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Direct vs. indirect effects of whole‐genome duplication on prezygotic isolation in Chamerion angustifolium : Implications for rapid speciation
Author(s) -
Husband Brian C.,
Baldwin Sarah J.,
Sabara Holly A.
Publication year - 2016
Publication title -
american journal of botany
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.218
H-Index - 151
eISSN - 1537-2197
pISSN - 0002-9122
DOI - 10.3732/ajb.1600097
Subject(s) - reproductive isolation , biology , polyploid , ploidy , gene duplication , genome , evolutionary biology , genetics , gene , population , demography , sociology
PREMISE OF THE STUDY: The depiction of polyploid speciation as instantaneous implies that strong prezygotic and postzygotic isolation form as a direct result of whole‐genome duplication. However, the direct vs. indirect contributions of genome duplication to phenotypic divergence and prezygotic isolation are rarely quantified across multiple reproductive barriers. METHODS: We compared the phenotypic differences between diploid and both naturally occurring and synthesized tetraploids (neotetraploids) of the plant Chamerion angustifolium . Using this information and additional published values for this species, we compared the magnitude of isolation (ecological, flowering, pollinator, and gametic) between diploids and natural‐occurring tetraploids to that between diploids and neotetraploids. KEY RESULTS: Differences among ploidy cytotypes were observed for eight of 12 vegetative and reproductive traits measured. Neotetraploids resembled diploids but differed from natural tetraploids with respect to four traits, including flowering time and plant height. Diploid–neotetraploid (2 x –4 x neo ) experimental arrays exhibited lower pollinator fidelity to cytotype and seed set compared with 2 x –4 x nat arrays. Based on these results and published evidence, reproductive isolation between diploids and neotetraploids across all four life stages averaged 0.48 and deviated significantly from that between diploids and natural tetraploids (RI = 0.96). CONCLUSIONS: Genome duplication causes phenotypic shifts and contributes directly to prezygotic isolation for some barriers (gametic isolation) but cannot account for the cumulative isolation from diploids observed in natural tetraploids. Therefore, conditions for species formation through genome duplication are not necessarily instantaneous and selection to strengthen prezygotic barriers in young polyploids is critical for the establishment of polyploid species in sympatry.