Ecología de los cangrejos de rio en tramos de montaña. Interacción con la comunidad de macroinvertebrados y algas epilíticas

Abstract

The white clawed-crayfish, Austropotamobius italicus, is an emblematic inhabitant of the Iberian Peninsula. It was well widespread over most of drain basins in the past, but habitat destruction and exotic species-mediated diseases put it at risk of extinction during last decades. Nowadays, remnant populations seem to be restricted to headwaters and small tributaries, consequently having a high conservation value. Crayfish are generally recognized as omnivores, displaying an opportunistic foraging behavior on steam biota. Among these organisms, one of the most important groups of primary producers is constituted by epilithon, represented by those algae colonizing the rocky surfaces of bedstreams. Furthermore, macroinvertebrates usually are the main consumers in benthic food webs, as they play a main role in energy flows between producers and higher level consumers, among which crayfish are included. This PhD study aimed to improve understanding of some of the issues related with crayfish ecology by examining abiotic factors conditioning the white-clawed crayfish distribution and interactions between this species and the benthic communities from headwaters. Both approaches were carried in two neighbour limestone areas located at the Iberian Range. On one hand, a field survey employing different sampling techniques was conducted within the irrigation net of Alto Tajo Natural Park, in order to determine the area covered by A. italicus and the main habitat features governing its distribution. On the other hand, a permanent mountain stream located at Serranía de Cuenca Natural Park was selected to appropriately assess the effects of crayfish on macroinvertebrate and epilithic algae compartments through two different mesocosm-based experiments involving increasing densities of crayfish. Additionally, a parallel study just involving the interaction of an exotic species, the signal crayfish Pacifastacus leniusculus, with epilithon, was made. The combined use of diurnal, nocturnal, capture and indirect survey techniques allowed the characterization of a relatively high number of small populations. The only variables showing significant differences between crayfish inhabited and non-inhabited locations were those related with altitude, as supported by a wide tolerance range for specific physicochemical and habitat features...