Convergent evolution in social swallows (Aves: Hirundinidae). Issue 2 (20th December 2016)

• Record Type: Journal Article
• Authors: Johnson, Allison E.; Mitchell, Jonathan S.; Brown, Mary Bomberger
• Is Part Of: Ecology and evolution. Volume 7:Issue 2(2017:Feb.)
• Page Start: 550
• Page End: 560
• Publication Date: 2016-12-20
• Subjects: coloniality -- convergent evolution -- morphology -- sociality; Ecology -- Periodicals; Evolution -- Periodicals; 577.05
• DOI: 10.1002/ece3.2641
• Languages: English
• ISSNs: 2045-7758

Abstract

Abstract: Behavioral shifts can initiate morphological evolution by pushing lineages into new adaptive zones. This has primarily been examined in ecological behaviors, such as foraging, but social behaviors may also alter morphology. Swallows and martins (Hirundinidae) are aerial insectivores that exhibit a range of social behaviors, from solitary to colonial breeding and foraging. Using a well‐resolved phylogenetic tree, a database of social behaviors, and morphological measurements, we ask how shifts from solitary to social breeding and foraging have affected morphological evolution in the Hirundinidae. Using a threshold model of discrete state evolution, we find that shifts in both breeding and foraging social behavior are common across the phylogeny of swallows. Solitary swallows have highly variable morphology, while social swallows show much less absolute variance in all morphological traits. Metrics of convergence based on both the trajectory of social lineages through morphospace and the overall morphological distance between social species scaled by their phylogenetic distance indicate strong convergence in social swallows, especially socially foraging swallows. Smaller physical traits generally observed in social species suggest that social species benefit from a distinctive flight style, likely increasing maneuverability and foraging success and reducing in‐flight collisions within large flocks. These results highlight the importance of sociality in species evolution, a link that had previously been examined only in eusocial insects and primates. Abstract : Using a bird family with diversity in social behavior, the swallows and martins (Hirundinidae), we examine how switches between social and nonsocial behavior influence morphological evolution. We find strong convergence in social swallow species to small body morphology, while solitary swallow species exhibit highly variable morphology. These results illustrate the importance of social behavior on morphological evolution. Photograph by Joel G. Jorgensen.