Pseudocongruent phylogeography reflects unique responses to environmental perturbations in a biodiversity hotspot

Abstract

Aim: Comparative phylogeographic studies provide important insights into the biogeographic processes shaping regional patterns of diversity. Yet, comparative studies are lacking for southern African herpetofauna, despite their high diversity. We statistically compare phylogeographic structure and divergence-time estimates among five co-distributed forest-living herpetofaunal taxa to assess rivers, climatic refugia and climatic gradients as congruent drivers of phylogeographic diversity.Location: Maputoland-Pondoland-Albany biodiversity hotspot, Southern Africa. Taxon: herpetofauna (reptiles and amphibians).Methods: Phylogeographic structure and divergence-times within species were estimated from mitochondrial and nuclear DNA sequence data. Phylogeographic concordance factors were used to estimate the degree of phylogeographic congruence among sympatric localities. Full-likelihood Bayesian comparisons were used to estimate synchronous divergence between phylogeographic regions and across a putative river barrier. Palaeoclimatic niche models were compared among taxa to identify congruent climatic refugia. Nonparametric statistics were used to identify climatic differences between regions and among populations within each species. Finally, redundancy analyses were used to assess geographic distance, climate and the putative river barrier as explanatory variables to genetic diversity. Results: There is comprehensive phylogeographic structuring within each species, comprising distinct northerly and southerly clades. Phylogeographic concordance factors generally support co-diversification in a north/south axis. Yet, analyses of the divergence-time estimates through the Mio/Plio/Pleistocene indicate asynchronous phylogeographic histories. Climatic niche models identified idiosyncratic responses to palaeoclimatic change. Climatic variables are significantly different among populations in all species and correlated with latitude. A combined model of distance, climate and rivers explained the greatest proportion of genetical diversity in most taxa, of which climate explained the highest variance. Main Conclusions: Ancient and recent species-specific responses to climatic and geological processes resulted in pseudo congruent phylogeographic histories among the five co-distributed species. The presence of a congruent north/south pattern in multiple taxonomic groups occupying different forested microhabitats, from fossorial to arboreal, supports latitudinal gradients as global drivers of phylogeographic diversity along the east coast of South Africa.

Phylogeny and phylogeography of chelonians from sub-Saharan Africa—A review of current knowledge in tribute to Margaretha D. Hofmeyr

“…Consequently, old lineages will diverge even more, while previously undifferentiated widely distributed taxa will only start to diverge from their conspecifics in other refugia. Thus, it is not unexpected that a recent analysis of phylogeographic congruence for herpetofauna from South Africa demonstrated that broad spatial congruence of co-distributed taxa is actually uncorrelated (Busschau et al 2022). We therefore encourage phylogeographic investigators to exercise caution in providing wholesale interpretations regarding congruency of patterns and to give careful attention to timing of diversification events and examine alternatives, and to propose hypotheses that are falsifiable.…”

Refining species boundaries among velvet worms (Onychophora, Peripatopsidae), with the description of two new species of Opisthopatus from South Africa

“…Aridification increased and the contraction of the forest biome persisted during the Pliocene to Pleistocene, further promoting cladogenesis among the velvet worm fauna of South Africa. In addition, the Miocene, Pliocene, and Pleistocene epochs represent periods of major cladogenesis in several other South African faunal groups (e.g., Barnes et al, 2020;Busschau et al, 2019Busschau et al, , 2021Busschau et al, , 2022Tolley et al, 2011Tolley et al, , 2014.…”

“…A revision of the O. kwazululandi s. l. species complex is outside of the scope of the present study but will be initiated in future. In addition, a recent comparative phylogeographic study by Busschau et al (2022) (Garrick et al, 2004). We are now focusing on poorly sampled regions in an attempt to identify sympatric velvet worm species and assess their reproductive isolation using additional DNA sequence data.…”

“…Although the forested region of Baziya is a reserve, there seems to be very little direct protection offered to these taxa or to any other potential narrow endemic invertebrate species present in these forests. Furthermore, the Baziya forest complex appears to have been highly neglected during biodiversity surveys; it also harbors a new, recently described freshwater crab, as well as a genetically isolated population of the Natal Black snake (Busschau et al, 2022;Daniels et al, 2021). Thus, the detection of diversity is key for the development and prioritization of adequate management plans and future active protection and, specifically for Baziya, the establishment of a more effective conservation regime.…”

Comparative biogeography of North American turtle faunas: Neogene regionalization

“…Once our cladistic biogeographic analysis was completed, we employed the comprehensive phylogeny of Thomson et al (2021) to assess whether biogeographical patterns were synchronous or established episodically, over time (Morrone 2020). This was necessary because a shared pattern does not prove synchronicity (Donoghue and Moore 2003, Naka and Brumfield 2018, Busschau et al 2022. That is, the same biogeographical pattern can be repeated through time (e.g., Keck andNear 2010, Blanton et al 2013).…”