Reproductive schedule of Medicago lupulina (Leguminosae) in a patchy environment

Abstract

Reproductive schedules for cohorts of Medicago lupulina seedlings were compared in adjacent habitats, distinguished by the presence or absence of a ground cover of mosses. The objective of the study was to determine how the reproductive schedule of a single taxon changes in a patchy environment (i.e., where risk of death changes with habitat type). The mortality rate was higher where mosses were absent, probably because of increased drought stress. In both habitats some plants reproduced for the first time in their second growing season, but the percentage reproducing for the first time in their third or fourth growing season was greater at moss-covered sites (15%) than at moss-free sites (4%). Fewer plants reproduced either once or repeatedly in the moss-free habitat (10% once, 1% repeatedly) than in the moss-covered habitat (18% once, 7% repeatedly). However, the mean number of seeds produced per plant was greater at moss-free sites (0–93) than at moss-covered sites (0–27). These results indicate that the timing, frequency, and amount of reproduction will all change where a species experiences different microhabitats within a patchy environment.