CHURA: Conserving Hyperendemic Udzungwa Restricted Amphibians

Posted by Elena Tonelli & Simon Valle

CHURA means frog in Swahili (Tanzania’s official language), and is also the acronym chosen for our project 'Conserving Hyperendemic Udzungwa Restricted Amphibians'.

The project focuses on the Udzungwa Scarp Forest Reserve (USFR; 200 km² ), a global biodiversity hotspot at the south-western end of the Eastern Arc Mountain (EAM) range, Tanzania. The great altitude range  (300–2068 m) and variety of vegetation types have contributed to an extraordinary number of strictly endemic species at the site. Four frog species (Kihansi spray toad Nectophrynoides asperginis, Poyntoni forest toad N. poyntoni, Wendy forest toad N. wendyae, and Kihanga reed frog Hyperolius kihangensis) are known only from specific sites on the scarp, and are regarded as ’hyper-endemics’. However, large portions of the forest remain unexplored and basic genetic and ecological data are lacking. 

The Kilombero Valley visible from the top of a waterfall around 1100 m (Photo E. Tonelli) 

Currently, we are refining amphibian inventories of the area, and examining species distribution, ecology and community dynamics throughout the USFR using ecological and molecular approaches. Given the occurrence of morphologically similar anuran species in the EAM range and that Eastern Arc herpetofauna shows distinctive changes in assemblages with small increases in altitude, genetic analysis is crucial to enable correct taxonomic classification, detection of potential sibling species and proper estimation of distributions. By adequately surveying the area and revising the conservation status of its amphibian species, my PhD project aims to support conservation management of this proposed Nature Reserve. 

Pitfall traps with drift fences 
(Photo E. Tonelli)

Three field seasons have been planned for the whole PhD project, each one lasting from November to March and coinciding with the short rains and the reproductive period, when amphibians’ detectability is higher. Field methods comprise pitfall traps with drift fences, night transects, day search with timed digging, opportunistic surveys, and audio recording. Since different species have different needs, all habitats are sampled, from closed canopy forest to open grasslands, from large rivers with waterfalls to shallow streams or ponds. The USFR is an exciting but demanding study area, with very steep, muddy paths connecting the Kilombero valley (about 200 m ) to the villages on the plateau at the top (about 2100 m). In many areas there are no paths at all, making movement slow.

In a previous study Menegon and Salvidio (2005), recorded 36 amphibian species in just five sites within USFR. We suspect this forest will surprise us again with some species still unknown to science and possibly a few more highly range-restricted amphibians.My team surveyed the historical sites of two hyper-endemics, with a rewarding outcome for the Kihanga reed frog H. kihangensis, which we found both in its historical site and in a new area over 7 km far from that previously known. This is potentially good news for the species, but it also suggests that some of the frogs we refer to as hyper-endemics are possibly more widespread in the scarp than first thought.

New sites have been discovered for the range restricted Kihanga reed frog (Photo E. Tonelli) 

This said, we weren’t as lucky with Poynton’s forest toad N. poyntoni, which we unsuccessfully tried to locate both in November and February. This is worrying since the species has not been recorded in its only known location in the past 10 years. We plan to survey the historical site again in the coming field season, hopefully with more encouraging results. Along with previously studied sites, three new sites at different altitudes were investigated. A total of 8 genera and 18 species were recorded, at least one of these species is new to science.

Callulina sp.,a new record for the USFR and possibly a new species (Photo E. Tonelli) 

 Table 1. Anuran species recorded along with altitudinal range.

    Recorded species                                                                             Altitude range m

    Afrixalus cf. uluguruensis                                                                     1650 - 1760

    Amietia angolensis                                                                                 1650 - 1740

    Arthroleptides yakusini                                                                          900 - 1200

    Arthroleptis affinis                                                                                  900 - 1760

    Arthroleptis reichei                                                                                 900 - 1760

    Arthroleptis stenodactylus                                                                    800 - 1760

   Arthroleptis xenodactyloides                                                                900 - 1760

   Callulina sp. (new record for USFR and possibly a new species)       1200

   Hyperolius kihangensis                                                                                1750

   Hyperolius minutissimus                                                                     1650 - 1740

   Hyperolius sp.                                                                                                1750

   Hyperolius substriatus                                                                          1750 - 1740

   L. cf. grandiceps                                                                                      1200  - 1760

   Leptopelis parkeri                                                                                         1650

   Leptopelis uluguruensis                                                                        900 - 1200

  Nectophrynoides sp. (new species)                                                          1650

  Nectophrynoides tornieri                                                                           1200

Molecular analysis on museum samples showed a remarkable genetic variety in the Scarp, especially within the genus Arthroleptis. We aim to disentangle the relationship between many cryptic sibling-species which occur in this forest using multiple genes.

Afrixalus cf. Uluguruensis (adult male, eggs and juvenile)

Next steps

In the two field seasons ahead I plan to survey 15 more sites, one of which will be the historical location of the hyper-endemic Wendy’s forest toad Nectoprhynoides wendyae at the south-western end of the reserve. Skin swabbing will be used to screen encountered individuals for Batrachochytrium dendrobatidis (Bd), a fungal pathogen which has been responsible for local amphibian extinction worldwide. 

John Lyakurva, a Tanzanian student from Dar es Salaam University will join the project next month. He will be trained in herpetological survey techniques to eventually lead one more team thereby covering a larger sampling area. Along with data on amphibians however, he will collect  data on reptile species occurrence and distribution in relation to altitude.

References

Menegon,  M.  and  Salvidio, S.  (2005)  Amphibians  and  reptiles  diversity  in  the  southern Udzungwa Scarp Forest Reserve, south-eastern Tanzania. In: Huber, B.A., B.J. Sinclair, K.-H.  Lampe  (eds).  African  biodiversity:  molecules,  organisms,  ecosystems.  Springer,  New York, pp 205–212.

Acknowledgements

Elena's work is done in collaboration with University of Basel and has been generously supported by