Sugar from nectar or from honeydew can prolong parasitoids’ lifespan, enhance their fecundity and foraging ability, and thereby increase their pest suppression efficiency. Sugar sources within crop ...monocultures are considered to be limiting for parasitoids. Nevertheless, only few studies have measured the sugar feeding of parasitoid assemblages in agricultural areas or in surrounding non‐crop habitats.
We used cold anthrone tests to compare the frequency of sugar feeding in parasitoid communities, inside pomegranate orchards and in adjacent natural areas, over two consecutive years. Overall, 40% of the 1610 sampled individuals belonging to 135 species scored positive for sugar.
Sugar‐feeding frequency was lower within the orchards than in the neighbouring natural areas. The proportion of sugar‐fed wasps increased with herbaceous vegetation cover, both within and outside the orchards, suggesting that herbs are a sugar‐rich habitat. Parasitoids sampled from trees and from herbs within the orchards had similar frequencies of sugar feeding, despite differences in wasp species composition.
Our results probably overestimate sugar‐feeding frequencies in the field because sugar‐fed individuals have higher longevity and hence are more likely to be sampled. We propose a simple model to approximate this over‐sampling bias and apply it to Encarsia inaron (Aphelinidae), one of the most abundant parasitoids in the samples.
We conclude that sugar availability potentially limits parasitoid fitness in this agro‐ecosystem. This may be due to the low density of plants in natural areas during the Mediterranean summer, and to herbicide applications within the orchards that further suppress non‐crop herbs.
The chestnut gall wasp Dryocosmus kuriphilus is a global pest of chestnut (Castanea spp). Established as a pest in the mid-twentieth century in Japan, Korea and North America, this species was first ...reported in Europe in 2002. Following the successful release of a biological control agent Torymus sinensis in Japan, this parasitoid species has been released in Italy since 2005. Here we discuss the potential of T. sinensis as a viable management option for the biological control of D. kuriphilus in central Europe. We suggest that more consideration should be given to determining, (i) the conditions under which T. sinensis may attack alternative native gall wasp hosts and (ii) the likelihood of hybridization of this species with native Torymus. Both issues are central to predicting unassisted range expansion by released T. sinensis, and to assess the environmental risks associated with a more widespread release of this species in Europe.
The communities associated with the invading gall wasp Andricus quercuscalicis vary considerably in species richness and species composition throughout its native and invaded ranges. Seventeen ...species of inquilines and parasitoids were identified as coinhabitants of the agamic galls of Andricus quercuscalicis throughout Europe. The life-histories of the parasitoid species are described; one is a solitary endoparasitoid, one a gregarious endoparasitoid and the remainder are solitary ectoparasitoids. A tortricid moth which develops as an inquiline in the agamic galls of A. quercuscalicis kills the gall causer; this is the first description of such an interaction between moths and cynipids. While some parasitoid species appear to be restricted in their attack to the native range of A. quercuscalicis, others were found throughout the range. Geographic variation in the species composition and the possible role of the invasion history of the host are discussed. Food web parameters calculated for the community from the native range and six regions across the invaded range appear to be correlated with the residence time of the invading host, in accordance with studies of successional communities. However, it might be impossible to separate effects of time from those of species richness.
Pollinator declines have motivated efforts to plant nectar and host plants for butterflies and other pollinators, but whether gardens promote pollinator conservation requires further investigation.
...We established garden plots to determine whether plant type (native vs. exotic) and weed maintenance (low or high) influence adult butterfly abundance and species richness, and the abundance and survival of immature stages of four species (monarch, queen, black swallowtail, and gulf fritillary). To assess how predator activity and mortality of immature stages might differ inside gardens compared to other suitable habitat patches, we compared caterpillar survival on sentinel host plants placed within and outside of plots.
The abundance and species richness of adult butterflies (all taxa) increased with the number of flowering plants per plot, but did not depend on plant type or weeding treatment. Exotic plots had greater adult monarch and gulf fritillary abundances, greater monarch and queen egg counts, and lower black swallowtail caterpillar counts relative to native plots.
The survival of immature stages (egg to instar 5) ranged from 2 to 13% and was similar across plots, except for gulf fritillary larvae, which had higher survival in exotic plots. Monarch caterpillar mortality risk was higher on sentinel plants placed inside plots, relative to those outside of plots.
This study suggests that garden plots attracted a diversity of adult butterflies and supported the reproduction of focal species. Given lower immature monarch survival within versus outside of plots, further work is needed to examine natural enemy pressure within pollinator gardens.
The geographical range area of host hypothesis predicts that regionally widespread host species are able to support higher local parasite species richness. In this study, we investigated the ...macro‐ecological patterns in cuckoo bumblebee species richness in relation to the geographical range area of their bumblebee hosts (Hymenoptera: Apidae: Bombini). The cuckoo bumblebees live in naturally fragmented environments composed of host bumblebee colonies upon which they are exclusively dependent.
We collected data on all 11 known cuckoo bumblebee species that are classified as parasites (obligate workerless social parasites) – and all 69 known bumblebee species in Europe.
Whereas some bumblebee hosts harbour several cuckoo bumblebee species, most are cuckoo free (78%). Bumblebees with a large geographical range area hosted more cuckoo bumblebee species than host species with a narrow range area. The geographical range area of cuckoo bumblebee species increased with increasing combined range area of all hosts, but it was smaller than combined range area of all hosts.
We found support for the hypothesis that the geographical range area of the host bumblebee species has an effect on the species richness of cuckoo bumblebees. If the range area of the host bumblebee species decreases, cuckoo bumblebees may become vulnerable to extinction.
Eusocial insects exhibit different kinds of collective behaviours which are the outcomes of interactions among several individuals without central control. Ant societies are ideal models to study ...group behaviours performed by cooperative individuals at caste or at the colony level. In addition to the ecological constraints, such as the costs of maintaining patterns of interactions, the social structure might also affect the collective behaviour in ants.
We tested the effect of Myrmica scabrinodis colony traits (number of queens, colony size, and colony age structure) on four major collective behaviours (aggression against intruders, removal of nestmate corpses, foraging, and colony relocation).
Our results showed that neither the number of queens nor the colony size affected the level of aggression against non‐nestmates while the efficiency of corpse removal was positively correlated with both traits. The age structure of the colony influenced both the aggressiveness towards non‐nestmates and the hygienic behaviours. Subcolonies containing a higher proportion of young individuals were more aggressive and less efficient in corpse removal. All studied traits affected foraging activity, as one of the most important behaviour in colony life.
Some of the ant collective behaviours, like foraging, are determined by many traits and their interaction, while others are mostly determined by one or a few major colony characteristics. Overall, our results suggest that individual tasks which generate collective behaviours depend on different intrinsic traits of the ant colony that make a timely and appropriate behavioural response possible in every situation.
Collective behaviours of Myrmica ants are influenced by several colony traits. The more important tasks are for fitness, the higher is the number of traits that can modify them.
All the colony traits examined (queen number, colony size and age composition) had a strong influence on nest hygienic behaviours and foraging activity.
Other collective behaviours were affected only by more specific colony characteristics, i.e. social defence by colony age composition and nest displacement efficiency by colony size.
rapid assessment of a poorly known insect group Hardwick, Bess; Kaartinen, Riikka; Koponen, Martti ...
Insect conservation and diversity,
January 2016, Letnik:
9, Številka:
1
Journal Article
Recenzirano
'Conservation planning and ecological analyses require large‐scale data on species’ abundance and distribution. We describe a national effort to quickly establish the distributions of taxa with ...hard‐to‐identify adults but easily identifiable larval stages: cynipid gall wasps (Hymenoptera: Cynipidae, Cynipini) on oak (Quercus robur). The survey was implemented by volunteers across 239 sites over 687 km of latitude. It yielded 10 523 galls, which were identified by specialists. The material revealed two species new to Finland and the national distributions and local abundances of 16 species. The likelihood of finding a given species was significantly affected by the visual apparency of its galls. This suggests that some cryptic generations may have been missed in the sampling. At the national level, our study exposed systematic changes in the species richness of insect taxa associated with a patchily distributed host plant towards its range margin. Species’ incidences decline as host trees grow increasingly scattered within the landscape. From a conservation perspective, the data increased eight‐fold the known records of gall wasps from Finland, and informed the first assessment of national threat status of these taxa. Our study reveals how the efforts of the public may be efficiently harnessed for revealing the current status of poorly known taxa. In addition to delivering a first survey of the target taxa, and of factors affecting their distribution, such ‘citizen science’ may generate a permanent base of enthusiasts for the future monitoring of changes and trends.
Butterflies are often considered as opportunistic nectar consumers that visit a range of flower species. The degree of specialisation in foraging behaviour and flower choice may, however, vary ...considerably at the inter‐specific level, from highly specialised to generalist species. In generalist nectar use, there can be intra‐specific variation in the availability and use of floral resources (diversity and abundance) among different populations. Knowing the preferences of nectar‐feeding butterflies can increase the understanding of ecological relationships and resource use and help in developing better strategies for butterfly conservation.
By means of behavioural tracking, we identified foraging patterns of Maniola jurtina butterflies in nectar‐rich and nectar‐poor grasslands. For both males and females, we showed significant preference for the brown knapweed Centaurea jacea and thistles (Cirsium sp.) in nectar‐rich, extensively managed grasslands. In the absence of these preferred species, as is typically the case in nectar‐poor intensively managed sites, M. jurtina nectared on Trifolium pratense and Leucanthemum vulgare. Flower visits were on average shorter on T. pratense compared to C. jacea. These observational results were confirmed by a field experiment in which a wild flower nectar array with C. jacea and T. pratense was introduced.
In extensively managed grasslands, foraging bouts were generally confined to patches of flowering plants and did not involve long flights between flower visits. In intensively managed meadows, butterflies performed longer flights, and ignored more flowers between two consecutive visits. Despite the variety of flower species visited, M. jurtina showed a significant preference for a few nectar sources in a context‐dependent way.
1. In 2002 Microdon myrmicae, a social parasite of Myrmica ants, was taxonomically separated from Microdon mutabilis. The original study in the U.K. found Microdon myrmicae to be specific to one ant ...species, Myrmica scabrinodis, yet it became apparent that the range of Microdon myrmicae includes at least the western Palaearctic. 2. Current knowledge of the European distributions of both Microdon myrmicae and Microdon mutabilis in Europe is reviewed. Also, in detailed studies of two Polish populations, Microdon myrmicae was found to survive equally well with two Myrmica ant species. We examine, however, the possibility that this reflects the presence of two separate Microdon species, each connected to one species of Myrmica. 3. Forty populations of Microdon myrmicae and 37 populations of Microdon mutabilis are currently known in Europe. All the populations in central and southern Europe that were visited after the separation of the two species were identified as Microdon myrmicae, while Microdon mutabilis' recognised range is now restricted to the British Isles and Scandinavia. Myrmica scabrinodis was found to host Microdon myrmicae in 26 out of 31 populations investigated. Four other Myrmica species were identified to the host Microdon myrmicae: Myrmica gallienii (eight populations), Myrmica rubra (four), Myrmica vandeli (one), and Myrmica sabuleti (one). Microdon myrmicae occurs in waterlogged grassland habitats, mainly of the 'Molinietum' type, resulting in a patchy distribution relative to its host ants. 4. In two populations Myrmica scabrinodis and Myrmica gallienii are both abundant and rear Microdon myrmicae in equal proportions. Microdon myrmicae pupae from Myrmica gallienii nests were heavier and the anterior respiratory organs were of significantly different shape. In contrast, the comparisons of Microdon myrmicae pupae among all other populations showed no significant differences, suggesting only one species throughout the European range.
It has been proposed that chemicals on plant elaiosomes aid seed detection by seed-dispersing ants. We hypothesized that the chemical interaction between ants and elaiosomes is more intimate than a ...generic attraction, and that elaiosome chemicals will attract mutualistic but not granivorous ant species. We investigated this by using two gorse species, Ulex minor and U. europaeus, and two associated ant species from European heathlands, the mutualist Myrmica ruginodis and the granivore Tetramorium caespitum. Behavioral studies were conducted with laboratory nests and foraging arenas. Both ants will take Ulex seeds, but while M. ruginodis showed increased antennation toward ether extracts of elaiosome surface chemicals compared with controls, T. caespitum showed no response. Elaiosome extracts were separated into seven lipid fractions. M. ruginodis showed increased antennation only toward the diglyceride fractions of both Ulex species, whereas T. caespitum showed no consistent reaction. This indicates that M. ruginodis can detect the elaiosome by responding to its surface chemicals, but T. caespitum is unresponsive to these chemicals. Responses to surface chemicals could increase the rate of seed detection in the field, and so these results suggest that Ulex elaiosomes produce chemicals that facilitate attraction of mutualistic rather than granivorous ant species. This could reduce seed predation and increase Ulex fitness.
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