Identifying Source Populations Research Articles

Determining source populations of newly identified cases of chronic wasting disease in white‐tailed deer

Chronic wasting disease (CWD) is a transmissible spongiform encephalopathy caused by prions, and affects deer, elk and moose. CWD was first reported in Illinois in 2002 and continues to spread. Spark deer, or new CWD cases found in disease free locations > 60 miles from infection zones, are worrisome because of their risk of infecting healthy populations. In Illinois, six spark cases have been reported south of the north core area. It is unknown whether spark deer originated from the core and migrated to southern areas or southern individuals contracted CWD from within their locale. The objective of this study was to genetically identify source populations of spark cases. Using microsatellites, randomly selected samples from north and south source populations were genotyped, tested for Hardy‐Weinberg and linkage disequilibrium using CERVUS, and allele frequencies calculated using ARLEQUIN. Assignment tests compared genotypes of each spark case to the north and south to calculate the probability of genotype occurrence in each population. Based on the probability, we assessed likelihoods that these spark deer originated from the disease core or local population. The results of the study provided a better understanding of potential mechanisms of spark case occurrence, the data required to evaluate sparks in Illinois and potential sources of CWD spread. This project was supported by the IDNR and UIUC‐OVCR.

Geographic profiling as a novel spatial tool for targeting the control of invasive species

Geographic profiling (GP) was originally developed as a statistical tool in criminology, where it uses the spatial locations of linked crimes (for example murder, rape or arson) to identify areas that are most likely to include the offender's residence. The technique has been successful in this field, and is now widely used by police forces and investigative agencies around the world. Here, we show that this novel technique can also be used to identify source populations of invasive species, using their current locations as input, as a prelude to targeted control measures. Our study has two main parts. In the first, we use computer simulations to compare GP to other simple measures of spatial central tendency (centre of minimum distance, spatial mean, spatial median), as well as to a more sophisticated single parameter kernel density model. GP performs significantly better than any of these other approaches. In the second part of the study, we analyse historical data from the Biological Records Centre (BRC) for 53 invasive species in Great Britain, ranging from marine invertebrates to woody trees, and from a wide variety of habitats (including littoral habitats, woodland and man‐made habitats). For 52 of these 53 data sets, GP outperforms spatial mean, spatial median and centre of minimum distance as a search strategy, particularly as the number of sources (or potential sources) increases. We analyse one of these data sets, for Heracleum mantegazzianum, in more detail, and show that GP also outperforms the kernel density model. Finally, we compare fitted parameter values between different species, groups and habitat types, with a view to identifying general values that might be used for novel invasions where data are lacking. We suggest that geographic profiling could potentially form a useful component of integrated control strategies relating to a wide variety of invasive species.

Isolation and characterization of 9 polymorphic microsatellite markers for the endangered boring giant clam (Tridacna crocea) and cross-priming testing in three other Tridacnid species

We report the development and characterization of nine microsatellite markers from the Tridacna crocea genome. In a wild population of 20 individuals from Ulugan Bay in the Republic of the Philippines, we observed an average of 9 alleles per locus and expected heterozygosity ranging from 0.41 to 0.92. Cross-species priming was tested in three additional Tridacna species with moderate success. These markers will be used in studies of fine-scale population genetic structure and gene flow in T. crocea. The markers may also be useful in a forensic context by identifying source populations of giant clams collected illegally for the live aquarium trade, while protecting legal exports from aquaculture facilities.

Patterns of Genetic Variation Among Populations of the Asian Longhorned Beetle (Coleoptera: Cerambycidae) in China and Korea

Abstract Central to the study of invasive species is identifying source populations in their native ranges. Source populations of invasive species can provide important information about species life cycles, host use, and species-specific predators and parasites that could be deployed in a biological control program. The Asian longhorned beetle, Anoplophora glabripennis (Motschulsky) (Coleoptera: Cerambycidae), is a serious invasive pest of urban forests in North America and Europe. We analyzed mitochondrial DNA haplotype frequencies and microsatellite allele frequencies to characterize phylogeographical patterns in potential source populations of A.. glabripennis. The data suggest that although there is evidence of genetic structure within and among populations in China, a substantial amount of genetic admixture has occurred. This admixture is probably due to recent reforestation efforts in China where beetles from previously isolated populations moved into new areas of abundant, susceptible, and stressed resources, leading to outbreak populations.

Revealing the geographic origin of an invasive lizard: the problem of native population genetic diversity

The brown anole, Anolis sagrei, is one of the most widespread and successful colonisers of the diverse Anolis genus, which comprises c. 400 species occurring naturally in Central and South America and the Caribbean. Based on extensive between and within population sampling from a previously published study (334 mitochondrial DNA sequences) and sampling for this study (37 mtDNA sequences), we reconstruct a phylogeny and produce a haplotype network to assign a recently introduced population in St Vincent, Lesser Antilles to its geographic origin. A single haplotype was present in the St Vincent population, which was identical to a haplotype from Tampa, FL. We show that genetic diversity within native range populations, combined with low frequencies of introduced haplotypes in native ranges, may impair attempts to identify source populations, even despite intensive sampling effort. The absence of mtDNA haplotype diversity suggests a significant genetic founder effect within the St Vincent population.

Genetic identification of source populations for an aquarium‐traded invertebrate

AbstractIncreasingly, wildlife managers are turning to molecular genetics to aid in conservation efforts. While such approaches have been applied to large terrestrial and aquatic vertebrate species, their application to other traded organisms has not been extensively explored. Here, we examined the utility of these techniques for identifying source populations of aquarium ornamental invertebrates, using members of the Hawaiian atyid genus Halocaridina as a study system. These shrimps, restricted to anchialine habitats of the Hawaiian Islands, are popular in the aquarium trade due to their ability to survive in hermetically sealed containers for extended periods of time. However, commercial harvesting, coupled with habitat destruction and strong regional endemism, could lead to the depletion/extinction of unique populations. Because the land district of Kona, along the west coast of the island of Hawai'i, has the state's highest concentration of anchialine habitats, we hypothesized that commercially available Halocaridina originated from this region. To test this, mitochondrial cytochrome c oxidase subunit I gene sequences from 96 individuals, obtained from six vendors, were compared with 580 homologous sequences from previous studies covering the known distribution range of Halocaridina. Recovery of identical, regional‐specific haplotypes, network analyses and statistical assignment tests identified these commercially acquired specimens as belonging to either the Kona, Ka'ū, (western and southern coasts, respectively, island of Hawai'i) or Kina'u (southern coast, island of Maui) genetic groups of these shrimps. Although 39 of the 96 individuals originated from the Kona genetic group as hypothesized, our finding that commercially available Halocaridina are from three genetic groups spanning two islands suggests that other populations also warrant potential management consideration. While this study represents the first application of molecular genetics in identifying source populations of aquarium ornamental species, we feel that these techniques are amenable more broadly as they are dependent on only a few caveats.

Ecological Genetics of Plant Invasion: What Do We Know?

AbstractThe rate at which plant invasions occur is accelerating globally, and a growing amount of recent research uses genetic analysis of invasive plant populations to better understand the histories, processes, and effects of plant invasions. The goal of this review is to provide natural resource managers with an introduction to this research. We discuss examples selected from published studies that examine intraspecific genetic diversity and the role of hybridization in plant invasion. We also consider the conflicting evidence that has emerged from recent research for the evolution of increased competitiveness as an explanation for invasion, and the significance of multiple genetic characteristics and patterns of genetic diversity reported in the literature across different species invasions. High and low levels of genetic diversity have been found in different invading plant populations, suggesting that either selection leading to local adaptation, or pre-adapted characteristics such as phenotypic plasticity, can lead to aggressive range expansion by colonizing nonnative species. As molecular techniques for detecting hybrids advance, it is also becoming clear that hybridization is a significant component of some plant invasions, with consequences that include increased genetic diversity within an invasive species, generation of successful novel genotypes, and genetic swamping of native plant gene pools. Genetic analysis of invasive plant populations has many applications, including predicting population response to biological or chemical control measures based on diversity levels, identifying source populations, tracking introduction routes, and elucidating mechanisms of local spread and adaptation. This information can be invaluable in developing more effectively targeted strategies for managing existing plant invasions and preventing new ones. Future genetic research, including the use of high throughput molecular marker systems and genomic approaches such as microarray analysis, has the potential to contribute to better understanding and more effective management of plant invasions.

Invasion success and genetic diversity of introduced populations of guppiesPoecilia reticulatain Australia

High genetic diversity is thought to characterize successful invasive species, as the potential to adapt to new environments is enhanced and inbreeding is reduced. In the last century, guppies, Poecilia reticulata, repeatedly invaded streams in Australia and elsewhere. Quantitative genetic studies of one Australian guppy population have demonstrated high additive genetic variation for autosomal and Y-linked morphological traits. The combination of colonization success, high heritability of morphological traits, and the possibility of multiple introductions to Australia raised the prediction that neutral genetic diversity is high in introduced populations of guppies. In this study we examine genetic diversity at nine microsatellite and one mitochondrial locus for seven Australian populations. We used mtDNA haplotypes from the natural range of guppies and from domesticated varieties to identify source populations. There were a minimum of two introductions, but there was no haplotype diversity within Australian populations, suggesting a founder effect. This was supported by microsatellite markers, as allelic diversity and heterozygosity were severely reduced compared to one wild source population, and evidence of recent bottlenecks was found. Between Australian populations little differentiation of microsatellite allele frequencies was detected, suggesting that population admixture has occurred historically, perhaps due to male-biased gene flow followed by bottlenecks. Thus success of invasion of Australia and high additive genetic variance in Australian guppies are not associated with high levels of diversity at molecular loci. This finding is consistent with the release of additive genetic variation by dominance and epistasis following inbreeding, and with disruptive and negative frequency-dependent selection on fitness traits.

THE APPLICABILITY OF X-RAY ENERGY-DISPERSIVE SPECTROSCOPY TO THE IDENTIFICATION OF POPULATIONS OF RED TURNIP BEETLE, ENTOMOSCELIS AMERICANA (COLEOPTERA: CHRYSOMELIDAE)

AbstractThe relative concentration of elements in adults of the red turnip beetle, Entomoscelis americana Brown, as determined by X-ray energy-dispersive spectroscopy (XES), was used with discriminant analysis to identify source populations of beetles from different fields in the same district. Classification of dispersed beetles from the same district, using discriminant functions, suggests that XES is a promising technique for dispersal studies. However, multivariate analysis of variance and canonical analysis of XES results of groups of beetles given different foods over varying times in the laboratory indicate that highly significant changes occur in the chemoprint. Methods of minimizing the effect of such changes are suggested for future studies of dispersal.