Miguel Tejedo

CSIC (Consejo Superior de Investigaciones Científicas-Spanish National Research Council), Evolutionary Ecology, Faculty Member

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Papers by Miguel Tejedo

Niche models at inter‑and intraspecifc levels revealhierarchical niche diferentiationin midwife toads

Effects of body size and timing of reproduction on reproductive success in female natterjack toads ( <i>Bufo calamita</i> )

Journal of Zoology, Dec 1, 1992

This study estimated variability in components of reproductive success in female natterjack toads... more This study estimated variability in components of reproductive success in female natterjack toads (Bufo calamita, Laurenti, 1768) as a function of their body size and timing of reproduction. Two components of reproductive success were analysed: fecundity and metamorphic success. Fecundity, as a function of body size, tended to increase exponentially. Age had a negligible effect once body size was statistically controlled. Egg size was also related to female body size but showed greater variation. Metamorphic success depended on the timing of reproduction. Later breeders suffered an exponential decline in metamorphic success because females spawned at recently-filled ponds of ephemeral duration. Since female body size decreased as the breeding season progressed, it may be inferred that larger, early-breeding females would have a differential reproductive success. The inverse relationship between the timing of reproduction and body size may be based on the energetic physiology of vitellogenesis, and on the potential trade-offs between the allocation of energy to growth—higher in smaller females—and reproduction.

El declive de los anfibios. La dificultad de separar las variaciones naturales del cambio global

El declive de los anfibios. La dificultad de separar las variaciones naturales del cambio global ... more

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Size-Dependent Vulnerability and Behavioral Responses of Tadpoles of Two Anuran Species to Beetle Larvae Predators

Herpetologica, 1993

I studied size-dependent vulnerability and behavioral responses of tadpoles to pre- daceous divin... more I studied size-dependent vulnerability and behavioral responses of tadpoles to pre- daceous diving beetle larvae (Dytiscus pisanus) in two anuran species (Bufo calamita and Pelobates cultripes) that breed in temporary ponds. Experiments revealed that large tadpoles of B. calamita were preferentially selected by the beetle larvae. Moreover, the average number of strikes to grasp a small tadpole was higher than for large tadpoles. However, in P. cultripes, large tadpoles were less likely to be captured than were small tadpoles. Both species differed in growth history; B. calamita has a short growth period and a small tadpole that is unable to avoid predation, whereas P. cultripes grows to a large size that reduces predation rate. Tadpoles of B. calamita show a reduction in mobility in the presence of the predator, whereas tadpoles of P. cultripes do not show it. Phylogenetic constraints restricting size at metamorphosis for B. calamita may lead to the adoption of alternative antipredatory strategies, such as a reduction in activity or habitat segregation.

Absence of the trade-off between the size and number of offspring in the natterjack toad (Bufo calamita)

Oecologia, May 1, 1992

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Contrasting Patterns of Quantitative and Neutral Genetic Variation in Locally Adapted Populations of the Natterjack Toad, Bufo Calamita

Evolution, Oct 1, 2004

The relative importance of natural selection and genetic drift in determining patterns of phenoty... more The relative importance of natural selection and genetic drift in determining patterns of phenotypic diversity observed in nature is still unclear. The natterjack toad (Bufo calamita) is one of a few amphibian species capable of breeding in saline ponds, even though water salinity represents a considerable stress for them. Results from two common-garden experiments showed a pattern of geographic variation in embryonic salinity tolerance among populations from either fresh or brackish environments, consistent with the hypothesis of local adaptation. Full-sib analysis showed increased variation in survival among sibships within population for all populations as osmotic stress was increased (broad-sense heritability increased as salinity raised). Nevertheless, toads native to the brackish water environment had the highest overall survival under brackish conditions. Levels of population genetic differentiation for salinity tolerance were higher than those of neutral genetic differentiation, the latter obtained through the analysis of eight microsatellite loci. Microsatellite markers also revealed little population differentiation, lack of an isolationby-distance pattern, and moderate gene flow connecting the populations. Therefore, environmental stress tolerance appears to have evolved in absence of geographic isolation, and consequently we reject the null hypothesis of neutral differentiation.

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Source of environmental data and warming tolerance estimation in six species of North American larval anurans

Journal of Thermal Biology, Aug 1, 2018

The current global warming scenario has led to a renewed interest in determining which species ar... more The current global warming scenario has led to a renewed interest in determining which species are more vulnerable to climate change. Hence, it is important to understand which factors can affect estimates of species vulnerability. We determined the critical thermal maxima (CT max) for six species of North American anuran larvae and measured the environmental temperatures to which they are exposed during their aquatic stage to estimate their warming tolerance (WT; difference between the critical thermal maximum and the macro-and microhabitat maximum environmental temperatures). Our results indicate that these species exhibited CT max values (37.8-41.7°C) that were similar to other temperate species and positively correlated only with environmental temperatures measured at the microclimate scale. This indicates that microclimatic variables are better predictors of CT max variation than macroclimate data. Moreover, most of the CT max variation found was associated with higher taxonomic levels, indicating that related species may show similar CT max values due to phylogenetic inertia. Studied species also exhibited high values of WT (10.3-22.6°C), similar to temperate amphibian species from other bioregions. This indicates

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Do Male Natterjack Toads Join Larger Breeding Choruses to Increase Mating Success?

Copeia, Feb 11, 1993

Male and female natterjack toads, Bufo calamita, exhibited a high degree of breeding synchronizat... more Male and female natterjack toads, Bufo calamita, exhibited a high degree of breeding synchronization. A polynomial or exponential regression indicated that the operational sex ratio (OSR) between nights increased with number of males in the overall population; hence, OSR varied temporally with chorus size. The comparison of three different groups of calling males within the breeding area, separated from each other and differing in male numbers, revealed similar OSRs between groups. Therefore, OSR did not vary spatially with chorus size. On average, males that attended larger groups obtained higher mating success in one season but not in another. Male movements between groups were directed toward larger groups, with higher OSRs and higher number of calling males, but males did not increase their mating probabilities by moving to another group. Female distribution among groups was correlated with the availability of oviposition sites, but they were not attracted differentially to large male groups or to groups with more callers.

Large male mating advantage in natterjack toads, Bufo calamita: sexual selection or energetic constraints?

Animal Behaviour, Sep 1, 1992

... Different ecological conditions in the Spanish population, with a more explosive breeding sea... more

Variability in Survival, Growth and Metamorphosis in the Larval Fire Salamander (Salamandra Salamandra): Effects of Larval Birth Size, Sibship and Environment

Herpetologica, Jun 1, 2004

Salamandra salamandra has an unusual mode of reproduction. Females retain eggs in their oviducts ... more Salamandra salamandra has an unusual mode of reproduction. Females retain eggs in their oviducts and give birth to aquatic larvae or, in some populations, to fully metamorphosed juveniles. We investigated how variation in the birth size of larvae of five different sibships of S. salamandra affected larval survival, larval growth rates, time to metamorphosis, and size at metamorphosis under different food and temperature conditions. Maternal effects, via the effect of larval birth size, attenuated throughout development in all environments but still affected metamorphic traits at lower temperatures. Larval developmental time was negatively correlated with larval birth size and positively correlated with size at metamorphosis. After controlling for the effect of larval birth size, broad-sense heritabilities were obtained for residual values of metamorphic traits, indicating that enough genetic variability exists at lower temperature environments and that responses to selection of metamorphic traits are possible. The size at and the time to metamorphosis were phenotypically and genetically correlated. Since both traits presumably affect fitness, genetic dependence between size and time to metamorphosis may act as a constraint on adaptive evolution through antagonistic pleiotropy. Mass-specific growth, time to metamorphosis, and size at metamorphosis were plastic under different temperature and food conditions, but no significant sibship 3 environment interaction was found for any trait. In addition, significant cross-environment correlation for size at metamorphosis with respect to the food gradient indicates low potential for the adaptive evolution of reaction norms to heterogeneous food environments.

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Geographic Variation in Asymmetric Competition: A Case Study with Two Larval Anuran Species

Ecology, Aug 1, 2002

The outcome of interspecific competition may be modulated by a large number of factors, both biot... more The outcome of interspecific competition may be modulated by a large number of factors, both biotic and abiotic. In this paper, we examined experimentally the effects of geographic variation, population density, and abiotic stress on the outcome of interspecific competition between two species of larval anurans. Three different populations of natterjack toad (Bufo calamita) were set to compete with common toad (Bufo bufo) in replicated artificial ponds under different combinations of osmotic stress (freshwater or brackish water) and intraspecific density (high and low). Among the B. calamita populations used, only one of them is sympatric to B. bufo and inhabits a freshwater environment. The two other populations, allopatric to B. bufo, occupy freshwater and brackish water environments, respectively. Survival, length of the larval period, and size at metamorphosis were analyzed at both the specific and the populational interaction levels. Intra-and interspecific competition did occur and generally resulted in a decrease in survival rates, an increase in the duration of the larval period, and a decrease in size at metamorphosis. Water salinity also prolonged the larval period and interacted with intra-and interspecific density, intensifying its effects. Interspecific competition was asymmetric, since B. bufo was competitively superior to B. calamita, causing larger effects on B. calamita than those experienced by B. bufo. However, the three populations of B. calamita showed different competitive effects and responses when they were set to compete with B. bufo. The population sympatric to B. bufo had the stronger competitive effect and response, causing a strong impact on survival, growth, and developmental rate of B. bufo. The allopatric population inhabiting the brackish environment also had a marked effect on B. bufo survival, although only at high density. The other allopatric population only had a significant effect on the size at metamorphosis of B. bufo. The impact of B. bufo on B. calamita was greater for the allopatric populations than for the sympatric one. This pattern suggests that the nature and outcome of ecological interactions are a function of environmental conditions and population history.

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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

Copeia, May 1, 2006

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Contrasting Patterns of Quantitative and Neutral Genetic Variation in Locally Adapted Populations of the Natterjack Toad

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Effect of Predation by Two Species of Sympatric Tadpoles on Embryo Survival in Natterjack Toads (Bufo Calamita)

Herpetologica, 1991

... This last protective property has been con-sidered dynamic, decreasing during de-velopment (B... more

Variation in body size and metamorphic traits of Iberian spadefoot toads over a short geographic distance

Journal of Zoology, Feb 13, 2008

Determinants of geographic variation in body size are often poorly understood, especially in orga... more Determinants of geographic variation in body size are often poorly understood, especially in organisms with complex life cycles. We examined patterns of adult body size and metamorphic traits variation in Iberian spadefoot toad (Pelobates cultripes) populations, which exhibit an extreme reduction in adult body size, 71.6% reduction in body mass, within just about 30 km at southwestern Spain. We hypothesized that size at and time to metamorphosis would be predictive of the spatial pattern observed in adult body size. Larvae from eight populations were raised in a common garden experiment at two different larval densities that allow to differentiate whether population divergence was genetically based or was simply a reflection of environmental variation and, in addition, whether this population divergence was modulated by differing crowding larval environments. Larger adult size populations had higher larval growth rates, attaining larger sizes at metamorphosis, and exhibited higher survival than smaller-sized populations at both densities, although accentuated at a low larval density. These population differences appeared to be consistent once embryo size variation was controlled for, suggesting that this phenotypic divergence is not due to maternal effects. Our results suggest considerable genetic differentiation in metamorphic traits that parallels and may be a causal determinant of geographic variation in adult body size.

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09. Variation in viability during development and hatching success in embryos of the toad Bufo calamita

Herpetological Journal, 1992

Contrasting effects of nitrogenous pollution on fitness and swimming performance of Iberian waterfrog, Pelophylax perezi (Seoane, 1885), larvae in mesocosms and field enclosures

Aquatic Toxicology, 2014

Amphibians are declining worldwide and pollutants have been implicated as a major 24 contributor ... more Amphibians are declining worldwide and pollutants have been implicated as a major 24 contributor to these declines. To understand these declines, many studies have assessed 25 the impact of pollutants on amphibian behavior, however information regarding their 26 effect on locomotor abilities, as well as the intra-specific variation of the tolerance to 27 pollutants, is extremely rare. Further, the majority of studies examining the impact of 28 pollutants on amphibians have been conducted in simplified laboratory settings. Given 29 the complexity of natural systems, determining whether amphibian responses in 30 laboratory studies are generalizable in more realistic natural scenarios is critical. 31 Towards this goal, this study assessed the impact of nitrogenous pollution on survival 32 and fitness-related larval traits (growth, mass and swimming performance) for three 33 populations of the frog Pelophylax perezi, exposed to different degrees of 34 eutrophication in two different and complementary experiments: (1) pond mesocosms, 35 with NH 4 Cl isolated or combined with NaNO 2 and NaNO 3 , and (2) field enclosures 36 placed in natural streams differing in their degree of pollution. 37 For both mesocosm and field enclosure experiments, larval mortality was unaffected by 38 nitrogenous pollution. However, in the mesocosm experiment, exposure to nitrogenous 39 compounds reduced final larvae mass and growth. In contrast, in the enclosure 40 experiment, polluted locations facilitated final mass and growth of surviving tadpoles. 41 Population-level variation in the effect of pollution was observed for final larval mass in 42 the mesocosm but not in the field enclosure experiment. In addition, although 43 nitrogenous compounds in both mesocosm and natural conditions had no direct effect 44 on absolute larval swimming performance, they may impact the viability of larvae by 45 affecting the relationships between growth and the swimming abilities. The differential 46 3 pattern found in the impacts of nitrogenous compounds on larvae of P. perezi when 47 raised in different experimental venues (mesocosms and field conditions) points to the 48 convenience of considering more realistic natural scenarios in assessing the impact of 49 pollutants on amphibians. 50 51 52

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Local Adaptation of an Anuran Amphibian to Osmotically Stressful Environments

Evolution, Aug 1, 2003

Water salinity is an intense physiological stress for amphibians. However, some species, such as ... more Water salinity is an intense physiological stress for amphibians. However, some species, such as Bufo calamita, breed in both brackish and freshwater environments. Because selection under environmentally stressful conditions can promote local adaptation of populations, we examined the existence of geographic variation in water salinity tolerance among B. calamita populations from either fresh or brackish water ponds in Southern Spain. Comparisons were made throughout various ontogenetic stages. A combination of field transplant and common garden experiments showed that water salinity decreased survival probability of individuals in all populations, prolonged their larval period, and reduced their mass at metamorphosis. However, significant population × salinity interactions indicated that the population native to brackish water (Saline) had a higher salinity tolerance than the freshwater populations, suggesting local adaptation. Saline individuals transplanted to freshwater environments showed similar survival probabilities, length of larval period, and mass at metamorphosis than those native to freshwater. This indicates that increased tolerance to osmotic stress does not imply a loss of performance in freshwater, at least during the larval and juvenile phases. Despite the adaptive process apparently undergone by Saline, all populations still shared the same upper limit of embryonic stress tolerance (around 10 g/l), defining a window of salinity range within which selection can act. Significant differences in embryonic and larval survival in brackish water among sibships for all populations suggest the existence of a genetic basis for the osmotic tolerance.

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Elevational and local climate variability predicts thermal breadth of mountain tropical tadpoles

Ecography

The climate variability hypothesis posits that increased environmental thermal variation should s... more The climate variability hypothesis posits that increased environmental thermal variation should select for thermal generalists, while stable environments should favor thermal specialists. This hypothesis has been tested on large spatial scales, such as latitude and elevation, but less so on smaller scales reflective of the experienced microclimate. Here, we estimated thermal tolerance limits of 75 species of amphibian tadpoles from an aseasonal tropical mountain range of the Ecuadorian Andes, distributed along a 3500 m elevational range, to test the climatic variability hypothesis at a large (elevation) and a small (microhabitat) scale. We show how species from less variable thermal habitats, such as lowlands and those restricted to streams, exhibit narrower thermal tolerance breadths than highland and pond‐dwelling species respectively. Interestingly, while broader thermal tolerance breadths at large scales are driven by higher cold tolerance variation (heat‐invariant hypothesis), ...

The timing of thermal acclimation and its adaptive role to face heat impacts. An examination in tropical tadpoles

Phenotypic plasticity of the upper critical thermal limits (CTmax) may be crucial for ectotherms ... more Phenotypic plasticity of the upper critical thermal limits (CTmax) may be crucial for ectotherms when it enables them to respond rapidly to extreme and novel thermal conditions. Although current studies have widely reported on the effect of increasing temperature on the magnitude of the plastic response of ectotherms, little is known about timing of upper thermal acclimation. These temporal components may be adaptive and of major environmental concern, especially under the increasing frequency of episodic heatwaves, predicted by climate change models together with quick habitat conversion. We experimentally studied the temporal acquisition of a greater thermal tolerance by acclimation effect in four species of tropical tadpoles, adjusting the daily variation in the CTmax to an asymptotic function and analyzing its main parameters: asymptotic CTmax (CTmax[?]) and acclimation rate of the CTmax (K), under two realistic daily thermal fluctuations: mean daily fluctuation (MF) and extreme hot fluctuation (HF), and under the corresponding constant temperatures, mean constant (MC) and hot constant (HC). The rate of acclimation was higher for constant and hotter conditions, with which the CTmax[?] was reached in a shorter time under these conditions. The time to achieve the CTmax[?] was between one and three days depending on the treatment of acclimation and species. Plastic responses are species-specific and appear to be adaptive to the level of thermal heterogeneity of their breeding environment. Engystomops pustulosus tadpoles, that develop in hot and thermally variable temporary pond had the greatest acclimation. This suggests that species exposed naturally to extreme heat events may exhibit the highest plastic response in acclimation to upper thermal tolerances.

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Miguel Tejedo

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