Koblmueller, S. | Search bioRxiv

bioRxiv2021

Somewhere I Belong: Phylogenetic Comparative Methods and Machine Learning to Investigate the Evolution of a Species-Rich Lineage of Parasites

AO_SCPLOWBSTRACTC_SCPLOWA substantial portion of biodiversity evolved through adaptive radiation. However, the effects of explosive speciation on species interactions remain poorly understood. Metazoan parasites infecting radiating host lineages could improve our knowledge because of their intimate host relationships. Yet limited molecular, phenotypic, and ecological data discourage multivariate analyses of evolutionary patterns and encourage the use of discrete characters. Here, we assemble new molecular, morphological, and host range data widely inferred from a species-rich lineage of parasites (Cichlidogyrus, Platyhelminthes: Monogenea) infecting cichlid fishes to address data scarcity. We infer a multi-marker (28S/18S rDNA, ITS1, COI mtDNA) phylogeny of 58/137 species and characterise major lineages through synapomorphies inferred from mapping morphological characters. We predict the phylogenetic position of species without DNA data through shared character states, a combined molecular-morphological phylogenetic analysis, and a classification analysis with support vector machines. Based on these predictions and a cluster analysis, we assess the systematic informativeness of continuous characters, search for continuous equivalents for discrete characters, and suggest new characters for morphological traits not analysed to date. We also model the attachment/reproductive organ and host range evolution using the data of 136/137 described species and multivariate phylogenetic comparative methods (PCMs). We show that discrete characters can mask phylogenetic signals but can be key for characterising species groups. Regarding the attachment organ morphology, a divergent evolutionary regime for at least one lineage was detected and a limited morphological variation indicates host and environmental parameters affecting its evolution. However, moderate success in predicting phylogenetic positions, and a low systematic informativeness and high multicollinearity of morphological characters call for a revaluation of characters included in species characterisations.

evolutionary biology↗

bioRxiv2020

Potassium Carbonate (K2CO3) - A cheap, non-toxic and high-density floating solution for microplastic isolation from beach sediments

Beaches are good indicators for microplastic distribution and local microplastic pollution. Multiple methods have been developed for extracting microplastics from sediment, mainly through density separation. However, the chemicals applied are often expensive and harmful for the user or to the environment. We briefly review the problems associated with the use of these chemicals and present a new floatation solution, potassium carbonate (K2CO3) that has many advantages over available media. It is non-toxic and cheap, and with a density of 1.54 g/cm3 the K2CO3 solution yielded a mean recovery rate of around 92% for PVC, one of the densest polymers, that cannot be easily extracted with alternative floatation agents. We propose that the use of K2CO3 is particularly promising for long term and large-scale monitoring studies, not least because it allows an increasing involvement of citizen scientists, hopefully leading to an increased public awareness of the plastic problem in the seas.

ecology↗