PATTERNS OF HOST-PLANT CHOICE IN BEES OF THE GENUSCHELOSTOMA: THE CONSTRAINT HYPOTHESIS OF HOST-RANGE EVOLUTION IN BEES

Abstract

To trace the evolution of host-plant choice in bees of the genus Chelostoma (Megachilidae), we assessed the host plants of 35 Palearctic, North American and Indomalayan species by microscopically analyzing the pollen loads of 634 females and reconstructed their phylogenetic history based on four genes and a morphological dataset, applying both parsimony and Bayesian methods. All species except two were found to be strict pollen specialists at the level of plant family or genus. These oligolectic species together exploit the flowers of eight different plant orders that are distributed among all major angiosperm lineages. Based on ancestral state reconstruction, we found that oligolecty is the ancestral state in Chelostoma and that the two pollen generalists evolved from oligolectic ancestors. The distinct pattern of host broadening in these two polylectic species, the highly conserved floral specializations within the different clades, the exploitation of unrelated hosts with a striking floral similarity as well as a recent report on larval performance on nonhost pollen in two Chelostoma species clearly suggest that floral host choice is physiologically or neurologically constrained in bees of the genus Chelostoma. Based on this finding, we propose a new hypothesis on the evolution of host range in bees.K E Y W O R D S : Ancestral state reconstruction, evolutionary constraint, oligolecty, phylogeny, pollination, supermatrix.

Pollination Syndromes in Mediterranean Orchids—Implications for Speciation, Taxonomy and Conservation

“…1e), a food-deceptive species, attracts several species of bees as pollinators, particularly Chelostoma rapunculi and C. campanularum (Hym. Megachilidae) (Nilsson, 1983), two species whose females are known to be strongly associated with (i.e., oligolectic on) Campanula flowers (Campanulaceae) (Westrich, 1989;Sedivy et al, 2008) (Fig. 1f).…”

Nests, Petal Usage, Floral Preferences, and Immatures of Osmia (Ozbekosmia) avosetta (Megachilidae: Megachilinae: Osmiini), Including Biological Comparisons with Other Osmiine Bees

“…), and O. rhodoensis is polylectic with a preference for Fabaceae (A. Mü ller, unpubl.). Assuming the phylogenetic relationships within the clade (Ozbekosmia, Tergosmia) as hypothesized above, the polylectic habit of O. rhodoensis appears to be derived, supporting the growing evidence that polylectic species have often evolved from oligolectic ancestors while retaining the original pollen host, (Mü ller, 1996;Larkin et al, 2008;Sedivy et al, 2008), i.e., O. rhodoensis continues to collect pollen of Fabaceae but has added new pollen hosts. That pollen specialization on Fabaceae might be ancestral in this clade is further corroborated by the pollen preferences of species of the subgenus Hemiosmia, the possible sister taxon of the clade (Ozbekosmia, Tergosmia) .…”

Abordagens Históricas No Estudo Das Interações Planta-Polinizador

“…A análise mostrou que a oligoleticia é um caráter ancestral, assim como em Dasypoda, e a troca para a polileticia ocorreu diversas vezes, sendo o número de vezes dependente do tipo de otimização utilizada (ACCTRAN ou DELTRAN). Este padrão de troca da oligoleticia para a polileticia, ainda foi observado também em outros grupos de abelhas, como Anthidiini (Apidae: Megachilinae) (Müller 1996) e Chelostoma (Apidae: Megachilinae) (Sedivy et al 2008).…”