WHITSON, MARY KATHRYN. Department of Botany, Box 90338, Duke University, Durham, NC 27708. - Does hybridization play a role in the morphological similarity between Physalis arenicola (Solanaceae) and a co-occurring, closely related species?
Various workers have postulated that members of Physalis
section Lanceolatae naturally hybridize. Successful artificial
hybridizations have been accomplished, but documented cases of natural
hybridization are rare. In areas of sympatry, different habitat
preferences help keep species of the Lanceolatae separated. In
north Florida, however, populations of P. arenicola and an
undescribed species of the Lanceolatae co-occur along the
bluffs of the Apalachicola river. This provides a unique opportunity
to address the question of natural hybridization among species of the
Lanceolatae. Physalis arenicola occurs throughout
Florida, favoring sandy, open areas. The undescribed species grows on
wooded river bluffs, and is apparently limited to a two county region.
Vegetatively, these taxa are quite similar, though P. arenicola
encompasses a broader range of morphological variation. The two taxa
are best distinguished by differences in rhizome morphology. Is the
vegetative similarity between these species due to the fact that they
are closely related and still share plesiomorphic characters, or is
there some gene flow between them? Leaf material was collected
from multiple individuals in the mixed species populations, and from
isolated populations of each taxon, including individuals of P.
arenicola from southern Florida, where the river bluff taxon does
not occur. Isozyme data was generated using the following 12 enzyme
systems: ACO, ALD, GDH, G3PDH, IDH, MDH, ME, PGI, PGM, PRX, SKD, and
TPI. Within P. arenicola, ACO, GDH, ME, PGI, PRX and TPI are
polymorphic. IDH is variable within both species. IDH also shows
species specific variation, as do MDH and SKD. Each species has a
unique ITS sequence. Eight characters differentiate these
sequences, including an 8 bp indel. The amount of ITS sequence
variation between these species is similar to that between sequences
of other closely related species within the Lanceolatae.
Key words: Florida, hybrid, isozyme, Physalis, Solanaceae, sympatry