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  e.g. McPeek and Brown (2000)  Local assembly of related species  e.g. Enquist et al. (2002)

Diversification and history of species pools Sample Literature 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. 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 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 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 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: Losos and Schluter (2000)—Area for speciation hypothesis Losos and Schluter (2000)—Area for speciation hypothesis Stephens and Weins (2003)—Time for speciation hypothesis Stephens and Weins (2003)—Time for speciation hypothesis Doebeli and Dieckmann (2000)—Speciation via ecological interactions Doebeli and Dieckmann (2000)—Speciation via ecological interactions Hubbell (2001)—Speciation proportional to abundance Hubbell (2001)—Speciation proportional to abundance

Local assembly of related species Sample Literature Elton (1946)—Compared genus to species ratios of local and regional faunas in Britain; attributed limited co-occurrence of congeners to competitive exclusion. 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. 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. 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 Webb (2000)—Introduced metrics for measuring relatedness of species in a sample relative to a species pool, in an explicitly phylogenetic context Similar to earlier methods of assessing phylogenetic uniqueness of sites for conservation planning, e.g. Vane-Wright et al. (1991), Faith (1992) 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” 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: Differing behavior and morphology of damselfly species in fish vs. dragonfly lakes Differing behavior and morphology of damselfly species in fish vs. dragonfly lakes Fish and dragonflies occur in different lakes and exert different predation pressures on Ennalagma Fish and dragonflies occur in different lakes and exert different predation pressures on Ennalagma Adaptations to dragonfly lakes (i.e., enhanced swimming ability) recently evolved with 2-3 independent origins Adaptations to dragonfly lakes (i.e., enhanced swimming ability) recently evolved with 2-3 independent origins Lower species richness of dragonfly lakes. Possible explanations: Lower species richness of dragonfly lakes. Possible explanations: Adaptations to dragonfly lakes evolved only recently and adapted lineages have not had time to diversify 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 Extinction is intrinsically higher in dragonfly lakes due to periodic drying Discontinuous patterns of speciation Discontinuous patterns of speciation Rapid, recent speciation within a lineage in Northeast likely the result of range expansion and development of reproductive isolation following glaciation 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 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) 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 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 High taxonomic exponents = high genus:species or family:species ratios High taxonomic exponents = high genus:species or family:species ratios Tested whether the relationship between species and higher taxa at a local scale differed from that at a regional scale Tested whether the relationship between species and higher taxa at a local scale differed from that at a regional scale Built regional species pools by merging plots within continents, hemispheres, and for the entire world 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 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 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: 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: Negative correlation between residual genus & family richness and precipitation Negative correlation between residual genus & family richness and precipitation Positive correlation between residual family richness and elevation 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) (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 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. 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.