Coevolved reproductive strategies in the oligolectic bee Callonychium petuniae (Apoidea, Andrenidae) and three purple flowered Petunia species (Solanaceae) in southern Brazil

Females of Callonychium petuniae were found to be oligolectic foragers on three sympatric purple flowered Petunia species in Rio Grande do Sul, southern Brazil. Males patrol patches of Petunia flowers in search for females. They also wait for females in or on the flowers and perch for mates in the vicinity of blossoms. Copulation is always initiated on Petunia flowers. Flying in copulation posture, the couple visits Rrther flowers where the female continues to collect pollen. The mates land outside the Petunia patch to copulate for up to 20 min. and then take ofr separately. We interprete the flights in copula posture as male strateies to prevent the female from returning to the area of high competitor abundance for further pollen collecting after copulation. Thereby males may increase their chances to be the last male to mate before the eggs are fertilized. Femals and males of C. petuniae are the most frequent pollinators of purple flowered Petunia species and indiscriminately transfer pollen between them. Cytogenetic analyses of chromosome numbers and meiotic phases in individuals of two sympatric Petunia species and in presumable hybrids showed, however, that the species maintain their integrity. Spontaneous color choices in multicolored patches of dummy flowers revealed that C. petuniae bees have a high preference for Petunia-purple color tones, as seen by the human eye. We discuss the significance of color selectivity by C. petuniae bees and of the visual signals exhibited by purple flowered Petunia species to keep the coevolved reproductive strategies stable.