Spatiotemporal variation in mating patterns is poorly known in wind-pollinated plant species. Here, we analysed mating patterns of the wind-pollinated dioecious shrub Pistacia lentiscus by genotyping 904 seeds from 30 mother plants with eight microsatellite markers in a high-density population in two consecutive flowering seasons. We found significant differences in some mating system estimates between years, particularly in the levels of correlated paternity. Overall, within-mothers correlated paternity was higher in 2007 than in 2006 (rpWM = 0.085 and 0.030), which translated into an effective number of fathers (Nep) of 11.8 and 33.6 respectively. Using a smoothing interpolation technique, we show that the effective pollen cloud was spatially structured in patches of high- and low-genetic diversity, which do not remain constant from year to year. In 2006, the among-mothers correlated paternity (rpAM) showed no trend with distance, suggesting no restriction of pollen dispersal. However, in 2007, rpAM was greater than zero at short distances, revealing the existence of small-scale patterns of pollen dispersal. The fact that the studied seasons were climatically homogeneous during the flowering time suggested that the observed differences might be ascribed to between-year phenological variation of individuals in the studied population or other (unknown) factors. Numerical simulations, based on the real data set, indicated that the clumping of males and decreasing plant density, which is related to different types of pollen limitation, greatly increase correlated mating in this wind-pollinated species, which is of relevance under the frame of the continuous anthropogenic habitat disturbance suffered by Mediterranean ecosystems.
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