Papers by Gustavo Llorente
Ethology Ecology & Evolution, Jul 1, 2019
Animal Biodiversity and Conservation
The Common Toad Bufo bufo is the amphibian with the highest rates of road mortality in many Europ... more The Common Toad Bufo bufo is the amphibian with the highest rates of road mortality in many European countries. This elevated incidence of road kills has frequently been associated with migration to breeding sites. In this study, we analysed the mortality of the Common Toad in the road network in Catalonia (NE Spain), and investigated the related causative factors on four roads near a breeding site in the Pyrenees. Results suggest that the high mortality rate is due to a combination of factors: toad abundance, traffic density and quality of water bodies for breeding. On the road with the highest incidence of road kills we investigated whether deaths occurred at specific spots or in a random manner. The road was divided into 500 m sections and each section was classified according to biotic (type of vegetation) and abiotic (presence of streams, roadside topography) variables. Multiple correspondence analysis showed that sections with streams crossing under the road had the highest mo...
PLOS ONE, 2015
One of the critical factors for understanding the establishment, success and potential impact on ... more One of the critical factors for understanding the establishment, success and potential impact on native species of an introduced species is a thorough knowledge of how these species manage trophic resources. Two main trophic strategies for resource acquisition have been described: competition and opportunism. In the present study our objective was to identify the main trophic strategies of the non-native amphibian Discoglossus pictus and its potential trophic impact on the native amphibian Bufo calamita. We determine whether D. pictus exploits similar trophic resources to those exploited by the native B. calamita (competition hypothesis) or alternative resources (opportunistic hypothesis). To this end, we analyzed the stable isotope values of nitrogen and carbon in larvae of both species, in natural ponds and in controlled laboratory conditions. The similarity of the δ 15 N and δ 13 C values in the two species coupled with isotopic signal variation according to pond conditions and niche partitioning when they co-occurred indicated dietary competition. Additionally, the non-native species was located at higher levels of trophic niches than the native species and B. calamita suffered an increase in its standard ellipse area when it shared ponds with D. pictus. These results suggest niche displacement of B. calamita to non-preferred resources and greater competitive capacity of D. pictus in field conditions. Moreover, D. pictus showed a broader niche than the native species in all conditions, indicating increased capacity to exploit the diversity of resources; this may indirectly favor its invasiveness. Despite the limitations of this study (derived from potential variability in pond isotopic signals), the results support previous experimental studies. All the studies indicate that D. pictus competes with B. calamita for trophic resources with potential negative effects on the fitness of the latter.
One of the critical factors explaining the success of invasive species and their effect on native... more One of the critical factors explaining the success of invasive species and their effect on native species is to know how they manage the trophic resources. Two main trophic pathways have been suggested to explain resource acquisition by invasive species: invasive species can may behave aggressively over the resources exploited by natives, displacing them from their niches (competition hypothesis), or they may exploit niche opportunities that most native species are unable to use efficiently (opportunism hypothesis). In Europe, painted frog (Discoglossus pictus) is one of the few introduced species of amphibians that is currently expanding. This species shows high overlap in the breeding habitat with one native species, the toad Bufo calamita. The aim of the present study was to determine how the two species manage trophic resources when coexist in the same habitat and the potential effects of the invasive on the native species. To corroborate previous findings obtained under laborat...
Pond breeding amphibian metacommunity structure: the importance of trade-offs Amphibian species l... more Pond breeding amphibian metacommunity structure: the importance of trade-offs Amphibian species living in lentic freshwater habitats exist along a gradient from ephemeral to permanent ponds. Community structure and distributions of species across the gradient have been explained by three principal ecological models, all them based on different tradeoffs and inherent properties of the species. One model assumes that patterns of occurrence can be understood in terms of metapopulation models, closely connected to ideas about fugitive or pioneer species and trade-offs between colonization and competition abilities. The other two models assert that a gradient in pond permanence is the main cause of community structure. One argues for a pond permanence-competition trade-off, whereas the other opts for species tolerance to predators across the hydroperiod (permanence-predation trade-off). We measured in-field distribution of species across the gradient and tadpole and predator abundances in different habitats. Using field surveys and laboratory experiments we examined the different traits suggested by the models in order to asses the relative role of each model in explaining community structure. Species distribution, tadpole abundance and predation risk across the hydroperiod gradient were in concordance with previous studies. Correlations among traits reflected trade-offs suggested by the models, whereas a test of equality of correlation coefficients does not favour any single trade-off model over the others. These results suggest that this community can be interpreted as a metacommunity in which local interactions (pond permanence, predation risk and competition) and regional processes (colonization-extinction rates) are important and related, and they emphasize the importance of habitat heterogeneity for both local and regional diversity maintenance.
Animal Biology, 2007
Several life-history traits may increase vulnerability of species to extinction. Among snakes, am... more Several life-history traits may increase vulnerability of species to extinction. Among snakes, ambush predation and dietary specialisation are factors that increase this vulnerability. European viper species, genus Vipera, display such traits and are categorised as endangered in several parts of its range. For their conservation management, a deeper knowledge of their ecology and habitat use is highly relevant. One of the species with less ecological data is the Lataste's viper Vipera latastei, a species which lives in the Iberian Peninsula and northwestern Africa. Here, we describe its diet based on the analysis of gut content of 435 museum specimens plus nine bibliographic data from the entire Iberian range. The species showed seasonal and ontogenetic shift in diet but no sexual variations. Feeding activity (percentage of vipers with prey) was low in accordance with its ambush predation tactics, being lower in spring than in summer and autumn. Prey spectrum included two main (reptiles and small mammals), and three sporadic, types of prey (arthropods, amphibians and birds). The consumption of reptiles and mammals was seasonal; the former decreased in occurrence from spring to autumn, whereas the latter showed an opposite pattern. There was an ontogenetic shift in the diet: juveniles fed mainly on reptiles and arthropods, whereas adult vipers progressively substitute this prey with insectivores, and the largest vipers primarily foraged on rodents and birds. Our results suggest that the seasonal variation in prey type was related to prey availability, whereas the ontogenetic shift was linked to gape limitation. The apparently wide prey spectrum of V. latastei must therefore be examined, taking into account that there are seasonal and ontogenetic dietary variations as well as geographic differences, the latter probably driven by climatic contrasts into the Iberian Peninsula. This new data of the endangered Iberian V. latastei can aid the effective conservation management of this species.
Revista española de Documentación Científica, 2001
The reptile populations in Montseny Natural Park. Distribution and monitoring
Oikos, 2004
Experimental manipulations of the densities of two larval anurans, Pelodytes punctatus and Bufo b... more Experimental manipulations of the densities of two larval anurans, Pelodytes punctatus and Bufo bufo, showed that these species compete asymmetrically in semi‐natural conditions. Growth, mass at metamorphosis, date of metamorphosis, and survival were used as measures of response to interspecific competition. A mechanistic approach was used to collect information on the behaviour of the two species in different conditions. The competitive superiority of Pelodytes at individual level was correlated with a larger body, faster growth rate, increased per capita competitive impact on conspecifics, and greater reduction in the availability of trophic and spatial resources. In the presence of Pelodytes, Bufo showed slower growth, smaller size at metamorphosis and reduced survival. In the interspecific treatments Bufo individuals modified their behaviour by increasing activity and use of the water column while Pelodytes did not change their foraging activity or space use in the aquaria. Howe...
Folia Parasitologica, 2000
The helminths infesting the common lizard, Zootoca vivipara (Jacquin, 1787), were studied with sp... more The helminths infesting the common lizard, Zootoca vivipara (Jacquin, 1787), were studied with special attention to the relations between the number of nematodes, Oswaldocruzia filiformis (Goeze,1782), and the size, sex and age class of the host. The possible seasonality of the parasite intensity and the relationship with the feeding habits of the host were also tested. Helminth infracommunities of Z. vivipara were depauperate with lizards harbouring only two species, the trematode Plagiorchis molini (Lent et Freitas, 1940) and the nematode O. filiformis. A positive correlation between host size and the number of O. filiformis was found for female Z. vivipara. However, no correlation was detected between intensity and sex or age class. The feeding habits of Z. vivipara, the isolation of the population studied and the low level of interaction with other reptilian or amphibian species are suggested as the causes of the depauperate helminth infracommunities found in this lacertid lizard.
Ecography, 2000
... carp Cyprinus earpio. Conversely, viperine snakes rejected the mosquito fish Gambusia holbrok... more ... carp Cyprinus earpio. Conversely, viperine snakes rejected the mosquito fish Gambusia holbroki whieh is the most abundant species in autumn, when Natrixmaura has a low feeding activity. Statistical comparisons between ...
Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology, 2008
Ectotherm vertebrates show physiological mechanisms that reduce metabolic costs during prolonged ... more Ectotherm vertebrates show physiological mechanisms that reduce metabolic costs during prolonged fasting. Once feeding, these animals adopt a wide variety of metabolic responses such as changes in gastrointestinal organ masses. Up-regulatory responses after feeding have been widely explored in infrequently feeding snakes like pythons, whereas few studies have been devoted to frequently feeding snakes. In this study, we have considered the gastrointestinal responses after feeding in a frequent feeder, the viperine snake Natrix maura, in the Ebro Delta rice fields. In this habitat, viperine snakes are exposed to long periods of food deprivation due to the lack of available prey as a consequence of the man-induced rice cycle. We weighed prey items and full gut masses, and measured length of combined esophagus and stomach, and intestine of viperine snakes belonging to a wide range of sizes. Snakes concentrate foraging activity when rice fields were flooded. In this period, gut masses increased. Likewise, intestines increased in length during the feeding period, which suggests that viperine snakes probably experience a postfeeding hypertrophy of their small intestines that contributes to their larger length. Once the intestine length was corrected for the snake size, it was shown that adults present longer intestines than immature snakes, reflecting an increase in the posterior part of the body linked to the gonads development. This study contributes to explore the physiological responses to feeding in frequently feeding snakes modelled by abrupt shifts of food availability.
Biological Journal of the Linnean Society, 2010
Sexual dimorphism in body size and shape in animals is normally linked to sexual selection mechan... more Sexual dimorphism in body size and shape in animals is normally linked to sexual selection mechanisms that modify the morphological properties of each sex. However, sexual dimorphism of ecologically relevant traits may be amplified by natural selection and result in the ecological segregation of both sexes. In the present study, we investigated patterns of sexual dimorphism of morphological traits relevant for locomotion in two lacertid lizards, Podarcis bocagei and Podarcis carbonelli, aiming to identify ontogenetic sources of variation. We analysed trunk and limb variation in relation to total body size, as well as the covariation of different traits, aiming to shed light on the proximate causation of adult sexual dimorphism. We find that, although immatures are generally monomorphic, adult females have a longer trunk, and adult males have longer fore and hind limbs. Both sexes differ substantially with respect to their growth trajectories and relationships between traits, whereas, in some cases, there are signs of morphological constraints delimiting the observed patterns. Because of the direct connection between limb size/shape and locomotor performance, which is relevant both for habitat use and escape from predators, the observed patterns of sexual dimorphism are expected to translate into ecological differences between both sexes.
Basic and Applied Ecology, 2007
Die ökologischen Bedingungen und die Nahrungsqualität haben Einfluss auf das Alter und die Größe ... more Die ökologischen Bedingungen und die Nahrungsqualität haben Einfluss auf das Alter und die Größe bei der Metamorphose von Organismen mit komplexen Lebenszyklen. Dennoch ist wenig darüber bekannt, wie das Nahrungssuchverhalten und die Nahrungswahl durch die ökologischen Bedingungen beeinflusst wird. Die vorliegende Untersuchung stellt zwei Fragen: (1) wie beeinflusst unterschiedliche Nahrung (proteinreich, proteinarm und beides zusammen) das Gedeihen der Larven, und (2) wie verändert sich die Nahrungswahl mit den ökologischen Bedingungen (Interferenz-Konkurrenz, Prädation und Austrocknen des Gewässers)? Um die zweite Frage zu beantworten, boten wird den Kaulquappen beide Nahrungstypen unter verschiedenen Bedingungen an. Wir maßen die Nahrungsaufnahme für beide Nahrungstypen, zusammen mit der Wachstumsrate und den Entwicklungsstadien der Kaulquappen. Wir erwarteten, dass die Kaulquappen unter ungünstigen Wachstumsbedingungen proteinreiche Nahrung wählen würden, die das Wachstum fördert und den Individuen erlauben würde, die risikoreiche Umwelt zu verlassen. Proteinreiche Nahrung beschleunigt die Entwicklung, führt aber auch zu kleineren Kaulquappen, während proteinarme Nahrung bei langsamerer Entwicklung das Wachstum fördert. Die Mischung der beiden ist nur in Bezug auf die Wachstumsrate vorteilhafter. Unsere Untersuchung der Kaulquappen zeigte, dass die Nahrungswahl nicht unveränderlich war, sondern in Abhängigkeit von den ökologischen Zusammenhängen in vorhersehbarer Weise variieren konnte. Wenn die Kaulquappen interferierender Konkurrenz und austrocknenden Gewässern ausgesetzt waren, ernährten sich die Kaulquappen von Nahrung, welche die Entwicklung förderte, während sie in der Kontrollgruppe und der Prädatorenvariante selektiv Nahrung fraßen, die das Wachstum förderte. Unsere Daten zeigen, dass die Nahrungswahl der Kaulquappen eine adaptive Antwort auf ökologische Veränderungen darstellen kann. Solch eine Selektion/Antwort würde das Wachstum, die Entwicklung und das Überdauern der Art erhöhen.
Animal Biology, 2006
In complex aquatic ecosystems, intraspecific competition for food can evolve into dietary differe... more In complex aquatic ecosystems, intraspecific competition for food can evolve into dietary differences related to body size, gender, capture ability, and habitat use. The diet of the viperine snake, Natrix maura, an aquatic predator which forages on fish and amphibians, has been studied in parallel with food availability in a small locality of the Matarranya River (NE Spain). Fish abundance values in this Mediterranean river, which hosts one of the highest rates of fish diversity in Europe, were estimated through electrofishing. Natrix maura fed on four of the ten fish species available and captured the only amphibian detected. Three of these fishes were the most abundant species in the river. The fourth fish was the river blenny, a small and rare benthonic species of which the males protect eggs laid under stones at the bottom of the river during reproductive periods. This behaviour makes it easy prey for N. maura. However, the river blenny was caught mostly by small- and medium-siz...
Uploads
Papers by Gustavo Llorente