The added value of geodiversity indices in explaining variation of stream macroinvertebrate diversity

Geodiversity, i.e. the variety of the abiotic environment, is considered to be positively correlated to biodiversity. In streams, the importance of physical heterogeneity for biodiversity variation is well known, but the usefulness of explicitly measured geodiversity indices to account for biodiversity has not been tested. We developed a technique to measure in-stream geodiversity, based on different types of stream flow, geomorphological processes and landforms observed from photographs taken during the field work, and substrates based on traditional field observations. We further tested the utility of these geodiversity measures in explaining variation in the biodiversity of macroinvertebrates in near-pristine streams. Our specific objective was to examine the explanatory power of geodiversity compared to traditional environmental variables, such as water chemistry, depth and current velocity. While most biodiversity indices correlated more strongly with traditional environmental variables, the influence of geodiversity on biodiversity was also evident. Unique effect of flow richness on species richness and that of total geodiversity on functional richness were higher than those of the traditional environmental variables. Our findings suggested that in-stream geodiversity offers a valuable concept for characterizing stream habitats. If further developed and tested, in-stream geodiversity can be used as a cost-efficient proxy to explain variation in biodiversity in stream environments.Peer reviewe

Highly variable species distribution models in a subarctic stream metacommunity : Patterns, mechanisms and implications

Special Issue: Metacommunities in river networks: The importance of network structure and connectivity on patterns and processes1. Metacommunity theory focuses on assembly patterns in ecological communities, originally exemplified through four different, yet non-exclusive, perspectives: patch dynamics, species sorting, source-sink dynamics, and neutral theory. More recently, three exclusive components have been proposed to describe a different metacommunity framework: habitat heterogeneity, species equivalence, and dispersal. Here, we aim at evaluating the insect metacommunity of a subarctic stream network under these two different frameworks. 2. We first modelled the presence/absence of 47 stream insects in northernmost Finland, using binomial generalised linear models (GLMs). The deviance explained by pure local environmental (E), spatial (S), and climatic variables (C) was then analysed across species using beta regression. In this comparative analysis, site occupancy, as well as taxonomic and biological trait vectors obtained from principal coordinate analysis, were used as predictor variables. 3. Single-species distributions were better explained by in-stream environmental and spatial factors than by climatic forcing, but in a highly variable fashion. This variability was difficult to relate to the taxonomic relatedness among species or their biological trait similarity. Site occupancy, however, was related to model performance of the binomial GLMs based on spatial effects: as populations are likely to be better connected for common species due to their near ubiquity, spatial factors may also explain better their distributions. 4. According to the classical four-perspective framework, the observation of both environmental and spatial effects suggests a role for either mass effects or species sorting constrained by dispersal limitation, or both. Taxonomic and biological traits, including the different dispersal capability of species, were scarcely important, which undermines the patch dynamics perspective, based on differences in dispersal ability between species. The highly variable performance of models makes the reliance on an entirely neutral framework unrealistic as well. According to the three-component framework, our results suggest that the stream insect metacommunity is shaped by the effect of habitat heterogeneity (supporting both species-sorting and mass effects), rather than species equivalence or dispersal limitation. 5. While the relative importance of the source-sink dynamics perspective or the species-sorting paradigm cannot be deciphered with the data at our disposal, we can conclude that habitat heterogeneity is an important driver shaping species distributions and insect assemblages in subarctic stream metacommunities. These results exemplify that the use of the three-component metacommunity framework may be more useful than the classical four perspective paradigm in analysing metacommunities. Our findings also provide support for conservation strategies based on the preservation of heterogeneous habitats in a metacommunity context.Peer reviewe

Does catchment geodiversity foster stream biodiversity?

Context One approach to maintain the resilience of biotic communities is to protect the variability of abiotic characteristics of Earth's surface, i.e. geodiversity. In terrestrial environments, the relationship between geodiversity and biodiversity is well recognized. In streams, the abiotic properties of upstream catchments influence stream communities, but the relationships between catchment geodiversity and aquatic biodiversity have not been previously tested. Objectives The aim was to compare the effects of local environmental and catchment variables on stream biodiversity. We specifically explored the usefulness of catchment geodiversity in explaining the species richness on stream macroinvertebrate, diatom and bacterial communities. Methods We used 3 geodiversity variables, 2 land use variables and 4 local habitat variables to examine species richness variation across 88 stream sites in western Finland. We used boosted regression trees to explore the effects of geodiversity and other variables on biodiversity. Results We detected a clear effect of catchment geodiversity on species richness, although the traditional local habitat and land use variables were the strongest predictors. Especially soil-type richness appeared as an important factor for species richness. While variables related to stream size were the most important for macroinvertebrate richness and partly for bacterial richness, the importance of water chemistry and land use for diatom richness was notable. Conclusions In addition to traditional environmental variables, geodiversity may affect species richness variation in streams, for example through changes in water chemistry. Geodiversity information could be used as a proxy for predicting stream species richness and offers a supplementary tool for conservation efforts.peerReviewe

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

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 mechanisms 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

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

Appendix_Teno_2012_env&coord

Environmental and spatial coordinate data for 55 stream sites in the River Tenojoki basin

Appendix_Teno_2012_spe

Site-by-species dataset for the insects found in the 55 stream sites in the River Tenojoki Basin

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