Pollinator-relevant floral traits impact bidirectional hybridisation in the orchid genus Gymnadenia

Authors:
Preprint
Publisher website
Google Scholar
Abstract
Reproductive isolation is mediated by ecological, phenotypic, and genetic barriers. Where such barriers are not upheld, hybridisation can occur, revealing insight about the formation of species. Here, we provide an integrative investigation of hybrid formation between the orchids Gymnadenia conopsea and G. rhellicani and potential isolating barriers in zones of overlap in the European Alps. We examine opportunities for hybridisation by quantifying hybrid frequency and pollinator assemblages of parent species. Next, we characterise floral phenotypes and genetic parentage of hybrids to examine how genetic inheritance of traits shapes ecological interactions, and thus fitness, of hybrids. We find that pollinator assemblages of parents overlap partially, consistent with observed rare hybrids (G. conopsea and G. rhellicani . No evidence of backcrossing or introgression was found, but direction of pollen transfer varied across sites. Additionally, hybrids were heterozygous for parental alleles at two loci impacting anthocyanin production, suggesting hybrids’ intermediate floral colour reflects inheritance of these alleles. Finally, we find little support that ploidy variation or hybrid seed infertility explains the absence of advanced generations of hybrids. Thus, we suggest that floral isolation represents an important isolating mechanism between G. conopsea and G. rhellicani in limiting the formation of uncommon, unfit hybrids and shaping species boundaries.
Funding Information
  • EU SP7 PLANT FELLOWS (GA-2010-267243)
  • Claraz Schenkung Zurich
  • Schweizerischer Nationalfonds zur Förderung der Wissenschaftlichen Forschung (31003A_155943)
  • Royal Society (RGS\R1\211279)
  • Biotechnology and Biological Sciences Research Council (BB/P013511/1)
  • Biotechnology and Biological Sciences Research Council (BB/X01102X/1)
  • Biotechnology and Biological Sciences Research Council (BB/X01097X/1)

This publication has 81 references indexed in Scilit: