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      Bats Track and Exploit Changes in Insect Pest Populations

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          Abstract

          The role of bats or any generalist predator in suppressing prey populations depends on the predator's ability to track and exploit available prey. Using a qPCR fecal DNA assay, we document significant association between numbers of Brazilian free-tailed bats ( Tadarida brasiliensis) consuming corn earworm (CEW) moths ( Helicoverpa zea) and seasonal fluctuations in CEW populations. This result is consistent with earlier research linking the bats' diet to patterns of migration, abundance, and crop infestation by important insect pests. Here we confirm opportunistic feeding on one of the world's most destructive insects and support model estimates of the bats' ecosystem services. Regression analysis of CEW consumption versus the moth's abundance at four insect trapping sites further indicates that bats track local abundance of CEW within the regional landscape. Estimates of CEW gene copies in the feces of bats are not associated with seasonal or local patterns of CEW abundance, and results of captive feeding experiments indicate that our qPCR assay does not provide a direct measure of numbers or biomass of prey consumed. Our results support growing evidence for the role of generalist predators, and bats specifically, as agents for biological control and speak to the value of conserving indigenous generalist predators.

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          Molecular analysis of predation: a review of best practice for DNA-based approaches.

          Molecular analysis of predation, through polymerase chain reaction amplification of prey remains within the faeces or digestive systems of predators, is a rapidly growing field, impeded by a lack of readily accessible advice on best practice. Here, we review the techniques used to date and provide guidelines accessible to those new to this field or from a different molecular biology background. Optimization begins with field collection, sample preservation, predator dissection and DNA extraction techniques, all designed to ensure good quality, uncontaminated DNA from semidigested samples. The advantages of nuclear vs. mitochondrial DNA as primer targets are reviewed, along with choice of genes and advice on primer design to maximize specificity and detection periods following ingestion of the prey by the predators. Primer and assay optimization are discussed, including cross-amplification tests and calibratory feeding experiments. Once primers have been made, the screening of field samples must guard against (through appropriate controls) cross contamination. Multiplex polymerase chain reactions provide a means of screening for many different species simultaneously. We discuss visualization of amplicons on gels, with and without incorporation of fluorescent primers. In more specialized areas, we examine the utility of temperature and denaturing gradient gel electrophoresis to examine responses of predators to prey diversity, and review the potential of quantitative polymerase chain reaction systems to quantify predation. Alternative routes by which prey DNA might get into the guts of a predator (scavenging, secondary predation) are highlighted. We look ahead to new technologies, including microarrays and pyrosequencing, which might one day be applied to this field.
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            Facts from feces revisited.

            Obtaining information on wild mammal populations has been a long-standing logistical problem. However, an array of non-invasive techniques is available, including recently developed molecular genetic techniques for the analysis of feces (molecular scatology). A battery of non-invasive, molecular approaches can be used on feces, which in conjunction with conventional analysis are potentially useful for assesing genetic structure, demography and life history of mammals. Several technical problems reman before large-scale studies of feces can be undertaken productively, but already studies are providing insight into population subdivision, food habits, reproduction, sex ratio and parasitology of free-ranging populations.
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              Species on the menu of a generalist predator, the eastern red bat (Lasiurus borealis): using a molecular approach to detect arthropod prey.

              One of the most difficult interactions to observe in nature is the relationship between a predator and its prey. When direct observations are impossible, we rely on morphological classification of prey remains, although this is particularly challenging among generalist predators whose faeces contain mixed and degraded prey fragments. In this investigation, we used a polymerase chain reaction and sequence-based technique to identify prey fragments in the guano of the generalist insectivore, the eastern red bat (Lasiurus borealis), and evaluate several hypotheses about prey selection and prey defences. The interaction between bats and insects is of significant evolutionary interest because of the adaptive nature of insect hearing against echolocation. However, measuring the successes of predator tactics or particular prey defences is limited because we cannot normally identify these digested prey fragments beyond order or family. Using a molecular approach, we recovered sequences from 89% of the fragments tested, and through comparison to a reference database of sequences, we were able to identify 127 different species of prey. Our results indicate that despite the robust jaws of L. borealis, most prey taxa were softer-bodied Lepidoptera. Surprisingly, more than 60% of the prey species were tympanate, with ears thought to afford protection against these echolocating bats. Moths of the family Arctiidae, which employ multiple defensive strategies, were not detected as a significant dietary component. Our results provide an unprecedented level of detail for the study of predator-prey relationships in bats and demonstrate the advantages which molecular tools can provide in investigations of complex ecological systems and food-web relationships.
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                Author and article information

                Contributors
                Role: Editor
                Journal
                PLoS One
                PLoS ONE
                plos
                plosone
                PLoS ONE
                Public Library of Science (San Francisco, USA )
                1932-6203
                2012
                31 August 2012
                : 7
                : 8
                : e43839
                Affiliations
                [1 ]Department of Ecology and Evolutionary Biology, University of Tennessee, Knoxville, Tennessee, United States of America
                [2 ]Areawide Pest Management Research Unit, USDA-ARS, College Station, Texas, United States of America
                [3 ]Department of Microbiology, University of Tennessee, Knoxville, Tennessee, United States of America
                [4 ]Department of Mathematics, Computer Science, and Physics, Capital University, Columbus, Ohio, United States of America
                [5 ]Centre for Ecology and Conservation Biology, Department of Biology, Boston University, Boston, Massachusetts, United States of America
                University of Western Ontario, Canada
                Author notes

                Competing Interests: The authors have declared that no competing interests exist.

                Conceived and designed the experiments: GFM JKW. Performed the experiments: GFM JKW VAB ME. Analyzed the data: GFM JKW VAB PF. Contributed reagents/materials/analysis tools: GFM JKW ME THK. Wrote the paper: GFM JKW VAB PF THK.

                Article
                PONE-D-12-14073
                10.1371/journal.pone.0043839
                3432057
                22952782
                7dc0f585-bdbb-4e27-ad52-41ccf55d1ddf
                Copyright @ 2012

                This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

                History
                : 15 May 2012
                : 30 July 2012
                Page count
                Pages: 10
                Funding
                This work was supported by NSF Grant EIA-0326483 (TH Kunz, PI, M Betke, GF McCracken, P Morton, and JK Westbrook, CoPI's); Bat Conservation International; and The University of Tennessee, Knoxville. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.
                Categories
                Research Article
                Agriculture
                Pest Control
                Integrated Control
                Biology
                Ecology
                Agroecology
                Agronomic Ecology
                Behavioral Ecology
                Conservation Science
                Terrestrial Ecology
                Evolutionary Biology
                Behavioral Ecology
                Zoology
                Animal Behavior
                Entomology
                Mammalogy

                Uncategorized
                Uncategorized

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