Systematics Section / ASPT
Barber, Janet C. , Santos-Guerra, Arnoldo , Francisco-Ortega, Javier , Jansen, Robert K. .
Sideritis L. in Macaronesia: current knowledge and future perspectives.
The genus Sideritis contains ca. 150 spp. of annual and perennial plants with a largely circum-Mediterranean distribution. Our studies to date have focused on the 23 species comprising the endemic Macaronesian subgenus Marrubiastrum. A western Mediterranean origin and single introduction of the group to the islands was supported by phylogenies based on chloroplast and nuclear sequence data. Anomalous placement of several taxa in a separate cpDNA (RFLP) phylogeny suggested previously undetected hybridization; this phylogeny also implied a bimodal pattern of change in diploid chromosome number. Bayesian analyses of an expanded nuclear matrix support all earlier inferences with the exception of chromosomal evolution. Here, the pattern suggests an overall increase in diploid number within the island subgenus. This is an exceptional contrast to the decreasing trend predominant in angiosperm groups, as well as to the general rule of chromosomal stasis in island plants. Current markers lack resolution to sufficiently delineate the pattern of change at a finer scale, thwarting more definitive interpretation. We are pursuing new markers in an attempt to improve phylogenetic resolution for these species. In addition, we plan to initiate chromosomal studies employing modern cytogenetic techniques (e.g. FISH; GISH) that will allow us to investigate putative hybrids. Our ultimate goal is to determine whether chromosomal changes have contributed to speciation in this diverse group of island plants.
1 - Florida International University, Dept. of Biological Sciences, 11200 SW 8th St., Miami, Florida, 33199, USA
2 - Jardin de Aclimatacion de la Orotava, Calle Retama Numero 2, Puerto de la Cruz, Teneri, Canary Islands, E-38040, Spain
3 - University of Texas at Austin, Section of Integrative Biology, 1 Universiy Station, #A6700, Austin, Texas, 78712, USA
4 - Saint Louis University, Department of Biology, 3507 Laclede Avenue, St. Louis, Missouri, 63103, USA
Presentation Type: Paper
Location: Cottonwood A (Snowbird Center)
Date: Tuesday, August 3rd, 2004
Time: 11:00 AM