Gulella taitensis (Gulella taitensis)

Mohamed bin Zayed Species project number 11252526

The Eastern Arc Mountains host an unusually high proportion of rare and endemic animals and plants, and together with the coastal forests of Kenya and Tanzania, are recognised as one of the world’s 25 biodiversity hot-spots. The Taita Hills forest (3°15’–3030’S, 38°15’–38030’E), together with Sagala and Kasigau, form the northern most part of the Eastern Arc mountains, and are the sole representatives of this ancient geological formation within the Kenyan political boundaries.  The entire Taita Hills forest ecosystem is comprised of several isolated forest fragments located at the hills peaks.  The largest is Mbololo fragment with area of about 200 ha of moist forest.  To the south of Mbololo lies a series of ten other relatively small fragments collectively known as Dabida by the locals. These forests have been highly manipulated because of an increasing demand for agricultural land and natural resource exploitation by the expanding human population. The remaining indigenous forest in the Taita Hills is highly fragmented and despite the threat of their destruction, they support high levels of regionally rare and endemic plant and animal species. Thus, their protection, conservation and continued existence will also provide shelter for other endangered plants and animals.

Three land snail species; Thapsia buraensis, Ziingis radiolata and Gulella taitensis endemic to Taita Hills were the target species for this project. These three species are listed as globally threatened in the IUCN Red List. Zingis radiolata is classified as critically endangered in the IUCN Red list. It’s endemic to the Taita hills Forest in Kenya. The population trend was unknown as at last assessment by Lange (2004). Thapsia buraensis is classified as endangered in the IUCN RED list (2010). It is endemic to Taita hills forest. The last survey showed a decrease in population (Lange 2004). Gulella taitensis is classified as endangered and is endemic to Taita hills forest.

The project has the following objectives .The project did a survey to determine population trend for Gulella taitensis. We compared the number of live snails collected in 2004, 2008 and 2012.  The data obtained was used to re-asses current Red list status for Gulella taitensis and revealed that species is still endangered. The study established that high numbers of these snails could be found under a log, moss or in a spot where there is wet decaying leaves. Thus this could give wrong information especially on survival of these snails. At the same time we found that some other land snail species that were feeding on G. taitensis. At this point we can not establish the extent and effect of this 'cannibalism' phenomenon.

  The second objective was to determine the current population and spatial distribution of Zingis radiolata and Thapsia buraensis. This objective was not achieved since we did not record a single live snail neither a dead shell for these two species. Thus more survey need to be carried out to establish whether there is any live snail of these two species that is surviving or both have become extinct. We are trying to raise more funds to have a continuous survey every year for three years for us to come up with a conclusive report.

The other objective of the project was to determine the habitat requirements for each of the species. For Thapsia buraensis and Zingis radiolata we did not establish their habitat requirements since no snail was recorded in this study. For Gulella taitensis it was established that the most preferred micro-habitat is dead decaying logs, under moss, in rocks and under wet decaying leaves’ litter. This was reflected by high numbers recorded in the unprotected fragments as these were mostly under the logs regardless of whether the forest quality was low or high in terms of canopy cover, litter depth tree density and total calcium content present in the forest soil.

The fourth objective of the project was to establish whether hybridization occurs in any of the three species. This work is continuing for Gulella taitensis but we lacked samples for Thapsia buraensis and Zingis radiolata thus their genetic work is on hold. The genetic diversity among and within Gulella taitensis populations will be assessed, using DNA sequences from a variable mitochondrial gene loci and a variable nuclear gene locus. The analysis of the sequences generated from these samples will be used to determine the current genetic structure of the species. Due to the continuous decrease in the size of the remnant forest fragments, molecular studies are vital in establishing the genetic structure of these species. Both their population trend data and their molecular data can be useful in determining their conservation requirements. This information will be vital in making decision that is essential to the management of the forest and long term survival of these snails.