Variation in seed set amongst populations of a rodent pollinated geophyte, Colchicum coloratum

Abstract

Agricultural activities around the rural village of Nieuwoudtville in the Succulent Karoo region of South Africa has lead to the confinement of many plant and animal species to fragmented patches of relatively untransformed habitat. The geophyte Colchicum coloratum subsp. coloratum (Colchicaceae) was studied in five patches of variable size in and around Nieuwoudtville. This species is dependent on rodent visitation for seed production. The influence of variation in population size and plant size on seed set was investigated, as well as whether there is pollen limitation in this species. A pollen-supplementation experiment indicates that there is pollen limitation in C. coloratum, and that much of the natural seed set could be the result of pollinator-mediated selfing. The five populations appeared to have different rodent abundances, however, neither population size nor the abundance of rodents in the area have an effect on seed set. This suggests that the mutualism between C. colchicum and its rodent pollinators is robust, and that habitat fragmentation in Nieuwoudtville has not yet affected the seed production of this geophyte.