Testing assertions of widespread introgressive hybridization in a clade of neotropical toads with low mate selectivity (Rhinella granulosa species group)

Author(s)

Rivera, Danielle ; Prates, Ivan ; Caldwell, Janalee P. ; Rodrigues, Miguel Trefaut ; Fujita, Matthew K.

• Document type: Journal article
• Source: HEREDITY; v. 130, n. 1, p. 8-pg., 2022-11-05.

Abstract

Discordance between different genomic regions, often identified through multilocus sequencing of selected markers, presents particular difficulties in identifying historical processes which drive species diversity and boundaries. Mechanisms causing discordance, such as incomplete lineage sorting or introgression due to interspecific hybridization, are better identified based on population-level genomic datasets. In the toads of the Rhinella granulosa species group, patterns of mito-nuclear discordance and potential hybridization have been reported by several studies. However, these patterns were proposed based on few loci, such that alternative mechanisms behind gene-tree heterogeneity cannot be ruled out. Using genome-wide ddRADseq loci from a subset of species within this clade, we found only partial concordance between currently recognized species-level taxon boundaries and patterns of genetic structure. While most taxa within the R. granulosa group correspond to clades, genetic clustering analyses sometimes grouped distinct taxonomic units into a single cluster. Moreover, levels of admixture between inferred clusters were limited and restricted to a single taxon pair which is best explained by incomplete lineage sorting as opposed to introgressive hybridization, according to D-statistics results. These findings contradict previous assertions of widespread cryptic diversity and gene flow within the R. granulosa clade. Lastly, our analyses suggest that diversification events within the Rhinella granulosa group mostly dated back to the early Pliocene, being generally younger than species divergences in other closely related clades that present high levels of cross-species gene flow. This finding uniquely contradicts common assertions that this young clade of toads exhibits interspecific hybridization. (AU)

• FAPESP's process: 03/10335-8 - Systematics and evolution of the herpetological fauna from Neotropical areas
• Grantee: Miguel Trefaut Urbano Rodrigues
• Support Opportunities: Research Projects - Thematic Grants
• FAPESP's process: 13/50297-0 - Dimensions US-BIOTA São Paulo: a multidisciplinary framework for biodiversity prediction in the Brazilian Atlantic forest hotspot
• Grantee: Cristina Yumi Miyaki
• Support Opportunities: BIOTA-FAPESP Program - Thematic Grants
• FAPESP's process: 11/50206-9 - Origin and evolution of snakes and their diversification in the Neotropics: a multidisciplinary approach
• Grantee: Hussam El Dine Zaher
• Support Opportunities: BIOTA-FAPESP Program - Thematic Grants
• FAPESP's process: 17/08357-6 - Phylogenetic Endemism and Comparative Phylogeography of the Brazilian Amazon Herpetofauna
• Grantee: Sérgio Marques de Souza
• Support Opportunities: Scholarships in Brazil - Post-Doctoral
• FAPESP's process: 11/50146-6 - Comparative phylogeography, phylogeny, paleoclimate modeling, and taxonomy of neotropical reptiles and amphibians
• Grantee: Miguel Trefaut Urbano Rodrigues
• Support Opportunities: BIOTA-FAPESP Program - Thematic Grants
• FAPESP's process: 12/15754-8 - Ecogeographical consequences of evolution of the snake-like morphotype in squamates
• Grantee: Agustín Camacho Guerrero
• Support Opportunities: Scholarships in Brazil - Post-Doctoral