Ecologia de comunitats d´invertebrats aquàtics de la Península Ibèrica, amb especial rellevància als Ostracoda

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The ecology of freshwater invertebrates can be dealt with under different scopes. The works presented in this thesis are structured in two different parts. We firstly focus on the interrelationship between the environment and planktonic and benthonic communities which, in shallow water systems (like many of the ones studied here), are usually mixed. In the first work, we studied the seasonal variation of invertebrate aquatic communities of two close mountain ponds (4.5 km apart) with similar climatic conditions but different hydroperiod (Laguna de Bezas, semi-permanent, and Laguna de Rubiales, a temporary pond, both in the Teruel province). In Bezas, a marked shift in the zooplankton structure was observed, firstly dominated by rotifers and then, after a volume reduction, by copepods and benthic cladocerans. In Rubiales, ecological succession is notorious through the sampling campaigns, where a noticeable increment of benthic species is observed when the pond experiments a turbidity shift and an increase of macrophyte coverage. A second chapter focus on the metacommunity analysis of aquatic invertebrates in the Baix Maestrat region, an area that shows a marked environmental gradient and a wide heterogeneity of waterbodies. Studied metacommunities show a dominance of niche effects (environmental adaptations) in all the groups. On the other hand, an absence of spatial effects (due to dispersive constrictions) was found in copepods, rotifers and hemipterans; a factor which nevertheless affected, although with less intensity, to the other groups. In the second part of this thesis, we focused on Ostracoda, and firstly dealt with those species present in streams of high ecological quality. Ninety sites were seasonally sampled in the Iberian Peninsula, and at this larger geographical scale we detected a significant spatial influence on the organization of the metacommunity, constituted by 41 species. However, the environmental effects were not negligible, in particular those related to water chemistry and temperature. In another work on Ostracoda, but now in human-managed water systems, we analized species distribution in reservoirs from the Xúquer River Basin Hydrological Administration. Communities’ structures (22 species found) differ significantly from those of rivers from the same basin. We must note the presence of exotic species in the reservoirs (Fabaeformiscandona subacuta, Candonocypris novaezelandiae), which are seldom found in lotic systems. Finally, we decided to study in detail the distribution of one of the exotic species found in previous samplings: F. subacuta. By sampling the probable area of origin (Japan), and carrying out an exhaustive bibliographical review, together with the analysis of further samples from collections from around the world, we could clarify the synonymy with Fabaeformiscandona japonica and assign a number of doubtful identifications, some of which corresponded to F. holzkampfi. In addition, and from the data obtained, we could conclude that this is a species that, although not usually found at high densities, prefers human-impacted environments, and shows tolerance to ecological disturbances of the ecosystem.
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