Ecological speciation in sympatric palms: 2. Pre- and post-zygotic isolation

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Title: Ecological speciation in sympatric palms: 2. Pre- and post-zygotic isolation
Authors: Hipperson, H
Dunning, LT
Baker, WJ
Butlin, RK
Hutton, I
Papadopulos, AST
Smadja, CM
Wilson, TC
Devaux, C
Savolainen, V
Item Type: Journal Article
Abstract: We evaluated reproductive isolation in two species of palms (Howea) that have evolved sympatrically on Lord Howe Island (LHI, Australia). We estimated the strength of some pre- and post-zygotic mechanisms in maintaining current species boundaries. We found that flowering time displacement between species is consistent across in and ex situ common gardens and is thus partly genetically determined. On LHI, pre-zygotic isolation due solely to flowering displacement was 97% for H. belmoreana and 80% for H. forsteriana; this asymmetry results from H. forsteriana flowering earlier than H. belmoreana and being protandrous. As expected, only a few hybrids (here confirmed by genotyping) at both juvenile and adult stages could be detected in two sites on LHI, in which the two species grow intermingled (The Far Flats) or adjacently (Transit Hill). Yet, the distribution of hybrids was different between sites. At Transit Hill we found no hybrid adult trees, but 13.5% of younger palms examined there were of late hybrid classes. In contrast we found four hybrid adult trees, mostly of late hybrid classes, and only one juvenile F1 hybrid in the Far Flats. This pattern indicates that selection acts against hybrids between the juvenile and adult stages. An in situ reciprocal seed transplant between volcanic and calcareous soils also shows that early fitness components (up to 36 months) were affected by species and soil. These results are indicative of divergent selection in reproductive isolation, although it does not solely explain the current distribution of the two species on LHI.
Issue Date: 20-Jul-2016
Date of Acceptance: 30-Jun-2016
ISSN: 1010-061X
Publisher: Wiley
Start Page: 2143
End Page: 2156
Journal / Book Title: Journal of Evolutionary Biology
Volume: 29
Issue: 11
Copyright Statement: © 2016 The Authors. Journal of Evolutionary Biology published by John Wiley & Sons Ltd on behalf of European Society for Evolutionary Biology. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.
Sponsor/Funder: Natural Environment Research Council (NERC)
Commission of the European Communities
The Leverhulme Trust
Funder's Grant Number: NE/M015742/1
Keywords: flowering
Evolutionary Biology
0603 Evolutionary Biology
0608 Zoology
Publication Status: Published
Appears in Collections:Faculty of Natural Sciences

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