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Link to original content: https://pubmed.ncbi.nlm.nih.gov/18611849/
Density-dependent diversification in North American wood warblers - PubMed Skip to main page content
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. 2008 Oct 22;275(1649):2363-71.
doi: 10.1098/rspb.2008.0630.

Density-dependent diversification in North American wood warblers

Daniel L Rabosky  1 , Irby J Lovette
Affiliations

Density-dependent diversification in North American wood warblers

Daniel L Rabosky et al. Proc Biol Sci. .

Abstract

Evidence from both molecular phylogenies and the fossil record suggests that rates of species diversification often decline through time during evolutionary radiations. One proposed explanation for this pattern is ecological opportunity, whereby an initial abundance of resources and lack of potential competitors facilitate rapid diversification. This model predicts density-dependent declines in diversification rates, but has not been formally tested in any species-level radiation. Here we develop a new conceptual framework that distinguishes density dependence from alternative processes that also produce temporally declining diversification, and we demonstrate this approach using a new phylogeny of North American Dendroica wood warblers. We show that explosive lineage accumulation early in the history of this avian radiation is best explained by a density-dependent diversification process. Our results suggest that the tempo of wood warbler diversification was mediated by ecological interactions among species and that lineage and ecological diversification in this group are coupled, as predicted under the ecological opportunity model.

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Figures

Figure 1
Figure 1
Maximum clade credibility (MCC) tree from Bayesian analysis of all continental North American Dendroica wood warbler species. Nodes marked with asterisks are supported by posterior probabilities of more than 0.95. Tree is based on more than 9 kb of mtDNA and nuclear intron sequence. Branch lengths are proportional to absolute time.
Figure 2
Figure 2
(a) Log-lineage through time (LTT) plot for North American wood warblers. Black line indicates LTT curve for the MCC tree (figure 1), and grey shading indicates 95% quantiles on the number of lineages at any point in time as inferred from the posterior distribution of phylogenetic trees sampled with MCMC. The dashed line indicates expected rate of lineage accumulation under constant-rate diversification with no extinction. Lineages accumulate quickly in the early phases of the radiation relative to the constant-rate diversification model. (b) Posterior distribution of the γ-statistic for wood warblers (black) in comparison with the corresponding null distributions, assuming either complete (f=1) or incomplete (f=0.25) sampling. Negative values of γ relative to the null distribution indicate decelerating diversification through time.
Figure 3
Figure 3
Maximum-likelihood reconstruction of speciation-through-time curve under overall best-fit model (density-dependent exponential). Rates are given in lineages per time unit assuming that the basal divergence occurred 1.0 time units before the present.
Figure 4
Figure 4
Distribution of ΔAICTS test statistic as tabulated from the posterior distribution of wood warbler phylogenies sampled using MCMC (black). Larger ΔAICTS values indicate better fit of density-dependent diversification models relative to continuous-decline models. Null distributions of ΔAICTS statistic (grey) were tabulated from phylogenies simulated under constant-rate and continuous-decline diversification models. Null distributions in (a) correspond to constant-rate phylogenies; distributions in (b,c) are phylogenies simulated under 5-fold and 10-fold declines in speciation under the continuous-decline model (equation (2.3)). We further tabulated null distributions under each model assuming taxon sampling was complete or incomplete at 75, 50 and 25% levels. Density-dependent models consistently fit the data better than the continuous-decline model, even when large numbers of missing taxa are assumed. The ΔAICTS statistic for the MCC tree is significant (p<0.05) under all diversification/sampling scenarios except the 10-fold decline with 25% sampling (p=0.085).
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