Bufo Calamita Research Articles

Defining population boundaries: use of three Bayesian approaches with microsatellite data from British natterjack toads (Bufo calamita)

Defining population boundaries: use of three Bayesian approaches with microsatellite data from British natterjack toads (Bufo calamita)

Predation on Amphibian eggs and larvae in temporary ponds : the case of Bufo calamita in southwestern Spain

Eggs and larvae of bufonids are often unpalatable or toxic. We assessed the vulnerability of Bufo calamita eggs and larvae to nine potential predators. Ingestion did not exert toxic or distasteful effects on most predators, but small predators had difficulties extracting eggs from the jelly. In laboratory, the most intensive predation was by larvae of Sharp-ribbed Salamander Pleurodeles waltl (Amphibia, Salamandridae), the common crustacean Triops cancriformis (Crustacea Notostraca) and the introduced Red Swamp Crayfish Procambarus clarkii (Decapodes, Cambaridae). Predation rate was related to the body size of predators. Predation in breeding ponds reached up to 95-100% eggs, and breeding success was only recorded in ponds without the three major predators above. While other species of Bufo that contain toxic substances are able to colonize permanent aquatic habitats, for Bufo calamita only the compact jelly of eggs serves to deter small predators.

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

AbstractThe 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).

Editorial and Retrospective 2007

Editorial and Retrospective 2007

Quantifying functional connectivity: experimental assessment of boundary permeability for the natterjack toad (Bufo calamita)

Like other pond-breeding amphibians, the natterjack toad (Bufo calamita) typically presents a patchy distribution. Because the species experiences high probabilities of local population extinction, its persistence within landscapes relies on both local and landscape-scale processes [dispersal allowing the (re)colonization of habitat patches]. However, the structure and composition of the matrix surrounding local populations can alter the dispersal rates between populations. As shown previously (Landscape Ecol 19:829-842, 2004), the locomotor performances of individuals at the dispersal stage depend on the nature of the component crossed: some landscape components offer high resistance to movement (high resistance or high viscosity components) whereas others allow high efficiency of movement (low resistance components). We now examine the ability of individuals to discriminate between landscape components and select low-resistance components. Our experimental study investigates the ways in which young natterjack toads choose from among landscape components common to southern Belgium. Toadlets (the dispersal stage) were experimentally confronted with boundaries between surrogates of sandy soils, roads, forests, agricultural fields and intensive pastures. Our results show: 1 the ability of toadlets to react to boundaries between landscape components, 2 differences in permeability among boundaries, and 3 our inability to predict correctly the permeability of the boundaries from the patch-specific resistance assessed previously. Toadlets showed a preference for bare environments and forests, whereas they avoided the use of agricultural environments. This pattern could not be explained in terms of patch-specific resistance only, and is discussed in terms of mortality risks and resource availability in the various landscape components, with particular attention to repercussions on conservation strategies.

Gene flow and functional connectivity in the natterjack toad

Functional connectivity is a key factor for the persistence of many specialist species in fragmented landscapes. However, connectivity estimates have rarely been validated by the observation of dispersal movements. In this study, we estimated functional connectivity of a real landscape by modelling dispersal for the endangered natterjack toad (Bufo calamita) using cost distance. Cost distance allows the evaluation of 'effective distances', which are distances corrected for the costs involved in moving between habitat patches in spatially explicit landscapes. We parameterized cost-distance models using the results of our previous experimental investigation of natterjack's movement behaviour. These model predictions (connectivity estimates from the GIS study) were then confronted to genetic-based dispersal rates between natterjack populations in the same landscape using Mantel tests. Dispersal rates between the populations were inferred from variation at six microsatellite loci. Based on these results, we conclude that matrix structure has a strong effect on dispersal rates. Moreover, we found that cost distances generated by habitat preferences explained dispersal rates better than did the Euclidian distances, or the connectivity estimate based on patch-specific resistances (patch viscosity). This study is a clear example of how landscape genetics can validate operational functional connectivity estimates.

Amphibians and squamate reptiles from the early Upper Pleistocene of Bois Roche Cave (Charente, southwestern France)

The layers, ascribed to the early Upper Pleistocene (Middle Palaeolithic) of Bois Roche Cave, contain an abundant bone assemblage, as well as a few lithic artifacts, in a hyena den. The amphibians and squamate reptiles fauna consist of: Pelobates fuscus (Pe- lobatidae), Pelodytes punctatus (Pelodytidae), Bufo bufo and Bufo calamita (Bufonidae), Hyla sp. (Hylidae), Rana temporaria and Rana cf. R. lessonae (Ranidae), a small lacertid (Lacertidae), Anguis fragilis (Anguidae), Natrix natrix and Coronella austriaca (Colubri- dae) and a Vipera berus complex species (Viperidae). The herpetofauna may be con- temporaneous of cold-temperate climatic conditions. P. fuscus, R. lessonae and V. berus complex underline more continental climatic conditions mitigated by the occurrence of species like P. punctatus and B. calamita with western Atlantic affinities. The palaeoenvi- ronment, suggested by herpetofauna, was a very open environment, with damp meadows and small grove areas of broad-leaved trees and conifers. The proportion and distribution of species in the stratigraphic sequence allow hypotheses concerning minor climatic variations to be advanced.

Atlas de distribución y estado de conservación de los Anfibios de la Comunidad de Madrid

Successful management and conservation planning depend upon the availability, integration and updating of information provided by different disciplines. This paper compiles relevant information for the conservation of amphibians in Comunidad de Madrid (Spain). We obtained chorological information from 1384 sampling localities throughout the region of Madrid, and reviewed relevant scientific literature for the management of amphibian populations in this area. We found at least one amphibian species in 70,3% of sampled localities. Results are illustrated in distribution maps of all 18 species found: Salamandra salamandra, Pleurodeles waltl, Mesotriton alpestris, Lissotriton boscai, Triturus marmoratus, Triturus pygmaeus, Alytes obstetricans, Alytes cisternasii, Discoglossus galganoi, Discoglossus jeanneae, Pelobates cultripes, Pelodytes punctatus, Hyla arborea, Hyla meridionalis, Bufo bufo, Bufo calamita, Rana iberica and Rana perezi. Distribution maps are presented in five-kilometer side UTM grids cells. We compare and integrate our results with previous studies and outline groups of populations representing independent management units, for which we propose risk categories according to the criteria established by the International Union for the Conservation of Nature (IUCN) at the regional level. Finally, we point out the main threats for the survival of amphibian populations and discuss possible actions to improve their conservation status.

Predation by an Exotic Crayfish, Procambarus Clarkii, on Natterjack Toad, Bufo Calamita, Embryos: Its Role on the Exclusion of this Amphibian from its Breeding Ponds

Procambarus clarkii, an American crayfish, was introduced in the SW Iberian Peninsula three decades ago. This region has no native crayfishes; therefore, P. clarkii constitutes a potential threat for the embryos and larvae of amphibians, which may lack evolved defenses against it. We assessed the effects of this crayfish on the Natterjack Toad, Bufo calamita, using two complementary approaches. First, we studied the effect of crayfish presence on B. calamita breeding habitat use in temporary ponds of Doñana Natural Park (southwestern Spain). We surveyed 31 temporary ponds for the presence of P. clarkii and B. calamita eggs and tadpoles, and we conducted a logistic regression to determine if crayfish were significantly associated with Natterjack Toad distribution after habitat variables were taken into account. Second, we experimentally evaluated the impact of P. clarkii on B. calamita embryos in natural ponds with a two × two factorial experiment, using two ponds (one with and one without crayfish) and two treatments (embryos exposed or not exposed to predators). Crayfish presence was a negative predictor of B. calamita breeding habitat use; co-occurrence of the two species was limited to only one pond. Moreover, the predation experiment showed that survival of B. calamita embryos was strikingly reduced when they were directly exposed to crayfish compared to survival in all other treatments. Our results indicated that P. clarkii has a strong effect on B. calamita reproductive success and that it may play an important role in structuring amphibian communities in temporary ponds.

The movements and breeding site fidelity of the natterjack toad (Bufo calamita) in an urban park near Paris (France) with management recommendations

Abstract The isolation of animal populations due to urban activities provides a useful framework for studying the consequences of landscape fragmentation. We studied a population of natterjack toads (Bufo calamita) in an urban park near Paris, France. In 2001 and 2002 we used radio-tracking to estimate the terrestrial movements of adults around their breeding sites. Twenty-four toads were equipped with internal transmitters in 2001 to record movements during and after the breeding period. In 2002, 19 males were released at 300 and 380 meters from their breeding ponds. Natterjack toad movements around and outside their breeding ponds were reduced compared to previous observations on this species. The only exchanges that were observed occurred between closely neighbouring breeding sites. During a translocation experiment in 2002, 58% of the displaced males returned to their site of capture and this happened mainly during the breeding period. The remaining 42% stayed close to the release site. There was no exchange of males between distant breeding sites. Natterjack toad conservation needs to take into account the high fidelity to a breeding site and the reduced breeding dispersal and homing ability of these animals. Conservation biology in urban landscapes constitutes a specific urban ecology with specific concepts such as 'population area'. Information from this study can assist land managers in establishing protected areas of high habitat quality around breeding ponds in urban areas, and managing parks for the protection of amphibian populations, particularly by facilitating exchanges between available areas.

Demographic life history traits of reproductive natterjack toads (Bufo calamita) vary between northern and southern latitudes

AbstractDemographic life history traits were investigated in three Bufo calamita populations in Germany (Rhineland-Palatinate: Urmitz, 50°N; 1998-2000) and Spain (Catalonia: Balaguer, Mas de Melons, 41°N; 2004). We used skeletochronology to estimate the age as number of lines of arrested growth in breeding adults collected during the spring breeding period (all localities) and during the summer breeding period (only Urmitz). A data set including the variables sex, age and size of 185 males and of 87 females was analyzed with respect to seven life history traits (age and size at maturity of the youngest first breeders, age variation in first breeders, longevity, potential reproductive lifespan, median lifespan, age-size relationship). Spring and summer cohorts at the German locality differed with respect to longevity and potential reproductive lifespan by one year in favour of the early breeders. The potential consequences on fitness and stability of cohorts are discussed. Latitudinal variation of life history traits was mainly limited to female natterjacks in which along a south-north gradient longevity and potential reproductive lifespan increased while size decreased. These results and a review of published information on natterjack demography suggest that lifetime number of offspring seem to be optimized by locally different trade-offs: large female size at the cost of longevity in southern populations and increased longevity at the cost of size in northern ones.

Influence of developmental stage on sensitivity to ammonium nitrate of aquatic stages of amphibians

In static renewal experiments, we studied how developmental stage influences the effect of ammonium nitrate on embryonic and larval stages of anuran amphibians. The observed lethal effects caused by ammonium nitrate increased with both concentration and duration of exposure. Significant differences were observed in sensitivity to ammonium nitrate as a function of developmental stage in Discoglossus galganoi, Pelobates cultripes, and Bufo calamita. In D. galganoi and P. cultripes, younger individuals displayed greater acute effects from the chemical fertilizer compared with older individuals. For example, 100% of P. cultripes hatchlings died after 4 d of exposure to a nominal concentration of 225.8 mg N-NO3NH4/L, whereas less than 40% of individuals from older larval stages died when exposed to this concentration. A delay of 4 d in the beginning of the exposure to the chemical was enough to cause significant differences in sensitivity. Bufo calamita showed a higher sensitivity in later larval stages after 12 d of exposure. Hyla meridionalis and B. calamita were less sensitive than the other two species. Peak ammonium nitrate concentrations usually occur when amphibians are breeding and, thus, when the most sensitive aquatic stage is in the water. The developmental stage of the test animals should be considered when evaluating the risk of ammonium nitrate to amphibians.

Lusitania revisited: A phylogeographic analysis of the natterjack toad Bufo calamita across its entire biogeographical range

Attempts to understand the current distributions of plants and animals require both historical and ecological information. Phylogeography has proved highly effective in elucidating historical events such as postglacial colonisations in north temperate zones. However, interesting questions still await resolution. Lusitanian distributions of fauna and flora in western Europe, for example, have puzzled biogeographers for more than 150 years. Lusitanian species have highly disjunct distributions in Ireland and in Iberia, often with few or no other populations inbetween. Despite much debate, no agreed explanation for Lusitanian distributions has yet emerged. We investigated the phylogeographic structure of one Lusitanian species, the natterjack toad Bufo calamita, using mitochondrial DNA control region sequences and allelic variation at eight microsatellite loci. Our results show that this amphibian must have survived in north European refugia, as well as in Iberia, during and since the last (Weichselian) glacial maximum around 20,000 years before present (BP). Subsequent local recolonisation after the Younger Dryas cooling around 11,000 years BP best explains the Lusitanian aspect of natterjack toad distribution.

Adaptation or exaptation? An experimental test of hypotheses on the origin of salinity tolerance inBufo calamita

The natterjack toad (Bufo calamita) shows variation in embryonic and larval salinity tolerance across populations in southern Spain. However, its aquatic/terrestrial biphasic life cycle, together with remarkable differences in salinity tolerance between Spanish and UK freshwater populations suggest an alternative hypothesis to local adaptation. Drought resistance during the terrestrial phase and salinity tolerance during the aquatic phase are both related to osmotic stress tolerance, and if there were an association between them, one could have evolved as an exaptation from the other. To test such an association, we reared B. calamita juveniles from three populations known to differ genetically in their salinity tolerance, under either dry or humid conditions. Drought decreased growth rate, enhanced burying behaviour, and decreased foraging activity and efficiency. No significant population x treatment interaction was found for any variable, i.e. populations were equally affected by drought. These results do not support the hypothesis of a genetic association between salinity and drought tolerance.

RELATIVE IMPORTANCE OF POPULATION PROCESSES AND HABITAT CHARACTERISTICS IN DETERMINING SITE OCCUPANCY OF TWO ANURANS

The ecological niche is the conceptual foundation for the analysis of species distributions. Habitat variables and resources are therefore thought to determine the distribution of a species. However, metapopulation and source-sink models posit that population processes determine the local distribution of a species; metapopulation theory suggests that many suitable patches could be unoccupied and source-sink theory suggests that unsuitable patches could be occupied. We examined whether the distribution of 2 European anurans (tree frog [Hyla arborea] and natterjack toad [Bufo calamita]) was determined by habitat variables, local population size (as indexed by the number of calling males), or metapopulation characteristics are. We found that the distribution of both species was best predicted by the number of calling males in the previous years. This supports the idea that population processes are more important determinants of distribution than habitat characteristics. We suggest that future distribution models explicitly incorporate population dynamic processes. Our results suggest that there is a threshold number of calling males above which a population is almost certain to persist in the short-term. If more robust population data are not available, such a threshold should be useful for managing threatened anuran species because the number of calling males is easily determined.

Six polymorphic microsatellite loci in the Natterjack toad, Bufo calamita

AbstractThe Natterjack toad, Bufo calamita, is a locally endangered anuran endemic to Europe. It has been used as a model organism in several ecological studies. When studying the genetic structure of marginalized populations of the species, there was a need to involve more loci in the study than those previously published. Here we present the development of six polymorphic microsatellite loci in the Natterjack. The loci will be used for studying population genetic structure and gene flow between populations.

Archaeological evidence of former occurrence and changes in fishes, amphibians, birds, mammals and molluscs in the Wadden Sea area

Animal remains are well preserved in archaeological sites, especially the terp sites, of the Wadden Sea area of Denmark, Germany and The Netherlands. Here, we provide an overview on the wild mammals, birds, fishes, amphibians and molluscs found in coastal sites dating from 2700 to 2600 B.C. and 700 B.C. to A.D. 1600. Coastal people used a variety of animal species for food and other purposes. Hunting, fowling, fishing and agriculture did not have much influence on wild stocks in the period from the late Bronze Age/early Iron Age until the late Middle Ages. However, large changes to the landscape were made in the late Middle Ages by diking and damming. As a result, some species such as the northern vole (Microtus oeconomus) and the natterjack toad (Bufo calamita) disappeared from the area except for some dune districts on the islands, and others became rare, such as the grey seal (Halichoerus grypus) and the lagoon cockle (Cerastoderma lamarcki). New habitats arose for birds of dry meadows and fields, like lapwing (Vanellus vanellus) and black-tailed godwit (Limosa limosa). Sturgeon (Acipenser sturio) disappeared from the Wadden Sea within a few decades since A.D. 1890 due to the destruction of spawning grounds by damming and high exploitation pressure. Our findings are important for the ecological history of the region.

Quantifying functional connectivity: Experimental evidence for patch-specific resistance in the Natterjack toad (Bufo calamita)

Despite the importance assigned to inter-patch movements in fragmented systems, the structure of landscape between suitable habitat patches, the matrix, is often considered as to be of minor interest, or totally ignored. Consequently, models predicting metapopulation dynamics typically assume that dispersal and movement abilities are independent of the composition of the matrix. The predictions of such models should be invalided if that crucial assumption is unverified. In order to test the hypothesis of a patch-specific resistance, we led an experimental study to assess the matrix effects on the movement ability of juvenile Natterjack toads (Bufo calamita). The movement behaviour of first year toadlets, the dispersal stage in this species, was investigated in an arena experiment. Toadlet mobility was assessed in five landscape components that were mimicked in the lab: sandy soil, road, forest, agricultural field, and pasture. We analysed several movement components including move length, speed, efficiency and turning angle distribution. Our results showed that movement ability was strongly affected by the land cover, even if body size modulated the behavioural responses of toadlets. Performances were the best in the arenas mimicking sand and roads, and the worst in the forest arena, toadlet moves being three to five times less effective in the latter. The mobility was intermediate in the two other arenas. We propose here a new method to quantify functional connectivity, based on quantitative estimates of relative values for resistance of landscape components. This method offers a reliable alternative for resistance value estimates to subjective ‘expert advice’ or inference from genetic population structure.

Distribution of amphibians and reptiles in central Poland: 1980-2000

Based on 3047 records from 97 recorders distribution maps were drawn for the amphibians and reptiles of central Poland (lirom 51°00’N to 52°15’N and from 18°20’E to 20°20’E). The study area was divided into 180 atlas fields based on the geographic grid. All data were gathered in 1980-2000, most of them (67%) however, in 1995-2000. 13 taxa of amphibians were found in 143 atlas fields and 6 species of reptiles were found in 121 atlas fields. The amphibians were (given with the number of atlas fields with the species found): 119 - Common frog Rana temporaria Linnaeus, 1758; 114 - Common toad Bufo bufo (Linnaeus, 1758); 97 - Moor frog Rana arvalis Nilsson, 1842; 94 - Fire-bellied toad Bomhina bombina (Linnaeus, 1761); 93 - Pool frog Rana lessonae Camerano, 1882; 87 - Tree frog Hyla arhorea (Linnaeus, 1758); 85 - Green toad Bufo viriiüs Laurenti, 1768; 72 - Smooth newt Triturus vulgaris (Linnaeus, 1758); 70 - Spadefoot Pelobales fuscus (Laurenti, 1768); 69 - Edible frog Rana kl. esculenia Linnaeus, 1758; 39 - Great crested newt Triturus cristatus (Laurenti, 1768); 30 - Marsh frog Rana ridibunda Pallas, 1771 and 28 - the Natterjack Bufo calamita Laurenti, 1768. The reptile species (given with the number o f atlas fields) were: 94 - Sand lizard Lacerta agilis Linnaeus, 1758; 72 - Slow-worm Anguis fragilis Linnaeus, 1758; 67 - Common lizard Lacerta vivipara Jacquin, 1787; 60 - Grass snake Natrix natrix (Linnaeus, 1758), 57 - Adder Vipera berus (Linnaeus, 1758) and 4 - the Smooth snake Coronella austriaca Laurenti, 1768. Six adult specimens of the European pond terrapin Emys orbicularis (Linnaeus) were also found, but breeding of this species in the area studied was not confirmed.

Terrestrial habitat preferences of the natterjack toad during and after the breeding season in a landscape of intensive agricultural activity

AbstractNineteen adult toads equipped with transmitters were followed during and after the breeding period (January to September) in order to estimate their home range area and habitat use in a landscape of cereal agriculture. Median home range area was 0.5 ha (range 0.1-11 ha) during the breeding season (January-April). Home range areas increase during the post-breeding season (April-September) e.g., median minimum concave polygon of 4.1 ha. No relation between home range and toads' body size was observed. Six habitat types were described in the studied area. The proportion of habitats used (i.e. proportion of the pooled positions of 11 toads during the post-breeding season in each habitat) was significantly different from the proportion of available habitats: while crops represented 85% of the available habitat, only 43% of the toads' positions were recorded in this type of habitat. A compositional analysis of habitat preference was performed. At both landscape and individual home range levels, the toads preferred the stone embankments and ditches above all, while the crops were the least preferred habitat. This study highlights the role of habitat linkage and marginal habitats for the persistence of amphibian populations in intensive agricultural and arid landscapes.