Divergent selection on flowering phenology but not on floral morphology between two closely related orchids. Issue 12 (6th May 2020)

• Record Type: Journal Article
• Authors: Chapurlat, Elodie; Le Roncé, Iris; Ågren, Jon; Sletvold, Nina
• Is Part Of: Ecology and evolution. Volume 10:Issue 12(2020)
• Page Start: 5737
• Page End: 5747
• Publication Date: 2020-05-06
• Subjects: divergent selection -- flowering phenology -- Gymnadenia -- phenological isolation -- plant–pollinator interactions -- reproductive barriers -- species divergence; Ecology -- Periodicals; Evolution -- Periodicals; 577.05
• DOI: 10.1002/ece3.6312
• Languages: English
• ISSNs: 2045-7758

Abstract

Abstract: Closely related species often differ in traits that influence reproductive success, suggesting that divergent selection on such traits contribute to the maintenance of species boundaries. G ymnadenia conopsea ss. and Gymnadenia densiflora are two closely related, perennial orchid species that differ in (a) floral traits important for pollination, including flowering phenology, floral display, and spur length, and (b) dominant pollinators. If plant–pollinator interactions contribute to the maintenance of trait differences between these two taxa, we expect current divergent selection on flowering phenology and floral morphology between the two species. We quantified phenotypic selection via female fitness in one year on flowering start, three floral display traits (plant height, number of flowers, and corolla size) and spur length, in six populations of G. conopsea s.s. and in four populations of G. densiflora. There was indication of divergent selection on flowering start in the expected direction, with selection for earlier flowering in two populations of the early‐flowering G. conopsea s.s. and for later flowering in one population of the late‐flowering G. densiflora . No divergent selection on floral morphology was detected, and there was no significant stabilizing selection on any trait in the two species. The results suggest ongoing adaptive differentiation of flowering phenology, strengthening this premating reproductive barrier between the two species. Synthesis : This study is among the first to test whether divergent selection on floral traits contribute to the maintenance of species differences between closely related plants. Phenological isolation confers a substantial potential for reproductive isolation, and divergent selection on flowering time can thus greatly influence reproductive isolation and adaptive differentiation. Abstract : We document divergent selection on flowering phenology in two closely related orchids. The results suggest ongoing adaptive differentiation, where selection is strengthening divergence in flowering phenology, an important premating reproductive barrier between the two species.