Contributions to Zoology, 86 (4) – 2017Samuel G. Penny; Angelica Crottini; Franco Andreone; Adriana Bellati; Lovasoa M.S. Rakotozafy; Marc W. Holderied; Christoph Schwitzer; Gonçalo M. Rosa: Combining old and new evidence to increase the known biodiversity value of the Sahamalaza Peninsula, Northwest Madagascar

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Endemicity patterns

Two new species of amphibians (B. ankarafensis and Stumpffia sp. aff. pygmaea Ca “Sahamalaza” (UCS)) identified in this survey and four species identified in prior surveys (Boophis tsilomaro, Cophyla berara, Rhombophryne sp. and Platypelis sp.) may represent local endemics as they have not been detected in other surveys of Northwest Madagascar (e.g. Nosy Be, Manongarivo, Tsaratanana, Benavony), in some cases, despite their prominent and distinctive calls (Vences et al., 2005b, 2010b; Glaw and Vences, 2007). The failure to detect neither Platypelis sp. nor Rhombophryne sp. during the most recent surveys mean that further effort should be invested in the area, as representatives of these genera are sometimes very difficult to detect. The population of Lygodactylus tolampyae from Sahamalaza was already known, however this population has a high genetic divergence with the other population of this species for which genetic data are available. A more in depth taxonomic revision of this genus is needed to apply this name to a specific taxon, until then it will not be possible to assess the taxonomic identification of the Lygodactylus tolampyae population from Sahamalaza. However, this might represent a new microendemic species of retile along with the previously identified and highly elusive skink Pseudoacontias menamainty. All this points towards the Sahamalaza peninsula being an important centre of microendemicity.

The new species of treefrog, Boophis ankarafensis, was described following the results of this survey (Penny et al., 2014). The species is only known from the banks of perennial streams in intact forest vegetation in Ankarafa Forest and has been classified as Critically Endangered on the IUCN Red List. The new candidate species, Stumpffia sp. aff. pygmaea Ca “Sahamalaza” (UCS), still awaits formal description but molecular data found only a 92-93% match (p-distance transformed into percent; at the analysed 16S fragment) with S. pygmaea and their taxonomic distinctness seems therefore to be granted. The species produces inconspicuous calls from within leaf-litter which are difficult to locate, thus the species may have been missed during surveys outside the peninsula. On the contary, this is such a small amphibian species that dispersal capacities might be very low. Our survey expands the range of Boophis tsilomaro beyond their type locality of Berara. The detection of B. tsilomaro from Anketsakely, a fragment of forest within Anabohazo, contributes only a marginal increase in range, and the species is confined to an area of less than 5 km2, qualifying it as Critically Endangered. The species’ absence from Ankarafa Forest, the only other significant area of forest on the peninsula, reinforces the importance of protecting all remaining areas of natural habitat in Sahamalaza, as populations may be reliant on particular conditions.

This survey expands the range of Cophyla berara beyond their type locality of Berara: a fragment of primary forest in Anabohazo (Vences et al., 2005b). We document the species throughout the fragments of Ankarafa Forest, the surroundings of Antafiabe village and the fragment of Anketsakely in Anabohazo Forest. These locations are no greater than 20 km distant from the type locality, yet mark an important extension to the distribution of this species and indicate multiple populations exist. Furthermore, C. berara were found in abundance in low quality secondary forest, a habitat common throughout the peninsula. Secondary tracts of regenerating forest are one of the most common forest types in Ankarafa and past land clearances have created a matrix of interlinked forest fragments surrounded by large thickets of bamboo. C. berara were extremely abundant in these forest edge habitats, and in interior sections where bamboo were present, a habit also reported in C. maharipeo (Rakotoarison et al., 2015). This association is likely due to their breeding habitat of laying spawn inside water-filled segments of bamboo. The species was detected in all surveyed forest fragments, including isolated sections of heavily degraded forest that had experienced recent burning; callers were also found perched on scorched leaves and branches. Thus, this species seems to be adapted to disturbed forest, and is less likely to experience severe decline in the immediate future. However, its long-term viability in these small isolated forest fragments is unknown and even with these new range extensions, it is still known from just three areas within the Sahamalaza Peninsula, which itself totals around 26000 hectares. There appears to be limited gene flow between populations in Ankarafa and Anababohazo and molecular analyses show they have already slightly diverged, with two fix substitutions at the analysed mitochondrial 16S fragment (Penny et al., 2016). Although the species appears relatively well adapted to disturbed forest, it is still a forest-dependent species and at risk from future habitat destruction.