Journal
AMERICAN JOURNAL OF BOTANY
Volume 100, Issue 3, Pages 496-508Publisher
WILEY
DOI: 10.3732/ajb.1200275
Keywords
habitat differentiation; Heuchera; minority cytotype exclusion; niche; plant polyploidy; Saxifragaceae; species distribution modeling
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Funding
- Ruth Meyer Summer Scholarship
- Renee Crown Honors Wise-Marcus Award
- National Science Foundation [DEB 0743101]
- U.S. Department of Homeland Security
- U.S. Department of Agriculture through NSF [EF-0832858]
- University of Tennessee, Knoxville
- Direct For Biological Sciences
- Div Of Biological Infrastructure [0832858] Funding Source: National Science Foundation
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Premise of the study: Polyploidization is a key factor involved in the diversification of plants. Although polyploids are commonly found, there remains controversy on the mechanisms that lead to their successful establishment. One major problem that has been identified is that newly formed polyploids lack mates of the appropriate ploidy level and may experience severely reduced fertility due to nonproductive intercytotype crosses. Niche differentiation has been proposed as a primary mechanism that can alleviate this reproductive disadvantage and facilitate polyploid establishment. Here we test whether the establishment of tetraploid cytotypes of Heuchera cylindrica (Saxifragaceae) is consistent with climatic niche differentiation. Methods: We use a combination of field surveys, flow cytometry and species distribution models to: (1) examine the distribution of diploid and tetraploid cytotypes; and (2) determine whether tetraploid Heuchera cylindrica occupy climates that differ from those of its diploid progenitors. Key results: The geographic distributions of diploid and tetraploid cytotypes are largely allopatric as an extensive survey of 636 plants from 43 locations failed to detect any populations with both cytotypes. Although diploids and tetraploids occur in different geographic areas, polyploid Heuchera cylindrica occur almost exclusively in environments that are predicted to be suitable to diploid populations. Conclusions: Climatic niche differentiation does not explain the geographic distribution of tetraploid Heuchera cylindrica. We propose instead that tetraploid lineages were able to establish by taking advantage of glacial retreat and expanding into previously unoccupied sites.
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