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Universidade do Porto (2013)

Phylogeography of Androctonus scorpions from the Maghreb Region

Pedro Jorge Lobo Martins Coelho

Titre : Phylogeography of Androctonus scorpions from the Maghreb Region

Auteur : Pedro Jorge Lobo Martins Coelho

Université de soutenance : Universidade do Porto

Grade : Mestrado em Biodiversidade e Recursos Genéticos 2013

Résumé
Venomous animals, such as scorpions, have always evoked fascination to mankind. DNA sequence data has become the most used molecular data in estimating evolutionary history and scorpion researchers have started to use these tools to understand the phylogenetic history of this group that was previously difficult to ascertain. In this thesis, mtDNA markers were used to produce the first multi-gene (COI, 16S and 12S) phylogeny of Androctonus scorpions. A total of 110 new sequences from six species were used to investigate phylogeographical patterns in North Africa using Maximum Likelihood (ML) and Bayesian Inference (BI) methods. The study also produced the first sequence data for two species and the first sequences for specimens from three countries. In addition, the geographic sampling coverage of Androctonus was greatly enhanced with unreported locations, confirming former conjectures regarding their range. In the analysis of Androctonus, high levels of genetic diversity were found within 13 well-resolved clades that also presented geographical coherence. The bulk of the diversity in the Maghreb is found in Morocco, where this study shows a greater level of cryptic variation than was previously identified. The level of pairwise genetic distances between endemic clades within Morocco can be as high as the distance between clades occurring thousands of kilometers away in other parts of North Africa. In Tunisia this study corroborates a phylogeographical split in A. australis found in earlier studies, and shows the two separated clades extend well beyond Tunisia. Scorpion venom is known to vary regionally, even within single species. Androctonus are highly poisonous scorpions and studies identifying regional diversity, such as presented here, can have direct application in developing therapeutic measures. Additionally, a molecular phylogeny of the Scorpiones order was produced. 20 species of seven scorpion families were sequenced for three mitochondrial genes (12S, 16S and COI). This phylogeny was part of a study that focused on the scorpion’s pincers (pedipalps), particularly on the influence that different cuticular shapes have on the pinching performance. The phylogeny was used to account for the phylogenetic signal in the studied traits by a technique called Independent Contrasts. In that study, we further assessed the evolution of the performance of morphological variants, delimiting groups with similar shapes and testing their performance in silico under natural loading condition. Our work is valuable for identifying DNA markers that are informative in scorpion phylogenetic estimate both at the species and family levels. More importantly, these results will hopefully lead on to future integrative studies uniting distinct areas such as toxicology and functional morphology, propelling our knowledge of these animals.

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Page publiée le 17 mai 2020