Annual variation of oilseed rape habitat quality and role of grassy field margins for seed eating carabids in arable mosaics

相似文献   

Carabid beetle condition,reproduction and density in winter oilseed rape affected by field and landscape parameters

The carabid beetles Amara similata and Poecilus cupreus are abundant in Central European winter oilseed rape (OSR) fields and potential antagonists of OSR pests. Therefore, they were investigated in 29 OSR fields relative to the influence of field and landscape parameters on their nutritional condition, reproductive potential and activity density. Nutritional condition was measured by a condition factor (CF). Fecundity of female beetles was expressed by the number of ripe oocytes in the ovaries. Activity density comprised the number of individuals caught with pitfall traps during their peak of reproductive period. Soil productivity and pest abundance (as a proxy of local prey availability) were considered as field parameters. Landscape parameters comprised the distance to the next fallow and the percentage of crop area around each study field. In eight of ten cases, pest abundance proved to be the most important factor explaining carabid characteristics, indicating that P. cupreus and A. similata consume insect pests in OSR fields. Pest abundance influenced the CF of both species and sexes positively. Oocyte numbers of A. similata were negatively related to the distance to the next fallow. Oocyte numbers of P. cupreus tended to increase with increasing pest abundance. Activity density of female A. similata was negatively influenced by soil productivity. Activity density of male A. similata and of female and male P. cupreus was negatively influenced by pest abundance. When analysing exclusively the influence of severe OSR pests (Meligethes aeneus, Ceutorhynchus napi and Dasineura brassicae), abundance of larval M. aeneus and C. napi was most important in explaining the CF and activity density of male A. similata, and male and female P. cupreus. M. aeneus and C. napi could be an essential prey for the carabids studied which may reduce the pests, thereby contributing to the protection of OSR from pest herbivory.     

Larval and adult seed consumption affected by the degree of food specialization in Amara (Coleoptera: Carabidae)

Many carabid beetles (Coleoptera: Carabidae) are known to feed on plant seeds, but the level of specialization on this food differs. This is the first study in which seed consumption is assessed for all larval instars and adults of ground beetles. Three species of Amara with syntopic occurrence, Amara aenea (DeGeer), Amara familiaris (Duftschmid) and Amara similata (Gyllenhal), were examined. Larvae of all three instars and adults were fed seeds of Stellaria media (L.) Vill., Capsella bursa‐pastoris (L.) Med. and Taraxacum officinale Wick. ex Wigg. in a laboratory no‐choice experiment. In general, larvae, particularly the first instar, showed greater differences in seed consumption than the adults, although the latter showed similar but less marked pattern. Amara aenea consumed all offered seed diets in all life stages. All three larval instars of granivorous A. familiaris almost exclusively fed on seeds of S. media and the adults also ate significantly more of this than other seeds. Amara similata consumed mostly seeds of C. bursa‐pastoris in the first instar and adult stages, whereas the larvae of the later instars seemed to be unspecialized on particular seed diet. Differences in seed‐specific consumption between larval instars in granivorous carabids are reported for the first time. The results provide further support for the parallel evolution of various degrees of granivory in the genus Amara, which may ultimately facilitate species coexistence. The daily seed consumption by the larvae was comparable or (in case of the third instar) even higher than that by the adults. Hence, we suggest that larvae may be the important consumers of seed in the field and should not be forgotten when seed predation is assessed.     

Rubidium marking reveals different patterns of movement in four ground beetle species (Col., Carabidae) between adjacent alfalfa and maize

相似文献   

Weed seed availability,carabid intraspecific interference and their interaction drive weed seed consumption by carabid beetles

相似文献   

Effect of diet on the fecundity of three carabid beetles

Abstract In the present study, the importance of diet in terms of fecundity is compared for three species of the carabid genus Amara (Coleoptera: Carabidae), using an insect diet, two types of seed diet (Capsella bursa‐pastoris, Stellaria media) and a mixed diet. It is expected that the species of carabid studied have different food requirements for reproduction. Diet affects reproduction performance and egg production significantly. A mixed diet and both single‐seed diets are suitable for reproduction in Amara aenea (DeGeer) because a higher proportion of the females reproduce and lay significantly more eggs than on a purely insect diet. Females of Amara familiaris (Duftschmid) do not reproduce unless provided with seeds of S. media. Seeds of C. bursa‐pastoris or a mixed diet are equally suitable diets for reproduction of Amara similata (Gyllenhal); a diet of insects or seeds of S. media is unsuitable. The results support the hypothesis that the species under investigation have specific food requirements, suggesting that seed feeding has evolved to different degrees in particular species: A. aenea is omnivorous, whereas A. familiaris and A. similata specialize on the seed of a particular plant species or family. This resource partitioning facilitates co‐occurrence of carabid species.     

Influence of within‐field position and adjoining habitat on carabid beetle assemblages in winter wheat

• 1 The influence of within‐field position and adjoining habitat on carabid beetles was studied in 20 winter wheat fields in ten different Swiss agricultural landscapes. In each landscape, two winter wheat fields (one with adjoining sown wildflower area and one with adjoining grassy margin) were investigated.
• 2 Carabid beetles were caught in pitfall traps 3 and 30 m from the edge in each of the 20 wheat fields. Significantly more individuals were found in the centres (30‐m position) than at the edges (3‐m position). Conversely, species richness was significantly higher at the field edges than in the centres.
• 3 Of the ten most abundant species, Poecilus cupreus, Agonum muelleri and Pterostichus melanarius were significantly more abundant in the field centres than at the edges. Harpalus rufipes was significantly more abundant in the fields adjoining sown wildflower areas than in the fields adjoining grassy margins.
• 4 In conclusion, the response of carabid beetles to within‐field position and adjoining habitats was species specific. This needs to be taken into account in habitat management for biodiversity conservation and pest control.

     

Mapping, characterisation, and comparison of the spatio-temporal distributions of cabbage stem flea beetle (Psylliodes chrysocephala), carabids, and Collembola in a crop of winter oilseed rape (Brassica napus)

The spatio‐temporal distribution of Psylliodes chrysocephala (L.) (Coleoptera: Chrysomelidae), a pest of oilseed rape (Brassica napus) (L.) (Cruciferae) and its potential predators, carabid beetles, within a crop of winter oilseed rape is described. The distribution of Collembola, a potential alternative food source for the predators, is also investigated. Insects were collected from spatially referenced sampling points across the crop and the counts mapped, analysed, and the degree of spatial association between the distributions determined using Spatial Analysis by Distance IndicEs (SADIE). Immigration into the crop by adult P. chrysocephala occurred from two edges and resulted in a non‐uniform distribution of the pest within the crop. Infestation of rape plants by P. chrysocephala larvae was greatest within the central area of the crop. Significant spatial association between adult female P. chrysocephala and the larval infestation of plants occurred throughout October. Three carabid species were active and abundant during peak pest immigration into the crop, viz., Trechus quadristriatus (Schrank) (Coleoptera: Carabidae), Pterostichus madidus (Fabricius) (Coleoptera: Carabidae), and Nebria brevicollis (Fabricius) (Coleoptera: Carabidae). Two of these species, T. quadristriatus and P. madidus, showed significant spatial association with the larvae of P. chrysocephala during October. All three carabid species showed a significant spatial association with Collembola during mid‐September, indicating that the latter may be an important food source for carabids during this period. In laboratory feeding experiments, only T. quadristriatus consumed the eggs of P. chrysocephala suggesting that, in the adult stage, this species may be the most important of the naturally occurring carabids as a predator of P. chrysocephala in the field. Adult T. quadristriatus may be a valuable component of an Integrated Pest Management strategy for winter oilseed rape, and the conservation of this species could be beneficial.     

Differentiation of spring carabid beetle assemblages between semi‐natural habitats and adjoining winter wheat

相似文献   

Diversity of foraging strategies and responses to predator interference in seed-eating carabid beetles

The prediction of pest regulation by multi-predator communities often remains challenging because of variable and opposite effects of niche complementarity and predator interference. Carabid communities are regulating weeds in arable fields and include a mix of species ranging from granivores to predators that are obligate omnivores. It is not clear from field studies whether granivore and obligate omnivore species either contribute equally or are complementary in the process of weed suppression, and little is known about the impact of potential predator interference within carabid communities on weed suppression. We compared the weed seed foraging strategy of the granivore Harpalus affinis and the obligate omnivore Poecilus cupreus. Using no-choice test experiments, we compared their activity and seed acceptance for four weed species through a scoring of the proportion of tested individuals consuming weeds, their latency before the consumption of the first seed and the total number of seeds consumed. We then evaluated their seed acceptance for dandelion seed Taraxacum officinale under predator interference by using chemical cues of carabids and tested the impact of three treatments, namely cues of intraspecific competition, interspecific competition and intraguild predation. We found that the obligate omnivore P. cupreus was highly active, had a low latency before consuming its first seed but had an interest in only two of the four weed species. P. cupreus seed acceptance remained unchanged in the presence of predator cues. By contrast, H. affinis was slow to start its seed consumption, accepted equally seeds of the four weed species and significantly increased its seed consumption in the presence of cues mimicking intraguild predation. These findings indicate that the two species differ in their foraging strategies, and as such, could have different contributions to weed seed suppression. This novel result calls for further studies documenting the foraging strategy of carabid species that thrive in arable fields as this could significantly improve our understanding of the delivery of weed seed regulation.     

Interactive effects of local and landscape factors on farmland carabids

相似文献   

Long-term developments in the carabid and staphylinid (Col., CArabidae and Staphylinidae) fauna during conversion from conventional to bilogivcal farming

In two field experiments over periods of 6 and 8 years the activity density and diversity of carabids and staphylids were measured in pitfalls traps during the conversiion fron conventional to biological farming. Positive effects of the conversion were observed for many carabid species; among them Harpalus rufipes and several Amara , Bembidion and Pterostichus species, and the staphylinid fly parasitoid Aleochara bipistulata . The increased number of weed species present could at least partly explain the rise. Negative effects of the conversion were observed for several staphylinid species, among them Philonthus cognatus and Tachyporus species, and the carabid Trechus quadristriatus . It is hypothesized that the reduction in stapjylinids could partly be due to competition from the rising numbers of carabids.     

Niche differentiation and preferences of Elaphrus cupreus Duftschmid, 1812 and Elaphrus uliginosus (Fabricius, 1792) (Coleoptera: Carabidae) as reason for their different endangerment in Central Europe

Ecological demands were studied in Elaphrus cupreus, a frequent species, and E. uliginosus, one of the most endangered carabids in Europe. Ecological experiments were performed in the laboratory and the field in northern Germany. Abundance was measured using the mark-and-recatch method. Both species prefer sites with water content changes lower than 25%. E. uliginosus prefers higher temperatures than E. cupreus and niche breadth was on average wider in E. cupreus than in E. uliginosus. E. uliginosus is restricted to grassland sites with a low fraction (>0 and 25%) of bare soil. E. cupreus was mainly found on sites having >75–100% bare soil. This preference of E. uliginosus can be referred to its high temperature demands using open regions for warming up and its predatory behaviour using hideouts for a rapid predatory push. The wider niche structure and lower temperature demand of E. cupreus allows the inhabitation of cooler alder woods. It prefers large fractions of bare soil because its predatory behaviour is to run randomly on the soil. Thus, E. uliginosus demands wet extensively grazed grassland where cattle produces low fractions of bare soil, while E. cupreus prefers intensively grazed sites in grassland or alder woods.     

Does the presence of grassy strips and landscape grain affect the spatial distribution of aphids and their carabid predators?

• 1 We investigated, over the course of 2 years, the spatial distribution and abundance of two species of aphid, Metopolophium dirhodum and Sitobion avenae, and predatory species of carabid. This was undertaken in 24 wheat fields in ‘coarse‐grain’ and ‘fine‐grain’ landscapes in western France. A greater percentage of the latter landscape was covered by hedgerows and grassland and the total area covered by fields and the average size of the fields were smaller.
• 2 The effects on aphid abundance of the distance from field margins, the presence of grassy strips and carabid abundance were determined in both landscapes.
• 3 Both aphid species were more abundant in the ‘fine‐grain’ landscape, which may have been a result of the higher density of semi‐natural elements. In both types of landscape, the total numbers of aphids were negatively correlated with the distance from the field margin. This may have been because aphids were dispersing from overwintering sites in field margins. The abundance of M. dirhodum was strongly negatively correlated with the presence of grassy strips in the ‘coarse‐grain’ landscape, although there were no such significant correlations for either of the aphid species in the ‘fine‐grain’ landscape.
• 4 Aphid and carabid abundances were negatively correlated in the ‘fine‐grain’ and positively in ‘coarse‐grain’ landscape.
• 5 The results obtained in the present study emphasize the importance of semi‐natural areas in agricultural landscapes in shaping the spatial distribution of aphids and carabid beetles, their natural enemies, at different spatial scales.

     

Monitoring carabid indicators could reveal environmental impacts of genetically modified maize

相似文献   

Predation of eggs ofSitona hispidulus [Col.: Curculionidae] in alfalfa

The predation on egg populations ofSitona hispidus (Fabricius) [Col.: Curculionidae] in a stand of alfalfa was evaluated in 1982 and 1983. By using pitfall traps, catches of reproductive adults ofS. hispidulus were correlated with catches of carabid species, and potential egg predators were identified for further evaluation. Results indicated that predators removed 28 % of eggs under field conditions.Amara aenea DeGeer was found to be particularly efficient on eggs ofS. hispidulus under caged-field conditions.      

Implications for conservation biocontrol of spatio‐temporal relationships between carabid beetles and coleopterous pests in winter oilseed rape

1 The spatio‐temporal distributions of predatory carabid beetles (Coleoptera: Carabidae) and their potential prey, the larvae of three coleopterous pests, Meligethes aeneus (Fabricius) and Ceutorhynchus spp. [Ceutorhynchus pallidactylus (Marsham), the cabbage stem weevil, and Ceutorhynchus assimilis (Paykull), the cabbage seed weevil], were studied within a crop of winter oilseed rape. The distributions of Collembola were recorded as potential alternative prey. Insect distributions were analysed and compared using Spatial Analysis by Distance Indices. 2 Mature larvae of the pests dropped from the crop canopy to the soil for pupation in temporal succession from May to early July. Their distributions within the crop were irregular and differed with species. 3 Adults of seven species or genera of carabid were abundant and active within the crop during May and June: Nebria brevicollis (Fabricius), Anchomenus dorsalis (Pontoppidan), Loricera pilicornis (Fabricius), Amara similata (Gyllenhal), Asaphidion spp., Pterostichus madidus (Fabricius) and Pterostichus melanarius (Illiger). 4 During May, N. brevicollis was spatially associated with peak numbers of M. aeneus larvae and with Collembola. Anchomenus dorsalis was spatially associated with Ceutorhynchus spp. larvae during two peaks in the abundance of the latter in early and late June. Nebria brevicollis and A. dorsalis coincided in both time and space with larvae of the three coleopterous pests when they were most vulnerable to predation by epigeal predators and are therefore good candidates for conservation biocontrol. 5 The importance of carabid beeetles in the natural enemy complex in winter oilseed rape and their potential for biocontrol of spring and summer pests are discussed in relation to husbandry practices for the crop and its adjacent areas which could be manipulated to promote carabid survival for integrated pest management.     

Contrary food requirements of the larvae of two Curtonotus (Coleoptera: Carabidae: Amara) species

The larvae of carabids that are granivorous as adults can be granivorous, omnivorous or carnivorous. The differences in larval food preferences of Amara aulica and Amara convexiuscula, two closely related species of the subgenus Curtonotus, were studied. Survival and duration of development of non‐diapausing first and second instar larvae were compared. The third instar larvae were not studied because they go into diapause prior to pupation. The larvae were fed diets consisting of insect larvae (Tenebrio molitor), seeds of Artemisia vulgaris, Tripleurospermum inodorum, Urtica dioica or Cirsium arvense and a mixed diet consisting of insect larvae and seed. Larvae of A. aulica required seeds for successful development, whereas those of A. convexiuscula developed on both an insect diet and seeds of Artemisia. The difference in larval food requirements facilitates the coexistence of these closely related species, which frequently share the same habitat.     

In-field cover crop strips support carabid communities and shape the ecological trait repartition in maize fields

1. The enhancement of pest regulation service in crops depends for a large part on the capacity of agroecological practices to increase the presence of key species or functional traits in arthropod communities within fields.
2. We investigated the effects of undestroyed strips of winter cover crops in maize fields on carabid community composition, and on the distribution of three ecological traits: diet, wing status and body size.
3. We found that the community composition and the distribution of ecological traits in the in-field cover crop strips had commonalities with both adjacent cropped areas and field margins. Some species were recorded mostly or only in the strips indicating that strips could support carabid species and help increase local diversity from the first year of establishment.
4. The activity-density of Poecilus cupreus and Pterostichus melanarius was higher in the cropped proximity of the strip, and the body size was influenced by the distance from the strip.
5. Our results suggest that carabid communities are shaped by the habitat type, but the influence of such agroecological infrastructures on communities of adjacent crops is minor beyond a distance of 10 m. However, overall species abundance was increased and thus potentially provided enhanced pest regulation.

     

Abundance and diversity of ground-dwelling arthropods of pest management importance in commercial Bt and non-Bt cotton fields

The modified population dynamics of pests targeted by the Cry1Ac toxin in Bacillus thuringiensis (Bt) transgenic cotton (Bt cotton) and possible reduced insecticide use in these transgenic varieties may exert a variety of effects on ground‐dwelling predator communities. A survey of ground‐dwelling arthropods was carried out weekly each of 3 years (during the cropping season) in commercial Bt and non‐Bt cotton fields. Sixty‐five taxa of ground‐dwelling arthropods (carabids, cicindelines, staphylinids, dermapterans, heteropterans and araneids) of importance for cotton pest management were recorded in the survey. Species abundance and dynamics across seasons were evaluated with univariate analysis of variance for higher taxa or multivariate principal response curve analysis for the whole community of 65 taxa. Diversity and richness indices and cumulative species curves also were calculated. The analyses demonstrated no differences in the ground‐dwelling arthropod communities between cotton types. One araneid species, Pardosa pauxilla, comprised ～80% of all araneids, Labidura riparia comprised ～96% of all dermapterans, Megacephala carolina comprised ～97% of cicindelines and four carabid species (Selenophorus palliatus, Apristus latens, Harpalus gravis and Anisodactylus merula) comprised ～80% of carabid species. M. carolina outnumbered all other collected species in each of the 3 years. When only predatory carabid species were considered, A. merula, Calosoma sayi, Harpalus pennsylvanicus and Stenolophus ochropezus were predominant and numbers trapped were similar between cotton types. The abundance of dermapterans, staphylinids, araneids and heteropterans varied among sample dates and across seasons but did not differ between cotton types. The frequent capture of M. carolina, S. palliatus and P. pauxilla in all fields and seasons in both cottons suggests that these species may be important for monitoring further changes in local communities as result of agricultural practices.