LOWREY, TIMOTHY K.1*, RICHARD WHITKUS2, JOY AVRITT1, and CHRISTOPHER J. QUINN3. 1Department of Biology, University of New Mexico, Albuquerque, NM 87120; 2Department of Biology, Sonoma State University, Rohnert Park, CA 94928; 3School of Biological Science, University of New South Wales, Sydney, NSW 2052, Australia. - Sex expression, compatibility and crossing relationships in the Vittadinia group (Asteraceae).
The Vittadinia group is comprised of 11 genera in the
Astereae tribe. Most members of the Vittadinia group
occur on the continent of Australia and several of the larger genera
extend their distribution across the Pacific to Hawaii and the Cook
Islands. Recent studies of the phylogenetic relationships of the
genera have revealed marked homoplasy in molecular data and in
morphological features, particularly those associated with the
breeding system. Past inter-generic hybridization events could
explain, in part, the considerable degree of homoplasy observed. Here
we report results of greenhouse studies on variation in sex
expression, self-incompatibility and infrageneric/intergeneric
cross-compatibility, in five of the largest genera: Vittadinia,
Tetramolopium, Minuria, Camptacra, and
Peripleura. Minuria, Camptacra, and one section
of Tetramolopium are monoecious while Vittadinia,
Peripleura, and the remaining two sections of
Tetramolopium are gynomonoecious. Self-incompatibility is
strongly correlated with monoecy. Phylogenetic analysis indicates that
monoecy has been gained and lost more than once, and hence so has
self-incompatibility. Crossing studies readily obtained interspecific
hybrids in all five genera with high pollen fertility in most cases.
Intergeneric hybrids resulted among a majority of the attempted
combinations. Intergeneric hybrids were obtained between Hawaiian and
Australian taxa and possessed surprisingly high pollen fertilities.
Therefore, ancient intergeneric hybridization may well have had a role
in generating diversity in this group.
Key words: Asteraceae, hybridization, monoecy, self-incompatibility, Tetramolopium, Vittadinia