Investigations in plant commonness and rarity: a comparison of seed removal patterns in the widespread Jatropha standleyi and the endemic J. chamelensis (Euphorbiaceae)

During early August to late September 1998 we examined seed dispersal in the tree species Jatropha standleyi (widespread) and J. chamelensis (endemic; Euphorbiaceae) at the Estacion de Biologia Chamela, Jalisco, Mexico. Using general linear models, we found that seed removal from beneath the parental canopy did not differ between the two species and that seed removal was correlated with both seed availability on the ground and rodent predation. We inferred that seed removal was largely mediated by rodents and determined that if a seed was not removed within 4d (approx. 16% chance), it was highly unlikely to be removed at all (approx. 3.5% chance) for both species. We note that although differences in patterns of seed removal may not explain the observed differences in range size, differences between the two species in seed crop size arc similar to patterns found in other endemic/widespread species pairs.