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David R. Towns - One of the best experts on this subject based on the ideXlab platform.
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eradications as reverse invasions lessons from pacific rat Rattus exulans removals on new zealand islands
Biological Invasions, 2009Co-Authors: David R. TownsAbstract:Eradications of kiore or Pacific rats (Rattus exulans) from islands around New Zealand have been followed by responses from resident species of coastal plants, invertebrates, reptiles and seabirds. These responses are compared with an invasion by ship rats (Rattus Rattus), which devastated populations of invertebrates, birds and bats. Post-eradication responses only approximate the effects of invasions because recovery is limited to the residual pool of native species. Greater effects of kiore are indicated by adding incompatible species confined to rat-free locations. The extended list includes at least 15 species of invertebrates, two species of frogs, tuatara (Sphenodon punctatus), 11 species of lizards and 9 species of seabirds. The analyses indicate direct and indirect effects of kiore similar to those reported after ship rat invasions. This is despite indications from the literature that kiore are the least damaging of the three commensal rat species.
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responses of tuatara sphenodon punctatus to removal of introduced pacific rats from islands
Conservation Biology, 2007Co-Authors: David R. Towns, Alison Cree, Donald G Newman, Richard G Parrish, Claudine L Tyrrell, Graham T Ussher, A H Whitaker, Ian WestbrookeAbstract:: Invasive mammalian predators such as rats are now widespread on islands, but hypotheses about their effects have rarely been tested. Circumstantial evidence from New Zealand indicates that, when introduced to islands, Pacific rats (Rattus exulans) have negative effects on endemic plants, invertebrates, birds, and reptiles, including the tuatara (Sphenodon punctatus). We tested the effects of Pacific rats on tuatara by comparing the demographic structure and body condition of tuatara populations on three islands before and after removal of rats and on a fourth island where rats remained. In the presence of rats, juvenile tuatara constituted on average 0–5% of the sample tuatara populations. When Pacific rats were removed after at least 200 years' occupancy, the proportion of juvenile tuatara increased 3.5- to 17-fold and body condition of adult males and females also improved (sometimes dramatically). We predict that, unless Pacific rats are removed from Taranga Island, the tuatara population will collapse because of low population density and the lack of juvenile recruitment. Our results demonstrate that when invasive species exert subtle effects on recruitment and body condition, the effects on populations of long-lived endemic species may only become apparent long after the invasion. Resumen: Actualmente, los depredadores mamiferos invasores, como las ratas, estan ampliamente extendidos en islas, pero las hipotesis sobre sus efectos han sido probadas pocas veces. Evidencia circunstancial de Nueva Zelanda indica que, cuando son introducidas a islas, las ratas del Pacifico (Rattus exulans) tienen un efecto negativo sobre plantas, invertebrados, aves y reptiles endemicos, incluyendo el tuatara (Sphenodon punctatus). Probamos los efectos de ratas del Pacifico sobre tuatara mediante la comparacion de la estructura demografica y la condicion corporal de poblaciones de tuatara en tres islas antes y despues de la remocion de ratas y en una cuarta isla donde permanecian las ratas. En la presencia de ratas, tuatara juveniles constituian, en promedio, 0–5% de las poblaciones de tuatara. Cuando las ratas eran removidas despues de por lo menos 200 anos de ocupacion, la proporcion de tuatara juveniles incremento entre 3.5 y 17 veces y la condicion corporal de los machos y hembras adultas tambien mejoro (algunas veces dramaticamente). Pronosticamos que, a menos que las ratas del Pacifico sean removidas de la Isla Taranga, las poblaciones de tuatara se colapsaran debido a una densidad poblacional baja y por la ausencia de reclutamiento de juveniles. Nuestros resultados demuestran que cuando las especies invasoras ejercen efectos sutiles sobre el reclutamiento y la condicion corporal, los efectos sobre las poblaciones de especies endemicas longevas se vuelven aparentes mucho tiempo despues de la invasion.
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changes in habitat use by lizards on a new zealand island following removal of the introduced pacific rat Rattus exulans
Pacific Conservation Biology, 1995Co-Authors: David R. TownsAbstract:On Korapuki Island (Mercury Islands group, northeastern New Zealand) lizard capture frequencies increased following the removal of Pacific Rats Rattus exulans in 1986 and rabbits Oryctolagus cuniculus in 1987. This increase was dominated by diurnal Shore Skinks Oligosoma smithi. Increases in Shore Skink captures were proportionally greatest where beach particle sizes exceeded 25 cm dia (50-fold in five years). In sites where particles were large the Shore Skink population became dominated by adults. These changes in Shore Skink distribution and size were found in areas unlikely to have been either directly or indirectly affected by rabbits. The changes are therefore attributable to removal of Pacific Rats which apparently had greatest effect on lizards where interstices between rocks allowed the rats access. The selective natural recovery of Shore Skink populations on Korapuki Island indicates that the effects of Pacific Rats on island lizard faunas depends not only on the presence of refuge areas, such as rocky beaches, but also on the particle sizes within them.
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response of lizard assemblages in the mercury islands new zealand to removal of an introduced rodent the kiore Rattus exulans
Journal of The Royal Society of New Zealand, 1991Co-Authors: David R. TownsAbstract:Predation by kiore (Rattus exulans) has long been assumed to reduce the abundance and species diversity of lizards on islands around New Zealand. However, proof of this is hard to find, partly because it is difficult to compare lizard populations on different islands. In this paper I review methods for obtaining contemporaneous samples of lizard populations, compare the relative abundances of lizards on islands with and without kiore, and describe the responses of lizard populations to the eradication of kiore. On islands in the Mercury Group, northern New Zealand, kiore are absent from Middle I., present on Stanley I., and formerly present (now eradicated) from Korapuki I. Comparison of islands with kiore versus those without kiore shows that there are differences in addition to those of species richness of lizards. On Middle I. in 1986 and 1987, 65% of the lizard biomass comprised nocturnal/crepuscular species, whereas these species represented only 2% of the biomass on Korapuki I. The circumstantial di...
Patrick V Kirch - One of the best experts on this subject based on the ideXlab platform.
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restructuring of nutrient flows in island ecosystems following human colonization evidenced by isotopic analysis of commensal rats
Proceedings of the National Academy of Sciences of the United States of America, 2018Co-Authors: Jillia A Swif, Patrick Roberts, Nicole Oivi, Patrick V KirchAbstract:The role of humans in shaping local ecosystems is an increasing focus of archaeological research, yet researchers often lack an appropriate means of measuring past anthropogenic effects on local food webs and nutrient cycling. Stable isotope analysis of commensal animals provides an effective proxy for local human environments because these species are closely associated with human activities without being under direct human management. Such species are thus central to nutrient flows across a range of socionatural environments and can provide insight into how they intersected and transformed over time. Here we measure and compare stable carbon and nitrogen isotope data from Pacific rat (Rattus exulans) skeletal remains across three Polynesian island systems [Mangareva, Ua Huka (Marquesas), and the Polynesian Outlier of Tikopia] during one of the most significant cases of human migration and commensal introduction in prehistory. The results demonstrate widespread δ15N declines across these islands that are associated with human land use, intensification, and faunal community restructuring. Local comparison of rat stable isotope data also tracks human activities and resource availability at the level of the settlement. Our results highlight the large-scale restructuring of nutrient flows in island ecosystems that resulted from human colonization and ecosystem engineering activities on Pacific islands. They also demonstrate that stable isotope analysis of often-ignored commensal taxa can provide a tool for tracking human land use and environmental effects.
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stable isotope analysis of pacific rat Rattus exulans from archaeological sites in mangareva french polynesia the use of commensal species for understanding human activity and ecosystem change
Environmental Archaeology, 2017Co-Authors: Jillian Swift, Melanie J Miller, Patrick V KirchAbstract:Stable carbon and nitrogen isotope analysis was applied to archaeological specimens of the commensal Pacific rat (Rattus exulans) to investigate nutrient fluxes in prehistoric socio-ecosystems on Mangareva (Gambier Islands) and their implications for anthropogenic environmental change. The Pacific rat – ubiquitous in Polynesian archaeological sites – is characterised by low dietary selectivity and a limited home range, making it an ideal candidate for assessing changes in island food webs. Temporal trends in diet-derived bone collagen δ13C and δ15N values are assessed from three sites: The Onemea Site, Taravai Island (TAR-6), Nenega-iti Rockshelter, Agakauitai Island (AGA-3) and Kitchen Cave Rockshelter, Kamaka Island (KAM-1). An overall trend of decreasing δ15N values in rat bone collagen over time reflects archipelago-wide changes to island socio-ecosystems most likely resulting from seabird population declines. Differences in site function and human activity may have also influenced local rat dietary p...
Julien Claude - One of the best experts on this subject based on the ideXlab platform.
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Effects of mammarenavirus infection (Wēnzhōu virus) on the morphology of Rattus exulans
Infection Genetics and Evolution, 2018Co-Authors: Jean Artois, Serge Morand, Kim Blasdell, Philippe Buchy, Veasna Duong, Vibol Hul, Julien ClaudeAbstract:The circulation of mammarenaviruses in rodent populations of the Mekong region has recently been established, with a genetic variant of Wēnzhōu virus, Cardamones virus, detected in two Rattus species. This study tests the potential teratogenic effects of Wēnzhōu infection on the development of a Murid rodent, Rattus exulans. Using direct virus detection, morphological records and comparative analyses, a link was demonstrated between host infection status and host morphologies (the spleen irrespective of weight, the skull shape and the cranial cavity volume) at the level of the individual (females only). This study demonstrates that mammarenavirus infections can impact natural host physiology and/or affect developmental processes. The presence of an infecting micro-parasite during the development of the rat may lead to a physiological trade-off between immunity and brain size. Alternatively, replication of virus in specialized organs can result in selective morphologic abnormalities and lesions.
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log shape ratios procrustes superimposition elliptic fourier analysis three worked examples in r
Hystrix-italian Journal of Mammalogy, 2013Co-Authors: Julien ClaudeAbstract:This publication uses and presents R routines that perform various morphometric analysis in the context of rodent systematics. The morphological variation of two commensal rat species, Rattus exulans and Rattus tanezumi , is analysed and the potential for discrimination between the two is assessed. Specimens were trapped in three localities of Northern and North-Eastern Thailand. Shape and size variation are analysed in regards to sex, species, and geographical effects with various morphometric methods: log-shape ratios on body measurements, elliptic Fourier analyses on teeth outlines, Procrustes superimposition on skull coordinates. Both species are significantly different; however, the discrimination seems to be better on skull Procrustes coordinates and on teeth size than on other morphometric data set. Where different allometries exist between species and where species differ in size and shape, it is shown that filtering allometry using the approach of Burnaby (1966) can improve the discrimination between species. Sex size and shape dimorphism is reduced by comparison to interindividual variation. Shape variation varies between sampled localities for Rattus exulans , this is not the case for Rattus tanezumi . This pattern is possibly related to the more commensal life of R. exulans . Download the complete "Yellow Book" on "Virtual Morphology and Evolutionary Morphometrics in the new millenium".
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cytonuclear discordance among southeast asian black rats Rattus Rattus complex
Molecular Ecology, 2013Co-Authors: Julien Claude, Yannick Chaval, Vincent Herbreteau, Marie Pages, Eric Bazin, Maxime Galan, Johan Michaux, Sylvain PiryAbstract:Black rats are major invasive vertebrate pests with severe ecological, economic and health impacts. Remarkably, their evolutionary history has received little attention, and there is no firm agreement on how many species should be recognized within the black rat complex. This species complex is native to India and Southeast Asia. According to current taxonomic classification, there are three taxa living in sympatry in several parts of Thailand, Cambodia and Lao People's Democratic Republic, where this study was conducted: two accepted species (Rattus tanezumi, Rattus sakeratensis) and an additional mitochondrial lineage of unclear taxonomic status referred to here as ‘Rattus R3’. We used extensive sampling, morphological data and diverse genetic markers differing in rates of evolution and parental inheritance (two mitochondrial DNA genes, one nuclear gene and eight microsatellite loci) to assess the reproductive isolation of these three taxa. Two close Asian relatives, Rattus argentiventer and Rattus exulans, were also included in the genetic analyses. Genetic analyses revealed discordance between the mitochondrial and nuclear data. Mitochondrial phylogeny studies identified three reciprocally monophyletic clades in the black rat complex. However, studies of the phylogeny of the nuclear exon interphotoreceptor retinoid-binding protein gene and clustering and assignation analyses with eight microsatellites failed to separate R. tanezumi and R3. Morphometric analyses were consistent with nuclear data. The incongruence between mitochondrial and nuclear (and morphological) data rendered R. tanezumi/R3 paraphyletic for mitochondrial lineages with respect to R. sakeratensis. Various evolutionary processes, such as shared ancestral polymorphism and incomplete lineage sorting or hybridization with massive mitochondrial introgression between species, may account for this unusual genetic pattern in mammals.
I A E Atkinson - One of the best experts on this subject based on the ideXlab platform.
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depression of tree recruitment by the pacific rat Rattus exulans peale on new zealand s northern offshore islands
Biological Conservation, 2002Co-Authors: D J Campbell, I A E AtkinsonAbstract:Recruitment of tree populations on islands with and without Rattus exulans Peale, and recruitment changes on islands before and after rat eradication are compared using size-class analyses. Seedling establishment in rat-proof exclosures was compared with adjacent control areas. R. exulans depress recruitment of 11 species of coastal trees among 17 species studied: Coprosma macrocarpa, Coprosma repens, Dysoxylum spectabile, Melicytus novae-zelandiae, Nestegis apetala, Pisonia brunoniana, Pittosporum crassifolium, Pouteria costata, Pseudopanax lessonii, Rhopalostylis sapida and Streblus banksii; some to the point of local extinction. Where R. exulans has reached small islands supporting dense colonies of petrels (Procellariidae, Pelecanoididae), the numbers of some plant and animal species have been greatly reduced. Successional pathways in vegetation recovering on larger islands formerly occupied by Maori, have also been altered by this rat. Similar effects by R. exulans on the plant life of Pacific islands are probable considering the length of time R. exulans has been present.
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effects of kiore Rattus exulans peale on recruitment of indigenous coastal trees on northern offshore islands of new zealand
Journal of The Royal Society of New Zealand, 1999Co-Authors: D J Campbell, I A E AtkinsonAbstract:Possible effects of kiore (Rattus exulans) on selected indigenous tree species in coastal forests ot northern New Zealand are surveyed from recent field sampling and a literature review Recruitment rates are compared on islands with and without kiore (i) on the same island before or at the time of rat eradication compared with recruitment some years later, and (II) on geographically separated islands with and without kiore In addition kiore‐proof exclosurcs enabled some comparisons to be made of seed germination and survival in the presence and absence of kiore There is evidence that kiore have substantially reduced recruitment of Pittosporum crassifohum, Poutena costata Streblus banksu, and Nestegis apetala by eating the seed Seed consumption and/or depressed recruitment is demonstrated for Rhopalostyhs sapida, Vitex lucens and Pisoma brunoniana, but the extent ot recruitment reduction is not yet clear No depressive effect by kiore on the recruitment ot some species, including Dysoxylum spectabde Beilchm...
Rodger J Sparks - One of the best experts on this subject based on the ideXlab platform.
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dating of Rattus exulans and bird bone from pleasant river otago new zealand radiocarbon anomalies from diet
Journal of The Royal Society of New Zealand, 2001Co-Authors: Nancy Beavanathfield, Rodger J SparksAbstract:Radiocarbon ages of Rattus exulans bone recovered from the Pleasant River, Otago, archaeological site were originally rejected on the basis of 14C variability allegedly caused by laboratory processing Subsequent work revealed no burial contaminant that could have affected the results on bone protein as processed We present the analysis of bone from seven bird species at the Pleasant River site which showed that marshland fowl also had up to 300 yr radiocarbon variation in their ages but maintained terrestrial range δ13C and δ15N values The apparent dietary effect that offsets marshland fowl 14C ages at Pleasant River suggested there was a similar diet based cause for the anomalous radiocarbon ages for some R exulans at the site rather than a laboratory contamination or processing effect
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dating of Rattus exulans bone from pleasant river otago new zealand testing the effect of burial contamination
Journal of The Royal Society of New Zealand, 2001Co-Authors: Nancy Beavanathfield, Rodger J SparksAbstract:Burial contamination can produce age anomalies in radiocarbon-d ated bone It is possible to test for the presence and effect of the in situ contamination — humic and fulvic acids, transferred in soil pore waters — for a specific site In this study, we examined the possibility that a previously unidentified and ineffectively removed burial contaminant affected radiocarbon ages from Rattus exulans bone at the Pleasant River archaeological site We found no evidence for such contamination and illustrated that testing in situ contamination effects should be considered before invoking same as a cause of radiocarbon anomalies in bone
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reliability of bone gelatin ams dating Rattus exulans and marine shell radiocarbon dates from pauatahanui midden sites in wellington new zealand
Radiocarbon, 1999Co-Authors: Nancy Beavan Athfield, Bruce Mcfadgen, Rodger J SparksAbstract:A suite of 6 bone gelatin accelerator mass spectrometry (AMS) radiocarbon dates for Rattus exulans Peale and associated beta decay (super 14) C dates for Austrovenus stutchburyi shell are presented for 4 middens at Pauatahanui, Wellington, New Zealand. Mean calibrated age ranges of Rattus exulans (520-435 BP and 350-330 BP at 95% confidence level) and shell (465-375 BP at 95% confidence level) from the 4 midden sites overlap. The agreement between Rattus exulans bone gelatin dates and associated shell provides an inter-sample comparison of (super 14) C dating using both gas counting (beta decay) and AMS dating techniques. We examine the adequacy of the standard gelatinization treatment for bone samples, which has been employed consistently at the laboratory since 1995.
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factors influencing 14c ages of the pacific rat Rattus exulans
Radiocarbon, 1997Co-Authors: Nancy Beavan, Rodger J SparksAbstract:An isotopic database for the Pacific/Polynesian rat (Rattus exulans) and foods that it scavenges is used to examine diet-induced (super 14) C age variation in omnivores. We discuss a suite of 26 Delta (super 14) C determinations and (super 13) C and (super 15) N analysis for modern Pacific/Polynesian rat bone gelatin and available food items from Kapiti Island, New Zealand (40 degrees 51'S, 174 degrees 75'E). These analyses provide the first isotopic data for modern specimens of the species, collected as part of a larger project to determine potential sources of bias in unexpectedly old (super 14) C age measurements on subfossil specimens of R. exulans from New Zealand. Stable C, N and (super 14) C isotopic and trapping data are used to trace carbon intake via the diet of the rats in each habitat. Data from specimens linked to five specific habitats on the island indicate that modern populations of R. exulans are not in equilibrium with atmospheric values of Delta (super 14) C, being either enriched or depleted relative to the atmospheric curve in 1996/97, the period of collection. The Delta (super 14) C values recorded for R. exulans are associated with diet, and result from variation in Delta (super 14) C values found in animal-protein food items available to a scavenging omnivore. The titer of carbon deviating from atmospheric values is believed to be derived from the essential amino acids in the protein-rich foods of the rat diet. Present evidence suggests that the depletion required to affect (super 14) C ages limits the possibility that diet introduces dramatic offsets from true ages. Marine diets, for example, would have a variable effect on ages for terrestrial omnivores, contraindicating the application of a standard marine correction for such specimens. We suggest that to identify the extent to which diet may influence the (super 14) C age in a given specimen of terrestrial omnivore, the separation and dating of essential amino acids vs. a nonessential amino, such as glycine, be applied.
