Intraspecific variability drives diversity in food webs

Biodiversity theories neglect individual-level variability in ecological interactions even though empirical work has revealed considerable genetic and phenotypic variation among individuals in natural populations. This impedes assessing the impact of individual-level variability on biodiversity in multi-trophic ecosystems. Here we use a density-dependent and individual-based food web model, tested against the largest individual-based food web to date, to show that non-random intraspecific variation in prey selection alters species diversity in food webs. Predators consuming many prey increase diversity by preferentially selecting common prey; predators consuming few prey inhibit diversity by preferentially selecting rare prey, putting them at risk of extinction. Thus species-level patterns cannot be explained by species-level averages, but instead must consider individual-level variation in prey selection. Individual-level variation occurs in many biological and social contexts, suggesting that analyses of individual-level interaction data will be relevant in a wide range of fields

Estimación de la diversidad genética y del tamaño efectivo de la población de coquina Donax trunculus del Parque Nacional de Doñana y su contribución a áreas no protegidas

Este capítulo contiene 16 páginas, 4 tablas, 6 figuras.[EN]We have studied seven populations of the wedge clam Donax trunculus, distributed throught the Spanish Atlantic and Mediterranean coasts. A comparative analysis of size and density was performed from a sample obtained from a commercially exploited population from Isla Canela, and from another population which is managed under a strict plan using only artisanal hand dredging from the beach of the Doñana National Park showing that the management carried out in the Doñana National Park is correct and allows sustainable fisheries. Twenty one microsatellite loci were isolated and characterized in D. trunculus of which 16 were polymorphic and codominant. At least 12 of them have high frequencies of null alleles in all populations, and the rest in most populations. All collected samples were genotyped with these 16 loci and genetic diversity indices, tests of disequiibrium, fixation indices and probabilities of genetic differentiation among localities were determined. The odds of assignment to the sampling location were also determined. Several analyses were conducted to determine the potential causes for the deviations from Hardy-Weinberg equilibrium which shown that they were mainly due to the presence of null alleles. Furthermore, using the ribosomal internal transcribed spacer it was determined that the commercially exploited populations of the wedge clam under the specific name Donax trunculus are actually a mixture of a hybrid and non-hybrid species. The analysis of the genetic structure made both to all individuals and separately for hybrid and non-hybrid individuals showed four genetically distinct populations in the Spanish coast. The first in the Cantabric Sea, the second in the Gulf of Cadiz, the third from the Strait of Gibraltar to Cabo de Gata and the last one from the Cabo de Gata to the Gulf of Rosas.[ES]Se han estudiado ejemplares de coquina, Donax trunculus en 7 localidades distribuidas por las costas peninsulares atlánticas y mediterráneas españolas. Se ha hecho un análisis comparado de datos de tallas y densidad obtenidos en una localidad explotada (Isla Canela) y otra protegida (playa del Parque Nacional de Doñana), que muestran que la gestión llevada a cabo en el Parque Nacional Doñana es la correcta y permite una pesca sostenible. Se aislaron y caracterizaron 21 loci de microsatélites de los cuales 16 resultaron polimórficos y codominantes. De ellos al menos 12 presentan elevadas frecuencias de alelos nulos en todas las poblaciones, y el resto en la mayoría de poblaciones. Todas las muestras fueron genotipadas con estos 16 loci y se determinaron los índices de diversidad genética, pruebas de equilibrio, índices de fijación y las probabilidades de diferenciación entre localidades. También se determinaron las probabilidades de asignación a la localidad de muestreo. Se realizaron diversos análisis para determinar las causas potenciales de las desviaciones del equilibrio de Hardy-Weinberg y se demostró que se deben principalmente a alelos nulos. Se descubrió mediante el análisis del marcador ribosomal ITS que las poblaciones de coquina explotadas comercialmente en España bajo la denominación específica Donax trunculus son en realidad una mezcla de una especie híbrida y una no híbrida. El análisis de la estructura genética, tanto el realizado a todos los individuos como de forma separada para individuos híbridos y no-híbridos, demostró que existen cuatro poblaciones genéticamente distintas en el litoral español. La primera en el Mar Cantábrico, la segunda en el Golfo de Cádiz, la tercera entre el Estrecho de Gibraltar y el Cabo de Gata y la última entre el Cabo de Gata y el Golfo de Rosas.Queremos agradecer en primer lugar al Organismo Autónomo Parques Nacionales por la concesión del proyecto que permitió el presente estudio. A la oficina de coordinación del Parque Nacional de Doñana por las facilidades prestadas para los muestreos en la playa de Doñana. Nuestro agradecimiento también a Consejería de Agricultura, Pesca y Desarrollo Rural de la Junta de Andalucía por compartir sus datos sobre la densidad de coquinas en el Golfo de Cádiz y facilitar los permisos de pesca en los diferentes puntos de Andalucía. Y como no, gracias también a los mariscadores y pescadores de Sanlú- car de Barrameda (Cádiz) y de Cabo de Gata (Almería) que nos acompañaron en los diferentes muestreos.Peer reviewe

Molecular phylogeny of the genera Palaemon and Palaemonetes (Decapoda, Caridea, Palaemonidae) from a European perspective

A molecular phylogenetic study by Murphy & Austin (2003) showed that Australian representatives of three shrimp genera of the family Palaemonidae (Palaemon, Palaemonetes, and Macrobrachium) do not cluster according to their generic classification. According to their results, the monophyly of these genera is questioned and the generic classification of the subfamily Palaemoninae is at stake. A large number of representatives of Palaemon and Palaemonetes inhabit European waters, including the type species of each genus. To clarify the phylogeny of these species, and thus the position of the generic names Palaemon and Palaemonetes on a phylogenetic tree, we obtained DNA sequences of the same genetic markers (16S mtDNA) as used by Murphy & Austin (2003) and re-addressed the question of taxonomy and phylogeny of these two genera within the subfamily Palaemoninae. Our results confirm the paraphyly of Palaemon and Palaemonetes. In contrast, the resulting monophyletic clades reflect the geographic distribution of the species according to their respective continents: Africa-Europe, Asia, Australia, and America. With the exception of Palaemon elegans the Afro-European species cluster in a way that would support monophyly of the two genera, if representatives from other continents are excluded. Possible taxonomic solutions are discussed.Research was partly funded by the postdoctoral grant from “Ministerio de Educación Cultura y Deporte” (Spain), and a Research contract “Ramón y Cajal” from “Ministerio de Ciencia y Tecnología” (Spain) to J.A.C.Peer Reviewe

Null alleles are ubiquitous at microsatellite loci in the Wedge Clam (Donax trunculus)

Recent studies have reported an unusually high frequency of nonamplifying alleles at microsatellite loci in bivalves. Null alleles have been associated with heterozygous deficits in many studies. While several studies have tested for its presence using different analytical tools, few have empirically tested for its consequences in estimating population structure and differentiation. We characterised 16 newly developed microsatellite loci and show that null alleles are ubiquitous in the wedge clam, Donax trunculus. We carried out several tests to demonstrate that the large heterozygous deficits observed in the newly characterised loci were most likely due to null alleles. We tested the robustness of microsatellite genotyping for population assignment by showing that well-recognised biogeographic regions of the south Atlantic and south Mediterranean coast of Spain harbour genetically different populations

Environmental and anthropogenic drivers affect the abundance of anchovy and mysids in the Guadalquivir Estuary (SW Spain)

Natural drivers, acting at various spatio-temporal scales firstly determine the distribution and abundance of species. On top of this natural forcing we usually find anthropogenic effects. Disentangling the relative influence of these two sources of variability has always been a challenge in ecology, and particularly in fisheries science. The Guadalquivir Estuary (SW Spain) serves as nursery ground for several commercial species in the Gulf of Cadiz. This study aims at quantifying the relative influence of biological (predator-prey effects), environmental (e.g. temperature, winds) and anthropogenic (dam discharges) effects on this nursery function with the focus on an important species, anchovy. We used data from a monitoring programme consisting of monthly records since 1997 at two sites: Tarfia (32 km) and Bonanza (8 km) (distance from the river mouth). Nonparametric models (GAM) were fit to the data to estimate the partial effects of the various covariates. We found positive and linear effects of temperature and mysids on anchovy abundance in both stations, while turbidity, winds and freshwater input had a negative effect, reducing fish abundance. A dam, 110 km upstream from the Guadalquivir mouth regulates freshwater discharges, directly influencing the estuarine habitat quality and extent, as captured by our models. In order to separate the anthropogenic effects from natural variability we further ran the models on a number of scenarios combining a range of dam discharges and environmental conditions. Water management stands out as a key node where potentially conflicting interests (irrigators, electric power, shipping, aquaculture, fisheries) converge. By focussing on the consequences that the effects of these activities ultimately have on the anchovy fishery, through this nursery function, our study aims to contribute to the process of making the ecosystem approach operational in the Gulf of Cadiz

The nursery role of the Guadalquivir estuary for marine fish. A long-term ecological research

Trabajo presentado en el 23rd Biennial CERF Conference (Grand challenges in coastal and Estuarine Science: securin our future), celebrado en Portland (Oregón, US) del 8 al 12 de noviembre de 2015.N

Multidecadal (1997-2020) telecoupling of water management for terrestrial agriculture and a marine fishery at southern Spain

Climate change is decreasing water supplies globally while water demand is rising, making water access and distribution essential for sustainability, equity, and efficiency. In response, water management has shifted towards practices that improve water efficiency. However, links between geographically separated socioecological systems, known as telecouplings, can obscure the potential consequences of water use. This study focuses on a telecoupling between terrestrial water use and marine fisheries for the period 1997 to 2020. We develop a case study in southern Spain using multidecadal time series of the Guadalquivir river’s hydrology, its estuarine community, and the European anchovy (Engraulis encrasicolus) fishery in the Gulf of Cadiz. We found that water extracted to irrigate crops decreased the river’s flow and seasonality. However, anchovies used the estuary as a nursery before recruiting to the ocean, where they were harvested. Anchovy recruitment improved when estuary hydrology matched the Guadalquivir River’s historical hydrology (i.e., high discharge and seasonality). Then using hydro-economic modeling, we explored the outcomes of different water policies on the telecoupled socioecological systems. Our models predicted that improved water efficiency incentivized agricultural expansion. In contrast, continued marine fishery yields required management values that supported the value of the marine fishery. We highlight estuaries’ critical role in driving marine systems; yet, upriver processes drive estuaries dynamics. Overall, marine-terrestrial telecouplings provide evidence that marine fisheries that rely on estuarine reliant species would benefit of water policy and management being extended beyond the water basin

Population dynamic and trophic position of mysid community demonstrates its key role for nursery function in a temperate estuary

Guadalquivir Estuary is a main nursery ground of marine goal species for Gulf of Cadiz fisheries. It is a well-mixed temperate estuary with horizontal salinity gradient and clear seasonal water temperature trend. Mysid community with Mesopodopsis slabberi, Neomysis integer and Rhopalophthalmus tartessicus make up to over 80% of total macrofauna biomass in the estuary. Life history, population structure, secondary production, trophic level and community spatio-temporal dynamic were unravelled combining analysis of long term 16y monitoring data with 2y of in depth population analysis and trophic biomarker studies. Results show a key trophic role in food web, a seasonal trend showing density peaks ( 23, 3 and 6 mg/m3, respectively) in spring-summer and winter marine coastward migration. Despite being euryhaline, the three species of showed unevenly spatial distribution, being salinity the variable best explaining structure changes of mysid assemblage. Inter- and intra-specific euryhalinity differences both for prey and predators seem to determine the entire spatial estuarine community distribution. High secondary production (P/B rates 38.2, 10.3 and 10.7) and food web studies confirm key role of mysids transferring energy up to juveniles (fish and crustaceans) arriving yearly in spring to their nursery area

Distribution and salinity tolerance of the invasive isopod Synidotea laticauda in the Guadalquivir estuary (SW Spain): Field and laboratory observations

Trabajo presentado en ECSA 56 (Coastal systems in transition: From a 'natural' to an 'anthropogenically-modified' state), celebrado en Bremen del 4 al 7 de septiembre de 2016.The effects of the exotic species in native communities are unpredictable and ecological studies should be required for environmental management. In Europe, the exotic species Synidotea laticauda has been introduced in several estuaries but there was not any previous biological study about these non-native populations. The spatio-temporal field distribution of S. laticauda in the last 30 km of the Guadalquivir estuary (salinities 0 to 30) was assessed during 7 years (August 1997-June 2004) by sampling at each new moon with a mesh size net of 1 mm. Survival and osmoregulatory patterns of the species under different experimental salinity conditions were also estimated. This exotic species is a permanent resident of the estuary, with presence of juveniles and adults during most of the year, but showing maximum densities in the warmest period (summer to early autumn). Spatial patterns were closely related to the salinity gradient: the highest densities were observed between 10 and 30 of salinity, with a maximum at 20 (≈ isosmotic point). In fact, the isopod is a weak osmoregulator, which maintains the osmolality of the hemolymph partially independent of the medium osmolality (in a salinity range of 5 to 25). Moreover, survival experiments showed a high tolerance (mortality < 30%) to sudden salinity changes between 2 and 35 and virtually no mortality in salinities (15-25) close to the isosmotic point (20). Osmoregulatory and survival patterns were not dependent on sex but they seemed to be specific-dependent on salinity acclimation. Although it is a euryhaline species, its weak osmoregulatory capacity explains its salinity-dependent distribution pattern. Our results provide a framework to predict the distribution of this invasive species under sceneries of climate change and consequent freshwater scarcity.N

Long-term ecological research of aquatic ecosystem at Guadalquivir estuary (1997-2014): community structure and food web

A long term ecological research program (LTER) is developed monthly at the Guadalquivir estuary since 1997. Inter- and intra-specific euryhalinity differences both in prey and predators seem to determine spatial species distribution at this important nursery area: the less euryhaline species (marine recruits) tends to occur at physiologically more favourable salinities (lower osmotic stress and mortality risk); whereas most euryhaline species (estuarine species) occurred at ecologically more favourable salinities (lower inter-specific competition and predation). Likewise, inter-specific differences in spawning periods cause certain temporal segregation of those marine recruits using the estuary. High spatiotemporal coincidence of prey (mainly mysids and copepods) density peaks with that of their predators suggests food availability as a key factor in the estuarine nursery function. According to their distribution, the estuarine stretch situated seaward from the 5 isohaline position is mainly used as a nursery ground, principally during warm period (T > 15 °C). Thus, human management of the freshwater input to the estuary (from a 110 km upstream dam) modifies the nursery ground extent due to seaward/upstream displacements of the estuarine salinity gradient. During droughts, this freshwater control may also lead to a partial loss of the estuarine nursery function due to a decrease of prey availability linked to extremely high-turbidity events