LINKECOL Review Conference, Ceske Budejovice, Czech Republic, 25-27 April 2002
A LINKECOL Review Conference was held in Ceske Budejovice, Czech Republic, on 25-27 April 2002. Presentations were given on the Programme themes:
Theme 1 - Biological invasions and ecosystem processes
Theme 2 - Species diversity and ecosystem processes
Theme 3 - Ecology and evolution of indirect effects in ecosystems
Presentations were also given on LINKECOL Workshops to be held in 2002 and 2003.
Discussion Groups were also held on the following topics:
Biological invasions
Ecology and evolution of indirect effects in ecosystems
Trophic versus nontrophic interactions in biodiversity research
List of participants (PDF 62 KB)
Presentations
The following presentations on Themes 1-3 of the Programme were given (in alphabetical order of speaker):
Michael Bonkowski | Microbial multitrophic level interactions: effects on plant growth and herbivore performance |
Jérôme Cortet | Importance of the initial structure of mesofauna communities on species dynamics and organic matter decomposition - implications for ecotoxicological studies Abstract |
Olivier Dangles | Naturally acid ecosystems are diverse and functional: evidence from boreal streams |
Jaimie Dick | Predatory impact of the freshwater invader, Dikerogammarus villosus (Crustacea: Amphipoda) Abstract |
Mark Emmerson | How does community assembly affect the relationship betwen diversity and ecosystem functioning |
Maria Granberg |
|
Sue Grayston | Linking changes in soil microbial communities to acclimatino in soil respiratin with elevated temperature in a boreal forest |
Peter Hambäck | Plant-animal interactions in complex habitats: Ecology and evolution |
Andy Hector | Biodiversity and the stability and functioning of ecosystems: an overview of recent research |
Ferenc Jordan | The quantified importance of species and their interactions in a host-parasitoid community |
Pavel Kindlmann | Linking aphid abundance and throughfall chemistry in a spruce forest |
Karel Prach and Petr Pysek | Research into plant invasions in the Czech Republic: history, focus and topics |
Bernhard Stadler | Linking aphids and ecosystems: interactions under changing environmental conditions |
Barbara Urban-Malinga | Biodiversity and organic matter processing on sandy beach. An experimental approach Abstract |
Montserrat Vilà | Rates and impacts of biological invasions in terrestrial ecosystems |
Wolfgang Weisser | Testing the relationship between biodiversity and ecosystem function in grassland ecosystems Abstract |
Discussion Group - Biological Invasions
Conclusions
Co-chaired by Montserrat Vilà and Daniel Prati
The areas of research on biological invasions that need further research and that will pose novel questions to be discussed in near future workshops are (a) the mechanisms linking the impact in community structure and to (?)ecosystem function, (b) the interaction between biological invasions and environmental changes including landscape changes, and (c) the understanding of the similarities and differences between species colonization, range expansion of native species and invasion of exotics.
General patterns of the impacts of plant invasions on ecosystem functioning are difficult to achieve because most studies describe the effects of particular species on particular properties. To understand in a more mechanistic way the impact of plant invasions we need to disentangle if the effects are due to the presence of the invader per se, the changes in a community structure occurring after invasion or both.
On the other hand, there is a lack of knowledge on the ecological factors of the recipient ecosystem determining impact. Furthermore, despite that biological invasions are considered a major component of global change, the influence of various environmental changes on biological invasions have not been investigated in depth. When conducting these studies, both the changes in the mean (change in shift) and variation of environmental parameters should be considered as many species are limited in their distribution by extreme values rather than the mean value (e.g. temperature or humidity).
Moreover, because plant invasions homogenize the flora and fauna worldwide, the role of landscape structure is of particular importance. Landscape properties such as connectivity, fragmentation and changes in land-use could explain why some exotics have been successful in some regions but not in others. Even less is known on interactive effects of global change parameters such as altered climatic variability and habitat fragmentation on invasion probabilities worldwide. Evidently, many invasions also happen without obvious global change and this needs further assessment.
These abovementioned issues could largely enrich from research on succession ecology, ecology of colonizing species and , ecology of community assemblages and biodiversity and stability. For example, experimental studies have found that at the local scale species diversity reduces the colonization of native species. However, different patterns emerge at higher spatial scales. Species-rich communities have more invasive species than species-poor communities. Thus, patterns of invasion and diversity are scale-dependent. What is different between colonization and invasion? Similarly, it is also well described that invasions can change the structure of the recipient community. However, it is not known if invaders are really better competitors than native species, and in which cases species are lost after invasion or empty niches filled.
Communities are not random assemblages of species. How different the introduced species has to be to change the structure and dynamics of the recipient community? Are there any general "aggressivity" traits that enhance invasion success and do these traits differ depending on the trophic level of invading organisms?
For all these topics, intercrossing between researchers working in different systems (i.e. aquatic, terrestrial, underground) and in different group of organisms (e.g. plants, animals) should have the highest priority.
Discussion Group - Ecology and evolution of indirect effects in ecosystems
Conclusions
Co-chaired by Frank Berendsee and Christer Björkman
One basic question that we asked was “How does evolution affect ecosystems?” based on the fact that species change over time. An interesting consideration here was that species migrate but not ecosystems. We get new assemblages of species. And the change is continuous.
To explore the evolutionary angle further there is a need to search for patterns, both spatial and temporal. When patterns have been revealed there will be a need for experiments and development of theoretical approaches.
There needs to be more focus on the mechanisms involved. It was concluded that most often there are certain species or interactions that are more important than biodiversity per se. Many interactions are rather complex which makes it essential that we have a good naturalistic knowledge.
Evolution is often neglected and the fact that it can be rapid makes it even more important to take it into consideration more often. For example, microevolutionary changes within populations/species may have buffering effects with respect to how species are affected by changes in the ecosystem.
An important but somewhat controversial question that was raised is “At what level does evolution occur?”. Even though individuals seem to be key elements in the evolutionary process it is still possible (and shown) that evolution also operates at higher (and lower) levels. There were plans presented for a workshop that would ask whether or not evolution may occur at the ecosystem level. At that and other workshops, and in research collaborations there is a need to involve population geneticists if we successfully should be able to progress further within this fascinating field of research.
To address evolutionary questions empirically we need to identify one or several model systems that provide the right attributes for experiments and where there is relevant background knowledge available. No really strong candidates were identified but Daphnias, lichens and mykorrhiza were discussed. An agreement about what systems to focus on experimentally would probably enhance the likelihood of increasing our understanding of the role of evolution in ecosystems within a reasonable time period.
Discussion Group - Trophic versus nontrophic interactions in biodiversity research
Conclusions
Co-chaired by Björn Malmqvist and Michael Bonkowski
Summary of the discussion
Even trophic interactions are not easy to tackle. Some simplifications like the functional group concept are often misleading. Looking at indirect effects, clearly strong drivers like ’ecosystem engineers’ exist, but also small indirect effects may add up to significant effects at higher levels. Due to the complexity of the observed effects, e.g. interactions between microorganisms, plants and herbivores, multidisciplinarity is needed in tackling indirect interactions. Including new techniques from different fields may help in uncovering the interaction pathways. Although evidence for their importance is accumulating, indirect effects are mainly neglected by ecological theory. We just became aware of the significance, more fundamental research in this area is needed.
Functional groups or fictional groups?
A part of the discussion focused on the entities of trophic interactions and whether they can be grouped in functional groups. Common consensus was that functional groups are artefacts that aid in structuring our view of interactions. Although useful in certain cases (e.g. designing experiments with plant functional groups) they can be strongly misleading in others (e.g. structure of terrestrial and marine foodwebs as shown by stable isotope analysis). Other points of discussion were whether interaction strength should be considered as a function and how to consider effects of rare species.
How to define indirect effects? Who are the drivers of indirect effects?
Looking at non-trophic interactions what patterns emerge, what is driving them and how can they be grouped? There was a general aggreement that ’ecosystem engineers’ are important drivers of indirect effects. By modifying their own environment they create whole cascades of non-trophic interactions. Apparently many non-trophic interactions exist between below- and aboveground communities. For example earthworms live in their own food-source and shape the structure and function of their soil environment with trophic and non-trophic effects on above-ground foodwebs. Similarly, diatoms in marine habitats are able to change the sediment structure of their habitat with important consequences for other members of the tidal flat community. However, also little changes may add up to big effects. For a single plant even small trade-offs may matter when competing with other plants in a community. Therefore non-trophic interactions creating small trade-offs in single plants may result in changes at the plant community level.
Multidisciplinarity and new techniques
There was a common strong aggreement that a multidisciplinary approach is the best way to uncover and tackle non-trophic interactions. For example, plant ecologists often focus merely on plant traits, microbiologists on microbes and soil ecologists on nutrient cycling although plants microbes and other soil organisms are connected in many direct and indirect ways.
Multidisciplinarity has also the advantage that some disciplines may benefit from new techniques, e.g. using stable isotopes to uncover foodweb relationships or nutrient and energy fluxes, or uncovering indirect responses of plants to herbivores with aid of DNA microarrays.
Lack in ecological theory and more fundamental research needed
Ecological theory is mainly focusing on trophic interactions. However, non-trophic interactions are important and therefore need to be included in ecological theory.
In conclusion, many examples of important non-trophic interactions have been found. Although there is now a general awareness of the importance of non-trophic interactions, we still know very little about the patterns, drivers and mechanisms. More fundamental research is needed in this area.
