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Transcript
Ecology Chapter 09 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 1 Outline • • • • Distribution Limits Distribution Patterns Organism Size and Population Density Commonness and Rarity 2 3 Introduction • Ecologists usually define a population as a group of individuals of a single species inhabiting a specific area. (族群) Characterized by the number of individuals and their density. Additional characteristics of a population include age distributions, growth rates, distribution, and abundance. (分佈) (數量) 4 5 Distribution Limits (分佈限制) • Physical environment limits geographic distribution of a species. Organisms can only compensate so much for environmental variation. 6 Kangaroo Distributions and Climate • Caughley found a close relationship between climate and distribution of the three largest kangaroos in Australia. Macropus giganteus - Eastern Grey Eastern 1/3 of continent. Macropus fuliginosus - Western Grey Southern and western regions. Macropus rufus - Red Arid / semiarid interior. 7 Kangaroo Distributions and Climate 8 Kangaroo Distributions and Climate • Limited distributions may not be directly determined by climate. Climate often influences species distributions via: Food production Water supply Habitat Incidence of parasites, pathogens and competitors. 9 Tiger Beetle of Cold Climates • Tiger Beetle (Cicindela longilabris) (長唇虎甲 蟲) lives at higher latitudes and elevations than most other species in NA. Schultz et. al. found metabolic rates of C. longilabris are higher and preferred temperatures lower than most other species. Supports generalization (概說) that the physical environment limits species distributions. 10 Tiger Beetle of Cold Climates 11 Figure 09_04 12 • Ecologists suggest that during the last glacial period C. longilabris lived far south of its present range limits. Then with climatic warming and the retreat of the glaciers, the tiger beetles followed their preferred climate northward and up in elevation into the mountains of western North America. 13 Distributions of Plants along a MoistureTemperature Gradient • Encelia species distributions correspond to variations in temperature and precipitation. pubesent 扁果菊 加州扁果菊 縟扁果菊 銀色扁果菊 nonpubesent 木扁果菊 14 有軟毛的 15 pubesent nonpubesent 16 Distributions of Barnacles along an Intertidal Exposure Gradient • Organisms living in an intertidal zone have evolved to different degrees of resistance to drying. Barnacles show distinctive patterns of zonation within intertidal zone. Connell found Chthamalus stellatus (小 藤壺) restricted to upper levels while Balanus balanoides (巨藤壺) is limited to middle and lower levels. 17 Distributions of Barnacles along an Intertidal Gradient • Balanus appears to be more vulnerable to desiccation, excluding it from the upper intertidal zone. Chthamalus adults appear to be excluded from lower areas by competition with Balanus. 18 Distributions of Barnacles along an Intertidal Gradient 19 20 Distribution of Individuals on Small Scales • • • Random: Equal chance of being anywhere. Uniform distribution of resources. (隨機) Regular: Uniformly spaced. (均勻) Exclusive use of areas. Individuals avoid one another. Clumped: Unequal chance of being anywhere. Mutual (相互的) attraction between individuals. Patchy (不勻稱) resource distribution. (叢集) 21 Distribution of Individuals on Small Scales 敵對的 22 Distribution of Tropical Bee Colonies • Hubbell and Johnson predicted aggressive bee colonies would show regular distributions while non-aggressive species would show random or clumped distributions. As predicted, four species with regular distributions were highly aggressive. Fifth was non-aggressive and randomly distributed. Prospective nest sites marked with pheromones. (費洛蒙) 23 有背無刺蜂 黃腹無刺蜂 競爭者 24 Distributions of Desert Shrubs • Traditional theory suggests desert shrubs are regularly spaced due to competition. Phillips and MacMahon found distribution of desert shrubs changes from clumped to regular patterns as they grow. Young shrubs clumped for (3) reasons: Seeds germinate at safe sites Seeds not dispersed from parent areas Asexual reproduction 25 Distributions of Desert Shrubs • • Phillips and MacMahon proposed as plants grow, some individuals in clumps die, reducing clumping. Competition among remaining plants produces higher mortality. Eventually creates regular distributions. Brisson and Reynolds found competitive interactions with neighboring shrubs appear to influence distribution of creosote roots, Larrea tridentata. 26 Creosote bush 三齒拉瑞阿 27 28 Heterogeneity in Rangelands 29 • The root systems of creosote bushes overlap much less than they would if they had circular distributions. • Brisson and Reynolds conclude that creosote bushes compete for belowground resources. 30 Distributions of Individuals on Large Scales • Bird Populations Across North America Root found at continental scale, bird populations showed clumped distributions in Christmas Bird Counts. Clumped patterns occur in species with widespread distributions. Brown found a relatively small proportion of study sites yielded most of records for each bird species in Breeding Bird Survey (繁殖鳥類調查). 31 短嘴鴨 32 魚鴨 33 人口普查 綠鵑 34 Plant Abundance along Moisture Gradients • Whittaker examined distributions of woody plants along moisture gradients in several North American mountain ranges. Documented moisture gradient from moist canyon bottoms up to the dry southwestfacing slopes. Tree species showed a highly clumped distribution along moisture gradients, with densities decreasing substantially toward the edges of their distribution. 35 Organism Size and Population Density • In other words, like birds, tree populations are concentrated in hot spots. 36 石松 亞歷桑那野草苺 西部黃杉 37 針刺松 紅槭 加拿大鐵杉 38 Organism Size and Population Density • In general, population density declines with increasing organism size. Damuth found the population density of herbivorous mammals (草食性哺乳類) decreased with increased body size. Peters and Wassenberg found aquatic invertebrates tend to have higher population densities than terrestrial invertebrates of similar size. Mammals tend to have higher population densities than birds of similar size. 39 40 Organism Size and Population Density 41 Plant Size and Population Density • Plant population density decreases with increasing plant size. Underlying details are very different. Tree seedlings can live at very high densities, but as the trees grow, density declines progressively until mature trees are at low densities. 42 紫萍 無性生殖多年生的 北美紅杉 43 44 45 Duckweed 46 Commonness and Rarity (普遍 & 稀有) • Rabinowitz devised commonness classification based on combinations of three factors: Geographic Range of Species (extensive versus restricted) Habitat Tolerance (broad versus small)- is related to the range of conditions in which a species can live Local Population Size (large versus narrow) 47 Commonness and Rarity (普遍 & 稀有) • • • Some plant species can tolerate a broad range of soil texture, pH, and organic matter content, while other plant species are confined to a single soil type. Tiger have broad habitat tolerance. Snow leopard is confines to a narrow range of conditions in the high mountains of the Tibetan Plateau. 48 Commonness and Rarity (普遍 & 稀有) • • Small geographic range, narrow habitat tolerance, and low population density are attributes of rarity. Populations that are least threatened by extinction, have extensive geographic ranges, broad habitat tolerances, and some large local populations. All seven other combinations create some kind of rarity. 49 Rarity • Rarity I Extensive Range, Broad Habitat Tolerance, Small Local Populations Peregrine Falcon (遊隼) 50 Peregrine Falcon 51 Rarity • Rarity II Extensive Range, Large Populations, Narrow Habitat Tolerance Passenger Pigeon 52 Passenger Pigeon 53 Rarity • Extreme Rarity III Restricted Range, Narrow Habitat Tolerance, Small Populations California Condor (兀鷹) 54 California Condor 55 放射松 加拉巴哥中型地雀 弗里芒氏楊 線葉鐵角蕨 夏威夷菊 魚鴨 袋獾 千歲蘭 短葉紅豆杉 卜力查得棕樹 56 Welwitschia 57 Pritchardia monroi 58