Molecular epidemiology of cassava mosaic disease in Madagascar

Cassava is the staple food for hundreds of millions of people in Africa but its cultivation is seriously constrained by cassava mosaic disease (CMD) in Madagascar, and in Africa in general. This study identified the cassava mosaic geminiviruses (CMGs) involved in CMD in Madagascar and their associated epidemiological characteristics from countrywide surveys. Molecular characterization of CMGs in Madagascar revealed an unprecedented diversity and co‐occurrence of six viruses: African cassava mosaic virus (ACMV), East African cassava mosaic Cameroon virus (EACMCV), East African cassava mosaic Kenya virus (EACMKV), East African cassava mosaic virus (EACMV), South African cassava mosaic virus (SACMV) and the recently described Cassava mosaic Madagascar virus (CMMGV). Distinct geographical distributions were observed for the six viruses. While ACMV was more prevalent in the central highlands, EACMV and EACMKV were prevalent in lowlands and coastal regions. Both EACMCV and SACMV occurred in almost all the localities visited. PCR diagnosis revealed that mixed infection (up to four co‐infected viruses) occurred in 21% of the samples and were associated with higher symptom severity scores. Pairwise comparisons of virus associations showed that EACMCV was found in mixed infections more often than expected while ACMV and SACMV were mostly found in single infections. A greater abundance of whiteflies was observed in lowland and coastal areas. Nevertheless, infected cuttings remain the primary source of CMD propagation (95%) in Madagascar.     

海南长春花小叶病植原体16S rDNA基因片段的比较分析

从海南儋州地区的长春花上采集了表现小叶症状,疑似植原体感染的病样,利用植原体165 rDNA通用引物对R16mF2/R16mR1,应用PCR技术从该样品的总DNA提取物中扩增到预期大小的特异片段(约1.4kb),该片段的序列分析及系统关系树构建的结果表明,该片段与16Sr Ⅰ组中的植原体同源率均达到99%以上,而与其它组的植原体16S rDNA序列的同源率均低于96%,与16Sr Ⅰ组植原体缬草黄化、翠菊黄化、桑萎缩和玉米丛矮等在同一条进化枝上.故初步认为引起海南长春花小叶病的植原体应归属于16Sr Ⅰ组,将其暂命名为长春花小叶植原体海南株系(Periwinkle little leaf phytoplasma strain Hainan,PLL-Hn).     

PRACT (Prototyping Rotation and Association with Cover crop and no Till) – a tool for designing conservation agriculture systems

Moving to more agroecological cropping systems implies deep changes in the organization of cropping systems. We propose a method for formalizing the process of innovating cropping system prototype design using a tool called PRACT (Prototyping Rotation and Association with Cover crop and no Till) applied to a Malagasy case study. The input information for PRACT is comprised of: (i) crop and cover crop adaptation to biophysical conditions, (ii) agroecological functions of the cover crops, (iii) crop production, (iv) association possibilities between crop and cover crop, and (v) agroecological functions of the cropping system. All the information was derived from expert knowledge developed over more than 12 years of agronomic experiments in Madagascar. The final output from PRACT is a list of cropping systems, i.e., crop and cover crop associations and their sequences over three years. These cropping systems are characterized by their potential agroecological functions and crop production. The PRACT model selects a list of cropping systems taking into account the above information by using elaborate rules governing the intercropping and sequences between crops and cover crops. Examples of the outcomes of model simulations are provided for four different kinds of field. Taking into account the range of potential crops and cover crops, the number of cropping systems that was theoretically possible for the different field types ranged from 19,683 to 2.98 ×  10¹³. In a first step, PRACT reduced this number by a factor of up to 28 times to propose possible cropping systems. To do so, cropping systems are selected in terms of the biophysical requirements of plants, plant compatibility and agronomic rules. Not all of these systems are suitable for every farmer. Thus using PRACT output, a second cropping system selection step can be taken based on these cropping system characteristics, i.e., crop production and agroecological functions. By doing so the number of cropping systems selected can reach a reasonable value that can be handled by technicians and farmers. Possible uses and further development of the tool are discussed.     

Patterns of species change in anthropogenically disturbed forests of Madagascar

Five main conclusions arise from this review of the responses of species to anthropogenic disturbance in Madagascar: First, species’ reactions to anthropogenic disturbance are generally negative, but remain poorly known. Our knowledge is patchy among and within higher taxonomic groups; we are still largely gathering case studies. Second, taxonomic groups vary considerably in which proximate factors are most important. Third, several groups show differing responses within different ecoregions. Whether these differences are consistent across groups requires further testing. Fourth, related species often have divergent reactions to disturbance, even within lower taxonomic groupings (families or genera). Thus, we cannot rely on phylogenetic relatedness or even ecological similarity to infer similarity in responses. Finally, disturbance typically reduces species diversity (especially of native and/or endemic species), but also causes species turnover, typically with forest specialists replaced by grassland generalists, and endemics replaced by non-endemics (including invasives). Given these knowledge gaps, we stress the urgency of applied studies that assess species’ ecology, behaviour and health across disturbance gradients, including purely anthropogenic landscapes. Remaining natural vegetation and protected areas will be unable to preserve Madagascar’s biodiversity under the impact of climatic change; we must understand responses of plants and animals to disturbance in order to create buffer zones and corridors combining secondary, degraded and natural habitats.     

The impacts of international and national governance changes on a traded resource: a case study of Madagascar and its chameleon trade

Trade in wildlife resources is permitted and regulated by national and international governance. Focussing on the trade in chameleons from Madagascar, our objective was to investigate the consequences of changes in governance on the number of individuals and species traded together with the prices paid to collectors, intermediaries and exporters. As a result of the liberalisation of export controls in 1988, exports of chameleons grew exponentially at an average rate of 62% per annum, the trade in Calumma spp. increasing at 91% per annum. The intervention of CITES in 1994, as a result of concerns over the trade, capped official exports at approximately 20,000 per annum and also restricted the trade to four species of Furcifer. The consequence of the CITES intervention was a shift in the species exported from a mix of Calumma harvested in the east and Furcifer harvested in the west to a trade in Furcifer alone, alongside an increase in the number of Furcifer exports. Consequently there was a shift in the distribution of local benefits gained from the trade away from the rainforests in the east, the centre of conservation concern. At the same time there was also a fall in the prices paid to collectors and intermediaries involved in the trade and a widening of the gap with the prices paid to exporters. The creation of an Experimental Management Programme within Madagascar to address the concerns of CITES in 1998/1999 and lobby for some expansion of the trade, led to an initial fall in the number of chameleons traded. Failure to achieve the latter objective has more recently led to an increase in the number of species traded and a further widening of the prices paid to collectors and exporters. These results highlight the need to consider carefully the consequences of changes in governance on the wildlife trade if conservation and local people are to benefit from the trade in wildlife resources.     

Wild-captive metapopulation viability analysis

We developed an interactive management model for wild and captive populations of the ploughshare tortoise or angonoka, Geochelone yniphora. Interactive management is based on the translocation of individuals between wild and captive populations to simulate a metapopulation. Demographic parameters of one captive and two wild populations of this rare tortoise were used to conduct a metapopulation viability analysis (MVA). The effectiveness of the conservation strategy proposed for this species was then evaluated by modifying the probability of extinction and growth of the metapopulation over a fixed period of time. Several alternative scenarios of interactive management were then tested and ranked in terms of their effect on the viability of the metapopulation. The model predicted that catastrophic events such as bush fires would likely have a negative effect on the future of remaining wild populations. However, the model also predicted that the use of captive-born offspring to establish additional wild populations would decrease the risk of extinction of the metapopulation as a whole. We believe that, when supported by sound knowledge of the demographic parameters of a species, the use of MVA as part of an interactive management program can be an effective conservation tool that allows assessment of the probable response of both captive and wild populations to different management alternatives. One of the most interesting aspects of this interactive management approach is the link between in situ and ex situ conservation.     

Field assessment of dog as sentinel animal for plague in endemic foci of Madagascar

The epidemiology of Yersinia pestis, the causative agent of plague, involves vectors and reservoirs in its transmission cycle. The passive plague surveillance in Madagascar targets mainly rodent and fleas. However, carnivores are routinely surveyed as sentinels of local plague activity in some countries. The aim of this study is to assess the use of domestic dog (Canis familiaris) as sentinel animal for field surveillance of plague in a highly endemic area in Madagascar. Cross-sectional surveys of plague antibody prevalence in C. familiaris were conducted in endemic areas with contrasting histories of plague cases in humans, as well as a plague free area. Rodent capture was done in parallel to evaluate evidence for Y. pestis circulation in the primary reservoirs. In 2 sites, dogs were later re-sampled to examine evidence of seroconversion and antibody persistence. Biological samplings were performed between March 2008 and February 2009. Plague antibody detection was assessed using anti-F1 ELISA. Our study showed a significant difference in dog prevalence rates between plague-endemic and plague-free areas, with no seropositive dogs detected in the plague free area. No correlation was found between rodents and dog prevalence rates, with an absence of seropositive rodents in some area where plague circulation was indicated by seropositive dogs. This is consistent with high mortality rates in rodents following infection. Re-sampling dogs identified individuals seropositive on both occasions, indicating high rates of re-exposure and/or persistence of plague antibodies for at least 9 months. Seroconversion or seropositive juvenile dogs indicated recent local plague circulation. In Madagascar, dog surveillance for plague antibody could be useful to identify plague circulation in new areas or quiescent areas within endemic zones. Within active endemic areas, monitoring of dog populations for seroconversion (negative to positive) or seropositive juvenile dogs could be useful for identifying areas at greatest risk of human outbreaks.     

Chromosomal rearrangements occurred repeatedly and independently during species diversification in Malagasy geckos,genus Paroedura

We conducted a phylogenetic study through karyological data, by standard staining and Ag-NOR banding, and molecular analysis (by 12S and 16S mitochondrial rRNA genes and nuclear gene C-mos) on 11 species of Malagasy geckos, genus Paroedura, and two relatives (Ebenavia inunguis and Uroplatus phantasticus). Ebenavia inunguis and U. phantasticus had 2n = 36 telocentric elements, NORs on the first chromosome pair in E. inunguis, and on the third chromosome pair in U. phantasticus. All examined Paroedura showed NORs on the smallest chromosome pair; moreover, six of the eleven examined species show a 2n = 36 karyotype, with a pair of metacentrics and 17 telocentric pair. The remaining species exhibited karyotypes with a diploid chromosome number ranging from 2n = 31 to 2n = 38. We assume that these karyotype assemblages derived from the 2n=36 karyotype by cryptic and/or simple rearrangements, such as inversions, fissions and fusions. Furthermore, molecular and/or chromosomal data indicate that Paroedura is a monophyletic genus, in which chromosome rearrangements occurred repeatedly and independently during the specific diversification. Moreover both P. bastardi and P. gracilis in current definitions are paraphyletic assemblages of several related species, since their population proves more closely related to P. ibityensis or P. oviceps than co-specific populations.     

From genetic diversity and structure to conservation: Genetic signature of recent population declines in three mouse lemur species (Microcebus spp.)

The exceptional biodiversity of Madagascar is threatened by anthropogenic landscape changes that took place during the 2000 years of human colonization. This study focuses on the influence of geographic distance and forest fragmentation on genetic diversity and population differentiation of three rare, nocturnal, arboreal lemur species in northwestern Madagascar. Historic declines in population sizes as a consequence of forest fragmentation are quantified and dated. Eighteen sites were visited, and a total of 205 Microcebus ravelobensis, 45 M. bongolavensis and 78 M. danfossi were genotyped with eight microsatellite loci. Genetic differentiation among the sites, as measured by F_ST, ranged from 0.01 to 0.19. These values were significant in almost all cases and indicated genetic structure in the samples. Isolation-by-distance was detected in one species and a STRUCTURE analysis indicated that fragmentation further promoted genetic differentiation. Bayesian methods revealed that populations from all three species underwent a major demographic collapse of around two orders of magnitude. This decrease probably began after the arrival of humans, most likely within the last 500 years. This result suggests that anthropogenic changes may have been limited during the first 1500 years of human colonization in all three ranges. Two of the study species (M. danfossi, M. bongolavensis) lack effectively protected areas in their ranges. Consequently, quick conservation actions are now needed in order to secure the remaining genetic diversity of these species.     

药用长春花生长动态研究

[目的]为长春花的规范化生产提供理论依据。[方法]采用随机区组设计,测定长春花的农艺性状和总生物碱含量的动态变化。[结果]长春花农艺性状的动态变化呈现类抛物线型增长。其中株高和一级侧枝数目在4月中下旬就进入快速增长期,株高增速可达11.9cm/10 d,一级侧枝数目增速可达6.4条/10 d;而地径、叶片数目和干、鲜重则于5月下旬或6月上旬进入快速增长期,地径、叶片数目和干、鲜重最快增速分别为1.17cm/10 d、24片/10 d和2.27、15.30 g/10 d。总生物碱含量于6月中旬进入快速增长期,增速可达1.70mg/10 d。[结论]长春花农艺性状都呈现类抛物线型变化,表现为"前期增加缓慢-中期迅速增加-后期缓慢增加"的趋势,总生物碱含量则呈现前期缓慢增长,到6月中下旬进入快速增长期的趋势。