Subspecies limits based on morphometry and mitochondrial DNA genomics in a polytypic species, the common grackle, Quiscalus quiscula

• Published in: Biological journal of the Linnean Society Vol. 139; no. 1; pp. 39 - 56
• Main Authors: Capainolo, Peter, Perktaş, Utku, ElverıCı, Can, Fellowes, Mark D E
• Format: Journal Article
• Language: English
• Published: UK Oxford University Press 03-05-2023
• Subjects: Bats; Body size; Character recognition; Climate change; Deoxyribonucleic acid; Differentiation; DNA; DNA structure; Gene flow; Genetic analysis; Genetic diversity; Haplotypes; Migratory birds; Migratory species; Mitochondrial DNA; Morphometry; Nominations; Phylogeny; Quiscalus quiscula; Songbirds; Florida; United States > US; Nearctic songbirds; demographic history; North America; mitochondrial DNA; climate change; phylogeography
• ISSN: 0024-4066; 1095-8312
• DOI: 10.1093/biolinnean/blad009

Abstract
Nearctic migratory songbirds have demonstrated low levels of genetic differentiation and weak phylogeographical structure in mitochondrial DNA lineages compared with resident species. The common grackle, Quiscalus quiscula, is a widespread, partially migratory, North American icterid composed of three currently recognized subspecies. In this study, mensural characters (external and skeletal measurements) and the complete mitochondrial genome together with two mitochondrial genes, Cytb and ND2, were used to investigate subspecific differentiation and demographic history of the common grackle. The results showed substantial variation in body size among subspecies, mostly distributed between the ‘Florida grackle’, Quiscalus quiscula quiscula, and the two other subspecies. Analysis of mitochondrial DNA indicated low levels of genetic variation, but we found distinct haplotypes in Florida that form a clade in the phylogenetic tree. This suggests that the nominate subspecies in Florida is a distinct evolutionary unit. The sharing of haplotypes among the other subspecies (Quiscalus quiscula versicolor and Quiscalus quiscula stonei) in the north suggests high levels of gene flow, making the status of these two subspecies equivocal. Gene flow between nominate Q. q. quiscula, Q. q. versicolor and putative Q. q. stonei is probably attributable to historical changes in distribution and abundance following climate change events. We therefore recognize only two subspecies in the common grackle complex.