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Postmating barriers to hybridization between an island’s native eucalypts and an introduced congener
journal contributionposted on 2023-05-18, 18:39 authored by Larcombe, MJ, Barbour, RC, Rebecca JonesRebecca Jones, Rene VaillancourtRene Vaillancourt, Bradley PottsBradley Potts
We evaluate postmating barriers to hybridization between an exotic eucalypt and a group of native congeners on the island of Tasmania. We aimed to better understand the basis of reproductive isolation between the species, glean insights into the evolution of isolating mechanisms, and inform genetic risk management. Compatibility between the exotic plantation species Eucalyptus nitens (pollen parent) and 18 native Tasmanian taxa was assayed using experimental crossing for 17 taxa (13,458 flowers pollinated to produce 1058 female × male cross combinations), and previous data for one species. Compatibility was assessed in terms of F1 hybrid production, as well as F1 hybrid survival and growth after 5 years. This data was combined with measurements of style length, and genetic distance from E. nitens to each maternal species, in order to determine the importance of a sequence of prezygotic and postzygotic barriers. We found that the early-acting barrier of style length (prezygotic) had the strongest isolating effect, while later-acting (postzygotic) barriers, affecting early-age growth and survival, contributed little to reproductive isolation. Style length alone explained 46 % of the variation in hybridization rate. Conversely, there was no significant relationship between genetic distance and prezygotic or postzygotic compatibility in these closely related species. This pattern is consistent with selection driving the rapid evolution of prezygotic barriers, while drift-like-processes lead to the more gradual evolution of intrinsic barriers. Although other premating and postmating barriers clearly contribute, our results highlight the important role of early-acting postmating barriers in preventing gene flow from exotic E. nitens plantations.
Publication titleTree Genetics and Genomes
Department/SchoolSchool of Natural Sciences
Place of publicationGermany
Rights statementCopyright 2016 Springer Verlag