Phylogenetic studies of apoid wasps (Hymenoptera, Apoidea) with insights into the evolution of complex behaviors.
The wasp superfamily Apoidea -- a group composed of more than 20,000 species of solitary, cleptoparasitic, and social bees, as well as a paraphyletic grade of more than 9,600 species of predatory and cleptoparasitic wasps -- has played an outsized role in the history of behavioral research. Favorite subjects of field naturalists and ethologists for more than two hundred years, these insects have evolved a tremendous diversity of behavioral strategies, each one an equally successful variation on a shared ancestral groundplan. Understanding the course of these evolutionary derivations and innovations is an important part of understanding insect behavior in toto, and one that requires a phylogenetically informed, comparative approach. As a contribution to ongoing efforts in apoid phylogenetic systematics -- and by extension to the study of behavioral evolution within the group -- the current work presents four phylogenetic studies of apoid taxa, with an additional fifth study examining the placement of Apoidea within Hymenoptera as a whole. Each provides some insight into the evolution of a complex behavioral syndrome, namely the development of predatory behavior from within a parasitoid wasp clade (Chapter II), the origins of cleptoparasitism in apid bees (Chapter III), trends in prey choice among philanthine wasps (Chapters IV and V), and innovations in nesting behavior within thread-waisted wasps (Chapter VI). In the first of these studies, I use a combination of direct optimization phylogeny reconstruction and clade sensitivity analysis to re-examine a previously published total evidence dataset based on 111 taxa from across Hymenoptera. This new analysis simultaneously reveals and formalizes deep topological instabilities within this important insect order, and shows how such instability can complicate back-of-the-envelope reconstructions of behavioral evolution (e.g., the origins of aculeate predatory behavior from within a paraphyletic "Parasitica"). In the second, I demonstrate once again the importance of combining multiple classes of phylogenetically informative characters through a simultaneous reanalysis of the bee family Apidae. By merging previously published datasets based on molecular, behavioral, and adult and larval morphological characters (and by providing new adult and larval character codings for taxa previously represented by molecular data alone), I add qualified support to a recently published, nucleotide-derived hypothesis concerning the origins of cleptoparasitism. This hypothesis -- that the trait evolved fewer times than previously supposed, with the nomadine and "melectine" lineages sharing a common cleptoparasitic ancestor -- is corroborated under a variety of different transformation cost parameters and appears relatively robust to the addition of morphological and behavioral data. The next two studies present the results of the most taxonomically comprehensive phylogenetic analyses of the digger wasp subfamily Philanthinae (Apoidea: Crabronidae) to date. While Chapter IV represents the first molecular analysis of the group to include species level terminals from all eight genera and all four tribes, Chapter V expands that work to include 66 newly coded morphological and behavioral characters. Although basal relationships among the four tribes remain either ambiguous or poorly supported, monophyly of the hyperdiverse, cosmopolitan genus Cerceris is strongly suggested for the first time -- a finding that challenges previous notions concerning the evolution of prey choice within the "beetlewolf" tribe Cercerini. Finally, the last study briefly examines relationships among the so-called "thread-waisted wasps" of the family Sphecidae sensu stricto as a prelude to a larger study of nest evolution within the group. While maximum parsimony analysis of 16 nest-related behavioral characters produces a largely unresolved topology, cladistic analysis of a three-gene dataset reveals new cases of paraphyly at both the tribal and generic levels. I briefly discuss the implications of this latter topology for our understanding of nest evolution within the group.
xiv, 256 pages : illustrations (chiefly color)
Wasps., Hymenoptera., Phylogeny., Behavior evolution., Social evolution in animals.