«3 Work plan 3.1 Detailed research plan 3.1.1. Overview Connectivity – a central concept in ecosystem studies that can now be tested and developed ...»
3 Work plan
3.1 Detailed research plan
Connectivity – a central concept in ecosystem studies that can now be tested and developed with
molecular genetic experiments
Connectivity between system constituents, i.e., interaction distances, has been identified to play a key role
in driving the processes that maintain and define systems, independent of the system type or its complexity
(With 1997, Bolliger et al. 2003, Green and Sadedin 2005). For ecological systems, it has been hypothesized that the degree and type of interactions (connectivity) between abiotic and biotic system constituents plays an important role in shaping the system's properties and dynamics (With 1997, Bolliger et al. 2003, Green and Sadedin 2005). It is widely recognized and accepted that ecosystems occupy dynamic, non-equilibrium, states, subject to a variety of disturbances to which they have varying capacities of response. Connectivity within landscapes and among their biotic elements not only describes environmental patterns (Taylor et al. 1993, With et al. 1997, Green and Sadedin 2005), but is the essential ingredient that contributes to ecosystem abilities to absorb the effects of disturbance or recover from it.
Consequently, the distribution of habitats and the dispersal abilities of organisms effectively connect landscape elements (Gardner et al. 1987, O'Neill et al. 1988, With and Crist 1995, Kindlmann et al. 2005) and define the capacity of ecosystems to resist and respond to perturbation. Modern human-dominated environments are subject to novel, more frequent and more extreme environmental perturbations to which environmental response remains uncertain. As connectivity is a central feature of this capacity, it is a societal need that scientific understanding of connectivity is improved and integrated into management action.
Connectivity in landscapes can be assessed structurally where connectivity refers to structure only.
Alternatively, habitat connectivity can be assessed functionally, where biotic responses to the landscape elements are considered along with the structure of habitats (Tischendorf 2001, Tischendorf and Fahrig 2001). Thus, depending on the organisms studied, structurally connected habitats may not be functionally connected or vice versa, indicating that the same structural connectivity may be perceived differently by different organisms.
Goals and framework of the ENHANCE project ENHANCE tackles the challenges on connectivity listed above in a concerted action of different research fields (terrestrial and aquatic population ecology, population genetics, spatio-temporal ecological modeling, socio-economics) of institutions of the ETH domain (WSL, ETHZ, EAWAG, EPFL). Furthermore, powerful methods (i.e., molecular-genetic analysis) allow conducting species dispersal experiments and identify functional populations in a new manner. The ENHANCE project combines such cutting edge technologies
with numeric modeling as well as socialscience approaches and economic analysis. ENHANCE goals are:
(1) To quantify the effects of increased landscape connectivity (de-fragmentation) on various biotic 2 2 levels (genes, species, communities) and spatial scales (m to km ) prior and after interventions for aquatic and terrestrial habitats.
(2) To test fundamental questions of species dispersal, invasion, metapopulation viability, (re)colonisation and gene flow in relation to land-use and de-fragmentation interventions.
(3) To consider various types of spatial and spatially dynamic models to generalise and up-scale local empirical findings to the conservation-relevant landscape scale.
(4) To provide societal and economic assessments of the role of connectivity in the people-landscape relationships since successful development and implementation of management options require knowledge of people’s attitudes towards ecosystem enhancement, of economical effects and of the availability of effective (participatory) planning measures.
The ENHANCE lead research questions are:
Q1: How does landscape connectivity affect population genetic variability, and what is the potential for management intervention, among selected habitats and model species, to conserve this variability? At what scales are effects visible? Are there spatial or temporal connectivity thresholds?
Q2: What degree of landscape connectivity is needed to enable gene flow and metapopulation dynamics of selected species or species groups?
Q3: How do land-use patterns, processes and composition affect migration, dispersal and recolonisation for species in human-dominated landscapes? How tolerant are populations to land-use changes?
Q4: How does landscape and population connectivity relate to the provision and maintenance of ecosystem function and in which way does this contribute to human social and economic well-being?
Q5: Which (participatory) management and planning approaches and which institutional settings contribute best to make the implementation of ecosystem-management and de-fragmentation strategies effective and efficient?
3.1.2 Modular project structure The way ENHANCE is set up reflects the methodological and thematic variety of the project. As displayed in Fig. 1 effects of experimental interventions on functional connectivity are assessed at the gene (Module
1) and the population level (Module 2). Module 3 deals with species-specific relationships between functional and structural connectivity and identifies the role of connectivity in explaining genetic patterns on the landscape. Module 4 performs socio-economic assessment of landscapes with different connectivity including cost-benefit analyses. This module asseses whether landscapes beneficial to ecology are also perceived as such by people. We selected species based on module-specific requirements and on joint interests between the modules. ENHANCE assesses effects of connectivity for three habitats and intervention types which are important for Central Europe: agricultural, river/riparian and urban habitats (Fig. 1).
Fig. 1: ENHANCE modules, selected habitats, intervention types, and investigated species 5 Agricultural habitats (lead partner: S. Dorn) Within the Swiss agricultural scheme of subsidies (ÖQV; BLW 2005), different types of extensive meadows receive incentive payments, if they are arranged in a spatial way to increase connectivity. Different planning instruments (Regionale Richtpläne, Landschaftsentwicklungskonzepte LEKs; Bolliger et al. 2002) are used to guide the spatial arrangement of corresponding elements in the landscape.
Type of intervention: We compare pre- and post interventional conditions for areas in the Grenchner Witi (SO) and Berlingen (TG), i.e. model situations where extensive meadows have been artificially reconnected (defragmentation) and model situations where meadows are structurally disconnected (fragmentation). Model organisms are bees and flowering plants.
River/riparian habitats (lead partners: A. Peter, EAWAG, A. Schleiss, EPFL) The Swiss government 1 and several cantons are currently developing and implementing large river restoration projects, e.g. at the Rhone, Thur, Alpine Rhine and Aare rivers (Stremlow et al. 2001; Rhode et al. 2004, 2005).
Type of intervention: One aim of river restoration projects (river widening, gravel bank forming, installation of fish ramps etc.) is to increase the lateral and longitudinal connectivity along catchments. We will work with pre- and post-interventional conditions, i.e. rivers where restoration interventions have increased longitudinal and latitudinal connectivity vs. channeled situations. The model organism is brown trout (Fig. 1). Details on the location of the study area are being identified.
Urban habitats (lead partner: M. Moretti, WSL) Green spaces in urban or peri-urban areas are important mainly because of three reasons: (1) The urban habitats are the fastest growing land-use type worldwide; (2) Urban green patches represent ecologically significant parts and stepping stones in ecological networks, from the genetic to the landscape level; (3) Green squares, public and private gardens, parks or so-called urban wilderness spaces are socially important for the well-being of local residents, while green flat roofs are becoming an important urban element for replacing green areas. Areas in the cities of Lucerne, Zürich, and Lugano will be considered.
Types of intervention: The response of biodiversity, community composition, and functional diversity of target groups to connectivity patterns in urban matrices are assessed using field experiments (trap nest colonization, pittfall traps) to assess connectivity patterns according to the (i) mosaic theory using matrices of green areas differently connected at ground level, and the (ii) island theory using green flat roofs as a third dimension of connectivity, less investigated so far. Model organisms include carabid beetles and flying species (bees) in interaction with The hedgehog (Erinaceus europeaus) will also be used as model species to test fragmented vs. connected urban matrices (e.g. Bontadina et al. 1996; Rondini et al. 2002). Module 2 (agricultural habitat;
3.1.3. Detailed module description Module 1: Gene level: Molecular technology to identify connectivity with and without interventions in agricultural and river/riparian habitats (lead partners WSL/ETHZ/EAWAG, R.
Holderegger / J. Ghazoul / R. Billetter / A. Peter) Module 1 provides molecular genetic analyses for two different habitats (agriculture, river/riparian) for a set of model organisms (bees, vascular plants, fish). Module 1 is closely linked to Module 2 as both result in information on connectivity. Results from Module 1 provide baseline information for all parts of Module 2, since the genetic methods estimate current exchange of individuals (or genes) among habitat patches and, by doing so, determine the functional connectivity in agricultural and riparian landscapes. Three PhDs (1 WSL, 1 EAWAG, 1 ETHZ) will closely work together and will be supervised by A. Peter, R. Billeter, J.
Ghazoul and R. Holderegger.
The study design of Module 1 with respect to locations and species is as follows:
(i) Intervention/location and control sites: the quasi-experimental set-up requires sites where defragmentation interventions have already been taken and comparable, still fragmented control 2 sites. Where possible, Module 1 will work at the same locations as Module 2.
(ii) Species: Module 1 investigates species which are specific and typical for one of the two studied systems. Where possible, we will work with the same species as Module 2.
(iii) Markers: The development of microsatellite (AFLPs as an alternative) markers for several species is time-and labour-consuming. Ideally, we will work with species for which microsatellite markers have already been developed and are available. This methodological issue could restrict the choice of species. Additionally, mtDNA markers are used.
Agricultural habitats (2 PhDs, R. Holderegger, R. Billetter, J. Ghazoul) Task 1: We will first carry out complete surveys of the structural properties of the habitat patches and record the sizes of the population of an insect-pollinated vascular plant species (in collaboration with Module 3). We will then genetically investigate all populations to infer the recent (using assignment methods; Campbell et al. 2003) and the historical gene flow patterns (based on genetic structure; Lowe et al. 2004). We will additionally study contemporary gene flow by pollen and seed in this plant species as a direct measurement of realised connectivity at the local scale in a part of the landscape. In a rarely carried out complete way, we infer current gene flow patterns by parentage analysis (seed families to infer pollen parents and seed traps and/or seedlings to infer dispersal from mother plants based on seed coat genotypes; Godoy and Jordano 2001) using neutral nuclear micrcosatellites as genetic markers. Since parentage analysis (Sork et al. 1999) asks for a complete genetic survey of potential father/mother plants, we will artificially reduce the number of flowering plants in a given year, if necessary. In an experimental setup, we will also place grown plants in the landscape to artificially increase the connectivity among adjacent habitats.
Task 2: We will carry out a similar set of studies as given under task (1) for an insect which is characteristic of meadows (i.e., bees) to study historical and recent gene flow (Keller and Largadièr 2003) and, thus, the exchange of individuals at the landscape level (SSRS) by using assignment tests (Campbell et al. 2003). In order to analyse dispersal of this small animal, we will additionally use direct observation methods by releasing marked animals at a given place and by re-sampling them by line tracking methods (Diekotter et al. 2005).
Riparian/river habitats (1 PhD, A. Peter, EAWAG in collaboration with University of Bern) Task 3 The genetic analysis will be carried out on brown trout to document the role of experimental habitat fragmentation/de-fragmentation on its populations. Genetic diversity will be surveyed in brown trout populations and, espec inially, one population that has experienced increased upstream movements (immigration) of fish. Methodologically, we will combine a molecular survey based on nDNA microsatelites with a survey of DNA markers in a smaller sub-sample representing all possible source populations of migration. Ideally we would sample 100 brown trout individuals per population for the microsatellite study and include two individuals in the mtDNA analysis. For the genetic studies we cooperate with the Department of Fish Ecology and Evolution of EAWAG.
Module 2: Identification of the effects of connectivity intervention for species/populations in agricultural, river/riparian, and urban landscapes (lead partners: ETHZ, EPFL, EAWAG, WSL;
S. Dorn, M. Moretti, A. Schleiss, A. Peter) Module 2 provides baseline population ecological information on the effects of interventions on species and population dynamics for three habitat types (agriculture, river/riparian, urban). The model organism include selected native bee species for the agricultural and the urban habitats, selected carabid and orthoptera species for the urban habitats, and brown trout, a small-sized, and a cyprinid fish species for the river habitats.
Module also 2 provides species information required for molecular genetic analysis in Module 1.