THE ECOLOGY OF SEX EXPRESSION IN A GYNODIOECIOUS ISRAELI DESERT SHRUB (OCHRADENUS BACCATUS)

摘要: The main goal of this study was to evaluate sex expression at geographic and individual levels in Ochradenus baccatus, an Israeli desert shrub. Although species formerly thought be strictly dioecious, a survey 24 populations along latitudinal rainfall gradient, we found extremely variable. While females reproduced only by seeds, males ranged across continuum from "pure males" that produced pollen "inconstant males," which seeds addition pollen. For sexual dimorphism evolve cosexuality, it is believed the morphs must compensated for their loss one function (e.g., production) increase remaining (i.e., seed production). In our 9-20 times as many males, showed controlled laboratory experiment offspring had higher germination seedling growth rates. Pure invested more biomass stamens than did inconstant males. Previously published models concerned with evolution dimorphisms have predicted that: (1) frequency should inversely related females, (2) if degree male inconstancy influenced environ- mental factors, then production decline habitat quality. We support both these predictions. ratio not differ significantly 1:1 19 surveyed, incon- stancy vary geographically. fraction fruit population declined on north-south gradient reflected three-fold rainfall. Among populations, negatively correlated postulate advantages conditional ability produce during periods unpredictable pollinator service) will result gynodioecy stable feature 0. bac- catus.