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• W3040473311 abstract "BackgroundMadagascar is famous for its biodiversity and exceptional degree of endemism, especially in chameleons, hosting almost half of the world’s species. The exploration of its species diversity started with the famous Georges Cuvier who described the first Madagascan chameleons in 1829. Since then, the quality of species descriptions and, subsequently, the species concepts have substantially changed. While the first descriptions were based on a few characters of the external morphology only, today the collected specimens are usually DNA barcoded and their taxonomic status is evaluated based on genetic distances as a first step. In doing so, a previous molecular study of the nasutum group, which are small chameleons with a rostral appendage on the snout tip in most species, resulted in an impressive 33 deep mitochondrial lineages. Only seven of these corresponded to named species leaving 26 lineages as operational taxonomic units (OTUs). In times of DNA based taxonomy and species delimitation algorithms taxonomists face new challenges of how to describe a species and to avoid oversplitting.In this dissertation I evaluate, based on a taxonomic revision of nasutum group, the significance of mitochondrial lineages for species delimitation and promote micro-computed tomography (micro-CT) as an additional tool for integrative taxonomy. The second part deals with the discovery of the phenomenon of widespread fluorescence in chameleons. Biofluorescence is only rarely found in land vertebrates, so far, but has been reported for several marine organisms where it is used, inter alia, for intraspecific communication. As chameleons also communicate visually, the fluorescent pattern might work as an additional signal for species recognition.Methods and ProcedureTo describe (or redescribe) species of the nasutum group, I followed an integrative taxonomic approach incorporating five lines of evidence (for details, see below): External Morphology, micro-CT-scans of the skulls, dice-CT scans of the hemipenes, mitochondrial gene sequences (ND2), and nuclear gene sequences (CMOS).In the nasutum group a number of species have remained poorly characterized, because their original descriptions date to over a century ago and lack precise locality data, or because the holotype is a juvenile specimen. These species were redescribed here using a combination of micro-CT scans and detailed study of external morphology. With the help of diagnostic characters of the skull, the old type specimens were matched to recently collected and sequenced specimens. Additionally, micro-CT scanning was used for the first time to produce 3-dimensional models of chameleon hemipenes. In preparation for scanning, each hemipenis was removed from the specimen and immersed in iodine solution for several days to enhance the contrast when X-raying this soft tissue. This method is called dice-CT, and the resulting scans provide a more objective and detailed illustration of the hemipenes than the conventional 2-dimensional drawings. Further, sequences of mitochondrial (ND2) and nuclear (CMOS) genes were analysed for most of the new species described here. To provide comparability, access, and fast taxonomic progress, all new species were registered at ZooBank with an LSID number, their sequences were uploaded to GenBank, and all taxonomic acts were published in open access journals.To study fluorescence in chameleons, we used a fluorimeter to measure the excitation and emission spectra and to calculate the quantum yield for the intensity of fluorescence. The distribution of the fluorescent tubercles was recorded with photographs under UV light illumination, and the bony origins of fluorescence were studied using micro-CT and Transmission Electron microscopy of histological sections. ConclusionsThe taxonomic part or this dissertation resulted in the description of eight new chameleon species, Calumma emelinae, gehringi, juliae, lefona, C. ratnasariae, roaloko, C. tjiasmantoi, and uetzi (see chapter 3.1.2, 3.1.3, 3.1.4, 3.1.5), contributing nearly 4% of all known species of the family Chamaeleonidae. Furthermore, one species, radamanus (Mertens, 1933) was revalidated, five species, boettgeri (Boulenger, 1888), fallax (Mocquard, 1900), guibei (Hillenius, 1959), linotum (Muller, 1924), and nasutum (Dumeril & Bibron, 1836) were redescribed, and the females of vatosoa Andreone, Mattioli, Jesu & Randrianirina, 2001 were described for the first time.Using an integrative taxonomic approach, I showed that current species delimitation algorithms based on mitochondrial gene sequences alone greatly overestimate the actual number of species. Micro-CT proved essential for analysing skull morphology, which resulted more appropriate for species delimitation than some highly variable external characters. Further, this tool enabled to find frontoparietal fenestrae, which are cranial openings of potential adaptive importance found only in chameleon species living at high elevations. Using novel dice-CT imaging, I also analysed hemipenial morphology in minute detail and described a new ornament, the “cornucula gemina”.Finally, the phenomenon of fluorescence in chameleons was discovered in species belonging to eight of the twelve chameleon genera. The optimal excitation wavelength is in the UV-A spectrum at 353 nm, emitting light with wavelengths from 360 nm to 500 nm, with a maximum at 433 nm (blue spectrum). We showed that the fluorescent patterns result from bony tubercles on the skull are species specific, sexually dimorphic, and occur especially in forest living species. Based on these findings, and also because the colour blue is a conspicuous signal in forest habitats, I hypothesize that chameleons use fluorescence as a constant signal for intraspecific communication supplementing their vibrant body-colour language. Further, as-of-yet unpublished examples suggest that fluorescence is more common in squamates and might be an interesting field for further studies." @default.
• W3040473311 created "2020-07-10" @default.
• W3040473311 creator A5030388532 @default.
• W3040473311 date "2019-06-25" @default.
• W3040473311 modified "2023-09-23" @default.
• W3040473311 title "Systematics and signalling of Madagascan chameleons of the Calumma nasutum group" @default.
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