Nuria Polo-Cavia

Abstract: Sexual signals can be evolutionarily stable if they are honest and condition-dependent or costly to the signaler. One possible cost is the existence of a trade-off between maintaining physiological health and elaboration of ornaments, such that only healthier individuals may afford to produce more elaborate sexual displays. We analyzed the relationship between head coloration and health state of Trachemys scripta elegans turtles. Results showed that turtles with a higher immune response and with a higher body condition had postorbital red patches with brighter coloration with higher values of long-wavelength reflectance (i.e., more reddish). Similarly, turtles with a higher immune response and with a lower heterophil/lymphocyte (H/L) ratio had chin yellow stripes with darker coloration with higher values of medium wavelengths (i.e., more yellowish). These relationships suggest that the health state of T. scripta elegans turtles is reflected by the colorful skin patches and stripes of the head. Characteristics of coloration did not differ between sexes, suggesting that this visual signal may be used by both sexes in intrasexual and intersexual communication. Because many other turtle species have similar colorful patches, it is likely that coloration may have a still unexplored significant role in sexual selection in many turtles.

Abstract: Alien predators are one of the major causes for rapid decline and extinction of native species, because they often create novel ecological contexts in which the antipredatory responses of native organisms are no longer fit. Although larval amphibians are often capable of innately responding to chemical cues from local predators through changes in morphology and behaviour, naïve tadpoles generally cannot recognise introduced predators with which they have not shared an evolutionary past. However, in a few documented cases, aquatic organisms have been observed to alter morphology or behaviour in response to alien predators. Such a response may have evolved as adaptive recognition, increasing their repertoire of innate responses to include the novel predator, or may have evolved as the prey's ability to learn new threats by association with conspecific alarm cues. The red swamp crayfish, Procambarus clarkii, is a harmful invasive species in aquatic systems worldwide, causing great ecological impact on native amphibian populations during the last decades through intense predation of eggs and tadpoles. We demonstrate that naïve tadpoles of the western spadefoot toad, Pelobates cultripes, are not capable of innately recognising water-borne predator cues from the red swamp crayfish. Nevertheless, we demonstrate that P. cultripes tadpoles can learn to recognise the cues of the invasive predatory crayfish as a threat when they are exposed to predator cues combined with conspecific alarm cues. Finally, we show that tadpoles conditioned by joint exposure to crayfish and alarm cues enjoy higher survival during predation trials with invasive crayfish. Learning to recognise a newly introduced predator through association with conspecific alarm cues may allow successful generalisation of antipredatory responses by tadpoles. This cognitive ability of tadpoles may contribute to reduce their vulnerability to alien predators and soothe the impact of invasions in natural populations.

Abstract: Righting behavior of aquatic turtles might be subject to coadaptation pressures between preferred basking temperature and locomotion, given that it is mainly performed on land and may critically determine the survival of turtles. We analyzed the effect of body temperature (Tb) on righting performance of two species of freshwater turtles, the endangered native Spanish terrapin (Mauremys leprosa), and the red-eared slider (Trachemys scripta elegans), an introduced invasive species that is displacing native turtles in the Iberian Peninsula. Interspecific differences in morphology, basking requirements and behavioral responses have been found between Spanish terrapins and introduced sliders. Therefore, we hypothesized that Tb might differentially affect righting behavior of these two turtle species. We found a clear effect of Tb on righting response of both M. leprosa and T. scripta, with the performance enhanced at the preferred basking temperature of each turtle species. These results suggest that righting might be coadapted to preferred basking temperature in freshwater turtles. Also, M. leprosa required longer times to right on average than T. scripta, which denotes a higher efficiency of introduced sliders at righting performance. These interspecific behavioral asymmetries in righting performance between native and exotic turtles might contribute to the greater competitive ability of introduced T. scripta, favoring the expansion of exotic sliders in the new environments in which they are introduced, in detriment to native Spanish terrapins.

Abstract: Thermoregulatory behavior and feeding status are strongly related in ectotherms. A trade-off between maintenance of energy balance and digestion efficiency has been recently proposed to affect thermoregulation in these animals. On the other hand, competition for basking sites has been described between Iberian turtles and the introduced red-eared slider (Trachemys scripta elegans). T. scripta negatively interferes with basking behavior of native turtles and benefits from a greater capacity to retain body heat, which may likely result in thermoregulatory advantages for the introduced sliders. Consequently, complex effects and alterations in metabolic rates of native turtles might derive from a deficient basking behavior. We compared the basking requirements of the endangered native Spanish terrapin (Mauremys leprosa) and those of the introduced red-eared slider, analyzing the upper set point temperature (LISP) (defined as the body temperature at which basking ceased) of both native and introduced turtles, under feeding and fasting conditions. We found higher values of LISP in the native species, and a reduction of this temperature associated with food deprivation in the two turtle species. This adjustment of thermoregulatory behavior to the nutritional status found in freshwater turtles suggests that ectotherms benefit from metabolic depression as an adaptive mechanism to preserve energy during periods of fasting. However, a reduction in metabolic rates induced by competition with sliders might lead M. leprosa to a prolonged deficiency of their physiological functions, thus incurring increased predation risk and health costs, and ultimately favoring the recession of this native species in Mediterranean habitats. (C) 2012 Elsevier Inc. All rights reserved.

Abstract: Sexual dimorphism in size or shape is common in many reptile species. Amphisbaenians are morphologically specialized for a fossorial life, which might constrain the evolution of sexual dimorphism. This might explain why some amphisbaenian species, but not others, show some type of sexual dimorphism. To understand the differential occurrence of sexual dimorphism in amphisbaenians, studies on a wide number of species belonging to different families and inhabiting different ecological conditions are needed. We measured several morphological variables in a population of the amphisbaenian Trogonophis wiegmanni, a representative of the little-studied family Trogonophidae from North Africa. Results show that males and females have similar body size; but for individuals of similar size, males are heavier, have longer tails, and have larger heads than do females. These differences might be explained by sexual selection, if males with larger heads had advantages in intrasexual contests, or by sexual diet differences. However, most ecological and behavioral aspects of this and other amphisbaenian species remain poorly known, thereby leaving unresolved which selective pressures are responsible for the sexual dimorphism that was evident in this species.

Abstract: También conocido como tortuga de orejas rojas debido a su característica mancha postorbital, el galápago de Florida (Trachemys scripta elegans) es un quelonio originario del sureste de Estados Unidos y noreste de México que ha sido introducido en numerosas regiones del mundo, especialmente en países mediterráneos, como consecuencia de su liberación incontrolada. Durante las últimas décadas, un gran número de juveniles ha sido importado en masa como parte del comercio de mascotas, lo que ha dado lugar a frecuentes introducciones en el medio natural. El galápago de Florida se ha establecido también en la península Ibérica, donde coloniza todo tipo de masas de agua gracias a su gran capacidad de adaptación. Hoy en día existen poblaciones autónomas de mayor o menor densidad en diversas marismas y humedales de la franja litoral, así como en puntos dispersos del interior . Algunas observaciones indican que este quelonio compite con los galápagos autóctonos ibéricos: el europeo (Emys orbicularis) y el leproso (Mauremys leprosa). La situación de estas dos especies nativas es preocupante, sobre todo la del escaso galápago europeo. El galápago leproso tiene un área de distribución mayor y abunda más en el suroeste ibérico, aunque ha sufrido un considerable receso debido sobre todo a la destrucción del hábitat y a la presión antrópica. La competencia a escala local con los galápagos exóticos introducidos podría estar empeorando el estado de las poblaciones autóctonas remanentes. Si bien la naturaleza de las interacciones entre especies no está clara, algunas ventajas potenciales del galápago de Florida sobre las especies nativas pueden estar contribuyendo a la expansión del invasor en las regiones mediterráneas. Se han citado una mayor tolerancia a la contaminación y a la presencia humana, una madurez sexual más temprana y una descendencia mayor. Además, el galápago de Florida se muestra activo a temperaturas inferiores del agua, por lo que puede comenzar antes su actividad anual, alcanza tallas superiores a las de los galápagos autóctonos y tiene una dieta más variada. Es probable que exista competencia por los recursos tróficos, los lugares de asoleamiento o los de nidificación, pues tanto los galápagos nativos como los americanos consumen materia animal de manera constante, dedican gran parte del tiempo a asolearse y coinciden en las épocas de reproducción. Pero el hecho de que el galápago de Florida tenga su origen en un medio especialmente competitivo �la coexistencia de numerosas especies competidoras de galápagos en sintopía es habitual en muchos ecosistemas de Norteamérica� podría dotarle de ciertas habilidades ventajosas sobre los galápagos autóctonos, adaptados a ambientes de escasa o nula competencia, hasta el punto de hacerles abandonar recursos fundamentales �alimento y lugares de asoleamiento� o de llegar a desplazarles hacia áreas alternativas menos favorables.

Abstract: Amphisbaenians are a group of reptiles specialized for a fossorial life, which makes the study of their peculiar biological and ecological adaptations difficult. The population biology of amphisbaenians is almost unknown. We described the seasonal variation in the size, age, and sex structure of a population of the amphisbaenian Trogonophis wiegmanni from the Chafarinas Islands, in North Africa. We specifically described body size (length and weight), frequency distribution of newborn and older juvenile individuals and adults, sex ratio of adults (which did not differ from a 1:1 ratio), and proportion of juveniles and newborn individuals in the population. The results indicated that T. wiegmanni is a viviparous species that delays reproduction until at least 2.5 yr, that almost half of adult females do not reproduce every year, and that females have a very small brood size (i.e., reproductive females give birth to a single juvenile at the beginning of autumn). We also used our data to infer growth and survival of juveniles, suggesting that mortality of newborn individuals is low. There are many aspects of the population biology of amphisbaenians that remain unknown and further studies are clearly needed.

Abstract: The ecology and behaviour of Amphisbaenians is poorly known due to their fossorial habits. However, amphisbaenians are often found under rocks where they thermoregulate, and probably engage in social interactions. We describe aggregations under rocks in a North African population of the little studied amphisbaenian Trogonophis wiegmanni. These observations could be used to make initial inferences about the social behaviour of this amphisbaenian. Results showed that amphisbaenians were sometimes found in pairs under the same rock. However, these aggregations were not random. Adult males were only found together with adult females, but we did not find pairs of adult males or adult females. This might suggest that there is intra-sexual intolerance, and that adult individuals of the same sex do not occupy the same rock space. Pairs of adults were more frequently found in spring than in autumn, coinciding with the mating season. Also, juvenile individuals were often found together with an adult, but juveniles tended to be more often with an adult female than with an adult male. This might indicate that juveniles are allowed to remain with their parents until they are older, which might enhance offspring fitness by providing access to high-quality habitats.

Abstract: Dado el interés científico y de conservación de la culebrilla mora, y con el objetivo de desarrollar un programa de conservación y gestión, el presente estudio examina la distribución detallada y abundancia relativa de la especie en las Islas Chafarinas, y constituye la primera evaluación del estado de conservación de sus poblaciones.

Abstract: The red-eared slider (Trachemys scripta elegans) is a worldwide highly invasive species, currently introduced in most freshwater habitats as a consequence of massive pet trade. In the Iberian Peninsula, this species is competing with and displacing the endangered native Spanish terrapin (Mauremys leprosa). Sliders are considered environmentally-aggressive turtles, capable of threatening or biting other individuals during competitive activities such as feeding. We hypothesized that agonistic behavior of introduced sliders against native terrapins might negatively affect the feeding efficiency of M. leprosa. We compared food ingestion of turtles and aggressive interactions during feeding, under situations of conspecific and heterospecific competition. The amount of food ingested by native and introduced turtles was similar under conspecific competition, but T. scripta ingested a greater percentage of food supplied under heterospecific competition. Also, introduced sliders initiated most of the aggressions observed during feeding activity, and aggression was more frequently directed to heterospecifics. Our results suggest a more aggressive and competitive behavior of introduced T. scripta in vying for food resources, which might contribute to explain the observed displacement of native populations of M. leprosa.

Abstract: Many authors have addressed the relationship between body condition and ecological parameters in a wide range of studies, suggesting a better fitness in those individuals with higher values of body condition. However, body size and body condition of individuals can vary significantly at the intraspecific level between geographic locations, which is usually explained by phenotypic plasticity or local adaptation. We suggest that a higher body condition per se might not be a good indicator of physiological health status, particularly when comparing populations inhabiting places with different levels of habitat alteration. We examined two populations of the western pond turtle Emys marmorata in the northern part of California's Central Valley, and found that individuals inhabiting a water pollution control plant located on the valley floor had significantly larger body size and higher body condition than those inhabiting an unaltered natural habitat in the foothills. However, turtles from the water pollution control plant did not show a better health status, estimated by comparisons between two immune system variables: T-cell-mediated immune response and heterophil/lymphocyte ratio. Parameters such as body size and body condition might be misleading indicators of health condition, particularly when they are used to estimate health status of populations from habitats with different levels of alteration. We emphasize the importance of using physiological methods in assessing the conservation state of wildlife populations, rather than relying on biometric indices that might miss important effects of alteration.

Abstract: The red-eared slider (Trachemys scripta elegans) is currently introduced in many Mediterranean countries, where it behaves as an invasive species that competes and displaces native populations of the endangered Spanish terrapin (Mauremys leprosa). However, the nature of competitive interactions is relatively unknown. During basking activity, factors like greater body size or pre-existing behavioral adaptations to an original habitat with higher levels of interspecific competition might confer competitive advantages to introduced T. scripta with respect to native terrapins. We hypothesized that competition for basking places with the introduced T. scripta might negatively affect the efficiency of basking and thermoregulation of the native Spanish terrapin. We experimentally analyzed the basking activity of T. scripta and M. leprosa under occasional and long-term situations of intra- and inter-specific competition. Native M. leprosa subjected to interspecific competition reduced their basking activity, basked for shorter periods than T. scripta, and avoided basking stacked with the exotic turtles. These results suggested the displacement from the basking sites of the native terrapin by the introduced T. scripta. The decreased basking activity of native M. leprosa when competing directly for basking places with introduced sliders may lead native terrapins to a loss in the efficiency of physiological functions related to ineffective thermoregulation, such as digestion or locomotor performance, thus favoring the expansion of the invasive species.

Abstract: The impact of alien predators on prey populations is well known by conservation biologists, but little attention has been paid to the negative effects that the introduction of exotic predators may have on native predators through competition for food. In the Iberian Peninsula, the red-eared slider, Trachemys scripta elegans, and other exotic freshwater turtles have been introduced, competing and displacing the native endangered terrapins (the European pond turtle, Emys orbicularis, and the Spanish terrapin, Mauremys leprosa). Although the nature of competitive interactions remains unclear, direct competition for food is likely to occur. Both native and invasive freshwater turtles are common predators of amphibian tadpoles. Naive amphibian tadpoles are known to recognize and respond to local predators with no prior experience, but tadpoles might not recognize new predatory species, since they have not shared a long evolutionary history with them. We examined the ability of four species of Iberian anuran tadpoles to recognize and respond to chemical cues from invasive and native freshwater predatory turtles. Three of the four tadpole species tested reduced their swimming activity when cues from native turtles were present in water, but not when cues belonged to exotic turtles. This inability of tadpole prey to respond innately to chemicals from introduced predatory turtles might be one of the causes that explains the displacement of native populations of Iberian terrapins by invasive exotic turtles, and may help clarify why alien predators sometimes prosper better in new habitats than locally adapted predators. (C) 2010 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd. All rights reserved.

Abstract: In the Iberian Peninsula, the red-eared slider (Trachemys scripta elegans) is an introduced invasive species that is displacing the endangered native Spanish terrapin (Mauremys leprosa). However, the nature of competitive interactions is relatively unclear. In temperate zones, mechanisms for maximizing heat retention could be selectively advantageous for aquatic turtle species, since individuals usually lose the heat gained from basking very rapidly when entering the water. We hypothesized that interspecific differences in morphology, and thus, in heating and cooling rates, might confer competitive advantages to introduced T. scripta. We compared the surface-to-volume ratios of both, introduced and native turtles, basing on biometric measures, and their effects on thermal exchange rates. T. scripta showed a more rounded shape, a lower surface-to-volume ratio and a greater thermal inertia, what facilitates body heat retention and favors the performance of activities and physiological functions such as foraging or digestion, thus aggravating the competition process with native turtles in Mediterranean habitats.

Abstract: The red-eared slider (Trachemys scripta elegans) is an introduced invasive species in many Mediterranean countries that is displacing the populations of native endangered Spanish terrapins (Mauremys leprosa). However, it is relatively unknown how potential competitive interactions could be taking place. In many freshwater turtles, semiochemicals from different glands might facilitate species and sex recognition. We hypothesized that chemosensory detection of competitor species might affect space use and habitat selection by freshwater turtles. We analyzed whether T. scripta and M. leprosa turtles recognized chemical cues from male and female conspecifics and heterospecifics in water. We compared time spent by turtles in clean water pools vs. water pools containing the different chemical stimuli. Introduced T. scripta did not avoid nor prefer water pools with chemical stimuli of native M. leprosa terrapins, which might favor the expansion of the invasive species. In contrast, M. leprosa preferred water with chemical stimuli of conspecifics and avoided water with chemical cues of T. scripta, which suggests that chemical cues could be used by native M. leprosa to avoid water pools occupied by introduced T. scripta. We suggest that this avoidance behavior of native M. leprosa may be one of the causes that contribute to the observed displacement of their populations by invasive T. scripta.

Abstract: Desde que en 1925 el maestro John Thomas Scopes protagonizara en Dayton (Tennessee) uno de los juicios más controvertidos del siglo XX, conocido como �juicio del mono�, la teoría de Darwin sobre la evolución de las especies inundó las escuelas de los Estados Unidos. A pesar de que la ley Butler �que prohibía la enseñanza de la teoría evolutiva en todos los centros educativos públicos del estado de Tennessee y que entró en vigor ese mismo año� no fuera derogada hasta 1967 sin haberse aplicado en cuatro décadas, y de que Scopes fuera condenado por transgredirla a una multa de 100 dólares cuyo pago nunca llegó a efectuarse, el juicio abrió una brecha en el búnker religioso de la educación que acabó por dar paso a la libre difusión de las teorías evolucionistas en las aulas. Desde entonces, los intentos de los representantes del literalismo bíblico para lograr la enseñanza de la creación del Génesis en la clase de Ciencias Naturales han ido sucediéndose con frenética insistencia hasta culminar en la aparición de su más elaborada estrategia: el actual movimiento del diseño inteligente (DI).

Abstract: En 1932 el biólogo norteamericano Sewall Wright presentó su diagrama del paisaje adaptativo con el propósito de describir las condiciones ideales que dan lugar a la evolución. Desde entonces, su teoría evolutiva de los �equilibrios cambiantes� y el propio diagrama han estado rodeados de controversia. El paisaje adaptativo de Wright no fue bien acogido entre los evolucionistas británicos. J. B. S. Haldane se mostró escéptico, R. A. Fisher lo consideró imperfecto y, junto con el renombrado genetista E. B. Ford, aportó evidencias empíricas en su contra. Sin embargo, y a pesar de las numerosas críticas, el paisaje adaptativo de Wright es considerado en la actualidad como el más influyente modelo heurístico de la biología evolutiva. eVOLUCI�N 3(2): 87-93 (2008).

Abstract: The nature of competitive interactions between native and introduced invasive species is unclear. In the Iberian Peninsula, the introduced red-eared slider (Trachemys scripta elegans) is an invasive species that is competing and displacing the endangered native Spanish terrapin (Mauremys leprosa). We hypothesized that interspecific differences in antipredatory behavior might confer competitive advantages to introduced T. scripta. We examined whether interspecific differences in responses to predation risk affect the time that turtles remained hidden in the shell before using an active escape to water. Both turtle species adjusted hiding times by balancing predation threat, microhabitat conditions and the costs of remaining hidden. However, introduced T. scripta showed longer hiding times before escaping than native M. Leprosa, which, in contrast, switched from waiting hidden in the shell to escape to deep water as soon as possible. These interspecific differences might result from the risk of facing different types of predators in different microhabitats (land vs. water) in their original habitats. However, in anthropogenically altered habitats where predators have been greatly reduced, T. scripta may avoid potential costs of unnecessary repeated escape responses to water (e.g. interruption of basking). These behavioral asymmetries could contribute to the greater competitive ability of introduced T. scripta within anthropogenically disturbed environments.