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Carabid Assemblages (Coleoptera: Carabidae) in a Rotation of Three Different Crops in Southern Alberta, Canada: A Comparison of Sustainable and Conventional Farming

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Carabids were sampled in 2000 (pretreatment year) and 2003-2005 in experimental plots in southern Alberta, Canada, after a rotation of beans, wheat, and potato under sustainable and conventional farming practices. Each phase of the rotation was present in every year. Crop type had a stronger effect than sustainable treatment on carabid-expected species richness, diversity, and species composition. However, carabid activity density was consistently higher in plots under sustainable treatments than those maintained conventionally. Potato plots, which were sprayed with insecticide for pest control, showed a significantly lower carabid activity density than the other crops. These results support other studies showing the beneficial effect of sustainable farming on activity density of carabid beetles.
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... The canopy architecture of intercropped plants offers various conditions at the soil surface favoring protection from predators, microclimate, access to light or wind and rain penetration (Bourassa et al. 2008). For example, while a dense canopy provides moist and shady shelter for the egg deposition of predators such as carabid Pterostichus melanarius, an open canopy may favor species that need drier and warmer environments for thermoregulation (Munyuli et al. 2007). ...
... Allelopathic effects are the same as those described in the 'Cover crop: dead and living mulch' section, and composted chicken manure inoculated with a plant-beneficial fungus (Trichoderma virens) suppressed weed emergence more than a chemical herbicide due to its production of antibiotic compounds within tomato crops (Héraux et al. 2005 Preceding crops can provide poor or rich habitats in terms of microclimate or food provision. In a potato-wheat-bean rotation, the composition of Carabidae was likely influenced by the different canopy densities between bean and wheat (Bourassa et al. 2008). Similarly, corn favored soil arthropods dominated by Acari and Collembola while soybean favored foliar arthropods dominated by Diptera and Hemiptera within a conventional long rotation (Adams et al. 2017). ...
... Amara spp.), with no effect on the other epigeal arthropods (e.g. spiders) (Hummel et al. 2002b;Bourassa et al. 2008) On the contrary, a higher carabid activity (mostly Harpalus sp.) was also found in full-tilled compared to strip-tilled zucchini cropping systems, which showed a resilience of carabid to soil disturbance (Quinn et al. 2016). Within conservation agriculture -which implies no-till farmingand without the use of pesticides, Brainard et al. (2016) reported a net dis-service in the regulation of pest compared to conventional tillage in snap bean production. ...
Thesis
Au cours du siècle dernier, la transition agro-industrielle a profondément modifié le mode de production agricole dans les pays développés, entrainant de nombreux impacts négatifs sur la biodiversité et le fonctionnement des agroécosystèmes. L’agroécologie a récemment émergé comme alternative à ce système de production. A l’interface entre discipline scientifique et pratiques agricoles, l’agroécologie se base sur le support et le maintien de processus écologiques d’intérêts. A travers une analyse bibliographique, nous avons mis en évidence le nombre relativement faible d’études écologiques dans les pratiques agroécologiques. Parmi ces dernières, peu de travaux lient pratiques et biodiversité. Nous avons également montré que les exploitations maraichères étaient sous-représentées, tandis que les micro-fermes étaient quasi inexistantes alors que les pratiques agroécologiques sont fréquentes dans ces deux environnements. C’est dans ce cadre que s’inscrit cette thèse qui vise à comprendre les impacts écologiques de la mise en place I/ de deux associations de cultures et II/ de la culture sur buttes dans un contexte de production de tomates en micro-fermes maraichères. En raison des propriétés biocides des composés soufrés identifiés chez les plantes du genre Allium et de la capacité des légumineuses à fixer l’azote atmosphérique dans leur racine à l’aide de bactéries symbiotiques, le poireau et le haricot valorisés en vente directe, ont été sélectionnés pour être associés à la tomate. Une expérimentation in situ a été réalisée sur deux sites du Sud-Ouest de la France en 2018 et 2019, pour évaluer les conséquences de la mise en place de ces pratiques sur les performances de la tomate en termes de croissance et de rendement, ainsi que sur les communautés de nématodes, bioindicateurs du fonctionnement du sol. Nos observations ont mis en évidence l’importance de l’historique de culture et de la qualité du sol dans la réponse des plantes et des organismes du sol à la mise en place de ces pratiques. L’analyse des communautés de nématodes nous a permis de mettre en évidence un enrichissement du sol en réponse à l’association haricot-tomate. La culture en association avec le poireau n’a eu que peu d’effets sur les communautés de nématodes, mais est liée à de meilleures performances végétales des tomates. La culture sur buttes n’a pas eu d’effet sur les performances de la tomate, malgré un enrichissement du sol visible à travers les communautés de nématodes, dominées par les bactérivores, et une plus grande abondance d’autres organismes du sol. Une interaction entre culture sur buttes et associations a été observée. Les effets de l’association haricot-tomate étaient d’autant moins marqués que le milieu était enrichi par la culture sur buttes. A l’inverse, l’effet positif de l’association avec le poireau semblait plus marqué avec une culture sur buttes. Une expérimentation en système simplifié a été effectuée pour évaluer le potentiel du poireau à contrôler l’un des ravageurs de la tomate, le nématode à galles Meloidogyne incognita. La présence du poireau n’a pas réduit l’infestation des racines de tomates par les nématodes mais a semblé inhiber leur reproduction. La croissance plus importante et la floraison précoce des tomates associées s’expliquent par une compétition entre plantes moins importante qu’en monoculture. Les résultats obtenus lors de cette thèse soutiennent ici l’importance de la prise en compte des organismes bioindicateurs dans l’étude du fonctionnement du sol. Ils apportent également des éléments sur les avantages respectifs de la mise en place des pratiques étudiées, notamment dans le service de biocontrôle, nous ont permis d’émettre l’hypothèse d’un effet de facilitation du poireau sur la croissance des tomates.
... However, in a related mark-releaserecapture experiment, individuals of the adventive, dominant, and mobile carabid Pterostichus melanarius (Illiger) (Coleoptera: Carabidae) entered the intercrop more often than the monocultures, suggesting an effect of vegetation structure on habitat choice for this species (Cárcamo and Spence 1994). At Vauxhall, Alberta, Bourassa et al. (2008) found that carabid species composition differed among small plots of wheat, bean (Phaseolus vulgaris Linnaeus; Fabaceae), and potato. Potato plots had lower carabid activity density than wheat and bean plots, but the crops did not differ in terms of diversity, and there were species-specific responses to crop species (Bourassa et al. 2008). ...
... At Vauxhall, Alberta, Bourassa et al. (2008) found that carabid species composition differed among small plots of wheat, bean (Phaseolus vulgaris Linnaeus; Fabaceae), and potato. Potato plots had lower carabid activity density than wheat and bean plots, but the crops did not differ in terms of diversity, and there were species-specific responses to crop species (Bourassa et al. 2008). However, other agricultural practices and inputs varied between the crops in the rotation, confounding the results (Bourassa et al. 2008). ...
... Potato plots had lower carabid activity density than wheat and bean plots, but the crops did not differ in terms of diversity, and there were species-specific responses to crop species (Bourassa et al. 2008). However, other agricultural practices and inputs varied between the crops in the rotation, confounding the results (Bourassa et al. 2008). ...
Article
The prairie grasslands have been transformed to become the primary source of agricultural production in Canada. Soon after its establishment, the Biological Survey of Canada recognised the urgent need to document the arthropods of the prairie grasslands, especially in the few pristine remnants. Although this initiative has yielded considerable progress in documenting the species present in the Prairies Ecozone, comprehensive ecological studies are sparse. Landscape effects on arthropods are well studied elsewhere, but no equivalent studies have been published for the Canadian Prairies. Crop rotation varies landscape composition annually, changes host plant resources in fields, and interacts with other agricultural inputs to disturb pest and beneficial arthropods. Despite only a handful of studies on grazing, there is an emerging pattern: moderate grazing increases arthropod diversity and benefits certain arthropod guilds. Abiotic inputs elicit variable responses from different arthropod taxa; Carabidae (Coleoptera) are best studied, with some information available for ants (Hymenoptera: Formicidae) and aquatic arthropods. Biotic inputs include arthropods released for biocontrol of weed and insect pests; evidence indicates that biocontrol agents of insects have a greater potential for impact on native communities of arthropods. The studies reviewed here reveal important trends and research gaps to be addressed in the future.
... Several of the most abundant ground beetle species collected in this study have been previously reported as abundant in agroecosystems in North America and elsewhere, highlighting their importance to agroecosystems. Examples include B. quadrimaculatum in alfalfa, carrots, corn, potatoes, soybeans, and wheat (Esau and Peters 1975, Best and Beegle 1977, Hsin et al. 1979, Boivin and Hance 1994, Ellsbury et al. 1998, Kinnunen and Tiainen 1999, Melnychuk et al. 2003, Floate et al. 2007, Bourassa et al. 2008, Bourassa et al. 2010); Bembidion rapidum (LeConte) in corn, soybeans, and wheat (Best and Beegle 1977, Hsin et al. 1979, Clark et al. 2006 ); Harpalus pensylvanicus (DeGeer) in alfalfa, corn, millet, pasture grass, sorghum, soybeans, sunflowers, and wheat (Rivard 1966, Kirk 1971, Best and Beegle 1977, Hsin et al. 1979, Weiss et al. 1990, Tonhasca 1993, Pavuk et al. 1997, Ellsbury et al. 1998, Clark et al. 2006, Miller and Peairs 2008 ; Stenolophus comma (F.) in alfalfa, beans, corn, potatoes , sainfoin, and wheat (Hsin et al. 1979, Lester and Morrill 1989, Bourassa et al. 2008 ); Elaphropus anceps (LeConte) in corn, soybeans , and wheat (Clark et al. 2006), H. erraticus in corn (Kirk 1971); Amara carinata (LeConte) in beans, corn, and potatoes (Kirk 1971, Floate et al. 2007, Bourassa et al. 2008); Amara farcta LeConte in alfalfa, beans, corn, potatoes, sainfoin, and wheat (Lester and Morrill 1989, Bourassa et al. 2008, Bourassa et al. 2010); Bembidion tetracolum Say in cabbage (Armstrong and McKinlay 1997, Prasad and Snyder 2004); and Harpalus amputatus Say in alfalfa, corn, millet, sainfoin, sorghum, sunflower, and wheat (Lester and Morrill 1989, Miller and Peairs 2008). Table 5. Comparisons of mean (6 SEM) ground beetle (Coleoptera: Carabidae) species richness, Simpson's diversity index (reciprocal), and Simpson's evenness between seed-applied insecticide sugarbeet and untreated sugarbeet during 2012 and 2013 Species richness (S) Simpson's diversity (1/D) Simpson's evenness (E) Environmental Entomology, 2016, Vol. ...
... Several of the most abundant ground beetle species collected in this study have been previously reported as abundant in agroecosystems in North America and elsewhere, highlighting their importance to agroecosystems. Examples include B. quadrimaculatum in alfalfa, carrots, corn, potatoes, soybeans, and wheat (Esau and Peters 1975, Best and Beegle 1977, Hsin et al. 1979, Boivin and Hance 1994, Ellsbury et al. 1998, Kinnunen and Tiainen 1999, Melnychuk et al. 2003, Floate et al. 2007, Bourassa et al. 2008, Bourassa et al. 2010); Bembidion rapidum (LeConte) in corn, soybeans, and wheat (Best and Beegle 1977, Hsin et al. 1979, Clark et al. 2006 ); Harpalus pensylvanicus (DeGeer) in alfalfa, corn, millet, pasture grass, sorghum, soybeans, sunflowers, and wheat (Rivard 1966, Kirk 1971, Best and Beegle 1977, Hsin et al. 1979, Weiss et al. 1990, Tonhasca 1993, Pavuk et al. 1997, Ellsbury et al. 1998, Clark et al. 2006, Miller and Peairs 2008 ; Stenolophus comma (F.) in alfalfa, beans, corn, potatoes , sainfoin, and wheat (Hsin et al. 1979, Lester and Morrill 1989, Bourassa et al. 2008 ); Elaphropus anceps (LeConte) in corn, soybeans , and wheat (Clark et al. 2006), H. erraticus in corn (Kirk 1971); Amara carinata (LeConte) in beans, corn, and potatoes (Kirk 1971, Floate et al. 2007, Bourassa et al. 2008); Amara farcta LeConte in alfalfa, beans, corn, potatoes, sainfoin, and wheat (Lester and Morrill 1989, Bourassa et al. 2008, Bourassa et al. 2010); Bembidion tetracolum Say in cabbage (Armstrong and McKinlay 1997, Prasad and Snyder 2004); and Harpalus amputatus Say in alfalfa, corn, millet, sainfoin, sorghum, sunflower, and wheat (Lester and Morrill 1989, Miller and Peairs 2008). Table 5. Comparisons of mean (6 SEM) ground beetle (Coleoptera: Carabidae) species richness, Simpson's diversity index (reciprocal), and Simpson's evenness between seed-applied insecticide sugarbeet and untreated sugarbeet during 2012 and 2013 Species richness (S) Simpson's diversity (1/D) Simpson's evenness (E) Environmental Entomology, 2016, Vol. ...
... Several of the most abundant ground beetle species collected in this study have been previously reported as abundant in agroecosystems in North America and elsewhere, highlighting their importance to agroecosystems. Examples include B. quadrimaculatum in alfalfa, carrots, corn, potatoes, soybeans, and wheat (Esau and Peters 1975, Best and Beegle 1977, Hsin et al. 1979, Boivin and Hance 1994, Ellsbury et al. 1998, Kinnunen and Tiainen 1999, Melnychuk et al. 2003, Floate et al. 2007, Bourassa et al. 2008, Bourassa et al. 2010); Bembidion rapidum (LeConte) in corn, soybeans, and wheat (Best and Beegle 1977, Hsin et al. 1979, Clark et al. 2006 ); Harpalus pensylvanicus (DeGeer) in alfalfa, corn, millet, pasture grass, sorghum, soybeans, sunflowers, and wheat (Rivard 1966, Kirk 1971, Best and Beegle 1977, Hsin et al. 1979, Weiss et al. 1990, Tonhasca 1993, Pavuk et al. 1997, Ellsbury et al. 1998, Clark et al. 2006, Miller and Peairs 2008 ; Stenolophus comma (F.) in alfalfa, beans, corn, potatoes , sainfoin, and wheat (Hsin et al. 1979, Lester and Morrill 1989, Bourassa et al. 2008 ); Elaphropus anceps (LeConte) in corn, soybeans , and wheat (Clark et al. 2006), H. erraticus in corn (Kirk 1971); Amara carinata (LeConte) in beans, corn, and potatoes (Kirk 1971, Floate et al. 2007, Bourassa et al. 2008); Amara farcta LeConte in alfalfa, beans, corn, potatoes, sainfoin, and wheat (Lester and Morrill 1989, Bourassa et al. 2008, Bourassa et al. 2010); Bembidion tetracolum Say in cabbage (Armstrong and McKinlay 1997, Prasad and Snyder 2004); and Harpalus amputatus Say in alfalfa, corn, millet, sainfoin, sorghum, sunflower, and wheat (Lester and Morrill 1989, Miller and Peairs 2008). Table 5. Comparisons of mean (6 SEM) ground beetle (Coleoptera: Carabidae) species richness, Simpson's diversity index (reciprocal), and Simpson's evenness between seed-applied insecticide sugarbeet and untreated sugarbeet during 2012 and 2013 Species richness (S) Simpson's diversity (1/D) Simpson's evenness (E) Environmental Entomology, 2016, Vol. ...
Article
This study investigated the impact of a neonicotinoid seed-applied insecticide (Poncho Beta) and two plant densities (86,487 and 61,776 plants per hectare) on the sugarbeet root aphid (Pemphigus betae Doane), beneficial epigeal arthropods, and selected crop yield parameters in sugarbeet (Beta vulgaris L. var. vulgaris). Ground beetles and centipedes were the most commonly collected taxa during 2012 and 2013, respectively. Centipede, spider, and rove beetle activity densities were not affected by the seed-applied insecticide, whereas plant density had a marginal effect on centipede activity density during 2012. Ground beetle species richness, diversity, and evenness were also not impacted by the seed treatments. However, during 2013, ground beetle activity density was significantly higher in plots planted with untreated sugarbeet seeds due to the abundance of Bembidion quadrimaculatum oppositum Say. Sugarbeet root aphid populations were significantly higher in the untreated plots during both years. In 2012, sugarbeet tonnage and sugar yield were higher under the low plant density treatment, while higher sugar content was recorded from the seed-applied insecticide plots (2013). Seed-applied neonicotinoids and plant density had little impact on beneficial epigeal arthropod activity density. Seed treatment did result in decreased root aphid populations; however, these reductions were not sufficient to be considered as an adequate control. This limited aphid control likely contributed to inconsistent effects on yield parameters.
... Nevertheless, this region includes the only sample from a grassland reserve in Alberta: the Suffield Grassland Reserve, about 250 km southeast of Calgary (Fig. 6) 6). Bourassa et al. (2008) identified 62 carabid species (Table 6) from a sample of 12,813 adults collected in pitfall traps in wheat, bean, and potato plots in 2000 and in 2003-2005. In nearby canola plots at this site during 2002, HC (unpublished) found 31 species (identified by S. Bourassa) from 1,068 adults. ...
... These practices included crop selection and rotations, tillage, reduced input (sustainable agriculture), and intercropping. In general, in plots subjected to the same practice over years, carabid activity density increased when pesticide inputs were reduced, but the studies have been confounded by differences in vegetation (Carcamo et al. 1995;Bourassa et al. 2008). Intercropping did not influence carabid activity or diversity patterns at Ellerslie or Lacombe, according to Carcamo et al. (1995) and Hummel et al. (2012), despite experimental evidence for P. melanarius' preference for an intercrop of pea-barley over monocultures of faba bean, barley, or fescue grass (Carcamo and . ...
Chapter
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Carabid beetles are among the best-known of Canada's insect families and are important indicators of environmental condition and change. Reasons for the relatively good level of knowledge include excellent taxonomic resources, a compendium of ecological information, and up-to-date checklists. The biology of carabid beetles is well understood in general terms, although for most species of the Prairies Ecozone, detailed studies of life cycles are lacking. Although pitfall traps are by far the most prevalent method of sampling, interpretation of trap catches without knowledge of life cycles can be misleading. Information from the literature on patterns of distribution, habitat use, and diet is tabulated for the 398 species of Carabidae (including Cicindelinae) reported to occur in the Prairies Ecozone, and more detailed information is presented on 15 tribes of particular interest. A brief summary is presented of 31 published and unpublished faunistic studies of carabid beetles in the Prairies Ecozone and in cultivated habitats in adjacent ecoregions. For 15 of these studies, relative abundance data are presented and discussed, and three studies, presenting previously unpublished information, are described in detail.
... Biodiversity tends to be higher in organic cropping systems in comparison with conventional systems, and this holds true for arthropod diversity (Bengtsson et al., 2005;Clark et al., 2006;Lundgren et al., 2006;Menalled et al., 2007;Bourassa et al., 2008;Shennan, 2008;Crowder et al., 2010Crowder et al., , 2012. Gains in biodiversity after transition to organic production are principally attributed to increased organic matter inputs into soil, a cessation of synthetic agrochemical applications, and increases in plant diversity. ...
... Epigeal arthropods are more abundant in cover crops than in bare control or fallow treatments (Lundgren et al., 2006;Prasifka et al., 2006;Pullaro et al., 2006;Shearin et al., 2008;Lundgren and Fergen, 2011). Crop type has a stronger effect on Carabidae richness, diversity and composition than management treatments (e.g., chemical inputs and tillage), which indicates that habitat suitability for soil dwelling predators may change from year to year depending on many factors (Bourassa et al., 2008). However, legacy effects on arthropod communities may also occur if the cropping system has long-lasting effects on weed-related resources (e.g., seeds and pollen), herbivorous prey, or the microclimate (Diehl et al., 2012). ...
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We conducted a cropping systems experiment in central Pennsylvania, USA, to determine the effects of initial cover crop species and soil management on the abundance and composition of the ground-dwelling arthropod community. We hypothesized that we would detect legacy effects of the cover crops planted in year 1 of a 3-yr crop sequence on the arthropod community in the subsequent 2 yrs, and that these effects would be influenced by the intensity of tillage. We compared four systems in a factorial combination of perennial sod and legumes or annual cereal grain and legume as initial cover crops and moldboard or chisel plow tillage implemented in soybeans followed by maize in the subsequent 2 yrs. The entire experiment was initiated twice in adjacent locations, starting in 2003 (Start 1) and 2004 (Start 2). We quantified soil arthropod activity-density and community composition and identified all arthropods to order or family, and the ground and tiger beetles (Coleoptera: Carabidae) to species. In Start 1, but not Start 2, arthropod activity-density increased with each year following implementation of organic management. We observed few legacy effects of cover crop or tillage intensity on arthropod activity-density. The composition of the soil arthropod community was primarily defined by the initial cover crop in the first year, and by the interaction between cover crop and tillage intensity in the second and third year. A legacy effect associated with a yr-1 cover crop of cereal rye was observed for Scarabaeidae beetles and Formicidae (ants) in yr 2 and Carabidae beetles in yr 3 of Start 1, but not Start 2. Weed indicators contributed significantly to the variation in the soil arthropod community that was explained by the environment in yr 2 in Start 1, and in yr 3 in both Starts. Our observations support the concept that both immediate and legacy effects of management shape arthropod communities during the organic transition period, suggesting that transitioning systems could be managed in ways that conserve or enhance natural enemy populations.
... The effects of organic farming on barley, oats, potatoes, wheat, potatoes, carrots, beans, faba bean, fescue, olives, corn, and tomato have been investigated (Dritschilo and Erwin 1982, Armstrong 1995, Carcamo et al. 1995, Berry et al. 1996, Ferris et al. 1996, Andersen and Eltun 2000, Bourassa et al. 2008. But for the rice ecosystem, the research has been rare. ...
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Planthoppers (Nilaparvata lugens, Sogatella furcifera, and Laodelphax striatellus) (Hemiptera: Delphacidae) are the most important pests affecting rice production. Pesticide spraying for its control may cause harmful effects on human health and the environment, especially the loss of biodiversity. The consequences of these changes on biodiversity and ecological services are well studied in tropical irrigated paddy fields, but are largely unknown in subtropical areas. Organic regime provides an environment-friendly method for biodiversity conservation; however, it is unclear whether this regime can suppress planthopper populations effectively in paddy fields. Consequently, we compared species richness, abundance, community structure, and evenness of natural enemies and planthoppers between organic and conventional rice fields (n = 35) distributed across four sites in China. The results showed that species richness was higher in organic fields than in conventional fields. Shannon index and evenness of predators and parasitoids were higher in most of the organic fields than their conventional counterparts. Furthermore, planthopper density showed a significant negative relationship with increased richness and evenness for both predators and parasitoids. These results underscore the notion that management regimes influence biodiversity in rice field. Most importantly, this has direct implications on the efficacy of natural pest control services rendered by predators and parasitoids associated with planthoppers in China and potentially other rice production regions in Asia.
... Compared with other studies on the NTOs Toschki et al. 2007), the size of our experimental plots was smaller, but relative to some published experiments in which the smallest plot was just 0.002 ha (Wolfenbarger et al. 2008), our plots were above average in size. Moreover, although the small plots cannot avoid ground-dwelling beetles travelling among different plots, similar as some studies which test successfully the effects of farming practices on carabid assemblages (Raworth et al. 2004;Bourassa et al. 2008), we also believe that differences in catches between transgenic and conventional cotton reliably reflected the effects of transgenic cotton on ground-dwelling beetle. Similar as other studies on the ground beetles in intensively cultivated fields in North China (Liu et al. 2010, very lower number of species and individuals were collected in our study. ...
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We compared the ground-dwelling beetle assemblages under four scenarios in which transgenic Bt (Cry 1Ac) cotton (33B), transgenic Bt (Cry 1Ac)+CpTI cotton (SGK321), conventional cotton (33), conventional cotton (Shiyuan 321) in North China. During the survey in two years (2009-2010), 24 ground beetle species were captured with pitfall traps in 20 plots which included five replicates for each cotton type. No significant difference was observed in the number of ground beetle species captured, activity density, evenness and Shannon-Wiener diversity among the four cotton varieties. Chlaenius posticalis was less abundant in transgenic Bt+CpTl cotton (SGK321) fields than its conventional cotton (Shiyuan 321), but more abundant in transgenic Bt cotton (33B) fields compared with its conventional cotton (33). There was no significant difference for other abundant species between in transgenic cotton and in conventional cotton fields. Based on non-metric multidimensional scaling (NMDS) analysis, ground-dwelling beetle assemblages were similar in transgenic and conventional cotton over the two years, but the ground-dwelling beetle assemblages in transgenic cotton 33B significantly differed from that in the conventional cotton (strain 33) in 2010. No strong evidence that the transgenic cotton effect on ground-dwelling beetle assemblages was found in this study.
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Nonnative species often transform local communities to the detriment of native species. Much of the existing invasion ecology research focuses on the effects of a few extremely impactful species, and it is less clear how nonnative species which are not causing economic or ecological impacts alter closely related natives at risk of being displaced. Filling these knowledge gaps is critical because consequences of nonnative species are likely to vary depending on taxonomic scale, functional trait, and spatial or temporal niche. We conducted a meta-analysis to evaluate how biodiversity of native Formicidae (ants), Carabidae (ground beetles), and Scolytinae (bark and ambrosia beetles) species changes across a gradient of pressure from nonnative confamilials. We calculated Hill numbers for each group from data presented in literature and correlated native diversity metrics to proportion of nonnative species. Species richness of native ants was significantly negatively correlated with proportions of nonnative ants, whereas bark and ambrosia beetle metrics showed a nonsignificant negative correlation. Nonnative ground beetles had neutral effects on diversity of native ground beetles. Resulting contrasting patterns of invasive species effects on natives suggest complex biotic and abiotic factors driving effects of nonnative species in these groups. Our results suggest that a few extreme examples (e.g., red imported fire ants) drive most of the changes seen in native arthropod communities. To accurately assess impacts of invaders on native arthropod diversity, baseline data are needed, and community analyses must consider diverse functional traits of native taxa and improve the depth and breadth of community sampling.
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The response of carabid beetles to differences in tillage and chemical use was studied using four matched pairs of sites. Abundance and species richness were significantly different between treatments, but four commonly used measures of diversity were relatively insensitive indicators of change. It is suggested that the use of diversity indices in impact assessment is redundant or, when used with ground beetles, misleading.