Incomplete Reproductive Isolation Between Genetically Distinct Sympatric Clades of the Pennate Model Diatom Seminavis robusta

Publication date: August 2018Source: Protist, Volume 169, Issue 4Author(s): Sam De Decker, Pieter Vanormelingen, Eveline Pinseel, Josefin Sefbom, Sien Audoor, Koen Sabbe, Wim VyvermanIncomplete reproductive isolation between genetically distinct taxa provides an interesting opportunity for speciation and adaptation studies. This phenomenon is well-described in macro-organisms, but less experimental evidence is available for unicellular eukaryotes. Here, we document the sympatric occurrence of genetically differentiated populations of the pennate model diatom Seminavis robusta in coastal subtidal biofilm communities and show widespread potential for gene flow between them. Based on sequence variation in the plastid-encoded rbcL gene, three distinct clades were identified. Morphological variation between the clades reflected their phylogenetic relationships, with subtle differences in valve morphology in the most distant clade compared to the other two clades, which were indistinguishable. Using a large number of experimental crosses we showed that, although reproductive output was significantly lower compared to the majority of within-clade crosses, approximately 34.5% of the inter-clade crosses resulted in viable and fertile progeny. While the nature of the incomplete reproductive isolation remains unknown, its occurrence in natural diatom populations represents an additional mechanism contributing to population genetic structuring and adaptation and can spur further research...

Source: Protist - July 10, 2018 Category: Molecular Biology Source Type: research