Mediterranean River Basin Research Articles

Invasibility Patterns of Knotgrass (Paspalum distichum) in Portuguese Riparian Habitats

Spatial patterns of the exotic riverine knotgrass (Paspalum distichum L.) were examined in Mediterranean river basins in Southwestern Iberia. The major goals of this study were to assess the degree of invasibility of riparian habitats by this species and to determine the influence of environmental factors and human-induced disturbances that this knotgrass has on both the landscape and the habitat scales. The present study demonstrates the ability of knotgrass to invade riparian habitats in Portuguese freshwater ecosystems. However, most of the spatial variation of the knotgrass cover seemed to be driven by local factors, such as fine sediment enrichment and the fragmentation of riparian woods, and by other anthropogenic interferences in relation to both the fluvial system and the surrounding landscape.

Summer habitat relationships of barbels in south‐west Spain

An analysis was made of the associations with local habitat features of barbels (Barbus sp.) of a Mediterranean river basin. The analysis was based on the presence data from sampling the upper, middle, and lower reaches of 31 rivers in the middle Guadiana River basin (south‐west Spain). Numerous local habitat variables were determined, including the river's size and substratum, physicochemical variables of water, and the aquatic and riparian vegetation. For each species, a univariate analysis was performed using preference indices, and logistic regression was used to construct a parsimonious multivariate model and Gaussian response models with the most influential variables, quantifying the species’ limits of tolerance. Distinct habitat associations for every species were obtained, mainly relating Barbus comiza to the larger habitats and higher water levels, Barbus microcephalus to the maintenance of lotic conditions and Barbus sclateri to more fluctuating rivers. Barbus steindachneri showed a different habitat relationship from that of the genetically almost identical B. comiza. Cover played a significant role in all but B. comiza.

Ecological and historical filters constraining spatial caddisfly distribution in Mediterranean rivers.

Summary1. Contemporary species distributions are determined by a mixture of ecological and historical filters acting on several spatial and temporal scales. Mediterranean climate areas are one of the world's biodiversity hotspots with a high level of endemicity, which is linked to complex ecological and historical factors.2. This paper explores the ecological and historical factors constraining the distribution of caddisfly species on a large regional scale. A total of 69 taxa were collected from 140 sampling sites in 10 Iberian Mediterranean river basins. Approximately 74% of taxa can be considered rare, with the southern basins (the Baetic–Riffian region) having greater endemicity. The greatest richness, involving a mixture of northern and southern species, was found in the transitional area between the Baetic–Riffian region and the Hesperic Massif.3. The historical processes occurring during the Tertiary (i.e. the junction of the Eurasian and African plates) explained 3.1% of species distribution, whereas ecological factors accounted for 20.7%. Only 0.3% was explained by the interaction of history and ecology. A set of multi‐scale ecological variables (i.e. basin, reach and bedform characteristics) defined five river types with specific caddisfly assemblages. The commonest caddisfly species accounted for the regional distribution pattern, while rare taxa contributed to the explanation of subtle patterns not shown by common species.4. Despite the importance of historical factors for biogeography and the large scale used in our study, ecological variables better explained caddisfly distribution. This may be explained by the length of time since the historical process we are considering, the high dispersion and colonisation capacity of many caddisfly species, and the strong environmental gradient in the area. Because of the historical and environmental complexity of Mediterranean areas, rare taxa should be included in ecological studies so that the singularity of these ecosystems is not missed.

Comparing pharmaceutical and pesticide loads into a small Mediterranean river

During 2003/2004, water samples were collected upstream and downstream of two wastewater treatment plant (WWTP) outlets in order to determine the contribution of urban centres to concentration of selected pharmaceuticals (antiphlogistics, lipid regulators and carbamazepine) and pesticides into a Mediterranean river basin (Arc river, Aix en Provence, France). Pharmaceutical loads were compared to pesticide ones. They could be nearly regarded as important as pesticide ones at least at one sampling site. The observed pollution patterns differed from pesticides to pharmaceuticals. Pesticide pollution occurred through a high pollution peak in spring while pharmaceuticals were continuously infused into the river via WWTP effluents. Carbamazepine and bezafibrate were detected in almost all samples at concentration levels ranging from ng/L to μg/L. The major pharmaceutical source could be ascribed to WWTP effluents and pharmaceutical concentrations increased during low flow rate conditions (summer), when municipal wastewater effluents accounted for the majority of the river water flow. Treated wastewaters contributed to a lesser extent to pesticide river water pollution. In an urbanized Mediterranean river basin, a deep understanding of water pollution by organic waste contaminants is required in order to set up an efficient programme of pollution reduction measures.

Historical biogeography of Mediterranean trout

Complete sequencing of the mitochondrial control region was used to describe phylogenetic relationships of brown trout populations ( Salmo trutta) in the Mediterranean river basins of Iberia and to review the historical biogeography of trout from the Mediterranean regions. Phylogenetic relationships among trout lineages suggested that the Danubian one is the most ancestral, in accordance with the eastern origin of most of the European freshwater fish species. Nested-clade and mismatch analyses suggested that the present distribution of haplotypes of the Adriatic and Mediterranean lineages resulted from population expansions originated, respectively, from central and western Europe, which favoured extensive secondary contacts between lineages. Reduced diversity detected within 50% of the analysed populations and large intrabasin differentiation indicated restricted gene flow in post-glacial periods.

Fish fauna in Iberian Mediterranean river basins: biodiversity, introduced species and damming impacts

Abstract A basin approximation was used to analyse distribution patterns of different components of biodiversity (taxonomic richness, endemicity, taxonomic singularity, rarity) and conservation status of freshwater fish fauna in 27 Mediterranean Iberian rivers. Basin area alone explained more than 80% of variation in native species richness. Larger basins featured not only a higher number of native species, but also more endemic and rare species and fewer diversified genera than smaller basins. In contrast, smaller basins scored higher community conservation values, owing to their lower degree of invasion by introduced species. The presence of dams was the most important factor determining the conservation status of fish communities, and it was also positively associated with the number of introduced species. While the most important components of Iberian freshwater fish biodiversity are located in large basins, small unregulated basins feature better conserved fish communities. Copyright © 2004 John Wiley & Sons, Ltd.

Trichoptera (Insecta) collected in Mediterranean river basins of the Iberian Peninsula: taxonomic remarks and notes on ecology

As a result of the GUADALMED project, undertaken in Iberian Mediterranean basins, to which were added samples taken by the junior author in the area, we collected numerous caddisfly larvae, pupae and adults. Some larvae were also reared in the lab to obtain adults and allow proper identification. A total of 90 species were identified, which accounts for more than a fourth of the species known in the Iberian Peninsula and Balearic Islands. Here we confirm the presence of doubtful species in the Iberian Peninsula (Glyphotaelius pellucidus) and we expand the distribution range of others (Lype reducta, Micrasema minimum, Limnephilus guadarramicus, Sericostoma pyrenaicum). Moreover, because of the unconformity of morphological larval characteristics with present taxonomical keys (Mesophylax aspersus) or lack of larvae descriptions (Allogamus mortoni, Stenophylax espanioli), here we include some relevant taxonomical aspects that are useful to identify larvae. A brief description of the larva of a possible new species of Hydropsyche (from now on H. gr. instabilis) is also given.

Neutral sugars as biomarkers in the particulate organic matter of a French Mediterranean river

Neutral sugars (arabinose, glucose, galactose, fucose, mannose, rhamnose, xylose and lyxose) in riverine POM and adjacent soil samples were analysed by gas chromatography over a period of 18 months in a small Mediterranean river basin. Total neutral sugars or TCHO, and individual neutral sugar abundance were highly variable, with TCHO yields varying from 0.04 to 94 mgTCHO/100 mgOC and concentrations from 0.04 to 78 μg/l. The most abundant neutral sugars were arabinose (ARA) in riverine POM and fucose (FUC) in soil samples. Temporal fluctuations in relative neutral sugar abundance (wt.%) and ratios indicated a mainly allochthonous and transformed POM source during autumn and winter while the dry season (from Dec-97 to Jul-98) was characterised by a fresher, phytoplanktonic component. Comparison of %FUC+RHA, %GLU, %GLU+GAL and (FUC+RHA)/(ARA+XYL) ratios with other parameters such as chlorophyll a and lignin-phenols enhanced the conclusions concerning the neutral sugar sources (terrestrial and phytoplanktonic) of riverine POM.

Distribution Patterns, Species Assemblages and Habitat Selection of the Stoneflies (Plecoptera) from Two Mediterranean River Basins in Southern Spain

AbstractThe stonefly distribution and its relationship with habitat changes, based on stream physico chemical features, were investigated in two Mediterranean river basins (Guadaira and Guadalete, S Spain). Plecopteran nymph distribution varied along an elevation gradient. Both stonefly species richness and species diversity increased with altitude. Stoneflies were able to tolerate a wide range of environmental conditions but were absent from low altitude sites, temporary streams with high salinity values and high water temperature. A total of 13 stonefly species were found in the study area, from which Tyrrhenoleuctra minuta (Klapálek) and Protonemura sp. were dominant. The most widespread species were Nemoura lacustris and Capnioneura mitis. Three distinct species assemblages were observed according to their distribution patterns, but with similar environmental preferences. Capnioneura petitpierreae and T. minuta showed preferences to low altitude sites, whereas C. mitis and N. lacustris were found throughout all sites. T. minuta and N. lacustris inhabited permanent and temporary sites, while the same species and C. mitis also were found in semipermanent streams. Temporally, most stoneflies were caught during winter (85.9%), especially at the low altitude sites.

Spatio‐Temporal Distribution and Ecological Preferences of Coexisting Hydropsychid Species (Trichoptera) in Two Mediterranean River Basins (S Spain)

AbstractThe hydropsychids of two Mediterranean river basins in southern Spain (Guadaira and Guadalete) were investigated from January 1988 to January 1989. The distribution of hydropsychids along an environmental gradient related to altitude varied depending on species. Two distinct species assemblages were observed. one located in the lower altitude sites (the “downstream assemblage” comprising Hydropsyche pictetorum, Hydropsyche exocellata and Cheumatopsyche lepida) and the other in the upper‐most areas (the “upstream assemblage” comprising Hydropsyche punica, Hydropsyche infernalis, Hydropsyche instabilis), which displayed a statistically significant preference for this type of habitat. Finally, H. pictetorum, selected the lowest sites. From a temporal point of view most species displayed a high variability in density dynamics between sites, suggesting a strong plasticity in life‐cycle phenology.

The Influence of Environmental Factors and Microhabitat Availability on the Distribution of an Aquatic Oligochaete Assemblage in a Mediterranean River Basin

AbstractSome aquatic oligochaete species, mainly certain naidids and tubificids, are often associated with polluted environments, with high levels of organic matter and oxygen deficit. However, in the stations sampled in the Guadaira river basin, which can be arranged on an axis of organic pollution, the main aquatic oligochaete species (Nais elinguis and Tubifex tubifex) inhabiting these environments do not show a distribution pattern significantly related to the water physico‐chemical characteristics measured. Nor, have we registered any association between these species and any kind of microhabitat, defined here: water current, presence of different types of vegetation, substrate coarseness and presence of anoxic sediments. Paranais litoralis is the exception, being related to areas without water current, located at higher altitudes, with high levels of dissolved organic matter and an anoxic substrate made up of fine particles.These results can be explained by the highly fluctuating nature of Mediterranean ecosystems and by the marked generalist character and ubiquity of the oligochaete assemblage species, able to colonize any kind of environment.

Encrusting algal assemblages in a Mediterranean river basin

Encrusting algal assemblages in a Mediterranean river basin