Genetic connectivity in the world’s largest freshwater copepod

• Main Author: Jooste, Candice Megan
• Other Authors: Teske, P.R., Prof., Wasserman, R.J., Dr.
• Format: Other/Unknown Material
• Language: English
• Published: 2018
• Subjects: Copepoda; Freshwater biology; Calanus hyperboreus; Copepods
• Online Access: http://hdl.handle.net/10210/295365

Abstract: Temporary water bodies (temporary ponds) are home to a number of crustacean taxa with interesting life cycles. These environments only hold water for a limited period, drying out completely for extended periods of time. Population persistence for many species is reliant on the production of dormant propagules capable of withstanding desiccation. Temporary water bodies are scattered across the landscape and are essentially isolated from each other, but research has shown that dormant propagules may be transported between different ponds via mammal, bird and wind dispersal. However, it is unknown how frequently this occurs, and whether species-level genetic divergence between populations takes place at ecological or evolutionary timescales (i.e. decades vs. millennia). Lovenula raynerae is a recently described copepod that is thought to be the largest freshwater copepod known to science and is found exclusively in temporary ponds in the Eastern Cape of South Africa. The aims of the present study were threefold. First, the genetic connectivity among spatially separated populations (ponds) was reconstructed using partial sequences of the mitochondrial COI gene and the nuclear 18S rRNA. Secondly, I aimed to investigate historical migration events of the species lineages to determine divergence times within the species. Thirdly, the whole mitochondrial genome of the species was reconstructed to gain a better understanding of phylogenetic relationships within the Copepoda, which have received little previous attention despite their ubiquity and importance in the food web. Out of 365 specimens collected in 46 ponds, five major evolutionary lineages were identified that were highly divergent, and levels of genetic structure between the temporary ponds were extremely high (ST = 0.927). It was further found that L. raynerae has a complex history of connectivity that dates back to the Pleistocene and perhaps even the Pliocene. Phylogenetic analyses using the complete mitochondrial genome data show that L. raynerae has a monophyletic relationship with Calanus hyperboreus, and these two calanoid copepods have a sister taxon relationship with. M.Sc. (Zoology)