Integration of Spatial and Ecological Data in Evolutionary Studies
Miller, Allison , Knouft, Jason .
Characterizing the environmental niches of widespread tree species in North America: ecological variation in the hickory and pecan genus (Carya).
Within some tree genera, distinct species persist across broad, overlapping geographic areas despite extensive interspecific gene flow. Genetic analyses have revealed minimal population structure and high levels of genetic variation within tree species, suggesting that various aspects of tree life histories (wind pollinated obligate outcrossers with long generation times, copious reproductive output, and large effective population sizes) influence spatial patterns of variation. However, even with ongoing hybridization, many wide-ranging tree species appear to remain distinct ecologically. In this study, we investigate the climatic characteristics of the environmental niches of North American pecan and hickory species (Carya, Juglandaceae). Carya is monophyletic in North America and comprises two sections: section Apocarya (N = 4 species) and section Carya (N = 9 species). Georeferenced locality data were used in conjunction with GIS data layers to quantify and compare ecological attributes of the geographic distributions of the thirteen North American Carya species. We examine two main null hypotheses: 1) climatic factors characterizing the distributions of North American Carya species do not differ, and 2) environmental niches are not conserved within sections of Carya. Locality data (6,440 localities) and 15 GIS layers describing precipitation and temperature were used to characterize the environmental niches for 13 species. Preliminary results indicate that all environmental variables differed significantly among species; nine of 15 environmental variables differed significantly between section Apocarya and section Carya. A principal components analysis explained >80% of the variance in environmental data; a MANOVA of principal components scores indicated that sections Apocarya and Carya differed significantly. Principal component scores were used to assess environmental niche overlap between species within and among sections. These data suggest that the environmental niches of North American Carya species, despite persistent interspecific hybridization, are relatively distinct and appear to be conserved evolutionarily.
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1 - Saint Louis University, Biology, 3507 Laclede Avenue, St. Louis, MO, 63103, USA
Presentation Type: Symposium or Colloquium Presentation
Location: Stevens 2/Hilton
Date: Wednesday, July 11th, 2007
Time: 10:15 AM