Visger, Clayton J , Germain-Aubrey, Charlotte , SOLTIS, PAMELA S. , Soltis, Douglas E. .
Niche Divergence in Tolmiea (Saxifragaceae): using Ecological Niche Modeling to develop a testable hypothesis for a diploid-autotetraploid species pair.
Tolmiea (Saxifragaceae) represents one of the clearest examples of a natural autopolyploid system. The autotetraploid T. menziesii (2n = 28) occupies a range in the Pacific Northwest from central Oregon to Alaska, while the diploid T. diplomenziesii (2n = 14) is found from Northern California to central Oregon. For the tetraploid to have originally become established following formation, it must have overcome a minority cytotype disadvantage. Partly as a consequence of the traditional view that autoploids were evolutionary unimportant, the area of autopolyploid establishment and niche divergence have received little attention. Here we ask, can the non-overlapping ranges of T. menziesii and T. diplomenziesii be explained by niche divergence or do they favor the same ecological space, but stay geographically isolated due to other factors, such as drift? This study first uses ecological niche modeling to quantify the degree of niche overlap between T. menziesii and T. diplomenziesii, which can serve as evidence for niche differentiation. Second, an ordination-based approach is applied to evaluate where in climatic space the two species differ most. Models generated for T. menziesii and T. diplomenziesii display a low degree of overlap (Schoener’s D= 0.258), and a significant departure from the background similarity of their different ranges (P < 0.02). The principle component analysis of climatic space resulted in clusters of T. menziesii and T. diplomenziesii overlapping along one principal component (temperature related), and non-overlapping along the other princial component (precipitation related). This 2-step approach suggests that the two ploidal levels not only have divergent niche requirements, but also reveals that precipitation availability appears to correlate most strongly with this divergence. Future work will use these data to develop a common garden comparison of physiological response to variation in water availability.
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1 - University of Florida, Florida Museum of Natural History and Department of Biology, Gainesville, FL, 32611, United States
2 - University of Florida, Florida Museum of Natural History, PO Box 117800, Gainesville, FL, 32611, USA
Presentation Type: Oral Paper:Papers for Sections
Date: Tuesday, July 29th, 2014
Time: 2:15 PM
Candidate for Awards:Ecological Section Best Graduate Student Paper