The role of olfactory cues in the sequential radiation of a gall-boring beetle

Species diversity itself may cause additional species diversity. According to recent findings, some species modify their environment in such a way that they facilitate the creation of new niches for other species to evolve to fill. Given the vast speciesdiversity of insects, the occurrence of such sequential radiation of species is likely common among herbivorous insects and the species that depend on them, many of them being insects as well. Herbivorous insects often have close associations with specific host plants and their preferences for mating and ovipositing on a specific host-plant species can reproductively isolate host-specific populations, facilitating speciation. Previous research by our laboratory has established that there are two distinct populations of thegall fly, Eurosta solidaginis (Tephritidae), which attack different species of goldenrods, Solidago altissima (Asteraceae) and S. gigantea. The gall fly’s host-associated differentiation is facilitating the divergence and potential speciation of twosubpopulations of the gall-boring beetle Mordellistena convicta (Mordellidae) by providing new resources (galls on stems of the galdenrods) for the gall-boring beetles. These beetles exist as two host-plant associated populations of inquilines that inhabit the galls induced by the gall fly. While our previous research has provided genetic and behavioral evidence for host-race formation, little is known about the role of their host plants in assortative mating and oviposition-site selection of the gall-boring beetles’ hostassociated populations. Volatile emissions from host plants can play a major role in assisting herbivores to locate their natal host plants and thus facilitate assortative mating and host-specific oviposition. The present study investigated the role of host-plant volatiles in host fidelity (mating on the host plant) and oviposition preference of M. convicta by measuring its behavioral responses to the host-plant volatile emissions using Y-tube olfactometers. In total, we tested behavioral responses of 615 beetles. Our resultsshow that M. convicta adults are attracted to their natal host galls (67% of S. altissima-emerging beetles and 70% of S. gigantea-emerging beetles) and avoid the alternate host galls (75% of S. altissima-emerging beetles and 66% of S. gigantea-emerging beetles),while showing no preference for, or avoidance of, ungalled plants from either species. This suggests that the gall beetles can orient to the volatile chemicals emitted by the galls and can potentially use them to identify suitable sites for mating and/or oviposition. Thus, host-associated mating and oviposition may play a role in the sequential speciation of the gall-boring beetle.

Delayed dispersal as a potential route to cooperative breeding in ambrosia beetles

Abstract  Xyleborini are a species-rich tribe of ambrosia beetles, which are haplodiploid and typically mate among siblings within their natal brood chamber. Several characteristics of this tribe would predict the evolution of higher levels of sociality: high genetic relatedness within galleries due to inbreeding, high costs of dispersal and the potential benefit of cooperation in brood care within the natal gallery (e.g. by fungus gardening, gallery extension, offspring feeding and cleaning). However, information on the social system of these beetles is very limited. We examined the potential for cooperative breeding in Xyleborinus saxeseni by monitoring dispersal in relation to brood size and composition. Results show that adult female offspring delay dispersal despite dispersal opportunities, and apparently some females never disperse. The femalesâ?? decision to stay seems to depend on the presence of eggs and dependent siblings. We found no indication that female offspring reproduce in their natal gallery, as colonies with many mature daughters do not contain more eggs than those with few or no daughters. There is a significant positive relationship between the number of females present and the number of dependent siblings (but not eggs), which suggests that cooperative brood care of female offspring raises colony productivity by improving survival rates of immatures. Our results suggest that cooperative breeding is likely to occur in X. saxeseni and possibly other xyleborine species. We argue that a closer look at sociality within this tribe may yield important information on the factors determining the evolution of cooperative breeding and advanced social organization.

Sensitisation to Ambrosia in Switzerland: a public health threat in waiting

BACKGROUND Ambrosia artemisiifolia (short name = Ambrosia common ragweed) pollen is a potent allergen and has recently been found in Switzerland, spreading from the southwest of the country. The aim of this study is to describe Ambrosia sensitisation rates in the population-based SAPALDIA cohort (Swiss Study on Air Pollution And Lung Diseases In Adults) and to test whether an increase in these rates could be observed. METHODS Among the 6345 participants from 8 areas who provided blood samples in 1991 and 2002, 5823 had valid results for specific IgE against common inhalant allergens tested with Phadiatop. In 2002 Ambrosia sensitisation was measured and positive tests were analysed for Artemisia vulgaris (mugwort). Blood samples taken in 1991 in Ticino and Geneva were also tested for Ambrosia. RESULTS Sensitisation rate (Phadiatop) did not increase significantly between the two surveys and sensitisation was found in 30% of the participants. A proportion of 7.9% showed specific IgE to Ambrosia pollen. The sensitisation rate in Lugano and Geneva had not changed substantially since 1991. Among those sensitised to Ambrosia 82% also showed specific IgE against Artemisia, suggesting a high rate of cross-reactivity. Only 1.3% were sensitized to Ambrosia alone. The incidence of asthma or hay fever in participants with specific IgE to Ambrosia pollen was not higher than in the general study population. CONCLUSION Currently Ambrosia pollen does not appear to be an important cause of inhalant allergies in Switzerland. Sensitisation rates are low and have not increased since 1991. Due to cross-reactivity Ambrosia sensitisation may be a consequence of primary sensitisation to Artemisia. Elimination of Ambrosia plants is nevertheless mandatory to avoid a future increase.

Living in Heterogeneous Woodlands – Are Habitat Continuity or Quality Drivers of Genetic Variability in a Flightless Ground Beetle?

Although genetic diversity is one of the key components of biodiversity, its drivers are still not fully understood. While it is known that genetic diversity is affected both by environmental parameters as well as habitat history, these factors are not often tested together. Therefore, we analyzed 14 microsatellite loci in Abax parallelepipedus, a flightless, forest dwelling ground beetle, from 88 plots in two study regions in Germany. We modeled the effects of historical and environmental variables on allelic richness, and found for one of the regions, the Schorfheide-Chorin, a significant effect of the depth of the litter layer, which is a main component of habitat quality, and of the sampling effort, which serves as an inverse proxy for local population size. For the other region, the Schwäbische Alb, none of the potential drivers showed a significant effect on allelic richness. We conclude that the genetic diversity in our study species is being driven by current local population sizes via environmental variables and not by historical processes in the studied regions. This is also supported by lack of genetic differentiation between local populations sampled from ancient and from recent woodlands. We suggest that the potential effects of former fragmentation and recolonization processes have been mitigated by the large and stable local populations of Abax parallelepipedus in combination with the proximity of the ancient and recent woodlands in the studied landscapes.

Plant genotype affects the quality of oilseed rape (Brassica napus) for adults and larvae of the pollen beetle (Meligethes aeneus)

Plant quality is one of the main factors influencing the fitness of phytophagous insects. Plant quality can vary not only among genotypes of the same host plant species, but also relative to the insect sex or its life stage. In the present study, the performance of larvae and adults of the pollen beetle (Meligethes aeneus F., Coleoptera: Nitidulidae), a major insect pest of oilseed rape crops, is compared on six genotypes of oilseed rape (Brassica napus). All of the traits that are measured vary among genotypes, and comprise larval developmental duration, life span of unfed emerging adults and survival time of field-sampled adults fed with pollen from the different genotypes. No correlation is found between insect performance and quantity of food available, showing that the quality of the food (i.e. pollen) is the fitness determinant for this insect species. Additionally, the performance of larvae and adults is also not correlated despite use of the same plant genotypes, suggesting that the determinants of pollen quality differ at least partially between both life stages. It is hypothesized that this may be a result of extensive differences in diet breadth between the life stages: larvae are specialists of brassicaceous plants, whereas adults are generalists. Finally, it is suggested that the manipulation of plant quality to increase pollen beetle development time may comprise a valuable strategy for favouring biological control by natural enemies of this pest; for example, as a result of extending the vulnerability window of larvae to attack by parasitoids.

Squash Bug, Squash Vine Borer, and Striped Cucumber Beetle on Butternut Squash and Muskmelon

Alternative agricultural schemes are gaining attention as the demand for organic and sustainable products continues to grow. Pest insects pose a sizeable challenge to agricultural production because their activities reduce crop fitness and productivity. Effective management of pest-insects is, therefore, crucial for successful management, and increasingly entails a multi-dimensional approach.

Ground beetle (Carabidae) abundance data from north-eastern Australian rainforest, between June 2008 - January 2010, using pitfall traps

Understanding how the environment influences patterns of diversity is vital for effective conservation management, especially in a changing global climate. While assemblage structure and species richness patterns are often correlated with current environmental factors, historical influences may also be considerable, especially for taxa with poor dispersal abilities. Mountain-top regions throughout tropical rainforests can act as important refugia for taxa characterised by low dispersal capacities such as flightless ground beetles (Carabidae), an ecologically significant predatory group. We surveyed flightless ground beetles along elevational gradients in five different subregions within the Australian Wet Tropics World Heritage Area to investigate (1) whether the diversity and composition of flightless ground beetles are elevationally stratified, and, if so, (2) what environmental factors (other than elevation per se) are associated with these patterns. Generalised linear models and model averaging techniques were used to relate patterns of diversity to environmental factors. Unlike most taxonomic groups, flightless ground beetles increased in species richness and abundance with elevation. Additionally, each subregion consisted of distinct assemblages containing a high level of regional endemic species. Species richness was most strongly positively associated with the historical climatic conditions and negatively associated with severity of recent disturbance (treefalls) and current climatic conditions. Assemblage composition was associated with latitude and current and historical climatic conditions. Our results suggest that distributional patterns of flightless ground beetles are not only likely to be associated with factors that change with elevation (current climatic conditions), but also factors that are independent of elevation (recent disturbance and historical climatic conditions). Variation in historical vegetation stability explained both species richness and assemblage composition patterns, probably reflecting the significance of upland refugia at a geographic time scale. These findings are important for conservation management as upland habitats are under threat from climate change.