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Canterbury, New Zealand

Russell A.L.,Grand Valley State University | Cox M.P.,Massey University | Cox M.P.,Allan Wilson Center for Molecular Ecology and Evolution | Cox M.P.,Bio Protection Research Center | And 2 more authors.
BMC Evolutionary Biology

Background: Human activities, such as agriculture, hunting, and habitat modification, exert a significant effect on native species. Although many species have suffered population declines, increased population fragmentation, or even extinction in connection with these human impacts, others seem to have benefitted from human modification of their habitat. Here we examine whether population growth in an insectivorous bat (Tadarida brasiliensis mexicana) can be attributed to the widespread expansion of agriculture in North America following European settlement. Colonies of T. b. mexicana are extremely large (∼10 6 individuals) and, in the modern era, major agricultural insect pests form an important component of their food resource. It is thus hypothesized that the growth of these insectivorous bat populations was coupled to the expansion of agricultural land use in North America over the last few centuries. Results: We sequenced one haploid and one autosomal locus to determine the rate and time of onset of population growth in T. b. mexicana. Using an approximate Maximum Likelihood method, we have determined that T. b. mexicana populations began to grow ∼220 kya from a relatively small ancestral effective population size before reaching the large effective population size observed today. Conclusions: Our analyses reject the hypothesis that T. b. mexicana populations grew in connection with the expansion of human agriculture in North America, and instead suggest that this growth commenced long before the arrival of humans. As T. brasiliensis is a subtropical species, we hypothesize that the observed signals of population growth may instead reflect range expansions of ancestral bat populations from southern glacial refugia during the tail end of the Pleistocene. © 2011 Russell et al; licensee BioMed Central Ltd. Source

Lefort M.-C.,Bio Protection Research Center | Lefort M.-C.,Unitec Institute of Technology | Boyer S.,Unitec Institute of Technology | Vereijssen J.,The New Zealand Institute for Plant and Food Research Ltd | And 3 more authors.

Widespread replacement of native ecosystems by productive land sometimes results in the outbreak of a native species. In New Zealand, the introduction of exotic pastoral plants has resulted in diet alteration of the native coleopteran species, Costelytra zealandica (White) (Scarabaeidae) such that this insect has reached the status of pest. In contrast, C. brunneum (Broun), a congeneric species, has not developed such a relationship with these 'novel' host plants. This study investigated the feeding preferences and fitness performance of these two closely related scarab beetles to increase fundamental knowledge about the mechanisms responsible for the development of invasive characteristics in native insects. To this end, the feeding preference of third instar larvae of both Costelytra species was investigated using an olfactometer device, and the survival and larval growth of the invasive species C. zealandica were compared on native and exotic host plants. Costelytra zealandica, when sampled from exotic pastures, was unable to fully utilise its ancestral native host and showed higher feeding preference and performance on exotic plants. In contrast, C. zealandica sampled from native grasslands did not perform significantly better on either host and showed similar feeding preferences to C. brunneum, which exhibited no feeding preference. This study suggests the possibility of strong intraspecific variation in the ability of C. zealandica to exploit native or exotic plants, supporting the hypothesis that such ability underpins the existence of distinct host-races in this species. © 2015 Lefort et al. Source

Meffin R.,Bio Protection Research Center | Duncan R.P.,Bio Protection Research Center | Duncan R.P.,University of Canberra | Hulme P.E.,Bio Protection Research Center
Agriculture, Ecosystems and Environment

To assess the biotic and abiotic drivers of feral crop persistence, the occurrence and size of alien Brassica populations across an agricultural landscape in Canterbury, New Zealand, were surveyed over three years. Measures related to propagule input and site conditions were recorded and their role in explaining population occurrence and persistence assessed through GLMs and proportional-hazard models. Many Brassica populations were transient, with about 60% of populations disappearing within two years. New populations were founded at a rate that compensated for those that disappeared, and were more likely to occur along transportation routes and near seed companies, suggesting they established from seed spillage. Larger populations and those growing where habitat conditions were similar to those in which Brassica are cultivated had higher probabilities of survival. Without anthropogenic seed input to found new populations, Brassica spp. are unlikely to persist in this landscape beyond ten years. To avoid overestimating the extent of naturalised populations over time it is important to account for local population extinctions. The abundance of feral crops that occur as casuals in the landscape, along with other aliens that are maintained by external seed inputs, could be controlled by managing propagule sources. In themselves, casual populations are unlikely to facilitate gene flow or act as sources of further population spread. © 2015 Elsevier B.V. Source

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