KEELING, STEPHANIE DIANA* and MARK E. MORT. Department of Ecology and Evolutionary Biology and Natural History Museum, University of Kansas, Lawrence, KS 66045-7534. - Mechanisms of asexual reproduction in Crassulaceae.
Asexual reproduction is an alternative method of reproduction employed
by numerous organisms. It has been speculated that asexual
reproduction is utilized by individuals that are particularly well
suited to a given environment, hence allowing for duplication of
individuals that will be successful in that habitat. Within plants
there is a wide variety of mechanisms of asexual reproduction, ranging
from apomixis (a form of agamospermy) in Poa pratensis to
plantlet formation in Kalanchoe diagremontiana. It is a common
means of reproduction in numerous angiosperm families. One angiosperm
family that displays numerous mechanisms of asexual reproduction is
Crassulaceae. Within this family alone there are examples of nodal
rooting in Crassula aquatica, plantlet formation from
meristematic tissue in crenations of leaf margins in Bryophylum
and Kalanchoe, bulbils in species of Crassula,
adventitious roots from attached stems in Adromischus and other
genera, and adventitious roots from detached stems and leaves in
species of Sedum. There is also evidence of stolons and
rhizomes in some members of this family. The phylogenetic distribution
of the various mechanisms of asexual reproduction within Crassualceae
were examined by tracing these features onto a previously published
estimate of phylogeny for the family. There is evidence to suggest
that certain mechanisms (e.g., stolon formation) have arisen multiple
times within the family. However, additional data are required to
document the developmental patterns and to assess fully the homology
of these asexual mechanisms within the family.
Key words: Asexual reproduction, character evolution, Crassulaceae