Pliocene forest dynamics as a primary driver of African bird speciation

Abstract

Aim Montane tropics are areas of high endemism, and mechanisms driving this endemism have been receiving increasing attention at a global scale. A general trend is that climatic factors do not explain the species richness of species with small to medium-sized geographic ranges, suggesting that geological and evolutionary processes must be considered. On the African continent, several hypotheses including both refugial and geographic uplift models have been advanced to explain avian speciation and diversity in the lowland forest and montane regions of central and eastern Africa; montane regions in particular are recognized as hotspots of vertebrate endemism. Here, we examine the possible role of these models in driving speciation in a clade of African forest robins. Location Africa.Methods We constructed the first robustly supported molecular phylogenetic hypothesis of forest robins. On this phylogeny, we reconstructed habitat-based distributions and geographic distributions relative to the Albertine Rift. We also estimated the timing of lineage divergences via a molecular clock. ResultsRobust estimates of phylogenetic relationships and clock-based divergences reject Miocene tectonic uplift and Pleistocene forest refugia as primary drivers of speciation in forest robins. Instead, our data suggest that most forest robin speciation took place in the Late Pliocene, from 3.2 to 2.2 Ma. Distributional patterns are complex, with the Albertine Rift region serving as a general east-west break across the group. Montane distributions are inferred to have evolved four times.Main conclusions Phylogenetic divergence dates coincide with a single period of lowland forest retraction in the late Pliocene, suggesting that most montane speciation resulted from the rapid isolation of populations in montane areas, rather than montane areas themselves being drivers of speciation. This conclusion provides additional evidence that Pliocene climate change was a major driver of speciation in broadly distributed African animal lineages. We further show that lowland forest robins are no older than their montane relatives, suggesting that lowland areas are not museums which house 'ancient' taxa; rather, for forest robins, montane areas should be viewed as living museums of a late Pliocene diversification event. A forest refugial pattern is operating in Africa, but it is not constrained to the Pleistocene.

Stable Pleistocene-era populations ofChaerephon pumilus(Chiroptera: Molossidae) in southeastern Africa do not use different echolocation calls

“…lineages were established during the late Pleistocene, between 60 000 and 13 000 years ago. Consistent with this, Taylor et al (2009) suggested that two lineages (Clade 1.1 and 2.1 in our analyses) underwent population expansion 12 956-3 360 y BP and 59 434-14 726 y BP, respectively, possibly associated with expansion from Pleistocene glacial refugia, a process shown to be influential in shaping patterns of genetic diversification among different taxa (Matthee & Robinson 1997;Hewitt 2000;Flagstad et al 2001;Muwanika et al 2003;Hewitt 2004;Anthony et al 2007;Brown et al 2007;Voelker et al 2010;Miller et al 2011).…”

Deep and wide valleys drive nested phylogeographic patterns across a montane bird community

“…Ten of the 23 species examined showed genetic divergences (see the phylogenetic trees in electronic supplementary material, S3, and summary table in electronic supplementary material, S2) that were spatially concordant with valleys, while a majority [13] showed no such effects across the distribution examined. While the distributions of four of these species extend to lower elevations, potentially enabling geneflow, the exceptions included the small, high-elevation rspb.royalsocietypublishing.org Proc.…”

“…Climatic fluctuations can change montane habitat distributions [10,11], enhancing the effects of biogeographic barriers [12]. Empirical evidence for the effects of climatic fluctuations comes from several montane regions where phylogenetic divergence correlates with the Pliocene in African forest robins [13] and in a Western Ghat sky island insectivore [14], Pleistocene in Australasian sky island species [15] and older Miocene events for South American Tanagers [16]. However, species may respond differentially to topography and climate.…”

Comparative multi-locus phylogeography confirms multiple vicariance events in co-distributed rainforest frogs

“…Though Pleistocene refugia are frequently depicted as drivers of species diversification, comparisons of molecular divergence among sister species indicate a continuum of divergence times from the Late Miocene to Recent, rather than a clear pulse of speciation events at the LGM [4][5][6][7][8]. Comparative studies of birds suggest that reproductively isolated sister taxa with overlapping distributions typically split during the Pliocene or Early Pleistocene and experienced recurrent cyclic changes whereas lineages that diverged during the Late Pleistocene more often show incomplete isolation or are non-overlapping geographically [4,[9][10][11][12]. Conversely, genetic or phenotypic divergence established during glacial periods may be reversed by intermittent (e.g.…”