Secondary contact erodes Pleistocene diversification in a wide-ranging freshwater mussel (Quadrula)

Molecular Ecology
By: , and 

Links

Abstract

The isolated river drainages of eastern North America serve as a natural laboratory to investigate the roles of allopatry and secondary contact in the evolutionary trajectories of recently diverged lineages. Drainage divides facilitate allopatric speciation, but due to their sensitivity to climatic and geomorphological changes, neighboring rivers frequently coalesce, creating recurrent opportunities of isolation and contact throughout the history of aquatic lineages. The freshwater mussel Quadrula quadrula is widely distributed across isolated rivers of eastern North America and possesses high phenotypic and molecular variation across its range. We integrate sequence data from three genomes, including female- and male-inherited mitochondrial markers and thousands of nuclear encoded SNPs with morphology and geography to illuminate the group's divergence history. Across contemporary isolated rivers, we found continuums of molecular and morphological variation, following a pattern of isolation by distance. In contact zones, hybridization was frequent with no apparent fitness consequences, as advanced hybrids were common. Accordingly, we recognize Q. quadrula as a single cohesive species with subspecific variation (Q. quadrula rumphiana). Demographic modeling and divergence dating supported a divergence history characterized by allopatric vicariance followed by secondary contact, likely driven by river rearrangements and Pleistocene glacial cycles. Despite clinal range-wide variation and hybridization in contact zones, the process-based species delimitation tool delimitR, which considers demographic scenarios like secondary contact, supported the delimitation of the maximum number of species tested. As such, when interpreting species delimitation results, we suggest careful consideration of spatial sampling and subsequent geographic patterns of biological variation, particularly for wide-ranging taxa.

Study Area

Publication type Article
Publication Subtype Journal Article
Title Secondary contact erodes Pleistocene diversification in a wide-ranging freshwater mussel (Quadrula)
Series title Molecular Ecology
DOI 10.1111/mec.17572
Edition Online First
Year Published 2024
Language English
Publisher Wiley
Contributing office(s) Wetland and Aquatic Research Center
Description e17572, 17 p.
Country Canada, United States
Other Geospatial eastern North America
Google Analytic Metrics Metrics page
Additional publication details