Floral Visitor Guilds of Five Allochronic Flowering Asteraceous Species in a Xeric Community in Central Mexico

Abstract

In this research,we determined: 1) the insect guilds visiting the sower heads of Þve Asteraceae species (Eupatorium petiolare Mocino ex De Candolle, Senecio praecox (Cavanilles) De Candolle, Dahlia coccinea Cavanilles, Tagetes lunulata Ortega,and Verbesina virgata Cavanilles); 2) the role of soral phenology and soral morphology on species composition and frequency of visits of different insect order; and 3) the diurnal schedules of anthophilous visitors and their relationship to temperature and relative humidity. Collections and observations of soral visitors for each species were made over 24 h per day. The Þve Asteraceae were visited by 137 Diptera,Hymenoptera, Coleoptera,and Lepidoptera species. Tagetes lunulata had the highest species richness of soral visitors (41 species),while V. virgata had the lowest (23 species). Apis mellifera L. (Hymenoptera) was the only visitor found visiting all Þve species. Species composition of insect visitors was closely related to plant phenology. Order-level frequency of visits was closely related to soral morphology. Two separate principal component analyses based on frequency of visits and soral morphology showed similar plant species groupings. Two groups of insects (Formicidae and Coleoptera) and two soral traits (ligulae length and presence of a cylindrical-campanulate involucre),respectively,were the variables deter- mining these groupings. The highest frequency of anthophilous visitors coincided with the highest temperatures and the lowest relative humidity levels on sowers of all species,except S. praecox. The combination of diurnal activity and guild visitor analyses in this study showed the importance of including both characteristics in pollination studies.