Post‐fragmentation population structure in a cooperative breeding Afrotropical cloud forest bird: emergence of a source‐sink population network

Abstract

The impact of demographic parameters on the genetic population structure and viability of organisms is a long-standing issue in the study of fragmented populations. Demographic and genetic tools are now readily available to estimate census and effective population sizes and migration and gene flow rates with increasing precision. Here we analysed the demography and genetic population structure over a recent 15-year time span in five remnant populations of Cabanis's greenbul (Phyllastrephus cabanisi), a cooperative breeding bird in a severely fragmented cloud forest habitat. Contrary to our expectation, genetic admixture and effective population sizes slightly increased, rather than decreased between our two sampling periods. In spite of small effective population sizes in tiny forest remnants, none of the populations showed evidence of a recent population bottleneck. Approximate Bayesian modelling, however, suggested that differentiation of the populations coincided at least partially with an episode of habitat fragmentation. The ratio of meta-Ne to meta-Nc was relatively low for birds, which is expected for cooperative breeding species, while Ne /Nc ratios strongly varied among local populations. While the overall trend of increasing population sizes and genetic admixture may suggest that Cabanis's greenbuls increasingly cope with fragmentation, the time period over which these trends were documented is rather short relative to the average longevity of tropical species. Furthermore, the critically low Nc in the small forest remnants keep the species prone to demographic and environmental stochasticity, and it remains open if, and to what extent, its cooperative breeding behaviour helps to buffer such effects.

Spatiotemporal analysis of gene flow in Chesapeake Bay Diamondback Terrapins (Malaclemys terrapin)

“…; Husemann et al . ). Our results confirm the importance of taking historical factors into account when quantifying genetic connectivity in highly impacted landscapes.…”

“…; Husemann et al . ). In contrast to habitat fragmentation, the anthropogenic translocation of individuals between populations reduces genetic differentiation, increases diversity within populations and may obscure estimates of genetic connectivity (Templeton et al .…”

“…Disentangling how historical and contemporary processes affect current patterns of genetic diversity is a formidable challenge, but can be achieved by temporal sampling (Husemann et al . ), or by separately estimating contemporary and historical processes (Chiucchi & Gibbs ; Epps et al . ).…”

Evolution along the Great Rift Valley: phenotypic and genetic differentiation of East African white‐eyes (Aves, Zosteropidae)

“…2008; Husemann et al. 2014a, 2015a). Similarly, on continents geographic isolation and specific environmental conditions within certain habitat types can lead to island‐like conditions.…”

Crossing species boundaries : the hybrid histories of the true geese

“…Similar to IM models, Approximate Bayesian Computation (ABC) modelling (Beaumont, 2010)$/ has been used to estimate past effective population sizes and bottlenecks (Husemann et al, 2015, Spurgin et al, 2014b, Athrey et al, 2012, Allentoft et al, 2014, divergence times Joseph, 2012, Barber andKlicka, 2010) and the amount of gene flow (Illera et al, 2014). In contrast to IM models, however, ABC modelling allows for the comparison of multiple scenarios that differ in the amount and timing of gene flow.…”