Analysis of the community structure of yeasts associated with the decaying stems of cactus. II.Opuntia species.

A survey was made of yeast species associated with the decaying pads of 3 prickly pear cacti (Opuntia phaeacantha, O. ficus-indica, andO. lindheimeri) in Arizona and Texas. Yeast communities from 12 localities were compared among localities, amongOpuntia species, and with previous data on yeast communities associated with columnar cacti. The results indicate thatOpuntia necroses contain relatively more yeast species with broader physiological abilities in their communities than columnar necroses. It is argued that differences in chemistry of the opuntias and columnar forms in concert with the insect vectors specific for these cacti account for the differences in yeast community structure. It is further hypothesized that the differences in yeast community structure have been important in the evolution and maintenance of species diversity forDrosophila species which live in the decaying stems or cladodes of various cacti. Most of the yeast community evolution in the cacti is postulated to have proceeded by evolution in situ and not by additions and replacements from outside of the system.