OTROS ESTUDIOS

There is widespread concern about the global decline of amphibians, but little is known about whether and how direct human disturbance might affect populations. The goal of this study was to assess the effects of recreational activities on Iberian frogs Rana iberica, an endemic and vulnerable species of the Iberian Peninsula, through observation and manipulative approaches. At the population level, we found that frog abundance decreased with the proximity to recreational areas. At the individual level, the behavioral responses of frogs to repeated disturbance events increased the time to resume pre-disturbance activities, but did not affect significantly flight initiation distances. We simulated different levels of human visitation to the stream banks, and found 80% and 100% decrease in stream bank use with a fivefold and a 12-fold increase in direct disturbance rate, respectively.

Recreational activities are negatively affecting Iberian frogs through a loss in the spatial and temporal availability of resources. To reduce the level of local disturbance to this species, we recommend setting up buffer areas >2.5 m from the streams or reducing visitor rates to fewer than 5 visits per hour (either groups or individuals). The role of direct human disturbance should be considered further as a potential factor affecting local amphibian declines.

Studies examining the effects of anthropogenic habitat fragmentation on both neutral and adaptive genetic variability are still scarce. We compared tadpole fitness‐related traits (viz. survival probability and body size) among populations of the common frog (Rana temporaria) from fragmented (F) and continuous (C) habitats that differed significantly in population sizes (C > F) and genetic diversity (C > F) in neutral genetic markers. Using data from common garden experiments, we found a significant positive relationship between the mean values of the fitness related traits and the amount of microsatellite variation in a given population. While genetic differentiation in neutral marker loci (FST) tended to be more pronounced in the fragmented than in the continuous habitat, genetic differentiation in quantitative traits (QST) exceeded that in neutral marker traits in the continuous habitat (i.e. QST > FST), but not in the fragmented habitat (i.e. QST ≈ FST). These results suggest that the impact of random genetic drift relative to natural selection was higher in the fragmented landscape where populations were small, and had lower genetic diversity and fitness as compared to populations in the more continuous landscape. The findings highlight the potential importance of habitat fragmentation in impairing future adaptive potential of natural populations.

In 1993-1994, larvae and imagines of Odonata were collected in 10 arms of the river Danube. Odonata larvae were also collected during the hydrobiological research of the Morava river basin in 1990-1993.

Following the method of hierarchical classification, based on the presence of dragonfly species at selected localities, we distinguished the characteristic biotopes, as follows: 1) lentic biotopes renewed and newly formed, with undercurrents and rippling inhabited by rheophilous dragonflies, Calopteryx splendens, Platycnemis pennipes and the pioneer species, Anax imperator; 2) drying, unstable, euthrophic biotopes are inhabited by the coenosis Lestes-Sympetrum sp.; 3) original stagnant waters inhabited by the ceonosis Orthetrum-Libellula depressa and Erythromma-Anax imperator; 4) original localities with larger areas inhabited by the coenosis Lestes-Sympetrum-Aeshna sp.; 5) lotic biotopes of the river Rudava with the coenosis Cordulegaster-Ophiogomphus cecilia, comprising the rare species, Ophiogomphus cecilia.

El objetivo del trabajo es describir las relaciones entre los tipos de hábitat, las condiciones físico-químicas del agua y la riqueza en las comunidades de invertebrados no artrópodos de agua dulce (macro y microespecies). Se sondearon 74 ecosistemas oligotróficos de montaña (ríos, arroyos, lagos, lagunas, embalses y turberas) en seis subcuencas del noroeste de la Península Ibérica incluidas en Natura2000. Se realizó un muestreo multihábitat en todos los ambientes (aguas abiertas, bentos, musgos y líquenes en rocas, troncos de árboles y hojarasca sumergida) para comprobar los patrones de biodiversidad en lugares someros.
Se caracterizó la selección de hábitat de 27 taxones de invertebrados no artrópodos (INA) pertenecientes a 6 Filos. La cercanía a las zonas de nacientes, con litologías gruesas en los fondos y aguas oligotrofas y de escasa mineralización, propician un reducido nivel trófico, lo que supone unas comunidades bióticas pobres y una limitada productividad de estos lugares. El ecosistema más rico en especies fue el lago de Sanabria. La presencia preferente de taxones propios de condiciones oligosaprobias y especialistas en baja mineralización avala su empleo en la monitorización de calidad del agua y la presencia de especies invasoras únicamente en tramos bajos refleja el papel de refugio de biota autóctona que cumplen las montañas.

Se describe la presencia de cuatro taxones de hidras de agua dulce (Cnidaria, Hydrozoa: Hydridae) en zonas someras epicontinentales de la cuenca del Duero (NO de España). En la subcuenca del Tera se encontraron individuos aislados sobre macrófitos sumergidos de tres taxones: Hydra vulgaris Pallas, 1766, Hydra (Pelmatohydra) oligactis Pallas, 1766 e Hydra (Chlorohydra) viridissima Pallas, 1766, y además en el Carrión grupos coloniales sobre bloques de cuarcita de la forma H. vulgaris var. aurantiaca Ehrenberg, 1838. En todos los casos se corresponde con ecosistemas de media montaña de aguas frías, transparentes y oligotróficas, de pH ligeramente ácido y con escasa mineralización. Todas las especies fueron localizadas en simpatría estricta, aunque en el lago de Sanabria se pudo citar tres taxones en diferentes hábitats. Se documenta la predación en cautividad de H. oligactis sobre gusanos oligoquetos y los periodos de formación de pólipos por gemación.

During the summer of 2005, a survey was carried out in 71 lakes and ponds of the Duero basin. Thirty nine of those pools had water during the sampling survey, in twenty six sites, thirty two hydrophyte species considered by the IH index were collected. It was observed that: 1) hydrophyte species differed in their optimum growth along a stress gradient calculated from different variables and field observations; 2) the most influent variables regarding the presence of macrophytes in a water body were the hydroperiod and the anthropogenic disturbances related to agricultural and livestock activities; 3) the best ecological quality systems were those located at higher altitudes, with cold and low mineral content waters and with less anthropogenic disturbances; 4) the majority of the localities were poorly conserved, in comparison with previous studies and, finally, 5) many of the studied systems, even with some kind of protection, had lost the categories proposed by Cirujano et al. (1992): wetland with “singular interest”, wetland with “national” or with “European significance”.

With the main goal of investigate the charophyte diversity changes over a period of 20 years, an extensive survey of lakes and ponds of the Duero basin was conducted during the summer of 2005. The results were then compared with those obtained by Alonso & Comelles during a decade (1977-86). Out of the 39 visited water bodies that contained water in 2005, only 14 hosted 10 taxa of charophytes: 8 belonging to the genus Chara and 2 to the genus Nitella. Unlike previous studies, all the water bodies examined in 2005 were highly affected by anthropogenic disturbances. However, no significant differences between sites with or without charophytes were found for any of the studied ecological variables. This suggests that charophytes can adapt to a wide range of habitat conditions, and highlights the need to preserve and maintain the previous heterogeneous nature of the visited water bodies. Moreover, a reduction in charophyte species richness was noted over time. This may have been due to the increasing effect of anthropogenic disturbances, which were mostly related to agricultural and livestock farming activities and alter the water quality of the ecosystems as well as the charophyte flora they harbour.

Se realiza por primera vez un catálogo de Bacillariophyceae para los ríos del NW de España. Se incluyen un nuevo examen de los táxones recogidos en publicaciones anteriores, datos de táxones citados durante los últimos años de los ríos de la demarcación hidrográfica de Galicia-Costa y una revisión de la taxonomía, en consonancia con los cambios sistemáticos y nomenclaturales, que se han producido sobre todo durante los últimos años. Se estudiaron las diatomeas epilíticas de las cuencas de los ríos de Galicia-Costa entre los años 2005, 2006 y 2007, durante dos temporadas diferentes: mayo-junio y septiembre. El estudio se llevó a cabo en 41 localidades distribuidas a lo largo de 31 ríos, donde se tomaron muestras en tramos aguas arriba y aguas abajo. Las comunidades de diatomeas de estos ríos que drenan de sustratos silíceos fueron comparadas en todos los tramos de aguas arriba. Se identificaron 141 táxones de diatomeas de la costa de Galicia. En este trabajo presentamos 15 nuevas citas para Galicia, dos para España y tres para la Península Ibérica, además de una nueva especie recientemente descrita. Los táxones dominantes son: Achnanthidium minutissimum, Achnanthes subhudsonis, Karayevia oblongella, Cocconeis placentula var. euglypta, Gomphonema rhombicum, y Navicula minima. Achnanthes subhudsonis fue la especie más abundante durante los meses de primavera y verano. Las especies restantes no mostraron cambios pertinentes independientemente de la época del año. Los resultados indican que las diatomeas de los ríos de Galicia son un componente importante de la diversidad del ecosistema.

Invasive macrophyte Myriophyllum aquaticum is capable of assimilating nutrients from both the sediments and the water column. However, which is the major source of nutrients supporting M. aquaticum growth under various nutrient regimes has not been well documented. Here we conducted a two factorial outdoor experiment (three levels of nutrient loading and two types of sediments) from 23 May to 27 June 2016, to assess M. aquaticum responses to different nutrient levels in the water column and the sediment. Results showed that concentrations of total nitrogen, total phosphorus and chlorophyll a in the water column increased in the treatment groups, but decreased slightly in the control group (nutrient-poor sediment and no nutrient addition). Sediment type had a significant effect on the growth M. aquaticum, while there were no significant effects of nutrient loading levels and the interactions between the two factors. Mean relative growth rate, mean plant height, mean stem diameter, the number of lateral branches and roots in the nutrient-rich sediment treatments were 1.6, 1.2, 1.6, 3.2 and 5.9 folds greater than in the nutrient-poor sediment treatments, respectively. These results suggest that nutrient-rich sediment has a positive effect on the growth of M. aquaticum. This study reveals possible expansion mechanism of the exotic M. aquaticum in China, and may provide valuable information on the ecological restoration of eutrophic freshwaters.