RESUMEN
Drug resistance has been worsening in human infectious diseases medicine over the past several decades. Our ability to successfully control resistance depends to a large extent on our understanding of the features characterizing the process. Part of that understanding includes the rate at which new resistance has been emerging in pathogens. Along that line, resistance data covering 90 infectious diseases, 118 pathogens, and 337 molecules, from 1921 through 2007, are modeled using various statistical tools to generate regression models for the rate of new resistance emergence and for cumulative resistance build-up in pathogens. Thereafter, the strength of the association between the number of molecules put on the market and the number of resulting cases of resistance is statistically tested. Predictive models are presented for the rate at which new resistance has been emerging in infectious diseases medicine, along with predictive models for the rate of cumulative resistance build-up in the aggregate of 118 pathogens as well as in ten individual pathogens. The models are expressed as a function of time and/or as a function of the number of molecules put on the market by the pharmaceutical industry. It is found that molecules significantly induce resistance in pathogens and that new or cumulative drug resistance across infectious diseases medicine has been arising at exponential rates.
Asunto(s)
Antibacterianos/farmacología , Infecciones Bacterianas/microbiología , Enfermedades Transmisibles Emergentes/microbiología , Farmacorresistencia Bacteriana , Modelos Estadísticos , Bacterias/efectos de los fármacos , Humanos , Pruebas de Sensibilidad MicrobianaRESUMEN
The long generation time and large effective size of widespread forest tree species can result in slow evolutionary rate and incomplete lineage sorting, complicating species delimitation. We addressed this issue with the African timber tree genus Milicia that comprises two morphologically similar and often confounded species: M. excelsa, widespread from West to East Africa, and M. regia, endemic to West Africa. We combined information from nuclear microsatellites (nSSRs), nuclear and plastid DNA sequences, and morphological systematics to identify significant evolutionary units and infer their evolutionary and biogeographical history. We detected five geographically coherent genetic clusters using nSSRs and three levels of genetic differentiation. First, one West African cluster matched perfectly with the morphospecies M. regia that formed a monophyletic clade at both DNA sequences. Second, a West African M. excelsa cluster formed a monophyletic group at plastid DNA and was more related to M. regia than to Central African M. excelsa, but shared many haplotypes with the latter at nuclear DNA. Third, three Central African clusters appeared little differentiated and shared most of their haplotypes. Although gene tree paraphyly could suggest a single species in Milicia following the phylogenetic species concept, the existence of mutual haplotypic exclusivity and nonadmixed genetic clusters in the contact area of the two taxa indicate strong reproductive isolation and, thus, two species following the biological species concept. Molecular dating of the first divergence events showed that speciation in Milicia is ancient (Tertiary), indicating that long-living tree taxa exhibiting genetic speciation may remain similar morphologically.
Asunto(s)
Evolución Biológica , Especiación Genética , Moraceae/anatomía & histología , Moraceae/genética , Filogenia , África , Secuencia de Bases , Teorema de Bayes , Cartilla de ADN/genética , Evolución Molecular , Haplotipos/genética , Repeticiones de Microsatélite/genética , Modelos Genéticos , Datos de Secuencia Molecular , Familia de Multigenes/genética , Filogeografía , Análisis de Secuencia de ADNRESUMEN
The following study aims at assessing the ophidian diversity of the Lama Forest, a classified area, situated in the South of Benin. One can distinguish three types of habitat according to the degree of human activity: the remaining dense forest at the centre, the intermediate plantation area, and finally the area around the edge which has been entirely subjected to human habitation. Each day for two weeks we have been working on various plots of study (by day), patrolled along transect routes (by night), and installed a trap in the central area. As a result, we were able to observe 32 snake specimens, 24 of which we captured. Nearly all were able to be identified, and have been classified into 13 genera and 17 species.
Asunto(s)
Biodiversidad , Serpientes , Animales , Benin , Ecosistema , Geografía , Humanos , Proyectos Piloto , Densidad de Población , Serpientes/fisiología , ÁrbolesRESUMEN
Forests of the Dahomey Gap are considered as refugia for many species. They play a crucial role in providing ecosystem services in an area devoid of forests. However, the impact of the way they are managed on the biodiversity they host has barely been investigated. Wild yams existing in these forests play a crucial role in maintaining the genetic diversity of cultivated yams. Indeed, studies of farmer practices have shown that, by way of ennoblement, wild yams collected and selected in the forests and old fallow areas are integrated into the cultivated pool. However, the genetic structure of wild yams is poorly understood. Using nine microsatellite loci, we investigated the population genetics of Dioscorea praehensilis in five forests in Benin, involving different management strategies and bioclimatic areas. Populations of D. praehensilis were strongly differentiated, consistent with an ancient separation of the forests. While the D. praehensilis population in a holly forest was undergoing mutation and drift equilibrium, the population collected from the most conserved forest was in a bottleneck. Moreover, in two forests with different management strategies, accessions from other forests were found, resulting from the displacement of yams following farmer migrations. No isolation by distance was detected, but a differentiation was found between populations of the Sudano-Guinean climate and the Guineo-Congolian climate. Our findings suggest differentiation due to forest isolations under past climatic conditions and more recent tuber flow through anthropogenic impacts.
Asunto(s)
Clima , Dioscorea/genética , Ecosistema , Genética de Población , Agricultura/métodos , Benin , Conservación de los Recursos Naturales , ADN de Plantas/genética , Frecuencia de los Genes , Flujo Genético , Genotipo , Repeticiones de Microsatélite , Mutación , Análisis de Secuencia de ADNRESUMEN
BACKGROUND AND AIMS: Baobab (Adansonia digitata) is a multi-purpose tree used daily by rural African communities. The present study aimed at investigating the level of morphometric and genetic variation and spatial genetic structure within and between threatened baobab populations from the three climatic zones of Benin. METHODS: A total of 137 individuals from six populations were analysed using morphometric data as well as molecular marker data generated using the AFLP technique. KEY RESULTS: Five primer pairs resulted in a total of 217 scored bands with 78.34 % of them being polymorphic. A two-level AMOVA of 137 individuals from six baobab populations revealed 82.37 % of the total variation within populations and 17.63 % among populations (P < 0.001). Analysis of population structure with allele-frequency based F-statistics revealed a global F(ST) of 0.127 +/- 0.072 (P < 0.001). The mean gene diversity within populations (H(S)) and the average gene diversity between populations (D(ST)) were estimated at 0.309 +/- 0.000 and 0.045 +/- 0.072, respectively. Baobabs in the Sudanian and Sudan-Guinean zones of Benin were short and produced the highest yields of pulp, seeds and kernels, in contrast to the ones in the Guinean zone, which were tall and produced only a small number of fruits with a low pulp, seed and kernel productivity. A statistically significant correlation with the observed patterns of genetic diversity was observed for three morphological characteristics: height of the trees, number of branches and thickness of the capsules. CONCLUSIONS: The results indicate some degree of physical isolation of the populations collected in the different climatic zones and suggest a substantial amount of genetic structuring between the analysed populations of baobab. Sampling options of the natural populations are suggested for in or ex situ conservation.
Asunto(s)
Adansonia/genética , Clima , Variación Genética , Adansonia/anatomía & histología , Benin , Análisis por Conglomerados , Dermatoglifia del ADN , Polimorfismo de Longitud del Fragmento de RestricciónRESUMEN
This study provides data on the past and present distribution of the red-bellied monkey, Cercopithecus erythrogaster erythrogaster, a subspecies that is endemic to Benin's southern ecosystems. The original distribution of this subspecies was between the Couffo River and the Nigerian border, but it has since been reduced to regions degraded by intense human settlement (such as the Oueme river valley) and to some better preserved areas, such as the Lama protected forest and some sacred grove forests in wet areas. Local people participated in this research programme and, as a result, many new localities have been discovered. All of these have been in wetlands in southern Benin, mainly in sacred groves. Conservation action for this subspecies will succeed only if local people are involved in its protection.