Variation of tsetse fly abundance in relation to habitat and host presence in the Maasai Steppe,Tanzania

Human activities modify ecosystem structure and function and can also alter the vital rates of vectors and thus the risk of infection with vector‐borne diseases. In the Maasai Steppe ecosystem of northern Tanzania, local communities depend on livestock and suitable pasture that is shared with wildlife, which can increase tsetse abundance and the risk of trypanosomiasis. We monitored the monthly tsetse fly abundance adjacent to Tarangire National Park in 2014–2015 using geo‐referenced, baited epsilon traps. We examined the effect of habitat types and vegetation greenness (NDVI) on the relative abundance of tsetse fly species. Host availability (livestock and wildlife) was also recorded within 100×100 m of each trap site. The highest tsetse abundance was found in the ecotone between Acacia‐Commiphora woodland and grassland, and the lowest in riverine woodland. Glossina swynnertoni was the most abundant species (68%) trapped throughout the entire study, while G. pallidipes was the least common (4%). Relative species abundance was negatively associated with NDVI, with greatest abundance observed in the dry season. The relationship with the abundance of wildlife and livestock was more complex, as we found positive and negative associations depending on the host and fly species. While habitat is important for tsetse distribution, hosts also play a critical role in affecting fly abundance and, potentially, trypanosomiasis risk.     

Seasonal variations in the distribution and abundance of the tsetse fly,Glossina morsitans morsitans in eastern Zambia

The seasonal changes in the distribution of Glossina morsitans morsitans Westwood (Diptera: Glossinidae) and its main host, cattle, were examined in a cultivated area of the plateau of eastern Zambia. During four consecutive years, the tsetse and cattle populations were monitored along a fly-round transect traversing the two main vegetation types in the study area. These were miombo, a one-storied open woodland with the genera Brachystegia and Julbernardia dominant, and munga, a one- or two-storied woodland where the principal tree genera were Acacia, Combretum and Terminalia. Concurrently, a capture/mark/release/recapture (CMRR) exercise was conducted along two other transects also traversing both vegetation types. The index of apparent abundance of tsetse (IAA) in miombo increased at the beginning of the rainy season (November), reached its peak at the end of the rainy season (April) and was low during the cold season (May to late August), but especially the hot dry season (September to late October). The IAA of tsetse in munga showed a pattern that was the reverse of that in miombo. The seasonal changes in the IAA of tsetse in both vegetation types were in accordance with changes in the movement patterns of tsetse between the two vegetation type as observed using CMRR. The distribution and abundance of cattle along the transect also showed a seasonal trend. This was especially so in munga, during the first three years of observations, where cattle abundance increased gradually from June onwards, reached a maximum at the end of the hot dry season (October-November) and declined steeply at the start of the rainy season (November-December). In both vegetation types, the monthly mean IAA of tsetse was positively correlated with the abundance of cattle in the previous month. It is concluded that the distribution of tsetse in cultivated area of the eastern plateau of Zambia undergoes substantial seasonal changes, which can partly be attributed to changes in the distribution of cattle. The implications of these observations for the control of tsetse are discussed.     

Seasonal variation in growth of Mastomys natalensis (Rodentia: Muridae) in Morogoro, Tanzania

The paper describes seasonal growth variation in a free living population of Mastomys natalensis (Smith, 1834) from Morogoro, Tanzania. Growth patterns are associated with rainfall patterns. Young animals enter a growth stop at the end of the dry season (October-November) and growth is only resumed after the first heavy rains. Reproduction is more related to size than to age. If the heavy rains come early in the rainy season, animals start reproducing in the beginning of the year. The resulting young reach their maximal size without growth stop and start reproducing immediately. Possible causes for the growth stop are discussed. Growth phenomena are thought to explain at least partially the relation between rainfall and reproduction in Mastomys .

Résumé

Cet article décrit la variation de croissance saisonnière d'une population de Mastomys natalensis (Smith, 1834) vivant en libertéà Morogoro, en Tanzanie. Les graphiques de croissance sont associés à ceux des chutes de pluie. Les jeunes animaux connaissent un arrêt de la croissance à la fin de la saison sèche (octobre-novembre) et la croissance ne reprend qu'après les premières fortes pluies. La reproduction est plus liée à la taille qu'à l'âge. Si les fortes pluies surviennent tôt en saison des pluies, les animaux commencent à se reproduire au début de l'année. Les jeunes atteignent alors leur taille maximale sans avoir connu d'arrêt de croissance et commencent à se reproduire immédiatement. On pense que les phénomènes de croissance expliquent au moins partiellement la relation entre les chutes de pluie et la reproduction chez Mastomys .     

Seasonal variation in understorey bird species diversity and abundance in the Uluguru Nature Reserve,Tanzania

The Uluguru Mountains form a component block of the Eastern Arc Mountains of Tanzania and Kenya and are known for a high degree of endemic vertebrate and plant taxa. Among the Eastern Arc Mountains, the Uluguru Mountains rank second in the number of endemic species. Although the forests in these mountains have received considerable ornithological attention, studies on how forest bird communities in the available low elevation forests are affected by seasons remain patchy and sporadic. Such studies are important because in the Uluguru Mountains, forest destruction in the lower slopes has been severe to an extent that there is very little substantial forest survives below 900 m above sea level. Using mist netting, seasonal variation in understorey bird communities in the remaining low elevation forests in the Uluguru Nature Reserve was assessed between 2005 and 2011. Species diversity and relative abundance of the birds were higher during the cold season in comparison with the hot season possibly due to seasonal elevational movements of some species. Elevational migrants made a large proportion of the avifauna in the study area. The results suggest that low altitude forests are important cold season refugia of elevational migrants and these forests need continual protection.     

Seasonal variation in diversity and abundance of understorey birds in Bunduki Forest Reserve,Tanzania: evaluating the conservation value of a plantation forest

Plantation forests generally support lower bird diversity than natural forests. However, in some instances the plantations have been found to provide suitable habitat for a number of bird species. In the Eastern Arc Mountains, there is limited knowledge how understorey birds, some of which make seasonal altitudinal movements, use plantations. Using mist netting we assessed seasonal use of the plantation forest by the understorey bird community in Bunduki Forest Reserve in the Uluguru Mountains. Species diversity and capture rates were significantly higher during the cold season than during the hot season possibly due to seasonal altitudinal migration by some species. The use of plantations by those species that make seasonal altitudinal movements shows that plantation forests can enhance indigenous biodiversity by enabling connectivity between two or more natural forest patches. Our findings suggest that in a situation where there is no natural forest, an exotic plantation with suitable indigenous understorey cover can help in protection of birds, including endemic and near-endemic species.     

Use of indigenous ecological knowledge of the Maasai pastoralists for assessing rangeland biodiversity in Tanzania

This paper incorporates the indigenous ecological knowledge (IEK) of the Maasai pastoralists and ecological methods to assess effects of grazing and cropping on rangeland biodiversity at macro‐ and micro‐landscape scales in northern Tanzania. The joint surveys with pastoralists identified indicator plant species and their associations with micro‐landscapes and livestock grazing suitability (i.e. for cattle and small ruminant grazing), while traditional calf‐pasture reserves (alalili pl. alalilia) were evaluated for preservation of rangeland biodiversity. The macro‐landscapes comprising the cool high plateau (osupuko pl. isipuki) and montane forest highland (endim) were included in the survey. At micro‐landscape scales, the osupuko was classified into uplands (orkung'u), slopes (andamata) and dry valley bottomlands (ayarata). The micro‐landscapes were assessed in terms of herbaceous plant species and woody species richness and risks of soil erosion. Biodiversity varied at both the macro‐ and micro‐landscape scales and in accordance with the land‐use types. Greater plant species diversity and less erosion risks were found in the pastoral landscapes than in the agro‐pastoral landscapes. The calf‐grazing pastures had greater herbaceous species richness than the non‐calf pastures, which in turn had more woody species. The study concludes that the indigenous systems of landscape classification provides a valuable basis for assessing rangeland biodiversity, which ecologists should incorporate into ecological surveys of the rangelands in East Africa in the future.     

Butterfly species richness and abundance in the Katavi ecosystem of western Tanzania

We sampled butterflies in six different habitat types in and around Katavi National Park, a remote reserve consisting primarily of miombo woodland and seasonal lakes in western Tanzania. Blendon traps set for 531 trap days and 143 h of butterfly netting at 35 sites yielded 186 species from five families over a 4‐month period during the wet season. Eight of these species constituted possible range extensions. Butterfly abundance and species richness were low in cultivated habitats but high in open riverine habitats; many butterfly species were found only in seasonally flooded grassland. This study constitutes the first butterfly species inventory from this poorly‐known national park, shows that protection of dry season water sources provides an important conservation service for invertebrates as well as large mammals, and that increased cultivation outside miombo parks can reduce local butterfly diversity.     

Haemolymph lectin and the maturation of trypanosome infections in tsetse

The tsetse immune system has recently been shown to be involved in trypanosome maturation; lectin secreted in the midgut, normally responsible for preventing the establishment of midgut infections, induces established midgut trypanosomes to mature. We now show that a second lectin, present in tsetse haemolymph, is essential to complete the maturation process. Interactions between tsetse lectins and parasite surface coats probably determine trypanosome transmissibility and may be partly responsible for the distribution of trypanosomiasis in Africa.     

Ovulation, insemination and mating in the tsetse fly Glossina pallidipes

ABSTRACT. Analyses of the ovulation, insemination and mating of female Glossina pallidipes Austen, were carried out in the field and laboratory. In unmated females, ovulation was delayed until at least the fifteenth day of adult life. The predictable pattern of growth and development of eggs was used to age nulliparous females to the nearest day in the field. Inseminated females first appeared at 5–6 days old and most females became inseminated at 8–10 days of age. There were no significant differences in the age at insemination in Zimbabwe or Kenya. Ovulation had occurred in the field by 10–11 days old. Mating therefore occurs at or just before ovulation. Females were able to mate at up to 12 days old and still produce a viable larva from their first egg. In laboratory flies originating from Uganda, factors which reduced and minimized the effects of disturbance, maximized insemination rate, so that under the best conditions the age at mating was identical to that found in the field. Nevertheless, the insemination rate of Fl generation Zimbabwe flies reared from wild-caught females was negligible. The differences in the laboratory mating behaviour of the Zimbabwe flies and the flies from the long-established colony of Uganda origin, are considered to be due to wild G. pallidipes being easily disturbed under laboratory conditions, whereas colony breeding rapidly selects for passivity. The concept of gross differences in G. pallidipes mating behaviour between geographic areas in thus rejected.     

The influence of sex and fly species on the development of trypanosomes in tsetse flies

Unlike other dipteran disease vectors, tsetse flies of both sexes feed on blood and transmit pathogenic African trypanosomes. During transmission, Trypanosoma brucei undergoes a complex cycle of proliferation and development inside the tsetse vector, culminating in production of infective forms in the saliva. The insect manifests robust immune defences throughout the alimentary tract, which eliminate many trypanosome infections. Previous work has shown that fly sex influences susceptibility to trypanosome infection as males show higher rates of salivary gland (SG) infection with T. brucei than females. To investigate sex-linked differences in the progression of infection, we compared midgut (MG), proventriculus, foregut and SG infections in male and female Glossina morsitans morsitans. Initially, infections developed in the same way in both sexes: no difference was observed in numbers of MG or proventriculus infections, or in the number and type of developmental forms produced. Female flies tended to produce foregut migratory forms later than males, but this had no detectable impact on the number of SG infections. The sex difference was not apparent until the final stage of SG invasion and colonisation, showing that the SG environment differs between male and female flies. Comparison of G. m. morsitans with G. pallidipes showed a similar, though less pronounced, sex difference in susceptibility, but additionally revealed very different levels of trypanosome resistance in the MG and SG. While G. pallidipes was more refractory to MG infection, a very high proportion of MG infections led to SG infection in both sexes. It appears that the two fly species use different strategies to block trypanosome infection: G. pallidipes heavily defends against initial establishment in the MG, while G. m. morsitans has additional measures to prevent trypanosomes colonising the SG, particularly in female flies. We conclude that the tsetse-trypanosome interface works differently in G. m. morsitans and G. pallidipes.     

喀斯特常绿落叶阔叶混交林物种多度与丰富度空间分布的尺度效应

物种多样性的空间分布格局及其尺度效应是生态学研究的重点,对于理解物种多样性的形成和维持机制以及生物多样性的管理和保护均具有重要意义。以贵州茂兰国家级自然保护区分布的亚热带原生性喀斯特常绿落叶阔叶混交林为研究对象,分析了2个1hm2(100m×100m)样地中物种多度和丰富度的空间分布特征及其与取样尺度的关系,采用方差和变异系数描述多度和丰富度在5个尺度(5m×5m,10m×10m,20m×20m,25m×25m,50m×50m)上的空间变异性。结果表明:(1)两个样地的物种多度和丰富度具有尺度依赖性特征;(2)由于多度具有叠加性,物种多度的方差随着尺度的增加呈线性增加,而变异系数呈线性下降;(3)丰富度的方差随尺度的增加表现出单峰分布的特征,在25 m×25 m尺度上达到最大值,变异系数则随取样尺度的增加而呈线性下降。研究表明,物种多度具有尺度推演规律,而丰富度却没有,因此,应慎重进行物种丰富度的尺度推演。在分析喀斯特森林物种多样性时,应注重尺度效应带来的影响。     

Tissue distribution and prevalence of Wolbachia infections in tsetse flies, Glossina spp

Tsetse flies Glossina spp. (Diptera: Glossinidae) harbor three different symbiotic microorganisms, one being an intracellular Rickettsia of the genus Wolbachia. This bacterium infects a wide range of arthropods, where it causes a variety of reproductive abnormalities, one of which is termed cytoplasmic incompatibility (CI) that, when expressed, results in embryonic death due to disruptions in fertilization events. We report here that in colonized flies, Wolbachia infections can be detected in 100% of sampled individuals, while infections vary significantly in field populations. Based on Wolbachia Surface Protein (wsp) gene sequence analysis, the infections associated with different fly species are all unique within the A group of the Wolbachia pipientis clade. In addition to being present in germ-line tissues, Wolbachia infections have been found in somatic tissues of several insects. Using a Wolbachia-specific PCR-based assay, the tissue tropism of infections in Glossina morsitans morsitans Westwood, Glossina brevipalpis Newstead and Glossina austeni Newstead were analysed. While infections in G. m. morsitans and G. brevipalpis were limited to reproductive tissues, in G. austeni, Wolbachia could be detected in various somatic tissues.     

Influence of temperature changes on larviposition rhythm in the tsetse fly, Glossina morsitans

ABSTRACT. The hourly and quarter-hourly distribution of larval deposition by female Glossina morsitans Westw. was studied at various temperatures. At constant temperature and humidity, peak larviposition occurred 8–9 h after lights on. The effect of confining the flies to daily (LD 12:12 h) regimes of at least twenty-five consecutive cycles that included a sudden increase in temperature of c. 6°C for 2 h was a significant reduction in depositions during each period of increased temperature, and a significant increase before the heat impulse. When the temperature was allowed to fall rapidly, larviposition rate doubled in the following 15 min.     

Neuroendocrine stimulation of uterine gland protein synthesis in the tsetse fly, Glossina morsitans

ABSTRACT. The uterine gland of the tsetse fly Glossina morsitans morsitans Westw. synthesizes a secretion which nourishes the developing larva in the uterus. Aqueous extracts of the brain have been shown to stimulate the synthesis of the protein and amino acid components of this secretion from L- [U-¹⁴C]leucine by uterine gland tubules in vivo and in vitro. A linear dose response relationship was demonstrated in vitro with extract concentrations ranging from 1 × 10^-4 to 1 × 10^-2 brains μl^-1. The maximum response, a > 300% increase in the rate of protein and amino acid synthesis, was achieved with as little as 1 × 10^-2 brains μl^-1 The concentration of active factor(s) in the brain declined during a single interlarval period coincident with the period of release of secretion associated with larval growth. The stimulatory activity in brain extracts was destroyed by proteolytic enzymes indicating that it is probably a protein or peptide. Results suggest that the active factor(s) is a hormone responsible for the stimulation of uterine gland protein synthesis essential for larval nutrition.     

Seasonal elevational movements of Eastern Olive Sunbird Cyanomitra olivacea in the Uluguru Mountains,Tanzania

Little is known about the seasonal elevational movements for most tropical avifauna species. Seasonal elevational movements of the Eastern Olive Sunbird Cyanomitra olivacea were studied along an elevational gradient from 600 to 1 500?m above sea level in the Uluguru Mountains, Tanzania, between May 2005 and February 2006. The recapture of ringed individuals along an elevational gradient across seasons provided evidence for the seasonal elevational movement of the Eastern Olive Sunbird in the Uluguru Mountains and the first documented evidence for this species in the Eastern Arc Mountains as a whole. Due to forest fragmentation and lack of corridors connecting high- and low-altitude forests in the Uluguru Mountains, the results have implications for conservation of the forest along the entire elevational gradient as well as for other forest bird species that have been documented to make seasonal elevational movements in the Uluguru Mountains and the entire Eastern Arc Mountains.     

Seasonal distribution and abundance of tsetse flies (Glossina spp.) in the Faro and Deo Division of the Adamaoua Plateau in Cameroon

Ten years after the large-scale tsetse control campaigns in the important cattle rearing areas of the Faro and Deo Division of the Adamaoua Plateau in Cameroon, the seasonal distribution and abundance of tsetse flies (Glossina spp.) were determined. During a period of 12 consecutive months (January-December 2005), the tsetse population was monitored along four trap transects consisting of a total of 32 traps and two flyround transects traversing the study area, which comprised the tsetse-infested valley, a buffer zone and the supposedly tsetse-free plateau. Throughout the study period, a total of 2195 Glossina morsitans submorsitans and 23 Glossina tachinoides were captured in the traps and 1007 G. m. submorsitans (78.8% male flies) were captured along the flyround transects. All G. tachinoides and almost all G. m. submorsitans were captured in the valley. Five G. m. submorsitans were captured in traps located in the buffer zone, whereas no flies were captured in traps located on the plateau. The index of apparent abundance (IAA) of G. m. submorsitans was substantially higher in the areas close to game reserves. In the remaining part of the valley, where wildlife is scarce and cattle are present during transhumance (dry season), the IAA of tsetse was substantially lower. In this part of the valley, the abundance of tsetse seemed to be associated with the presence of cattle, with the highest IAA during transhumance when cattle are present and the lowest apparent abundance during the rainy season when cattle have moved to the plateau. It is concluded that the distribution of tsetse in a large part of the valley undergoes substantial seasonal changes depending on the presence or absence of cattle. The repercussions of those findings for the control of tsetse in the valley and the probability of reinvasion of the plateau are discussed.     

Seasonal dynamics in mosquito abundance and temperature do not influence avian malaria prevalence in the Himalayan foothills

We examined seasonal prevalence in avian haemosporidians (Plasmodium and Haemoproteus) in migrant and resident birds in western Himalaya, India. We investigated how infection with haemosporidians in avian hosts is associated with temporal changes in temperature and mosquito abundance along with host abundance and life‐history traits (body mass). Using molecular methods for parasite detection and sequencing partial cytochrome b gene, 12 Plasmodium and 27 Haemoproteus lineages were isolated. Our 1‐year study from December 2008 to December 2009 in tropical Himalayan foothills revealed a lack of seasonal variation in Plasmodium spp. prevalence in birds despite a strong correlation between mosquito abundance and temperature. The probability of infection with Plasmodium decreased with increase in temperature. Total parasite prevalence and specifically Plasmodium prevalence showed an increase with average avian body mass. In addition, total prevalence exhibited a U‐shaped relationship with avian host abundance. There was no difference in prevalence of Plasmodium spp. or Haemoproteus spp. across altitudes; parasite prevalence in high‐altitude locations was mainly driven by the seasonal migrants. One Haemoproteus lineage showed cross‐species infections between migrant and resident birds. This is the first molecular study in the tropical Himalayan bird community that emphasizes the importance of studying seasonal variation in parasite prevalence. Our study provides a basis for further evolutionary study on the epidemiology of avian malaria and spread of disease across Himalayan bird communities, which may not have been exposed to vectors and parasites throughout the year, with consequential implications to the risk of infection to naïve resident birds in high altitude.     

How species richness and total abundance constrain the distribution of abundance

The species abundance distribution (SAD) is one of the most intensively studied distributions in ecology and its hollow‐curve shape is one of ecology's most general patterns. We examine the SAD in the context of all possible forms having the same richness (S) and total abundance (N), i.e. the feasible set. We find that feasible sets are dominated by similarly shaped hollow curves, most of which are highly correlated with empirical SADs (most R² values > 75%), revealing a strong influence of N and S on the form of the SAD and an a priori explanation for the ubiquitous hollow curve. Empirical SADs are often more hollow and less variable than the majority of the feasible set, revealing exceptional unevenness and relatively low natural variability among ecological communities. We discuss the importance of the feasible set in understanding how general constraints determine observable variation and influence the forms of predicted and empirical patterns.     

甘南亚高寒草甸稀有种对物种多样性和物种多度分布格局的贡献

稀有种不仅影响群落的物种多度分布格局, 同时也是α多样性的重要贡献者。本研究主要通过加性分配和Fortran软件的RAD程序包拟合的方法, 研究了甘南亚高寒草甸不同坡向物种多样性及多度分布格局的变化, 分析了物种多度分布格局及其α多样性的变化特征, 确定了稀有种在物种多度分布格局中的相对贡献。结果表明: (1)在南坡到北坡的变化中, 环境因子差异比较明显, 其中, 土壤全磷、有机碳、速效磷、碳氮比及含水量呈递增趋势; 土壤氮磷比和pH值呈递减趋势; 土壤全氮在西坡显著低于其他坡向, 而速效氮在所有坡向上差异不显著。(2)稀有种对群落物种多样性的影响在南-北坡向梯度上依次增大, 去除稀有种的影响在各坡向均高于去除非稀有种, 可见, 稀有种在甘南亚高寒草甸物种多样性中的相对贡献高于非稀有种。(3)各坡向的稀有种资源获取模式以随机分配占领模式(random fraction模型)为主, 而非稀有种则以生态位优先占领模式(geometric series模型)为主。由于稀有种有较大的扩散率, 在物种多样性较高的生态系统中, 物种之间的生态位重叠会更加明显, 从而抑制物种多样性的增加, 因此能达到维持原有物种多样性的目的。     

Rhythmic pulses of haemolymph pressure associated with parturition and ovulation in the tsetse fly,Glossina morsitans

Abstract Expulsion of the tsetse larva from the uterus of the female is preceded by 1–2 h of rhythmic pulses of haemolymph pressure that can be detected using a barographic technique. At first baseline pressure is maintained and all pulses are positive in relation to baseline. Then, about 1 h before parturition, baseline pressure increases, pulse intensity increases, and the pulses become both positive and negative in relation to baseline. Each pulse correlates with ‘bobbing’ action of the female's proboscis, the only external indication of this internal activity. A single large pressure pulse is observed at parturition, and thereafter the pressure level returns to the original baseline and pulsing action ceases. Around the presumptive time of ovulation, 1–2 h after parturition, another series of pressure pulses is observed. The pulses are the likely consequence of coordinated waves of muscular contraction that are essential preparation for successful parturition and ovulation.