boy nature

This research project is led by Jason M. Tylianakis

The importance of species interactions in ecosystem functioning

Summary

My research concentrates on the effects of human changes to the environment on biodiversity, species interactions and ecosystem processes. I am particularly interested in how species traits and the local environment jointly shape the structure of interaction networks such as food webs, and how this structure affects processes at the entire community level. I also study the conditions under which biodiversity is most important for maintaining ecosystem functioning and services, and how best to manage the functional capability of ecosystems.

The Challenge

Humans are driving an unprecedented number of simultaneous changes to the environment. These changes are driving extinctions of species, altering their distributions, and disrupting their interactions. My research group uses a variety of experimental and observational approaches to try to understand how environmental effects on communities alter the functioning of the ecosystems.

Insights

We have examined a broad suite of species interactions, and found few general patterns in how different species and their interactions respond to different kinds of environmental change. Therefore, we focus on multispecies networks of interactions as a framework for determining whole-community changes and incorporating emergent properties of interaction-network structure. We frequently use interaction networks as replicated units for hypothesis testing, and have found changes to food webs that cannot be predicted simply by changes to biodiversity. These changes include alteration of the average structure, as well as homogenization of interactions in space and time. We have also found that the position of interactions in networks can determine their likelihood of going extinct.

Our group has examined the context in which biodiversity is important for ecosystem functioning. Much research has shown a positive effect of biodiversity on the rates of different functions/processes, though this relationship is by no means ubiquitous. It is also difficult to reconcile these positive diversity effects with the reality that many of our most productive systems contain low species diversity (e.g. plantation forests, pastures). We are therefore working on trying to understand the conditions under which biodiversity has greater or lesser impacts on ecosystem processes, and we have shown that drivers of biodiversity loss (such as land-use change) can directly alter ecosystem functioning in ways that overshadow the positive effects of biodiversity – at least in the short term. We have also found that biodiversity has its greatest impact on ecosystem functioning when the available resources are heterogeneous and thereby allow greater niche partitioning.

Impact

Our work has underscored the importance of species interactions as a component of biodiversity that is vulnerable to environmental change. It has shown that the structure of species interaction networks can be altered in unpredictable ways, and that these changes can affect ecosystem functioning.

The Future

We are currently quantifying the impacts of land-use intensification on adjacent native ecosystems, and working on ways to minimise those impacts. These impacts can occur in a number of ways, for example, nutrient flows, movement of organisms, or indirect interactions between species in each habitat. In contrast, movement of organisms from native to productive habitats can be beneficial for agriculture, so we are interested in understanding the landscape configurations that minimise harmful spillover from production to natural systems, while maximising the benefits to production from ecosystem service providers in native habitats.

Previously, we have found that pollinator and natural enemy diversity can, respectively, enhance rates of pollination and natural pest control in agricultural systems. We are currently working on landscape-scale approaches to manage these ecosystem service providers, and determining the conditions (e.g. crop types) under which their diversity will be most important. It is imperative that any such strategies for managing biodiversity in agricultural landscapes do not carry high opportunity costs for landowners, so we are looking for 'win-win' scenarios.

Finally, we are examining the importance of species traits and phylogenetic relatedness for the structuring of species interaction networks.

Funders and Sponsors

Our work is currently funded by the Marsden Fund of New Zealand, NERC, The Ministry of Business, Innovation and Employment (NZ), The Royal Society of New Zealand, and the Miss E.L. Hellaby Indigenous Grasslands Research Trust.