Holocene climate change promoted allopatric divergence and explains the current disjunct geographic distribution of theOphrys aveyronensisspecies complex (Orchidaceae)

Abstract

AbstractSpecies with disjunct geographic distributions provide natural opportunities to investigate recent or incipient allopatric divergence. Although not rare, many of the cases observed result from successful colonization from a historical to a new range through dispersal or human-induced introduction which make the underlying eco-evolutionary processes sometimes difficult to decipher. TheOphrys aveyronensisspecies complex presents a disjunct geographic distribution with two ranges currently separated by 600 km on both sides of the Pyrenees Mountains. To uncover the causes of such intriguing biogeographic pattern, we combined population genomics and Ecological Niche Modelling approaches. Population genomic data show that all the populations studied display similar patterns of genetic diversity and dramatic decrease in effective size. We found significant genetic differentiation between the two ranges of theO. aveyronensisspecies complex. Our results support a very recent divergence (ca.1500 generations ago). Ecological Niche Modelling results further indicate that the disjunct geographic distribution of theO. aveyronensisspecies complex is consistent with a range split of a broad ancestral range, contraction and shifts in opposite directions in response to climate warming during the Holocene. The congruence of both the results of population genomics and ENM approaches demonstrates that continental allopatric divergence is involved in theOphrysadaptive radiation. TheO. aveyronensiscomplex is a promising candidate to study the onset of reproductive isolation immediately following an initial stage of geographic separation.