Joseph S. Wilson

Sampling bee communities (Hymenoptera: Apiformes) in a desert landscape: Are pan traps sufficient?

Abstract Pan traps (colored plastic bowls) are frequently used as an efficient standardized method of sampling bee faunas. We explored the utility of pan traps in three colors compared to net collecting using simultaneous sampling at biweekly intervals throughout the flowering season (May–Sep) at 11 sites in the eastern Great Basin Desert. Pan traps deployed for one day (9:00–16:00) on average captured significantly larger samples than net collections (2 hr.) at all intervals except the latter half of May. Average species richness for net collections exceeded pan traps only during late May and late September, periods with abundant floral resources. Capture rates were similar between colors. The composition of bees was also similar; Sørensens similarity values exceeded 0.7. Color preferences for pollen specialists did not match flower color of their hosts. There were significant differences in species composition between net collections and pan trap collections. Almost one-third of the species showed a strong bias toward one method and in some cases between pan trap colors. The methods appear complementary: Halictinae and Perdita were predominantly collected in pan traps (85%); three genera, Anthidium, Colletes, Epeolus were largely or entirely detected by netting. Net collecting should be used in addition to pan traps if comprehensive inventories are desired. Though pan trapping constitutes a standardized method that avoids collector bias, it may not be unbiased; capture rates were lowest when flowering plant richness was greatest.

Illuminating the lack of consensus among descriptions of earth history data in the North American deserts: a resource for biologists.

Understanding the timing of mountain building and desert formation events in western North America is crucial to understanding the evolutionary history of the diverse arid-adapted biota that is found there. While many different, often conflicting descriptions exist regarding geobiotic change in western North America, little work has been done to synthesize these various viewpoints. In this paper we present several case studies that illustrate the differences in the various explanations, based on geological and paleobiological data, detailing mountain uplift and desertification in western North America. The majority of the descriptions detailing mountain building in this area fall into two major periods of uplift, the Laramide uplift (∼70—50 Ma) and the Neogene uplift (∼15—2 Ma), yet it remains unclear which of these events was responsible for the formation of the modern mountains. Like the descriptions of mountain building, various accounts exist detailing the timing of desert formation. Some authors suggest that the deserts existed as far back as 15 Ma while others propose that desert formation occurred as recently as 10,000 years ago. Based on this review of the literature, we suggest that the data on Cenozoic geomorphological evolution of the North American desert landscape is still too coarse and filled with gaps to allow for the development of a robust model of landscape evolution. Instead, this work demonstrates the need for biologists studying the North American biota to realize just how problematic some of the earth history data and models are so that they can build this uncertainty into biogeographic reconstructions.

Host conservatism, host shifts and diversification across three trophic levels in two Neotropical forests

Host–parasite systems have been models for understanding the connection between shifts in resource use and diversification. Despite theoretical expectations, ambiguity remains regarding the frequency and importance of host switches as drivers of speciation in herbivorous insects and their parasitoids. We examine phylogenetic patterns with multiple genetic markers across three trophic levels using a diverse lineage of geometrid moths (Eois), specialist braconid parasitoids (Parapanteles) and plants in the genus Piper. Host–parasite associations are mapped onto phylogenies, and levels of cospeciation are assessed. We find nonrandom patterns of host use within both the moth and wasp phylogenies. The moth–plant associations in particular are characterized by small radiations of moths associated with unique host plants in the same geographic area (i.e. closely related moths using the same host plant species). We suggest a model of diversification that emphasizes an interplay of factors including host shifts, vicariance and adaptation to intraspecific variation within hosts.

The evolution of novel host use is unlikely to be constrained by trade‐offs or a lack of genetic variation

The genetic and ecological factors that shape the evolution of animal diets remain poorly understood. For herbivorous insects, the expectation has been that trade‐offs exist, such that adaptation to one host plant reduces performance on other potential hosts. We investigated the genetic architecture of alternative host use by rearing individual Lycaeides melissa butterflies from two wild populations in a crossed design on two hosts (one native and one introduced) and analysing the genetic basis of differences in performance using genomic approaches. Survival during the experiment was highest when butterfly larvae were reared on their natal host plant, consistent with local adaptation. However, cross‐host correlations in performance among families (within populations) were not different from zero. We found that L. melissa populations possess genetic variation for larval performance and variation in performance had a polygenic basis. We documented very few genetic variants with trade‐offs that would inherently constrain diet breadth by preventing the optimization of performance across hosts. Instead, most genetic variants that affected performance on one host had little to no effect on the other host. In total, these results suggest that genetic trade‐offs are not the primary cause of dietary specialization in L. melissa butterflies.

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.

The race is not to the swift: Long-term data reveal pervasive declines in California's low-elevation butterfly fauna

Understanding the ecology of extinction is one of the primary challenges facing ecologists in the 21st century. Much of our current understanding of extinction, particularly for invertebrates, comes from studies with large geographic coverage but less temporal resolution, such as comparisons between historical collection records and contemporary surveys for geographic regions or political entities. We present a complementary approach involving a data set that is geographically restricted but temporally intensive: we focus on three sites in the Central Valley of California, and utilize 35 years of biweekly (every two weeks) surveys at our most long-sampled site. Previous analyses of these data revealed declines in richness over recent decades. Here, we take a more detailed approach to investigate the mode of decline for this fauna. We ask if all species are in decline, or only a subset. We also investigate traits commonly found to be predictors of extinction risk in other studies, such as body size, diet breadth, habitat association, and geographic range. We find that population declines are ubiquitous: the majority of species at our three focal sites (but not at a nearby site at higher elevation) are characterized by reductions in the fraction of days that they are observed per year. These declines are not readily predicted by ecological traits, with the possible exception of ruderal/non-ruderal status. Ruderal species, in slightly less precipitous decline than non-ruderal taxa, are more dispersive and more likely to be associated with disturbed habitats and exotic hosts. We conclude that population declines and extirpation, particularly in regions severely and recently impacted by anthropogenic alteration, might not be as predictable as has been suggested by other studies on the ecology of extinction.

Intraspecific phytochemical variation shapes community and population structure for specialist caterpillars

Summary Chemically mediated plant–herbivore interactions contribute to the diversity of terrestrial communities and the diversification of plants and insects. While our understanding of the processes affecting community structure and evolutionary diversification has grown, few studies have investigated how trait variation shapes genetic and species diversity simultaneously in a tropical ecosystem. We investigated secondary metabolite variation among subpopulations of a single plant species, Piper kelleyi (Piperaceae), using high‐performance liquid chromatography (HPLC), to understand associations between plant phytochemistry and host‐specialized caterpillars in the genus Eois (Geometridae: Larentiinae) and associated parasitoid wasps and flies. In addition, we used a genotyping‐by‐sequencing approach to examine the genetic structure of one abundant caterpillar species, Eois encina, in relation to host phytochemical variation. We found substantive concentration differences among three major secondary metabolites, and these differences in chemistry predicted caterpillar and parasitoid community structure among host plant populations. Furthermore, E. encina populations located at high elevations were genetically different from other populations. They fed on plants containing high concentrations of prenylated benzoic acid. Thus, phytochemistry potentially shapes caterpillar and wasp community composition and geographic variation in species interactions, both of which can contribute to diversification of plants and insects.

Family-Level Divergences in the Stinging Wasps (Hymenoptera: Aculeata), with Correlations to Angiosperm Diversification

Diversification in insects has often been linked to the evolution of angiosperms. The majority of studies reporting this link, however, have been done on herbivorous insects. It remains unclear if the diversification of angiosperms was also influential in the diversification of species-rich, carnivorous insect groups. Here we investigate the timing of the origin and diversification in the stinging wasps (Hymenoptera: Aculeata). We employ a Bayesian Markov chain Monte Carlo relaxed clock approach to estimate divergence times for 13 wasp families and eight superfamilies. Divergence times are calibrated with 12 fossils representing groups in various lineages. Our results indicate that many of the modern aculeate families originated during the Cretaceous and in concert with the diversification of angiosperms. This similarity between diversification ages in wasps and in angiosperms may be due to an increased habitat complexity and prey diversity that early angiosperm forests provided.

Specificity, rank preference, and the colonization of a non-native host plant by the Melissa blue butterfly

Animals often express behavioral preferences for different types of food or other resources, and these preferences can evolve or shift following association with novel food types. Shifts in preference can involve at least two phenomena: a change in rank preference or a change in specificity. The former corresponds to a change in the order in which hosts are preferred, while a shift in specificity can be an increase in the tendency to utilize multiple hosts. These possibilities have been examined in relatively few systems that include extensive population-level replication. The Melissa blue butterfly, Lycaeides melissa, has colonized exotic alfalfa, Medicago sativa, throughout western North America. We assayed the host preferences of 229 females from ten populations associated with novel and native hosts. In four out of five native-associated populations, a native host was preferred over the exotic host, while preference for a native host characterized only two out of five of the alfalfa-associated populations. Across all individuals from alfalfa-associated populations, there appears to have been a decrease in specificity: females from these populations lay fewer eggs on the native host and more eggs on the exotic relative to females from native-host populations. However, females from alfalfa-associated populations did not lay more eggs on a third plant species, which suggests that preferences for specific hosts in this system can potentially be gained and lost independently. Geographic variation in oviposition preference in L. melissa highlights the value of surveying a large number of populations when studying the evolution of a complex behavioral trait.

Revision of Velvet Ant Genus Dilophotopsis Schuster (Hymenoptera: Mutillidae) by Using Molecular and Morphological Data, with Implications for Desert Biogeography

Abstract Taxonomy of the wide-ranging Nearctic velvet ant genus Dilophotopsis Schuster (Hymenoptera: Mutillidae) is reviewed using molecular and morphological comparisons. The validity of the four designated subspecies of Dilophotopsis concolor (Cresson) is examined. Dilophotopsis concolor paron (Cameron) is morphologically and molecularly distinct from the other three subspecies, and it is raised to the species level [D. paron (Cameron), nov. stat.]. Dilophotopsis concolor crassa (Viereck) and Dilophotopsis concolor laredo Schuster are morphologically indistinguishable from the nominative subspecies D. concolor concolor, and they are considered junior synonyms of this species. A key to the species of Dilophotopsis is provided. The distributions of Dilophotopsis species, as well as the genetic variation within D. concolor, are associated with individual arid lands, and they indicate that this genus will be useful in the study of the historical biogeography of the North American arid lands.