POLLINATION BIOLOGY OF FOUR SOUTHWESTERN SPECIES OF PHLOX (POLEMONIACEAE): INSECT VISITATION IN RELATION TO COROLLA TUBE LENGTH

Abstract

The southwestern Phlox species P. dolichantha, P. superba, P. stansburyi, and P. grayi are a group of morphologically similar species that differ notably in the length of their corolla tubes (approximately 35 to 45 mm, 26 to 33 mm, 19 to 25 mm, and 13 to 16 mm, respectively). We assessed insect visitation to these 4 species over 24-h periods during peak flowering. A diverse array of visitors was documented, including members of the orders Lepidoptera, Diptera, Hymenoptera, and Coleoptera. Although Phlox is generally considered to exhibit a lepidopteran pollination syndrome, all of these species experienced some visitation from non-lepidopterans. Phlox superba and P. grayi received greatest visitation from a hawkmoth (Hyles lineata), and P. dolichantha and P. stansburyi received the most visits from small flies (Anthomyia and Tachypeza, respectively). All Phlox species were visited by lepidopterans, and the hawkmoth species H. lineata was observed visiting all 4 species. Bees were only observed visiting the shorter-tubed P. stansburyi and P. grayi, although bees were present among populations of all 4 species. Our findings suggest that these Phlox species might be more generalist than previously hypothesized and that further investigation into plant-pollinator interactions in the group might contribute to our understanding of their floral evolution.