Download Species richness: Taxonomic/phylogenetic perspectives

Species richness:
Taxonomic/phylogenetic perspectives
Species richness:
Taxonomic/phylogenetic perspectives
Phylogenetic information has been used in a variety of
fields of research: systematics, evolution, comparative
biology, biogeography, ecology
Webb et al. (2002) reviewed applications of phylogenies in
community ecology
Themes related to species richness:
 Diversification and history of species pools
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e.g. McPeek and Brown (2000)
Local assembly of related species
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e.g. Enquist et al. (2002)
Diversification and history of species pools
Sample Literature
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Ricklefs and Schluter (1993)—Included several chapters looking at historical
influences (e.g. coevolution, ecological radiation, range shifts) on species
assemblages as inferred through phylogenies.
Losos (1996)—Reviewed phylogenetic inferences including use of phylogenies to
determine which species of Anolis lizards on Antillean islands were derived from
colonization vs. in situ speciation
Ricklefs and Bermingham (2001)—Used phylogenies to infer timing of colonization of
bird species on Antillean islands, revealing that colonization and extinction were not
balanced over evolutionary time
Moritz et al. (2000)—Outlined an “integrated molecular approach” to the study of
diversification of rainforest faunas that had revealed variation in the age of species
and recent speciation centered on landscapes with spatial and temporal
heterogeneity
Diversification hypotheses and models:
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Losos and Schluter (2000)—Area for speciation hypothesis
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Stephens and Weins (2003)—Time for speciation hypothesis
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Doebeli and Dieckmann (2000)—Speciation via ecological interactions
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Hubbell (2001)—Speciation proportional to abundance
Local assembly of related species
Sample Literature
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Elton (1946)—Compared genus to species ratios of local and regional
faunas in Britain; attributed limited co-occurrence of congeners to
competitive exclusion.
Graves and Gotelli (1993)—Used null models to test for assembly rules in
Amazonian flocking birds; found that congeners flocked together less
frequently than expected by chance.
Tofts and Silvertown (2002)—Tested whether local segregation of
congeneric plants was due to competitive interactions or dispersal limitation,
by introducing the missing congener and monitoring performance; results
suggested role of dispersal limitation.
Webb (2000)—Introduced metrics for measuring relatedness of species in a
sample relative to a species pool, in an explicitly phylogenetic context
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Similar to earlier methods of assessing phylogenetic uniqueness of sites for
conservation planning, e.g. Vane-Wright et al. (1991), Faith (1992)
Palmer (in press)—Argues that “the number of species per genus or per
family is a biased measure of evolutionary ramification”
McPeek and Brown (2000)
Used phylogenies to interpret patterns of distribution, habitat use and morphology of
Ennalagma damselfly species, and to infer modes of speciation and diversification
Patterns addressed:
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Differing behavior and morphology of damselfly species in fish vs. dragonfly lakes
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Fish and dragonflies occur in different lakes and exert different predation pressures on
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Adaptations to dragonfly lakes (i.e., enhanced swimming ability) recently evolved with 2-3
independent origins
Lower species richness of dragonfly lakes. Possible explanations:
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Ennalagma
Adaptations to dragonfly lakes evolved only recently and adapted lineages have not had time
to diversify
Extinction is intrinsically higher in dragonfly lakes due to periodic drying
Discontinuous patterns of speciation
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Rapid, recent speciation within a lineage in Northeast likely the result of range expansion
and development of reproductive isolation following glaciation
More gradual speciation within another lineage in Southeast, with many species confined to
coastal plain, likely the result of classic allopatric speciation
Concluded that the many co-occurring species in fish lakes are ecologically very similar,
probably all sharing the same niche and structured by neutral processes rather than
niche differentiation.
Enquist et al. (2002)
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Using large datasets of rainforest plots and fossil assemblages, found that the relationships
between species and higher taxa (genera, families) at a local scale could be fitted to power
functions
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Tested whether the relationship between species and higher taxa at a local scale differed from
that at a regional scale
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Built regional species pools by merging plots within continents, hemispheres, and for the entire world
Species from pools were randomly reassigned to plots to generate random communities that were
replicated 1,000 times
Taxonomic exponents of random communities were significantly higher than observed communities
Suggested that these results could be explained by processes of dispersal limitation and local
filtering of species. Patterns of residual variation appeared to support this explanation further:
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High taxonomic exponents = high genus:species or family:species ratios
Negative correlation between residual genus & family richness and precipitation
Positive correlation between residual family richness and elevation
(No correlation of residual genus or family richness with stem density, maximum stem diameter, community
biomass or latitude)
Compared taxonomic exponents of different size classes and found lower taxonomic similarity
among larger classes, suggesting a role of competitive thinning among taxonomically similar
species as they mature
Found total biomass of plots to be related to richness (at all three taxonomic levels) by inverse
power functions, suggesting that biomass remains relatively constant, i.e. increases in richness
are accompanied by reduced biomass per taxon.