Biology subjects

Saastamoinen, M.

Publications and source records attributed to Saastamoinen, M..

3 recordsLinked to original sources

bioRxiv2018

Every cloud has a silver lining: Moderate plant water stress positively impacts development, immunity, and gut microbiota of a specialist herbivore

The ongoing global temperature rise has led to increasing frequency of drought events, negatively impacting vegetation and the living organisms relying on it. Extreme drought killing host plants can clearly reduce herbivore fitness, but the impact of moderate host plant water stress on insect herbivores can vary, and may even be beneficial. The Finnish Glanville fritillary butterfly (Melitaea cinxia) has faced reduced precipitation in recent years, which has impacted population dynamics. However, whether the negative effects depend on extreme desiccation killing the host plant or moderate drought impacting plant quality remains unclear. We assessed the performance of larvae fed on moderately water-stressed Plantago lanceolata in terms of growth, gut microbial composition and immune response. We found that larvae fed on water-stressed plants had better growth, a more heterogeneous bacterial community and a shifted fungal community in the gut, and up-regulated the expression of one candidate immune gene (pelle), whereas survival remained unaffected. Most of the measured traits showed considerable variation due to family structure. Our data suggest that in temperate regions moderate host plant water stress can positively shape resource acquisition of this specialized insect herbivore, potentially by increasing nutrient accessibility or concentration. Potentially, the better larval performance may be mediated by a shift of the microbiota on water-stressed plants, calling for further research especially on the understudied gut fungal community.

ecology↗

bioRxiv2018

Landscape permeability and individual variation in a dispersal-linked gene jointly determine genetic structure in the Glanville fritillary butterfly

There is now clear evidence that species across a broad range of taxa harbour extensive heritable variation in dispersal. While studies suggest that this variation can facilitate demographic outcomes such as range expansion and invasions, few have considered the consequences of intraspecific variation in dispersal for the maintenance and distribution of genetic variation across fragmented landscapes. Here we examine how landscape characteristics and individual variation in dispersal combine to predict genetic structure using genomic and spatial data from the Glanville fritillary butterfly. We used linear and latent factor mixed models to identify the landscape features that best predict spatial sorting of alleles in the dispersal-related gene phosphoglucose isomerase (Pgi). We next used structural equation modeling to test if variation in Pgi mediated gene flow as measured by Fst at putatively neutral loci. In a year when the population was expanding following a large decline, individuals with a genotype associated with greater dispersal ability were found at significantly higher frequencies in populations isolated by water and forest, and these populations showed lower levels of genetic differentiation at neutral loci. These relationships disappeared in the next year when metapopulation density was high, suggesting that the effects of individual variation are context dependent. Together our results highlight that 1) more complex aspects of landscape structure beyond just the configuration of habitat can be important for maintaining spatial variation in dispersal traits, and 2) that individual variation in dispersal plays a key role in maintaining genetic variation across fragmented landscapes.\n\nImpact summaryUnderstanding how fragmentation affects dispersal and gene flow across human-modified landscapes has long been a goal in evolutionary biology. It is typically assumed that individuals of the same species respond to the landscape in the same way, however growing evidence suggests that individuals can vary considerably in their dispersal traits. While the effects of this individual dispersal variation on range expansions and invasions have been well-characterized, knowledge of how it might mediate genetic responses to landscape fragmentation are almost entirely lacking. Here we demonstrate that individual variation in dispersal is key to the maintenance of genetic variation during a population expansion following a large decline in a butterfly metapopulation. We further show that spatial variation in dispersal is not maintained by the configuration of habitat patches alone, but by a more complex genotype-environment interaction involving the landscape matrix (i.e. landscape features found between habitat patches). This challenges the simplified landscape representations typically used in studies of dispersal evolution that ignore heterogeneity in the landscape matrix. More broadly, our results highlight the interplay of adaptive and neutral processes across fragmented landscapes, suggesting that an understanding of species vulnerability to landscape fragmentation requires consideration of both.

evolutionary biology↗

bioRxiv2017

Extensive phenotypic plasticity in a seasonal butterfly limits potential for evolutionary responses to environmental change

Understanding how populations adapt to changing environments is a major goal in evolutionary biology and ecology, and particularly urgent for predicting resilience to climate change. Phenotypic plasticity, the ability to express multiple phenotypes from the same genome, is a widespread adaptation to short-term environmental fluctuations, but whether it facilitates adaptation to environmental change on evolutionary timescales, such as those under climate change, remains contentious. Here, we investigate plasticity and adaptive potential in an African savannah butterfly displaying extensive plasticity as adaptation to predictable dry-wet seasonality. We assess the transcriptional architecture of seasonal plasticity and find pervasive gene expression differences between the seasonal phenotypes, reflecting a genome-wide plasticity programme. Strikingly, intra-population genetic variation for this response is highly depleted, possibly reflecting strong purifying selection in its savannah habitat where an environmental cue (temperature) reliably predicts seasonal transitions and the cost of a mismatched phenotype is high. Under climate change the accuracy of such cues may deteriorate, rendering dominant reactions norm maladaptive. Therefore, depleted variation for plasticity as reported here may crucially limit evolutionary potential when conditions change, and seasonally plastic species may in fact be especially vulnerable to climate change.

evolutionary biology↗