Emilio Civantos

COEVOLUTION OF COLOR PATTERN AND THERMOREGULATORY BEHAVIOR IN POLYMORPHIC PYGMY GRASSHOPPERS TETRIX UNDULATA

Abstract Ectothermic organisms, such as insects and reptiles, rely on external heat sources to control body temperature and possess physiological and behavioral traits that are temperature dependent. It has therefore been hypothesised that differences in body temperature resulting from phenotypic properties, such as color pattern, may translate into selection against thermally inferior phenotypes. We tested for costs and benefits of pale versus dark coloration by comparing the behaviors (i.e., basking duration and bouts) of pygmy grasshopper (Tetrix undulata) individuals exposed to experimental situations imposing a trade‐off between temperature regulation and feeding. We used pairs consisting of two full‐siblings of the same sex that represented different (genetically coded) color morphs but had shared identical conditions from the time of fertilization. Our results revealed significant differences in behavioral thermoregulation between dark and pale individuals in females, but not in males. Pale females spent more time feeding than dark females, regardless of whether feeding was associated with a risk of either hypothermia or overheating. In contrast, only minor differences in behavior (if any) were evident between individuals that belonged to the same color morph but had been painted black or gray to increase and decrease their heating rates. This suggests that the behavioral differences between individuals belonging to different color morphs are genetically determined, rather than simply reflecting a response to different heating rates. To test for effects of acclimation on behaviors, we used pairs of individuals that had been reared from hatchlings to adults under controlled conditions in either low or high temperature. The thermal regime experienced during rearing had little effect on behaviors during the experiments reported above, but significantly influenced the body temperatures selected in a laboratory thermal gradient. In females (but not in males) preferred body temperature also varied among individuals born to mothers belonging to different color morphs, suggesting that a genetic correlation exists between color pattern and temperature preferences. Collectively, these findings, at least in females, are consistent with the hypothesis of multiple‐trait coevolution and suggest that the different color morphs represent alternative evolutionary strategies.

Chemical ornaments of male lizards Psammodromus algirus may reveal their parasite load and health state to females

Evidence for parasite-mediated sexual selection has been found in many species that use visual ornaments to attract females. However, in many animals, variation in female responses to scents of parasitized males suggests that parasitic infections might also affect information conveyed by pheromones (i.e., chemical ornaments). Thus, pheromones might also function in parasite-mediated sexual selection. We show here that female lizards Psammodromus algirus responded differently to femoral gland secretions of males according to the parasite load and health of these males. Scents of healthier males elicited more tongue flicks (a chemosensory behavior) by females, suggesting that these scents were more attractive. Chemical analyses showed that parasite load and the T-cell-mediated immune response were related to the variability in the proportions of some lipids in secretions of males. Further trials testing the chemosensory responses of females to chemical standards indicated that females actually discriminated the chemicals related to males’ health from other chemicals found in secretions. We suggest that these chemical ornaments may provide reliable information on the health and degree of parasitic infection of a male.

Determinants of survival in juvenile Psammodromus algirus lizards

Abstract Theories posit that the relative mortality rate of adults and juveniles is a major determinant of population dynamics and life history evolution. Moreover, differential survival of pre-reproductive individuals may be an important source of variation in lifetime reproductive success, and characters that influence survival of juveniles are likely to be under strong selection. We examined survival from hatching to maturity in a natural population of Psammodromus algirus lizards using data from a capture-mark-recapture study. We found that mortality from hatching to maturity was high: only 8% of males and 14% of females that hatched in 1996 survived the entire study period until maturity in spring 1998. The probability of survival was 75% during both the first and second overwinter periods when lizards were inactive most of the time, and about 25% during their first spring to autumn activity season. Our analyses further revealed significant associations between survival and snout-vent length, body condition, sex and microhabitat use. However, the relationship between survival and morphological characters varied among time periods, presumably because the sources of mortality during the activity season were different from those during hibernation. The association between survival and body condition also varied within time periods, both between large and small individuals and between the two sexes. This suggests that the relative importance of different selective agents may change during the life of individuals and vary between males and females due to differences in body size and behaviour.

Body Size and Microhabitat Affect Winter Survival of Hatchling Psammodromus algirus Lizards

To examine factors related to overwinter survival of Psammodromus algirus hatchlings, we performed a capture-mark-recapture study of a cohort of hatchlings. In this work, we examine the effects of body size, vegetation structure of the home range, tail condition, sex, and estimated hatching date on hatchling survivorship to the next spring. Results of a logistic regression analysis showed that survival was associated with larger body size (SVL), higher cover, and earlier hatching date. Tail condition and sex were not associated with overwinter survivorship.

Can we predict habitat quality from space? A multi-indicator assessment based on an automated knowledge-driven system

Abstract There is an increasing need of effective monitoring systems for habitat quality assessment. Methods based on remote sensing (RS) features, such as vegetation indices, have been proposed as promising approaches, complementing methods based on categorical data to support decision making. Here, we evaluate the ability of Earth observation (EO) data, based on a new automated, knowledge-driven system, to predict several indicators for oak woodland habitat quality in a Portuguese Natura 2000 site. We collected in-field data on five habitat quality indicators in vegetation plots from woodland habitats of a landscape undergoing agricultural abandonment. Forty-three predictors were calculated, and a multi-model inference framework was applied to evaluate the predictive strength of each data set for the several quality indicators. Three indicators were mainly explained by predictors related to landscape and neighbourhood structure. Overall, competing models based on the products of the automated knowledge-driven system had the best performance to explain quality indicators, compared to models based on manually classified land cover data. The system outputs in terms of both land cover classes and spectral/landscape indices were considered in the study, which highlights the advantages of combining EO data with RS techniques and improved modelling based on sound ecological hypotheses. Our findings strongly suggest that some features of habitat quality, such as structure and habitat composition, can be effectively monitored from EO data combined with in-field campaigns as part of an integrative monitoring framework for habitat status assessment.

Social aggregation behaviour in the North African amphisbaenian Trogonophis wiegmanni

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.

Sexual Dimorphism in the North African Amphisbaenian Trogonophis wiegmanni

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.

STRUCTURE OF A POPULATION OF THE AMPHISBAENIAN TROGONOPHIS WIEGMANNI IN NORTH AFRICA

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.

Developmental instability and immune function in colour polymorphic pygmy grasshoppers

Random left minus right deviations from symmetry in otherwise bilaterally symmetric traits may arise due to developmental instability in response to environmental stress. Here we test for variation in developmental instability, measured as asymmetry of (femur) size, among individuals belonging to four different genetically encoded colour morphs of the pygmy grasshopper Tetrix undulata (Sow.) (Orthoptera: Tetrigidae). Such a difference is expected under the hypotheses that perturbed growth and development and concomitant morphological asymmetry may result from exposure to unfavourable temperatures or costs associated with melanization, or reflect a by-product of past disease in individuals with poor immune responsiveness. Results from mixed model two-way ANOVAs uncovered no statistically significant directional asymmetry in femur size, whereas non-directional asymmetry was significant in each of the four different colour morphs. The degree of intraindividual, interlateral variance in femur size varied significantly among individuals belonging to different colour morphs, being considerably higher in the black morph, which also suffers the greatest risk of overheating, compared to the brown, striped and grey morphs. Asymmetry in femur size was not associated with one measure of immune responsiveness, the encapsulation response of individuals experimentally implanted with a novel antigen consisting of a nylon mono-filament. These results are consistent with the notion that individual pigmentation pattern may indirectly influence developmental instability and morphological asymmetry, via the effects of coloration on body temperature.

Diet selection by the threatened Chafarinas' skink Chalcides parallelus in North Africa

Abstract Studies of diet suggest that skinks are opportunistic predators. However, there is little information on actual diet preferences because most studies do not evaluate the availability of prey in the environment. We analysed the diet selection of a population of the little-known skink Chalcides parallelus from the Chafarinas Islands in North Africa. This species is considered highly threatened, and diet selection is an important basic point on which to support the design of conservation plans. We specifically examined diet estimated from faecal material collected from live skinks, and compared diet with availability of invertebrates in the microhabitats used by skinks (under rocks and in the leaf litter). Results indicated that the diet of C. parallelus skinks consisted of the same types of invertebrates that are more commonly found in the habitat such as beetles (54.8% of prey), cockroaches, spiders and snails. This diet could be considered generalist, and probably opportunistic. However, the comparison of proportions of prey types in the diet and those available in the habitat revealed that C. parallelus did not eat prey at random, but selected some particular prey types (beetles, cockroaches, and pseudoscorpiones) while others (ants and isopods) were consumed less than expected by their abundance. Invertebrates available and consumed did not differ in size, but skinks consumed beetles that were smaller than the average size of those available. We discuss how diet preferences could be due to selection of the more profitable or easily captured prey.