Nueva filogenia molecular de Crocodylia en el 22nd European Congress of Herpetology

Durante el 22nd European Congress of Herpetology (22SEH), celebrado del 4-8 septiembre en Wolverhampton (UK), Ane de Celis ha presentado una nueva filogenia molecular de Crocodylia. En esta nueva filogenia molecular se incluyen todas las especies actuales de cocodrilos y se han utilizado secuencias de ADN mitocondrial y nuclear, las cuales se han analizado una por una para verificar su utilidad a la hora de reconstruir las relaciones filogenéticas en Crocodylia. Los resultados muestran que todas las secuencias de genes mitocondriales fueron útiles para reconstruir las relaciones filogenéticas del grupo, pero no así con todas las secuencias nucleotídicas nucleares. El árbol filogenético resultante combinando todas las secuencias que demostraron tener utilidad filogenética muestra gran robustez y es uno de los más completos hasta el momento. El resumen del trabajo a continuación:

Advances in genetic sequencing and phylogenetic analysis techniques have deepened our understanding of crocodylian phylogenetic relationships. Most studies have focused on increasing the number of sequences included in these phylogenetic studies, and also on addressing the incongruence between molecular and morphological data in phylogenetic studies (e.g., the ongoing discussion on the phylogenetic relationships of Tomistoma). However, not all sequences contain valuable information to reconstruct the evolutionary history of organisms, and since techniques such as Bayesian Inference (BI) require extensive computational resources, it is desirable to assess the phylogenetic utility of these sequences prior to analysis to optimise processing time and obtain robust phylogenetic trees. Mitochondrial and nuclear nucleotide sequences from 23 crocodylian species were retrieved to analyse their phylogenetic utility. These sequences comprise approximately 26000 base pairs from 33 nuclear and mitochondrial genes available on NCBI GenBank, making this study one of the most comprehensive and extensive analyses of molecular sequences from all crocodylian species currently available. Each sequence was aligned, evaluated for substitution saturation (protein-coding sequences), and the best nucleotide substitution model was selected for each sequence. Bayesian Inference (BI, 10 million generations) and Maximum Likelihood (ML, 1000 replicates) were performed on each sequence, and the phylogenetic resolution was assessed by examining the resulting trees. Sequences that produced phylogenetic trees with significant polytomies were excluded from subsequent analyses. Most of the excluded sequences were partial nuclear sequences, as many failed to resolve crocodylian phylogenetic relationships, especially between crocodylids. The remaining sequences were concatenated (approximately 17500 bp) and subjected to BI and ML analyses (25 million generations and 1000 replicates, respectively). The resulting majority rule tree shows well-resolved and supported phylogenetic relationships among crocodylians, consistent with previous studies and optimising computational resources by eliminating sequences of low phylogenetic utility.

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Más información:

• Referencia: de Celis, A., Narváez, I., Ortega, F. 2023. Optimising the molecular phylogeny of Crocodylia. In: Malhotra, A., Harrison, X., Jehle, R., Ruthsatz, K., Ting, K.S., Garner, T., Herrel, A., Gower, D.J., Crnobrnja-Isailović, J., Corti, C., Naumov, B., Torres-Sánchez, M., Jablonski, D., Orton, F., Vamberger, M., Jelić, D., Ihlow, F., Gvoždík, V., O'Shea, M., Maddock, S., Kruger, N., Wilkinson, J., Pawlik, A., Morris, R., Martin, R., Deepak, V. (Eds.). Book of abstracts of the 22nd European Congress of Herpetology, University of Wolverhampton, UK, 4th-8th September 2023.