Smaller habitat patch sizes tend to support lower numbers of species than larger patches according to the species-area hypothesis. For nectivorous pollinating insects particularly, feeding efficiency is driven by the size and floral density of a patch. I counted the number of insects visiting Helianthus annuus (Asteraceae) flowers in small (5-10 m2), medium (17-33 m2) and large (75-393 m2) patches over two consecutive days near Succor Creek State Natural Area, Oregon. The mean number of all insect species was significantly different across the three patch sizes (One Way ANOVA, p=0.001). Specifically, large and medium sized patches contained higher numbers of species (12.2±2.3 and 11.3±2.2, respectively [mean±standard deviation]) than small patches (6.5±1.2) (One Way ANOVA, p=<0.001; Holm-Sidak Multiple Comparison Procedures, p=<0.001 and p=0.001, respectively). The mean number of true pollinator species was higher in the large and medium sized patches (7.2±2.5 and 7.3±1.4, respectively) compared to the small patches (4.5±1.0) (One Way ANOVA, p=0.017; Holm-Sidak, p<0.05 for both comparisons). My data are consistent with the results of previous studies showing a decline in pollinator species richness with patch size and indicate that habitat patch size and fragmentation are important considerations in the design and implementation of pollinator conservation management plans.

Increased Helianthus annuus (Asteraceae) patch size leads to higher insect pollinator richness near Succor Creek State Natural Area, Oregon