Critically endangered island endemic or peripheral population of a widespread species? Conservation genetics ofKikuchi's gecko and the global challenge of protecting peripheral oceanic island endemic vertebrates

Abstract

Aim To highlight the significant conservation challenge of evaluating peripheral endemic vertebrates in island archipelago systems and to assess empirically the complexities of approaches to conservation genetic studies across political and biogeographic boundaries. To demonstrate the poignant need for international collaboration and coordination when species delimitation problems with high conservation concern involve island endemics with biogeographically peripheral ranges.Location Southeast Asia, Lanyu Island, Taiwan, and the Philippines.Methods Genetic samples were collected and sequenced for one mitochondrial gene and five nuclear loci for species of the Gekko mindorensis-G. kikuchii species complex in Southeast Asia. We used maximum likelihood and Bayesian phylogenetic methods and coalescent-based species delimitation analyses to estimate phylogeographic relationships, construct multilocus haplotype networks and test putative species boundaries.Results Phylogenetic and population genetic analyses suggest that Kikuchi's Gecko may represent a peripheral population of a widespread species distributed from the northern Philippines to Taiwan. However, we identify a discrepancy between inferences of species boundaries resulting from methods based on allele frequencies versus coalescent-based methods that incorporate evolutionary history. Coalescent-based analyses suggest that G. kikuchii may be a distinct evolutionary lineage. Our study underscores the need for coalescent-based methods in conjunction with population genetic approaches for conservation genetic assessments of widespread species.Main conclusions This study joins a few recent works suggesting that Philippine-derived anomalies in the fauna of Lanyu (and possibly greater Taiwan) are worthy of careful reconsideration. Determining whether each is the result of recent human-mediated introduction or (possibly more ancient) natural dispersal should be the goal of future studies on this seldom-conceived biogeographic relationship. Isolated species endemic to islands on the outer periphery of biogeographic and political regions represent particular conservation challenges. This is especially true if a species occurs on an isolated island that is allied biogeographically with one nation, but politically administered by another.

The amphibians and reptiles of Mindanao Island, southern Philippines, II: the herpetofauna of northeast Mindanao and adjacent islands

“…A recent phylogeographic (Siler et al 2012c, 2014b) investigation identified eight genetically divergent and geographically structured clades within this Philippine endemic species, confirming previous speculation (Ferner et al 2001, Brown et al 2013) that many Philippine populations constitute a cryptic species complex. In a follow-up study, Siler et al (2014b) recognized Gekko kikuchii as a member of the Gekko mindorensis Complex, with a distribution that included populations from the islands of Luzon (northern Philippines) and Lanyu (Taiwan).…”

Complex inter‐island colonization and peripatric founder speciation promote diversification of flightless Pachyrhynchus weevils in the Taiwan–Luzon volcanic belt

“…Within the Taiwan-Luzon volcanic belt, long-distance dispersal by skipping the stepping-stone islands in between has been inferred for the Philippine bulbuls (Microscelis amaurotis) from Japan to the Babuyan and Batanes Islands (Oliveros & Moyle, 2010), and for Kikuchi's geckos (Gekko kikuchii) from Luzon to Orchid Island (Siler et al, 2014). However, the prevalence of long-distance dispersal in the Taiwan-Luzon volcanic belt shown herein and in earlier studies requires further examination by comparative analyses of colonization histories and community assemblies across taxonomic groups (Shaw & Gillespie, 2016).…”

“…The Kuroshio current is thought to be a strong oceanic mechanism in shaping the distribution of tropical sea grasses (Kuo, Kanamoto, Iizumi, Aioi, & Mukai, 2006) and population genetic structures of skinks in the Ryukyu Archipelago (Kurita & Hikida, 2014). However, the stepping-stone model of colonization in the Taiwan-Luzon volcanic belt has never been rigorously tested using a molecular phylogeographical approach, with the exception of some phylogenetic studies of shrews (Esselstyn & Oliveros, 2010), birds (Oliveros & Moyle, 2010) and geckos (Siler, Oaks, Cobb, Ota, & Brown, 2014), which indicated a direction of colonization from either Northern Taiwan (shrews) and Batanes (birds) or Southern Luzon (geckos). Nevertheless, these earlier studies were limited by representatives from only a few islands across the Taiwan-Luzon volcanic belt to fully address the direction and stepwise pattern of the stepping-stone hypothesis.…”

Additions to Philippine Slender Skinks of the Brachymeles bonitae Complex (Reptilia: Squamata: Scincidae) II: a new species from the northern Philippines

“…Although this process likely contributed to the development of distinct faunal regions within the Philippines, studies suggest that species diversification patterns in Brachymeles do not follow predicted PAIC-based diversification patterns, with evidence suggesting a number of overseas dispersal events may have also taken place during the radiation of this group throughout the archipelago (Siler et al 2011a). Furthermore, studies on radiations of other Philippine reptiles (Linkem et al 2010(Linkem et al , 2011Siler et al 2010cSiler et al , 2012bSiler et al , 2014Welton et al 2013Welton et al , 2014 have also partially or fully rejected PAIC formation and fragmentation events in the generation and maintenance of species diversity. These studies suggest that additional diversification mechanisms need to be explored to accurately assess and understand the processes that have resulted in the country's diversity of Brachymeles.…”