WALLACE, ROBERT S.* AND DEBRA L. STANSBERRY. Department of Botany, Iowa State University, Ames, IA 50011. - Molecular phylogenetic appraisal of the genera Peniocereus and Nyctocereus (Cactaceae).
The relationship of the geophytic genus Peniocereus (Berger)
Br. &. R. to other groups of cacti has been controversial. Previous
authors have allied it with members of the Tribe Hylocereeae or to
members of the Tribe Echinocereeae, citing morphological similarities
with the Wilcoxia group of Echinocereus. Additonally,
recent treatments of the Cactaceae have subsumed the genus
Nyctocereus (Berger) Br. & R. within Peniocereus. Our
present studies of DNA sequences of the plastid rpl16 intron
have shown Peniocereus to be more closely allied with the
Pachycereinae subtribe of Tribe Pachycereeae. Furthermore, the
epiphytic species Deamia testudo, previously allied to
Selenicereus (Tribe Hylocereeae), was also found to be part of
this clade. The value of phylogenetic analyses of plastid
rpl16 intron sequences to establish a revised classification
for the Peniocereus-Nyctocereus clade is examined, particularly
with respect to morphological diversification in Mexican Pachycereeae.
With the inclusion of Deamia testudo in the Tribe
Pachycereeae, this new evidence provides an example of another
independent evolution of epiphytism in the Cactaceae, in addition to
the well-known examples in tribes Rhipsalideae and Hylocereeae.
Key words: Cactaceae, classification, molecular systematics, Nyctocereus , Peniocereus, phylogeny