Since the 19th International C. elegans Meeting in 2013, discovery of new Caenorhabditis species has continued at a rapid rate. We now know of 63 species, 51 of which are in culture. All new species were found in tropical locations.
A molecular phylogeny for 41 Caenorhabditis species was calculated with sequence data of 22 genes that were analyzed with three different algorithms. Previously reconstructed relationships within the genus are confirmed. Caenorhabditis contains three large monophyletic groups: The Drosophilae super group and the Japonica group and Elegans groups within the Elegans super group. Four species are not part of these clades and branch off early. Relationships within the Elegans super group are generally well resolved but the position of C. kamaaina remains uncertain. Two species isolated from fresh figs and likely associated with fig-wasps (Kanzaki pers. comm.) branch off as the sister group of C. elegans. The relationships within the Drosophilae super group are less well supported with conflicting placements of several subclades. We are currently incorporating the remaining species into the phylogeny.
Light and scanning electron microscopic evaluation of morphology show that the diversity in phenotypic characters is large across the genus as a whole. However, most of this diversity is found in the Drosophilae super group and the basally branching species. Phenotypic diversity within the Elegans group is small in comparison. This is in contrast to the rate of molecular diversity, which is more uniform across all Caenorhabditis species. The analysis of phenotypic characters confirms that homoplasy is extensive and affects almost all characters studied.
So far, genomes of 16 species have been sequenced. An initiative to sequence the genomes of all remaining Caenorhabditis species in culture was launched by Mark Blaxter and his lab in 2014 (http://caenorhabditis.bio.ed.ac.uk/).
We continue to deposit morphological, biogeographical, ecological, sequence, and taxonomic data on all Caenorhabditis species in the open-access online database RhabditinaDB (http://wormtails.bio.nyu.edu/Databases). Information about Caenorhabditis isolates is also found in a WIKI on WormBase (http://evolution.wormbase.org/index.php/Main_Page).
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