Abstract
Based on rangewide sampling and three mitochondrial and two nuclear markers (together up to 1,850 bp and 1,840 bp, respectively), we examine the phylogeography of two helmeted terrapin species (Pelomedusa galeata and P. subrufa sensu stricto) and infer shifts of climatically suitable spaces since the Last Glacial Maximum using a modeling approach. Whilst P. galeata displays significant phylogeographic structuring across its range and consists of two deeply divergent lineages that could represent distinct species, P. subrufa shows no obvious phylogeographic differentiation. This seems to be related to historically stable or fluctuating ranges. One of the lineages within P. galeata appears to be confined to the westernmost, winter-rainfall region of South Africa and deserves special conservational attention due to the scarcity of surface water. The other lineage is distributed further east and is differentiated in three weakly supported subclades with parapatric distribution; one occurring inland, and two along the south and east coasts, respectively. As far as is known, P. subrufa occurs in South Africa only in the northeast of the country (Limpopo, Mpumalanga) and we report the species for the first time from the Lapalala Wilderness Area in the Waterberg region (Limpopo), approximately 350 km further west than previously recorded. We confirmed the occurrence of P. galeata only 80 km south of Lapalala. Thus, a sympatric occurrence of P. galeata and P. subrufa is possible. Another putative contact zone, for the two lineages within P. galeata, must be located in the Western Cape region, and further contact zones are likely for the eastern subclades within P. galeata. The nuclear loci provided no evidence for gene flow across taxa or genetic clusters within taxa. Future investigations should use denser sampling from putative contact zones and more nuclear markers to re-examine this situation. Despite few phylogeographic studies published for southern African biota, it seems likely that differentiation follows general rules, and that climate and physiographic barriers (e.g., the Great Escarpment) have shaped phylogeographic patterns.
Highlights
Helmeted terrapins of the genus Pelomedusa are widely distributed across sub-Saharan Africa, the southwestern Arabian Peninsula and Madagascar
Localities for subclade Ia were from the interior of South Africa, at high elevations above the Great Escarpment, where summer-rainfall prevails (Fig. 2; records in the provinces of the Free State, Gauteng, Limpopo, North West, Northern Cape)
Nuclear markers confirm the distinctness of Pelomedusa galeata and P. subrufa sensu stricto
Summary
Helmeted terrapins of the genus Pelomedusa are widely distributed across sub-Saharan Africa, the southwestern Arabian Peninsula and Madagascar. How to cite this article Vamberger et al (2018), In quest of contact: phylogeography of helmeted terrapins (Pelomedusa galeata, P. subrufa sensu stricto). Pelomedusa was long assumed to be monotypic, with the single species P. subrufa (Bonnaterre, 1789) sensu lato. Pelomedusa contains 10 formally recognized species and a minimum of five unnamed candidate species (Vargas-Ramírez et al, 2010; Fritz et al, 2011; Fritz et al, 2014; Fritz et al, 2015; Vargas-Ramírez, Petzold & Fritz, 2016; Wong, Fong & Papenfuss, 2010; Petzold et al, 2014; Nagy et al, 2015)
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