Population Genetic Structure and Revised Geographic Range for the Tridactyl Skink ( Brachymeles muntingkamay ) from Luzon Island , Philippines

The genus Brachymeles represents a unique radiation of semi-fossorial (burrowing) lizards, all but two of which are endemic to the Philippines in Southeast Asia (Siler et al. 2011a, 2012b). Although all species can be described as slender, brown, and smallto medium-sized, this radiation represents one of the best systems for studying the evolution of limb reduction and loss; body forms within the genus range from pentadactyl to externally limbless (Siler and Brown 2011). Over the last decade, a renewed effort at understanding evolutionary patterns within Brachymeles has resulted in the discovery of 21 new species previously unknown to science or masquerading within the range of a previously recognized, widespread, and morphologically diverse species (Siler 2010; Siler and Brown 2010, 2011; Siler et al. 2009, 2010a,b, 2011a,b,c,d, 2012a,b). Although the dense survey efforts leading to these discoveries have filled in many gaps in our understanding of this radiation, there still remain species with unique body plans that are poorly represented in collections and are far less understood (Siler 2010; Siler et al. 2011c,d, 2012a). Many of the species representing unique digit classes within the genus are micro-endemics, with recognized ranges currently limited to single sites. Among these taxa, several low-elevation species have persisted despite nearly complete deforestation across their limited ranges on Mindanao and Cebu islands (B. cebuensis, B. pathfinderi); until rediscovered in 2009, B. pathfinderi had not been observed for more than 80 years (Siler et al. 2011c). Other taxa include several mid-to-high elevation species (B. elerae, B. muntingkamay, B. wrighti), with B. elerae and B. wrighti long represented in museum collections by only a few specimens (Siler et al. 2011d). All three of these species occur in the mountainous terrain of northern Luzon Island in the Philippines. Interestingly, all micro-endemic taxa are non-pentadactyl, with finger counts ranging from 3–5 and toe counts ranging from 2–4. Brachymeles muntingkamay Siler, Rico, Duya, and Brown, 2009 is one of 36 recognized lizard species of Brachymeles, and is one of only four species known to possess three digits on the foreand hind limbs. This unique species was discovered only recently in midto high-elevation forest on Mt. Palali in the northern portions of Luzon Island, and has since been presumed to be endemic to this single, isolated mountain peak in the Caraballo Mountain Range of central Luzon. During a recent survey around the caldera of Mt. Cagua in the extreme northeastern portion of Luzon Island, a second montane population of this species was discovered. From 7–23 July 2011, seven adults and one juvenile of Brachymeles muntingkamay were collected during herpetological field surveys in midto high-elevation forest on Mt. Cagua, in extreme northeast Luzon Island, Philippines (Fig. 1). Here we report on this newly discovered population of B. muntingkamay from Mt. Cagua, located in the northern extreme of the Sierra Madre Mountain Range. The new population is not only geographically disjunct from the type locality of B. muntingkamay, but is located in a completely disparate mountain range on the island. With this new discovery, we present data on the genetic identity and structure between the two geographically disjunct populations, provide new photographic and morphological data for the species, revise the known geographic range of B. muntingkamay, and discuss the implications of this discovery for future research involving other unique (and possibly rare) midto high-elevation vertebrate species in the Philippines. Materials and Methods. —Field survey protocols follow Brown et al. (1996, 2000), Diesmos et al. (2005), Siler et al. (2011e), and McLeod et al. (2011). Vouchered specimens collected in the field were deposited in the University of Kansas Natural History Museum (KU) herpetological collections and the National Museum of the Philippines (PNM). We examined fluid-preserved specimens for variation in qualitative and mensural characters. Sex was determined by gonadal inspection, and measurements were taken to the nearest 0.1 mm with digital calipers by CDS. X-rays were taken with a company cabinet X-ray on Kodak MIN-R 2000 film exposed at 5 milliamperes and 30 volts for 1 minute 15 seconds. Meristic and mensural characters were chosen based on Siler et al. (2009): snout–vent length, total length, tail length, paravertebral scale-row count, supralabial count, infralabial count, supraciliary count, and supraocular count. Additionally, we counted the number of presacral vertebrae from x-ray images of specimens. A summary of representative diagnostic characters highlighting the minor variation observed between mountain populations is provided in Table 1. Genetic samples of B. muntingkamay from the recently surveyed site in the Municipality of Gonzaga were used to investigate the northeastern population’s identity, as well as its genetic similarity with the type populations of topotypic B. muntingkamay from Mt. Palali, central Luzon (Fig. 1). The dataset included newly collected sequences of the mitochondrial gene NADH dehydrogenase subunit 2 (ND2), supplemented by published ND2 sequence data from B. elerae and B. boulengeri for use as outgroup samples (Siler et al. 2011a). We follow the methods described in Siler et al. (2012c) for calculating haplotype networks. All Mt. Cagua specimens were initially identified on the basis of body and head scalation patterns (Siler et al. 2009). The newly collected B. muntingkamay specimens include: KU 330086, 330087, 330089–93, seven adult females; KU 330088, CAMERON D. SILER* Department of Biology, University of South Dakota, Vermillion, South Dakota 57069, USA LUKE J. WELTON Department of Biology, Brigham Young University, Provo, Utah 84602, USA ASHLEY A. ROCK Biodiversity Institute and Department of Ecology and Evolutionary Biology, University of Kansas, Lawrence, Kansas 66045, USA RAFE M. BROWN Biodiversity Institute and Department of Ecology and Evolutionary Biology, University of Kansas, Lawrence, Kansas 66045, USA