Iberian Freshwater Research Articles

Inter-population plasticity in dietary traits of invasive bleakAlburnus alburnus(Linnaeus, 1758) in Iberian fresh waters

Inter-population plasticity in dietary traits of invasive bleak<i>Alburnus alburnus</i>(Linnaeus, 1758) in Iberian fresh waters

Cenozoic tectonic and climatic events in southern Iberian Peninsula: Implications for the evolutionary history of freshwater fish of the genus Squalius (Actinopterygii, Cyprinidae)

Southern Iberian freshwater ecosystems located at the border between the European and African plates represent a tectonically complex region spanning several geological ages, from the uplifting of the Betic Mountains in the Serravalian–Tortonian periods to the present. This area has also been subjected to the influence of changing climate conditions since the Middle–Upper Pliocene when seasonal weather patterns were established. Consequently, the ichthyofauna of southern Iberia is an interesting model system for analyzing the influence of Cenozoic tectonic and climatic events on its evolutionary history. The cyprinids Squalius malacitanus and Squalius pyrenaicus are allopatrically distributed in southern Iberia and their evolutionary history may have been defined by Cenozoic tectonic and climatic events. We analyzed MT-CYB (510 specimens) and RAG1 (140 specimens) genes of both species to reconstruct phylogenetic relationships and to estimate divergence times and ancestral distribution ranges of the species and their populations. We also assessed their levels of genetic structure and diversity as well as the amount of gene flow between populations. To investigate recent paleogeographical and climatic factors in southern Iberia, we modeled changes-through-time in sea level from the LGM to the present. Phylogenetic, geographic and population structure analyses revealed two well-supported species (S. malacitanus and S. pyrenaicus) in southern Iberia and two subclades (Atlantic and Mediterranean) within S. malacitanus. The origin of S. malacitanus and the separation of its Atlantic and Mediterranean populations occurred during the Serravalian–Tortonian and Miocene–Pliocene periods, respectively. These divergence events occurred in the Middle Pliocene and Pleistocene in S. pyrenaicus. In both species, Atlantic basins possessed populations with higher genetic diversity than Mediterranean, which may be explained by the Janda Lagoon. The isolation of S. malacitanus was earlier and related to the rising of the Betic Mountains. Divergence of its Atlantic and Mediterranean populations was associated with the creation of the freshwater systems of southern Iberia close to the Gibraltar Strait. The presence of S. pyrenaicus in southern Iberia may be the result of recent colonization associated with river capture, as demonstrated our biogeographic reconstruction.

How well do protected area networks support taxonomic and functional diversity in non-target taxa? The case of Iberian freshwaters

Protected area networks represent one of the mainstays of global conservation polices and are therefore central to current efforts to maintain biodiversity. However, a major limitation of most conservation strategies is their bias towards particular taxonomic groups and ecosystems, meaning that many taxa and habitats are often only incidentally protected as a by-product of inclusion within reserves. Here we investigate how effectively protected area networks, not specifically designated for freshwaters, support aquatic biodiversity in the Iberian Peninsula (Spain and Portugal), using data for water beetles, surrogates of overall macroinvertebrate diversity in these habitats. We explore the behaviour of different measures (α, β and γ) of both taxonomic and functional diversity at different spatial scales. Overall our findings highlight the contrasting performance of reserve systems in the maintenance of either taxonomic or functional diversity, as well as the importance of spatial scale. Iberian reserves perform relatively well in supporting taxonomic diversity of water beetles at the peninsular scale, but the same protected areas poorly represent functional diversity. Such a mismatch cautions against the use of any one diversity component as a surrogate for others, and emphasizes the importance of adopting an integrative approach to biodiversity conservation in aquatic ecosystems. Furthermore, our results often show contrasting patterns at smaller spatial scales, highlighting the need to consider the influence of scale when evaluating the effectiveness of protected area networks.

Interspecific Aggressive Behaviour of Invasive Pumpkinseed Lepomis gibbosus in Iberian Fresh Waters

Pumpkinseed Lepomis gibbosus (L.) are successful invaders in Europe, where this species exerts multiple ecological effects, mainly through trophic interactions. Behavioural interference represents a potential impact for native fauna and this is of particular conservation concern in the Iberian Peninsula because of the highly valuable endemic fauna inhabiting streams of this region. However, aggressive interactions have not previously been examined under natural conditions in Iberian fresh waters. To address this gap in knowledge, the aim of the present study was to assess the effect of pumpkinseed aggression on endemic fauna of an Iberian stream, the River Bullaque (central Spain). In September 2009, we analysed the aggression and environmental contexts of these behavioural interactions by snorkelling: aggressor size, aggression type, shoal size, previous activity to aggression, recipient species, response to aggression, microhabitat structure and prey availability. Small pumpkinseed displayed more threat and fewer pursuit behaviours relative to medium and large individuals, reflecting an ontogenetic behavioural shift from low to high aggression intensity. Small aggressors came from large shoals, with bottom feeding being the most frequently observed activity prior to an aggressive interaction; whereas large pumpkinseed were less gregarious and they were mostly ambulating within the water column prior to aggression. Recipient species of aggression included non-native crayfish and fishes, and more importantly, endemic fishes and frogs. Retreat was the most common response to aggression, irrespective of aggressor size. Small pumpkinseed displayed aggressive behaviours over coarse substrata containing elevated macrobenthos biomass; whereas aggression by large individuals was observed in deeper waters. These findings suggest that small and large pumpkinseed exert a high impact on other stream residents through aggression in competition for food and territory defence, respectively. This study highlights the usefulness of direct observations in the wild for assessing the effects of behavioural interference of invasive fishes on Iberian aquatic communities.

EFFECTS OF FLOW REGULATION AND NON‐NATIVE SPECIES ON FEEDING HABITS OF EURASIAN OTTER Lutra lutra IN MEDITERRANEAN TEMPORARY RIVERS

ABSTRACTIn Mediterranean temporary rivers, ecological resources greatly fluctuate because of the high hydrological variability throughout the year. However, flow regulation prevents this natural regime and commonly entails associated non‐native species, which change the structure of aquatic communities. Nonetheless, few studies have tested the interaction of these two disruptive factors (flow regulation and non‐native species) and their synergistic effects on the Eurasian otter (Lutra lutra) diet at the river scale. The aim of this study was to compare the seasonal feeding habits of the otter between a temporary non‐regulated stretch and two regulated stretches invaded by non‐native species in a Mediterranean water course. The Bullaque River (Guadiana River Basin, central Spain) was seasonally sampled for otter spraints and prey abundance assessed from December 2009 to November 2010. Three stretches were considered: high (source, non‐regulated), medium (transition, regulated) and low (confluence, regulated). Diet varied from native prey in the high stretch (amphibians, insects and endemic cyprinids) to non‐native species in the low stretch (red‐swamp crayfish Procambarus clarkii and pumpkinseed sunfish Lepomis gibbosus). Seasonally, ingested biomass of native prey increased in spring. Diet was more diverse in the high stretch. Otters neutrally selected native cyprinids in the high stretch throughout the year, whereas crayfish was selected in the other two stretches. Overall results showed that flow regulation and non‐native species have increased prey availability for the otter; however, this paper highlights the importance of maintaining natural regimes in Mediterranean temporary rivers to conserve native communities and thus minimally impact food webs in Iberian freshwaters. Copyright © 2014 John Wiley &amp; Sons, Ltd.

Population traits of invasive bleak Alburnus alburnus between different habitats in Iberian fresh waters

The bleak Alburnus alburnus (L.) is a cyprinid native to most of Europe, mainly inhabiting lentic environments. This fish species is a successful invader in the Iberian Peninsula, where it was first introduced to reservoirs as forage fish during the 1990s. Bleaks threaten the highly endemic Iberian fish fauna by means of trophic competition and hybridization. Yet, little is known about the environmental biology of bleaks in the Iberian Peninsula, particularly far from impounded waters. Thus, the aim of this work was to compare seasonal and gender variation of size structure, body condition and reproductive investment of bleaks between different habitats. Only sexually mature bleaks were seasonally collected and examined from the River Gévora and the Sierra Brava Reservoir (southwestern Spain) to assess more in-depth the adaptive capacity at the population level and the subsequent invasiveness. Bleak was an abundant species in the fish assemblages of both habitat types (i.e. river and reservoir). The proportion of smaller mature bleaks was lower in the river than the reservoir during spring and the opposite pattern was observed during winter. Both male and females were larger in the river during the breeding season in the study areas (i.e. spring), as well as with higher body condition and reproductive investment. These findings suggest that bleaks enhance their reproduction rate in the river to compensate for higher mortality in this habitat, where environmental conditions may be harsher due to the winter floods and summer droughts typical of Mediterranean water courses. Overall results highlight the high degree of plasticity in population traits of the bleak in the Iberian Peninsula, which will surely aid its ability to adapt to a wide variety of Mediterranean ecosystems, including lentic and lotic environments. Consequently, this invasive fish may pose a serious risk for the highly valuable fauna of Mediterranean Europe.

Diet of the introduced pikeperch Sander lucioperca (L.) (Osteichthyes, Percidae) in a recent colonised reservoir in south-western Iberian Peninsula

The present study examines the diet of pikeperch (Sander lucioperca) in Iberian freshwaters. Food habits of Sander lucioperca were studied based on stomach content analyses of 376 specimens (12.22–52.52 cm total length) collected in 2009 on a south-western Iberian reservoir. A total of 265 stomachs (79.52%) contained food, and fifteen taxonomic levels of prey were identified. The most important prey was fish according to the Relative Importance Index (IRI). Trophic level analysis revealed that S. lucioperca is a top predator throughout its life history. There were no differences between sexes (p = 0.573, ANOSIM) and seasons (p = 0.266) in the diet composition, but minor dietary shifts with ontogeny were found. The Levins' standardized index indicated wider niche breadth for small pikeperch, whereas larger pikeperch specimens showed a narrow niche breadth with a specialization in congeners. The graphical analysis (Amundsen method) of the diet confirmed that pikeperch feed mainly on congeners in Alcántara reservoir; however some native species were also consumed.

Population divergence with or without admixture: selecting models using an ABC approach

Genetic data have been widely used to reconstruct the demographic history of populations, including the estimation of migration rates, divergence times and relative admixture contribution from different populations. Recently, increasing interest has been given to the ability of genetic data to distinguish alternative models. One of the issues that has plagued this kind of inference is that ancestral shared polymorphism is often difficult to separate from admixture or gene flow. Here, we applied an approximate Bayesian computation (ABC) approach to select the model that best fits microsatellite data among alternative splitting and admixture models. We performed a simulation study and showed that with reasonably large data sets (20 loci) it is possible to identify with a high level of accuracy the model that generated the data. This suggests that it is possible to distinguish genetic patterns due to past admixture events from those due to shared polymorphism (population split without admixture). We then apply this approach to microsatellite data from an endangered and endemic Iberian freshwater fish species, in which a clustering analysis suggested that one of the populations could be admixed. In contrast, our results suggest that the observed genetic patterns are better explained by a population split model without admixture.

Impacts of non-native fishes on Iberian freshwater ichthyofauna: current knowledge and gaps

The Iberian Peninsula contains a highly endemic freshwater ichthyofauna that is being homogenized and threatened by an increasing number of non-native fishes. Here, in this paper, I reviewed the literature on the impacts of fish introductions and translocations on the native Iberian ichthyofauna. The aims of the present review were (1) to provide an overview of the already studied and proven impacts as well as of the suggested potential impacts that remain to be tested, (2) to synthesize the current knowledge in the Iberian Peninsula and (3) to suggest future research approaches. Despite some well-documented impacts, an increasing number of non-native fish species and a wide range of diverse ecological situations uncover knowledge gaps which hamper conservation and management efforts. Since the introduction of species is often pointed out as a major cause of extinctions, I encourage research groups and funding agencies to devote more resources to the study of interactions between nonnative and native fishes in order to develop evidence-based species-specific impact assessments.

Biogeography of Iberian freshwater fishes revisited: the roles of historical versus contemporary constraints

AbstractAim The question of how much of the shared geographical distribution of biota is due to environmental vs. historical constraints remains unanswered. The aim of this paper is to disentangle the contribution of historical vs. contemporary factors to the distribution of freshwater fish species. In addition, it illustrates how quantifying the contribution of each type of factor improves the classification of biogeographical provinces.Location Iberian Peninsula, south‐western Europe (c. 581,000 km2).Methods We used the most comprehensive data on native fish distributions for the Iberian Peninsula, compiled from Portuguese and Spanish sources on a 20‐km grid‐cell resolution. Overall, 58 species were analysed after being categorized into three groups according to their ability to disperse through saltwater: (1) species strictly intolerant of saltwater (primary species); (2) species partially tolerant of saltwater, making limited incursions into saltwaters (secondary species); and (3) saltwater‐tolerant species that migrate back and forth from sea to freshwaters or have invaded freshwaters recently (peripheral species). Distance‐based multivariate analyses were used to test the role of historical (basin formation) vs. contemporary environmental (climate) conditions in explaining current patterns of native fish assemblage composition. Cluster analyses were performed to explore species co‐occurrence patterns and redefine biogeographical provinces based on the distributions of fishes.Results River basin boundaries were better at segregating species composition for all species groups than contemporary climate variables. This historical signal was especially evident for primary and secondary freshwater fishes. Eleven biogeographical provinces were delineated. Basins flowing to the Atlantic Ocean north of the Tagus Basin and those flowing to the Mediterranean Sea north of the Mijares Basin were the most dissimilar group. Primary and secondary freshwater species had higher province fidelity than peripheral species.Main conclusions The results support the hypothesis that historical factors exert greater constraints on native freshwater fish assemblages in the Iberian Peninsula than do current environmental factors. After examining patterns of assemblage variation across space, as evidenced by the biogeographical provinces, we discuss the likely dispersal and speciation events that underlie these patterns.

Threats to the conservation of biotic integrity in Iberian fluvial ecosystems

Fluvial ecosystems are highly modified by human activity and the species inhabiting them are more imperiled than their aerial or oceanic counterparts. In addition, freshwater biodiversity per surface unit is higher than terrestrial and marine biodiversity. But from a conservation point of view rivers and streams have received less attention than any other natural system. Impacts in water and habitat quality, flow regime and biotic interactions can be considered the main factors responsible for the lack of biotic integrity in Mediterranean rivers. Dams and impoundments alter rastically the physical habitat structure and the ecological unctioning of running waters. But at the same time also modify the flow regime. Biotic interactions are deeply altered by introduced invasive species, which are common and proliferate in eservoirs and other artificial lentic habitats. In this paper we have adapted this classification of the main human impacts on fluvial ecosystems to the Iberian situation summarising them in three groups: water pollution, damming, and introduction of invasive species. We discuss their effects on biotic integrity of running waters through some examples from some of our previous works. Pollution is treated in two alternative ways. Quantifying its importance in the drainage network of a large Mediterranean area in southern Spain, as well as analysing its effect on the structure of macroinvertebrate communities and otter (Lutra lutra) distribution. Invasive species are widespread in Iberian inland waters. We hereby present the spatial relationship between native fish communities and invasive centrarchids that populate the peninsula. Finally, the damming impacts are considered through the analysis of its role in the spread and establishment of the invasive species. All of them are just a few examples about how alterated is the natural composition and dynamics of Iberian rivers and streams, i.e. its biotic integrity. The challenge for the future lies in the efficient protection of the biodiversity of Iberian freshwaters in the face of increasing pressures on the aquatic resources. But the first step in preserving our rivers is the real recognition of the extent of the problem, particularly among scientists.

Evolution in action through hybridisation and polyploidy in an Iberian freshwater fish: a genetic review.

The Iberian minnow Leuciscus alburnoides represents a complex of diploid and polyploid forms with altered modes of reproduction. In the present paper, we review the recent data on the origin, reproductive modes, and inter-relationships of the various forms of the complex, in order to predict its evolutionary potential. The complex follows the hybrid-origin model suggested for most other asexual vertebrates. Diploid and triploid females from the southern river basins exhibit reproductive modes that cannot be conveniently placed into the categories generally recognised for these vertebrate complexes, which imply continuous shifting between forms, where genomes derived from both parental ancestors are cyclically lost, gained or replaced. Replacement of nuclear genomes allow the introduction of novel genetic material, that may compensate for the disadvantages of asexual reproduction. Contrasting with most other vertebrate complexes, L. alburnoides males are fertile and play an important role in the dynamics of the complex. Moreover, diploid hybrid males may have initiated a tetraploidization process, when a diploid clonal sperm fertilised a diploid egg. This direct route to tetraploidy by originating fish with the right constitution for normal meiosis (symmetric), may eventually lead to a new sexually reproducing polyploid species. This case-study reinforces the significance of hybridisation and polyploidy in evolution and diversification of vertebrates.