Ocorrência da hibridação em anfíbios anuros: revisão sistemática e análise da influência da reprodução

Abstract

Hybridization is recognized as an important evolutionary process, capable of generating genetic and phenotypic variation, new adaptations, and, in some cases, new species. Consequently, the occurrence of hybrids poses a challenge to taxonomy and systematics, as hybrids often lack distinctive morphological, genetic, or behavioral traits. In anuran amphibians, this phenomenon may be associated with behavioral and ecological factors, such as reproductive patterns. In explosive breeding, the breeding season is short, and males and females gather in large aggregations after rainfalls, resulting in lower chances of female mate choice and thus favoring hybridization. In prolonged breeding, reproduction occurs over several weeks, during which males typically perform courtship behaviors that facilitate species recognition and allow female choice. However, the association between hybridization, reproductive patterns, and courtship behaviors remains poorly explored. We conducted a systematic review following the PRISMA protocol, searching Google Scholar and Web of Science between September 2023 and April 2024, aiming to provide a comprehensive analysis of hybridization occurrence in anuran amphibians in relation to reproductive behavior. A total of 1,893 articles were analyzed, 129 of which met the inclusion criteria, resulting in 88 confirmed records of hybridization across 34 genera and 10 families. The most represented genera were Anaxyrus (17 cases), Rhinella (11 cases), Dryophytes (9 cases), and Lithobates (7 cases). Among the different occurrences of hybridization associated with reproductive patterns, the family Hylidae concentrated hybridization cases in species with prolonged breeding, whereas explosive breeding cases occurred mostly within Bufonidae. Most hybridization cases involved two explosive-breeding species (50%), followed by two prolonged-breeding species (28%), and cases in which each species displayed a different reproductive pattern (9%). In 13% of cases, reproductive patterns were not reported in the literature. Regarding the presence of courtship, only five occurrences were documented: four in prolonged-breeding species and one in explosively- breeding species. This association was marginally non-significant (p = 0.054), indicating a tendency for prolonged-breeding species forming hybrids to have proportionally more documented courtship behaviors compared to explosively breeding species forming hybrids. Our results reinforce that explosive breeding increases the likelihood of hybridization, likely due to less effective mate choice mechanisms. However, the occurrence of hybridization in prolonged-breeding species and even in some with well documented courtship behaviors challenges the notion that these behaviors guarantee reproductive isolation. Thus, hybridization among anuran species appears to be more complex than previously assumed, and we discuss the data in light of potential mechanisms that may help explain this phenomenon. This study highlights gaps in the understanding of reproductive behavior and hybridization in anurans, emphasizing the need for integrative approaches combining genetics, ecology, and behavior to understand the evolution and persistence of lineages.