TY - JOUR
T1 - The role of hybridization during ecological divergence of southwestern white pine (Pinus strobiformis) and limber pine (P. flexilis)
AU - Menon, Mitra
AU - Bagley, Justin C.
AU - Friedline, Christopher J.
AU - Whipple, Amy V.
AU - Schoettle, Anna W.
AU - Leal-Sàenz, Alejandro
AU - Wehenkel, Christian
AU - Molina-Freaner, Francisco
AU - Flores-Rentería, Lluvia
AU - Gonzalez-Elizondo, M. Socorro
AU - Sniezko, Richard A.
AU - Cushman, Samuel A.
AU - Waring, Kristen M.
AU - Eckert, Andrew J.
N1 - Publisher Copyright:
© 2018 John Wiley & Sons Ltd
PY - 2018/3
Y1 - 2018/3
N2 - Interactions between extrinsic factors, such as disruptive selection and intrinsic factors, such as genetic incompatibilities among loci, often contribute to the maintenance of species boundaries. The relative roles of these factors in the establishment of reproductive isolation can be examined using species pairs characterized by gene flow throughout their divergence history. We investigated the process of speciation and the maintenance of species boundaries between Pinus strobiformis and Pinus flexilis. Utilizing ecological niche modelling, demographic modelling and genomic cline analyses, we illustrated a divergence history with continuous gene flow. Our results supported an abundance of advanced generation hybrids and a lack of loci exhibiting steep transition in allele frequency across the hybrid zone. Additionally, we found evidence for climate-associated variation in the hybrid index and niche divergence between parental species and the hybrid zone. These results are consistent with extrinsic factors, such as climate, being an important isolating mechanism. A build-up of intrinsic incompatibilities and of coadapted gene complexes is also apparent, although these appear to be in the earliest stages of development. This supports previous work in coniferous species demonstrating the importance of extrinsic factors in facilitating speciation. Overall, our findings lend support to the hypothesis that varying strength and direction of selection pressures across the long lifespans of conifers, in combination with their other life history traits, delays the evolution of strong intrinsic incompatibilities.
AB - Interactions between extrinsic factors, such as disruptive selection and intrinsic factors, such as genetic incompatibilities among loci, often contribute to the maintenance of species boundaries. The relative roles of these factors in the establishment of reproductive isolation can be examined using species pairs characterized by gene flow throughout their divergence history. We investigated the process of speciation and the maintenance of species boundaries between Pinus strobiformis and Pinus flexilis. Utilizing ecological niche modelling, demographic modelling and genomic cline analyses, we illustrated a divergence history with continuous gene flow. Our results supported an abundance of advanced generation hybrids and a lack of loci exhibiting steep transition in allele frequency across the hybrid zone. Additionally, we found evidence for climate-associated variation in the hybrid index and niche divergence between parental species and the hybrid zone. These results are consistent with extrinsic factors, such as climate, being an important isolating mechanism. A build-up of intrinsic incompatibilities and of coadapted gene complexes is also apparent, although these appear to be in the earliest stages of development. This supports previous work in coniferous species demonstrating the importance of extrinsic factors in facilitating speciation. Overall, our findings lend support to the hypothesis that varying strength and direction of selection pressures across the long lifespans of conifers, in combination with their other life history traits, delays the evolution of strong intrinsic incompatibilities.
KW - conifers
KW - ecological speciation
KW - extrinsic barriers
KW - hybrid zone
KW - introgression
KW - population genomics
UR - http://www.scopus.com/inward/record.url?scp=85045087350&partnerID=8YFLogxK
U2 - 10.1111/mec.14505
DO - 10.1111/mec.14505
M3 - Artículo
C2 - 29411444
SN - 0962-1083
VL - 27
SP - 1245
EP - 1260
JO - Molecular Ecology
JF - Molecular Ecology
IS - 5
ER -