Kevin A. Williams

Repeated evolution in overlapping mimicry rings among North American velvet ants

Müllerian mimicry, in which two or more harmful species share a similar appearance for mutual benefit, is a widely appreciated, yet relatively uncommon natural phenomenon. Although Müllerian mimicry occurs in vertebrates, most studies are focused on tropical, herbivorous invertebrates. Here we identify a large Müllerian mimicry complex in North American velvet ants (Hymenoptera: Mutillidae). These are conspicuous, diurnal parasitoids of bees and wasps that defend themselves with a powerful sting. We investigate morphological and genetic variation and ask whether morphological similarities are the result of convergent evolution or shared ancestry. We find that 65 species in the velvet ant genus Dasymutilla can be placed into one of six morphologically distinct and geographically delimited mimicry rings. Müllerian colour patterns are primarily the result of independent evolution rather than shared, phylogenetic history. These convergent colour syndromes represent one of the largest known Müllerian mimicry complexes yet identified, particularly in the Northern Hemisphere.

Ecological and Evolutionary Processes Drive the Origin and Maintenance of Imperfect Mimicry

Although the forces behind the evolution of imperfect mimicry remain poorly studied, recent hypotheses suggest that relaxed selection on small-bodied individuals leads to imperfect mimicry. While evolutionary history undoubtedly affects the development of imperfect mimicry, ecological community context has largely been ignored and may be an important driver of imperfect mimicry. Here we investigate how evolutionary and ecological contexts might influence mimetic fidelity in Müllerian and Batesian mimicry systems. In Batesian hoverfly systems we find that body size is not a strong predictor of mimetic fidelity. However, in Müllerian velvet ants we find a weak positive relationship between body size and mimetic fidelity when evolutionary context is controlled for and a much stronger relationship between community diversity and mimetic fidelity. These results suggest that reduced selection on small-bodied individuals may not be a major driver of the evolution of imperfect mimicry and that other factors, such as ecological community context, should be considered when studying the evolution of imperfect mimicry.

Sex association and synonymy in southwestern U.S. species of Dasymutilla (Hymenoptera: Mutillidae)

Species of the velvet ant genus Dasymutilla exhibit extreme sexual dimorphism and many are known from only one sex. Several sets of species from the southwestern U.S. have been suspected of being conspecific based on similar geographic ranges. Here we present DNA sequence data to show that D. candida Mickel is a junior synonym of D. thetis (Blake), D. errabunda Mickel is a junior synonym of D. heliophila (Cockerell), D. caneo (Blake) is a junior synonym of D. monticola (Cresson), D. dugesii (Cockerell and Casad) is a junior synonym of D. foxi (Cockerell), and D. reclusa (Mickel) is a junior synonym of D. birkmani (Melander). Based on genetic and morphological similarity, we also find that D. paenulata Mickel is a junior synonym of D. monticola. Based on a pair taken in copula, D. bollii (Fox) is a junior synonym of D. creon (Blake). Complete diagrams and descriptions of the male genitalia are given for the first time for each species.

Addressing the Dasymutilla quadriguttata Species-Group and Species-Complex (Hymenoptera: Mutillidae): Several Distinct Species or a Single, Morphologically Variable Species?

Abstract This study uses morphological and natural history data, along with molecular data derived from the internal transcribed spacers 1 and 2 (ITS1 and ITS2), to investigate the status of species that are morphologically similar to Dasymutilla quadriguttata. Genetic distances, UPGMA cluster analyses, and maximum parsimony analyses were performed. In addition to those species that are morphologically similar to Dasymutilla quadriguttata, for our analysis we chose other species from the D. quadriguttata species-group that differ sufficiently in morphology as outgroups, as well as species from the D. bioculata and D. nigripes species-groups. These species include D. californica, D. chattahoochei, D. lepeletierii, D. nigripes, and D. wileyae. Conclusions from the analyses are that D. alesia, D. allardi, D. atrifimbriata, D. biguttata, D. castor, D. cypris, D. electra, D. hersilia, D. hora, D. interrupta, D. mediatoria, D. miamensis, D. mutata, D. nigridia, D. nitidula, D. permista, and D. rubricosa are indistinguishable from and junior synonyms of D. quadriguttata. With this knowledge and with past sex associations, the D. castor, D. monticola, and D. quadriguttata species-groups are updated and an addendum to Mickels (1936) Dasymutilla key is provided.

Multifaceted assessment of species validity in the Dasymutilla bioculata species group (Hymenoptera: Mutillidae)

This study examines the validity of the ten species and eight subspecies composing the Dasymutilla bioculata species group. Four lines of evidence are examined: morphological data derived from both sexes; behavioural data derived from the study of mating pairs; geographic distribution; and molecular data derived from the internal transcribed spacers 1 and 2 of the nuclear ribosomal RNA cistron (ITS1 and ITS2). Morphological studies reveal that none of the taxa in question can be consistently diagnosed by any synapomorphies or unique combinations of characters. Mating studies reveal that males of single nominal taxa are attracted to females of multiple nominal taxa, and that females of single nominal taxa attract multiple males. None of the nominal taxa are geographically isolated from the others. Genetic distances between these taxa are significantly lower than those seen in interspecific comparisons of other Dasymutilla species. Based on this evidence, we infer that the taxa in question share a recent common ancestor, and cannot be adequately differentiated using any of the available data sources. Therefore, employing the phylogenetic species concept, Dasymutilla bimaculata Manley & Pitts, Dasymutilla chiron chiron (Blake), Dasymutilla chiron ursula (Cresson), Dasymutilla creusa creusa (Cresson), Dasymutilla creusa bellona (Cresson), Dasymutilla lepeletierii (Fox), Dasymutilla medea (Cresson), Dasymutilla melanippe melanippe Mickel, Dasymutilla melanippe conformis Mickel, Dasymutilla praegrandis praegrandis Mickel, Dasymutilla praegrandis russata Mickel, Dasymutilla pyrrhus (Fox) and Dasymutilla sulcatulla Mickel must be considered junior synonyms of Dasymutilla bioculata (Cresson). We also discuss the identification of this species, as well as subspecific relationships and species‐group implications.

Preliminary Assessment of Velvet Ant (Hymenoptera: Mutillidae) Diversity in the Deserts of Southern California

ABSTRACT. The deserts of southern California house a diverse and unique insect fauna. Velvet ants (Hymenoptera: Mutillidae) are common in these deserts. Velvet ants are important to ecosystem health, particularly in desert environments, because they are parasitic on the bees and wasps that help maintain overall ecosystem function. The goal of this study was to measure velvet ant diversity across the deserts of southern California, We made preliminary collections from 10 sites in a variety of areas in the western Sonoran Desert (Colorado Desert), the Mojave Desert, and the Great Basin Desert. We measured β-diversity using Sørensens similarity index to compare velvet ant richness and relative abundance between different sites. To determine how accurate our similarity estimates were, and to gain an understanding of actual velvet ant diversity, we also compared velvet ant richness of 2 sites (Algodones Sand Dunes and Deep Canyon) using data obtained from the examination of museum specimens borrowed from over 12 museums across the West, Comparisons of velvet ant faunas between sites revealed low similarities (0.167–0.75 species richness only; 0.022–0.67 both abundance and richness), Low similarity values indicate that a rich velvet ant fauna exists in the deserts of southern California.

Phylogeographic Investigations of the Widespread, Arid-Adapted Antlion Brachynemurus sackeni Hagen (Neuroptera: Myrmeleontidae)

Several recent studies investigating patterns of diversification in widespread desert-adapted vertebrates have associated major periods of genetic differentiation to late Neogene mountain-building events; yet few projects have addressed these patterns in widespread invertebrates. We examine phylogeographic patterns in the widespread antlion species Brachynemurus sackeni Hagen (Neuroptera: Myrmeleontidae) using a region of the mitochondrial gene cytochrome oxidase I (COI). We then use a molecular clock to estimate divergence dates for the major lineages. Our analyses resulted in a phylogeny that shows two distinct lineages, both of which are likely distinct species. This reveals the first cryptic species-complex in Myrmeleontidae. The genetic split between lineages dates to about 3.8–4.7 million years ago and may be associated with Neogene mountain building. The phylogeographic pattern does not match patterns found in other taxa. Future analyses within this species-complex may uncover a unique evolutionary history in this group.

The first sexual associations in the genus Darditilla Casal, 1965 (Hymenoptera, Mutillidae)

Abstract New sex associations are proposed for four species of Darditilla: Darditilla amabilis (Gerstaecker, 1874); Darditilla bejaranoi Casal, 1968; Darditilla debilis (Gerstaecker, 1874); and Darditilla felina (Burmeister, 1854). Darditilla botija Casal, 1965, syn. n. is the male of Darditilla amabilis; the other three males were previously unknown. Mutilla decorosa Kohl, 1882, syn. n. is conspecific with Darditilla felina. Descriptions and extended diagnoses are provided for previously unknown males and for females that were not adequately described. These represent the first sex associations for the genus Darditilla.

Caribbean and Mexican Additions to the Dasymutilla bioculata Species-Group (Hymenoptera: Mutillidae)

ABSTRACT Williams et al. (Syst. Entomol. 36: 180–191) discovered that all former members of the Dasymutilla bioculata species-group were synonymous. Here we present a study of Mexican and Caribbean species that closely resemble D. bioculata (Cresson). Dasymutilla bouveiri (André), Dasymutilla chionothrix Manley & Pitts, Dasymutilla concordia Manley & Pitts, Dasymutilla insulana Mickel, Dasymutilla latebalteata (Cameron), Dasymutilla nocticaro Manley & Pitts, Dasymutilla truxali Manley & Pitts, and Dasymutilla Veracruz Manley & Pitts are transferred to the D. bioculata species-group based on morphological similarities with D. bioculata. Placement in the D. bioculata species-group, coupled with overlapping disparate ranges, facilitate the following synonymies. D. truxali is a junior synonym of D. chionothrix. D. Veracruz is a junior synonym of D. latebalteata. D. concordia is a junior synonym of D. nocticaro. Genaro (Caribbean J. Sci. 33: 263–268) provided a key to the males of the Caribbean species, including Dasymutilla bouvieri and D. insulana, but these males were not satisfactorily described. Full descriptions are given for these males and diagnoses are provided for all members of the D. bioculata species-group.

Nectaring by Nocturnal Velvet Ants (Hymenoptera: Mutillidae)

Abstract Velvet ants (Hymenoptera: Mutillidae) are a conspicuous component of the fauna of Nearctic deserts, but little is known about their natural history. We observed a nocturnal aggregation of female velvet ants on the dune-restricted plant Croton californicus var. mohavensis (Euphorbiaceae). We collected 44 female velvet ants on or directly beneath a group of male and female plants during 2 nights. Some individuals were on flowers drinking nectar. The discovery of nocturnal velvet ants on C. californicus marks the first record of nectaring in nocturnal female velvet ants.