Home  About us  Contact
 

Usambara Mountains (usambara + mountain)

Distribution by Scientific Domains
Life Sciences100%

Kinds of Usambara Mountains

  • east usambara mountain
    		•

    Selected Abstracts

    Mistletoe (Tapinanthus bangwensis Reichenbach) infestation of indigenous and non-indigenous trees at Amani Nature Reserve, Tanzania

    AFRICAN JOURNAL OF ECOLOGY, Issue 1 2001
    L. M. Lekunze
    Abstract A survey of Tapinanthus bangwensis was carried out in a plantation in the botanic garden at Amani Nature Reserve, which forms part of the East Usambara Mountain, located in the north-east of Tanzania. A total of 169 trees were examined on four transects of 100 × 50 m (5000 m2) each, located about 700 m apart. Three treatment transects were established in open woodland with a control transect in the closed canopy. Out of 101 trees (81 non-indigenous and 20 indigenous) examined in the open canopy, T. bangwensis was present on 24; eighteen non-indigenous and six indigenous. Of all the infested trees, a non-indigenous species, silky oak (Grevillea robusta) was the most common (37.4%), followed by an indigenous species, mzindanguruwe (Blighia unijugata) with 16.6%. Chi-squared tests showed that there was no significant difference in frequency of infestation between non-indigenous and indigenous species (,2 = 0.715, P = 0.5826). t -Testing showed that T. bangwensis preferred taller and larger trees (t = , 3.930, P = 0.0002 and t = , 2.416, P = 0.0175, respectively). No T. bangwensis was found on the 68 trees examined in the closed canopy. Résumé On a réalisé une étude sur Tapinanthus bangwensis dans une plantation du jardin botanique de la Réserve Naturelle d'Amani qui fait partie de la East Usambara Mountain, au nord-est de la Tanzanie. On a examiné un total de 169 arbres sur quatre transects de 100 mètres sur 50 (5000 m2) chacun, situés à environ 700 mètres l'un de l'autre. On a créé trois transects de traitement dans la forêt claire et un de contrôle dans la canopée fermée. Sur les 101 arbres (81 non indigènes et 20 indigènes) examinés dans la canopée ouverte, T. bangwensisétait présent sur 24, 18 non indigènes et six indigènes. Parmi les espèces infestées, une espèce non indigène, Grevillea robusta, était la plus commune (37,4%), suivie par une espèce indigène, mzindanguruwe (Blighia unijugata) avec 16,6%. Des tests de ,2 ont montré qu'il n'y avait pas de différence significative dans les fréquences d'infestation des espèces indigènes et non indigènes (,2 = 0,715, P = 0,5826). Les tests de t ont montré que T. bangwensis préférait les arbres plus hauts et plus gros (t = - 3,930, P = 0,0002 et t = - 2,416, P = 0,0175, respectivement). On n'a pas trouvé de T. bangwensis sur les 68 arbres examinés en canopée fermée. [source]

    Inbreeding and inbreeding depression in a threatened endemic plant, the African violet (Saintpaulia ionantha ssp. grotei), of the East Usambara Mountains, Tanzania

    AFRICAN JOURNAL OF ECOLOGY, Issue 3 2010
    Johanna Kolehmainen
    Abstract Mating among closely-related individuals in small and isolated plant populations may result in reduced vigour of the inbred offspring, i.e. inbreeding depression, especially in naturally outbreeding plants. Occurrence of inbreeding and inbreeding depression was studied in Saintpaulia ionantha ssp. grotei, a threatened endemic plant species with a narrow ecological amplitude from the East Usambara Mountains. The level of inbreeding (measured as the fixation index, F) was investigated in twelve populations by analyzing variation at one microsatellite marker locus. The effect of one generation of selfing and outcrossing on the progeny fitness was studied by controlled crosses in two small patches that differ in the level isolation. The fixation index (F) across the populations was on the average 0.21 and varied among the populations from substantial inbreeding (F = 0.58) to surplus heterozygosity (F = ,0.29). High inbreeding depression (,) was observed at early and late stages of the life-cycle. The isolated patch exhibited lower inbreeding depression than did the non-isolated patch. The results of this study suggest that inbreeding and subsequent inbreeding depression are potential threats to the survival of Saintpaulia populations. Résumé L'accouplement d'individus étroitement liés, dans des petites populations végétales isolées, peut aboutir à une vigueur moindre de la progéniture de même souche, c'est-à-dire une dépression due à l'endogamie, spécialement chez des plantes qui sont naturellement exogames. L'occurrence de l'endogamie et de la dépression qui y est liée a étéétudiée chez le Saintpaulia ionantha spp. grotei, une plante endémique menacée qui n'a qu'une faible amplitude écologique dans l'est des Usambara Mountains. On a recherché le taux d'endogamie (mesuré par l'indice de fixation F) dans 12 populations en analysant la variation d'un locus microsatellite marqueur. L'effet d'une génération d'auto- et d'allofécondation sur l'aptitude (fitness) de la progéniture a étéétudié par des croisements contrôlés dans deux petites parcelles dont le degré d'isolement différait. L'indice de fixation F dans les populations était en moyenne de 0,21 et il variait d'une autofécondation substantielle (F = 0,58) à une hétérozygosité en surplus (F = ,0,29). Une forte dépression due à l'endogamie (,) a été observée aux stades précoce et tardif du cycle vital. La parcelle isolée a présenté une dépression liée à l'endogamie moins forte que celle de la parcelle non isolée. Les résultats de cette étude suggèrent que l'auto-fécondation et la dépression qui en résulte sont des menaces potentielles pour la survie des populations de Saintpaulia. [source]

    Reproductive ecology of three endangered African violet (Saintpaulia H. Wendl.) species in the East Usambara Mountains, Tanzania

    AFRICAN JOURNAL OF ECOLOGY, Issue 2 2006
    Johanna K. Kolehmainen
    Abstract Knowledge of the reproductive biology of endangered plants is essential for their effective conservation. It also provides important information for understanding the evolutionary processes that affect speciation, thus helping the definition of proper units for conservation in endangered plants with problematic taxonomy. We studied the reproductive potential and possibility for hybridization in the endangered genus Saintpaulia (Gesneriaceae) by examining flowering phenology, flower and seed production and pollination of three sympatric cross-compatible Saintpaulia species in the East Usambara Mts., Tanzania. The synchrony observed in flowering in S. confusa and S. difficilis may enable hybridization between these two species, whereas partial phenological separation may contribute to the integrity of S. grotei. Although the level of flower abortion is high in S. confusa, each pollinated flower yields about 1000 seeds. Saintpaulia confusa produces fruits following both self- and cross-pollination but spontaneous self-pollination seems not to occur. Thus, seed production depends on sufficient pollinator service. Floral heteromorphy (i.e. enantiostyly) and bee pollination are likely to further enhance cross-pollination, suggesting that the genus predominantly outcrosses. Thus, Saintpaulia populations are likely to suffer from negative effects of inbreeding if they become small and isolated. Résumé La connaissance de la biologie de la reproduction des plantes en danger est essentielle pour l'efficacité de leur conservation. Elle fournit aussi des informations importantes pour la compréhension des processus évolutifs qui touchent la spéciation et donc pour la définition d'unités adéquates pour la conservation de plantes en danger dont la taxonomie pose des problèmes. Nous avons étudié le potentiel reproductif et la possibilité d'hybridation du genre menacéSaintpaulia (Gesneriaceae) en examinant la phénologie de la floraison, la production de fleurs et de semences, et la pollinisation de trois espèces de Sainpaulia sympatriques de l'est des Usambara Mountains, en Tanzanie, qui peuvent se croiser. La synchronie de la floraison observée avec S. confusa et S. difficilis permet peut-être l'hybridation entre ces deux espèces, tandis qu'une séparation phénologique partielle pourrait contribuer à conserver l'intégrité de S. grotei. Même si le niveau d'avortement est élevé pour les fleurs de S. confusa, chaque fleur fécondée produit environ 1000 semences. S. confusa produit des fruits après la pollinisation par sa propre espèce ou par croisement avec une autre espèce, mais il semble qu'il n'y ait pas d'auto-pollinisation spontanée. Donc, la production de semences dépend de l'abondance des pollinisateurs. L'hétéromorphie florale (i.e. énantiomorphisme) et la pollinisation par les abeilles sont susceptibles de stimuler la pollinisation croisée, ce qui suggère que ce genre se reproduit surtout de cette façon. Il est donc probable que les populations de Saintpaulia risquent de souffrir des effets négatifs de l'inbreeding si elles deviennent trop petites et isolées. [source]

    Power to detect trends in ecological indicators in the East Usambara Mountains, Tanzania

    AFRICAN JOURNAL OF ECOLOGY, Issue 4 2003
    William D. Newmark
    Abstract We evaluated the statistical power of monitoring protocols to detect, over a 10-year period, trends in indices of abundance of primates, hornbills and forest interior dung beetles and growth rates of epiphytic ferns in the Amani Nature Reserve, in the East Usambara Mountains, Tanzania. Local technicians are responsible for the day-to-day gathering of data. The existing monitoring protocols for blue monkey, silver-cheeked hornbills, trumpeter hornbills, forest interior dung beetles and Asplenium nidus have sufficient statistical power (>0.80) to detect trends of 65% or less over a 10-year period. Monitoring protocols for black and white colobus and Asplenium holstii have lower statistical power (<0.80). We therefore conclude that the majority of monitoring protocols of the East Usambara Ecological Monitoring Project have the capacity both logistically and statistically to detect long-term trends in important functional groups in the East Usambara Mountains. Résumé Nous avons évalué le pouvoir prédictif des protocoles de surveillance continue pour détecter, sur une période de 10 ans, la tendance des indices d'abondance des primates, des calaos et des bousiers de forêt, et des taux de croissance des fougères épiphytes dans la Réserve Nature d'Amani, dans les East Usambara Mountains, en Tanzanie. Des techniciens locaux sont responsables de la récolte quotidienne des données. Les protocoles actuels de surveillance continue des cercopithèques à diadème, des calaos Ceratogymna brevis et Cerratogymna bucinator, des bousiers de forêt et d'Asplenium nidus ont un pouvoir prédictif suffisant (>0.80) pour déceler des tendances de 65% ou moins sur 10 ans. Les protocoles de surveillance continue du colobe blanc et noir et d'Asplenium holstii ont un pouvoir prédictif plus faible (<0.80). Nous avons donc conclu que la majorité des protocoles de surveillance continue du Projet de Surveillance Écologique Continue des East Usambara avaient les capacités logistique et statistique, de déceler des tendances à long terme de groupes fonctionnels importants dans les East Usambara Mountains. [source]

    Phylogeny, phylogeography, and geographic variation of Sylvisorex howelli (Soricidae), an endemic shrew of the Eastern Arc Mountains, Tanzania

    JOURNAL OF ZOOLOGY, Issue 4 2005
    William T. Stanley
    Abstract The Eastern Arc Mountains of eastern Africa are notable for the high levels of endemism exhibited by various forest-dwelling organisms of this ancient montane archipelago. There has been virtually no assessment of the variation among populations of small mammal species living on these unique mountains, but recent faunal surveys have produced sufficient material to initiate such studies. Cranial morphometric and DNA sequence data were examined from six populations of Sylvisorex howelli Jenkins, 1984, an endemic shrew found in several different massifs of the Eastern Arc Mountains, to assess variation across the archipelago in the context of various hypotheses of historical biogeography. Twenty-two cranial measurements were analysed using principal components analysis. Age classes (based on tooth wear) and sex had little effect on the variation exhibited by the variables studied. Overall, specimens of S. howelli from the East Usambara Mountains are smaller than specimens from other known populations. The mitochondrial ND2 and 12S rRNA genes from representatives of each montane population of S. howelli in addition to several crocidurine taxa from eastern Africa and three soricine outgroup species were sequenced to assess phylogenetic relationships among these taxa. Neither maximum likelihood, maximum parsimony, nor Bayesian analyses support monophyly of the genus Sylvisorex, but S. howelli populations were consistently recovered as a well-supported clade. Over 40 individuals of S. howelli from six disjunct montane ranges, comprising the entire known distribution of the species, were sequenced for 504 base pairs of ND2 to investigate phylogeographic patterns. Phylogenetic analysis recovered six reciprocally monophyletic haplotype clades grouped by locality. Branch lengths are consistent with relatively long periods of isolation among populations from the Uluguru, Ukaguru, Nguru, Nguu, East Usambara and West Usambara Mountains, with low levels of diversity observed within each population. These results are interpreted within the historical context of the Eastern Arc Mountains. [source]

    Ranging behavior and habitat selection of terrestrial insectivorous birds in north-east Tanzania: implications for corridor design in the Eastern Arc Mountains

    ANIMAL CONSERVATION, Issue 5 2010
    W. D. Newmark
    Abstract Understanding the ranging behavior and habitat selection of understory tropical birds is important for corridor design and enhancing functional connectivity in fragmented tropical landscapes. Here we report on the ranging behavior and habitat selection of three terrestrial insectivorous bird species, the spot-throat Modulatrix stictigula, Usambara thrush Turdus roehli and orange ground thrush Zoothera gurneyi, in the East (EUM) and West (WUM) Usambara Mountains in north-east Tanzania. Based on 5945 locations and 3676 bird radio-tracking hours conducted between 2001 and 2008 at four study sites in the EUM and WUM, we determined that the 95% kernel home range and 50% kernel core range for the spot-throat, Usambara thrush, and orange ground thrush are similar yet large (aggregate mean home range=10.3±1.1 ha; aggregate mean core range 1.5±0.4 ha); that these species are adverse to crossing non-forested openings , no bird was recorded over the course of the study to cross a non-forested opening >15 m; and that the most extinction-prone species in our study system, the spot-throat and Usambara thrush, preferentially used slightly disturbed and primary forest, respectively. These results indicate that maintaining continuous forest cover and minimizing forest disturbance in corridors in the Eastern Arc Mountains is important for enhancing their habitat suitability for these species. [source]

    Effects of Tea Plantations on Stream Invertebrates in a Global Biodiversity Hotspot in Africa

    BIOTROPICA, Issue 4 2009
    Olly van Biervliet
    ABSTRACT Tropical stream ecosystems in montane forest watersheds are important centers of endemism and diversity and provide essential ecosystem services. These habitats are subject to a variety of stressors, including the conversion of adjacent terrestrial habitats from forest to agriculture, but the impacts of these anthropogenic effects are largely unknown because of the paucity of studies in these systems. In montane habitats in the wet tropics, large-scale cultivation of tea is common and can represent an important source of income at local and national scales. However, little is known about how tea cultivation impacts adjacent stream ecosystems. In this study, we examine stream macroinvertebrate assemblages in a biodiversity hotspot the East Usambara Mountains, Tanzania. Specifically, we compare diversity of macroinvertebrate assemblages found on cobbles in stream riffles in watersheds dominated by forest with those surrounded by tea cultivation. We found that streams surrounded by tea were characterized by significantly lower dissolved oxygen and had lower total estimated species richness and number of families. Furthermore, the richness of invertebrate taxa known to be sensitive to anthropogenic disturbance were substantially reduced in tea streams and general assemblage-level analysis shows significant differences in the composition of macroinvertebrate assemblages between tea and forested streams. Our results suggest that tea cultivation may reduce stream habitat quality and biodiversity in the East Usambaras. Further research is needed to evaluate the effects of tea cultivation on streams over longer times scales and to address methods for minimizing negative effects of agriculture on montane stream communities. [source]

    Tanzanian Forest Edge Microclimatic Gradients: Dynamic Patterns,

    BIOTROPICA, Issue 1 2001
    William D. Newmark
    ABSTRACT Air temperature, vapor pressure deficit, and light intensity microclimatic gradients were examined along four forest edge and four paired forest interior transects in the East and West Usambara Mountains, Tanzania. Between 14 August 1995 and 11 August 1998, 287, 282, and 196 air temperature, vapor pressure deficit, and light intensity gradients, respectively, were measured along the four forest edge and four interior transects. The relationship between microclimate and distance from the forest edge was examined using piecewise linear regression. All microclimatic gradients were classified into one of nine shapes based on the sign and the size of the two estimated slopes. The relative frequency in the shapes of 65 percent of air temperature gradients, 52 percent of vapor pressure deficit gradients, and 62 percent of light intensity gradients along forest edge transects exceeded the relative frequency of these same shapes along forest interior transects, indicating that a majority of the forest edge microclimatic gradients measured were influenced by edge effects. Yet this result also indicated that approximately one-third of all air temperature and light intensity gradients and nearly one-half of all vapor pressure deficit gradients recorded during this study were affected by factors independent of edge effects per se, and that forest edge microclimatic gradients were temporally nonconstant. For air temperature and vapor pressure deficit gradients, low spatial but high temporal variation existed in estimated edge width and the relative change in microclimate between the forest edge and interior. For light intensity gradients, both high spatial and temporal variability characterized estimated edge width and relative change in microclimate between the forest edge and interior. The pooled mean edge width and relative change in microclimate between die forest edge and interior across the four forest edge transects for air temperature, vapor pressure deficit, and light intensity gradients were 94.1 m and 2.00°C, 82.6 m and 0.29 kPa, and 60.5 m and 10.6 joules/sec/m2, respectively. These results suggest that forest edge microclimatic gradients in general may be inherently dynamic and nonconstant. [source]