Fish colonization patterns in central Sweden from dropletdigital PCR and shotgun sequencing of sedimentary DNA

• The natural establishment of Scandinavian fish populations took place following the lastdeglaciation 9,000 to 12,000 years ago when the retreating ice exposed new habitats. Accessibilityof lakes from the Proto-Baltic sea and the southern freshwater habitats was influenced by theirelevation relative to the post-glacial coastline, with some lakes being unreachable due to migrationbarriers. Long standing hypotheses regarding colonization routes have been formulated based onmodern distribution patterns, knowledge of historic climate variations, and species’ tolerances toenvironmental conditions. These hypotheses have not been tested with other forms of evidencebecause long-term data on past fish histories are limited. In this study, the colonization history ofseveral fish species was investigated using historical data combined with analyses of sedimentaryDNA from Lake Hotagen in central Sweden which is located above the post-glacial coastline.DNA was analyzed with droplet digital PCR (ddPCR) and metagenomic shotgun sequencingapproaches. The ddPCR array used specific primers of seven species known to have beenhistorically present at the lake, and successfully detected 5/7 species in the top 80 cm (~3000 years)of the sediment core where DNA was best preserved. Metagenomics however detected 6/8expected genera in all sediment samples dating back 7000 years. Based on our findings, we inferthat 1) (dd)PCR based methods had too low sensitivity to allow consistent detection of fish inancient samples and 2) metagenomics, while sufficiently sensitive, require expanded databases toincrease granularity across species, especially those who are currently underrepresented. 3) Mostfish species likely colonized lake Hotagen soon after the last deglaciation despite the presence ofmigration barriers.

Ämnesord

NATURVETENSKAP  -- Biologi -- Ekologi (hsv//swe)

NATURAL SCIENCES  -- Biological Sciences -- Ecology (hsv//eng)

Nyckelord

biology

biologi

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