Long-term landscape changes in vegetation structure: fire management in the wetlands of KwaMbonambi,South Africa

In wetlands the effects of fire on vegetation dynamics are somewhat uncertain. A change detection analysis in the herbaceous wetlands of KwaMbonambi, South Africa, which were subject to frequent fires, revealed that in 1937 the study area comprised grassland (69%), herbaceous wetland (25%), indigenous swamp forest (4%) and tree plantations (1%). However, by 1970, tree plantations occupied 78% of the landscape and grasslands and herbaceous wetlands had declined to 9% and 6%, respectively, whereas indigenous swamp forest had increased to 6%. By 2009 tree plantations had been removed from the wetland areas. Despite this opportunity for herbaceous wetlands to recover their historical extent, they decreased to only 2%, mostly changing to indigenous swamp forest or to an herbaceous/fern (Stenochlaena tenuifolia)/woodland mosaic. Fire records showed suppression of fire to be an important contributing factor, particularly in wetlands that had been disturbed by tree plantations, although subsequently removed. A pilot burning experiment revealed that S. tenuifolia did not inhibit fire. It is therefore practicable to increase fire frequency to prevent the mosaic developing into forest. A conceptual model of the influence of fire regime on wetland vegetation type is presented and priorities for further research on wetlands and fire are recommended.     

西藏墨脱格当乡野生虎捕食家畜现状与保护建议

曾经在西藏东南的阔叶林中广泛分布的孟加拉虎,目前仅有一个小种群残留在墨脱县境内。2000年5－6月间,在大型家畜遭受野生虎捕食最严重的墨脱县格当乡展开调查,试图寻找减轻虎害的方法。结果表明：1994－1995年虎的捕食率达到最高,对牛和骡马的捕食率分别是17．9％和9．4％;但1996年后,捕食率分别降低到7．8％和1．8％,这可能与1996年当地曾捕杀过一头虎有关。1993－1999年间,全乡牛的数量下降了11％,但骡马数量上升了23％,这是因为当地为增加运输能力而从别处购得骡马。据反映,目前格当乡境内大约有4－5头虎。1997年和1999年,均见母虎和小虎同行,说明该种群尚有繁殖。在抽样的21户居民家中,1999年4月到2000年5月间,66．6％的人家有大型牲畜遭虎捕杀,共损失牛27头,马12匹,而自1993年以来,21户中共有18户（85．8％）,有牲畜被杀记录,共计损失117头。其中对牛的捕食率达19．7％,对马达11．9％,平均每户损失牛1．2头,骡马0．5匹。非法狩猎减少了虎的猎物如野猪、羚牛等的数量,是老虎转向家畜的主要原因之一。虎害已对格当乡群众的经济造成较大负面影响。但格当乡以及周边地区保护着中国最后的野生孟加拉虎种群,为确保虎的长期生存同时减少人－虎冲突,建议改变目前放牧方式,尽可能联合放牧、增加看护;改善放牧地条件,清除牧场周围蕨草丛;减少对羚牛等有蹄类的猎杀,以减少对老虎猎物种群的破坏;对部分家畜移入棚内试行圈养,既保护家畜,又提高乳制品产量和增加农家肥料;实行多种经营方法,建议养一些山羊和家禽;政府应该帮助安置好部分愿意外迁的居民,这样既满足这些居民的需要,同时也减轻对当地野生动物种群的压力。     

Genetic variation in South Indian castes: evidence from Y-chromosome, mitochondrial, and autosomal polymorphisms

Background

Major population movements, social structure, and caste endogamy have influenced the genetic structure of Indian populations. An understanding of these influences is increasingly important as gene mapping and case-control studies are initiated in South Indian populations.

Results

We report new data on 155 individuals from four Tamil caste populations of South India and perform comparative analyses with caste populations from the neighboring state of Andhra Pradesh. Genetic differentiation among Tamil castes is low (R_ST = 0.96% for 45 autosomal short tandem repeat (STR) markers), reflecting a largely common origin. Nonetheless, caste- and continent-specific patterns are evident. For 32 lineage-defining Y-chromosome SNPs, Tamil castes show higher affinity to Europeans than to eastern Asians, and genetic distance estimates to the Europeans are ordered by caste rank. For 32 lineage-defining mitochondrial SNPs and hypervariable sequence (HVS) 1, Tamil castes have higher affinity to eastern Asians than to Europeans. For 45 autosomal STRs, upper and middle rank castes show higher affinity to Europeans than do lower rank castes from either Tamil Nadu or Andhra Pradesh. Local between-caste variation (Tamil Nadu R_ST = 0.96%, Andhra Pradesh R_ST = 0.77%) exceeds the estimate of variation between these geographically separated groups (R_ST = 0.12%). Low, but statistically significant, correlations between caste rank distance and genetic distance are demonstrated for Tamil castes using Y-chromosome, mtDNA, and autosomal data.

Conclusion

Genetic data from Y-chromosome, mtDNA, and autosomal STRs are in accord with historical accounts of northwest to southeast population movements in India. The influence of ancient and historical population movements and caste social structure can be detected and replicated in South Indian caste populations from two different geographic regions.     

Impact of ivermectin on onchocerciasis transmission: assessing the empirical evidence that repeated ivermectin mass treatments may lead to elimination/eradication in West-Africa

BACKGROUND: The Onchocerciasis Control Program (OCP) in West Africa has been closed down at the end of 2002. All subsequent control will be transferred to the participating countries and will almost entirely be based on periodic mass treatment with ivermectin. This makes the question whether elimination of infection or eradication of onchocerciasis can be achieved using this strategy of critical importance. This study was undertaken to explore this issue. METHODS: An empirical approach was adopted in which a comprehensive analysis was undertaken of available data on the impact of more than a decade of ivermectin treatment on onchocerciasis infection and transmission. Relevant entomological and epidemiological data from 14 river basins in the OCP and one basin in Cameroon were reviewed. Areas were distinguished by frequency of treatment (6-monthly or annually), endemicity level and additional control measures such as vector control. Assessment of results were in terms of epidemiological and entomological parameters, and as a measure of inputs, therapeutic and geographical coverage rates were used. RESULTS: In all of the river basins studied, ivermectin treatment sharply reduced prevalence and intensity of infection. Significant transmission, however, is still ongoing in some basins after 10-12 years of ivermectin treatment. In other basins, transmission may have been interrupted, but this needs to be confirmed by in-depth evaluations. In one mesoendemic basin, where 20 rounds of four-monthly treatment reduced prevalence of infection to levels as low as 2-3%, there was significant recrudescence of infection within a few years after interruption of treatment. CONCLUSIONS: Ivermectin treatment has been very successful in eliminating onchocerciasis as a public health problem. However, the results presented in this paper make it almost certain that repeated ivermectin mass treatment will not lead to the elimination of transmission of onchocerciasis from West Africa. Data on 6-monthly treatments are not sufficient to draw definitive conclusions.     

Sequence variation in ZFX introns in human populations

DNA variation in human populations was studied by examining the last intron of the ZFX gene (about 1, 151 bp) with a worldwide sample of 29 individuals. Only one polymorphic site was found, which is located in an Alu sequence. This polymorphism is present at an intermediate frequency in all populations studied, and could be a shared polymorphism or due to migration among populations in Asia, Europe, and Africa. The nucleotide diversity is 0.04%, supporting the view that the level of nucleotide variation in nuclear DNA is very low in humans. From the sequence data, the age (T) of the most recent common ancestor of the sampled sequences is estimated: the mode of T is about 306,000 years, and the 95% confidence interval of T is 162,000-952,000 years. This mode estimate is considerably older than the estimates from Y- linked sequences.      

Marcusenius desertus sp. nov. (Teleostei: Mormyridae), a mormyrid fish from the Namib desert

We critically compared Marcusenius specimens from the mouth of the Cunene River on the Namibia/Angola border, a harsh desert environment on the Atlantic Ocean coast virtually devoid of aerial insects with aquatic larvae which are an important food item, with Marcusenius multisquamatus Kramer & Wink, 2013 from the escarpment region of that same river, in a relatively rich and productive subtropical savannah environment. River mouth specimens were differentiated in morphology and electric organ discharges, as determined by ANOVA/MANOVA comparisons, principal component and discriminant analyses on morphological and electrophysiological characters, and genetics, including sequences of the mitochondrial cytochrome b gene, indicating reproductive isolation. Specimens from the river mouth differed from M. multisquamatus, their closest relatives, by having a shorter snout, a smaller eye diameter, and smaller nares separation. River mouth specimens were also differentiated from other, increasingly less-close relatives, such as M. altisambesi Kramer et al., 2007 from the Okavango River, Botswana, and from M. krameri Maake et al., 2014 from the Limpopo System, South Africa. We therefore designate the new species Marcusenius desertus sp. nov. for the Cunene River mouth population.     

New taxa and combinations in Old World Urticaceae

In anticipation of the publication of full revisions, a diagnosis of a new species of Droguetia is presented together with two new combinations for subspecies of Droguetia iners , a new combination for a species and a variety on Didymodoxa and a new combination for a subspecies of Australina pusilla . The name Elatostema trinerve Hochst. (1845) is shown to be conspecific with and antedate Urera cameroonensis Wedd. (1869). The new combination Urera trinervis is therefore made.     

Mitochondrial mismatch analysis is insensitive to the mutational process

Mismatch distributions are histograms showing the pattern of nucleotide (or restriction) site differences between pairs of individuals in a sample. They can be used to test hypotheses about the history of population size and subdivision (if selective neutrality is assumed) or about selection (if a constant population size is assumed). Previous work has assumed that mutations never strike the same site twice, an assumption that is called the model of infinite sites. Fortunately, the results are surprisingly robust even when this assumption is violated. We show here that (1) confidence regions inferred using the infinite- sites model differ little from those inferred using a model of finite sites with uniform site-specific mutation rates, and (2) even when site- specific mutation rates follow a gamma distribution, confidence regions are little changed until the gamma shape parameter falls well below its plausible range, to roughly 0.01. In addition, we evaluate and reject the proposition that mismatch waves are produced by pooling data from several subdivisions of a structured population.