Resource-based habitat: concept and applications

ELIB

Habitat is a key concept for ecology and conservation. General habitat or land-use types can be useful to study distribution patterns of animals at coarse-grained spatial scales, but they typically do not capture the functional spatial resolution at which organisms interact with their environment. Therefore we explore a resource-based habitat approach (connecting the concept of habitat back to the ecological niche) instead of using general vegetation types or biotopes as surrogates for a species’ habitat (see Dennis, R.L.H., Shreeve, T.G. & Van Dyck, H. 2003. Oikos 102: 417-426).

We apply this resource-based approach in a series of studies with butterflies and birds.

1.    Resource-based habitat-use, behaviour and conservation of peatbog and heathland butterflies

We have applied, and further explore, the use of a bottom-up resource-based concept to delineate habitat. This approach explicitly takes into account functional relationships between species and essential resources and/or conditions in their environment rather than using general vegetation types as surrogates for a species’ habitat. We developed a procedure to map butterfly habitat from such a perspective for heathland butterflies of regional conservation concern. This tool is, for example, used in the National Park Hoge Kempen.  We also used the approach for testing the degree of transferability among nature reserves of habitat models to predict the distribution of heathland butterflies (e.g. Hipparchia semele, Callophrys rubi, Satyrium ilicis).

Peatbog butterflies are also species of conservation concern. Moreover, several can be considered glacial relict species (e.g. Boloria aquilonaris) and a detailed understanding of their habitat-use will be essential to guide their conservation in the era of climate change. We study in detail adult and larval resource-use and what it signifies for the conservation of these rare species. This study allows us to incorporate the resource-based habitat approach into behavioural ecology (e.g., effect of male territorial behaviour on female resource-use in Lycaena hippothoe), thermal ecology (e.g. the significance of microclimate buffering for caterpillars of Boloria aquilonaris) and classic ecology (e.g. interspecific niche overlap between peatbog butterflies).   

2.    Nectar offer, use and consequences in different agricultural landscapes

Nectar is a key resource for several insects, including butterflies. We study how nectar quantity, quality and configuration at the landscape level differ between traditionally managed agricultural landscapes and intensively managed agricultural landscapes. We, for example, aim to develop a kind of nectar-index to compare this aspect of habitat quality among landscapes. We also analyze what such differences may mean for nectar-consumers. Therefore, this study is not only done in the field, but we also perform laboratory experiments to measure the effect of quantitatively and qualitatively different nectar intake on life history traits like fecundity and survival (e.g. with the Meadow brown butterfly Maniola jurtina).

3.    Red-backed shrikes in agricultural vs woodland landscape

In the south of Belgium, the red-backed shrike (Lanius collurio) is considered a typical bird of agricultural landscapes with meadows and hedgerows. However, the species has recently also colonized forest gaps that resulted from altered forestry. We study resource availability (i.e. insect prey items) in both types of landscape relative to reproductive success of the shrikes (e.g. trade-offs between number and condition of offspring). To understand the presence and abundance of different insects, several thermal aspects of the vegetation are studied as well. We particularly test the hypothesis that forest gaps in this region would be ecological and evolutionary traps.  

For this project we collaborate with Dr. Nicolas Titeux, a former lab member who currently is at the Gabriel Lippmann Research Centre (Luxembourg).