Abstract (246 words)
Biological invasions have caused the loss of freshwater biodiversity
worldwide. The interplay between adaptive responses and demographic
characteristics is expected to be important for the resilience of
populations to biological invasions, but the interaction between these
factors is poorly understood. The native freshwater gastropodAmnicola limosus is distributed along spatial variation in impact
from an invasive molluscivorous fish (Neogobius melanostomus ), as
well as in calcium concentration, which limits the distribution of this
invader and thus provides refuges for the gastropods. We investigated if
refuge populations could provide migrants to declining invaded gastropod
populations through gene flow (i.e., demographic rescue), which could
also help maintain genetic diversity (i.e., genetic rescue). We also
tested for genetic adaptation of A. limosus to the invasive
predator and the low calcium habitats. We conducted pooled whole-genome
sequencing of twelve gastropod populations from the Upper St. Lawrence
River, complemented with a laboratory reciprocal transplant of wild
F0 A. limosus to measure survival and fecundity
in treatments of water calcium concentration (low/high) and round goby
cue (present/absent). We found that gene flow is restricted from the
low-calcium uninvaded refugia towards high-calcium invaded populations,
implying that the potential for demographic and genetic rescue is
limited. We also detected signatures of divergent selection between
habitat types and evidence of low fitness of individuals from refugia
populations in both habitat types, which could be either a cause or
consequence of the population structure between habitat types and
highlights the potential conflict between demographic/genetic rescue and
adaptation.
Keywords: genetic rescue, aquatic invasive species (AIS),
gastropods, whole-genome sequencing, adaptation