Flexible Host Choice and Common Host Switches in the Evolution of Generalist and Specialist Cuckoo Bees (Anthophila: Sphecodes)

Abstract

Specialization makes resource use more efficient and should therefore be a common process in animal evolution. However, this process is not as universal in nature as one might expect. Our study shows that Sphecodes (Halictidae) cuckoo bees frequently change their host over the course of their evolution. To test the evolutionary scenario of host specialization in cuckoo bees, we constructed well-supported phylogenetic trees based on partial sequences of five genes for subtribe Sphecodina (Halictini). We detected up to 17 host switches during Sphecodes evolution based on 37 ingroup species subject to mapping analysis of the hosts associated with the cuckoo bee species. We also examine the direction of evolution of host specialization in Sphecodes using the likelihood ratio test and obtain results to support the bidirectional evolutionary scenario in which specialists can arise from generalists, and vice versa. We explain the existence of generalist species in Sphecodes based on their specialization at the individual level, which is recently known in two species. Our findings suggest flexible host choice and frequent host switches in the evolution of Sphecodes cuckoo bees. This scenario leads us to propose an individual choice constancy hypothesis based on the individual specialization strategy in cuckoo bees. Choice constancy has a close relationship to flower constancy in bees and might be an extension of the latter. Our analysis also shows relationships among the genera Microsphecodes, Eupetersia, Sphecodes and Austrosphecodes, a formerly proposed Sphecodes subgenus. Austrosphecodes species form a basal lineage of the subtribe, and Microsphecodes makes it paraphyletic.

Bees of the family Halictidae Thomson, 1869 from Dominica, Lesser Antilles (Hymenoptera: Apoidea)

“…Sphecodes (Austrosphecodes) is evidently rendered paraphyletic by Microsphecodes based on molecular phylogenetic results (Habermannová et al 2013). The implication of these results is that some or all Austrosphecodes should be synonymized with Microsphecodes.…”

“…The latter name has priority, but if Austrosphecodes is treated at only the subgeneric level, then Microsphecodes should also be treated as a subgenus of Sphecodes. The current phylogenetic hypothesis would allow for Austrosphecodes and Microsphecodes combined to be treated at the generic level since together they form the sister group to other species included in the phylogeny (Habermannová et al 2013). Full taxon sampling of major sphecodine groups has not been completed.…”

Leucophora Satellite Flies (Diptera: Anthomyiidae) as Nest Parasites of Sweat Bees (Hymenoptera: Halictidae) in the Neotropics

“…Thus, this is not only the first observation of Leucophora visiting the nests of any bee species in the Neotropics but also the first case of any anthomyiid fly associated with bees of the tribe Augochlorini. In conclusion, Leucophora satellite flies seem to be, together with Sphecodes cleptoparasitic bees and mutillid parasitoid wasps (Brothers et al 2000, Polidori et al 2009, Habermannová et al 2013, among the more widespread insect natural enemies of halictid bees worldwide.…”

The cuckoo bee genus Sphecodes Latreille, 1804 (Hymenoptera: Halictidae) in Kazakhstan

“…Presently there are nearly 300 species recognized in Sphecodes, and while certain broad groups have been discerned among these (e.g., Meyer, 1919;Michener, 1978), it remains to be discovered what natural clades exist. The only phylogenetic attempt at resolving relationships among species of Sphecodes represented less than 14% of the diversity but nonetheless revealed some potential patterns of interest (Habermannová et al, 2013). Of greatest interest was the revelation that Austrosphecodes Michener, widely considered a subgenus of Sphecodes, were likely more basal among Sphecodina, and related to Microsphecodes Eickwort and Stage (Habermannová et al, 2013).…”