Global patterns of biodiversity and phylogeny of the Echinodermata
Matthys, S. (2022). Global patterns of biodiversity and phylogeny of the Echinodermata. MSc Thesis. Universiteit Gent/Vrije Universiteit Brussel/Universiteit Antwerpen: Gent, Brussel, Antwerpen. 41 pp.
This paper deals with different aspects of the Echinodermata, which have not been extensively studied in the past. It deals with their species diversity over depth through the analysis of a barplot representing the number of taxa over depth. The species diversity over depth pattern is analyzed in order to determine if it corresponds with the unimodal pattern that has been observed in the past. The paper considers the phylogenetic community structure in terms of countries, oceans and depth ranges in which the echinoderms occur. The last aspect of the analysis is the phylogenetic tree that has been constructed of the echinoderms. The aimis to determine if it corresponds to previous phylogenetic relationships, namely the Asterozoan or the Cryptosyringid hypothesis. In order to provide the results, all the available sequences of the Echinodermata havebeen uploaded from The Barcode of Life Database and analysed in RStudio for the construction of the barplots and the calculation of the Mean Pairwise Distance, Mean Nearest Taxon Distance and Pairwise Distance. The phylogenetic tree was constructed through FastTree and Mega11. The species diversity over depth which was visualized through the barplots did notshow a clear unimodal pattern. This could be due to the fact that not all the species were associated with their corresponding depth and it seems that there are almost no echinoderms to be found in the hadal zone, which seems quite surprising. In terms of phylogenetic community structure, the main phylogenetic community structure characterizing the Echinodermata seems to be the clustering phylogenetic community structure. This is plausible due to the fact that the echinoderms adapt to the changing environmental conditions, but this still needs to be confirmed through further investigations. Finally, the phylogenetic tree, which contained a high number of branches and made the determination of a relationship complicated, tends to go towards the Asterozoan hypothesis, which is the hypothesis that seems to be the most probable according to the scientists.To conclude, the species diversity analyses had to contain more species that are associated with their corresponding depth in order to get a clear representation of the species diversity as it seems quite unlikely that echinoderms are absent at greater depths. For the phylogenetic community structure, comparison could not be made with previous researches asit has not been done in the past, but the clustering phylogenetic community structure seems to be a possibility in terms of phylogenetic community structure. For the phylogenetic tree, it tends to go towards the same conclusion as previous researches. Overall the research corresponds to previous results, but more data have to be incorporated for the species diversity over depth and the investigation of phylogenetic community structure could be interesting to be made for future researches.
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