Evolutionary relationship of Sphaerodoridae

Small grown species with spherical protrusions, called macrotubercles, on their back are the most characteristic features of the polychaete family Sphaerodoridae. A small group of polychaetes with about 110 species in 10 genera. With an overall aim to study evolutionary relationships of the group, we first started to study relationships within the family, but also its position within the polychaete group Phyllodocida.

Results from analyses of evolutionary relationships of Sphaerodoridae. Modified from Capa et al. 2016.
Results from analyses of evolutionary relationships of Sphaerodoridae. Modified from Capa et al. 2016.

We hired Maria Capa as postdoc to lead this project, and the first year she spent a lot of time travelling to different museums to examine type specimens of as many species as possible. This also made it possible to get hand of specimens preserved in ethanol suitable for molecular studies. We teamed up with Maite Aguado, and after a while got hand of a representative collection of species across the family.

Our study clearly find the family Sphaerodoridae monophyletic. But after this study the position of Sphaerodoridae within Phyllodocida remains unresolved. It was not possible to establish a sister group relationship. Conclusions could, however, be reached among genera and species. The study state that Sphaerodoridium and Sphaerodoropsis are not monophyletic groups, supporting earlier morphological assessments of Sphaerodoropsis being catch-bag of species with a range of different appearances. It was also found that Clavodorum and Sphaerodoridium was nested together.

Although new insight could be given in sphaerodorid relationships using molecular studies as a range of taxa where included, we need more representatives from different groups to provide further knowledge and answer questions on relationships between species and groups within the family.

 

References:

Capa M, Aguado M, Bakken T. 2016. Phylogenetic hypothesis of Sphaerodoridae Malmgren, 1967 (Annelida) and its position within Phyllodocida. Cladistics 32: 335-350. DOI: 10.1111/cla.12134