Investigating the cause of the disjunct distribution of Amietophrynus pantherinus, the Endangered South African western leopard toad

Assessing the effects of climate change on distributions of Cape Floristic Region amphibians

Abstract Climatic changes have had profound impacts on species distributions throughout time. In response, species have shifted ranges, adapted genetically and behaviourally or become extinct. Using species distribution models, we examined how changes in suitable climatic space could affect the distributions of 37 endemic frog species in the Cape Floristic Region (CFR) – an area proposed to have evolved its megadiversity under a stable climate, which is expected to change substantially in future. Species distributions were projected onto mean climate for a current period (1950 to 2000), hindcasted to palaeoclimate (Last Glacial Maximum; LGM ≈ 21 kya and Holocene Glacial Minimum; HGM ≈ 6 kya) and forecasted for two emissions scenarios (A2a and B2a) for the year 2080. We then determined the changes in area sizes, direction (longitude and latitude), fragmentation index and biotic velocity, and assessed if these were affected by life-history traits and altitude. We found that the biotic velocity at which the CFR amphibian community is expected to shift north (A2a ≈ 540.5 km/kya) and east (B2a ≈ 198 km/kya) far exceeds historical background rates (≈1.05 km/kya, north and west ≈ 2.36 km/kya since the LGM). Our models further suggest that the CFR amphibian community has already lost about 56% of suitable climate space since the LGM and this loss is expected to accelerate under future emission scenarios (A2a ≈ 70%; B2a ≈ 60%). Lastly, we found that highland species were more fragmented than lowland species between the LGM and current period, but that the fragmentation of lowland species between current and future climates is expected to increase.

Evidence from peptidomic analysis of skin secretions that allopatric populations of Xenopus gilli (Anura:Pipidae) constitute distinct lineages

The International Union for Conservation of Nature (IUCN) Endangered Cape Platanna Xenopus gilli inhabits disjunct ranges at the tip of Cape Peninsula and near the town of Kleinmond on opposite sides of False Bay in the extreme southwest of Africa. Peptidomic analysis of host-defense peptides in norepinephrine-stimulated skin secretions from frogs from the Cape Peninsula range resulted in the identification of two magainins, two peptide glycine-leucine-amide (PGLa) peptides, two xenopsin-precursor fragment (XPF) peptides, nine caerulein-precursor fragment (CPF) peptides, and a peptide related to peptide glycine-glutamine (PGQ) previously found in an extract of Xenopus laevis stomach. The primary structures of the peptides indicate a close phylogenetic relationship between X. gilli and X. laevis but only magainin-1, PGLa and one CPF peptide are identical in both species. Consistent with previous data, the CPF peptides show the greatest antimicrobial potency but are hemolytic. There are appreciable differences in the expression of host-defense peptide genes in frogs from the population of animals sampled near Kleinmond as peptides corresponding to magainin-G2, XPF-G1, XPF-G2, and four CPF peptides, present in secretions from the Cape Peninsula frogs, were not identified in the skin secretions from Kleinmond frogs. Conversely, PGLa-G3, XPF-G3, and three CPF peptides were identified in the Kleinmond frogs but not in the Cape Peninsula animals. The data support the conclusion from morphometric analyses and comparisons of the nucleotide sequences of mitochondrial genes that the disjunct populations of X. gilli have undergone appreciable genetic, morphological, and phenotypic divergence.

Fading out of view: the enigmatic decline of Rose's mountain toad Capensibufo rosei

Rose's mountain toad Capensibufo rosei survives in a few isolated montane populations in the south-western Cape of South Africa. It comprises several cryptic species but it is uncertain whether the lineage on the Cape Peninsula is distinct. We tested the hypothesis that toads from the Peninsula form a single genetic lineage but that different breeding sites are divergent at a population level as a result of limited dispersal abilities. Directed surveys were carried out to locate breeding sites and samples obtained were analysed in a phylogenetic and population genetic framework, using two mitochondrial markers. We found toads breeding at only one of five known historical breeding sites, although one new breeding site was also recorded. No toads were observed at 15 other non-breeding localities where they were historically observed. Toads from the two active breeding sites formed a single lineage that was sufficiently distinct to be given species status. However, these were discrete at a population level, with no shared haplotypes, suggesting no gene flow between sites. One site was particularly low in genetic diversity, implying increased vulnerability to stochastic events and elevated risk of extinction. These results, coupled with the failure to locate historically known sites on the Cape Peninsula, make this newly recognized Peninsula endemic a conservation priority. Efforts should focus on the protection and expansion of the two known surviving populations and the patches of habitat upon which they rely.

Mind the gaps: investigating the cause of the current range disjunction in the Cape Platanna, Xenopus gilli (Anura: Pipidae)

Low-lying areas of the Cape at Africa’s south-westernmost tip have undergone dramatic marine-remodelling, with regular changes in sea-level following glacial cycles. Species for which marine barriers are impenetrable underwent concomitant radical distribution changes which may account for current range disjunctions. The Cape platanna, Xenopus gilli, is a frog distributed in only three disjunt areas within low-lying regions of the southwestern Cape. We determined the relationship between frogs from these three disjunct areas, by using a combination of morphometric analysis and mtDNA (ND2 and 16S fragments) sequences of 130 frogs from eight ponds. Coalescent analyses on molecular data dated the divergence in two major clades to around 4.6 Mya, a period during which major uplifting on the eastern side of the subcontinent caused climate changes throughout southern Africa. Principal components analysis showed significant morphometric differences between each clade on head and limb measurements. Consistent differences in ventral colouration and patterning were also observed. We report on increased levels of hybridisation with X. laevis throughout the range of X. gilli, which reaches at least 27% hybrids in some ponds. Urgent conservation actions are required to control habitat loss from alien invasive vegetation, and prevent introgression with the domestic-exotic, X. laevis.

Effect of Pleistocene climatic oscillations on the phylogeography and demography of red knobby newt (Tylototriton shanjing) from southwestern China

Factors that determine the genetic structure of species in southwestern China remain largely unknown. In this study, phylogeography and demography of Tylototriton shanjing was investigated from a mitochondrial perspective to address the role of the Quaternary ice ages in shaping phylogeographic history and genetic diversity of Yunnan. A total of 146 individuals from 19 populations across the entire range of the species were collected. We detected four maternal phylogenetic lineages corresponding to four population groups, and found that major glaciation events during the Pleistocene have triggered the intra-specific divergence. Coalescent simulations indicated that the populations retreated to different refugia located in southern Yunnan, northwestern Yunnan, the border region of western Yunnan with Myanmar, and middle-western Yunnan, respectively, during previous glacial periods in the Pleistocene, and these four refugia were not retained during the Last Glacial Maximum. Population expansions occurred during the last inter-glaciation, during which ice core and pollen data indicated that the temperature and precipitation gradually increased, and declines of population sizes started after the beginning of the Last Glacial Maximum when the climate became cooler and dryer. The paleo-drainage system had no contribution to the current genetic structure and the rivers were not dispersal barriers for this salamander.

Phylogeography and demographic history of Babina pleuraden (Anura, Ranidae) in southwestern China

Factors that determine genetic structure of species in southwestern China remain largely unknown. In this study, sequences of two mitochondrial genes (COI and cyt b) were determined to investigate the phylogeography and demography of Babina pleuraden, a pond frog endemic to southwestern China. A total of 262 individuals from 22 populations across the entire range of the species were collected. Our results indicate that B. pleuraden comprises five well-supported mitochondrial lineages roughly corresponding to five geographical areas. The phylogeographic structure of B. pleuraden has been shaped primarily by the unique regional responses of the Yunnan Plateau to the rapid uplift of the Qinghai-Tibetan Plateau occurred c. 2.5 Mya (B phrase of Qingzang Movement) and climatic oscillation during middle Pleistocene (c. 0.64–0.36 Mya), rather than by the paleo-drainage systems. The present wide distribution of the species has resulted from recent population expansion (c. 0.053–0.025 Mya) from multiple refugia prior to the Last Glacial Maximum, corresponding to the scenario of “refugia within refugia”.