Small-scale spatial resource partitioning in a hyperparasitoid community

peer reviewe

Introduced deer and their potential role in disease transmission to livestock in Australia

1. The transmission of pathogens between wildlife and livestock is a globally recognised threat to the livestock industry, as well as to human and wildlife health. Wild cervids are susceptible to many diseases affecting livestock. This presents a challenge for wildlife and domestic animal disease management because the frequent use of agricultural areas by wild cervids may hamper the effectiveness of disease control strategies. 2. Six deer species have established wild populations in Australia and are expanding in range and abundance. A comprehensive literature review of diseases impacting deer and livestock was undertaken, resulting in consideration of 38 pathogens. A qualitative risk assessment was then carried out to assess the overall risk posed by the pathogens to the livestock industry. 3. Five diseases (bovine tuberculosis, foot and mouth disease, malignant catarrhal fever, surra, and screw‐worm fly infestation) ranked highly in our risk assessment. Of these five diseases, only one (malignant catarrhal fever) is currently present in Australia, but all five are notifiable diseases at a national level. Data on these diseases in deer are limited, especially for one of the most abundant species, the sambar deer Rusa unicolor, highlighting a further potential risk attributable to a lack of understanding of disease epidemiology. 4. This paper provides a detailed review of the pathogens affecting both cervids and livestock in Australia, and applies a qualitative framework for assessing the risk posed by deer to the livestock industry. The qualitative framework used here could easily be adapted to assess disease risk in other contexts, making this work relevant to scientists and wildlife managers, as well as to livestock industry workers, worldwide

Global patterns in helminth host specificity: phylogenetic and functional diversity of regional host species pools matter

Host specificity has a major influence on a parasite's ability to shift between human and animal host species. Yet there is a dearth of quantitative approaches to explore variation in host specificity across biogeographical scales, particularly in response to the varying community compositions of potential hosts. We built a global dataset of intermediate host associations for nine of the world's most widespread helminth parasites (all of which infect humans). Using hierarchical models, we asked if realised parasite host specificity varied in response to regional variation in the phylogenetic and functional diversities of potential host species. Parasites were recorded in 4–10 zoogeographical regions, with some showing considerable geographical variation in observed versus expected host specificity. Parasites generally exhibited the lowest phylogenetic host specificity in regions with the greatest variation in prospective host phylogenetic diversity, namely the Neotropical, Saharo-Arabian and Australian regions. Globally, we uncovered notable variation in parasite host shifting potential. Observed host assemblages for Hydatigera taeniaeformis and Hymenolepis diminuta were less phylogenetically diverse than expected, suggesting limited potential to spillover into unrelated hosts. Host assemblages for Echinococcus granulosus, Mesocestoides lineatus and Trichinella spiralis were less functionally diverse than expected, suggesting limited potential to shift across host ecological niches. By contrast, Hyd. taeniaeformis infected a higher functional diversity of hosts than expected, indicating strong potential to shift across hosts with different ecological niches. We show that the realised phylogenetic and functional diversities of infected hosts are determined by biogeographical gradients in prospective host species pools. These findings emphasise the need to account for underlying species diversity when assessing parasite host specificity. Our framework to identify variation in realised host specificity is broadly applicable to other host–parasite systems and will provide key insights into parasite invasion potential at regional and global scales

Trade-offs between developmental parameters of two endoparasitoids developing in different instars of the same host species

Trade-offs amongst life history traits is a major theme in evolutionary biology. Parasitoid wasps are important biological control agents and make excellent organisms to examine trade-offs in fitness related traits such as size, development rate and survival. Here, we examined trait-related trade-offs in 2 solitary endoparasitoids developing in different stages (or instars) of the same caterpillar host, the cabbage moth Mamestra brassicae. Microplitis mediator is a small specialist parasitoid that attacks first (L1) to third (L3) instars of M. brassicae; Meteorus pulchricornis is a larger highly generalized parasitoid that attacks L1-L4 instars of the same host species. When developing in early host instars (e.g. L1-L2), both parasitoids differently traded-off size against development time. In M. mediator, adult body mass was smaller in wasps developing in L1 than in L2 and L3 hosts, whereas development time was unaffected by instar. By contrast, adult body mass in M. pulchricornis was smaller and development time longer when developing in L1 and L2 than in L3 and L4 instars. Periodic starvation of M. brassicae caterpillars parasitized by M. pulchricornis further reduced adult mass and extended development time of wasps in L2 (but not L4) hosts. Maximum egg load in M. pulchricornis (but not M. mediator) was correlated with adult female body size. Our results imply that rapid development time is more important than body size for fitness in both species, although in M. pulchricornis both development time and adult size are traded off in determining the optimal phenotype. Developing a better understanding of association-specific patterns of development in parasitoids can assist in the optimization of mass rearing of these insects for biological control. © 2014 Elsevier Inc

Development of two related endoparasitoids in larvae of the diamondback moth, Plutella xylostella (Lepidoptera: Plutellidae)

We compare the growth and development of two related solitary endoparasitoids (Braconidae, Microgastinae) in different instars (second and third) of the diamondback moth Plutella xylostella. Cotesia vestalis is a well-studied parasitoid whose larvae feed primarily on host hemolymph and fat body whereas Dolichogenidea sicaria is a parasitoid whose larvae consume the entire host caterpillar before pupation. Little is known about the biology of D. sicaria including its association with P. xylostella. When developing in L2 and L3 host instars, survival of both parasitoids to adult was similar. However, development time was longer in D. sicaria than in C. vestalis but the adult wasps were also larger. Both species were protandrous and exhibit sexual size dimorphism, where females were the larger sex. Our results suggest that D. sicaria is a promising new biological control agent of P. xylostella, augmenting better studied parasitoids such as C. vestalis

The cabbage moth or the sorrel moth (Lepidoptera: Noctuidae)?

When insect herbivores develop over many generations on the same plant species, their descendants may evolve physiological adaptations that enable them to develop more successfully on that plant species than naive conspecifics. Here, we compared development of wild and lab-reared caterpillars of the cabbage moth, Mamestra brassicae, on a cultivar of cabbage Brassica oleracea (cv. Cyrus) and on a wild plant species, sorrel, Rumex acetosa, on which the wild strain had been collected and reared for two earlier consecutive generations. The lab strain had been reared on the same cabbage cultivar for more than 20 years representing > 200 generations. Survival to adult did not vary with strain or plant species. Both strains, however, developed significantly faster when reared on R. acetosa than B. oleracea. Pupae from the field strain were larger when reared on B. oleracea than on R. acetosa, whereas the identity of the plant species did not matter for the lab strain. Our results show that long-term rearing history on cabbage had little or no effect on M. brassicae performance, suggesting that some generalist herbivores can readily exploit novel plants that may be chemically very different from those on which they have long been intimately associated