BARBER, JANET C.*, JAVIER FRANCISCO-ORTEGA, ARNOLDO SANTOS-GUERRA, KATHRYN TURNER, AND ROBERT K. JANSEN. Section of Integrative Biology, School of Biological Sciences, University of Texas, Austin, TX 78712; Dept. of Biological Sciences, Florida International University, University Park, FL 33199; Jardin de Aclimatacion de La Orotava, Puerto de la Cruz, Tenerife, Canary Islands, E-38400, Spain. - Origin of Macaronesian Sideritis L. (Lamiaceae) inferred from sequences of two non-coding regions of chloroplast DNA.
Sideritis L. (Lamiaceae) comprises approximately 150 species of
annuals and perennials distributed chiefly in the Mediterranean
region. Twenty-four of these are woody perennials endemic to the
Macaronesian archipelagos of Madeira and the Canary Islands. An
earlier study used a chloroplast DNA restriction site approach to
elucidate the pattern of evolution within and among the islands. In
an effort to determine the continental origin of the insular group, we
sequenced the trnL intron and the trnT-trnL
intergenic spacer of the chloroplast genome. Sampling included seven
island taxa, drawn from all three sections of the Macaronesian
subgenus Marrubiastrum, and 29 continental taxa representing
the remaining four sections that comprise the continental subgenus
Sideritis. The two perennial continental sections form
strongly supported clades, but there is little resolution within the
groups. While the Macaronesian subgenus Marrubiastrum is
monophyletic, its sections are not; this finding agrees with the
results of the earlier cpDNA RFLP study. The cpDNA sequence data
identified Sideritis cossoniana, an annual species from
Morocco, as the closest continental relative of the Macaronesian
group. Preliminary analyses of ITS sequences for the same taxa
corroborate this relationship, which contrasts with the hypothesis of
earlier workers who suggested that the insular taxa were most closely
related to eastern Mediterranean species of the genus. This study
provides further evidence for the evolution of woodiness in insular
taxa descended from herbaceous continental ancestors.
Key words: biogeography, Lamiaceae, Macaronesia, Sideritis