McEntee, J. P. | Search bioRxiv

bioRxiv2018

The macroecology of passerine nest types, in the light of macroevolution

Passerine birds build a diversity of nests to lay and incubate eggs, and to house nestlings. Open cup, dome, and hole (or cavity) nests have distinct advantages and/or disadvantages related to predation risk and thermoregulation. We used macroecological and macroevolutionary approaches to test contrasting predictions from considering these consequences. Patterns of prevalence across latitude and elevation for the roofed nest types (holes and domes) provide no evidence that their thermoregulation benefits promote colonization of colder environments. These patterns are more consistent with the role of predation in determining where dome-nesting species in particular occur. Macroevolutionary analyses suggest that diversity patterns for nest types along major ecological gradients mostly arise from how clades with conserved nest types have diversified across gradients, rather than arising from local adaptation. Lastly, we reveal a negative relationship between body mass and latitude in hole-nesting passerines, which runs counter to Bergmanns rule.\n\nStatement of authorshipJPM and JGB designed the study. JPM and ZZ compiled data from the literature. JPM performed statistical analyses with input from JGB. JPM and JGB wrote the manuscript, and ZZ contributed to revisions.\n\nData accessibility statementsData were obtained from existing sources in the literature, cited in the manuscript.

evolutionary biology↗

bioRxiv2016

Tempo and timing of ecological trait divergence associated with transitions to coexistence in birds

Summary paragraphOrganismal traits may evolve either gradually or in rapid pulses followed by periods of stasis, but the relative importance of these evolutionary models in generating biodiversity has proven difficult to resolve1,2. In addition, while it is often assumed that pulses of trait evolution are associated with speciation events, few studies have explicitly examined how the tempo of trait divergence varies with respect to different geographical phases of speciation. Thus, we still know little about the trajectories of trait divergence over timescales relevant to speciation, or the extent to which these trajectories are shaped by variation in geographical isolation and overlap (sympatry) among incipient species. Here, we combine divergence time estimates, trait measurements, and geographic range data for avian sister species pairs worldwide to examine the tempo and timing of trait divergence during allopatric speciation. We show that divergence in two important ecological traits--?body mass and beak morphology--is best explained by a model including pulses of divergence and periods of relative stasis. We also infer that trait divergence pulses often precede sympatry, and that pulses leading to greater trait disparity are associated with earlier transitions to sympatry. These findings suggest that early pulses of trait divergence promote subsequent transitions to sympatry, rather than such pulses occurring after sympatry has been established, for example via character displacement3. Incorporating pulsed divergence models into allopatric speciation theory helps to resolve some apparently contradictory observations, including widespread instances of both rapid sympatry and prolonged geographical exclusion4-6.

evolutionary biology↗