Interpretation of gypsy moth frontal advance using meteorology in a conditional algorithm.

The gypsy moth, Lymantria dispar, is a non-native species that continues to invade areas in North America. It spreads generally through stratified dispersal where local growth and diffusive spread are coupled with long-distance jumps ahead of the leading edge. Long-distance jumps due to anthropogenic movement of life stages is a well-documented spread mechanism. Another mechanism is the atmospheric transport of early instars and adult males, believed to occur over short distances. However, empirical gypsy moth population data continue to support the possibility of alternative methods of long-range dispersal. Such dispersal events seemed to have occurred in the mid- to late-1990s with spread across Lake Michigan to Wisconsin. Such dispersal would be against the prevailing wind flow for the area and would have crossed a significant physical barrier (Lake Michigan). The climatology of the region shows that vigorous cyclones can result in strong easterly winds in the area at the time when early instars are present. It is hypothesized that these storms would enable individuals to be blown across the Lake and explain the appearance of new population centers observed at several locations on the western shore of Lake Michigan nearly simultaneously. A synoptic climatology model coupled with population dynamics data from the area was parameterized to show an association between transport events and population spread from 1996 to 2007. This work highlights the importance of atmospheric transport events relative to the invasion dynamics of the gypsy moth, and serves as a model for understanding this mechanism of spread in other related biological invasions.

Critical patch size generated by Allee effect in gypsy moth, Lymantria dispar (L.).

Allee effects are important dynamical mechanisms in small-density populations in which per capita population growth rate increases with density. When positive density dependence is sufficiently severe (a 'strong' Allee effect), a critical density arises below which populations do not persist. For spatially distributed populations subject to dispersal, theory predicts that the occupied area also exhibits a critical threshold for population persistence, but this result has not been confirmed in nature. We tested this prediction in patterns of population persistence across the invasion front of the European gypsy moth (Lymantria dispar) in the United States in data collected between 1996 and 2008. Our analysis consistently provided evidence for effects of both population area and density on persistence, as predicted by the general theory, and confirmed here using a mechanistic model developed for the gypsy moth system. We believe this study to be the first empirical documentation of critical patch size induced by an Allee effect.

Dispersion in time and space affect mating success and Allee effects in invading gypsy moth populations.

1. Understanding why invading populations sometimes fail to establish is of considerable relevance to the development of strategies for managing biological invasions. 2. Newly arriving populations tend to be sparse and are often influenced by Allee effects. Mating failure is a typical cause of Allee effects in low-density insect populations, and dispersion of individuals in space and time can exacerbate mate-location failure in invading populations. 3. Here we evaluate the relative importance of dispersal and sexual asynchrony as contributors to Allee effects in invading populations by adopting as a case study the gypsy moth (Lymantria dispar L.), an important insect defoliator for which considerable demographic information is available. 4. We used release-recapture experiments to parameterize a model that describes probabilities that males locate females along various spatial and temporal offsets between male and female adult emergence. 5. Based on these experimental results, we developed a generalized model of mating success that demonstrates the existence of an Allee threshold, below which introduced gypsy moth populations are likely to go extinct without any management intervention.

Grape cane gallmaker (Coleoptera: Curculionidae) and its impact on cultivated grapes.

The grape cane gallmaker, Ampeloglypter sesostris (Leconte), is a native weevil that infests new shoots of wild and cultivated grapes (Vitis spp.). Females oviposit on the tender portions of new shoots, producing a reddish gall that can expand the shoot to twice its normal diameter. These galls can be quite numerous in eastern vineyards, and their effects are unknown. We studied the spatial distribution of grape cane gallmaker and its impact on berry size, sugar content, and nutrient and mineral uptake. We observed spatial trends in grape cane gallmaker distribution in vineyards adjacent to woodland margins, with the trend emanating from the woodline. In vineyards without woodland margins, there was little spatial dependency in grape cane gallmaker distribution in individual years. However, grape cane gallmaker density on a single vine was spatially cross-correlated between 2 yr. The presence of galls did not significantly affect berry quality, or the uptake of nutrients and minerals, and we conclude that grape cane gallmaker does not negatively impact berry quality or mature vine vigor.

Reservoir competence of Carcinops pumilio for Salmonella enteritidis (Eubacteriales: Enterobacteriaceae).

The histerid beetle Carcinops pumilio (Erichson) occurs naturally in poultry house manure and is an important predator of house fly eggs and larvae. Because efforts to commercially produce C. pumilio have been unsuccessful, one fly control strategy under consideration is the direct transport of adult C. pumilio between poultry houses to facilitate their establishment. However, we demonstrate that C. pumilio is a competent reservoir of Salmonella enteritidis (Gaertner). Adult C. pumilio exposed to S. enteritidis-inoculated house fly eggs harbored the bacterium externally and internally for up to 4 and 13 d, respectively, and feces were culture-positive for S. enteritidis for at least 14 d. This suggests that C. pumilio can be a reservoir of S. enteritidis; therefore its movement between poultry facilities should be carefully considered.

Spatio-temporal dynamics of resident and immigrating populations of Carcinops pumilio (Coleoptera: Histeridae) in high-rise poultry facilities.

The histerid beetle Carcinops pumilio (Erichson) is an important natural predator of the house fly, Musca domestica L., in accumulated poultry house manure. We examined the spatio-temporal dynamics of establishing adult C. pumilio in high-rise poultry facilities using conventional and geostatistical approaches. The growth curves of resident and immigrating populations followed logistic and exponential equations, respectively, and their rates of establishment were statistically the same. Frequency distributions for both populations were strongly positively skewed, and approximately 53% of sampling intervals were significantly modeled by the negative binomial. Taylor's power law indicated both populations to be aggregated, and gave excellent least squares regression fits to both populations. Correlograms, a geostatistical tool, suggested little local spatial structure (e.g., 2nd order effects) for either population. The resident population was 'randomly' aggregated: beetles were clustered around randomly distributed aggregations of house fly immatures. The immigrating population exhibited significant spatial trends (e.g., 1st order effects) consistently seen at all sampling intervals. C. pumilio spatial structure was represented primarily by this spatial trend; thus, immigration of C. pumilio may have been either a singular event in time, or initiating at 1 or multiple times from a singular location.

Flotation method for extracting insects from poultry manure samples.

We examined the efficacy of a sucrose-based flotation method for extracting 3 prevalent insect species from poultry house manure: 3rd-instar Musca domestica L. (Diptera: Muscidae), Carcinops pumilio (Erichson) (Coleoptera: Histeridae) adults, and Alphitobius diaperinus (Panzer) (Coleoptera: Tenebrionidae) adults. A 0.6 M sucrose solution in distilled water altered the specific gravity to 1.2 and caused the 3 species to float to the water surface for easy separation. An analysis of variance (ANOVA) showed significant effects of the solution volume to sample mass ratio on recovery rates (F = 35.96, P < 0.0001), but no differences in species-specific recovery rates (F = 0.97, P = 0.3824). Among samples agitated in a ratio of at least 3.2 ml solution per gram of sample mass, we observed neither significant ratio effects (F = 1.37, P = 0.2442) nor significant differences in species-specific recovery rates (F = 2.05, P = 0.1353); overall, we recovered 97.49 +/- 0.20% of all individuals of the 3 species. Our analyses demonstrated that sucrose-based flotation was a statistically valid method of collecting these species from poultry manure samples.

Hypertension and cerebral arteries: relationship to disruption of the blood-brain barrier.

This study was performed to determine whether structural changes in cerebral arterioles could account for differences in susceptibility of the blood-brain barrier to acute hypertensive disruption between hypertensive and normotensive animals. We studied spontaneously hypertensive rats (SHR), 3 other models of hypertension and their normotensive controls. The age and duration of hypertension of the rats were matched to an earlier study showing that protection of the blood-brain barrier was usually found in rats with chronic hypertension. We measured the dimensions of fixed pial arterioles and minimal cerebrovascular resistance produced by bicuculline. Minimal cerebrovascular resistance was not different between the groups of animals. There were no differences in the area of the media of pial arterioles between any of the groups. In addition, we examined the possibility that sympathetic nerves might affect cerebrovascular resistance during bicuculline in SHR. The presence of sympathetic nerves in SHR, but not WKY, reduced the degree of cerebral vascular dilation during bicuculline. From these data we conclude that 1) structural changes in cerebral vessels do not account for protection of the blood-brain barrier in rats with a moderate duration of hypertension and 2) sympathetic nerves may have an exaggerated effect on cerebral vessels of SHR.