Colin Favret

ON DEFINING "KEY INNOVATIONS" IN AN ADAPTIVE RADIATION: CYTOCHROME P450S AND PAPILIONIDAE

The concept of the key innovation has been central to discussions of specialization and adaptive radiation in herbivorous insects. Rarely, however, have key innovations been defined mechanistically; typically, a key innovation is described broadly as a complex suite of traits (e.g., the ability to feed on angiosperm plants). Identifying the molecular genetic basis for individual traits that collectively characterize such key innovations can be useful in determining whether all species within a lineage share a particular key innovation or whether convergent innovations have evolved independently. Within the genus Papilio, the ability to feed on a furanocoumarin-containing plant has been identified as a key innovation; over 75% of the species in the genus are associated to some degree with plants containing furanocoumarins. In this group, furanocoumarin metabolism is effected by cytochrome P450 monooxygenases, hemebound proteins known in many organisms to play a role in xenobiotic detoxification. Although furanocoumarin-metabolizing P450s in two species of Papilio do not share high levels of identity overall, conserved elements can be found; in particular, levels of amino acid identity in a putative substrate recognition site are very high. This conservation of amino acid identity contrasts sharply with reportedly high levels of diversification in substrate recognition sites observed in comparisons of proteins within species or between species that do not share a narrow range of host plants. Specialization on a particular group of host plants and subsequent diversification on those hosts may necessitate conservation of function in these regions, which may thus be considered key innovations in a lineage.

Evolution and Diversity of Facultative Symbionts from the Aphid Subfamily Lachninae

ABSTRACT Many aphids harbor a variety of endosymbiotic bacteria. The functions of these symbionts can range from an obligate nutritional role to a facultative role in protecting their hosts against environmental stresses. One such symbiont is “Candidatus Serratia symbiotica,” which is involved in defense against heat and potentially also in aphid nutrition. Lachnid aphids have been the focus of several recent studies investigating the transition of this symbiont from a facultative symbiont to an obligate symbiont. In a phylogenetic analysis of Serratia symbionts from 51 lachnid hosts, we found that diversity in symbiont morphology, distribution, and function is due to multiple independent origins of symbiosis from ancestors belonging to Serratia and possibly also to evolution within distinct symbiont clades. Our results do not support cocladogenesis of “Ca. Serratia symbiotica” with Cinara subgenus Cinara species and weigh against an obligate nutritional role. Finally, we show that species belonging to the subfamily Lachninae have a high incidence of facultative symbiont infection.

Just How Imperiled Are Aquatic Insects? A Case Study of Stoneflies (Plecoptera) in Illinois

Abstract Nearly 5,000 historical and contemporary specimen records of stoneflies (Plecoptera) from Illinois demonstrated that this fauna is highly imperiled, boding poorly for aquatic insect communities in North America and elsewhere. Losses include two extinctions of endemics and 20 extirpations of 77 total species, a rate of loss that is higher than for either mussels or fish in Illinois. Another 19 species (24.7%) were designated as critically imperiled, being known from five or fewer locations. Two families, Perlidae and Perlodidae, experienced the greatest number of losses. Species lost were mostly those with longer life cycles and direct egg hatch. Three historically hyperdiverse regions were identified and losses in all 14 natural divisions were documented. Large river habitats and historically prairie regions have experienced the greatest proportional losses of species. This scenario probably follows for Ephemeroptera, Trichoptera, and Odonata in the Midwest and in other areas with similar glacial and cultural histories.

Migratory Aphid (Hemiptera: Aphididae) Habitat Selection in Agricultural and Adjacent Natural Habitats

Abstract Paired suction traps were used to study the habitat choice of migrating aphids in adjacent crop and natural habitats in east central Illinois. Traps were placed in a row-crop field and a restored prairie for 4 yr at one site, and a row-crop field and a wooded plot for 3 yr at another. Row crops were corn or soybean, rotated annually. We did not wish to sample aphids that were native to the local habitats because they would be in a habitat by circumstance of birth, and not necessarily by choice. We therefore removed from the habitat choice analysis any aphid species that colonize plants in either the agricultural or natural habitat. Numbers of aphids from outside sources in the two adjacent habitats were compared. In 2 of 4 yr, outside-source aphids were more abundant in the row-crop than the restored prairie, despite the absence of potential host plants in both habitats. In all 3 yr, outside-source aphids were trapped in greater numbers in the crop than in the woods. Selection of the crop over the natural habitat occurred during almost all sampling periods throughout the summers. We present possible explanations for the aphids’ apparent preference for crop habitats and provide brief discussions of abundant aphids, local—as well as outside—source species, trapped in our study. We also discuss the relevance of our study to the understanding of long- and short-distance aphid migration and aphid vectoring of plant pathogens.

An aphid lineage maintains a bark‐feeding niche while switching to and diversifying on conifers

Lachnine aphids are unusual among phytophagous insects because they feed on both leafy and woody parts of both angiosperm and conifer hosts. Despite being piercing‐sucking phloem‐feeders, these aphids are most speciose on woody parts of coniferous hosts. To evaluate the significance of this unusual biology on their evolution, we reconstructed the ancestral host and feeding site of the lachnine aphids and estimated important host shifts during their evolution. We sampled 78 species representing 14 of the 18 genera of Lachninae from Asia and North America. We performed parsimony, Bayesian and likelihood phylogenetic analyses of combined mitochondrial Cox1, Cox2, CytB and nuclear EF1a1 DNA sequences. We dated the resulting phylograms important nodes using Bayesian methods and multiple fossil and secondary calibrations. Finally, we used parsimony and Bayesian ancestral state reconstruction to evaluate ancestral feeding ecology. Our results suggest the lachnine common ancestor fed on a woody part of an angiosperm host in the mid‐Cretaceous. A shift to conifer hosts in the Late Cretaceous is correlated with a subsequent increased diversification in the Palaeogene, but a switch to leafy host tissues did not engender a similar burst of diversification. Extant lachnine lineages exhibit the full range of historical association with their hosts: some appeared before, some concomitant with and some after the appearance of their hosts. We conclude our study by placing all the lachnine genera in five tribes.

Wing Morphometry Helps Diagnose Cryptic Species and Resurrect Mindarus pinicolus (Hemiptera: Aphididae)

ABSTRACT Wing venation, two-dimensional and with easily recognized reference points at vein junctions, presents an opportunity for the development of automated insect identification. Using a suite of continuous characters, I investigated the use of wing morphometry for computerized insect identification of cryptic species of the aphid genus Mindarus. A priori groups were determined using cytochrome oxidase 1 DNA barcodes. Discriminant function analysis of 24 wing measurements consistently grouped individuals of unknown taxonomic affinity with the correct a priori groups. The results suggest that diagnostic signal is present in wing morphometry, but the signal is considerably stronger with the addition of morphometry from other aphid appendages, namely, 10 leg and antennal segments. Almost all Mindarus collected in eastern North America have been determined as the balsam twig aphid, Mindarus abietinus Koch (Hemiptera: Aphididae), but molecular diagnostics reveals that the Palearctic species is not present in the Western Hemisphere. Schizoneura pinicola Thomas has been considered a North American synonym of M. abietinus. Morphometric discriminant function analysis suggests that the Abies-feeding eastern North American population is M. pinicolus. The species is here reinstated with a new combination and redescribed.

Comparing the Ephemeroptera and Plecoptera Specimen Databases at the Illinois Natural History Survey and Using Them to Document Changes in the Illinois Fauna

Abstract Databasing of all Ephemeroptera and Plecoptera specimens in the Illinois Natural History Survey Insect Collection has recently been completed. Both databases are Internet-searchable in a simplified format (http://www.inhs.uiuc.edu/cbd/EPT/index.html). Analysis of the databases shows that the Plecoptera are at a much better level of determination than the Ephemeroptera, with 88% of the specimens determined to the species level. Only 22% of Ephemeroptera specimens have been determined to species. The Ephemeroptera collection is also much more narrow in geographic scope, with 74% of determined specimens from Illinois. In contrast, only 30% of determined Plecoptera specimens are from Illinois, with most of the remainder being from across the United States. Four new Illinois records were uncovered in the Ephemeroptera database: Caenis diminuta Walker, C. punctata McDunnough, Pseudocloeon ephippiatum (Traver), and Serratella deficiens (Morgan). Analyses of the data document range reductions in Illinois of the stonefly Neoperla clymene (Newman) and the mayfly Pseudiron centralis McDunnough, range expansion in the stonefly Perlesta nelsoni Stark, and a shift in the prevalence of perlid stonefly species assemblages from Acroneuria in the first half of the 20th century to Perlesta in the second half. We also discuss the change in Plecoptera diversity between historic and modern records from Illinois, and compare the relative stability of Plecoptera species assemblages from the major ecological regions of the state. We encourage entomologists to find other uses for these data and to contribute a growing pool of historic specimen-level data at their own institutions.

Machine vision automated species identification scaled towards production levels

Computer‐automated identification of insect species has long been sought to support activities such as environmental monitoring, forensics, pest diagnostics, border security and vector epidemiology, to name just a few. In order to succeed, an automated identification programme capable of addressing the needs of the end user should be able to classify hundreds of taxa, if not thousands, and is expected to distinguish closely related and hence morphologically similar species. However, it remains unknown how automated identification methods might handle an increase in data quantity, be it in reference imagery or taxonomic diversity. We sought to test the scalability of an automated identification method in terms of the number of reference specimens used to train the classifier and the number of taxa into which the classifier should assign unknown specimens. Is there an optimal number of reference images, where the cost of acquiring more images becomes greater than the marginal increase in identification success? Does increasing taxonomic diversity affect identification success, whether negatively or positively? In order to test the scalability of the automated insect identification enterprise, we used a sparse processing technique and support vector machine to test the largest dataset to date: 72 species of fruit flies (Diptera: Tephritidae) and 76 species of mosquitoes (Diptera: Culicidae). We found that: (i) machine vision methods are capable of correctly classifying large numbers of closely related species; (ii) when the misclassification of a specimen occurs at the species level, it is often classified in the correct genus; (iii) classification success increases asymptotically as new training images are added to the dataset; (iv) broad taxon sampling outside a focal group can increase classification success within it.

Is There a Cryptic Species Within Aulacorthum solani (Hemiptera: Aphididae)?

ABSTRACT Examination of DNA sequences of the 5′ end of the mitochondrial cytochrome oxidase I gene of Aulacorthum solani (Kaltenbach) (Hemiptera: Aphididae) reveals little variation between samples from broad geographic provenances. The apparent genetic similarity despite A. solanis morphological and biological differences contrasts with the species complexes of other aphid pests.

Catalog of the Aphid Genera Described from the New World

Abstract A nomenclatural and bibliographic catalog of the genus-group names of aphids (Hemiptera: Aphidoidea) from the New World is presented. The catalog includes 206 available genus-group names with type species with New World localities, full bibliographic citations, and other associated nomenclatural and taxonomic information. Two nomenclatural discrepancies are resolved: Siphonophora acerifoliae Thomas is designated the type species of Phymatosiphum Davis, and Strenaphis Quednau nomen novum is proposed as a replacement name for the homonymic Stenaphis Quednau.