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INTRODUCTION Palms and the Tropical Landscape Tropical forests are biodiversity hotspots and contain the most diverse plant communities on the planet (Givinish 1999). Neotropical rainforests are the most extensive of all global tropical forests; around half of the global total, 4 x 106 km2 in area, and one-sixth of the total broad-leaf forest of the world (Whitmore 1998). Tropical forest habitats can support a host of different tree species even in small areas; up to 283 species per hectare (Phillips et al. 1994). Palms are among the dominant vascular plants in many tropical forests, and are important components of the forest structure in Amazonian forests (Scariot 1999). Palms (Arecacea family) belong to the class of monocotyledons; they form a distinctive crown of feathery or fan-shaped leaves which are always alternate, often very large and pinnately incised to a varying degree (Bruggeman 1962). There number of palm species is estimated at 2500 – 3500 in approximately 210 – 236 genera (Jones 1995). Montufar & Pintaud (2006) have estimated the number of native palms in Western Amazonia to be about 121 species and 33 genera (roughly two-thirds of the Amazon palms and one-fifth of the New World palms). The richness and abundance of palm taxa, as well as their occurrence in all strata of the forest, and their importance as a vital food source for wildlife make this family a primary target for conservation (Scariot 1999). The sedentary habitat and patchy distributions of plants make them susceptible to habitat 1 destruction, which may cause changes in taxa composition and population sizes (Schemske et al. 1994). And despite the importance of plants, particularly palms, in the forest structure and function, their response to habitat fragmentation has been studied less than animals (Laurence & Bierregaard 1997). There are 165 individual species registered on the 2006 IUCN Red list, 9 of those are critically endangered, 14 individuals are endangered and 67 species are registered as vulnerable. Almost a third of the species on the list are data deficient (45 individuals), where there is inadequate information to make an assessment on the extinction risk of an individual species. Only one species, Amorphophallus preussii (endemic to Ecuador), has a recorded population trend; which is declining (Darbyshire 2004), all other individuals have not had their population trends studied. The major threat for all of the individuals is ongoing human induced habitat loss/degradation (ICUN 2006), whilst other major threats include large-scale wood plantations, livestock and crop agriculture, fires, infrastructure growth and in rare occasions; natural disasters such as volcano eruptions (Benavides & Pitman 2003). 2 Factors Influencing Species Abundance Land Use in Tropical Habitats Much of the Amazon Basin is a mosaic of forest types produced by erosion/deposition cycles of the major rivers (Clarke et al. 1995) and variation in terre firme parent material and geochemistry (Guillaumet 1987). Another source of small to medium scale spatial heterogeneity within tropical forests is the historical or current impact of human activity, from agriculture, silviculture and selective harvesting, even within stands considered to be old growth (Clark et al. 1995; Bush & Colinvaux 1994). Agriculture is the biggest land use of tropical forests and serves the main purpose for which rain forests are cleared (Whitmore 1998). Conversion of tropical rainforests to pasture for cattle husbandry is particularly widespread in the neotropics. Shifting agriculture, commonly known as ‘swidden’, is a sustainable low-input form of cultivation which can continue indefinitely on the infertile soils underlying most tropical rainforests, provided the carrying capacity of the land is not exceeded. Dufour (1990), claims that under some circumstances, shifting agriculture based on long fallow periods can be an ecologically and an economically sustainable practice in tropical forests. Not all shifting agriculture is practised in a sustainable manner, in some circumstances farmers fell and burn the forest and grow crops on the released nutrients for several years in succession, continuing until coppicing potential and the soil seed 3 bank are exhausted, invasive species take hold and soil nutrients are depleted. They then move onto a new patch of virgin forest. In western Amazonia, peasants from the Andean plateau are moving into the forest with no previous experience of forest agriculture, after growing a few crops they sell-out to a pastoralist who raises cattle, creating a wave of cultivation and poor pasture sweeping western from the foothills of the Andes (Whitmore 1998). On a more commercial scale, tropical forests are frequently used as a source of timber and non-timber products, and are an important and widespread forest land use in much of the tropics (Collins et al 1991). Clear felling results in greater levels of habitat loss and degradation, and it is believed that many palms do not regenerate in open areas and are therefore threatened in areas with extensive deforestation (Pedersen, 1994; Moraes et al., 1995), whereas selective logging; the periodical extraction of commercially valuable trees from forests (Johns 1988), has a much less detrimental effect on the forest ecosystem (Grieser Johns 1997; Asner et al 2004). The rate at which habitats are disturbed influences the species assemblages and diversity within a plant community. At very low rates of disturbance, such as infrequent clear-felling, competitive exclusion would occur and species richness would be low, species richness would be greatest at moderate levels of disturbance, because dominance is prevented, and the pool of potential colonists is relatively large (Armesto & Pickett 1985). 4 Habitat Associations The distribution of individuals within a population of plants is rarely random across a landscape (Harms et al. 2001). Tropical trees and shrubs often display distributional biases with respect to environmental variables such as soil type and water availability, across spatial scales of several ha to many km2. The association of species with physical habitat variables generates some of the most obvious patterns in the distribution and abundance of organisms, and its study has a long history (Cowles 1899; Whittaker 1956). On a smaller scale, microhabitat heterogeneity (referring to environmental conditions that vary at scales less than 10m2, e.g. treefall gaps or local topographic variations (Svenning 1999)), has been suggested to play an extensive role in determining species distributions (Grubb 1977; Ricklefs 1977). Whereas several authors (Molofsky & Augspurger 1992; Nicotra et al. 1999) have shown heterogeneity in environmental conditions that clearly influence seed and seedling survival, such as light, litter and soil moisture, have been shown to occur at spatial scales of less than 1m. Webb & Peart (2000) suggest that the most influential hypothesis for habitat partitioning in rain forest trees relies on not on any underlying heterogeneity in the physical environment, but on the endogenous, local heterogeneity created by canopy openings. A tropical landscape scattered with small indigenous communities practising traditional agricultural methods would create a mosaic of habitat types, and increasing heterogeneity on a landscape and microhabitat scale. 5 Only one group of tropical forest trees, the pioneer or early-successional species, has been clearly and consistently associated with a specific habitat type; disturbed areas such as large canopy openings (Whitmore 1989). Among nonpioneers species, little evidence has been compiled to link any differences in individual-level response to environmental conditions to differences in distribution along environmental gradients (Baraloto & Goldberg 2004). This shows a critical gap in current knowledge, as non-pioneer species form a large part of the tropical forest ecosystem, and in the case of many species such as palms, are fundamental keystone species, components for the present and future of the tropical forests globally. Consequently, it is important to identify any strong habitat associations resulting from human influenced habitat loss/degradation and their effects on the abundance and diversity of palms. Niche Width & Occupation Several authors (Grubb 1977; Denslow 1987) believe that the exceptional diversity within a tropical forest is maintained through niche differentiation with respect to resources. The niche is a multidimensional description of a species’ resource needs, habitat requirements and environmental tolerances (Hutchinson 1957). Where the niche structure of complex plant communities has been investigated in some detail, niche differences have been found in germination 6 behaviour, root depth, temperature thresholds, grazing tolerance, phenology and many other factors (Crawley 1997). The niche width of a species refers to the area which a species could physically inhabit; the niche width often differs from the area that a species actually inhabits, or its realized niche width. The niche concept has rarely been used in plant ecology due to the difficulty in defining a species’ niche breadth, in zoological terms it is fairly straightforward to define an individual’s niche in relation to diet and range size, yet it is much more difficult to apportion resources such as light, water or nitrogen between species. Within plant communities, a species with a ‘broad niche’ will be found growing abundantly over a wide range of niche conditions, and are known as generalists, and species with a ‘narrow niche’ , a specialist, will only be found under a restricted range of conditions. Specialist species with a narrow realized niche width will eventually become extinct from the landscape due to competition from more abundant species with a broader niche width. Crawley (1997) suggests that in order to maintain diversity, species-rich plant communities may be composed of: (i) species with narrower niches; (ii) species with more broadly overlapping niches; (iii) habitats providing ‘longer’ niche axes; or (iv) a combination of these. The ability for species to coexistence rather than out-compete in plant communities is driven by niche specialisation along gradients or resource availability (Grubb 1977; Crawley 1990). The niche diversification hypothesis created by Connell (1978) is an important equilibrium hypothesis stating that species coexist by occupying different niches. There are many authors that 7 discredit such as simple hypothesis, and a much more complex version proposes that coexistence is a result of habitat or microhabitat specialisation (Denslow 1987; Gentry 1988; Welden et al. 1991; Clark et al. 1993) and that much of the tropical plant diversity therefore depends on habitat and microhabitat heterogeneity. Aims & Objectives The aim of this study is to investigate possible species associations between palms and balsas across a range of habitat types, displaying different degrees of anthropogenic alteration and supporting a range of microhabitat variables. Specifically the questions addressed are (i) What is the palm density and abundance in the study area? (ii) Are there any habitat associations between palm species in natural and anthropogenically altered tropical forest? (iii) What are the species associations between balsa trees and palm species? The objectives derived from these aims are (i) Obtain the number of palms and balsas present in the study area and calculate species density and abundance through plot sampling. (ii) Identify differences in habitat type and land use and record microhabitat variables across the study site. (iii) Identify differences in species abundance and assemblages between natural and anthropogenically altered habitats. 8 METHODS Study Site The study took place during July and August 2007, conducted in the native community of La Torre, within the buffer zone of the Tambopata Nature Reserve, 27km southwest of Puerto Maldonado in south-eastern Peru (12°49’S, 69°17’W). The area is at the moist tropical/subtropical vegetation boundary (Brightsmith 2004). Rainfall is on average 2810 mm per year (Pearson & Derr 1986). The dry season starts in April and ends in October (Pearson & Derr 1986). The surrounding area is made up of a mix of floodplain and terra firme forests (Brightsmith 2004). There are no large-scale deforestation or agricultural areas in the La Torre community, although along the river edge and close to tourist and community residence there are small cleared sections for subsistence agriculture (less than 3 hectares) and homegardens (R. Harris, pers. Obs.). The dominant habitat is secondary floodplain forest, with fragments of understorey Guadua bamboo (Lloyd 2004) and remnants of primary forest. A seasonal palm swamp (12°42’S, 69°20’W), which has not been subjected to anthropogenic disturbances or land use change, located approximately 5km downstream of the La Torre community was also sampled. 9 Figure 1. Location of study site within South-eastern Peru. 10 Figure 2. Location of transects within study site. 1= 1250m, 2 = 1750m, 3 = 600m, 4 = 250m, 5 = 250m, 6 = 700m (Palm swamp), 7 = 1500m. Total length surveyed = 6.3km 11 Habitat Sampling A total of 136 survey plots were sampled laid out along transects following existing pathways, Figure 2 shows the location and length of the transects. A 100m2 plot was sampled every 50m along the transect, a pilot study using 25m intervals between plots was initially trailed but the method was deemed too timeconsuming for the limited study period. Plots were sampled at alternate sides of the transect to include more habitat types and ensure a more random sampling strategy. In total an area of 1.36ha was surveyed. Each plot was categorized at the time of the survey according to habitat type or past/present land use. The habitat categories were: Regenerated secondary forest with no visible anthropogenic alteration (SEC). Regrowth of secondary forest after large scale disturbances both natural and anthropogenic develops rapidly in tropical habitats, but species richness often accumulates quite slowly. Even regrowth over a century old does not contain all the species present in primary forest. (Corlett & Turner 1997). Garden, either abandoned or receiving lowest level of management such as occasional fruit harvesting (GARD). Home gardens usually contain small numbers of useful plant species grown such as trees for fruit and firewood, specialised vegetables and medicinal plants. Small populations of animals such as poultry and pigs are sometimes raised in homegardens (Kellman & Tackaberry 1997). 12 Residential (RES); either tourist residence or member of the La Torre Community, including the land immediately surrounding the buildings of a distance of less than 10m and not including land managed for agriculture purposes (managed land within the vicinity of residential property classed as home gardens). Agricultural land (AGRI); land recently (within last 20 years) >1ha used for the growth of crop species cleared completely of the original forest species present and may or may not of been subjected to burning. Agricultural land includes small-scale shifting agriculture and larger monoculture plantations. Dominant bamboo understorey within secondary forest (BAM). Bamboo grows in monotypic stands, which is unusual in tropical plant communities. The structure of bamboo stands differs from other habitats in that the relatively thin-stemmed plants are densely packed and have a thick subcanopy of similarly shaped leaves (Kratter 1997). Periodic palm swamp (SWA). Soils tend to be richer in plant nutrients due to seasonal flooding (Whitmore 1998). Yet flooded forests are usually less floristically diverse than non-flooded forests and contain more specialised species (Kellman & Tackaberry 1997). Habitat measurements were taken at each plot, the canopy openness was taken from the centre of the plot with an acetate sheet, the sheet had a 10cm x 10cm grid split into 100 cm squares, the number of squares which the sky was visible 13 through when held directly above at arms length, equalled the percentage of canopy openness. The five tallest trees within the survey plot were selected and their heights estimated by sight alone, the estimation of tree heights was based on previous knowledge of vegetation sampling in the same habitat, using an automatic range -finder and clinometer to record tree heights. The tree architecture of the five tallest trees was taken to give an indication of the recent history of the forest (Torquebiau 1986; Jones et al. 1995). The categories are: BA – ‘branching above’, if the first or major branch was above half of the tree height, indicative of tree growth under a closed canopy (undisturbed primary forest) or; BB – if it was ‘branching below’ half of the tree height, suggesting growth under an open canopy due to disturbance or treefall BASB – ‘branching above scars below’, where the first or major branch is above half height of the tree but there is evidence of dropped branches below half the tree height, caused by tree growth under a regenerating, closing canopy BBVG – ‘branching below vegetated growth’, the branches are growing vertically from close to its base, suggesting tree growth in a heavily altered habitat with frequent tree-cutting. 14 Palm and Balsa sampling Previous field work within the same study region and a pilot study revealed that Balsa (Ochroma pyramidale) was present along with five palm (Araceae) species. Ochroma pyramidale (Balsa) is harvested for its light timber which is produced when growth has been adequately rapid (Whitmore & Wooi-Khoon 1983). Ranges from southern Mexico to Bolivia and is found in the West Indies. Ochroma reaches heights of 20 – 30m and is an extremely fast grower; 5 -6 m per year (Whitmore 1998). Figure 3. Ochroma Pyramidale Socratea exorrhiza (Walking Palm) has wellseparated stilt roots (Fig. 2) which can grow up to 4m and are covered in small spines (Henderson et al 1995). Socratea exorrhiza can reach a height of 20m and is present from Nicaragua to Brazil (Chiquita 2006). Figure 4. The stilt roots of a Socratea exorrhiza palm. 15 Attalea butyracea (Shebon) can grow up to 30m tall (Wright & Duber 2001). The plant initially develops a basal rosette of fronds which may remain for 20years before trunk growth (Wright & Duber 2001). Attalea butyracea are found across Central America, Northern South America, Western South America (IPGRI 2007). Figure 5. Attalea butyracea Astrocaryum murumuru are shade – tolerant species (Losos 1995) and can grow up to 20m tall. Astrocaryum murumuru has black spines along the stem and leaf midrib (Fig. 3) and is distributed across western South America (IPGRI 2007). Figure 6. The underside and trunk of Astrocaryum murumuru 16 Euterpe edulis (Wasai Palm) can reach a height of 25m (Silva Matos & Watkinson 1998). Occurs in coastal forests on steep slopes and forest patches inland (Henderson et al 1995), typically on wetter soils, often in swampy areas (Dias et al 1988). Euterpe species are commonly harvested for their palm hearts (Silva Matos & Watkinson 1998); although Euterpe edulis within the study area are Figure 7. Euterpe edulis not being extracted. Distributed throughout Northern South America & Western South America (IPGRI 2007). Iriartea deltoidea (Erotic Palm) is the only species in the Iriartea genus. Clearly identified by clustered roots at the base of the stem, which can grow 1.5m above ground (Henderson et al. 1995). Characteristic canopy components of premontane tropical forests up to 1000m (Kessler 2000), individuals can reach 35m in height (Gentry 1993). Iriartea deltoidea have a wide Neotropical distribution across South America. Figure 8. Root structure of Iriartea deltoidea 17 The number of Ochroma pyramidale individuals with a diameter at breast height (d.b.h) ≥300mm were recorded, whereas with the palm species, the diameter of the palm was recorded at 500mm above ground level rather than the d.b.h, this would include the diameter of the root stilts in Iriartea and Socratea rather than the main stem, as the diameter of stilt roots can be used as an indicator to the age of an individual (A. Lee, pers. Comm.). The palm species were identified to species level and all palm and Ochroma species surveyed with a diameter ≥ 300mm had their heights recorded and whether the tree was fruiting, flowering or neither. 18 RESULTS Species Abundance There were 195 individuals recorded over all 7 transects at an overall abundance of 144 individuals per ha, 171 of those were palm species, 24 were Ochroma pyramidale. The most abundant species was Iriartea deltoidea, recorded at an abundance of 53 individuals per ha (Table 1 shows all abundances), the least abundant species was Socratea exorrhiza, recorded at 4.4 individuals per ha, Euterpe edulis also had a very low abundance, 6.6 individuals per ha. Transect 1 was the only transect to have all species present, whereas in transect 4 and 5, only one species was recorded, both these transects had the lowest abundance, 33.3 individuals per ha for both. Transect 6, located in the palm swamp, had the highest abundance of palms recorded, 214.3 per ha, but no Ochroma pyramidale individuals. No species was recorded on every transect, although Attalea butyracea occurred most frequently, on 6 out of the 7 transects, Socratea exorrhiza and Euterpe edulis occurred the least frequently, on only 3 out of the 7 transects. Table 2 shows the abundance of individuals based on habitat type at each plot. Secondary forest was the only habitat with all species present, agricultural habitats supported the lowest number of species, only Ochroma pyramidale and Attalea butyracea were present there. Agricultural habitats also had the lowest abundance, 20 individuals per ha, the highest abundance within a habitat was within the palm swamp, 214 individuals per ha. The palm swamp also had the 19 highest abundances of 3 palm species over all habitats; Iriartea deltoidea, Euterpe edulis & Socratea exorrhiza (129, 36 & 29 individuals per ha respectively). Garden habitats had the lowest abundance for palm species (119 individuals per ha), but the highest abundance for Ochroma pyramidale (81 individuals per ha). 20 Table 1. Abundance of individuals by transect. Key to habitats; SEC – secondary forest, GARD – garden, RES – residential including homegardens, AGRI – agricultural land, BAM – dominant bamboo understorey, SWA – seasonal palm swamp Transect 1 2 3 4 5 6 7 ALL 31 36 12 6 6 14 31 136 Area surveyed (Ha) 0.31 0.36 0.12 0.06 0.06 0.14 0.31 1.36 Dominant habitat type SEC SEC SEC SEC SEC SWA SEC Number of plots GARD / RES / AGRI / BAM Other habitats AGRI RES Abundance (individuals per Ha plus number recorded in parentheses) Ochroma pyramidale 9.7 (3) 50 (18) 16.7 (2) 0 0 0 3.2 (1) 17.6 (24) Astrocaryum murumuru 41.9 (13) 11.1(4) 25 (3) 33.3 (2) 0 0 16.1 (5) 19.6 (27) Iriartea deltoidea 74.2 (23) 22.2 (8) 0 0 0 128.6 (18) 74.2 (23) 52.9 (72) Attalea butyracea 48.4 (15) 16.7 (6) 33.3 (4) 0 33.3 (2) 21.4 (3) 9.7 (3) 24.3 (33) Euterpe edulis 6.5 (2) 0 16.7 (2) 0 0 35.7 (5) 0 6.6 (9) Socratea exorrhiza 3.2 (1) 0 0 0 0 28.6 (4) 3.2 (1) 4.4 (6) 183.9 (57) 100 (36) 91.7 (11) 33.3 (2) 33.3 (2) 214.3 (30) 106.5 (33) 125.7 (171) All palm species 21 Table 2. Abundance of individuals per ha in different habitats including number of individuals recorded in parentheses. Key to habitats; SEC – secondary forest, GARD – garden, RES – residential including homegardens, AGRI – agricultural land, BAM – dominant bamboo understorey, SWA – seasonal palm swamp. Number of plots Area surveyed (Ha) SEC 86 0.86 GARD 16 0.16 RES 6 0.06 AGRI 5 0.05 BAM 8 0.08 SWA 14 0.14 Abundance (individuals per ha plus number recorded in parentheses) Ochroma pyramidale Astrocaryum murumuru Iriartea deltoidea Attalea butyracea Euterpe edulis Socratea exorrhiza All palm species 5.8 (5) 26.7 (23) 52.3 (45) 27.9 (24) 3.4 (3) 2.3 (2) 81.2 (13) 12.5 (2) 0 6.2 (1) 0 0 50 (3) 16.6 (1) 16.6 (1) 0 0 0 20 (1) 0 0 20 (1) 0 0 25 (2) 12.5 (1) 62.5 (5) 12.5 (1) 0 0 0 0 128.5 (18) 21 (3) 35.7 (5) 28.5 (4) 112.7 (97) 18.7 (3) 33.3 (2) 20 (1) 87.5 (7) 214.2 (30) A non-parametric test was carried out to investigate differences in species abundances between habitats. Ochroma pyramidale & Iriartea deltoidea were significant to the P <0.01 level (df = 5, H = 21.59 & 21.34 respectively), and Euterpe edulis & Socratea exorrhiza were significant to the P < 0.05 level (df = 5, H = 11.42 & 14.19 respectively). A post-hoc test, Dunn’s multiple comparison test showed that for all species except Iriartea deltoidea, there was no significant difference between habitat type and species abundance. For Iriartea deltoidea, Dunn’s multiple comparison test showed that the mean rank of the garden habitat is lower than the mean rank of the swamp habitat, and that all other habitats did not differ significantly from each other (P < 0.05, nGARD = 16, nSWA = 14). 22 Habitat Sampling In the initial pilot study there were seven habitat types identified, secondary forest, garden, residential, agricultural, bamboo understorey, palm swamp and slash and burn; there was only one plot located within a slash and burn habitat, and for all analyses this plot has been omitted from the data. Secondary regenerated forest was the most dominant habitat type, while agricultural land was the rarest (Table 3). The highest average canopy height and lowest canopy openness was recorded in the palm swamp, and the lowest canopy height and greatest canopy openness recorded in agricultural land. The palm swamp showed higher numbers of trees with a ‘Branching Above’ architecture, typical of undisturbed forests, the garden and agricultural habitats had the highest numbers of trees with ‘Branching Below Vegetated Growth’ architecture, associated with frequent and extreme disturbance. Table 3. Number of plots within each habitat type and their mean micro-habitat variables with standard deviations in parentheses; tree architecture as a mean % of plot, average canopy height and % of canopy openness. Key to habitats; SEC – secondary forest, GARD – garden, RES – residential including homegardens, AGRI – agricultural land, BAM – dominant bamboo understorey, SWA – seasonal palm swamp. Number of plots SEC GARD RES AGRI BAM SWA 86 16 6 5 8 14 Mean Canopy Height (m) BBVG Canopy openness (%) Tree Architecture (mean % of plot) BA BB BASB 11.75 (3.26) 12.4 (17) 42 (27.4) 40.2 (28.2) 2.8 (6.8) 4.13 (7.03) 8.99 (1.63) 0 67.6 (30.8) 17.4 (21.6) 8.8 (16.2) 5.13 (4.42) 10.26 (2.57) 3.4 (8.2) 20 (29.4) 56.6 (29.4) 3.4 (20) 16 (33.8) 6.65 (0.44) 4 (8.8) 48 (43.8) 4 (8.8) 8 (10.8) 61 (53.43) 10.7 (0.74) 0 40 (21.2) 52.6 (30) 5 (9.2) 2.25 (1.28) 12.32 (0.81) 30 (15.2) 27.2 (23) 42.8 (23.2) 0 1.79 (1.57) 23 The heights for each species within the plots were also recorded and a mean height was calculated for each habitat type (Table 4). A one-way ANOVA was then used to test for significance within the means. Euterpe edulis and Socratea exorrhiza were excluded due to low occurrence rates within a large proportion of the different habitat types. The highest averages were for Ochroma pyramidale and Iriartea deltoidea. Ochroma pyramidale was recorded at a greater mean height within residential habitats, and lower average heights within agricultural land, the average heights recorded for Ochroma pyramidale were the only significant results. Table 4. Mean (± standard deviation) average heights of selected species within different habitat types including significance. Key to habitats; SEC – secondary forest, GARD – garden, RES – residential including homegardens, AGRI – agricultural land, BAM – dominant bamboo understorey, SWA – seasonal palm swamp. GARD RES AGRI BAM 7 0 11.5 0.7 F = 7.956 P < 0.05 9 0 F = 1.056 P > 0.05 Ochroma pyramidale Mean Std. Dev. 12.2 1.64 10 1.58 14.67 1.52 Astrocaryum murumuru Mean Std. Dev. 8.3 4.01 11.5 0.7 3 0 Attalea butyracea Mean Std. Dev. 7.07 3.85 8 0 Iriartea deltoidea Mean 11.1 Std. Dev. 3.11 7 0 4 1.73 F = 0.494 P > 0.05 16 12.2 11.83 F= 1.092 0 2.16 3.33 P > 0.05 6 0 24 SWA Significance SEC Habitat and Species Associations The influence of micro-habitat variables across all habitat types on the presence or absence of all species is shown in Table 5. Only 2 species showed significant associations with any micro-habitat variable. Iriartea deltoidea was the only species to show significance associations with all variables. The openness of canopy had a negative effect (P <0.05) on the presence of Iriartea deltoidea, the greater the canopy openness, the lower the incidence rate of species presence within a plot (mean canopy openness when species present = 9.02 ±21.7; mean canopy cover when species absent = 3.02 ±5.14). The mean average canopy height had a positive effect on Iriartea deltoidea, the greater the average canopy height, the greater the chance of species presence (mean average canopy height when species present = 12.7 ±2.8; mean average canopy height when species absence = 10.8 ±4.7). The tree architecture had influence the presence of two species, Iriartea deltoidea and Attalea butyracea. Attalea butyracea was positively correlated with habitats with a tree architecture consisting of ‘Branching Above’, Iriartea deltoidea was positively correlated with habitats containing trees with ‘Branching Above’ and ‘Branching Above Scars Below’ architecture. There were higher rates of Iriartea deltoidea absent in a plot when the tree architecture was described as ‘Branching Below’ or ‘Branching Below Vegetated Growth’. None of the other species showed any significant correlation to micro-habitat variables. 25 Table 5. Influence of micro-habitat variables on species presence or absence across all habitat types including significance. (NS = no significance) Tree architecture Canopy openness % BA BB BASB BBVG Average canopy height Ochroma pyramidale NS NS NS NS NS NS Astrocaryum murumuru NS NS NS NS NS NS Iriartea deltoidea Negative P<0.05 Positive P<0.01 Negative P<0.01 Positive P<0.01 Negative P<0.01 Positive P<0.01 Attalea butyracea NS Positive P<0.05 NS NS NS NS Euterpe edulis NS NS NS NS NS NS Socratea exorrhiza NS NS NS NS NS NS Table 6. Association between species across all habitat types based on Chisquared test: + +percentage of occasions when both species were present, + percentage of occasions when only one of the two species were present, including P value. Attalea butyracea Ochroma pyramidale Attalea butyracea Astrocaryum murumuru Iriatea deltoidea Euterpe edulis Socratea exorrhiza + + 0.7% + + 1.4% + + 0% + + 0% + + 0% + - 27.9% P > 0.05 + - 23.52% P > 0.05 + - 40.4% P < 0.05 + - 14.7% P > 0.05 + - 13.9% P > 0.05 + + 5.1% + - 25% P > 0.05 + + 5.7% + - 34.5% P > 0.05 + + 5.1% + - 36.02 P > 0.05 + + 2.9% + - 17.6% P < 0.05 + + 0% + - 20.5% P > 0.05 + + 2.9% + - 28.6% P > 0.05 + + 0% + - 22.7% P > 0.05 + + 1.4% + - 16.9% P > 0.05 + + 2.2% + - 29.4% P > 0.05 Astrocaryum murumuru Iriartea deltoidea + + 0% + - 8.1% P > 0.05 Euterpe edulis 26 There were only two significant correlations between species (Table 6), Ochroma pyramidale and Iriartea deltoidea not once occurred in the same plot (X2 = 6.74, P < 0.05), and Euterpe edulis and Attalea butyracea only occurred in the same plot on 2.9% of the time (X2 = 9.17, P <0.05). There were 5 other occasions of negative correlation, Euterpe edulis & Ochroma pyramidale, Socratea exorrhiza & Ochroma pyramidale, Socratea exorrhiza & Attalea butyracea, Astrocaryum murumuru & Euterpe edulis, Socratea exorrhiza & Euterpe edulis. None of the species have strong positive correlations with other species, Euterpe edulis has the most negative correlations with 4, and Astrocaryum murumuru and Iriartea deltoidea have the least negative correlations, 1 each. The proportion of plots where one species was absent and another present was greatest with Ochroma pyramidale and Iriartea deltoidea, 40.4%, and lowest between Euterpe edulis and Socratea exorrhiza. 27 DISCUSSION Microhabitat Heterogeneity The microhabitat variables recorded in this study reflect only a small proportion of potential parameters of which can directly affect species distributions on a spatial and temporal scale. Microhabitat variables not recorded in this study that may influence species distributions within communities include topography/elevation (Vazquez & Givinish 1998; Keating 1999), soil type (Newbery et al. 1986; Sabatier et al. 1997) and climate conditions (Overpeck et al. 1990; Bongers et al. 1999). The selection of variables recorded was chosen to reflect the land use and possible influences of anthropogenic alterations or disturbances. Most of the results were consistent with the expected outcomes of varying degrees of disturbance, the palm swamp, which has not been subjected to major anthropogenic disturbances, displayed the most pristine habitat, with the greatest mean canopy height and the lowest percentage of canopy openness, on the other end of the scale; agricultural land which has been subjected to the most severe forms of disturbance within the area suffered from the lowest canopy height and the greatest percentage of canopy openness. The main inconsistencies in microhabitat variables in accordance to land use and expected forest structure was the tree architecture. Recording the tree 28 architecture of a plot is said to give an indication of the recent history of the forest (Torquebiau 1986; Jones et al. 1995), the majority of the habitat types had predictable tree architecture, such as secondary forest, which mainly consisted of trees grown under an open canopy due to disturbance or treefall. The palm swamp however, did not have tree architecture corresponding to the previous habitat variables recorded or to the known history of the site. The plots surveyed were mainly composed of trees signifying growth under a regenerating closing canopy, not the type of tree structure found within an undisturbed primary forest. So based on these results it would appear that compared to the other habitats used in this study, the palm swamp represents a more preserved habitat, although it cannot be classed as primary or pristine forest, and like most of the forest in the La Torre region, it is a secondary old growth forest. Regardless of this, the habitats chosen for this study show microhabitat variations according to land use and disturbance, and therefore are adequate sites for basing species and habitat associations on. 29 Species Abundance Iriartea deltoidea was the most abundant species recorded across the whole of the study area, and the dominant species in 4 out of 7 transects. Although it was the most common species within the La Torre region of south eastern Peru; a study by Montufar & Pintaud (2006), investigating the distribution of palm communities across western Amazonia found that Iriartea deltoidea was the most abundant aborescent palm species on terra firme within Ecuador, but in north-east Peru it becomes patchily distributed or rare over large areas. Iriartea deltoidea has a wide range across the neotropical forests of South America, but the distribution of individuals across landscapes on a countrywide scale is obviously not even, but could be dependent on randomness or more likely; relying on the macro and micro scale environmental heterogeneity discussed in previous and subsequent sections. The most frequently occurring species was Attalea butyracea, which was found in 6 out of 7 transects and in 5 out of the 6 habitats. Attalea butyracea has proven in this study to be the best species in dispersal and recruitment. The stony endocarps of Attalea butyracea can persist on the forest floor for several years before decomposing and are distributed by several species including primates, rodents and small mammals (Harms & Dalling 1995). The mean heights of individuals were less than that of other species, suggesting that although dispersal mechanisms for Attalea butyracea are more effective than in 30 other palm species, individuals are easily out competed by existing and pioneer species, resulting in numerous stunted individuals. Species Abundance by Habitat Type Secondary forest had the greatest number of palms present, whereas the palm swamp had the greatest density of palms; the palm swamp supported the largest communities of Iriartea deltoidea, Euterpe edulis and Socratea exorrhiza, although Euterpe edulis and Socratea exorrhiza had the lowest occurrence rates within all the transects. Euterpe edulis typically occurs on wetter soils (Dias et al. 1988) due to the fact that germination is higher on such soils (Silva Matos & Watkinson 1998), and can probably explain why the largest number of Euterpe edulis individuals was found in the palm swamp. In opposition of this explanation, Clark et al. (1995), found that Euterpe edulis was closely associated with steep topography and less fertile soils, contradicting their high abundance within the palm swamp, which tends to be rich in nutrients due to seasonal flooding (Whitmore 1998). Rather than suggesting Euterpe edulis is more successful in the palm swamp than other habitats, the low abundance within habitats outside of the palm swamp could be a result of past over-extraction of palm hearts, which results in death of the individual tree. Although there is no current harvesting of palm hearts in the La Torre region studied, past harvesting may have depleted the seed bank, meaning any further regeneration of Euterpe edulis communities 31 will require seed dispersal from habitats such as the palm swamp or by management prescriptions such as seedling transplants. The palm swamp was the only habitat in which Ochroma pyramidale was absent from, Pearson et al. (2003) suggests that Ochroma pyramidale has a high demand for nutrients, and larger gaps are required for release from root competition, the palm swamp had the lowest canopy openness and the highest density of palms, resulting in unfavourable conditions for Ochroma pyramidale to thrive, the garden habitat had the highest density of Ochroma pyramidale, which had the lowest number of palms and a high percentage of canopy openness. The pioneer or early-successional species (such as Ochroma pyramidale), has been clearly and consistently associated with a specific habitat type; disturbed areas such as large canopy openings by Whitmore (1998), and follows the same trend here, with the largest communities present in the most disturbed habitats. Dransfield (1978) suggests that stilt roots in palms favour the exploitation of canopy gaps similar to pioneer species; the development of the root cone early in the life cycle permits a rapid height increase without loss of stability (Swaine 1983). Socratea exorrhiza and Iriartea deltoidea are both stilt root palms, yet neither of these species was found in abundance in any of the disturbed habitats, Socratea exorrhiza was only found within the palm swamp and secondary forest habitats, suggesting that these two stilt root species do not favour canopy gaps, and could not be described as pioneers. There are clear differences in palm species assemblages in the range of habitats sampled here, the density of palm species also varies between habitats. 32 The habitats that have been subjected to anthropogenic disturbances supported fewer species and fewer individuals than the more pristine habitats. The seedling stage and mechanisms driving dispersal and germination are the most affected by disturbances attributed to anthropogenic influences, both positively and negatively. Wright & Duber 2001 found that anthropogenic disturbance indirectly reduced seed dispersal and seed predation; this concentrated seeds near reproductive trees and enhanced seed survival. As a consequence, seedling recruitment increased with the intensity of anthropogenic disturbance, with disproportionate increases near seed-bearing trees, and a reduced dispersal of new recruits to other habitats. This would result in concentrations of species within disturbed habitats, which was not apparent within the habitats sampled in this study. In a study of Amazonian palms, Scariot (1999) established that the seedling stage was most affected by habitat disturbances and fragmentation, and that this possible lower seedling recruitment may lead to taxa composition in small forest fragments diverging from continuous forest, which is what has occurred within the La Torre region, with each habitat having a unique assemblage of palm species that are derived from the list of species found within the secondary forest habitat. 33 Microhabitat and Species Associations There have been many authors that have studied a range of microhabitat variables such as topography, soils, climate and canopy height, and found significant relationships between the distributions of individuals across landscapes according to the mosaic of microhabitats (Webb & Peart 2000; Phillips et al. 2003; Svenning 1999), whereas other studies have found little evidence for microhabitat partitioning among non-pioneer tree species (Welden et al. 1991; Clark & Clark 1992; Clark et al. 1993). In this study there were only two species to show significant microhabitat associations: Iriartea deltoidea and Attalea butyracea. Iriartea deltoidea displayed significant associations with all variables; a higher mean canopy height and lower mean canopy openness had a positive effect on the species presence, tree architecture reflecting regenerating closed canopies and undisturbed forest also had a positive effect on species presence, whereas tree architecture indicating a frequently disturbed forest structure had a significant negative effect on species presence. Regarding canopy height; Welden et al. (1991) found that canopy height was unimportant for the two palm species included in their study whereas a study by Svenning (1999) showed that canopy height influenced the distribution of some palm species, but was of much less importance than topography. The only other species to show significant associations with microhabitat variables was Attalea butyracea, which was positively associated with tree architecture indicative of undisturbed primary forest. These results suggest that Iriartea 34 deltoidea are significantly associated with forest structures containing tall, closed canopies and have limited anthropogenic disturbance or alteration. Due to the fact that Attalea butyracea was the most frequently occurring species across all habitat types, it is difficult to say with conviction that Attalea butyracea is associated with a particular forest structure. It has been discussed previously that Attalea butyracea has the best dispersal mechanisms seen in this study, and is therefore able to establish communities in most habitats. Consequently, the microhabitat association seen here merely suggests that Attalea butyracea has a preference to undisturbed primary forests, and that although it is able to colonise and exploit canopy gaps and openings through dispersal and recruitment, it is a non-pioneer species, with a habitat preference for undisturbed forests. A study by Svenning (1999) investigating microhabitat specialisation in Ecuadorian palm communities found that 20 out of 31 taxa analysed had significant microhabitat relationships, and that most of the palm species were distributed according to the microhabitat variables at scales of tens to hundreds of metres. Wider research into tropical tree communities, including palm species, has also found examples of microhabitat specialisation; Webb & Peart (2000) discovered that there were significant associations of species with variation in physiography, within an area that is limited in spatial and elevational range, although, all habitat associated species occurred at least once in a non-preferred habitat. A study by Phillips et al. (2003) found that a large fraction of tree species have a significant tendency to be favoured by one habitat or another, and that the proportion of species with significant habitat associations with their study 35 approaches 80%. There have been studies in the neotropical tree communities that have found no microhabitat associations, particularly amongst non-pioneer species; Clark & Clark (1992) found that four of six non-pioneer species at La Selva, Costa Rica did not differ in sapling distributions with respect to canopy structure, and a study by Baraloto & Goldberg (2004) found that among nonpioneer species few indications of differences in the microhabitat conditions permitting seedling bank establishment. The difference between pioneer and non-pioneer species in respect to habitat and niche partitioning has been noted by several authors before (Grubb 1986; Pacala & Rees 1998; Rees et al. 2001), the biggest single influential environmental factor driving niche occupation is light availability; variation in light within the forest provides colonisation-based niches. There was no strong evidence within the results to suggest that any of the species were specialists and restricted by niche width, although there were clear habitat preferences towards the palm swamp (Euterpe edulis, Socratea exorrhiza, Iriartea deltoidea). Tilman & Pacala (1993) suggest that habitat association alone does not provide strong support for the hypothesis of niche differentiation as a mechanism for maintaining species diversity. Vormisto (2002; 2004) suggests that palms tend to be widespread and habitat generalists, and that palm communities are more influenced by dispersal across broader spatial scales than by environment heterogeneity. However, in this study; in which only a small selection of palms were identified and sampled, there was one species for which 36 a clear association with all microhabitat variables recorded has been identified, with one other species showing a significant association with one variable. Ochroma pyramidale had the most negative associations with other species. Ochroma pyramidale is a pioneer species, which typically exploit canopy gaps and areas of recent disturbance. Ochroma pyramidale are very fast growing (Whitmore & Wooi-Khoon 1983), and are able to out-compete palm seedlings within newly created canopy openings, therefore when Ochroma pyramidale are present within a plot, it is unlikely there will be established communities of palm species. Based on the strong microhabitat associations shown by Iriartea deltoidea with undisturbed forests with a closed canopy, it is perhaps unsurprising that Ochroma pyramidale was never found within the same plot. Ochroma pyramidale is a pioneer species; its habitat preferences are recently disturbed habitats and canopy gaps, which were negatively associated with Iriartea deltoidea. Although there is no evidence in the results to directly link microhabitat associations to species associations; Iriartea deltoidea and Attalea butyracea both had the same significant positive association with primary forest tree architecture, but there were no significant positive or negative species associations. Harms et al. (2001) found that in a study investigation habitat associations in a neotropical forest; their results did not support the hypothesis that habitat specialisation is among the principal mechanisms of species coexistence and associations, which apparently maintains a large fraction of the diversity within a tropical plant community. A study in the tropical forest of Costa Rica by Clark et al. (1995) 37 found that Socratea exorrhiza and Iriartea deltoidea had a low probability of interspecific encounter, and that possible forms of interaction between the two are cited as competition for pollinators or indirect effects mediated by specific mycorrhizal fungi or natural enemies; but there were no significant negative associations between the two species in the La Torre region, the two species coexisted in both habitats in which Socratea exorrhiza was present, and were found to have their highest abundances in the same habitat, the palm swamp; displaying a higher probability of interspecific encounter than Clark et al. (1995) stated. Again, Iriartea deltoidea had a different abundance characteristic in the La Torre region compared to another part of South America where its range extends to. Previously we discussed how Iriartea deltoidea was more common in La Torre than in North Peru, and now it is apparent that Iriartea deltoidea is able to coexist with other palm species within the region that it would normally be negatively associated with. 38 Conclusions The first biogeographical hypothesis regarding palm distributions in Amazonia may be attributed to de Candolle (1857); he suggested that Amazonian palms were ‘almost equally diffused throughout the tropics’. Extensive research into the tropics and particularly palm communities has disproved this hypothesis. Amazonia is a highly heterogeneous region, in which climate, soils, landscape, dispersal and geological history can only partially explain the distribution patterns of palms (Montufar & Pintaud 2006). Even in a small area, such as the La Torre region sampled in this study, there are differences in palm species abundance and assemblages based on the varying levels of anthropogenic alteration and the high microhabitat heterogeneity present. The palm swamp is clearly a important patch habitat within the matrix of secondary forest and anthropogenically altered habitats, it is therefore crucial that this habitat is conserved to prevent the onset of succession and encroachment of invasive pioneer species seen in other parts of the La Torre region. The palm swamp supports the highest density and diversity of palm species, and crucially, supports the largest community of Iriartea deltoidea, which in this study has been identified as the most important species. It is highly abundant in the La Torre region, whereas in north-east Peru it becomes patchily distributed or rare over large areas, it was the only species to show significant habitat preferences and microhabitat associations, and coexists with Socratea exorrhiza when other studies have found there to be negative species associations between the two species. in the La Torre region the primary 39 target for conservation within the palm community would be Iriartea deltoidea, and the habitats and species it is closely associated with, due to its patchy abundance across Peru, and its unpredictable distribution characteristics within La Torre. The family of palms have been described as keystone species, crucial to the forest structure and ecosystem, this study highlights the sensitivity of palm communities to relatively low impact anthropogenic disturbances over a small area. Based on this, it would be fair to assume that high impact anthropogenic disturbances such intensive agriculture, commercial timber extraction and urbanisation could potentially result in the breakdown of palm communities, facilitate the extinction of specialist species from a region, and encourage the recruitment of invasive and pioneer species. 40 REFERENCES Armesto, J.J. & Pickett, S.T.A, (1985) Experiments on disturbance in old-field plant communities: impact on species richness and abundance. Ecology. 66. 230 – 240. Asner, G.P., Keller, M., Silvas, J.N.M. (2004) Spatial and temporal dynamics of forest canopy gaps following selective logging in the eastern Amazon. Global Change Biology. 10. 765 – 783. Baraloto, C. & Goldberg, D.E., (2004) Microhabitat associations and seedling bank dynamics in a tropical forest. Oecologia. 141. 701 – 712. Benavides, G. & Pitman, N. (2003). Anthurium ecuadorense. In: IUCN 2006. 2006 IUCN Red List of Threatened Species. www.iucnredlist.org.Accessed 7th March 2007. Bongers, F., Poorter, L., Van Rompaey, R.S.A.R., Parren, M.P.E., (1999) Distribution of twelve moist forest canopy tree species in Liberia and Cote d’Ivoire: response curves to a climatic gradient. Journal of Vegetation Science. 10. 371 – 382. Brightsmith, D.J., (2004) Avian Geophagy and soil characteristics in South-eastern Peru. Biotropica, 36, 534 – 543. Bruggeman, L., (1962) Tropical Plants and their Cultivation. Thames and Hudson. London. 228pp. Bush, M.B. & Colinvaux, P.A., (1994) Tropical forest disturbance: paleoecological records from Darien, Panama. Ecology. 75. 1761 – 1768. de Candolle, A. (1857) Sketch on the life and writings of M. de Martius, secretary to the Bavarian Academy of Science. Hookers Journal of Botany and Kew Garden Miscellaneous. 9. 6 – 10. Chiquita (2006) Nature and Community Project. http://www.chiquita.com/naturecommunity/FloraAndFauna/Slides/Flora/Slide %2005.asp. Accessed 22nd February 2007. 41 Clark, D.A. & Clark D.B., (1999) Assessing the growth of tropical rain forest trees: issues for forest modelling and management. Ecological Applications. 9. 981 – 997. Clark, D.B., Clark, D.A., Rich, P.M., (1993) Comparative analysis of microhabitat utilization by saplings of nine tree species in neotropical rain forest. Biotropica. 25. 397 – 407. Clark, D.A., Clark, D.B., Sandoval, Rosa Sandoval, M., Marco Vinicio Castro, C., (1995) Edaphic and Human Effects on Landscape-Scale Distributions of Tropical Rain Forest Palms. Ecology. 76. 2581 – 2594. Collins, N.M., Sayer, J.A., Whitmore, T.C. (1991). The Conservation Atlas of Tropical Forests: Asia and the Pacific. Macmillan. London. Connell, J., (1978) Diversity in tropical rainforests and coral reefs. Science. 199. 1302 – 1310. Corlett, R.T. & Turner, I.M., (1997) Long-Term Survival in Tropical Forest Remnants in Singapore and Hong Kong. In: Laurence, W.F. & Bierregaard, R.O. Jr. (eds.) Tropical Forest Remnants: Ecology, Management, and Conservation of Fragmented Communities. University of Chicago Press, Chicago. Pages 333 – 347. Cowles, H.C., (1899) The ecological relations of the vegetation on the sand dunes of Lake Michigan. Botanical Gazette. 27. 95 – 391. Crawley, M.J., (1990) The population dynamics of plants. Philosophical transactions of the Royal Society of London. 330. 125 – 140. Crawley, M.J., (1997) Plant Ecology Second Edition. Blackwell Science. Oxford. 717 pp. Darbyshire, I. (2004). Amorphophallus preussii. In: IUCN 2006. 2006 IUCN Red List of Threatened Species. www.iucnredlist.org. Accessed 7th March 2007. Denslow, J.S., (1987) Tropical rainforest gaps and tree species diversity. Annual Review of Ecology and Systematics. 18. 431 – 451. Dias, A.C., Figliolia, M.B., Netto, B.V.M., Nogueira, J.C.B., Silva, A.D., Siqueira, A.C.M.F., Yamazoe, G., (1988) Pesquisa sobre palmito no Instituto 42 Florestal de São Paulo. In Oliveira, Y.M., Machado, N.A., Carpanezzi, A.A. (Eds.) Encontro Nacional de Pesquisadores em Palmito. Curitiba, Brazil. pp 63 – 73. Dransfield, J., (1978) Growth forms of rain forest palms. In: Tomlinson, P.B. & Zimmermann, M.H., (eds). Tropical trees as living systems. Cambridge University Press. New York. Pp 247 – 268. Dufour, D.L. (1990) Use of Tropical Rainforests by Native Amazonians. Bioscience. 40. 652 – 659. Gentry, A.H., (1988) Changes in plant community diversity and floristic composition on environmental and geographical gradients. Annals of the Missouri Botanical Garden. 75. 1 – 34. Gentry, A. H., (1993) A field guide to the Families and Genera of woody plants of Northwest South America. Conservation International. Washington DC. Givinish, T.J., (1999) On the causes of gradients in tropical tree diversity. Journal of Ecology. 87. 193 – 210. Grieser Johns, A. (1997) Timber Production and Biodiversity Conservation in Tropical Rain Forests. Cambridge University Press. Cambridge. Pp 22 – 187. Grubb, P.J., (1977) The maintenance of species-richness in plant communities: the importance of the regeneration niche. Biology Reviews. 52. 107 – 145. Grubb, P.J., (1986) Problems posed by sparse and patchily distributed species in species-rich plant communities. In: Diamond, J & Case, T.J (eds.) Community Ecology. Harper & Row. New York. Pp 207 – 225. Guillaumet, J.L., (1987) Some structural and floristic aspects of the forest. Experientia. 43. 241 – 251. Harms, K.E., Condit, R., Hubbell, S.P., Foster, R.B., (2001) Habitat associations of trees and shrubs in a 50-ha neotropical forest plot. Journal of Ecology. 89. 947 – 959. Henderson, A., Galenano, G., Bernal, R., (1995) Field guide to the palms of the Americas. Princeton University Press. New York. 43 Hutchinson, G.E., (1957) Concluding remarks. Cold Spring Harbor Symposium on Quantitative Biology. 22. 415 – 457. IPGRI; International Plant Genetic Resources Institute (2007) New world fruits database. http://www.ipgri.cgiar.org/regions/americas/programmes/TropicalFruits/defa ult.asp. Accessed 22nd February 2007. IUCN. (2006) IUCN Red List of Threatened Species. www.iucnredlist.org. Accessed 7th March 2007. Johns, A.D. (1988) Effects of “selective” timber extraction on rainforest structure and composition and composition and some consequences for frugivores and folivores. Biotropica. 20. 31 – 37. Jones, D.L., (1995) Palms throughout the world. Smithsonian Institution Press. Washington. Jones, M.J., Linsley, M.D., Marsden, S.J., (1995) Population sizes, status and habitat associations of the restricted-range bird species of Sumba, Indonesia. Bird Conservation International. 5. 21 – 52. Keating, P.L. (1999) Changes in paramo vegetation along an elevation gradient in Southern Ecuador. Journal of TORREY BOT SOC? 126. 159 – 175. Kellman, M. & Tackaberry, R., (1997) Tropical Environments. The functioning and management of tropical ecosystems. Routledge. London. 380pp. Kessler, M., (2000) Upslope-directed mass effect in palms along an Andean elevational gradient: A cause for high diversity at mid-elevations? Biotropica. 32. 756 – 759. Kratter, A.W., (1997) Bamboo Specialization by Amazonian Birds. Biotropica. 29. 100 – 110. Laurence, W.F. & Bierregaard, R.O. Jr. (1997) Tropical Forest Remnants: Ecology, Management, and Conservation of Fragmented Communities. University of Chicago Press, Chicago. 616pp. Lloyd, H., (2004) Habitat and population estimates of some threatened lowland forest bird species in Tambopata, south-east Peru. Bird Conservation International. 14. 261 – 277. 44 Losos, E., (1995) Habitat Specificity of Two Palm Species: Experimental Transplantation in Amazonian Successional Forests. Ecology. 76. 2595 – 2606. Molofsky, J. & Auspurger, C.K., (1992) The effect of leaf litter on early seedling establishment in a tropical forest. Ecology. 73. 68 – 77. Montufar, R., & Pintaud, J.C., (2006) Variation in species composition, abundance and microhabitat preferences among western Amazonian terra firme palm communities. Botanical Journal of the Linnean Society. 151, 127 – 140. Moraes, M., Galeano, G., Bernal, R., Balslev, H. and Henderson, A. (1995) Tropical Andean palms (Arecaceae). In Biodiversity and Conservation of Neotropical Montane Forests (S.P. Churchill, H. Balslev, E. Forero and J.L. Luteyn, eds) pp. 473 - 87. New York: The New York Botanical Garden. Newberry, D.M., Gartlan, J.S., McKey, D.B., Waterman, P.G., (1986) The influence of drainage and soil phosphorous on the vegetation of Doula-Edea Forest Reserve, Cameroon. Vegetation. 65. 149 – 162. Nicotra, A.B., Chazdon, R.L., Iriart, S.V.B., (1999) Spatial heterogeneity of light and woody seedling regeneration in tropical wet forests. Ecology. 80. 1908 – 1926. Overpeck, J.T., Rind, D., Goldberg, R., (1990) Climate-induced changes in forest disturbance and vegetation. Nature. 343. 51 – 53. Pacala, S.W. & Rees, M. (1998) Models suggesting field experiments to test two hypotheses explaining successional diversity. American Naturalist. 152. 729 – 737. Pearson, L., & Derr, J.A. (1986) Seasonal patterns of lowland forest floor arthropod abundance in south-eastern Peru. Biotropica 18. 244 - 256. Pearson, T.R.H., Burslem, D.F.R.P., Goeriz, R.E., Dalling, J.W., (2003) Regeneration niche partitioning in neotropical pioneers: effects of gap size, seasonal drought and herbivory on growth and survival. Oecologia. 137. 456 – 465. 45 Pedersen, H.B. (1994) Management, extraction and commercial use of wild palms in Ecuador. In Las plantas y el hombre (M. RõÂ os and H.B. Pedersen, eds) pp. 12 - 22. Quito, Ecuador: ABYA-YALA. Phillips, O.L., Hall, P., Gentry, A.H., Sayer, S.A., Vasquez, R., (1994) Dynamics and species richness of tropical rain forests. Proceedings of the National Academy of Sciences, USA. 91. 5 – 2809. Phillips, O.L., Vargas, P.N., Monteagudo, A.L., Cruz, A.P., Zans, M.C., Sanchez, W.G., Yli-Halla, M., Rose, S., (2003) Habitat association among Amazonian tree species: a landscape-scale approach. Journal of Ecology. 91. 757 – 775. Rees, M., Condit, R., Crawley, M., Pacala, S., Tilman, D., (2001) Long-term studies of vegetation dynamics. Science. 293. 650 – 655. Ricklefs, R.E., (1977) Environmental heterogeneity and plant species diversity: a hypothesis. The American Naturalist. 111. 377 – 381. Silva Matos, D.M. & Watkinson, A.R., (1998) The Fecundity, Seed, and Seedling Ecology of the Edible Palm Euterpe edulis in Southeastern Brazil. Biotropica. 30. 595 – 603. Scariot, A. (1999) Forest fragmentation effects on palm diversity in central Amazonia. Journal of Ecology, 87, 66 – 76. Schemske, D.W., Husband, B.C., Ruckelshaus, M.H., Goodwillie Parker, C.I.M., Bishop, J.G. (1994) Evaluating approaches to the conservation of rare and endangered plants. Ecology, 75, 584 – 606. Svenning, J.C., (1999) Microhabitat specialization in a species-rich palm community in Amazonian Ecuador. Journal of Ecology. 87. 55 – 65. Swaine, M.D., (1983) Stilt roots and ephemeral germination sites. Biotropica. 15. 240 – 245. Tilman, D & Pacala, S.W. (1993) The maintenance of species richness in plant communities. In: Ricklefs, R.E. & Schulter, D. (eds) Species Diversity in Ecological Communities: Historical and Geographical University of Chicago Press. Chicago. Pp 13 – 25. 46 Perspectives. Torquebiau, E.F., (1986) Mosaic patterns in Dipterocarp rain forest in Indonesia and their implications for practical forestry. Journal of Tropical Ecology. 2. 301 – 325. Vazquez, J.A. & Givinish, T.J., (1998) Altitudinal gradients in tropical forest composition, structure and diversity in the Sierra de Manantlan. Journal of Ecology. 86. 999 – 1020. Vormisto, J. (2002) Palms as rainforest resources: how evenly are they distributed in Peruvian Amazonia? Biodiversity and Conservation. 11. 1025 – 1045. Vormisto, J., Svenning, J.C., Hall, P., Balslev, H., (2004) Diversity and dominance in palm (Arecaceae) communities in terre firme forests in the western Amazon basin. Journal of Ecology. 92. 577 – 588. Webb , C.O. & Peart, D.R., (2000) Habitat associations of trees and seedlings in a Bornean rain forest. Journal of Ecology. 88. 464 – 478. Welden, C.W., Hewett, S.W., Hubbell, S.P., Foster, R.B., (1991) Sapling survival, growth, and recruitment: relationship to canopy height in a neotropical forest. Ecology. 72. 35 – 50. Whitmore, T.C. & Wooi-Khoon, G., (1983) Growth analysis of the seedlings of balsa, Ochroma lagopus. New Phytol. 95. 305 – 311. Whitmore, T.C., (1989) Canopy gaps and the two major groups of forest trees. Ecology. 70. 536 – 538. Whitmore, T.C., (1998) An Introduction to Tropical Rain Forests. Second edition. Oxford University Press. Oxford. 282pp. Whittaker, R.H., (1956) Vegetation of the Great Smoky Mountains. Ecological Monographs. 26. 1 – 80. Wright, S.J. & Duber, H.C., (2001) Poachers and Forest Fragmentation Alter Seed Dispersal, Seed Survival, and Seedling Recruitment in the Palm Attalea butyracea, with Implications for Tropical Tree Diversity. Biotropica. 33. 583 – 595. 47