Reconstructing the demographic history of a nocturnal primate, Microcebus arnholdi, during the late Quaternary

Marked climatic oscillations during the Pleistocene had consequences for vegetation and animal population dynamics worldwide. Mouse lemurs (Microcebus spp.) are forest-dwelling primates that are endemic to Madagascar for which Pleistocene climatic and vegetation changes have been postulated and patchily shown. Microcebus arnholdi is a mouse lemur species restricted to Montagne d’Ambre National Park in northern Madagascar. This study aims to evaluate the demographic dynamics of two populations of M. arnholdi during the late Quaternary. Two populations were sampled (2 x 33 individuals) in a continuous montane humid forest at 1,073 m a.s.l., and in a discontinuous evergreen forest interspersed with savannah situated at 848 m a.s.l. Whereas we hypothesize that the higher elevation areas of Montagne d’Ambre constituted a Pleistocene refugium with continuous forest cover, we still predict a population bottleneck as a result of vegetation contraction during the Last Glacial Maximum (LGM), which should be stronger for the population sampled in the discontinuous forest at lower altitude than for the population sampled in the mid-elevation continuous forest. Clustering methods were initially used to assess genetic structure and revealed that our samples belong to geographically distinct genetic clusters. Demographic fluctuations were then reconstructed by three complementary methods. First, two approaches assuming panmixia were used to infer demographic trajectories over recent (Stairway Plots) and more ancient times (PSMC), by using RADseq and full genome data, respectively. Additionally, a simulation based approach (fastsimcoal2) was used to test the fit of a suite of more complex demographic models to the observed data, including genetic structure. Preliminary results point towards the occurrence of an ancient bottleneck during the LGM (25 kya), followed by a population expansion until the mid-Holocene (8 kya), and a subsequent population decline in both populations.