BOGLER, DAVID J.1,2*, TIM RAWLINGS2, and JAVIER FRANCISCO-ORTEGA1,2. 1Fairchild Tropical Garden, Research Center, 11935 Old Cutler Road, Miami FL 33156; 2Florida International University, University Park Campus, Miami FL 33199. - Evolutionary relationships in Dasylirion (Nolinaceae): an assessment using AFLP markers.
Dasylirion is a genus of prickly-leaved, dioecious rosette
plants found in arid, hilly regions of the desert Southwest and
Mexico. Morphological and molecular data clearly indicate that
Dasylirion is closely related to Nolina,
Beaucarnea, and Calibanus, and these genera are often
treated as the family Nolinaceae. Dasylirion was recently
monographed and 17 species were recognized. Many of these species fit
the model of "semispecies" in which barriers to reproduction
are weak and hybrids are common. Species relationships are poorly
known, and probably reticulate. Molecular studies using several
markers have generally failed to reveal much variation in
Dasylirion, a situation common in long-lived, woody taxa. A
survey of chloroplast DNA restriction site variation indicated two
major groups, one clade of species in southern and central Mexico with
brushy leaf tips, and another clade containing the rest of the
species. Sequencing ITS rDNA failed to provide much additional
information. Recently, a study was made using the technique known as
amplified fragment length polymorphism (AFLP) to resolve species
relationships in Dasylirion. AFLP is widely used in population
level studies, paternity analysis, cultivar identification, and crop
breeding, but the limits of using the technique to compare more widely
divergent taxa are uncertain. We surveyed 36 samples of
Dasylirion using 21 primer pairs, which generated hundreds of
variable fragments. In general, the AFLP data supports the clades
indicated by the chloroplast DNA restriction site data, however
relationships within the major clades is highly dependent on screening
the data and methods of analysis. Strengths and weaknesses of using
AFLP markers in studies of this nature will be discussed.
Key words: AFLP, Dasylirion, DNA fingerprinting, Nolinaceae, phylogeny