<p>Dispersal is an important factor in animal ecology. Anurans (frogs and toads) are often philopatric (home loving) but some specimens in a population usually have the capacity to disperse relatively long distances. In this study I investigated the colonization of newly constructed ponds in the southwest of Sweden by three anuran species: The common toad (Bufo bufo), the moor frog (Rana arvalis) and the common frog (Rana temporaria). The ponds were constructed between two and five years ago and were now as frequently occupied as older source ponds in the area. For the common toad and the common frog there was no correlation between distance to source populations and degree of colonization. The moor frog was more common in ponds that were situated in the vicinity of older source ponds with ample populations. The main impression was that these species rapidly colonize newly constructed ponds, at least within moderate distances from source populations. There were some differences between the species though and it seems like the moor frog have more limited dispersal abilities than the other two species.</p>

Dispersal is an important factor in animal ecology. Anurans (frogs and toads) are often philopatric (home loving) but some specimens in a population usually have the capacity to disperse relatively long distances. In this study I investigated the colonization of newly constructed ponds in the southwest of Sweden by three anuran species: The common toad (Bufo bufo), the moor frog (Rana arvalis) and the common frog (Rana temporaria). The ponds were constructed between two and five years ago and were now as frequently occupied as older source ponds in the area. For the common toad and the common frog there was no correlation between distance to source populations and degree of colonization. The moor frog was more common in ponds that were situated in the vicinity of older source ponds with ample populations. The main impression was that these species rapidly colonize newly constructed ponds, at least within moderate distances from source populations. There were some differences between the species though and it seems like the moor frog have more limited dispersal abilities than the other two species.

Batrachochytrium dendrobatidis (Bd) is a fungus that causes chytridiomycosis in amphibians. This fungus is an invasive species that has spread all over the world and is causing mass deaths in many areas. Bd has an efficient life cycle which targets suitable hosts and causes disturbances in amphibian osmoregulation and eventually death. It has caused more than 90 presumed extinctions worldwide. However, even though this fungus is commonly found in Sweden, no cases of chytridiomycosis has been found in the wild. This raises the questions i) what factors makes the infection in amphibians more severe and ii) does temperature affect the severity of Bd infection? According to the thermal mismatch hypothesis pathogens should be more efficient at temperatures where the performance gap between the host and pathogen is the widest. We chose the common toad as a study organism since it can be found all over Sweden and is generally considered to be adapted to colder climates. Our aim was to test the thermal mismatch hypothesis and see if the effect of infection differed between different temperatures. Common toad eggs were collected from two ponds in southern Sweden, raised in the laboratory and metamorphosed juvenile toads were reared in three different temperature rooms, either 14℃, 18℃ or 22℃. There they were either infected with Bd or exposed to a sham infection and monitored for 40 days. We show that Bd infection negatively affects growth and survival of common toads in accordance with previous studies. Furthermore, we found that temperature affects the effect of infection and shows patterns of the thermal mismatch hypothesis.