Species delimitation in wolf spiders (Lycosidae) using DNA barcoding and double-digest restriction site associated DNA sequencing

Thesis event information

Date and time of the thesis defence

Place of the thesis defence

IT116, Linnanmaa campus, University of Oulu

Topic of the dissertation

Species delimitation in wolf spiders (Lycosidae) using DNA barcoding and double-digest restriction site associated DNA sequencing

Doctoral candidate

Master of Science Vladislav Ivanov

Faculty and unit

University of Oulu Graduate School, Faculty of Science, Ecology and genetics research unit

Subject of study

Genetics and ecology

Opponent

PhD, Docent Pedro Miguel Cardoso, University of Helsinki

Custos

PhD/Senior Curator Marko Mutanen, University of Oulu

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Identification and delimitation of wolf spider species using DNA

There are millions of species inhabiting our planet. The number of species experts (taxonomists) that know in detail how to identify and describe them is low and continues to decrease. At the same time, only 20% of biodiversity is known to humanity. This situation is often referred to as “taxonomic impediment”.
Some twenty years ago scientists from Canada started to propagate idea that short DNA sequences (termed DNA barcodes) can be used to efficiently identify species. That led to emergence of large database called BOLD (http://boldsystems.org/) where millions of DNA barcode sequences since have accumulated. Simultaneously, taxonomists attempted to use these data to establish boundaries between species, which is not a trivial task given that majority of unknown species belong to heavily understudied groups of organisms.
The time passed and it became obvious that DNA barcodes work well, but not for all cases. There are groups of animals and plants where well described species boundaries have been shown not to coincide with patterns revealed in DNA barcodes. Such cases are very important to study for researchers to understand DNA data correctly to describe and identify known and unknown species.
My doctoral thesis is focusing on such complicated cases known for wolf spiders (family Lycosidae). I used genomic DNA of the target species or populations to understand why classical approach to delineate species conflicts with the picture drawn by DNA barcodes, and whether genomic data can be used as a standard tool to establish species boundaries. The genomic data comes from special technique called double digest restriction site associated DNA sequencing (ddRADseq) that allows for sampling thousands of areas of the genome to study evolutionary processes that happened in the past or that are ongoing.
I studied wolf spiders collected within large area that cover Canada, USA, Greenland, Faroe Islands, Finland, France, Slovakia and Far East Russia. My results suggest that conflicting patterns between DNA barcodes and traditional species circumscription result from gene exchange between species that has presumably happened during glaciation and inter-glacial events in the northern hemisphere. The results also suggest that ddRADseq data can reliably be used for species assignments and the method can be standardized to concern any group of organisms. The latter is important because it enables application of standard species delimitation criteria across different groups of organisms and, thus, building a more reliable and stable classification system for life.
Last updated: 21.3.2022