Universität zu Köln

Ngo Ngoc, Hai ORCID: 0000-0001-5471-965X (2022). High level of local endemism under high risk of extinction: Systematics, evolution, autecology, population and conservation status of Tiger geckos (Goniurosaurus) in Vietnam. PhD thesis, Universität zu Köln.

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Abstract

Tiger geckos of the genus Goniurosaurus currently consist of 24 species in Southeast and East Asia, all of which have been found in allopatry with a high level of local endemism. Five species are currently known from Vietnam, viz. G. araneus, G. catbaensis, G. huuliensis, G. lichtenfelderi and G. luii. Although new species of Goniurosaurus are still being discovered, the genus has become threatened by extinction through anthropogenic impacts. Unfortunately, once the thesis started, none of Goniurosaurus species were yet included in any wildlife protection laws, neither in China nor in Vietnam. In spite of the urgent requirement for protection, Goniurosaurus species have been omitted from the prioritization of conservation schemes due to a lack of biological background. In this study, I employed integrative methods of morphology, genetics, ecology, demography, and species distribution models in order to provide insights into the systematics, evolution, autecology, population status and threats of tiger geckos in Vietnam for conservation implications. Based on data collected during recent field work by our team, we expanded morphological descriptions of Vietnamese tiger geckos, evaluated variations among all Goniurosaurus species and provided an identification key. Our phylogenetic analyses showed that all recorded populations of Goniurosaurus from Vietnam are monophyletic with low intraspecific divergences (0 – 1.9 %), which are assigned to one of the four known species, namely G. catbaensis, G. huuliensis, G. lichtenfelderi and G. luii. Together with genetic data of remaining species from China and Japan, we evaluated the phylogeny of 23 species of Goniurosaurus. The analysis strongly supported the recognition of four monophyletic species groups (namely G. kuroiwae, G. lichtenfelderi, G. luii and G. yingdeensis). We further calibrated the divergence date of generic origin in the Eocene (approximately ~45.3 mya), and the diversification within four monophyletic groups began in the mid-Miocene ~13.4 – 7.7 mya and continued to at least the mid-Pliocene ~2 mya among species. The cladogenetic events of Goniurosaurus were ergo assumed relative to past orogeny processes following the vicariance pattern, adapted habitat segregation (e.g. karst and granite) and altitudinal transition. Given the Grinnellian niche evolution, the speciation among Goniurosaurus species was further explained with both climatic niche conservatism and divergence patterns. We studied the habitat preference of four Vietnamese tiger gecko species. The ecological analyses confirmed that three Goniurosaurus species (G. catbaensis, G. huuliensis and G. luii) are limestone karst-dwelling specialists, while the habitat preference of G. lichtenfelderi is significantly different, viz. adapted to granite-stream forest. Being aware of the importance of demographical information for species conservation efforts, population monitoring was carried out to estimate the population size and density of two Vietnamese Goniurosaurus species (namely, G. catbaensis and G. huuliensis). Consequently, their population size and density were found to be exceedingly small and negatively correlated to the increasing severity of human impacts. 3In this study, an extensive attempt was implemented to outline domestic and international trade activities in Goniurosaurus species. As a result, a large number of wild Goniurosaurus individuals from Vietnam and China have been over-harvested for international trade, although our records only reflected snapshots. Given potential impacts of climate change, we applied species distribution models (SDMs) to project the potential distribution of three Vietnamese Goniurosaurus species (namely, G. catbaensis, G. huuliensis and G. lichtenfelderi). Under climate change scenarios, their suitable habitats were predicted to shift towards higher latitudes, shrink significantly and even vanish in their entire distribution within the next decades. Furthermore, the increasing rate of habitat degradation and forest conversions dramatically imperils wild populations of Goniurosaurus species in Vietnam. Under severe human impacts, all species of Goniurosaurus from China and Vietnam were listed in CITES Appendix II, and Vietnamese species were assessed as globally threatened in the IUCN Red List and were protected by national laws as well. In this context, we identified priority areas – especially in protected areas, islands and transboundary regions – for conservation actions, and highly recommended the establishment of species and habitat conservation areas for tiger geckos in Vietnam. In conclusion, this study clarified issues related to the systematics and proved evolutionary hypotheses of geographical origin and relevant abiotic factors for the diversification of Goniurosaurus species and their allopatric distribution. Together with assessments of ecology, demography and anthropogenic threats, the thesis emphasized the urgent requirement of conservation actions. In this context, conservation programs and solutions were proposed to protect Goniurosaurus species in Vietnam and their habitats in the future.

Item Type:	Thesis (PhD thesis)
Creators:	Creators Email ORCID ORCID Put Code Ngo Ngoc, Hai ngohai2709@gmail.com orcid.org/0000-0001-5471-965X UNSPECIFIED
URN:	urn:nbn:de:hbz:38-641284
Date:	2022
Language:	English
Faculty:	Faculty of Mathematics and Natural Sciences
Divisions:	Faculty of Mathematics and Natural Sciences > Department of Biology > Zoologisches Institut
Subjects:	Natural sciences and mathematics
Uncontrolled Keywords:	Keywords Language Tiger Gecko English Evolution English Conservation English Ecology UNSPECIFIED Population UNSPECIFIED Vietnam UNSPECIFIED
Date of oral exam:	31 October 2022
Referee:	Name Academic Title Ziegler, Thomas Prof. Dr.
Refereed:	Yes
URI:	http://kups.ub.uni-koeln.de/id/eprint/64128