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Acoustic phenotypic variation is of major importance for speciation and the evolution of species diversity. Whereas selective and stochastic forces shaping the acoustic divergence of signaling systems are well studied in insects, frogs, and birds, knowledge on the processes driving acoustic phenotypic evolution in mammals is limited. We quantified the acoustic variation of a call type exchanged during agonistic encounters across eight distinct species of the smallest‐bodied nocturnal primate radiation, the Malagasy mouse lemurs. The species live in two different habitats (dry forest vs. humid forest), differ in geographic distance to each other, and belong to four distinct phylogenetic clades within the genus. Genetically defined species were discriminated reliably on the phenotypic level based on their acoustic distinctiveness in a discriminant function analysis. Acoustic variation was explained by genetic distance, whereas differences in morphology, forest type, or geographic distance had no effect. The strong impact of genetics was supported by a correlation between acoustic and genetic distance and the high agreement in branching pattern between the acoustic and molecular phylogenetic trees. In sum, stochastic factors such as genetic drift best explained acoustic diversification in a social communication call of mouse lemurs., The study shows that eight cryptic mouse lemur species differ in the acoustic parameters of their agonistic Tsak calls. This acoustic diversification can be best explained by stochastic factors such as genetic drift rather than by ecology.

Reproduction is a fundamental trait in the life history of any species and contributes to species diversity and evolution. Here, we aim to review the barely known variation in reproductive patterns of the smallest-bodied primate radiation, the Malagasy mouse lemurs, focusing on twelve species of four phylogenetic clades. We present a new reproductive field dataset collected between May and November 1996-2016 for nine species (Microcebus murinus, M. myoxinus, M. ravelobensis, M. bongolavensis, M. danfossi, M. sambiranensis, M. margothmarshae, M. mamiratra, and M. lehilahytsara) and add published field information on three additional species. In the majority of species, the estrus of females was recorded in the period of long days (day length longer than 12 hr), whereas male testes size increased about one to three months prior to this. Reproductive schedules varied considerably between the four clades. Sympatric species-pairs of different clades differed in the timing of female and male reproduction, suggesting strong phylogenetic constraints. Populations of the same species in a different ecological setting varied in the onset of reproduction, suggesting substantial environmental plasticity. Warm temperatures and rainfall throughout the year may allow for less expressed reproductive seasonality. Our results suggest that an interplay between phylogenetic relatedness, ambient temperature (as a proxy for thermo regulatory constraints), and rainfall (as a proxy for food availability), may best explain this variation. Findings further point to a more complex control of mouse lemur reproduction than previously described and illuminate phylogenetic constraints and adaptive potentials in behavioral reaction norms of a species-rich primate radiation.