한빛사 논문
Jae Young Choi1, Michael Purugganan1,2, and Elizabeth A. Stacy3,*
1 Center for Genomics and Systems Biology, Department of Biology, 12 Waverly Place, New York University, New York, NY USA
2 Center for Genomics and Systems Biology, NYU Abu Dhabi Research Institute, New York University Abu Dhabi, Saadiyat Island, Abu Dhabi, United Arab Emirates
3 School of Life Sciences, University of Nevada Las Vegas, 4505 S. Maryland Parkway, Las Vegas, Nevada USA
*Corresponding author : Elizabeth A. Stacy
Abstract
A long-standing goal of evolutionary biology is to understand the mechanisms underlying the formation of species. Of particular interest is whether or not speciation can occur in the presence of gene flow and without a period of physical isolation. Here, we investigated this process within Hawaiian Metrosideros, a hyper-variable and highly dispersible woody species complex that dominates the Hawaiian Islands in continuous stands. Specifically, we investigated the origin of Metrosideros polymorpha var. newellii (newellii), a riparian ecotype endemic to Hawaii Island that is purportedly derived from the archipelago-wide M. polymorpha var. glaberrima (glaberrima). Disruptive selection across a sharp forest-riparian ecotone contributes to the isolation of these varieties and is a likely driver of newellii’s origin. We examined genome-wide variation of 42 trees from Hawaii Island and older islands. Results revealed a split between glaberrima and newellii within the past 0.3-1.2 million years. Admixture was extensive between lineages within Hawaii Island and between islands, but introgression from populations on older islands (i.e. secondary gene flow) did not appear to contribute to the emergence of newellii. In contrast, recurrent gene flow (i.e. primary gene flow) between glaberrima and newellii contributed to the formation of genomic islands of elevated absolute and relative divergence. These regions were enriched for genes with regulatory functions as well as for signals of positive selection, especially in newellii, consistent with divergent selection underlying their formation. In sum, our results support riparian newellii as a rare case of incipient ecological speciation with primary gene flow in trees.
Keywords : Metrosideros, sympatric speciation, ecological speciation, incipient speciation, gene flow, genomic islands of divergence
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