Universität zu Köln

Ngo, Thi Hanh ORCID: 0000-0002-5283-6243 (2025). Systematics, evolutionary distinctiveness, and conservation priority of the speciose lizard genus Cyrtodactylus in Vietnam. PhD thesis, Universität zu Köln.

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Abstract

Cyrtodactylus is the most diverse genus in the family Gekkonidae and ranks as the third-largest vertebrate genus in the world. In the past two decades, the number of new species has increased more than fourfold, particularly with a significant surge in new discoveries in Vietnam. However, as new species in this genus are described at a rapid rate, several taxa have been synonymized as a result of additional data. For example, C. paradoxus and C. thochuensis have been shown to be junior synonyms of C. condorensis and C. leegrismeri, respectively. This highlights the pressing need to review the taxonomic progress. Moreover, many areas in Vietnam where this group likely occurs are still poorly studied, emphasizing the necessity for additional field surveys to better understand the diversity of Cyrtodactylus in these regions. Furthermore, although some phylogenetic relationships and biogeographic studies have been conducted, phylogenetic analyses have yet included all members of the genus in Vietnam. Previous studies have primarily focused on just one or two mitochondrial genes (COI and/or ND2). Additionally, since the beginning of the dissertation, only one study has been carried out that provides information on the population status and main anthropogenic threats to one threatened species, and none of the Cyrtodactylus species, especially the most threatened taxa, have been investigated for their microhabitat preferences. Therefore, we conducted this study to (1) investigate the taxonomic status of described Cyrtodactylus species in Vietnam and discover new taxa (2) recover phylogenetic relationships, evolutionary processes, and biogeographic history of Cyrtodactylus and (3) assess ecological traits and population status of two endemic and critically endangered species. The results of the dissertation show that C. thuongae and C. rufford are junior synonyms of C. dati and C. lomyenensis, respectively. During four years of this study, seven new species have also been described and at least ten new lineages have been discovered. Our study reveals that the C. angularis and C. chauquangensis are monophyletic groups and several lineages within these groups diverged during the Miocene era when the East Asia monsoon was developed and increased precipitation in the region. Biogeographic analysis suggests that the Mekong Lowlands is likely the ancestral area of the C. angularis group while C. chauquangensis might have originated from the Northwest Uplands (including northern Laos and part of northern Vietnam). Our ecological analyses confirm that C. takouensis is a granite specialist. In contrast, C. gialaiensis likely has a broader distribution across the Gia Lai District rather than restricted to a single locality. It has had to adapt to various habitats, including soil cliffs, tree trunks, and shrubs found between coffee plantations and roads, as well as within coffee plantation areas. Recognizing the significance of demographic information for species conservation, population monitoring studies were conducted to estimate the population size of two Vietnamese Cyrtodactylus species, namely, C. takouensis and C. gialaiensis. According to the study results, their population size and density are extremely small and negatively correlated with the increasing severity of human impacts. The diet of C. nigriocularis was also for the first time investigated in this study to support ex situ conservation measures. To provide a reference for future studies, we also assess the suitability of genetic markers for molecular systematics and species identification of Cyrtodactylus based on twelve complete mitochondrial genomes of ten Cyrtodactylus species. Overall, phylogenies inferred from ND5 most frequently recovered a topology similar to those based on the 13 protein coding genes. In conclusion, this study helps clarify issues related to the systematics and species diversity, and provide robust phylogenetic relationships, evolutionary hypotheses, and successfully reconstruct biogeographic history for two Cyrtodactylus groups, namely the C. angularis and C. chauquangensis groups. Together with assessments of ecology, demography and anthropogenic threats, the dissertation highlights the urgent need of conservation actions for at least two threatened species, C. gialaiensis and C. takouensis.

Item Type:	Thesis (PhD thesis)
Creators:	Creators Email ORCID ORCID Put Code Ngo, Thi Hanh ngohanhhus@gmail.com orcid.org/0000-0002-5283-6243 UNSPECIFIED
URN:	urn:nbn:de:hbz:38-789693
Date:	2025
Place of Publication:	Cologne, Germany
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 Cyrtodactylus UNSPECIFIED Vietnam UNSPECIFIED
Date of oral exam:	24 September 2025
Referee:	Name Academic Title Ziegler, Thomas Prof. Dr.
Refereed:	Yes
URI:	http://kups.ub.uni-koeln.de/id/eprint/78969