Am J Bot. 2012 Apr;99(4):655-62. doi: 10.3732/ajb.1100466. Epub 2012 Mar 20.
- 1
- University of California Davis and Center for Population Biology, One Shields Avenue, Davis, California 95616, USA.
Abstract
PREMISE OF THE STUDY:
Polyploids
are often hypothesized to have distinct and broader niches than their
diploid progenitors. Differences in geographic distributions between
diploid and polyploids are frequently used to infer niche
differentiation and increased breadth, but they are seldom used to test
these hypotheses explicitly.
METHODS:
Niche overlap and breadth were compared for diploids, tetraploids, and hexaploids of three taxa in the Claytonia perfoliata complex (C. parviflora, C. perfoliata,
and C. rubra) with the use of species distribution models. Resampling
and randomization approaches were used to test hypotheses of niche
differentiation, breadth, and conservatism.
KEY RESULTS:
Niche
differentiation was detected between polyploid and diploid cytotypes
assigned to the same taxon (e.g., C. parviflora 2× vs. 4×) but not
between hexaploids and tetraploids within a taxon (e.g., C. parviflora
4× vs. 6×). Individual hexaploid cytotypes had broader ecological niches
than individual diploid cytotypes. However, as a group the three
hexaploid taxa did not exceed the combined niche breadth of the three
diploids, suggesting that polyploidy does not result in transgressive
niche breadth for this group. Niche overlap was lowest among diploids
and was highest among the three hexaploid cytotypes, consistent with
introgression associated with polyploidy resulting in greater ecological
similarity. Although cytotypes possessed nonidentical niches, after
accounting for environmental differences among ranges, cytotypes were
more similar than expected, suggesting niche conservatism and similar
responses to environmental characteristics.
CONCLUSIONS:
These
results suggest that polyploids occupy distinct and broader niches
relative to diploids but that cytotypes also share fundamentally similar
responses to environmental variation across ploidy levels.
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