Biological invasions are widely seen as the biggest threat to biodiversity next to the loss of habitats. One aspect of considerable interest is the recruitment of natural enemies after the ...establishment of the invad-ing species and how such enemies link invaders to native communities. However, not all invaders are invasive. Eight cynipid species originating in south-eastern Europe invaded Britain over the last 200 years. Presently they cause no economic concern or have any detectable detrimental effect on the native cynipid fauna. Since their invasions have been allowed to progress without intervention, they provide an excellent opportunity to study the recruitment of natural enemies and their integration into native communities. In contrast, the invasion of Japan by Dryocosmus kuriphilus from China caused great economic concern, because considerable damage to its host trees, Castanea spp. a valuable fruit tree in Japan and elsewhere in the world, is caused by high infestation rates. Here we review the early recruitment of parasitoids to the alien species in the UK and D. kuriphilus in Japan, their role in the invaders population dynamics, and how they link the invaders to native cynipid communities.
This paper discusses the different social parasites of ants, evolutionary routes to inquilism and other specialized forms of social parasitism, and host specificity in social parasites. Case ...histories of host specificity and the degree of integration in 3 social parasite systems, i.e. and (high virulence, low transmission predators of ant brood, which enter host colonies in their final larval instar and mainly inhabit the outer nest chambers), and (high virulence, low transmission cuckoo feeders in ant brood chambers, which enter host colonies in their last larval instar), and (high infestation, low transmission predators in ant brood chambers, which enter host colonies as eggs), and the testing and calibration of 2 host specificity hypotheses are presented.
Hyperspectral imaging is a recent development in the evolving field of UAV remote sensing and a new avenue for habitat condition monitoring. We present preliminary results of a pilot study evaluating ...the use of UAV hyperspectral imaging to detect early stages of Acute Oak Decline (AOD) in a broadleaved forest in the UK. Field observations revealed that, compared to asymptomatic trees, leaves of symptomatic trees show lower levels of water and higher reflectance in the near-infrared part of the spectrum. The observed changes in leaf level reflectance spectra were subtle but statistically significant. Normalised hyperspectral UAV canopy radiance spectra suggest the opposite is occurring: symptomatic trees have lower near-infrared radiances. UAV campaigns suffer from changing illumination conditions and in our case normalizing between image frames is not sufficient. We plan to derive reflectance spectra to enable us to adequately evaluate the observed differences between leaves and canopies.
Rapid and substantial changes have occurred in the parasitoid and inquiline community associated with the agamic galls of Andricus quercuscalicis in Britain since the insect arrived in southern ...England. Over the last 5 years the species composition converged to that recorded from galls from the native range. High rates of attack by inquilines, virtually absent in previous surveys, were recorded in south-east England, but not at the edge of the invaded range. Inquiline abundance was positively correlated with parasitoid species richness, because most parasitoid species concentrated their attack on inquilines. An examination of the guild structure sampled in different parts of the native and invaded range revealed continuous trends away from the native range in a number of community and food-web parameters. The abundance patterns of 4 parasitoid species attacking the gall-maker, and 2 parasitoid species attacking inquiline larvae, were related to: 1) gall morphology; 2) the geographical location of the sample sites; and 3) the abundance of other members of the guild. While parasitism of the agamic galls was low (< 5% in Britain, < 15% in the native range), ten parasitoid species caused local mortalities up to 80% in the sexual galls of A.quercuscalicis collected in the native range. An analysis for spatial variation in density dependent abundance patterns showed both positive and negative density dependence as well as density independent relationship between parasitism and host density at all spatial scales and for all parasitoid species. A comparison between the distributions of A.quercuscalicis and two other invading gall wasps, Andricus kollari and A.lignicola , showed that A.quercuscalicis was the only species positively associated with the presence of Turkey oak (an obligate host tree) and suggests that A.quercuscalicis exhibits the lowest rate of spread.
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