Department of Life Sciences Seminar
What a difference a decade makes – Recapping the last 10 years of bryozoan phylogenetics and future prospects
Parasites and Vectors, Dept.of Life Sciences, NHM
Wednesday 10 of April 11:00
Sir Neil Chalmers seminar room, Darwin Centre LG16 (below Attenborough studio)
Since the first bryozoan molecular phylogenetic study just over decade ago, the field has come a long way, battling the enemies of sequence contamination, long-branch attraction, and misidentification. In this talk I will recount how some of these obstacles have been overcome, recap key results that were gathered along the way, and outline some future research lines of molecular bryozoology in the era of next-generation sequencing (NGS). Bryozoan colonies provide microhabitats for many other organisms including bacteria, fungi, diatoms, ciliates, nematodes, copepods, ostracods, sponges, molluscs, entoprocts and turbellarian flatworms, providing ample opportunities for co-extraction and co-amplification during PCR, resulting in frequently contaminated datasets. This has been having important implications for bryozoan interrelationships and metazoan-wide phylogenetic inferences, which will be discussed. The comparatively fast rate of molecular evolution of bryozoans often results in them forming clades with other long-branching taxa, such as chaetognaths and platyhelminths. By using a model of sequence evolution that accounts for heterogeneity in amino acid composition across sites and across lineages, our results provide an alternative hypothesis, placing phoronids as the sister group to bryozoans, contradicting recent hypotheses of Bryozoa sensu lato, i.e. (Ectoprocta, Entoprocta), and Polyzoa (Ectoprocta (Cycliophora, Entoprocta)). Phylogenetic reconstructions have revealed numerous examples of morphological convergence and plasticity, as well as cryptic species, in all three bryozoans classes, highlighting the importance of using molecular data in assessing species interrelationships and species boundaries, and thus in providing a true estimate of diversity at multiple taxonomic hierarchies. Future work is planned to utilize these instances of convergence to study their effect on species diversification rates, by interpreting a densely sampled phylogenetic framework, constructed using NGS technology, in light of the well-preserved fossil record of bryozoans. Furthermore, using RNA-seq, future work is projected to provide insights into the underlying gene-expression processes involved in the generation of different zooid types produced by a single colony genotype, thus taking the first step in developing bryozoans as a model to study the underlying molecular processes of morphological and functional disparity.
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