Browsing by Author "Vamberger, Melita"

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    How many species of angulate tortoises occur in Southern Africa? (Testudines: Testudinidae: Chersina)
    (Wiley-Blackwell, 2020) Hofmeyr, Margaretha D.; Spitzweg, Cäcilia; Vamberger, Melita
    Using range-wide sampling and 1,143 bp of mtDNA (cytochrome b gene) and 14 microsatellite loci, we examined genetic differentiation in the widely distributed Southern African angulate tortoise (Chersina angulata). We found evidence for two genealogical lineages that differ in both genetic marker systems and their preferred habitat conditions. According to a fossil-calibrated molecular clock for all African tortoise lineages using 1,870 bp mitochondrial and 1,416 bp nuclear DNA, the two lineages of C. angulata diverged in the Pliocene (approx. 3.8 million years ago). Species distribution models reveal that the ranges of the two lineages shifted little since the Last Glacial Maximum, which is in agreement with the demographic population descriptors suggestive of stationary populations that did not experience expansion. One lineage occurs in the west, and the other in the south of the extant distribution range. In the geographic contact zone, the two lineages hybridize extensively, providing evidence for their conspecificity under the biological species concept. Each lineage could be recognized as a distinct subspecies, but the ill-defined geographic origins of the type material of the available names prevent their identification with any taxon.
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    In quest of contact: phylogeography of helmeted terrapins (Pelomedusa galeata, P. subrufa sensu stricto)
    (PeerJ, 2018) Vamberger, Melita; Hofmeyr, Margaretha D.; Ihlow, Flora; Fritz, Uwe
    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.
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    Leopard tortoises in southern Africa have greater genetic diversity in the north than in the south (Testudinidae)
    (Wiley, 2018) Spitzweg, Cäcilia; Hofmeyr, Margaretha D.; Fritz, Uwe; Vamberger, Melita
    In contrast to mammals, little is known about the phylogeographic structuring of widely distributed African reptile species. With the present study, we contribute data for the leopard tortoise (Stigmochelys pardalis). It ranges from the Horn of Africa southward to South Africa and westwards to southern Angola. However, its natural occurrence is disputed for some southern regions. To clarify the situation, we used mtDNA sequences and 14 microsatellite loci from 204 individuals mainly from southern Africa. Our results retrieved five mitochondrial clades; one in the south and two in the north-west and north-east of southern Africa, respectively, plus two distributed further north. Using microsatellites, the southern clade matched with a well-defined southern nuclear cluster, whilst the two northern clades from southern Africa corresponded to another nuclear cluster with three subclusters. One subcluster had a western and central distribution, another occurred mostly in the north-east, and the third in a small eastern region (Maputaland), which forms part of a biodiversity hotspot. Genetic diversity was low in the south and high in the north of our study region, particularly in the north-east. Our results refuted that translocations influenced the genetic structure of leopard tortoises substantially. We propose that Pleistocene climatic fluctuations caused leopard tortoises to retract to distinct refugia in southern and northern regions and ascribe the high genetic diversity in the north of southern Africa to genetic structuring caused by the survival in three refuges and subsequent admixture, whereas tortoises in the south seem to have survived in only one continuous coastal refuge