WHITSON, MARY KATHRYN. Biology Department, Duke University, Box 90338, Durham, NC 27706. - Untangling Physalis (Solanaceae) from the physaloids: two-gene phylogeny vindicates the splitters.
In Physalis, yellow flowers with darkly spotted throats give
rise to berries which are completely enveloped by inflated,
lantern-like calyces. Despite this distinctive morphology, taxonomists
have had difficulty delimiting the genus, and little is known about
the phylogenetic relationships of the 75+ species of Physalis.
DNA sequence data from a segment of the nuclear gene waxy (600
bp) and the ITS region of the nrDNA (800 bp) was used to generate a
phylogeny of Physalis. Taxon sampling included 30 species of
Physalis plus related physaloid genera. The data sets were
analyzed simultaneously using maximum parsimony as the optimality
criterion. All characters had equal weights and gaps were treated as
missing data. Trees were rooted using the outgroup Witheringia.
As currently defined, Physalis is polyphyletic. While the
morphologically typical species form a strongly supported clade, P.
alkekengi (white flowers), P. carpenteri (clustered
flowers) and P. microphysa (deeply lobed calyx) are separated
from this clade by a grade of physaloid genera including
Quincula, Physalis subgenus Physalodendron (P.
melanocystis and P. arborescens), Oryctes and
Chamaesaracha. P. alkekengi, the type of Physalis
and its only Eurasian member, is not included in the main
Physalis clade. That clade consists of Margaranthus (in
fruit, indistinguishable from Physalis) and Physalis
species with solitary yellow flowers and highly inflated calyces.
Other than section Viscosa (predominantly North American), the
sections of Physalis do not appear to be monophyletic, though a
rhizomatous perennial clade is formed by section Viscosa and
the U.S. species of section Lanceolatae. In general, the
phylogeny supports the physaloid genera as being distinct from
Physalis, but does not support the monophyly of sections within
the genus. However, further sampling within Physalis may
suggest ways in which the infrageneric classification can be adjusted
to recognize both monophyletic and morphologically distinctive units.
Key words: ITS, phylogeny, Physalis, physaloid, Solanaceae, waxy