Lack of genetic variation prevents adaptation at the geographic range margin in a damselfly. Issue 18 (26th August 2016)

• Record Type: Journal Article
• Authors: Takahashi, Yuma; Suyama, Yoshihisa; Matsuki, Yu; Funayama, Ryo; Nakayama, Keiko; Kawata, Masakado
• Is Part Of: Molecular ecology. Volume 25:Issue 18(2016)
• Page Start: 4450
• Page End: 4460
• Publication Date: 2016-08-26
• Subjects: adaptation -- damselfly -- distribution range -- genetic diversity -- migration load -- range margin; Molecular ecology -- Periodicals; Molecular population biology -- Periodicals; 576
• DOI: 10.1111/mec.13782
• Languages: English
• ISSNs: 0962-1083

Abstract

Abstract: What limits a species' distribution in the absence of physical barriers? Genetic load due to asymmetric gene flow and the absence of genetic variation due to lack of gene flow are hypothesized to constrain adaptation to novel environments in marginal populations, preventing range expansion. Here, we examined the genetic structure and geographic variation in morphological traits in two damselflies ( Ischnura asiatica and I. senegalensis ) along a latitudinal gradient in Japan, which is the distribution centre of I. asiatica and the northern limit of I. senegalensis . Genomewide genetic analyses found a loss of genetic diversity at the edge of distribution in I. senegalensis but consistently high diversity in I. asiatica . Gene flow was asymmetric in a south–north direction in both species. Although body size and wing loading showed decreasing latitudinal clines (smaller in north) in I. asiatica in Japan, increasing latitudinal clines (larger in north) in these phenotypic markers were observed in I. senegalensis, particularly near the northern boundary, which coincided well with the location where genetic diversity began a sharp decline. In ectothermic animals, increasing latitudinal cline in these traits was suggested to be established when they failed to adapt to thermal gradient. Therefore, our findings support the possibility that a lack of genetic variation rather than geneflow swamping is responsible for the constraint of adaptation at the margin of geographic distribution.