<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.

In meiner Dissertation untersuche ich das Paarungs- und Fortpflanzungsverhalten des Europäischen Grasfrosches (Rana temporaria) in einem evolutionären Kontext. Mein Ziel ist es zu verstehen, welche Mechanismen zur Bildung von Paaren führen, ob die Partnerwahl die Paarungsmuster erklärt, die wir beobachten können, und ob es evolutive Vorteile gibt, die sich aus der Paarung mit einem bestimmten Partner ergeben. Die Suche nach und die Konkurrenz um Paarungspartner führt zur Entwicklung verschiedener Paarungssysteme, Strategien und Taktiken, um den Reproduktionserfolg während der gesamten Lebensdauer zu erhöhen. Das Paarungsverhalten wird durch natürliche und sexuelle Selektion beeinflusst, wobei beide in unterschiedliche Richtungen wirken können. Für die meisten Individuen ist das Überleben unerlässlich, um sich so oft wie möglich zu reproduzieren, und dadurch die reproduktive Gesamtfitness zu erhöhen. Andererseits könnte ein auffälliges Verhalten bei der Fortpflanzung das Prädationsrisiko erhöhen. Der Akt der Paarung selbst kann bereits mit Risiken verbunden sein, welche sich auf die Überlebensraten auswirken können. Durch sexuelle Selektion könnten bestimmte sekundäre Geschlechtsmerkmale begünstigt werden, entweder aufgrund von Vorteilen im Wettbewerb innerhalb eines Geschlechts (intrasexuell), oder aufgrund spezifischer Präferenzen zwischen den Geschlechtern (intersexuelle Selektion). Damit sich die Partnerwahl entwickeln kann, muss der gewählte Paarungspartner Vorteile aufweisen, von denen der wählende Partner profitiert, denn die Wahl ist mit energetischen Kosten und zeitlichem Aufwand verbunden. Als Frühlaicher muss der Europäische Grasfrosch mit einem eingeschränktem Paarungszeitraum umgehen. Die Männchen konkurrieren um den Zugang zu Weibchen und es wird angenommen, dass sich Weibchen während der Paarung und Reproduktion passiv verhalten, da der hohe "Männchen-Überschuss" keine Wahl zulassen würde. Aus evolutionärer Sicht sollten Weibchen jedoch das wählerische Geschlecht sein und entscheiden mit wem sie sich paaren, da sie mehr Energie in die Eierproduktion investieren. / In my thesis, I examine the mating and reproductive behaviour of the European Common Frog (Rana temporaria) in an evolutionary context. I aim to understand which mechanisms lead to the formation of pairs, if mate choice shapes the patterns of mating that we can observe and if there are benefits derived from pairing with a specific mate. The search and competition for mating partners lead to the evolution of various mating systems, strategies and tactics to increase lifetime reproductive success. The mating behaviour is influenced by natural and sexual selection, whereby both could act in different directions. For most individuals, survival is essential in order to reproduce as often as possible to increase lifetime reproductive fitness. On the other hand, reproduction could increase predation risk due to conspicuous behaviour and risks associated with mating itself. Sexual selection could favour specific secondary sexual traits, either due to advantages in intrasexual competition, or by specific preferences of the choosy sex (intersexual selection). For mate choice to evolve, there need to be benefits associated with the chosen mating partner, because choosiness involves costs in terms of energy and time constraints during mating. As an explosive breeder, the European Common Frog has to deal with time constraints during the short breeding season. The males are competing for the access to females and it is assumed that females are passive during breeding due to a high male-biased operational sex ratio. However, from an evolutionary perspective females should be the choosy sex and should decide with whom to mate, as they invest more energy into the production of eggs.