Assessment of Historical and Current Distribution Records of the Indo-Pacific Slender Gecko , Hemiphyllodactylus typus Bleeker , 1860 , in Sri Lanka

Hemiphyllodactylus typus is a widespread but low abundant parthenogenetic taxon, which is widely distributed through Southeast Asia and the entire tropical Pacific Ocean of New Guinea to some other Oceanic Islands. The present study has reviewed the data from a combination of literature together with our unpublished field records. A total of 36 localities of H. typus were detected, including four recent observations or repeated observations. Some information regarding the natural history, autecology and biogeography of H. typus in Sri Lanka are given.


INTRODUCTION
Hemiphyllodactylus typus is a widespread, unisexual (parthenogenetic) species and thus the populations comprise only of females with developed precloacal and femoral pores.This species is distributed through Southeast Asia and the entire tropical Pacific Ocean west of New Guinea to the Sunda Islands and eastward towards the islands and atolls of eastern Polynesia reaching Pitcairn Island.The species has probably been introduced into the Philippines, Taiwan, Andaman and Nicobar (India) and Mascarene Islands, Ryukyu and Iriomotejima Islands (Japan), New Caledonia (questionable) and Hawaiian Islands in the USA (Das, 1999;Lever, 2003;Zug, 2010;Chandramouli et al., 2012;Fisher et al., 2013;Holden et al., 2014).Its apparent scarcity is certainly related to its small size, strictly nocturnal mode of life, and secretive behaviour (Zug, 2010).Batuwita & Alagiyawadu (2004) presented that individuals from coastal zones are more or less slender bodied while those from the central hills are robust.However, populations of Hemiphyllodactylus from Sri Lanka are also possibly formed by bisexual populations, which is not examined so far (see Somaweera & Somaweera, 2009;Zug, 2010).H. typus is considered as an endangered species in Sri Lanka, The Red-List criterion has amended in 2012 under the "Nationally Vulnerable" B1 ab (ii) (MENR, 2012).

MATERIAL AND METHODS
This article provides a combination of information from published literature together with our unpublished field records.This is necessary in view of insularity of the study region, exceptionally high species diversity of reptiles, probable presence of both unisexual and bisexual populations of Hemiphyllodactylus and the possibility of its introductions through accidental human transport.
All records were georeferenced.However, coordinates of some historical records correspond to the closest village/regions nearby and do not represent the exact sites of the recorded finding.Based on obtained coordinates (see Table 1) we generated a distribution map for H. typus in Sri Lanka using DIVA-GIS 7.5 (Hijmans et al., 2012).The records were divided into two categories, already published and our new records.Field observations of H. typus were encountered during three regular field visits and one random spot between 2004 and 2015 (Table 1).Visual spotting on habitats with occasional hand capture was done during the diurnal and Ceylon Journal of Science 45(3) 2016: 77-84 DOI: http://doi.org/10.4038/cjs.v45i3.7403RESEARCH ARTICLE nocturnal observations.Some measurements were taken with a digital vernier scale (Mannesmann Electronic Precision/0-150 mm).Specimens were identified following Smith (1935), Deraniyagala (1953), Somaweera & Somaweera (2009) and Zug (2010).No voucher specimens were collected.

RESULTS
A total of 36 localities of H. typus were detected including four recent observations (see Table 1 and Figure 1).All observation sites were from wet and intermediate zones of the island and the locations were confined to lowland, sub-montane or montane and moist monsoon forests (see Table 1; cf.Somaweera & Somaweera, 2009).Habitats of recent sightings are described below.All observed specimens were females.
During November 2004 to December 2009, a total of 15 observations were made in this site.These observed specimens were three new born, three juveniles and nine adults or subadults (31-41 mm SVL).

Godahena, Ambalangoda (location 19)
This site is located on the eastern boundary of Madampa Lake along the southwestern coastline of Sri Lanka, next to southern boundary of the RAMSAR wetland "Maduganga" Lagoon, Galle District.(see also Boulenger, 1890).Subsequently Stejneger (1899) corrected the genus name as a H. ceylonensis and stated nomenclature as H. ceylonensis (see Werner, 1913;Zug, 2010).Later Smith (1935) listed it as a subspecies H. typus.Populations from Sri Lanka are currently designated as H. typus because the morphology of the holotype (BMNH 74.4.29.1326) was confirmed to be of this species.The situation in Sri Lanka is, however, more complicated due to historical evidence of unisexual and bisexual specimens and different morphology between populations (see below and Batuwita & Alagiyawadu, 2004;Zug, 2010).
Hemiphyllodactylus typus is uncommon or scattered in many countries where it is been recorded (Zug, 2010;Grismer, 2011;Fisher et al., 2013).Based on present observations and available literature, the recorded sympatric geckoes were listed in Table 2 Hemiphyllodactylus typus recorded in number of different types of habitats in Sri Lanka (mangrove, plantations, primary and secondary forests, and anthropogenic habitats).Some of these records come from an elevation of above 1,000 m (Table 1).Observed pattern suggests that fragmented populations on the island.Most of observed sites were located in the southwestern part of the island, especially in coastal regions and central hills.
The current considered pattern of H. typus distribution, can be separated into two subpopulations, one is covers south-west lowlands with coastal plains and the other is central hills above the 1000 m.The theoretical explanation for this two separated populations will be explored further.
However, (i) the slightly disjunctive pattern of distribution of this species in Sri Lanka (Figure 1), (ii) historical records of existence of both unisexual and bisexual populations (Zug, 2010) and (iii) morphological differentiation between lowland and central hills populations (Batuwita & Alagiyawadu, 2004;Zug, 2010), we can suggest that populations of Hemiphyllodactylus on the island can be formed by two species; unisexual H. typus morph type and bisexual, presumably classified as H. aurantiacus morph type distributed also in southern and eastern India (Maqsood-Javed et al., 2010;Zug, 2010).On the other hand, we cannot exclude the fact that the latter is a new undescribed species (Zug, 2010).
The status of this genus in Sri Lanka can be confirmed through a widespread sampling and molecular/chromosomal evaluation.At present, the taxonomic status of the Sri Lankan bisexual population is indecipherable owing to paucity of data.Both morphotypes (presumably equal to H. typus and H. aurantiacus) are members of very diverse typus genetic group (mitochondrial ND2 marker; Grismer et al., 2013) and according to this phylogenetic hypothesis both fall into different clades of this group.In accordance with this hypothesis and with current distribution of the species (and colonization ability of H. typus) we can speculatively discuss that the origin of the one (bisexual) morphotype is natural (H.aurantiacus) while the second (unisexual) is the result of human-mediated introduction on the island (most of the current records come from the vicinity of main ports of the island, i.e.Colombo and Galle; Figure 1).
In general, very little information is known about the origin of parthenogenetic species in Sri Lanka (see Jayaneththi et al., 2015 for Lepidodactylus lugubris), and molecular investigation could uncover the answer.Geckoes are one of the top ten most successful introduced animal group in the world (Bomford et al., 2005) and parthenogenetic unisexual species are a wellknown example for that (see Zug, 2010;Daza et al., 2012).Considering the very dense maritime transportation in Sri Lanka (Indian Ocean) since the colonial period in the last 200 years, it is possible that H. typus naturalised in Sri Lanka after the colonial era.This hypothesis supports the occurrence of this species in Mascarene, Andaman and Nicobar Islands of the Indian Ocean where it is also a non-native (see Bour & Moutou, 1982;Das, 1999;Lever, 2003;Chandramouli, et al., 2012).A similar phenomenon is supposed for L. lugubris in Sri Lanka (Jayaneththi et al., 2015).We are focusing further studies in par with Zug"s (2010) original hypothesis, which states that the entire distribution of H. typus instigates from humanmediated transport (ships), possibly during the last two centuries.Further studies on these species will continue to evaluate dispersal events of H. typus and L. lugubris in Sri Lanka.

Figure 1 :
Figure 1: Updated distribution map of Hemiphyllodactylus typus in Sri Lanka based on published (blue spots) and new records in the present study (orange stars).SeeTable 1 for other details.

Table 1 .
Table 1 for other details.Distribution sites and descriptions of published records including new localities of Hemiphyllodactylus typus in Sri Lanka.