Browsing by Subject "range expansion"

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  • Rolls, Robert J.; Hayden, Brian; Kahilainen, Kimmo K. (2017)
    Climate change and species invasions represent key threats to global biodiversity. Subarctic freshwaters are sentinels for understanding both stressors because the effects of climate change are disproportionately strong at high latitudes and invasion of temperate species is prevalent. Here, we summarize the environmental effects of climate change and illustrate the ecological responses of freshwater fishes to these effects, spanning individual, population, community and ecosystem levels. Climate change is modifying hydrological cycles across atmospheric, terrestrial and aquatic components of subarctic ecosystems, causing increases in ambient water temperature and nutrient availability. These changes affect the individual behavior, habitat use, growth and metabolism, alter population spawning and recruitment dynamics, leading to changes in species abundance and distribution, modify food web structure, trophic interactions and energy flow within communities and change the sources, quantity and quality of energy and nutrients in ecosystems. Increases in temperature and its variability in aquatic environments underpin many ecological responses; however, altered hydrological regimes, increasing nutrient inputs and shortened ice cover are also important drivers of climate change effects and likely contribute to context-dependent responses. Species invasions are a complex aspect of the ecology of climate change because the phenomena of invasion are both an effect and a driver of the ecological consequences of climate change. Using subarctic freshwaters as an example, we illustrate how climate change can alter three distinct aspects of species invasions: (1) the vulnerability of ecosystems to be invaded, (2) the potential for species to spread and invade new habitats, and (3) the subsequent ecological effects of invaders. We identify three fundamental knowledge gaps focused on the need to determine (1) how environmental and landscape characteristics influence the ecological impact of climate change, (2) the separate and combined effects of climate and non-native invading species and (3) the underlying ecological processes or mechanisms responsible for changes in patterns of biodiversity.
  • Bergman, Nora (Helsingin yliopisto, 2021)
    Rapid environmental changes over the last 100 years have led to substantial range shifts across taxonomic groups. Understanding what facilitates successful shifts is important for predicting ecological consequences and planning efficient conservation actions. Interestingly, the very process of range expansion can affect the success of the shift by causing genetic changes in the expanding populations. Theory predicts that without sufficient gene flow, repeated founder events and strong genetic drift can result in allele frequency gradients and loss of genetic diversity along the expansion axis. Empirical studies testing these expectations in environment-driven range shifts are still relatively scarce, and how range expansions affect genetics in highly mobile species remains unclear. In this study, I investigated the genetic consequences of a recent range expansion in a long-distance migratory passerine, the reed warbler (Acrocephalus scirpaceus). Utilizing genome-wide data from restriction site-associated DNA sequencing (RAD-seq), I studied whether the expansion was reflected in either population structure or genetic diversity of the recently established Finnish range edge population. Despite philopatry and genetic differentiation to the range core populations, principal component analysis (PCA) and a model-based Bayesian clustering approach (fineRADstructure) revealed a lack of spatial population structure along a putative colonization route. Levels of genetic diversity, based on expected heterozygosity, nucleotide diversity, and private allele count, were found to be very similar between range edge (Finland) and range core (Central Europe). The results likely indicate high levels of gene flow both within the new population and across greater spatial distances during or after the range expansion. Due to a detected sequencing batch effect, however, the exact diversity estimates must be considered preliminary. These findings suggest that species with high enough dispersal propensity may escape the predicted genetic costs of range expansions, retaining high levels of genetic variation at range margins. This study provides valuable insights for understanding range shifts in mobile taxa, and highlights the need to investigate further the traits of species that enable the preservation of evolutionary potential during range shifts.
  • Blomberg, Anna S.; Vasko, Ville; Salonen, Saku; Petersons, Gunars; Lilley, Thomas M. (2021)
    Highly mobile species are considered to be the first to respond to climate change by transforming their ranges of distribution. There is evidence suggesting that Pipistrellus nathusii, a species capable of long-distance migration, is expanding both its reproduction and overwintering ranges to the North. We recorded the echolocation calls of bats at 16 sites in South-Western Finland on two consecutive winters, and detected calls of P. nathusii at one of the sites throughout the second winter. To our knowledge, this is the northernmost record of an overwintering P. nathusii, and contributes to evidence that the species is already responding to climate change.
  • Rousi, Matti; Possen, Boy; Ruotsalainen, Seppo; Silfver, Tarja Hannele; Mikola, Juha Tapio (2018)
    The acclimation capacity of leading edge tree populations is crucially important in a warming climate. Theoretical considerations suggest that adaptation through genetic change is needed, but this may be a slow process. Both positive and catastrophic outcomes have been predicted, while empirical studies have lagged behind theory development. Here we present results of a 30-year study of 55,000 Scots pine (Pinus sylvestris) trees, planted in 15 common gardens in three consecutive years near and beyond the present Scots pine tree line. Our results show that, contrary to earlier predictions, even long-distance transfers to the North can be successful when soil fertility is high. This suggests that present northern populations have a very high acclimation capacity. We also found that while temperature largely controls Scots pine growth, soil nutrient availability plays an important role-in concert with interpopulation genetic variation-in Scots pine survival and fitness in tree line conditions. These results suggest that rapid range expansions and substantial growth enhancements of Scots pine are possible in fertile sites as seed production and soil nutrient mineralization are both known to increase under a warming climate. Finally, as the ontogenetic pattern of tree mortality was highly site specific and unpredictable, our results emphasize the need for long-term field trials when searching for the factors that control fitness of trees in the variable edaphic and climatic conditions of the far North.
  • Lehmann, Philipp; Westberg, Melissa; Tang, Patrik; Lindstrom, Leena; Kakela, Reijo (2020)
    During winter insects face energetic stress driven by lack of food, and thermal stress due to sub-optimal and even lethal temperatures. To survive, most insects living in seasonal environments such as high latitudes, enter diapause, a deep resting stage characterized by a cessation of development, metabolic suppression and increased stress tolerance. The current study explores physiological adaptations related to diapause in three beetle species at high latitudes in Europe. From an ecological perspective, the comparison is interesting since one species (Leptinotarsa decemlineata) is an invasive pest that has recently expanded its range into northern Europe, where a retardation in range expansion is seen. By comparing its physiological toolkit to that of two closely related native beetles (Agelastica alniandChrysolina polita) with similar overwintering ecology and collected from similar latitude, we can study if harsh winters might be constraining further expansion. Our results suggest all species suppress metabolism during diapause and build large lipid stores before diapause, which then are used sparingly. In all species diapause is associated with temporal shifts in storage and membrane lipid profiles, mostly in accordance with the homeoviscous adaptation hypothesis, stating that low temperatures necessitate acclimation responses that increase fluidity of storage lipids, allowing their enzymatic hydrolysis, and ensure integral protein functions. Overall, the two native species had similar lipidomic profiles when compared to the invasive species, but all species showed specific shifts in their lipid profiles after entering diapause. Taken together, all three species show adaptations that improve energy saving and storage and membrane lipid fluidity during overwintering diapause. While the three species differed in the specific strategies used to increase lipid viscosity, the two native beetle species showed a more canalized lipidomic response, than the recent invader. Since close relatives with similar winter ecology can have different winter ecophysiology, extrapolations among species should be done with care. Still, range expansion of the recent invader into high latitude habitats might indeed be retarded by lack of physiological tools to manage especially thermal stress during winter, but conversely species adapted to long cold winters may face these stressors as a consequence of ongoing climate warming.
  • Välkki, Anna (Helsingin yliopisto, 2021)
    Birdsong is information, communication and a target of sexual selection. Song complexity is the variation in bird song structure. Within-song complexity is variation in song components, in number and order of syllables and phrases. Song complexity is an honest trait under sexual selection and competition for mates increases it. When species expands its range front to a new area, the population density is low in the beginning. Males in the new population do not need to compete as hard as before, because population density is decreased, which decreases song complexity. Many warblers have complex songs and they do not have a colourful plumage. It is well possible that song complexity is the main target of sexual selection in warblers. The purpose of this study was to investigate if there were differences in song complexity in Eurasian reed warblers (Acrocephalus scirpaceus) breeding at their range front in Finland. The population of Finland is 100 years old and the population density is still decreased in compared to Central Europe. My hypothesis was that reed warblers would sing less complex songs at lower densities as competition for mates is low. I used song recordings of 51 reed warbler males, which I recorded during the breeding season 2019 in song complexity analyses. Recordings were from South Finland from 14 locations in 6 municipalities. Most of the recording places were coastal reedbeds. A couple of recording places were reedbeds in inland ponds and reedbeds in a flooded forest. I counted the male densities within 50 m and 200 m radius around the recorded males using Google Maps. I took account the males which were at least 20 m away from each other and were there in the same week than the recorded male. I extracted four within-song complexity variables from the recordings: Total number of syllables, number of syllable types, number of syllable transitions and mean frequency bandwidth. I measured song complexity with spectral analyses using Koe, a bioacoustic software. I did next analyses with R to see if there is association between local density and complexity. I found that one of the song complexity variables, total number of syllables, was significantly positively associated with the density of singing males within 200 m radius. The other variables were not significantly associated with male density, but number of syllable types and number of syllable transitions showed a similar relationship with singing male density within 200 m. Previous studies support the hypothesis that higher local density can increase some aspects of song complexity, for example number of syllables or length of phrases. Some males did not have neighbours within 50 m. Density within 50 m had no significant relationship with song complexity variables. However, mean frequency bandwidth, total number of syllables and number of syllable types showed more variation when neighbours were present, which suggest that males increase their effort when they have competition. Finally, I found that the number of syllable transitions decreased as the breeding season progressed. This could be explained with younger birds coming to breed later or with paired males singing less.