Population genetics of the olive‐winged bulbul (Pycnonotus plumosus) in a tropical urban‐fragmented landscape

Abstract

With increasing urbanization, urban‐fragmented landscapes are becoming more and more prevalent worldwide. Such fragmentation may lead to small, isolated populations that face great threats from genetic factors that affect even avian species with high dispersal propensities. Yet few studies have investigated the population genetics of species living within urban‐fragmented landscapes in the Old World tropics, in spite of the high levels of deforestation and fragmentation within this region. We investigated the evolutionary history and population genetics of the olive‐winged bulbul (Pycnonotus plumosus) in Singapore, a highly urbanized island which retains <5% of its original forest cover in fragments. Combining our own collected and sequenced samples with those from the literature, we conducted phylogenetic and population genetic analyses. We revealed high genetic diversity, evidence for population expansion, and potential presence of pronounced gene flow across the population in Singapore. This suggests increased chances of long‐term persistence for the olive‐winged bulbul and the ecosystem services it provides within this landscape.

Demographic history of the fragmented yellowthroated bulbul (Pycnonotus xantholaemus) population in the Deccan Peninsula, India

“…It had high hd and low π. Similar results have been reported for other bulbul species: olive-winged bulbul Pycnonotus plumosus (Tang et al 2016), light-vented bulbul P. sinensis (Song et al 2013), collared finchbill Spizixos semitorques (Gao et al 2011) and Philippines bulbul Hypsipetes philippinus (Silva-Iturriza et al 2010). High hd and low π reflect that the population has undergone rapid expansion from a small ancestral population, with a small effective population size (N e ) (Rogers & Harpending 1992).…”

“…The time since expansion was estimated for YTB using the 1050 bp sequence of mtCR with a mutation rate of 1.6 to 2.8% per base pair per million years (Lerner et al 2011). Since life history parameters were not available for this species, we used a generation time of 1 yr based on the estimates for the olivewinged bulbul Pycnonotus plumosus (Tang et al 2016) and the Philippines bulbul Hypsipetes philippinus (Kennedy et al 2000).…”

Significance of the globally threatened Straw-headed Bulbul Pycnonotus zeylanicus populations in Singapore: a last straw for the species?

“…This can be complemented with genetic studies to investigate the degree of gene flow between the subpopulations across Singapore (e.g. Tang et al 2016). Findings drawn from both field survey and genetic data can be incorporated into an endangered species management plan coordinated among various stakeholders as a follow-up.…”

Gene flow and genetic drift in urban environments

“…For example, we found that urban fragmentation can result in increased genetic drift and reduced gene flow for many organisms including both small (Gortat et al, ) and large mammals (Wilson, Farley, McDonough, Talbot, & Barboza, ), lizards (Delaney et al, ), amphibians (Hitchings & Beebee, ), fish (Mather, Hancox, & Riginos, ), insects (Keller, Nentwig, & Largiader, ) and plants (Hollingsworth & Dickson, ). Urban facilitation, however, resulted in reduced drift and increased gene flow in a variety of organisms including insects (Kamdem, Fouet, Gamez, & White, ; Vickruck & Richards, ), birds (Tang et al, ), mammals (Adams, van Heezik, Dickinson, & Robertson, ) and plants (Johnson, Prashad, Lavoignat, & Saini, ). Indeed, a wide variety of taxa also experienced no change in genetic drift and gene flow, including organisms as diverse as plants (Culley, Sbita, & Wick, ) and mammals (Atterby, Allnutt, MacNicoll, Jones, & Smith, ).…”

“…In contrast, isolation‐by‐resistance (IBR, McRae, ) models predict that in addition to geographic distance, other factors (e.g., roads and buildings) provide varying levels of resistance to gene flow, many of which act in nonlinear and nonadditive ways. Urban features may act as either complete barriers or conduits to gene flow, or may act somewhere along the continuum from barrier to conduit (Crispo et al, ; de Groot et al, ; Holderegger & Di Giulio, ; LaPoint, Balkenhol, Hale, Sadler, & van der Ree, ; Tang, Sadanandan, & Rheindt, ). Although there is great heterogeneity of anthropogenic landscape features found within and between cities, it is unclear the extent to which urban fragmentation and facilitation models have been applied to landscape genetic analyses.…”