Species monitoring through space and time — combining microfluidic SNP
genotyping and environmental niche modelling on herbarium specimens of
the rare Northern dragonhead, Dracocephalum ruyschiana (Lamiaceae)
Abstract
Aim: We have studied population genetic change through time in the
Northern dragonhead, Dracocephalum ruyschiana (Lamiaceae); a plant
species that has experienced a drastic population decline and habitat
loss in Europe. We aimed at adding a historic level to the monitoring of
dragonhead by testing a microfluidic SNP array approach on herbarium
specimens up to 200 years old and comparing the genomic results with
that of modern populations in Norway. We also aimed to gain a more
holistic species knowledge to guide monitoring efforts by combining
herbarium genomics with ecological niche modelling (ENM). Location:
Europe (mainly Norway) Methods: We have applied a microfluidic array
consisting of 96 SNP markers on 130 herbarium specimens collected from
1820 to 2008. Obtained genotype data were compared with SNP data from
modern samples using various population genetic analyses. We used sample
metadata and observational records to model the species’ environmental
niche. Results: The SNP array successfully genotyped all included
herbarium specimens but was less capable of capturing diversity outside
of Norway, which was genetically highly divergent from the Norwegian
dragonheads. The historic-modern comparison revealed similar genetic
structure in space and limited change through time in Norway. The ENM
suggests that dragonhead has not fully achieved its potential
distribution in Norway, which is anchored in warmer and drier regions,
including areas where it does not occur today. Main conclusions: With
the appropriate design procedures, the SNP array technology is promising
for genotyping old herbarium specimens; an invaluable source of
information from the past. We found no signs of the severe reduction in
population size in our temporal genomic data of Norwegian dragonhead.
Regardless, the regional populations in Norway are genetically
divergent, both from each other and more so from populations outside of
Norway, rendering continued protection of all existing populations of
the species relevant.