Variation in Spatial Flowering Phase and Cross Pollination in the Sonoran Desert Rock Fig

Abstract

<p>The reproduction of plant species to produce seeds begins with pollination. The timing (phenology) of flowering is influenced by local environmental conditions such that neighboring plants are more likely to flower at the same time and cross-pollinate than are plants located further apart. In contrast to other flowering plants, which produce pollen and ovules simultaneously within the same flowers, wild figs (genus Ficus) produce separate male and female flowers that develop several weeks to months apart. For neighboring fig trees to cross-pollinate, they need to have flowering times that are out of phase with each other, with one tree bearing male flowers while another bears female flowers. As a result, if local environmental conditions synchronize flower production, neighboring fig trees will be less likely to cross-pollinate than trees located farther apart. We tested this prediction in the Sonoran Desert rock fig, Ficus petiolaris. Using information on flowering phenology collected from nine sites over four seasons, we calculated the probability of cross-pollination between trees as a function of the distance between them in the field. In contrast to predictions, we found significant but highly variable spatial patterns of flowering and opportunity for cross-pollination both within and across sites and seasons. An important consequence of this variation is that fig pollinators must traverse highly unpredictable distances to successfully cross-pollinate fig trees.</p>