RADseq data reveal a lack of admixture in a mouse lemur contact zone contrary to previous microsatellite results

Microsatellites have been a workhorse of evolutionary genetic studies for
decades and are still commonly in use for estimating signatures of genetic
diversity at the population and species level across a multitude of taxa.
Yet, the very high mutation rate of these loci is a double-edged sword,
conferring great sensitivity at shallow levels of analysis (e.g.,
paternity analysis) but yielding considerable uncertainty for deeper
evolutionary comparisons. For the present study, we used reduced
representation genome-wide data (RADseq) to test for patterns of
interspecific hybridization previously characterized using microsatellite
data in a contact zone between two closely related mouse lemur species in
Madagascar (Microcebus murinus and M. griseorufus). We revisit this system
by examining populations in, near, and far from the contact zone,
including many of the same individuals that had previously been identified
as hybrids with microsatellite data. Surprisingly, we find no evidence for
admixed nuclear ancestry. Instead, re-analyses of microsatellite data and
simulations suggest that previously inferred hybrids were false positives
and that the program NewHybrids can be particularly sensitive to
erroneously inferring hybrid ancestry. Combined with results from
coalescent-based analyses and evidence for local syntopic co-occurrence,
we conclude that the two mouse lemur species are in fact completely
reproductively isolated, thus providing a cautionary tale for the
inference of interspecific hybridization with microsatellite data.