AN EXPERIMENTAL ASSESSMENT OF LANDSCAPE CONNECTIVITY

We experimentally assess the relative movement abilities of two sympat ric, ecologically similar species of damselfly, Calopteryx maculata an d Calopteryx aequabilis (Odonata: Calopterygidae), within two structur ally dissimilar habitat types, forest and pasture. For both species, s treams are required resources, forest is a potential resource, and pas ture is neutral habitat. Experimental manipulations were conducted at a spatial scale approaching typical inter-stream distances within our study region. A portion of the individuals was displaced away from its required stream habitat within its native landscape, and the remainin g individuals were transferred to another landscape of alternate habit at structure (either forest or pasture). Within each habitat type we e quate relative movement ability, an essential component of landscape c onnectivity, with the proportion of displaced individuals observed to have reached the stream, as measured against reobservation rates of co ntrol individuals released at the stream. We found that C. maculata, t he species more consistent in its use of forest as a resource, moved s ignificantly more readily through 700 m of pasture habitat than throug h the same distance of forest, while C. aequabilis moved with equal ab ilities through both habitat types. Historical behavior - whether or n ot the individuals typically used forest as a resource before the mani pulations - did not have a statistically significant effect on the mov ement abilities of individuals of either species in either habitat typ e. There was, however, some evidence that C. maculata individuals nati ve to non-forested landscapes moved more readily through forest than t heir forest-inhabiting counterparts. Both sexes moved with equal abili ties irrespective of habitat type, but male C. aequabilis moved with g reater ability through forest than females, while the reverse was true within pasture landscapes.