Sideroxylon section Frigoricola (Sapotaceae) comprises eight species of shrubs or small trees endemic to temperate North America. These eight species are Sideroxylon alachuense, S. lanuginosum, S. lycioides, S. macrocarpum, S. reclinatum, S. rufohirtum, S. tenax, and S. thornei. Morphologically, these taxa are distinguished from their tropical congeners by having a combination of fascicled leaves, conspicuously reticulate tertiary venation, short styles, small fruits, and a bipartite hilum scar. A molecular phylogenetic analysis including these eight species plus 17 selected tropical relatives was conducted using nuclear ITS sequence data. The results confirm the monophyly of the group, which is here given recognition at sectional rank. Relationships within the group were investigated based on detailed observations of morphological characters, as well as molecular analysis of the nuclear ITS DNA region, and five chloroplast DNA regions. Morphology-based cladistic analysis yielded a wellresolved phylogeny of the group. Several subclades are evident within the group: the S. lycioides + S. thornei clade, the S. tenax clade (i.e., S. tenax + S. alachuense ), the S. lanuginosum clade (i.e., S. lanuginosum subspp. lanuginosum, rigidum, and albicans), the S. reclinatum clade (i.e., S. reclinatum subspp. reclinatum and austrofloridense), and the S. rufohirtum + S. macrocarpum clade. The S. reclinatum clade plus the S. rufohirtum + S. macrocarpum clade form a clade, i.e., the S. reclinatum complex. DNA analysis suggested alternative groupings, but sequence divergence is minimal for the regions compared. Species of Sideroxylon section Frigoricola are endemic to an area encompassing much of the southeastern United States and the northern tier of states in Mexico, most of these species being concentrated on the North American Coastal Plain from Texas through the Carolinas, an area recently recognized as a global hotspot of biodiversity and endemism. Florida is the center of diversity for the group. Sideroxylon section Frigoricola represents a recent radiation whose species are morphologically distinct and apparently eco-geographically differentiated. A formal taxonomic revision of the section is presented.
|Advisor:||Judd, Walter S.|
|Commitee:||Smith, Nigel, Soltis, Pamela S., Williams, Norris H.|
|School:||University of Florida|
|School Location:||United States -- Florida|
|Source:||DAI-B 79/04(E), Dissertation Abstracts International|
|Subjects:||Botany, Systematic biology|
|Keywords:||Florida, endemic, taxonomic revision|
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