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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Range extensions

All species documented from Ankarafa Forest represent new records from this locality. Several species were recorded from Sahamalaza for the first time and represent important range extensions. For Boophis tsilomaro, Cophyla berara and Blaesodactylus ambonihazo we provide the first distribution record outside of their respective type localities. In the case of Boophis tsilomaro and Cophyla berara the range expension is still limited to the Sahamalaza Peninsula. Yet, it is worthnoting that in C. berara we observe a genetic distance of 1% between the two known populations of Berara and Ankarafa. The record of Blaesodactylus ambonihazo represents a significant increase in its distributional range (extended northward by over 200 km; Bauer et al., 2011; Ikeuchi and Mori, 2014). The recent formal description of this species (Bauer et al., 2011), along with those of B. victori Ineich et al., 2016 and B. microtuberculatus Jono et al., 2015, together with the confirmed sympatry of B. victori with B. sakalava (Grandidier, 1867), and of B. microtuberculatus with B. boivini Duméril, 1856 (Jono et al., 2015; Ineich et al., 2016), further highlights the importance of applying a taxonomically integrative approach, and the need to reassess previously known localities and providing new genetic data. The distribution of B. ambonihazo may extend to other dry forests fragments in north-western Madagascar, but due to the genera’s apparent requirements for areas of relatively low disturbance containing at least some large trees, its distribution is likely to be severely fragmented (Ineich et al., 2016).

The species Acrantophis madagascariensis and Crocodylus niloticus are reported from Sahamalaza for the first time. Unfortunately, Acrantophis madagascariensis was only recorded in the 2011-2012 expedition and no genetic data are available on this record. Only a single specimen of C. niloticus was sighted, of which the tail-end was seen slipping into the water of the Vavan’aneno River in Antafiabe; local people attested the presence of multiple specimens within the area but note that the largest individuals have been lost to hunting. The presence of the snake Ithycyphus perineti, gecko Ebenavia inunguis, chameleon Brookesia minima and treefrog Boophys brachychir within Sahamalaza extend their ranges over 100 km south along Madagascar’s west coast from Nosy Be (Glaw and Vences, 2007). The population of the Ebenavia inunguis sampled in Ankarafa belong to the Clade Cb (sensu Hawlitschek et al., 2017) as the popuation from Nosy Be, that is the type locality of this taxon. These two populations have a genetic distance of 4% at the analysed COI fragment, and thus far this represent the only other record for this taxon outside of Nosy Be. Brookesia minima was known at least from Nosy Be and Manongarivo and the population sampled in this study has a genetic distance of 5% with the population from Manongarivo. Similarily, B. brachychir was already reported for Nosy Be, Manongarivo, Forêt d’Ambre and near Antsiranana. This record thus represent the southern most new distribution.

The presence of Heterixalus tricolor confirms the species’ distribution between Nosy Be and Ankarafantsika (Glaw and Vences, 2007). The presence of the turtle Pelomedusa subrufa extends their range over 200 km northeast of a record from Mahajanga (Iverson, 1992; Glaw and Vences, 2007; Petzold et al., 2014), placing this population at the northern edge of their projected distribution (Boycott and Bourquin, 2008), although no genetic distance was observed between the P. subrufa sequences of the newly reported population and the available sequences in Genbank.

We treated Phelsuma kochi as synonymous with P. madagascariensis, recorded by Andreone et al. (2001) following molecular identification; however, a photo from the earlier survey period resembles P. grandis Gray, 1870, known from the Sambirano region to the north, and it remains possible that the species occurs in sympatry with P. kochi. The occurance of P. kochi extends their range over 200 km northeast of Ankarafantsika (Mori et al., 2006; Glaw et al., 2011) and the genetic distance between the population from Sahamalaza and Tsingy de Bemaraha is of 7% at the analysed COI fragment.

This survey documents the first record of Phelsuma laticauda from Sahamalaza, a species known from a number of locations across northern Madagascar (Gelach et al., 2011). The presence of Phelsuma vanheygeni increases their known range of about 50 km south beyond the Ampasindava peninsula, where the species was classified as Endangered due to their restricted range (Randrianantoandro et al., 2011). The presence of Phelsuma sp. aff. quadriocellata marks their only documented occurrence in north western Madagascar and a significant distance from the populations known from Eastern Madagascar (Glaw and Vences, 2007). Furthermore, individual’s from Sahamalaza occurred at heights of 150-170 m asl, significantly lower than the mid-elevation areas of 720-1350 m asl where the species is generally reported in the East (Glaw and Vences, 2011). The individuals encountered were found residing in Pandanus screw palms, a trait shared with Phelsuma quadriocellata (Peters 1883), however it is unknown whether they are truly conspecific as genetic data are not available. Their rare encounter rate from Sahamalaza may mean they have been missed by other surveys and indicate the species occurs between these distant sites; alternatively, they may belong to a different P. species. The species may be synonymous with Phelsuma cf. quadriocellata reported from Nosy Be (Andreone et al., 2003). The record of Madascincus stumpffi in Sahamalaza, similar with the record from Marojejy, mark the southernost distributional record for the species, but the population from Sahamalaza have a genetic distrace of 9% at the analysed COI fragment if compared with the population of M. stumpffi of Forest d’Ambre.

The presence of the frog Blommersia sp. Ca05 (UCS) marks a range increase of over 300 km beyond Tsingy de Bemaraha. Populations are also known from Isalo, Makay and Kirindy, while recent records of a Blommersia species from Mariarano and Mitsinjo near the Besiboka delta may also be attributed to B. sp. Ca05 (Rakotoarison et al., 2015), potentially indicating the species is widely distributed along the Madagascar’s west coast. Finally, we report a new record of the recently resurrected Geckolepis humbolti which, in Madagascar, was until now known only in the Tsingy de Bemaraha. The newly reported population of Geckolepis humbolti from Sahamalaza has a genetic distance of 8-9% with the populations from the Comoros and Mayotte.