Dataset Information

Genetic monitoring detects an overlooked cryptic species and reveals the diversity and distribution of three invasive Rattus congeners in South Africa.

ABSTRACT: BACKGROUND: South Africa's long and extensive trade activity has ensured ample opportunities for exotic species introduction. Whereas the rich biodiversity of endemic southern African fauna has been the focus of many studies, invasive vertebrates are generally overlooked despite potential impacts on biodiversity, health and agriculture. Genetic monitoring of commensal rodents in South Africa which uncovered the presence of Rattus tanezumi, a South-East Asian endemic not previously known to occur in Africa, provided the impetus for expanded studies on all invasive Rattus species present. RESULTS: To this end, intensified sampling at 28 South African localities and at one site in Swaziland, identified 149 Rattus specimens. Cytochrome b gene sequencing revealed the presence of two R. tanezumi, seven Rattus rattus and five Rattus norvegicus haplotypes in south Africa. Phylogenetic results were consistent with a single, recent R. tanezumi introduction and indicated that R. norvegicus and R. rattus probably became established following at least two and three independent introductions, respectively. Intra- and inter-specific diversity was highest in informal human settlements, with all three species occurring at a single metropolitan township site. Rattus norvegicus and R. rattus each occurred sympatrically with Rattus tanezumi at one and five sites, respectively. Karyotyping of selected R. rattus and R. tanezumi individuals identified diploid numbers consistent with those reported previously for these cryptic species. Ordination of bioclimatic variables and MaxEnt ecological niche modelling confirmed that the bioclimatic niche occupied by R. tanezumi in south Africa was distinct from that occupied in its naturalised range in south-east Asia suggesting that factors other than climate may influence the distribution of this species. CONCLUSIONS: This study has highlighted the value of genetic typing for detecting cryptic invasive species, providing historical insights into introductions and for directing future sampling. The apparent ease with which a cryptic species can become established signals the need for broader implementation of genetic monitoring programmes. In addition to providing baseline data and potentially identifying high-risk introduction routes, the predictive power of ecological niche modelling is enhanced when species records are genetically verified.

SUBMITTER: Bastos AD

PROVIDER: S-EPMC3055845 | biostudies-literature | 2011

REPOSITORIES: biostudies-literature

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Genetic monitoring detects an overlooked cryptic species and reveals the diversity and distribution of three invasive Rattus congeners in South Africa.

Bastos Armanda D AD Nair Deenadayalan D Taylor Peter J PJ Brettschneider Helene H Kirsten Frikkie F Mostert Elmarie E von Maltitz Emil E Lamb Jennifer M JM van Hooft Pim P Belmain Steven R SR Contrafatto Giancarlo G Downs Sarah S Chimimba Christian T CT

BMC genetics 20110216

<h4>Background</h4>South Africa's long and extensive trade activity has ensured ample opportunities for exotic species introduction. Whereas the rich biodiversity of endemic southern African fauna has been the focus of many studies, invasive vertebrates are generally overlooked despite potential impacts on biodiversity, health and agriculture. Genetic monitoring of commensal rodents in South Africa which uncovered the presence of Rattus tanezumi, a South-East Asian endemic not previously known t ...[more]

PMID: 21324204

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Project description:BackgroundRattus spp. are frequently implicated as key reservoir hosts for leptospirosis, one of the most common, but neglected, bacterial zoonoses in the world. Although leptospirosis is predicted to be a significant public health threat in Africa, studies from the continent are limited.MethodsRattus spp. (n = 171) were sampled (January-May 2016) across the City of Johannesburg, South Africa's largest inland metropole. Rattus spp. genetic diversity was evaluated by full length (1140 bp) cyt b sequencing of 42 samples. For comparison, a further 12 Rattus norvegicus samples collected in Cape Town, South Africa's largest coastal metropole, were also genotyped. Leptospira infections were identified and genotyped using real-time PCR and multi-locus (lfb1, secY and lipL41) DNA sequencing.ResultsFive R. norvegicus haplotypes were identified across Johannesburg, four of which have not previously been detected in South Africa, and one in Cape Town. Across Johannesburg we identified a Leptospira spp. infection prevalence of 44% (75/171) and noted significant differences in the prevalence between administrative regions within the metropole. Multi-locus sequence analyses identified a clonal genotype consistent with L. borgpetersenii serogroup Javanica (serovar Ceylonica).DiscussionThe prevalence of infection identified in this study is amongst the highest detected in Rattus spp. in similar contexts across Africa. Despite the complex invasion history suggested by the heterogeneity in R. norvegicus haplotypes identified in Johannesburg, a single L. borgpetersenii genotype was identified in all infected rodents. The lack of L. interrogans in a rodent community dominated by R. norvegicus is notable, given the widely recognised host-pathogen association between these species and evidence for L. interrogans infection in R. norvegicus in Cape Town. It is likely that environmental conditions (cold, dry winters) in Johannesburg may limit the transmission of L. interrogans. Spatial heterogeneity in prevalence suggest that local factors, such as land use, influence disease risk in the metropole.ConclusionsIn South Africa, as in other African countries, leptospirosis is likely underdiagnosed. The high prevalence of infection in urban rodents in Johannesburg suggest that further work is urgently needed to understand the potential public health risk posed by this neglected zoonotic pathogen.

Dataset Information

Genetic monitoring detects an overlooked cryptic species and reveals the diversity and distribution of three invasive Rattus congeners in South Africa.

Publications

Genetic monitoring detects an overlooked cryptic species and reveals the diversity and distribution of three invasive Rattus congeners in South Africa.

Similar Datasets

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