Nathan M. Schiff

Evolution of the hymenopteran megaradiation

The Hymenoptera--ants, bees and wasps--represent one of the most successful but least understood insect radiations. We present the first comprehensive molecular study spanning the entire order Hymenoptera. It is based on approximately 7 kb of DNA sequence from 4 gene regions (18S, 28S, COI and EF-1α) for 116 species representing all superfamilies and 23 outgroup taxa from eight orders of Holometabola. Results are drawn from both parsimony and statistical (Bayesian and likelihood) analyses, and from both by-eye and secondary-structure alignments. Our analyses provide the first firm molecular evidence for monophyly of the Vespina (Orussoidea+Apocrita). Within Vespina, our results indicate a sister-group relationship between Ichneumonoidea and Proctotrupomorpha, while the stinging wasps (Aculeata) are monophyletic and nested inside Evaniomorpha. In Proctotrupomorpha, our results provide evidence for a novel core clade of proctotrupoids, and support for the recently proposed Diaprioidea. An unexpected result is the support for monophyly of a clade of wood-boring sawflies (Xiphydrioidea+Siricoidea). As in previous molecular studies, Orussidae remain difficult to place and are either sister group to a monophyletic Apocrita, or the sister group of Stephanidae within Apocrita. Both results support a single origin of parasitism, but the latter would propose a controversial reversal in the evolution of the wasp-waist. Generally our results support earlier hypotheses, primarily based on morphology, for a basal grade of phytophagous families giving rise to a single clade of parasitic Hymenoptera, the Vespina, from which predatory, pollen-feeding, gall-forming and eusocial forms evolved.

Trapping Phyllophaga spp. (Coleoptera: Scarabaeidae: Melolonthinae) in the United States and Canada using sex attractants.

Abstract The sex pheromone of the scarab beetle, Phyllophaga anxia, is a blend of the methyl esters of two amino acids, L-valine and L-isoleucine. A field trapping study was conducted, deploying different blends of the two compounds at 59 locations in the United States and Canada. More than 57,000 males of 61 Phyllophaga species (Coleoptera: Scarabaeidae: Melolonthinae) were captured and identified. Three major findings included: (1) widespread use of the two compounds [of the 147Phyllophaga (sensu stricto) species found in the United States and Canada, males of nearly 40% were captured]; (2) in most species intraspecific male response to the pheromone blends was stable between years and over geography; and (3) an unusual pheromone polymorphism was described from P. anxia. Populations at some locations were captured with L-valine methyl ester alone, whereas populations at other locations were captured with L-isoleucine methyl ester alone. At additional locations, the L-valine methyl ester-responding populations and the L-isoleucine methyl ester-responding populations were both present, producing a bimodal capture curve. In southeastern Massachusetts and in Rhode Island, in the United States, P. anxia males were captured with blends of L-valine methyl ester and L-isoleucine methyl ester. Resumen La feromona sexual del escarabajo, Phyllophaga anxia, es una mezcla de los ésteres metílicos de dos aminoácidos, L-valina y L-isoleucina. Se condujo un estudio de campo usando diferentes mezclas de los dos componentes en 59 sitios de Estados Unidos y Canada. Más de 57,000 machos de 61 especies dePhyllophaga fueron capturados e identificados. Tres de los resultados más importantes incluyen: (1) el extenso uso de los dos componentes [de las 147 especies de Phyllophaga (sensu stricto), en Estados Unidos y Canada, fueron capturados machos de cerca del 40% de ellas.]; (2) para la mayoría de las especies, la respuesta intraespecífica de los machos a las combinaciones de los dos aminoácidos fue consistente entre años diferentes, y en todos los sitios geográficos; y (3) un inusual polymorfismo de la feromona fue descrito para P. anxia. Poblaciones de algunos sitios fueron atrapados sólo con valina, mientras que poblaciones de otros sitios fueron atrapados sólo con isoleucina. También se encontraron sitios donde las poblaciones responden a ambos componentes, valina e isoleucina, produciendo una curva de captura bimodal. En el sureste del estado de Massachusetts y en Rhode Island, en Estados Unidos, machos de P. anxia fueron atrapados en trampas con mezclas de valina e isoleucina.

Growth and intraspecific competitive abilities of the dioecious Lindera melissifolia (Lauraceae) in varied flooding regimes.

Abstract The contribution of sexual dimorphism to male-biased colony ratios observed in field populations of the federally endangered Lindera melissifolia was investigated. Growth characteristics and intraspecific relative competitive abilities were determined for first-year male and female L. melissifolia plants grown at varied densities and receiving three flooding treatments. In the no-flooding and 30-day-flooding treatments, stem height, stem diameter, and total leaf area for male plants were significantly greater than that of higher density male plantings and of female plants without respect to density. In both male and female plants, stem growth ceased and leaves were abscised in response to flooding. Although density effects in combination with hydrologic regime influenced intersexual competition, male-bias from competitive exclusion was not indicated. Growth characteristics for male plants grown alone suggest potential for greater interspecific competitive abilities than that of female plants. Therefore, male plants may be better adapted for colonizing suitable habitat, thus contributing to male-biased colony ratios observed in naturally occurring populations.

First Contact Pheromone Identified for a Longhorned Beetle (Coleoptera: Cerambycidae) in the Subfamily Prioninae

Little is known of the reproductive behavior of longhorned beetles (Coleoptera: Cerambycidae) in the subfamily Prioninae. Mallodon dasystomus (Say), the hardwood stump borer, is a widely distributed prionine that is native to the southern U.S. Here, we explored the chemically-mediated mating behavior of M. dasystomus, and tested the hypothesis that males recognize females by a contact pheromone. In mating bioassays, all males tested attempted to mate with females only after contacting females with their antennae. Moreover, all males attempted to mate with solvent-washed dead females treated with as little as 0.15 ± 0.03 female equivalents of conspecific cuticular extracts, confirming that compounds on the cuticle of females are essential for mate recognition. Cuticular hydrocarbon profiles of females contained 13 compounds that were not present in profiles of males. Among the female-specific compounds, two co-dominant methyl-branched alkanes, 2-methylhexacosane (2Me-C26) and 2-methyloctacosane (2Me-C28), accounted for 17% of the total hydrocarbons. Our strategy for identifying the contact pheromone was to synthesize and test the bioactivity of female specific compounds, starting with the most abundant. In bioassays, males displayed mating behavior in response to synthetic 2Me-C26 and 2Me-C28 when tested individually. Furthermore, when these compounds were tested in combination, they elicited the full progression of mating behaviors, suggesting that 2Me-C26 and 2Me-C28 make up the contact pheromone. These findings are further evidence of the critical role of contact pheromones in mating systems of longhorned beetles.

Hermit Thrush is the First Observed Dispersal Agent for Pondberry (Lindera melissifolia)

Abstract We investigated dispersal opportunities for the endangered pondberry, Lindera melissifolia (Lauraceae). In 199 hours of observation at 5 fruiting colonies in the Delta National Forest, Sharkey County, Mississippi, we recorded 82 bird species in the vicinity of a colony. Of these, 12 were observed on pondberry plants, and two consumed ripe pondberry fruits. Of these, the northern cardinal, Cardinalis cardinalis (Cardinalidae), was a seed predator. The other, hermit thrush, Catharus guttatus (Turdidae), was a dispersal agent for the plants. Numbers of fruits declined rapidly after hermit thrushes arrived in October and no fruits remained by January. Winter behavior of hermit thrushes constrains their dispersal of seeds to short distances. Without establishment of additional colonies, pondberry dispersal by birds to unoccupied patches of suitable forest is unlikely.

Bottomland Forests in the Lower Mississippi Alluvial Valley Associated with the Endangered Lindera melissifolia

Abstract Forest canopy and subcanopy data were collected from and compared among five disjunct bottomland hardwood forests in the Lower Mississippi Alluvial Valley, each with known occurrence of a population of the federally endangered shrub Lindera melissifolia. All study sites are cut-over forests, underlain by hydric soils, and have a seasonal high water table. Canopy and subcanopy species are similar among sites, but species differ in relative importance, and flood tolerant tree species exceed that of flood intolerant species. Distribution of L. melissifolia colonies within each study site was not associated with mean tree density or d.b.h. Forest composition and structure at each study site reflect hydrologic regime, topography, historical disturbance, and an absence of recent disturbance. Results of this study provide a quantitative description of bottomland forests that currently sustain L. melissifolia populations. This information may be utilized for development of forest management plans aimed at ensuring continued sustainability of existing L. melissifolia populations and assessing other bottomland hardwood forests for potential reintroduction of this endangered species.

Flooding Facility Helps Scientists Examine the Ecophysiology of Floodplain Species Used in Bottomland Hardwood Restorations

Bottomland hardwood ecosystems, important for their unique functions and values, have experienced considerable degradation since European settlement through deforestation, development, and drainage. Currently, considerable effort is underway to restore ecological functions on degraded bottomland sites. Restoration requires a better understanding of the biological components, especially plants, and their interactions with other biotic and abiotic components of the ecosystem. Previous experimental approaches have focused on the effects of stress on floodplain plant species in controlled, small-scale studies or large, uncontrolled ecosystem-scale studies. We describe a facility, named the Flooding Research Facility (FRF), where hydrologic regimes can be manipulated to study ecophysiology of floodplain species. Key features of the FRF include the ability to establish experiments on a scale larger than would be possible in a greenhouse, but small enough to control key abiotic variables, such as flood frequency, duration, and light availability on native bottomland soil. Design of the FRF allows for random and replicated treatment applications. Additionally, we provide an example of ongoing research on the effects of flooding and light availability on pondberry (Lindera melissifolia), a federally endangered shrub found in the southeastern United States.

Role of Volatile Semiochemicals in the Host and Mate Location Behavior of Mallodon dasystomus (Coleoptera: Cerambycidae)

Little is known of the role semiochemicals play in the mating systems of longhorned beetles (Coleoptera: Cerambycidae) in the primitive subfamily Prioninae. Mallodon dasystomus (Say), the hardwood stump borer, is a widely distributed prionine native to the southern US. Preferred hosts of M. dasystomus include oak, sweetgum, sugarberry and hackberry; although they also colonize a variety of other hardwoods. Here, we study the mate location behavior of M. dasystomus by testing the hypotheses that the sexes are mutually attracted to volatiles emanating from the larval host and that females release a volatile pheromone that is attractive to males alone. In a Y-tube olfactometer, male and female M. dasystomus responded to volatiles from host material (i.e., sweetgum and sugarberry). However, only males responded to females in the olfactometer, suggesting that females release a volatile sex pheromone. In choice experiments conducted in a greenhouse, we determined that both males and females prefer host over non-host material. In further bioassays in the greenhouse, males chose host material containing a live female over that containing a live male or host material alone. These findings are further evidence of the critical role host volatiles and pheromones play in mating systems of longhorned beetles.

New species of Cerambycidae from Panama, with new distribution records (Coleoptera: Cerambycidae).

Two new species of Cerambycidae, Tessaropa elizabeth Bezark, sp. nov. (subfamily Cerambycinae, tribe Methiini ) and Anelaphus cordiforme Tyson, sp. nov. (subfamily Cerambycinae, tribe Elaphidiini), are described from the western part of the Darien, Panama. Nine new country records for Panama are reported for the following species: Adetus linsleyi Mar-tins & Galileo, Estola strandiella Breuning, Nubosoplatus inbio Swift, Paranisopodus heterotarsus Monné & Martins, Pempteurys sericans Bates, Rosalba costaricensis (Melzer), Tomopterus brevicornis Giesbert, Psapharochrus nigricans (Lameere), and Oedudes bifasciata (Bates).

Competition and habitat quality influence age and sex distribution in wintering rusty blackbirds

Bird habitat quality is often inferred from species abundance measures during the breeding and non-breeding season and used for conservation management decisions. However, during the non-breeding season age and sex classes often occupy different habitats which suggest a need for more habitat-specific data. Rusty Blackbird (Euphagus carolinus) is a forested wetland specialist wintering in bottomland hardwood forests in the south-eastern U. S. and belongs to the most steeply declining songbirds in the U.S. Little information is available to support priority birds such as the Rusty Blackbird wintering in this threatened habitat. We assessed age and sex distribution and body condition of Rusty Blackbirds among the three major habitats used by this species in the Lower Mississippi Alluvial Valley and also measured food availability. Overall, pecan groves had the highest biomass mainly driven by the amount of nuts. Invertebrate biomass was highest in forests but contributed only a small percentage to overall biomass. Age and sex classes were unevenly distributed among habitats with adult males primarily occupying pecan groves containing the highest nut biomass, females being found in forests which had the lowest nut biomass and young males primarily staying in forest fragments along creeks which had intermediate nut biomass. Males were in better body condition than females and were in slightly better condition in pecan groves. The results suggest that adult males occupy the highest quality habitat and may competitively exclude the other age and sex classes.