Geographic variation, population structure, behavioral discrimination, and taxonomy of the most polytypic antbirds (Aves, Thamnophilidae)

Author(s)

Rafael Dantas Lima

• Document type: Master's Dissertation
• Press: São Paulo.
• Institution: Universidade de São Paulo (USP). Instituto de Biociências (IBIOC/SB)
• Defense date: 2024-06-04

Examining board members

Luis Fábio Silveira; Vítor de Queiroz Piacentini; Glaucia Cristina Del Rio

• Advisor: Luis Fábio Silveira

Abstract

Species and subspecies taxa are foundational to much biological research, making accurate taxonomy crucial across various biological disciplines. Many existing taxa, however, predate modern standards, underscoring the critical need for taxonomic revision. The speciose avian family Thamnophilidae has seen considerable taxonomic progress, driven largely by new insights into traits that indicate lineage divergence and affect reproductive isolation. Despite these advancements, many thamnophilid taxa remain that have not yet been thoroughly revised in light of these insights. The Plain Antvireo (Dysithamnus mentalis) and Variable Antshrike (Thamnophilus caerulescens) stand out as prime candidates for taxonomic revision within the family. They have unusually great amounts of geographic plumage variation, reflected in as many as eighteen and twelve described subspecies, respectively. They have each variably been treated as comprising either a single or multiple species taxa, and it is presently unclear to what extent their differentiated populations exist as discrete clusters versus as continua. Critically, despite the recognized importance of premating isolation mediated by divergence in vocalizations and postmating isolation in thamnophilid speciation, comprehensive characterizations of vocal variation and genetic structure across their entire ranges are lacking. Here, I combined morphological, vocal, and genomic data to characterize geographic variation and population genetic structure in the Plain Antvireo and Variable Antshrike. For D. mentalis, I identified 1214 phenotypically diagnosable populations forming six distinct nuclear genomic clusters. In contrast with its geographically structured phenotype and nuclear genome, the D. mentalis complex exhibits no geographic structuring of mitochondrial haplotypes. My analysis also uncovered several previously unrecognized hybrid zones and suggest that premating reproductive isolation is generally weak or nonexistent among most lineages, thus largely supporting their continued classification as a single biological species. For T. caerulescens, I found nine phenotypically distinct populations, including seven previously recognized taxa and two newly described ones. My results establish that one lineage (T. c. cearensis) has evolved substantial reproductive isolation from all others in the complex and is thus best treated as a separate biological species. The remaining populations of the Variable Antshrike showed low levels of reproductive isolation and are therefore kept as members of a single species, although some show genome-wide divergence that could justify future species status upon further investigation of newly identified contact zones. In general, my results significantly advance our understanding of the geographic variation and population structure of the D. mentalis and T. caerulescens complexes and provide novel working hypotheses for downstream science. (AU)

• FAPESP's process: 21/10339-1 - Integrative taxonomy of two highly polytypic thamnophilids (Aves: Thamnophilidae)
• Grantee: Rafael Dantas Lima
• Support Opportunities: Scholarships in Brazil - Master