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Antananarivo, Madagascar

Tollenaere C.,Montpellier SupAgro | Brouat C.,Montpellier SupAgro | Duplantier J.-M.,Montpellier SupAgro | Rahalison L.,Institute Pasteur Of Madagascar Ipm | And 6 more authors.
Journal of Biogeography

Aim To describe the phylogeographic patterns of the black rat, Rattus rattus, from islands in the western Indian Ocean where the species has been introduced (Madagascar and the neighbouring islands of Réunion, Mayotte and Grande Comore), in comparison with the postulated source area (India). Location Western Indian Ocean: India, Arabian Peninsula, East Africa and the islands of Madagascar, Réunion, Grande Comore and Mayotte. Methods Mitochondrial DNA (cytochrome b, tRNA and D-loop, 1762 bp) was sequenced for 71 individuals from 11 countries in the western Indian Ocean. A partial D-loop (419 bp) was also sequenced for eight populations from Madagascar (97 individuals), which were analysed in addition to six previously published populations from southern Madagascar. Results Haplotypes from India and the Arabian Peninsula occupied a basal position in the phylogenetic tree, whereas those from islands were distributed in different monophyletic clusters: Madagascar grouped with Mayotte, while Réunion and Grand Comore were present in two other separate groups. The only exception was one individual from Madagascar (out of 190) carrying a haplotype that clustered with those from Réunion and South Africa. 'Isolation with migration' simulations favoured a model with no recurrent migration between Oman and Madagascar. Mismatch distribution analyses dated the expansion of Malagasy populations on a time-scale compatible with human colonization history. Higher haplotype diversity and older expansion times were found on the east coast of Madagascar compared with the central highlands. Main conclusions Phylogeographic patterns supported the hypothesis of human-mediated colonization of R. rattus from source populations in either the native area (India) or anciently colonized regions (the Arabian Peninsula) to islands of the western Indian Ocean. Despite their proximity, each island has a distinct colonization history. Independent colonization events may have occurred simultaneously in Madagascar and Grande Comore, whereas Mayotte would have been colonized from Madagascar. Réunion was colonized independently, presumably from Europe. Malagasy populations may have originated from a single successful colonization event, followed by rapid expansion, first in coastal zones and then in the central highlands. The congruence of the observed phylogeographic pattern with human colonization events and pathways supports the potential relevance of the black rat in tracing human history. © 2009 Blackwell Publishing Ltd. Source

Tollenaere C.,Montpellier SupAgro | Duplantier J.-M.,Montpellier SupAgro | Rahalison L.,Institute Pasteur Of Madagascar Ipm | Ranjalahy M.,Institute Pasteur Of Madagascar Ipm | Brouat C.,Montpellier SupAgro
Molecular Ecology

The black rat (Rattus rattus) is the main reservoir of plague (Yersinia pestis infection) in Madagascar's rural zones. Black rats are highly resistant to plague within the plague focus (central highland), whereas they are susceptible where the disease is absent (low altitude zone). To better understand plague wildlife circulation and host evolution in response to a highly virulent pathogen, we attempted to determine genetic markers associated with plague resistance in this species. To this purpose, we combined a population genomics approach and an association study, both performed on 249 AFLP markers, in Malagasy R. rattus. Simulated distributions of genetic differentiation were compared to observed data in four independent pairs, each consisting of one population from the plague focus and one from the plague-free zone. We found 22 loci (9% of 249) with higher differentiation in at least two independent population pairs or with combining P-values over the four pairs significant. Among the 22 outlier loci, 16 presented significant association with plague zone (plague focus vs. plague-free zone). Population genetic structure inferred from outlier loci was structured by plague zone, whereas the neutral loci dataset revealed structure by geography (eastern vs. western populations). A phenotype association study revealed that two of the 22 loci were significantly associated with differentiation between dying and surviving rats following experimental plague challenge. The 22 outlier loci identified in this study may undergo plague selective pressure either directly or more probably indirectly due to hitchhiking with selected loci. © 2010 Blackwell Publishing Ltd. Source

Rabarison H.,University of Antananarivo | Rakotondrafara A.,University of Antananarivo | Razafimandimbison S.G.,University of Stockholm | Ratsimbason M.,Center National Of Recherche Pharmaceutique Cnarp | And 4 more authors.
Scripta Botanica Belgica

Background and methods - Cedrelopsis (Rutaceae), commonly known as Katrafay, is an endemic genus of Madagascar and consists of eight species of trees and shrubs growing on different substrates and in primary and/or modified ecosystems. These species of Cedrelopsis are plant parts most used plants for several purposes. Thus, an ecological assessment was undertaken in aim to understand the pressures and threats to populations, define their conservation status, and establish a strategy for sustainable management. Key results - Approximately 65 to 100% of subpopulations of Cedrelopsis are in sites with no appropriate conservation measure. Timber and habitat loss are the major threats. Cedrelopsis procera is critically endangered, while C. gracilis, C. longibracteata, C. ambanjensis, and C. rakotozafyi are in danger of extinction; C. trivalvis, C. grevei, and C. microfoliolata are vulnerable. Discussion and conclusion - Human activities including wood use and burning are the main pressures contributing to the depletion of species. As regards their conservation status, Cedrelopsis species are actually in an intermediate level between the categories "vulnerable" (VU) and "critically endangered" (CR). Managing their populations and habitats requires effective participation of key players.© 2013 National Botanic Garden of Belgium. All rights reserved. Source

Brouat C.,Montpellier SupAgro | Tollenaere C.,Montpellier SupAgro | Tollenaere C.,Montpellier University | Estoup A.,Montpellier SupAgro | And 10 more authors.
Molecular Ecology

Studies focusing on geographical genetic patterns of commensal species and on human history complement each other and provide proxies to trace common colonization events. On Madagascar, the unintentional introduction and spread of the commensal species Rattus rattus by people may have left a living clue of human colonization patterns and history. In this study, we addressed this question by characterizing the genetic structure of natural populations of R. rattus using both microsatellites and mitochondrial sequences, on an extensive sampling across the island. Such data sets were analysed by a combination of methods using population genetics, phylogeography and approximate Bayesian computation. Our results indicated two introduction events to Madagascar from the same ancestral source of R. rattus, one in the extreme north of the island and the other further south. The latter was the source of a large spatial expansion, which may have initially started from an original point located on the southern coast. The inferred timing of introduction events - several centuries ago - is temporally congruent with the Arabian trade network in the Indian Ocean, which was flourishing from the middle of the first millennium. © 2014 John Wiley & Sons Ltd. Source

Tollenaere C.,Montpellier SupAgro | Rahalison L.,Institute Pasteur Of Madagascar Ipm | Ranjalahy M.,Institute Pasteur Of Madagascar Ipm | Duplantier J.-M.,Montpellier SupAgro | And 3 more authors.

In Madagascar, the black rat, Rattus rattus, is the main reservoir of plague (Yersinia pestis infection), a disease still responsible for hundreds of cases each year in this country. This study used experimental plague challenge to assess susceptibility in wild-caught rats to better understand how R. rattus can act as a plague reservoir. An important difference in plague resistance between rat populations from the plague focus (central highlands) and those from the plague-free zone (low altitude area) was confirmed to be a widespread phenomenon. In rats from the plague focus, we observed that sex influenced plague susceptibility, with males slightly more resistant than females. Other individual factors investigated (weight and habitat of sampling) did not affect plague resistance. When infected at high bacterial dose (more than 10 5 bacteria injected), rats from the plague focus died mainly within 3-5 days and produced specific antibodies, whereas after low-dose infection (< 5,000 bacteria), delayed mortality was observed and surviving seronegative rats were not uncommon. These results concerning plague resistance level and the course of infection in the black rat would contribute to a better understanding of plague circulation in Madagascar. © 2010 International Association for Ecology and Health. Source

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