The origins of acoustic variation in the songs of Neotropical singing mice

Intraspecific variation in animal signaling is striking and complex, and it can impact individual fitness, reproductive isolation, and speciation. Understanding how variation in signals originate in individuals, populations, and species is a longstanding challenge of evolutionary biology. Here, I investigate acoustic variation in the dramatic advertisement songs of Alston’s singing mouse (Scotinomys teguina). Unlike their muroid ancestors and relatives, singing mice produce loud, long, and audible vocalizations that are used in mate attraction and intrasexual competition. I find that among individuals, songs differ most along two major dimensions of acoustic variation corresponding to variation in song effort and spectral characteristics. I examine how body condition predicts these acoustic axes and find that song effort is highly correlated with measures of adiposity, particularly leptin, a metabolic hormone that influences energetic investment into costly traits. Next, I estimate the heritability of song, finding high heritability for stable spectral characteristics and low heritability for dynamic effort-related measures. I also estimate heritability of body condition, then look for phenotypic and genetic correlations between acoustic and condition traits. I find strong phenotypic correlations between measures of song and body condition, and preliminary results show comparable estimates for genetic correlations. Finally, I examine patterns of genetic and phenotypic variation across populations of singing mice and ask whether microevolutionary patterns of genetic variation scale to macroevolutionary patterns. I find evidence that intraspecific variation in song effort is under stochastic processes and suggest that spectral characteristics may be under selection. Together, my results enrich our understanding of the evolution of an elaborate acoustic signal and illustrate how integrating across multiple fields can help address longstanding challenges in behavior and evolution in free-living and non-model species.Ecology, Evolution and Behavio