SYTSMA , KENNETH JAY , SPALINK, DANIEL .
Examining biogeographic and climatic niche evolution in Clarkia (Onagraceae) from the California Floristic Province.
The genus Clarkia (Onagraceae), primarily restricted to the California Floristic Province (CFP) with a few taxa extending into the Pacific Northwest and one, Clarkia tenella, occurring in Mediterranean-climate regions of Chile and Argentina, has emerged as an important model system for the study of plant evolution, particularly mechanisms of plant speciation and breeding system diversification. As presently understood, Clarkia includes 42 species segregated into eight mostly diploid sections. A phylogenetic framework for Clarkia based on both chloroplast and nuclear DNA is now emerging and is providing the basis for more detailed studies of its remarkable radiation. We present a two-pronged analysis of the diversification of Clarkia in space (ancestral area reconstruction-AAR) and niche (ecological niche modeling) using time-constrained phylogeny. First, we scored species (and subspecies is some cases) for presence/absence in the main CFP regions. Dispersal-extinction-cladogenesis (DEC) models, with or without the "j" parameter (cladogenetic jump dispersals), were used to explore AAR in the R package "BioGeoBEARS". The Sierra Nevada Region appears to be a key component of the early diversification of the genus. Unlike most other reported examples using "BioGeoBEARS", invoking cladogenetic jump dispersal does NOT significantly increase the likelihood of the model, thus perhaps indicating that speciation in Clarkia occurs far more often with allopatric vicariant events than island-like founder dispersals. Second, we obtained geo-referenced CFP-centered Clarkia specimens and a suite of climatic and soil variables to develop ecological niche models for these species using the program MAXENT. We conduct both multivariate and univariate analyses of these niche parameters in a phylogenetic context. We explore phylogenetic signal, significant niche shifts, and correlative evolution using the R packages "surface," "caper," "ace," and "picante." There is strong ecological and phylogenetic correlation among several of the climatic variables. Some of the strongest niche shifts are seen with (1) precipitation in warmest month, (2) mean temperature, and (3) elevation. These Clarkia results are discussed in the context of the timing of geological, climatic, and vegetation shifts in the CFP.
1 - University Of Wisconsin, Department Of Botany, Birge Hall, 430 Lincoln Drive, Madison, WI, 53706, USA
Presentation Type: Oral Paper:Papers for Topics
Candidate for Awards:None