Non-agricultural Habitats Research Articles

Spatio-temporal variation in the demographic attributes of a generalist mesopredator

Human land-use practices have dramatically altered the composition and configuration of native habitats throughout many ecosystems. Within heterogeneous landscapes generalist predators often thrive, causing cascading effects on local biological communities, yet there are few data to suggest how attributes of fragmentation influence local population dynamics of these species. We monitored 25 raccoon (Procyon lotor) populations from 2004 to 2009 in a fragmented agricultural landscape to evaluate the influence of local and landscape habitat attributes on spatial and temporal variation in demography. Our results indicate that agricultural ecosystems support increased densities of raccoons relative to many other rural landscapes, but that spatial and temporal variation in demography exists that is driven by non-agricultural habitat attributes rather than the availability of crops. At the landscape scale, both density and population stability were positively associated with the size and contiguity of forest patches, while at the local scale density was positively correlated with plant diversity and the density of tree cavities. In addition, populations occupying forest patches with greater levels of plant diversity and stable water resources exhibited less temporal variability than populations with limited plant species complexity or water availability. The proportion of populations comprised of females was most strongly influenced by the availability of tree cavities and soft mast. Despite the abundance of mesopredators in heterogeneous landscapes, our results indicate that all patches do not contribute equally to the regional abundance and persistence of these species. Thus, a clear understanding of how landscape attributes contribute to variation in demography is critical to the optimization of management strategies.

Which habitats of European importance depend on agricultural practices?

The aim of this paper is to identify the habitat types listed in the Habitats Directive Annex I that require low-intensity agricultural management for their existence. We assessed the link between the Annex I habitat types and agricultural practices in order to identify habitat types that depend on the continuation of agricultural practices or whose existence is prolonged or spatially enlarged via blocking or reducing the secondary succession by agricultural activities. 63 habitat types that depend on or which can profit from agricultural activities—mainly grazing and mowing—were identified. They are classified into 2 groups: (1) habitats fully dependent on the continuation of agricultural management; (2) habitats partly dependent on the continuation of agricultural management. This paper also briefly discusses habitat types for which either doubts remain on their dependence on agricultural management, or the relation to extensive farming practices exists only in part of their area of distribution in Europe or under certain site conditions, respectively. Assessments of the conservation status of habitats of European Importance by 25 EU Member States in 2007 showed that habitats identified by us as depending on agricultural practices had a worse status than non-agricultural habitats.

The bucket and the searchlight: formulating and testing risk hypotheses about the weediness and invasiveness potential of transgenic crops

The bucket and the searchlight are metaphors for opposing theories of the growth of scientific knowledge. The bucket theory proposes that knowledge is gained by observing the world without preconceptions, and that knowledge emerges from the accumulation of observations that support a hypothesis. There are many problems with this theory, the most serious of which is that it does not appear to offer a means to distinguish between the many hypotheses that could explain a particular set of observations. The searchlight theory proposes that preconceptions are unavoidable and that knowledge advances through the improvement of our preconceptions - our hypotheses - by continuous criticism and revision. A hypothesis is a searchlight that illuminates observations that test the hypothesis and reveal its flaws, and knowledge thereby increases through the elimination of false hypotheses. Research into the risks posed by the cultivation of transgenic crops often appears to apply the bucket theory; many data are produced, but knowledge of risk is not advanced. Application of the searchlight theory, whereby risk assessments test hypotheses that transgenic crops will not be harmful, seems to offer a better way to characterise risk. The effectiveness of an environmental risk assessment should not be measured by the size of the bucket of observations on a transgenic crop, but by the power of the risk hypothesis searchlights to clarify the risks that may arise from cultivation of that crop. These points are illustrated by examples of hypotheses that could be tested to assess the risks from transgenic crops and their hybrids becoming weeds or invading non-agricultural habitats.

Expanding the paradigms of plant pathogen life history and evolution of parasitic fitness beyond agricultural boundaries.

How do pathogens, whether they parasitize plants or animals, acquire virulence to new hosts and resistance to the arms we deploy to control disease? The significance of these questions for microbiology and for society at large can be illustrated by the recent worldwide efforts to track and limit the emergence of human transmissible strains of swine and avian influenza virus and of multidrug-resistant lines of human pathogenic bacteria, and to restrain the spread of Ug99, a strain of stem rust of wheat. Recent research in medical epidemiology has elucidated the impact of pathogen ecology in environmental reservoirs on the evolution of novel or enhanced pathogen virulence. In contrast, the evolution of virulence in plant pathogens has been investigated from a predominantly agro-centric perspective, and has focused overwhelmingly on evolutionary forces related to interactions with the primary plant host. Here, we argue that current concepts from the field of medical epidemiology regarding mechanisms that lead to acquisition of novel virulence, biocide resistance, and enhanced pathogenic fitness can serve as an important foundation for novel hypotheses about the evolution of plant pathogens. We present numerous examples of virulence traits in plant pathogenic microorganisms that also have a function in their survival and growth in nonagricultural and nonplant habitats. Based on this evidence, we make an appeal to expand concepts of the life history of plant pathogens and the drivers of pathogen evolution beyond the current agro-centric perspective.

Effects of Natural Enemy Biodiversity on the Suppression of Arthropod Herbivores in Terrestrial Ecosystems

Claims about the role of predator diversity in maintaining ecosystem function and providing ecosystem services such as pest control are controversial, but evaluative tests are beginning to accumulate. Empirical and experimental comparisons of species-rich versus species-poor assemblages of entomophagous arthropods and vertebrates range from strong suppression to facilitative release of herbivorous arthropod prey. Top-down control can be strengthened when natural enemies complement each other, dampened by negative interactions, balanced by both factors, and driven by single influential species. A meta-analytic synthesis shows a significant overall effect of enemy richness increasing top-down control of herbivores, which is consistent in agricultural studies conducted in tropical versus temperate zones, in studies using caged versus open-field designs, but not so in nonagricultural habitats. Synthetic analyses address theory and help set precautionary policy for conserving ecological services broadly, while characterizing uncertainty associated with herbivore response to changes in enemy diversity.

Design of an ecologically-based IPM program for fruit flies (Diptera: Tephritidae) in Tanzania

Introduction . Studies to determine the pre-requisites for formulating an IPM program for fruit flies (Diptera: Tephritidae) were conducted in the Morogoro region, Central Tanzania, from 2004 to 2006. Specifically, studies aimed at determining the biodiversity of fruit flies, and their incidence and abundance in the surveyed region. Materials and methods . Adult flies were collected using McPhail traps baited with parapheromones (methyl eugenol, trimedlure and cue lure) and synthetic food baits (hydrolyzed yeast and three-component lure). Flies were also collected from infested fruits after incubation in the laboratory. A total of four sites and neighboring areas representing the three agro-ecological zones of Morogoro region were used. Results . Two key fruit fly pests were determined based on incidence in major fruits and their seasonal abundance. The invasive fruit fly, Bactrocera invadens Drew, Tsuruta and White, is the key pest in the low and medium altitude areas. On the other hand, the Natal fruit fly, Ceratitis rosa Karsch, is the key frugivorous pest in the high altitude areas. Discussion . Management programs of fruit flies need to focus on key pests, taking into consideration their breeding in the non-agricultural habitats. Components of such a program should include the Male Annihilation Technique (MAT), legislation, use of parapheromones and baits, farm hygiene and sanitation, quarantine, surveillance and postharvest treatment.

Population characteristics of house mice (Mus musculus) on southern Yorke Peninsula, South Australia

Seasonal population characteristics of house mice (Mus musculus), including the effect of season on body mass, were studied at Innes National Park, southern Yorke Peninsula. Mice were caught with Elliott traps, ear-notched, and released. Over 1550 trap-nights (January to December 2006, excluding May), 202 mice were caught. The overall capture success rate was 13.03 mice per 100 trap-nights. The recapture rate was 42.57%. Body mass of adult house mice varied significantly among seasons (P = 0.009). In particular, mouse body mass varied between autumn and winter (P = 0.018), and spring and winter (P = 0.023). The body mass of mice captured in autumn and then recaptured in winter was also significantly different (P = 0.006). This study is the first published for M. musculus population characteristics on Yorke Peninsula and adds to the relatively limited information available on house mouse populations in non-agricultural habitats.

Abundance of Native and Non-Native Lady Beetles (Coleoptera: Coccinellidae) in Different Habitats in Maine

Abstract Several studies suggest the possibility that non-native lady beetles may have replaced native lady beetles in some agricultural habitats. There is relatively little information, however, about lady beetle species composition outside of agricultural habitats. Evans (2004) suggested that native species have retreated to nonagricultural habitats in response to the arrival of non-native lady beetles (habitat compression hypothesis). To test this hypothesis, a survey of lady beetles was conducted in 2004 and 2005 in different habitats in Maine. From May to October, lady beetles were sampled in a variety of agricultural and nonagricultural habitats. In total, 3,487 and 2,903 lady beetles were collected in 2004 and 2005, respectively. Non-native lady beetles were found in a variety of habitats, including the habitats that would have likely served as a refuge for native species if the habitat compression hypothesis applied to the surveyed areas. Native species were found in a higher proportion in agricultural habitats compared with nonagricultural habitats and in very low numbers in all of the habitats surveyed. Hippodamia tredecimpunctata tibialis (Say) and Coccinella transversoguttata Brown, the two native species that were once dominant here, made up only 1.09 and 0.07% of the total lady beetles collected, respectively. In this survey, we failed to detect evidence that native lady beetles have retreated to nonagricultural habitats in response to the arrival of non-native lady beetles.

The life history of the plant pathogen Pseudomonas syringae is linked to the water cycle.

Pseudomonas syringae is a plant pathogen well known for its capacity to grow epiphytically on diverse plants and for its ice-nucleation activity. The ensemble of its known biology and ecology led us to postulate that this bacterium is also present in non-agricultural habitats, particularly those associated with water. Here, we report the abundance of P. syringae in rain, snow, alpine streams and lakes and in wild plants, in addition to the previously reported abundance in epilithic biofilms. Each of these substrates harbored strains that corresponded to P. syringae in terms of biochemical traits, pathogenicity and pathogenicity-related factors and that were ice-nucleation active. Phylogenetic comparisons of sequences of four housekeeping genes of the non-agricultural strains with strains of P. syringae from disease epidemics confirmed their identity as P. syringae. Moreover, strains belonging to the same clonal lineage were isolated from snow, irrigation water and a diseased crop plant. Our data suggest that the different substrates harboring P. syringae modify the structure of the associated populations. Here, we propose a comprehensive life cycle for P. syringae--in agricultural and non-agricultural habitats--driven by the environmental cycle of water. This cycle opens the opportunity to evaluate the importance of non-agricultural habitats in the evolution of a plant pathogen and the emergence of virulence. The ice-nucleation activity of all strains from snow, unlike from other substrates, strongly suggests that P. syringae plays an active role in the water cycle as an ice nucleus in clouds.

Effects of global environmental changes on weeds.

Abstract The global environment is projected to change significantly by the end of the 21st century, mainly as a result of intensifying human activities. Important environmental changes include rising carbon dioxide (CO 2 ) in the atmosphere, higher global average temperatures and altered precipitation patterns. As we strive to feed the rapidly increasing human population, it is of socioeconomic and ecological significance to understand the effects of environmental changes on the serious weeds that cause significant crop losses. This paper reviews the responses of 12 of the world's most serious agricultural weeds in response to global environmental changes. The weeds include species of a variety of growth forms as well as C 3 and C 4 photosynthetic pathways. In addition, we used meta-analytical techniques to synthesize the effects of elevated CO 2 on total biomass production for six of the most studied weeds. Our review found non-uniform biomass and reproductive responses to global changes among weeds. Consequently, the injuriousness of weeds to crops is likely to increase in some weeds, e.g., Chenopodium album , but decrease in others, e.g., Sorghum halepense . Because many of these agricultural weeds are also found in non-agricultural habitats, their differential responses to global changes will bear implications on community structure and species interactions in future natural ecosystems.

SPECIES AFFINITY AND INFRACOMMUNITY ORDINATION OF HELMINTHS OF LEPTODACTYLUS CHAQUENSIS (ANURA: LEPTODACTYLIDAE) IN TWO CONTRASTING ENVIRONMENTS FROM NORTHEASTERN ARGENTINA

One hundred seventy-two frogs (Leptodactylus chaquensis) were collected from November 2002 to November 2003, in agricultural (n = 132) and nonagricultural (n = 40) areas. Both sites are near the city of Corrientes, Argentina. The main goals of this study were as follows: (1) to determine the helminth parasite community in agricultural and nonagricultural habitats; (2) to analyze the relationships between helminth parasites and site of infection, frog body size, and gender; (3) to identify and examine covariation and association of helminth communities; and (4) to determine the mean richness and diversity of parasite communities. The helminth compound community of this amphibian species consisted of 24 species: 19 in agricultural habitats and 18 in nonagricultural habitats. The mean richness, mean diversity, and evenness of helminths were significantly different between the habitats (P < 0.05). The body size of the host was the important factor in determining parasite richness. Both habitats exhibited differences in community ordination. The helminth species in the 2 habitats exhibited the same interspecific relationships, although differences were observed in the intensity of infection.

Community-based surveillance of malaria vector larval habitats: a baseline study in urban Dar es Salaam, Tanzania.

BackgroundAs the population of Africa rapidly urbanizes it may be possible to protect large populations from malaria by controlling aquatic stages of mosquitoes. Here we present a baseline evaluation of the ability of community members to detect mosquito larval habitats with minimal training and supervision in the first weeks of an operational urban malaria control program.MethodsThe Urban Malaria Control Programme of Dar es Salaam recruited and provided preliminary training to teams of Community-Owned Resource Persons (CORPs) who performed weekly surveys of mosquito breeding sites. Two trained mosquito biologists accompanied each of these teams for one week and evaluated the sensitivity of this system for detecting potential Anopheles habitats.ResultsOverall, 42.4% of 986 habitats surveyed by an inspection team had previously been identified by CORPs. Agricultural habitats were detected less often than other habitats (30.8% detected, Odds Ratio [95%CI] = 0.46 [0.29–0.73], P = 0.001). Non-agricultural artificial habitats were less suitable than other habitats (29.3% occupancy, OR = 0.69 [0.46–1.03], P = 0.066) but still constituted 45% (169/289) of occupied habitats because of their abundance (51 % of all habitats).ConclusionThe levels of coverage achieved by modestly trained and supported CORPs at the start of the Dar es Salaam UMCP were insufficient to enable effective suppression of malaria transmission through larval control. Further operational research is required to develop surveillance systems that are practical, affordable, effective and acceptable so that community-based integrated vector management can be implemented in cities across Africa.

Association between Wildlife and Agriculture: Underlying Mechanisms and Implications in Burrowing Owls

Western burrowing owls (Athene cunicularia hypugaea) are endangered in Canada and several western U.S. states. Population declines have been linked with control measures aimed at burrowing mammals and loss of nesting habitat. The owls frequently associate with irrigated agriculture throughout portions of their western U.S. range. To determine potential factors driving the association of burrowing owls with agriculture, we examined availability of suitable nest burrows (burrow availability hypothesis), abundance of potential prey (prey availability hypothesis), and predation of nest burrows (predation hypothesis) for owls nesting in the Snake River Birds of Prey National Conservation Area in southwestern Idaho during 2001–2002. Nest burrow availability did not differ between agricultural and nonagricultural habitats, and occupancy rates of owls in artificial burrows were greater near agriculture. More rodent prey species were live-trapped in agricultural habitat compared with nonagricultural habitat, and there was no difference in relative abundance of prey between habitat types. Pellet remains indicated greater abundance and biomass of prey being consumed in agricultural habitat compared with nonagricultural habitat. Finally, predation rates of dummy nests in agricultural and nonagricultural habitat did not differ. These findings allow us to reject the burrow availability and predation hypotheses, while the prey availability hypothesis remains tenable. Thus, burrowing owls may nest near irrigated agriculture in southwestern Idaho because of increased diversity or availability of prey. We suggest that research is needed to determine how widespread this prey availability relationship may be and how management of burrowing owls in agricultural landscapes may take advantage of this apparent rich prey resource.

Habitat Selection by the Introduced Biological Control Agent &lt;I&gt;Trichogramma ostriniae&lt;/I&gt; (Hymenoptera: Trichogrammatidae) and Implications for Nontarget Effects

Trichogrammatid wasps are used widely as biocontrol agents against a variety of lepidopteran pests. However, the broad physiological host range of most Trichogramma species raises concerns about the potential impact of released wasps on nontarget Lepidoptera. If wasps exhibit a preference for agricultural over nonagricultural habitats, this could lessen the risk for many nontarget species that occur primarily in natural habitats. In this study, we examined the habitat selection behavior of Trichogramma ostriniae Pang and Chen, an Asian species that has shown considerable promise in the United States as a biological control agent against the European corn borer, Ostrinia nubilalis Hubner (Lepidoptera: Crambidae). On two different farms, we released wasps in a border area between corn (Zea mays L.) and natural forest, at locations equidistant to the two habitats. We monitored wasp movement for 4 wk using sticky cards placed up to 30 m inside each habitat. The results showed that T. ostriniae wasps have no inherent avoidance of entering forest habitat. Overall, however, corn habitat was more attractive to the wasps than forest habitat. The relative attractiveness of corn versus forest habitat also increased over time. We discuss our results on T. ostriniae habitat selection behavior within the context of information on T. ostriniae physiological host range and searching efficiency within different habitats and address the implications for risk to nontarget forest Lepidoptera.

Decline of Northern Lapwing Vanellus vanellus breeding on arable farmland in relation to loss of spring tillage

Capsule A decrease in the area of spring tillage was not the primary cause of a decline to extinction of a local breeding population of Lapwing. Aims This study tested whether or not the availability of spring tillage limited the number of Lapwing settling on arable land and resulted in a population decline, the ‘spring tillage’ hypothesis. Two predictions from the hypothesis were tested: (i) that between-year differences in the numbers of Lapwing settling on tilled land tracked between-year differences in the area of spring tillage; (ii) that the saturation density was reached on tilled land in each year when birds were present. Methods Breeding birds, nests and fledged young were counted annually on arable land and adjacent grassland and non-agricultural habitats on part of the North Downs, Hampshire, between 1981 and 1995, except in 1987 and 1988. Data on crop development and field attributes were collected concurrently. Results The number of breeding pairs decreased to zero between 1981 and 1995. Over the same period, the area of spring tillage decreased by 40%. Tillage availability partially determined the distribution of fields used for nesting, but there was no evidence that it limited the number of Lapwing settling on tilled land, except in 1984 and, possibly, 1982. Neither prediction of the ‘spring tillage’ hypothesis was upheld. Annual production of fledged young was not sufficient to replace annual losses. Conclusion The decrease in the area of spring tillage did not account wholly for the decline in the numbers of Lapwing nesting on arable land in the study area. It is likely that the decline was due primarily to very low breeding success, which was not compensated by immigration.

Spatial and Seasonal Patterns of Bird Communities in Italian Agroecosystems

Abstract: Despite agricultural landscapes covering almost 60% of the total land area of Italy, knowledge of the effects of agriculture and its intensification on bird communities is still scarce. I analyzed the effects of land uses on bird diversity and community structure in different farmland habitats of lowland northwestern Italy. I surveyed breeding and overwintering birds with a hierarchically nested sampling design and used generalized linear and mixed models to investigate the relationships between the diversity and abundance of birds and habitat or landscapes attributes. The effects of agriculture on α avian diversity varied with season and spatial scale, whereas nonagricultural habitats (long‐term fallows or woodlands) had a generally positive effect that was constant throughout time and space. As the amount of woodland habitat increased, spatial turnover (β diversity) of breeding birds decreased. Arable landscapes supported low levels of avian diversity throughout the year but were favored by emblematic farmland birds that have declined severely in Europe and in the study area. Farmland birds (40% of which are experiencing population declines) were more abundant or foraged more frequently in the less‐disturbed habitat types such as fallows, grasslands, and winter stubbles and tended to avoid the prevailing cultivations (maize, vineyard, and wheat). Landscape simplification, the expansion of maize cultivation, winter plowing practices, and the conversion of highly diverse grasslands to tilled lands are likely to be responsible for the local decline of most farmland species (Skylark[Alauda arvensis], Starling[Sturnus vulgaris], buntings[Emberiza spp.], and wagtails[Motacilla spp.]) and for the increase of birds that are turning into agricultural pests (Hooded Crow[Corvus corone cornix]).

Risks and consequences of gene flow from herbicide‐resistant crops: canola (Brassica napus L) as a case study

Data from the literature and recent experiments with herbicide-resistant (HR) canola (Brassica napus L) repeatedly confirm that genes and transgenes will flow and hybrids will form if certain conditions are met. These include sympatry with a compatible relative (weedy, wild or crop), synchrony of flowering, successful fertilization and viable offspring. The chance of these events occurring is real; however, it is generally low and varies with species and circumstances. Plants of the same species (non-transgenic or with a different HR transgene) in neighbouring fields may inherit the new HR gene, potentially generating plants with single and multiple HR. For canola, seed losses at harvest and secondary dormancy ensures the persistence over time of the HR trait(s) in the seed bank, and the potential presence of crop volunteers in subsequent crops. Although canola has many wild/weedy relatives, the risk of gene flow is quite low for most of these species, except with Brassica rapa L. Introgression of genes and transgenes in B rapa populations occurs with apparently little or no fitness costs. Consequences of HR canola gene flow for the agro-ecosystem include contamination of seed lots, potentially more complex and costly control strategy, and limitations in cropping system design. Consequences for non-agricultural habitats may be minor but appear largely undocumented.

Movement of greenhouse whitefly and its predators between in- and outside of Mediterranean greenhouses

Some Mediterranean greenhouses are inserted in a landscape of open fields, non-agricultural and woody habitats. Both the greenhouse whitefly and its polyphagous predators are well adapted to protected and field crops. The phenology and intensity of whitefly and predator exchange between greenhouses and surrounding habitats were investigated in two different zones of northern Spain. Whiteflies colonised greenhouses earlier and built up high populations before predators established in the crop. Both the abundance of vegetation and the topographic characteristics of the environment surrounding greenhouses affected the numbers of predators entering the tomato crop through the greenhouse openings whereas whitefly migration was only affected by the topography around the greenhouses. These results are discussed in terms of biological control of greenhouse pests by naturally occurring predators.

Temporal and spatial overlap between monarch larvae and corn pollen.

To assess the likelihood that monarch larvae will be exposed to Bacillus thuringiensis (Bt) pollen, we studied milkweed and monarch densities in habitats which comprise much of the land available to breeding monarchs, e.g., cornfields, cornfield edges, other agricultural fields, and nonagricultural areas, in four regions of the monarch breeding range. We found that monarchs use milkweed in cornfields throughout their breeding season, and that per plant densities are as high or higher in agricultural habitats as in nonagricultural habitats. As a result of the prevalence of agricultural land, most of the monarchs produced in the upper Midwest are likely to originate in cornfields or other agricultural habitats. There was a greater temporal overlap between susceptible monarchs and corn anthesis in the northern than the southern part of the summer breeding range, because of earlier pollen shed in the south. The importance of agricultural habitats to monarch production suggests that, regardless of the impact of genetically modified crops, agricultural practices such as weed control and foliar insecticide use could have large impacts on monarch populations.

Indirect interactions in aphid–parasitoid communities

AbstractIndirect interactions between populations of different species can be important in structuring natural communities. Indirect effects are either mediated by changes in population densities (trophic or density‐mediated effects) or by changes in the behavior of species that are not trophically connected (behavioral or trait‐mediated effects). We reviewed the literature on aphids and their parasitoids to explore the various possible indirect interactions that can occur in such communities. The review was motivated by our study of a particular aphid–parasitoid community in a natural (i.e., nonagricultural) habitat, and by the wealth of information that exists about aphid–parasitoid systems in agricultural settings. We focused our review on aphid–parasitoid interactions, but considered how these were influenced by the other aphid natural enemies and also by aphid mutualists and host plants. We conclude that indirect effects are likely to have a major effect in structuring aphid–parasitoid communities, and that the latter are a valuable model system for testing ideas about community interactions.