Geography meets ecology:developing proxies to understand variations of stream biodiversity

Abstract Freshwater ecosystems form unique environments with high biodiversity. However, freshwater biodiversity is increasingly threatened because of human activities, such as the ongoing climate change and land use alterations. To prevent the further decline in biodiversity, it is crucial to understand the factors that affect and modify biotic communities. For freshwater systems, information on the patterns and underlying echanisms of biodiversity is still inadequate, which may complicate any conservation and management efforts. Ecologists must often rely on different proxy variables in studies examining biodiversity-environment and biodiversity-space relationships due to difficulties in obtaining direct measures of numerous factors across large regions. Biodiversity patterns in streams have been shown to be structured by direct physical properties of the local habitat and by proxy features on the catchment and regional scales, but one problem has been related to only moderate explanatory power using such ‘traditional environmental variables’. The goal of this thesis was to study biodiversity patterns in northern streams by introducing the use of geographical proxy variables of environmental features (i.e. geodiversity) and dispersal (i.e. different geographical distances). More precisely, the aims were to 1) examine the effects of local environmental and geographical variables on stream biodiversity; 2) investigate how environmental and spatial distance types between stream sites affect the variation of stream insect communities; 3) compare the relative roles of habitat-scale geodiversity measures and traditional in-stream variables in explaining stream macroinvertebrate biodiversity and; 4) examine how catchment-scale geodiversity contributes to the variation in stream biodiversity in a boreal region. According to the results, traditional environmental variables contributed most to the variation in stream biodiversity. However, geographical proxies showed a clear usefulness in understanding biodiversity-environment relationships. It was demonstrated that physical distance measures describing dispersal routes also showed a notable role affecting community compositional variation between stream sites, implying that interesting patterns are shaped by dispersal processes in stream environments. Moreover, the results indicated that the geodiversity on local and catchment scales correlated with stream biodiversity, which underlines the value of geodiversity as a proxy to explain biodiversity variations in the freshwater realm. If further developed, similar proxy variables to those presented in this thesis could offer complementary insights to help explain the structuring of biodiversity patterns in streams. Finally, conservation efforts may also benefit from the identified cost-efficient proxy variables helping to understand the nuances in biodiversity variation

Spatiaalisen sijainnin, ympäristötekijöiden ja lajien levittäytymiskyvyn vaikutukset pohjaeläinyhteisöjen rakenteeseen subarktisissa virtavesissä

Eliöyhteisöjen rakenteen tiedetään olevan riippuvainen paikallisista ympäristötekijöistä ja lajien välisistä vuorovaikutuksista. Myös lajien leviäminen paikkojen välillä on tunnistettu, mutta kuitenkaan paikallisten ja alueellisten prosessien suhteellista merkitystä yhteisöjen koostumisessa ei vielä täysin tunneta. Erityisen hyvin tämä ilmenee virtavesien pohjaeläinyhteisöissä, osin paikallisten ja alueellisten tekijöiden sekä ympäristön monimutkaisen luonteen takia. Alueellisten tekijöiden aliarvioiminen voi aiheuttaa ongelmia esimerkiksi virtavesikunnostusten onnistumisen arvioinnissa, jossa pohjaeläimiä käytetään bioindikaattorilajeina. Tässä työssä tutkittiin paikallisten ja alueellisten tekijöiden vaikutusta pohjaeläinyhteisöjen muodostumisessa Tenojoen valuma-alueella Pohjois-Suomessa. Tutkimusta varten kerättiin pohjaeläinnäytteet kesäkuussa 2012 yhteensä 55 puro- ja jokiuomasta. Jokaisesta tutkimuspisteestä mitattiin selittävinä ympäristömuuttujina 15 eri parametria uoman fysikaalisista piirteistä veden kemiallisiin ominaisuuksiin. Spatiaalista sijaintia kuvattiin tutkimuspisteiden välisillä etäisyyksillä, jotka mitattiin kolmella eri tavalla. Nämä epäsuorasti eliöiden leviämisteitä kuvaavat reitit olivat maanyli-, vesireitti- ja optimaaliset etäisyydet. Keskeisenä tutkimusmenetelmänä käytettiin Mantelin etäisyysperusteista testiä. Testin avulla selvitettiin tutkimuspaikkojen yhteisörakenteen vaihtelun korrelaatiota ympäristötekijöiden ja maantieteellisten etäisyyksien kanssa. Lisäksi yhteisöjen vaihtelun kannalta tärkeimmät ympäristötekijät selvitettiin BIOENV (Best Subset of environmental Variables with Maximum Correlation With Community Dissimilarities) -menetelmällä. Eliöiden levittäytymiskyvyn vaikutuksen selvittämiseksi lajiaineisto jaettiin 7 ryhmään, jotka indikoivat lajien erilaista leviämiskykyä virtavesiympäristössä. Tulosten mukaan tutkimuspaikkojen lajisto poikkesi toisistaan, mutta erojen suuruus vaihteli tarkasteltavan lajiryhmän mukaan. Paremmin leviävien lajiryhmien yhteisöt olivat keskimäärin samankaltaisempia verrattuna heikomman leviämiskyvyn omaaviin lajeihin. Mantelin testin perusteella yhteisöjen vaihtelu oli enemmän riippuvainen paikallisista ympäristötekijöistä kuin spatiaalisesta sijainnista. Tämä ilmeni myös hajontakuvioiden perusteella, joissa yhteisöjen erilaisuus kasvoi ympäristögradientin mukaan. Kuitenkin lajiston jakaminen lajiryhmiin toi esille myös alueellisten tekijöiden merkityksen, sillä leviämiskyvyltään heikompien lajiyhteisöjen vaihtelu korreloi muita ryhmiä enemmän maantieteellisten etäisyystyyppien kanssa. Spatiaalisista etäisyyksistä tärkeimmiksi osoittautuivat vesireitit, jotka korreloivat etäisyysmitoista selvimmin yhteisöjen vaihtelun kanssa. Tämä oli odotettu tulos osoittaen vesireittien luonnollisen merkityksen hyönteisten selkeimpinä leviämisreitteinä. Tässä työssä kokeiltujen optimaalisten reittien roolista lajien leviämisteinä saatiin myös joitain viitteitä korostaen paikkatietomenetelmien tuomia mahdollisuuksia ekologisissa tutkimuksissa

Understanding environmental change through the lens of trait-based, functional, and phylogenetic biodiversity in freshwater ecosystems

Abstract In the era of the Anthropocene, environmental change is accelerating biodiversity loss across ecosystems on Earth, among which freshwaters are likely the most threatened. Different biodiversity facets in the freshwater realm suffer from various environmental changes that jeopardize the ecosystem functions and services important for humankind. In this work we examine how environmental changes (e.g., climate change, eutrophication, or invasive species) affect trait-based, functional, and phylogenetic diversity of biological communities. We first developed a simple conceptual model of the possible relationships between environmental change and these three diversity facets in freshwaters and, secondly, systematically reviewed articles where these relationships had been investigated in different freshwater ecosystems. Finally, we highlighted research gaps from the perspectives of organisms, ecosystems, stressors, and geographical locations. Our conceptual model suggested that both natural factors and global change operating at various spatial scales influence freshwater community structure and ecosystem functioning. The relationships between biodiversity and environmental change depend on geographical region, organism group, spatial scale, and environmental change gradient length. The systematic review revealed that environmental change impacts biodiversity patterns in freshwaters, but there is no single type of biodiversity response to the observed global changes. Natural stressors had different, even contradictory, effects (i.e., multiple, negative, and positive) on biodiversity compared with anthropogenic stressors. Anthropogenic stressors more often decreased biodiversity, although eutrophication and climate change affected freshwater ecosystems in a complex, more multi-dimensional way. The research gaps we identified were related, for example, to the low number of community-based biodiversity studies, the lack of information on true phylogenies for all freshwater organism groups, the missing evaluations whether species traits are phylogenetically conserved, and the geographical biases in research (i.e., absence of studies from Africa, Southern Asia, and Russia). We hope that our review will stimulate more research on the less well-known facets and topics of biodiversity loss in highly vulnerable freshwater ecosystems

Geography of global change and species richness in the North

Abstract Different components of global change (e.g., climate change, land use, pollution, and introduced species) continue to alter biodiversity worldwide. As northern regions are still relatively undisturbed and will likely face clear increases in temperature in the near-future, we examined the signs of biodiversity change due to anthropogenic stressors using a systematic review of previous studies. Our aim was to map where, in which way, and owing to which stressor biodiversity in northern regions has changed. We made a systematic literature search covering the years between 2000 and 2015 to obtain a comprehensive selection of recent research. As species richness was clearly the most commonly used indicator of biodiversity, we only concentrated on this aspect of biodiversity. We compared different biological groups, regions, and ecosystems. In the majority of the cases, anthropogenic stressors had decreased species richness, or had no effects on it, while increasing or multiple effects of stressors on species richness were less common. Freshwater ecosystems were most sensitive to anthropogenic stressors, as species richness often decreased owing to these stressors. The effects of land use on richness were covered relatively widely in the selected set of articles, but the effects of other components of global change on species richness require further attention. Despite the fact that pollution was not as commonly studied stressor as land use, it was the most harmful stressor type affecting species richness. Geographically, most studies were located in boreal Canada or Fennoscandia, while no studies were executed in vast circumpolar areas where the temperature rise has been greatest and the projected climate change is likely to be fast. Overall, we could find an alarmingly small set of studies that described the effects of actual anthropogenic stressors in real-life circumstances in northern high latitudes