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 gastropod Amnicola 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.

Plant secondary metabolites (PSMs) are produced by plants to overcome environmental challenges, both biotic and abiotic. We were interested in characterizing how autumn seasonality in temperate and subtropical climates affects typical PSM production in comparison to herbivory. Herbivory is commonly measured from spring to summer when plants have high resource availability and are prioritizing growth and reproduction. However, autumn seasonality also challenges plants as they cope with limited resources and prepare survival for winter. This suggests a potential gap in knowledge on how autumn seasonality affects PSM production differently from herbivory. Using meta-analysis, we recorded production of 22 different PSM subgroups from 58 published papers to detect a typical response across all PSMs. We also compared production of five phenolic subgroups – hydroxybenzoic acids, flavan-3-ols, flavonols, hydrolysable tannins, and condensed tannins. We calculated effect sizes from herbivory studies (absence to presence) and temperate to subtropical seasonal studies (summer to autumn), while considering other variables (e.g., plant type, increase in time since herbivory, temperature, and precipitation). We did not detect a shared effect of herbivory or season on PSM production across all subgroups. However, we discovered herbivory having a positive effect on flavonol production and autumn seasonality having a positive effect on flavan-3-ol and condensed tannin production. We discuss how these responses might stem from three factors: 1. some PSMs are constitutively produced by plants in autumn whereas others are induced only following herbivory, 2. plants produce metabolites with higher costs only during seasons when other resources for growth and reproduction are less available, and 3. some PSM subgroups serve more than one function for plants and such functions can be season dependent. The outcome of our meta-analysis is that autumn seasonality changes PSM production differently from herbivory, and we see value in further investigating seasonality-herbivory interactions with plant chemical defense.

Plant secondary metabolites (PSMs) are produced by plants to overcome environmental challenges, both biotic and abiotic. We were interested in characterizing how autumn seasonality in temperate and subtropical climates affects typical PSM production in comparison to herbivory. Herbivory is commonly measured from spring to summer when plants have high resource availability and are prioritizing growth and reproduction. However, autumn seasonality also challenges plants as they cope with limited resources and prepare survival for winter. This suggests a potential gap in knowledge on how autumn seasonality affects PSM production differently from herbivory. Using meta-analysis, we recorded production of 22 different PSM subgroups from 58 published papers to detect a typical response across all PSMs. We also compared production of five phenolic subgroups – hydroxybenzoic acids, flavan-3-ols, flavonols, hydrolysable tannins, and condensed tannins. We calculated effect sizes from herbivory studies (absence to presence) and temperate to subtropical seasonal studies (summer to autumn), while considering other variables (e.g., plant type, increase in time since herbivory, temperature, and precipitation). We did not detect a shared effect of herbivory or season on PSM production across all subgroups. However, we discovered herbivory having a positive effect on flavonol production and autumn seasonality having a positive effect on flavan-3-ol and condensed tannin production. We discuss how these responses might stem from three factors: 1. some PSMs are constitutively produced by plants in autumn whereas others are induced only following herbivory, 2. plants produce metabolites with higher costs only during seasons when other resources for growth and reproduction are less available, and 3. some PSM subgroups serve more than one function for plants and such functions can be season dependent. The outcome of our meta-analysis is that autumn seasonality changes PSM production differently from herbivory, and we see value in further investigating seasonality-herbivory interactions with plant chemical defense.

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 gastropod Amnicola limosa is distributed along spatial variation in impact from an invasive molluscivorous fish (Neogobius melanostomus), as well as calcium concentrations, limiting the distribution of this invader (refuges). We investigated the potential for genetic adaptation of A. limosa 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. limosa to measure survival and fecundity in treatments of water calcium concentration (low/high) and round goby cue (present/absent). We quantified gene flow between the habitat types to test how population structure might interact with adaptation. We found that low calcium, uninvaded habitats could act as refugia for the gastropods from the invasive fish and provide migrants to declining invaded gastropod populations through strong gene flow (i.e., demographic rescue), which also maintained genetic diversity (i.e., genetic rescue). However, we also detected signatures of divergent selection between habitat types and evidence of low fitness of individuals from refuge populations in both habitat types. This suggests that migrants from refuges could introduce maladapted alleles to recipient populations in high calcium, invaded habitats, thereby reducing fitness via outbreeding depression and producing conflict between demographic, genetic, and evolutionary rescue.