Why abundant tropical tree species are phylogenetically old

Abstract

Neutral models of species diversity predict patterns of abundance for communities in which all individuals are ecologically equivalent. These models were originally developed for Panamanian trees and successfully reproduce observed distributions of abundance. Neutral models also make macroevolutionary predictions that have rarely been evaluated or tested. Here we show that neutral models predict a humped or flat relationship between species age and population size. In contrast, ages and abundances of tree species in the Panamanian Canal watershed are found to be positively correlated, which falsifies the models. Speciation rates vary among phylogenetic lineages and are partially heritable from mother to daughter species. Variable speciation rates in an otherwise neutral model lead to a demographic advantage for species with low speciation rate. This demographic advantage results in a positive correlation between species age and abundance, as found in the Panamanian tropical forest community.T he neutral theory of biodiversity (NTB) introduced the idea that geologic time scales may be directly relevant to ecological population dynamics (1). In NTB models, individuals produce offspring, disperse, and die at random, and species are ecologically equivalent because they share the same per capita birth and death probabilities. In most NTB models, new species arise by a process analogous to mutation; every new offspring has a (low) probability of mutating into the first member of a new species (1-4). In others, species randomly split into two new species with a probability proportional to population size (1, 5, 6). NTB models are remarkably successful in predicting distributions of species abundances, particularly with the assumption of mutation speciation (4,7,8). Although the assumption of ecological neutrality has been continuously challenged (9-13), the predictions of NTB have been shown to be robust to the existence of niches if species diversity is sufficiently high (2, 14, 15), because random drift can still occur between the relative abundances of species within the same niche or between species that share very similar niches (16,17).For realistically large number of individuals in a region, NTB models also predict that the abundances of species change slowly over geologic time before eventually drifting (randomly walking) to extinction (1,18,19). The taxon cycle that has occurred over intervals on the order of millions of years in several independent lineages of Lesser Antillean birds (20) provides some indirect empirical evidence for slow population dynamics over geologic time scales. However, recent studies also suggested that taxonomic turnover in very abundant clades, like birds (21, 22) and planktonic foraminifera (23), is sometimes much faster than that predicted by purely ecological drift.Here, we focus on geologic time scales and derive the predictions of NTB models for the relationship between a species' current abundance and its phylogenetic age: the time since the divergence of a species and its clo...

Backbones of evolutionary history test biodiversity theory for microbes

“…Another important empirical direction will be to extend this work across a broader range of taxa. For example, power law scaling of phylogenetic diversity with sample size for angiosperm communities (65) and nonneutrality in tropical forest phylogenies (66) suggest that the patterns we see here may not be restricted to microbes. Identifying the precise similarities and differences across taxonomic groups will undoubtedly lead to a range of insights and may also require more sophisticated analytical approaches given the relatively small size of many species-level phylogenies.…”

A mean field model for competition: from neutral ecology to the Red Queen

“…; Chisholm & Lichstein ; Condit et al ., ; Chave & Leigh ; Rosindell & Cornell , ; O'Dwyer & Green ; Vellend, ). Neutral theory has had considerably less success in predicting dynamic patterns of diversity, from decadal‐scale species abundance fluctuations to geological ages of species (Leigh, ; Wang et al ., ; Chisholm & O'Dwyer ). For example, in the case of rainforest trees, species ages predicted by neutral theory are sometimes older than the age of the Earth (Nee, ).…”

Benefits from living together? Clades whose species use similar habitats may persist as a result of eco‐evolutionary feedbacks

“…However, several other studies report the opposite relationship of species in speciose clades suffering higher extinction risk (Schwartz & Simberloff, 2001;Davies et al, 2011). In addition, Wang et al (2013) reported that rare, putatively vulnerable species belong to phylogenetically young clades. However, also, clade-level traits often explain only a limited portion of the variance in species rarity or decline (Wang et al, 2013) and may be inconsistent among families (Sj€ ostr€ om & Gross, 2006;Davies et al, 2011).…”

“…In addition, Wang et al (2013) reported that rare, putatively vulnerable species belong to phylogenetically young clades. However, also, clade-level traits often explain only a limited portion of the variance in species rarity or decline (Wang et al, 2013) and may be inconsistent among families (Sj€ ostr€ om & Gross, 2006;Davies et al, 2011).…”