ELISENS, WAYNE*, MIA MOLVRAY, PAUL KORES, AND CLAUDE DEPAMPHILIS. Department of Botany & Microbiology, University of Oklahoma, Norman, OK 73019 and Department of Biology, Pennsylvania State University, University Park, PA 16802. - ITS sequence variation among climbing snapdragons (Veronicaceae): implications for delimiting genera and evaluating crossing data.
The 20 North American species comprising subtribe Maurandyinae have
been treated in four to seven genera and are noteworthy for exhibiting
a diversity of floral morphologies and wide interspecific
compatibilities in artificial crosses. To test taxonomic hypotheses
and to evaluate inferences about genetic relatedness based on crossing
and interfertility data, 15 ingroup and four outgroup species were
analyzed for nucleotide variation among nrDNA ITS sequences.
Parsimony analyses result in a high level of support for monophyly of
the group and sister group status for the SW European and
Mediterranean genera Asarina and Cymbalaria. Within the
Maurandyinae, two main clades with moderate levels of support are
delineated: Maurandya + Epixiphium +
Holmgrenanthe and Mabrya + Lophospermum.
Biogeographic analyses suggest a basal diversification in arid
habitats with a subsequent radiation into more mesic habitats in
southern Mexico and Guatemala. The frequently segregated monotypic
genera Epixiphium and Holmgrenanthe are characterized by
long branch lengths and the lowest indices of crossability in the
group. Species previously segregated in Mabrya appear
paraphyletic, supporting their merger in an expanded
Lophospermum and consistent with their moderate levels of
‘intergeneric’ hybrid fertilities. The highest indices of
crossability and interfertility are found in species of
Maurandya and Lophospermum that have the closest
topological placement on ITS trees.
Key words: crossing data, generic delimitation, ITS, Maurandyinae, Veronicaceae