BARBER1, JANET C.*, JAVIER FRANCISCO-ORTEGA2, ARNOLDO SANTOS-GUERRA3, AND ROBERT K. JANSEN1. 1Section of Integrative Biology, School of Biological Sciences, University of Texas, Austin, TX 78712; 2Dept. of Biological Sciences, Florida International University, University Park, Miami, FL 33199; 3Jardín de Aclimatación de La Orotava, Puerto de la Cruz, Tenerife, Canary Islands, E-38400, Spain. - Evolution of Sideritis L. (Lamiaceae) in Macaronesia based on an analysis of chloroplast and nuclear datasets.
In an earlier study, we used a chloroplast DNA restriction site
approach to elucidate evolutionary patterns within Sideritis L.
subgenus Marrubiastrum (Lamiaceae). This assemblage of 24
species comprises one of the largest endemic groups in Macaronesia.
The subgenus contains a wide array of life forms which are found in
all ecological zones present in the Macaronesian archipelagos of
Madeira and the Canary Islands. A unique characteristic of the group
is its high level of aneuploidy, a feature rare in oceanic island
plants. We undertook a second analysis of the insular taxa using
sequences of the internal transcribed spacers (ITS) of nuclear
ribosomal DNA in order to test the patterns revealed by the
chloroplast phylogeny. Placement of several taxa in the earlier cpDNA
RFLP analysis suggested that hybridization may have been important in
the evolution of the group. Populations of S.
canariensis from three different islands appeared in three
different places in the cpDNA tree, and infraspecific taxa of two
other species were also split up. Our nuclear-based analysis provides
support for an interpretation of hybridization. The three populations
of S. canariensis are sister to each other in the ITS
phylogeny, as are the subspecies of S. cretica and
S. gomerae that were split in the chloroplast tree. If
incongruence between the two datasets is non-significant, we will
conduct rigorous analyses on a combined dataset to test the
hybridization hypothesis and to further characterize evolutionary
patterns within Macaronesian Sideritis.
Key words: cpDNA RFLP, ITS, Lamiaceae, Macaronesia, Sideritis