Size- and season-related sex expression and reproductive performance in gynodioecious Ochradenus baccatus Delile (Resedaceae), at Wadi Degla, Egypt

Reproductive performance and phenology in gynodioecious Ochradenus baccatus was investigated at Wadi Degla, in Egypt's arid Eastern Desert. Between January and December 2005, plants representing a series of size classes were identified from two populations, located ca. 7.5 km apart. A total of 94 individuals were marked and classified according to sex expression and overall size/canopy volume. Reproductive phenology was monitored across the year. Plants presented an extended reproductive phenology having two peaks, in spring and autumn. Plant size was a significant factor influencing reproductive output and phenology. Fruit number, seeds-per-fruit and seed mass all varied significantly among the size classes of both female and hermaphrodite plants, during both spring and autumn phenophases. Numbers of fruit and seeds-per-fruit were greater in spring than autumn, and female forms had greater fruit numbers, seed mass and percent germination, and fewer seeds-per-fruit than hermaphrodites. Numbers of fruits, seeds-per-fruit and seed mass were all significantly positively correlated with plant size. Seeds produced at the larger downstream population had greater seed germination rates than those from the upper site. Results are discussed in terms of plant size and directed seed dispersal patterns.