Biodiversity & limnological functioning of the Malagarasi-Moyovosi wetlands, western Tanzania “Results and Discussion”

Biodiversity surveys

The herpetology surveys, lead by S. Loader, were the first systematic geographic sampling with a focus on frogs in western Tanzania.  Previous data was limited with only eight recorded frog species (Loveridge, 1942) – this Fig. 2.  Limnological sampling, clockwise from upper left, a) sampling physical paramenters at midpoint of headwater stream, b) Igombe river sampling with expedition zodiac, c) field titrations of Winkler reactions (productivity analyses), d) limno team uses dugout pirogue to find midpoint in swampy waterway Igombe river headwaters at Lake Nyamagoma, e) limno sampling with plankboat  & armed guard in Lake Sagara, f), midpont water sampling and incubations in Luiche River, Ujiji, g) water chemisty in field lab, Igamba Falls, h) (center) spectrophotometric work in TAFIRI-Kigoma lab.

survey brings the total to 21 species. The real diversity is certainly higher, as our sampling was done during the dry season, which is sub-optimal for amphibians.  Moreover, complete herpetological sampling requires yearround monitoring and stationary sampling methods such as pit traps. Nevertheless, as a result of our surveys there are some species range extensions and potentially some new species. Detailed morphological and genetic work will be carried out to investigate this further. The overall pattern is that the Malagarasi amphibian fauna shows similarities to the widespread East African lowland assemblages, rather than the Highlands of East Africa, where no single species is shared (Poynton et al. submitted). We recorded other herps (crocodile, python) and attempted to collect caecilian amphibians (none were found, which may indicate a range limit) and did collect typhlopid (blind) snakes during the expedition. The collections made during this expedition will provide a basis for an authoritative guide to amphibians of Western TZ (Loader, et al. in prep.).

The ichthyology sampling, lead by J. Friel, was extremely successful and recovered an estimated 75 fish species (60 of which are identified to date) which is approximately 3/4 of the recorded fish fauna in the whole basin.  This is an impressive recovery rate for one collection trip and indicates that the fish diversity is likely to increase significantly with further taxonomic work and further collections.  Currently we know that we collected minimum of three new species, but it is highly likely that more will be recovered as work proceeds on the collections.  Two new species (one catfish and one cichlid) were found only in the Igamba Falls area and are currently being described.  One of the newly discovered catfish may turn out to be a new basal genus that is the sister group to all other Chiloglanis, thus significantly improving our understanding of evolution in this important clade.

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The malacology sampling, lead by E. Michel, was similarly extremely successful with discovery of several new species and collection of the potential Tanganyika ‘outgroup’ Potadomoides pelseneeri (previously thought to be endangered or extinct, but we found it in very large numbers). Among the gastropods we found as many as five probable new species, some with apparent Congolese affinity.  One new species, unique to the Igamba Falls area, is highly unusual and will certainly be the focus of taxonomic and conservation interest. Taxonomic work is proceeding on these species and descriptions are planned for publication in the next year.  We were able to provide the first samples of the medically important snails Bulinus and Biomphalaria from this region for a study of genetics of schistosome (bilharzia) vectors and similarly the first tissue samples of the land snail Trochonanina that will allow testing a major hypothesis on faunal origins (Naggs & Raheem, 2005).  We also made the first large-scale collection of bivalves in the area.

Although effective taxonomic collections are best done with a focus on particular taxa, by experts, we were able to make preliminary collections of crustaceans, insects and diatoms.  These are currently being examined by specialists for identification (listed below in the logistics section) and may also be used for expanded systematic coverage in evolutionary studies.  Among crustaceans we collected shrimp that are the first from the region, are potential local endemics, and complement a larger study of elevated endemism in freshwater shrimp in eastern Tanzania.   Our collections of crabs did not reveal any novel taxa, but the common, widely distributed scavenger we found were of unusually large sizes. Our entomology collections include several new species of mayflies and the first western Tanzania addition to phylogenetic and distribution studies of African mayflies and dragonflies.
Collections are in the process of being accessed, with type specimens to be deposited in the Natural History Museum,  London  (molluscs,  herps,  insects),  and  Cornell  University  (fish)  and  paratypes  in  the  National Museums of Tanzania and TAFIRI-Kigoma with accurate labelling after the taxonomic work is completed.
We were highly alert to the presence of the exotic, destructive South American water hyacinth (Eichhornia crassipes), which has been recently introduced into Lake Tanganyika (K. West, pers. comm.).  We did not find evidence that it has colonized the areas of the Malagarasi wetlands we visited, however we observed a small clump of water lettuce (Pistia stratiotes) at one place in Lake Sagara.

Our aquatic surveys of the remote Igamba Falls area are apparently the first of their kind and revealed a number of new fish and mollusk species, making this site not only of special interest, but also of special concern as it is under discussion for hydropower installation.  Although this site has been discussed for hydropower for 10 years or so and is not the highest rated among possibilities in the region (www.ssea.snclavalin.com/pdf/SSEA_Bulletin_no3.pdf) we are aware it is still currently under active consideration as a WB fact-finding team visited the site in August 2005.  Our aquatic sampling there was of very limited duration and we strongly advocate detailed biodiversity work be continued in the region.

Updated: November 25, 2015 — 9:53 am
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