NATURAL HYBRIDIZATION AND EXTINCTION OF A POPULATION OF PHYSALIS VIRGINIANA (SOLANACEAE)

A population of Physalis virginiana (Solanaceae) in Durham Co., North Carolina, which comprised about 40 individual plants in 1968, was reduced in size to four depauperate plants which were collected and studied in 1973. Concomitant with this reduction in population size is an increase in the proportion of individuals showing evidence of hybridization with the closely related P. heterophylla, also growing in the vicinity, from no evidence of hybridization in 1968 to 75% hybrid individuals (3 out of 4 surviving plants) in 1973. Two possible reasons are postulated for this hybridization: scarcity of P. virginiana pollen for cross-fertilization in this self-incompatible species and superiority of vegetative growth of hybrids in a changing habitat that has become unsuited for the survival of P. virginiana.