Aging and growth outside the comfort zone: the case of alien fire-bellied toads in France

Abstract

Understanding why some small populations succeed while others fail to establish in novel environments has major implications in applied fields such as in situ species conservation and reintroductions. Species introductions outside their native range provide excellent opportunities to address such topic, since invasions usually start with small populations. We studied the life-history strategy of a population of the fire-bellied toad (Bombina bombina) introduced in France, outside the natural range of the species, to estimate its population demographic potential. The introduced population showed a fast life history strategy, with early sexual maturation at 2 years of age, a relatively short life-span (3.1 years in females and 2.3 in males, with a maximum age of 5 years), and survival rates similar to those of populations from its native range. The population presents the characteristics for becoming invasive and might pose a threat to the native yellow-bellied toad (B. variegata) populations nearby through hybridization, competition and as potential vector of pathogens and parasites. Its spread should be closely monitored and additional introductions avoided to limit its potential negative impact.