Systematics Section / ASPT
Barber, Janet C. , Finch, Courtney , Santos-Guerra, Arnoldo , Francisco-Ortega, Javier , Jansen, Robert K. .
A comparison of phylogenies based upon independent nuclear and chloroplast datasets for Sideritis L. (Lamiaceae: Lamioideae).
The genus Sideritis comprises ca. 150 spp. of annual and perennial plants with a largely circum-Mediterranean distribution. Our studies of this genus have included multiple genetic markers and extensive sampling of continental relatives. One study used chloroplast restriction site (RFLP) data to investigate evolution within the Macaronesian subgenus. A second used ITS data and expanded sampling to include 25 continental taxa. The major objective of that study was to determine the origin of the Macaronesian group; thus, it included only seven island taxa. Although these earlier studies investigated phylogenetic relationships and evolution within the genus, they lacked parallel sampling. We have completed an ITS sequence dataset for 55 taxa of Sideritis (plus two outgroups); this represents complete sampling for all taxa included in the earlier studies. Due to the difficulties of incorporating new data into an existing RFLP dataset, we have instead completed a cpDNA sequence dataset with sampling that corresponds to the nuclear ribosomal ITS dataset. The two chloroplast phylogenies (RFLP and sequence data) are entirely congruent, based on parsimony 70% bootstrap values. However, a number of clades with lower bootstrap support (61-65%) in the cpDNA sequence phylogeny have high posterior probabilities (.95-1.00) in a Bayesian consensus. Some of these clades conflict with the RFLP phylogeny. Most surprising of the conflicts is the sister relationship between the two subspecies of S. soluta; this relationship is unique to this dataset. Comparisons of the cpDNA phylogenies to the nuclear ITS phylogeny highlight several instances of potential cytoplasmic introgression. We have begun chromosomal studies that we hope will allow us to identify putative hybrids and to determine whether chromosomal changes have contributed to speciation, particularly within the Macaronesian subgenus. Preliminary fluorescence in situ (FISH) experiments suggest that Robertsonian changes (i.e. chromosome fission/fusion) have played a role in the evolution of Sideritis.
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1 - Saint Louis University, Department of Biology, 3507 Laclede Avenue, St Louis, Missouri, 63103-2010, USA
2 - Jardín de Aclimatación de La Orotava, Puerto de la Cruz, Canary Islands, Tenerife, , Spain
3 - Dept. Biological Sciences, Florida International University, Fairchild Tropical Botanic Garden, Miami, Florida, 33199, USA
4 - University of Texas Austin, Section of Integrative Biology, 1 University Station, A6700, Austin, Texas, 78712-7640, USA
Presentation Type: Poster
Location: Salon C, D & E - Gov Ballroom/Hilton
Date: Tuesday, August 16th, 2005
Time: 12:30 PM