Name: Dinis M
Title: Gene flow and environmental differentiation between viviparous and ovoviviparous populations of Salamandra algira tingitana
Institution: University of Porto
The Mediterranean Basin is a Global Hotspot of Biodiversity, exhibiting high levels of endemism and is considered an important centre of diversification, which is attributable to its complex biogeographic history, shaped by periods of connectivity between the European and African continents and by the interplay between the climatic oscillations of the Quaternary, and the high topographic complexity of the region.
The North African fire salamander Salamandra algira is the sole African representative of the Palearctic genus Salamandra, believed to have colonized North Africa across the Strait of Gibraltar. Past climatic oscillations likely played a key role in the evolutionary history of this species, resulting in four allopatric subspecies presently restricted to Moroccan and Algerian mountain ranges. Like in other North African species of Palearctic origin, S. algira populations tend to be associated with relatively mild climates and vegetation cover, which likely contributes to its fragmented distribution.
In the Moroccan Rif, four sublineages, belonging to the subspecies S. a. tingitana and S. a. splendens, occur in a relatively small area of complex topography, separated by narrow contact zones. The Rif populations of S. algira are an interesting research model due to the occurrence of pueriparous reproduction in a sublineage of S. a. tingitana, while larviparity is the predominant reproductive strategy for most of the species.
This work seeks to assess the impact of Pleistocene climatic oscillations and detect potential climatic refugia for S. algira, to assess the geographic structure of genetic diversity and the effect of topo-climatic and habitat variability on the ecological niche segregation in the Rif sublineages, and to elucidate the evolutionary and ecological context of pueriparity. To accomplish these goals, an integrated approach combining microsatellite and mtDNA information with ecological niche models and niche overlap tests was used. Furthermore, the extent and severity of habitat degradation due to vegetation loss from 2006 to 2014 was assessed for North Africa, with particular focus on the threat to Palearctic relicts, using S. algira as model.
Results reveal new insights on the context of pueriparity in the Rif, with the identification of a new pueriparous population on a sublineage previously believed to be strictly larviparous, and evidence for an association between pueriparity and relatively water-independent habitats.
Population structure and gene flow at secondary contact zones between Rif sublineages and subspecies were identified. Lineages showed distinct responses to climate and habitat factors, though partial overlap between models suggests distributions in the Rif may not be fully allopatric and niches not fully divergent. Independent areas of climatic stability were identified for each subspecies.
Habitat degradation by vegetation loss was identified in areas of intense human activity in the Rif, Middle Atlas and eastern Algeria. Populations of S. algira subject to recent vegetation loss were identified in the contact zone between Rif subspecies, within the Talassemtane National Park.
Overall, these results suggest a pattern of allopatric divergence within Paleoclimatic refugia at both the subspecies and sublineage levels, followed, in the case of the Rif populations, by secondary contact facilitated by non-fully divergent ecological niches. Despite the still undisclosed evolutionary history of pueriparity in S. algira, this work supports the “dry climate hypothesis” for the evolution of pueriparity in Salamandra. The identification of areas of severe habitat degradation provides a valuable resource for prioritizing future conservation efforts for relict Palearctic species in North Africa, and for S. algira in particular.