Multi-year stigmatic pollen-load sampling reveals temporal stability in interspecific pollination of flowers in a subalpine meadow

Co-flowering plants may commonly experience interspecific pollination. It remains unknown, however, whether interspecific pollination is a largely stochastic process or consistent enough over years to exert selection for traits that can reduce interspecific pollination or ameliorate its deleterious effects on reproduction. To assess the likelihood of this precondition being met, stigmatic pollen loads on 17 to 34 insect-pollinated plant species over 3 consecutive years were scored in a subalpine meadow in southwestern China. Plant species varied significantly in the amount and proportion of heterospecific pollen (HP) on stigmas. Both the number of HP species and the proportion of the pollen load that was HP for each recipient species correlated positively between years (reflected in pairwise correlations for all year-by-year combinations). Although inter-annual variation was smaller for conspecific pollen (CP) than for HP loads, species tended to experience either consistently high or c...