Albert Montori

A comparative study of predator-induced phenotype in tadpoles across a pond permanency gradient

In a field survey the distribution of pond-breeding anuran species and their potential large predators was investigated along a freshwater habitat gradient, ranging from ephemeral pools to permanent ponds. In a laboratory experiment predator-induced plasticity was examined for all tadpole species to test whether the plastic response of ephemeral and temporary pond species differs from that of permanent pond species. Desiccation and predation pose conflicting demands; reduced activity lowers the risk of death by predation but increases the risk of death by desiccation. It was expected that species from time-constrained habitats would display a morphotype that would reduce vulnerability to invertebrate predators, thus allowing these species to maintain a high level of activity, whereas species from permanent ponds would avoid predation both morphologically and behaviourally. Species distribution and predator composition along the hydroperiod gradient differed. Variations between ephemeral and temporary ponds can be attributed to hydroperiod differences and the presence of large invertebrate predators in temporary ponds, whereas the contrasts between temporary and permanent ponds can only be attributed to the hydroperiod, since the presence and abundance of top predators are similar in both habitat types. With the exception of bufonids, all species showed predator-induced plasticity in agreement with previous studies. Tadpole species differed in the integration of the phenotypic traits measured, but differences observed between species could not be attributed only to habitat. Species from temporary habitats showed an expected response, with a low reduction of activity in comparison with the rest of the species. The lack of general patterns in the morphological changes suggests that species within the same habitat type did not converge on similar phenotypes, perhaps due to functional constraints on differences in microhabitat use in the water column.

Breeding phenology of an amphibian community in a Mediterranean area

We studied the temporal breeding patterns and strategies of anuran assemblages in the Mediterranean region over five consecutive years. We collected monthly data on the number of clutches, tadpoles and juveniles presence of six species in 98 ponds. The data showed a great temporal segregation of species. Species using permanent ponds have a breeding peak that is related to temperature whereas reproductive success in temporary pond breeders is determined by rainfall pulses. Many species showed great plasticity of reproduction with two peaks: one in spring and the other in autumn. In spite of this temporal segregation, a large overlap was observed among species during the larval phase period. Three species (Alytes obstetricans, Pelodytes punctatus and Rana perezi) have over-wintering tadpoles. We discuss temporal segregation, differences between species in their breeding strategies and variable conditions between years as factors that favour the temporal coexistence of species in the Mediterranean region.

Northward shifts of the distributions of Spanish reptiles in association with climate change.

It is predicted that climate change will drive extinctions of some reptiles and that the number of these extinctions will depend on whether reptiles are able to change their distribution. Whether the latitudinal distribution of reptiles may change in response to increases in temperature is unknown. We used data on reptile distributions collected during the 20th century to analyze whether changes in the distributions of reptiles in Spain are associated with increases in temperature. We controlled for biases in sampling effort and found a mean, statistically significant, northward shift of the northern extent of reptile distributions of about 15.2 km from 1940-1975 to 1991-2005. The southern extent of the distributions did not change significantly. Thus, our results suggest that the latitudinal distributions of reptiles may be changing in response to climate change.

Helminth communities of two lizard populations (Lacertidae) from Canary Islands (Spain): Host diet-parasite relationships

A parasitological survey has been carried out to determine the relationships between host diet and parasite fauna. Diet, and infracommunities and component communities of two subspecies of lacertid lizards, Gallotia galloti galloti (Oudart, 1839) and G. g. palmae (Boettger et Muller, 1914) from Tenerife and La Palma islands (Canary Islands, Spain), have been analysed. High values of parasite infection parameters were found in both subspecies, which were only infected by nematodes of the family Pharyngodonidae. Plant matter was mainly consumed by both lizard subspecies and relevant amounts of mineral matter were also found in both hosts. Diet of these lacertid lizards was correlated with their parasite fauna formed by monoxenous nematodes parasitising herbivorous reptiles, as in tortoises and iguanid lizards. Abundance and richness of parasites increased with consumption of plant matter in G. g. galloti. Helminthological data support the idea of a tendency of both hosts towards herbivory, probably related to their own phylogeny linked to insularity.

Hierarchical competition in pond-breeding anuran larvae in a Mediterranean area

The anuran larval guild is frequently characterised by the co-occurrence, with high niche overlap, of distinct species in the same pond at variables densities during development. Anuran larvae have therefore been widely studied as a model system for competition. Body size and activity level are considered the most important factors that influence the outcome of competition between tadpoles. As species from temporary ponds normally show higher activity levels in order to achieve rapid growth and thus reduce the risk of desiccation, these species are often considered superior competitors. We designed several laboratory experiments to examine the intra- and interspecific effects on growth rate, mass at metamorphosis and survival to metamorphosis of six species in a Mediterranean area. Body size and activity level were used as explanatory covariables to determine competitive ability among species. An asymmetric and hierarchical relationship was found among the six species. Larger tadpole species were more successful in competitive interactions than smaller ones, but no relationship was found between activity level and competition effects. Species typically found in temporary ponds (Pelodytes punctatus and Bufo calamita) were considered poor competitors in contrast with other communities studied. Species with low competitive ability can persist by using refuges in which competition is reduced (e.g. ephemeral ponds).

Locomotor Mode and the Evolution of the Hindlimb in Western Mediterranean Anurans

The evolutionary association between morphology, locomotor performance and habitat use is a central element of the ecomorphological paradigm, and it is known to underlie the evolution of phenotypic diversity in numerous animal taxa. In anuran amphibians the hindlimb acts as the propulsive agent, and as such, it is directly associated with jumping performance. In this study we combine individual- and species-level analyses to examine the effects of locomotor mode on body size and hindlimb morphology of Western Mediterranean anurans. In addition to the commonly studied hindlimb traits, we also examine the ratio between tibiofibula and femur length. Body size shows no signs of an evolutionary association to locomotor mode. Instead, hindlimb traits are significantly differentiated between locomotor groups, both at the individual and species levels. Specifically, we observe a gradient of tibiofibula to femur ratio values that matches biomechanical predictions. The analysis of adult static allometries indicates that these differences arise early in ontogeny. By comparing the fit of distinct evolutionary models we provide evidence that the locomotor mode adopted by each species to match the requirements of the habitat it frequents has shaped the evolution of the hindlimb, but not body size.

Habitat features affecting the small-scale distribution and longitudinal migration patterns of Calotriton asper in a Pre-Pyrenean population

The longitudinal movements and abiotic factors that determine the distribution of Pyrenean mountain newts (males, females, amplexus and metamorphic newts) were examined in a 1500 meters segment of a Pre-Pyrenean stream. Migration of adult newts was studied by means of capture-recapture techniques in the course of one year. Our results indicate that the mean distance the newts migrated per year was less than 50 meters and the population could be considered sedentary. No significant differences in longitudinal movement patterns between the sexes were observed, and movement patterns were more or less constant over time. Habitat variables determining newt abundance was estimated by means of a GLM. Our results indicate that the number of refugia (wood debris, stones and fissures) determines the distribution of newts. Larval abundance was correlated with stream-bed structure.

Range contraction and loss of genetic variation of the Pyrenean endemic newt Calotriton asper due to climate change

Many studies have identified climate warming to be among the most important threats to biodiversity. Climate change is expected to have stronger effects on species with low genetic diversity, ectothermic physiology, small ranges, low effective populations sizes, specific habitat requirements and limited dispersal capabilities. Despite an ever-increasing number of studies reporting climate change-induced range shifts, few of these have incorporated species’ specific dispersal constraints into their models. Moreover, the impacts of climate change on genetic variation within populations and species have rarely been assessed, while this is a promising direction for future research. Here we explore the effects of climate change on the potential distribution and genetic variation of the endemic Pyrenean newt Calotriton asper over the period 2020–2080. We use species distribution modelling in combination with high-resolution gridded climate data while subsequently applying four different dispersal scenarios. We furthermore use published data on genetic variation of both mtDNA and AFLP loci to test whether populations with high genetic diversity (nucleotide diversity and expected heterozygosity) or evolutionary history (unique haplotypes and K clusters) have an increased extinction risk from climate change. The present study indicates that climate change drastically reduces the potential distribution range of C. asper and reveals dispersal possibilities to be minimal under the most realistic dispersal scenarios. Despite the major loss in suitable climate, the models highlight relatively large stable areas throughout the species core distribution area indicating persistence of populations over time. The results, however, show a major loss of genetic diversity and evolutionary history. This highlights the importance of accounting for intraspecific genetic variation in climate change impact studies. Likewise, the integration of species’ specific dispersal constraints into projections of species distribution models is an important step to fully explore the effects of climate change on species potential distributions.

Alimentación de las larvas de tritón pirenaico, Euproctus asper, en el prepirineo de la Cerdaña, España

Se ha estudiado la dieta estacional de los ejemplares larvarios de una poblacion de triton pirenaico Euproctus asper localizada en un torrente de montana media del prepirineo oriental espanol. Las larvas de diptero son la presa fundamental de la dieta, siendo secundariamente las larvas de plecoptero y de efemeroptero las presas de mayor importancia, tanto en numero como en biomasa. El intervalo de talla de presas mas consumido se situa entre los 1.5 y 2 mm., situandose la media en los 3.02 mm. Se ha obtenido una correlacion significativa entre la talla media de las presas del estomgo y la talla corporal de la larva (r s = 0.38).

Impact of ammonium nitrate and sodium nitrate on tadpoles of Alytes obstetricans

The presence of pesticides, herbicides and fertilisers negatively affect aquatic communities in general, and particularly amphibians in their larval phase, even though sensitivity to pollutants is highly variable among species. The Llobregat Delta (Barcelona, Spain) has experienced a decline of amphibian populations, possibly related to the reduction in water quality due to the high levels of farming activity, but also to habitat loss and alteration. We studied the effects of increasing ammonium nitrate and sodium nitrate levels on the survival and growth rate of Alytes obstetricans tadpoles under experimental conditions. We exposed larvae to increasing concentrations of nitrate and ammonium for 14 days and then exposed them to water without pollutants for a further 14 days. Only the higher concentrations of ammonium (>33.75 mg/L) caused larval mortality. The growth rate of larvae was reduced at ≥22.5 mg/L NH4+, although individuals recovered and even increased their growth rate once exposure to the pollutant ended. The effect of nitrate on growth rate was detected at ≥80 mg/L concentrations, and the growth rate reduction in tadpoles was even observed during the post-exposure phase. The concentrations of ammonium with adverse effects on larvae are within the range levels found in the study area, while the nitrate concentrations with some adverse effect are close to the upper range limit of current concentrations in the study area. Therefore, only the presence of ammonium in the study area is likely to be considered of concern for the population of this species, even though the presence of nitrate could cause some sublethal effects. These negative effects could have an impact on population dynamics, which in this species is highly sensitive to larval mortality due to its small clutch size and prolonged larval period compared to other anuran amphibians.