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Lower Tana River (lower + tana_river)
Selected AbstractsImpact of rifting and hydrography on the genetic structure of Clarias gariepinus in eastern AfricaJOURNAL OF FISH BIOLOGY, Issue 5 2002C.S. Giddelo In a study of the genetic structure of Clarias gariepinus at the ND5 and ND6 loci of mitochondrial DNA using RFLP,PCR in 16 populations (267 fish), a total of 18 haplotypes was detected. The most common haplotype was EA1 and represented 46% of all genotypes. Three phylogenetic groups characterized the region, with the East African clade occurring between the western rift in the west, Lake Baringo in the north, the Indian Ocean in the east and the Rufiji River in the south. The Lower Tana River (unlike the Upper Tana River) and Lake Kamnarok grouped with the North clade, while the Ruaha River (tributary of the Rufiji River) represented a contact zone between the East and the South-central African clade. Genetic structure was distinct (FST=0·66), with the Lower Tana River and Lake Mtera forming specific units. Within the East clade, the Oloibortoto River, Upper Tana River and Lake Victoria each formed a distinct population. Lake Baringo grouped either with the eastern rift or the western rift depending on the analysis. Lake Jipe, the Pangani River, Rusizi River, Lake Edward, Nyabugogo River and the Luiche River clustered together. Among group variance explained 66·8% of the total variance; the impact of vicariance (rifting and uplifting) on the phylogeography was considerable. A distribution model of the catfish is proposed which combines the separation by rifting several million years ago with a high gene flow in the western rift due to historical connectivity among lakes and rivers. [source] Tree mortality due to an El Niño flood along the lower Tana River, KenyaAFRICAN JOURNAL OF ECOLOGY, Issue 1 2009Julie Wieczkowski Abstract This study investigated forest tree mortality as a result of the extremely strong 1997,1998 El Niño flood in Tana River, Kenya, directly tested how mortality varied in relation to tree species and diameter at breast height (DBH), and indirectly tested how mortality varied in relation to floodwater depth. The study forest was under 2 m of water for approximately 71 days, from December 1997 until February 1998. Twenty-five liana, subcanopy tree, and canopy tree species were selected based on their importance in the diet of the Tana River mangabey (Cercocebus galeritus Peters), a critically endangered primate endemic to the Tana River. Reproductive-sized individuals of these species were enumerated in 16.25 ha. I also enumerated trees killed by the El Niño flood, recorded their location in the forest, and measured their DBH. Ninety-two trees in fifteen species were killed by the flood. There were significant differences in mortality by species and by 0.25 ha quadrat. There were negative correlations between number of dead and DBH, number of dead and distance from the river, and per cent of quadrat killed and distance from the river. There appear to have been few long-term consequences of the El Niño flood in the forest or for the mangabeys. Résumé Cette étude s'est intéressée à la mortalité des arbres en forêt due à la très grave inondation causée en 1997,1998 par El Niño dans la rivière Tana, au Kenya. J'ai testé directement de quelle manière la mortalité variait selon l'espèce des arbres et leur diamètre à hauteur de poitrine (DBH), et indirectement comment elle variait avec la profondeur de l'eau. La forêt étudiée est restée sous deux mètres d'eau pendant environ 71 jours, de décembre 1997 à février 1998. Vingt-cinq espèces de lianes, d'arbres de sous-canopée et de la canopée ont été sélectionnées en fonction de leur importance dans le régime alimentaire du mangabey de la rivière Tana (Cercocebus galeritus Peters), une espèce de primate en danger critique d'extinction qui est endémique de cet endroit. Les individus de ces espèces ayant la taille requise pour se reproduire furent dénombrés sur 16,25 ha. J'ai aussi dénombré les arbres tués par l'inondation d'El Niño, noté leur emplacement dans la forêt et mesuré leur DBH. Quatre-vingt-douze arbres appartenant à 15 espèces ont été tués par cette inondation. Il y avait des différences significatives de mortalité selon les espèces et par quadrat de 0,25 ha. Il y avait des corrélations négatives entre le nombre d'arbres morts et leur DBH, entre le nombre d'arbres morts et la distance par rapport au lit du fleuve, et entre le nombre d'arbres morts par quadrat et cette distance. Il semble qu'il y ait peu de conséquences à long terme de cette inondation dans la forêt ou pour les mangabeys. [source] Ecological correlates of abundance in the Tana mangabey (Cercocebus galeritus)AMERICAN JOURNAL OF PRIMATOLOGY, Issue 3 2004Julie Wieczkowski Abstract I investigated the ecological correlates of abundance in the Tana mangabey (Cercocebus galeritus), one of the world's most endangered primates, with the goal of recommending management strategies. I systematically selected 31 forest fragments throughout the mangabey's 60-km distribution along the lower Tana River in southeastern Kenya. Within the 31 fragments, I measured vegetation structure, food abundance, and human forest product use in 107 belt transects, and conducted 370 mangabey surveys. I used a weighted multiple regression analysis to determine whether there was a dependence between the selected forest attributes and the mean number of mangabey groups per fragment. Fragment area and density of trees ,10 cm diameter at breast height (DBH) were the only variables that significantly correlated with the variation in mangabey abundance. No additional variables were significant when the analysis was limited to forest fragments inside the Tana River Primate National Reserve (TRPNR) or to fragments outside the TRPNR. When I estimated the resources available before recent human forest product use by adding nonharvested and harvested variables, the total basal area of the top 15 food species became significant. This was only within the TRPNR, however. Management, therefore, should focus on increasing forest area, density of trees ,10 cm DBH, and coverage of food trees throughout the mangabey's distribution. Solutions must be found for the problem of forest clearing, and forest product use must be better managed to protect the habitat of this critically endangered primate. The significance of food abundance only within the TRPNR suggests a need to collect dietary data from mangabey groups in fragments toward the southern limit of the mangabey's distribution, where plant species composition differs from that in fragments in which dietary data have been previously collected. Am. J. Primatol. 63:125,138, 2004. © 2004 Wiley-Liss, Inc. [source] Tana River Mangabey Use of Nonforest Areas: Functional Connectivity in a Fragmented Landscape in KenyaBIOTROPICA, Issue 5 2010Julie Wieczkowski ABSTRACT Habitat loss and fragmentation is a serious threat to biodiversity. Fragment isolation can be reduced if fragments are connected, either structurally through habitat corridors or functionally if the species can move through the surrounding matrix. One-way to evaluate landscape connectivity is to observe natural movements of animals within fragmented landscapes. The Tana River mangabey (Cercocebus galeritus) is an endangered monkey endemic to fragmented forests along the lower Tana River in Kenya, and who has been observed to move through matrix between fragments. One mangabey group moved through 1 km of matrix, while another group moved through two areas of matrix. I collected behavioral and ranging data on the latter group to describe its behavior and time spent in the matrix. Utilizing data from belt transects in the matrix and forest fragments, I characterized the vegetation structure of the matrix and compared it to the forests included in each group's home range. The group spent the majority of their time eating while in the matrix, and spent an average 36.4 min in one matrix area and 100 min in the other. The matrix is generally characterized by the highest measures for a nonforest attribute and the lowest measures for forest attributes. These results suggest that forest fragments are functionally, but not structurally, connected for the mangabey; a landscape approach to conservation, therefore, should be taken for the lower Tana River. Research investigating the limitations of the mangabey's ability to use the matrix is needed. [source] | ||||||||||