Phenotypic variability and environmental tolerance shed light on nine-banded armadillo Nearctic invasion

Abstract

High phenotypic diversity is an intrinsic attribute of successful invaders, but remains poorly studied. Here, we investigate the role of phenotypic traits in biological invasions using one of the few Neotropical mammal lineages that has successfully invaded the Nearctic, the nine-banded armadillo Dasypus novemcinctus. Specifically, we analyzed cranial phenotypic variation of the nine-banded armadillo, comparing ecological associations throughout its native range with those experienced by invasive populations in the United States. We also compared the climatic conditions faced by native and invader armadillos to determine whether the species has broadened its environmental tolerance or remained within its native climatic pool. Our study shows that D. novemcinctus exhibits pronounced morphological variation through its range and that the phenotypic pattern in newly invaded areas departs from trends of the species in its native range. The morphological differences exhibited by invader armadillos can be related to their reduced reliance on myrmecophagy, with armadillos from temperate open areas in North America exploiting a broader range of dietary items. Moreover, we found the climatic conditions faced by alien armadillos during the initial phases of their Nearctic invasion fell within the native climatic range. In sum, high phenotypic variability and substantial environmental tolerance in the nine-banded armadillo help to explain its nearly ubiquitous distribution across contrasting ecosystems in its native range as well as its successful Nearctic invasion. Our findings underscore the importance of studying the covariation of morphology and climate across native and invasive ranges to understand biological responses in novel environments.