No abstract

The continental highlands of the Cameroon Volcanic Line (CVL) represent biological ‘sky islands’ with high levels of species richness and endemism, providing the ideal opportunity to understand how orogenesis and historical climate change influenced species diversity and distribution in these isolated African highlands. Relationships of puddle frogs (Phrynobatrachus) endemic to the CVL are reconstructed to examine the patterns and timing of puddle frog diversification. Historical distributions were reconstructed using both elevation and geography data. Puddle frogs diversified in the CVL via several dispersal and vicariance events, with most of the locally endemic species distributed across the northern part of the montane forest area in the Bamenda‐Banso Highlands (Bamboutos Mts., Mt. Lefo, Mt. Mbam, Mt. Oku and medium elevation areas connecting these mountains). Two new species, P. jimzimkusi sp. n. and P. njiomock sp. n., are also described based on molecular analyses and morphological examination. We find that these new species are most closely related to one another and P. steindachneri with the ranges of all three species overlapping at Mt. Oku. Phrynobatrachus jimzimkusi sp. n. is distributed in the southern portion of the continental CVL, P. njiomock sp. n. is endemic to Mt. Oku, and P. steindachneri is present in the northeastern part of the montane forest area. Both new species can be distinguished from all other puddle frogs by a combination of morphological characters, including their large size, ventral coloration and secondary sexual characteristics present in males. These results highlight the Bamenda‐Banso Highlands, and specifically emphasize Mt. Oku, as a centre of diversification for puddle frogs, supporting the conservation importance of this region. Our results also provide new insights into the evolutionary processes shaping the CVL ‘sky islands’, demonstrating that lineage diversification in these montane amphibians is significantly older than expected with most species diverging from their closest relative in the Miocene. Whereas climatic changes during the Pliocene and Pleistocene shaped intraspecific diversification, most speciation events were significantly older and cannot be linked to Africa's aridification in response to Pleistocene climate fluctuations.

A fundamental expectation of vicariance biogeography is for contemporary cladogenesis to produce spatial congruence between speciating sympatric clades. The Uroplatus leaf-tailed geckos represent one of most spectacular reptile radiations endemic to the continental island of Madagascar, and thus serve as an excellent group for examining patterns of continental speciation within this large and comparatively isolated tropical system. Here we present the first phylogeny that includes complete taxonomic sampling for the group, and is based on morphology and molecular (mitochondrial and nuclear DNA) data. This study includes all described species, and we also include data for eight new species. We find novel outgroup relationships for Uroplatus and find strongest support for Paroedura as its sister taxon. Uroplatus is estimated to have initially diverged during the mid-Tertiary in Madagascar, and includes two major speciose radiations exhibiting extensive spatial overlap and estimated contemporary periods of speciation. All sister species are either allopatric or parapatric. However, we found no evidence for biogeographic congruence between these sympatric clades, and dispersal events are prevalent in the dispersal-vicariance biogeographic analyses, which we estimate to date to the Miocene. One sister-species pair exhibits isolated distributions that we interpret as biogeographic relicts, and two sister-species pairs have parapatric distributions separated by elevation. Integrating ecological niche models with our phylogenetic results finds both conserved and divergent niches between sister species. We also found substantial intra-specific genetic variation, and for the three most widespread species, poor intra-specific predictive performance for ecological niche models across the latitudinal span of Madagascar. These latter results indicate the potential for intra-specific niche specialization along environmental gradients, and more generally, this study suggests a complex speciation history for this group in Madagascar, which appears to include multiple speciation processes.

The Mascarene ridged frog, Ptychadena mascareniensis, is a species complex that includes numerous lineages occurring mostly in humid savannas and open forests of mainland Africa, Madagascar, the Seychelles, and the Mascarene Islands. Sampling across this broad distribution presents an opportunity to examine the genetic differentiation within this complex and to investigate how the evolution of bioclimatic niches may have shaped current biogeographic patterns. Using model-based phylogenetic methods and molecular-clock dating, we constructed a time-calibrated molecular phylogenetic hypothesis for the group based on mitochondrial 16S rRNA and cytochrome b (cytb) genes and the nuclear RAG1 gene from 173 individuals. Haplotype networks were reconstructed and species boundaries were investigated using three species-delimitation approaches: Bayesian generalized mixed Yule-coalescent model (bGMYC), the Poisson Tree Process model (PTP) and a cluster algorithm (SpeciesIdentifier). Estimates of similarity in bioclimatic niche were calculated from species-distribution models (maxent) and multivariate statistics (Principal Component Analysis, Discriminant Function Analysis). Ancestral-area reconstructions were performed on the phylogeny using probabilistic approaches implemented in BioGeoBEARS. We detected high levels of genetic differentiation yielding ten distinct lineages or operational taxonomic units, and Central Africa was found to be a diversity hotspot for these frogs. Most speciation events took place throughout the Miocene, including "out-of-Africa" overseas dispersal events to Madagascar in the East and to São Tomé in the West. Bioclimatic niche was remarkably well conserved, with most species tolerating similar temperature and rainfall conditions common to the Central African region. The P. mascareniensis complex provides insights into how bioclimatic niche shaped the current biogeographic patterns with niche conservatism being exhibited by the Central African radiation and niche divergence shaping populations in West Africa and Madagascar. Central Africa, including the Albertine Rift region, has been an important center of diversification for this species complex.