Gustavo A. Llorente

Intraspecific ecomorphological variation: linear and geometric morphometrics reveal habitat-related patterns within Podarcis bocagei wall lizards

Morphological variation in relation to habitat is known to occur in several lizard groups. Comparative studies have linked morphology and habitat use, showing that locomotion is the principal mediator of this evolutionary relationship. Here, we investigate intraspecific ecomorphological variation in Podarcis bocagei by examining three habitat types, representing a variety between saxicolous and ground‐dwelling habits. Our results indicate variation in absolute and relative limb length, but patterns are only partially concordant to biomechanical predictions. Whereas the femur and hind foot are longer in ground‐dwelling lizards, confirming previous observations, the tibia and hind limb are relatively shorter, contradicting expectations. Additionally, head shape varies substantially between habitats, in line with a hypothesis of mechanical restrictions related to microhabitat and refuge use. Finally, we detect male‐specific variation between habitats in total body size and head size, providing evidence for interactions between natural and sexual selection. Although performance and behaviour studies are necessary to definitely confirm the functional and evolutionary significance of the observed patterns, our study indicates that ecomorphological adaptations can arise in a very short evolutionary time in this group of lizards.

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.

The pond network: can structural connectivity reflect on (amphibian) biodiversity patterns?

Landscape connectivity is a very recurrent theme in landscape ecology as it is considered pivotal for the long term conservation of any organism’s populations. Nevertheless, this complex concept is still surrounded by uncertainty and confusion, largely due to the separation between structural and functional connectivity. Amphibians are the most threatened vertebrates around the globe, in Europe mostly due to habitat alteration, and to their particular life cycle. Pond breeding amphibians are considered to be organised in metapopulations, enhancing the importance of landscape connectivity in this group of animals. We sampled the amphibian species present in two pond groups in Central Western Spain. We applied the graph theory framework to these two pond networks in order to determine the importance of each pond for the entire network connectivity. We related the pond importance for connectivity with the species richness present in each pond. We tested if connectivity (partially) determined the presence of the amphibian species sampled using logistic regression. The results show that the structural connectivity of the pond network impacts on the amphibian species richness pattern and that the importance of the pond for the connectivity of the network is an important factor for the presence of some species. Our results, hence, attest the importance of (structural) landscape connectivity determining the pattern of amphibian (functional) colonization in discrete ponds.

Food availability induces geographic variation in reproductive timing of an aquatic oviparous snake (Natrix maura)

The viperine snake Natrix maura is a common water snake, which forages on aquatic prey such as fish and frogs in Western Mediterranean water bodies. Female viperine snakes collected from three populations at the Iberian Peninsula during the vitellogenesis period were compared. Mean clutch size and range, as well as the slope of the regression between body size and clutch size, did not show differences between populations. In contrast, mean size of enlarged follicles of females collected in May from the Ebro Delta proved significantly smaller than those of females from the Matarranya River (50 km far) and the Granada Depression (500 km far). There were no differences in climatic conditions between areas. However, seasonal variation in food availability was significantly different in the Ebro Delta. In this area, the rice fields are dry in early spring as men control the water flow, and prey are not available. This energetic constraint induced female viperine snakes to adjust reproductive timing according to seasonal availability and to delay vitellogenesis for at least one month. By contrast, other Mediterranean populations exhibited a rather high prey availability from early spring (e.g. Matarranya River), females being in good condition in this season and consequently vitellogenesis starting earlier than in the Ebro Delta. This study illustrates a new case of reproductive plasticity in snakes.

Reproductive Cycle in a Pyrenean Oviparous Population of the Common Lizard (Zootoca Vi Vipara)

High altitude reptiles inhabit adverse environments that condition their reproductive biology. The reproductive and fat body cycles of a high altitude oviparous population of the Common lizard (Zootoca vivipara) in the central Pyrenees were analysed and compared with data on other oviparous and viviparous populations from lower altitudes found in the literature. The studied population shows an extremely short reproductive period. Males show a mixed-type spermatogenesis with very short, vernal spermiogenesis. They emerge from their winter burrows earlier than females and remain unfertile until females start activity and the breeding season begins. Large males release more sperm in copulations than small ones. Females synchronically lay a single clutch per year whereas other oviparous populations living at lower altitudes are iteroparous. Females invest more fat reserves from different compartments (liver, tail) than males, but later in the reproductive season. This major energetic stress seems to be due to the long period of oviductal egg retention. The main effect of altitude on oviparous Zootoca vivipara is the shortening of the reproductive period, which precludes the laying of a second clutch. However, no substantial differences (other than reproductive modality) have been detected between this high mountain oviparous population and viviparous ones. This suggests that not only viviparity but also oviparity is a suitable strategy in such environmental conditions.

Food availability determines the response to pond desiccation in anuran tadpoles

Food availability and pond desiccation are two of the most studied factors that condition amphibian metamorphosis. It is well known that, when food is abundant, organisms undergo metamorphosis early and when they are relatively large. The capability of anurans to accelerate their developmental rate in response to desiccation is also common knowledge. These two variables must act together in nature, since we know that, as a pond dries, the per capita resources decrease. We conduct an experiment to evaluate the effects of desiccation and food availability separately and in combination in tadpoles of the painted frog (Discoglossus pictus). We demonstrate that food deprivation leads to slow growth rates, which delay metamorphosis and produce smaller size and weight. The capability to accelerate metamorphosis when facing a drying pond is also confirmed, but, nevertheless, with factor interaction (when the pool is drying and resources are scarce) the capacity to respond to desiccation is lost. In addition, slow drying rates are shown to be stressful situations, but not enough to provoke a shortening of the larval period; in fact, the larval period becomes longer. We also demonstrate that the interaction of these factors changes the allometric relationship of different parts of the hind limb, which has implications for the biomechanics of jumping. Due to low mortality rates and an adequate response to both environmental factors, we expect D. pictus to have a great invasive potential in its new Mediterranean distribution area, where lots of temporary and ephemeral ponds are present.

Comparing Filippi and Luiselli's (2000) method with a cartographic approach to assess the conservation status of secretive species: the case of the Iberian snake-fauna

The conservation status of the snake fauna of a given region or territory is often hard to estimate due the secretive habits of these animals, as well as of the lack of long-term demographic studies and generally low population densities. We examined the conservation status of the snakes from the Iberian Peninsula by applying two complementary methods. The first method, created by Filippi and Luiselli for a study of the Italian snakes conservation status, takes into account the ecological and non-ecological attributes which make species vulnerable to extinction. The second is a cartographic analysis which consists of calculating two indexes derived from the comparison of old and recent citations in UTM 10×10 km squares of Iberian snakes by means of extensive database sets. For each species, we calculated the percentage of recent citations, and the percentage of squares with both old and recent citations. Species with low proportion of recent citations and new squares appeared to be in decline. We found considerable coincidence between the two methods in the identification of the most threatened snake species: Vipera latastei, Coronella girondica ,a ndNatrix natrix. We suspect that the ecological specialisation and the low reproductive output make C. girondica and V. latastei prone to extinction when faced with environmental changes (i.e. habitat loss). For N. natrix, we argue that this semi-aquatic snake experiences suboptimal environmental conditions in Mediterranean habitats. A combination of both methods proved adequate to detect vulnerability to extinction of snake species, hence revealing an effective tool for establishing conservation strategies in snakes and other secretive faunas.

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).