Hybridization of mouse lemurs: different patterns under different ecological conditions

Abstract

BackgroundSeveral mechanistic models aim to explain the diversification of the multitude of endemic species on Madagascar. The island's biogeographic history probably offered numerous opportunities for secondary contact and subsequent hybridization. Existing diversification models do not consider a possible role of these processes. One key question for a better understanding of their potential importance is how they are influenced by different environmental settings. Here, we characterized a contact zone between two species of mouse lemurs, Microcebus griseorufus and M. murinus, in dry spiny bush and mesic gallery forest that border each other sharply without intermediate habitats between them. We performed population genetic analyses based on mtDNA sequences and nine nuclear microsatellites and compared the results to a known hybrid zone of the same species in a nearby wide gradient from dry spiny bush over transitional forest to humid littoral forest.ResultsIn the spiny-gallery system, Microcebus griseorufus is restricted to the spiny bush; Microcebus murinus occurs in gallery forest and locally invades the dryer habitat of its congener. We found evidence for bidirectional introgressive hybridization, which is closely linked to increased spatial overlap within the spiny bush. Within 159 individuals, we observed 18 hybrids with mitochondrial haplotypes of both species. Analyses of simulated microsatellite data indicate that we identified hybrids with great accuracy and that we probably underestimated their true number. We discuss short-term climatic fluctuations as potential trigger for the dynamic of invasion and subsequent hybridization. In the gradient hybrid zone in turn, long-term aridification could have favored unidirectional nuclear introgression from Microcebus griseorufus into M. murinus in transitional forest.ConclusionsMadagascar's southeastern transitional zone harbors two very different hybrid zones of mouse lemurs in different environmental settings. This sheds light on the multitude of opportunities for the formation of hybrid zones and indicates an important influence of environmental factors on secondary contact and hybridization. Our findings suggest that hybridization could enhance the adaptability of mouse lemurs without necessarily leading to a loss of distinctiveness. They point to a potential role of hybridization in Madagascar's diversification history that requires further investigation.

Habitat Separation of Sympatric Microcebus spp. in the Dry Spiny Forest of South-Eastern Madagascar

“…This matches the situation found elsewhere [Yoder et al, 2002;Génin, 2008]. However, in Andohahela the two species also occur sympatrically and hybridize at the ecotone between dry spiny and gallery forests [Gligor et al, 2009;Hapke et al, 2011, Rakotondranary et al, 2011a. These seemingly clear habitat associations of the two species indicate that habitat structure could be a niche dimension for species separation.…”

“…In the field, animals were classified based on morphological criteria [Rakotondranary et al, 2011a]. Identifications were verified on the bases of mitochondrial DNA and microsatellites [Hapke et al, 2011]. Capture and genetic verification of species identification were necessary to develop morphological criteria that will guarantee correct assignment of morphotypes to species and to identify hybrids.…”

Multilocus coalescent analyses reveal the demographic history and speciation patterns of mouse lemur sister species

“…[41,44]). We sought to utilize genes with sufficient sequence variation to reliably estimate coalescent parameters.…”

“…Over the extensive range of M. murinus , the species has been found to overlap with multiple congeners [37,38], many of which exhibit a high degree of endemicity. One example of this pattern of sympatry couples M. murinus with M. griseorufus , with multiple lines of evidence for distribution overlap and potential hybridization between the two species in southern Madagascar [39-41]. Within their respective ranges, M. murinus and M. griseorufus also exhibit marked differences in abundance.…”

Population genetics implications for the conservation of the Philippine Crocodile Crocodylus mindorensis Schmidt, 1935 (Crocodylia: Crocodylidae)

“…Occasionally STRUCTURE overestimates the optimal K value; hence, Evanno et al (2005) developed an ad hoc test statistic ∆K to evaluate the output files in addition to approximating the asymptote of the posterior probability curve. At K-max, we applied a conservative threshold of q≥0.05 to the membership coefficient (q-value) of the cluster attributed to the introgressing species to identify hybrids (Hapke et al 2011).…”