B. Vanhooydonck

What determines dewlap diversity in Anolis lizards? An among-island comparison

Animal signalling systems are extremely diverse as they are under different, often conflicting, selective pressures. A classic textbook example of a diverse signal is the anoline dewlap. Both at the inter‐ and intraspecific levels, dewlap size, colour, shape and pattern vary extensively. Here, we attempt to elucidate the various factors explaining the diversity in dewlap size and pattern among seven Anolis sagrei populations from different islands in the Bahamas. The seven islands differ in the surface area, number and kind of predators, sexual size dimorphism and Anolis species composition. In addition, we investigate whether selective pressures acting on dewlap design differ between males and females. Whereas dewlap pattern appears to serve a role in species recognition in both sexes, our data suggest that relative dewlap size is under natural and/or sexual selection. We find evidence for the role of the dewlap as a pursuit‐deterrence signal in both males and females as relative dewlap size is larger on islands where A. sagrei occurs sympatrically with predatory Leiocephalus lizards. Additionally, in males relatively large dewlaps seem to be selected for in a sexual context, whereas in females natural selection, for instance by other predators than Leiocephalus lizards, appears to constrain relative dewlap size.

Relationships between hormones, physiological performance and immunocompetence in a color-polymorphic lizard species, Podarcis melisellensis

Species with alternative phenotypes offer unique opportunities to investigate hormone-behavior relationships. We investigated the relationships between testosterone, corticosterone, morphology, performance, and immunity in a population of lizards (Podarcis melisellensis) which exhibits a color polymorphism. Males occur in three different color morphs (white, yellow, orange), providing an opportunity to test the idea of morphs being alternative solutions to the evolutionary challenges posed on the link between hormones, morphology, performance, and immunity. Morphs differed in bite force capacity, with orange males biting harder, and in corticosterone levels, with yellow males having lower levels than orange. However, morphs did not differ in testosterone levels or in the immunological parameters tested. At the individual level, across morphs, testosterone levels predicted size-corrected bite force capacity, but no relation was found between hormone levels and immunity. Our results do not support the testosterone-based polymorphism hypothesis and reject the hypothesis of a trade-off between testosterone and immunity in this species, but provide a mechanistic link between testosterone and a sexually selected performance trait.

Is the whole more than the sum of its parts? Evolutionary trade-offs between burst and sustained locomotion in lacertid lizards

Trade-offs arise when two functional traits impose conflicting demands on the same design trait. Consequently, excellence in one comes at the cost of performance in the other. One of the most widely studied performance trade-offs is the one between sprint speed and endurance. Although biochemical, physiological and (bio)mechanical correlates of either locomotor trait conflict with each other, results at the whole-organism level are mixed. Here, we test whether burst (speed, acceleration) and sustained locomotion (stamina) trade off at both the isolated muscle and whole-organism level among 17 species of lacertid lizards. In addition, we test for a mechanical link between the organismal and muscular (power output, fatigue resistance) performance traits. We find weak evidence for a trade-off between burst and sustained locomotion at the whole-organism level; however, there is a significant trade-off between muscle power output and fatigue resistance in the isolated muscle level. Variation in whole-animal sprint speed can be convincingly explained by variation in muscular power output. The variation in locomotor stamina at the whole-organism level does not relate to the variation in muscle fatigue resistance, suggesting that whole-organism stamina depends not only on muscle contractile performance but probably also on the performance of the circulatory and respiratory systems.

No trade-off between sprinting and climbing in two populations of the lizard **Podarcis hispanica**

Biomechanical reflections suggest that lizards that have specialized in running should differ in parts of their morphological design from lizards that have specialized in climbing. Moreover, adaptation in one direction may conflict with performance in the other. We tested this assumed trade-off by measuring climbing and running performance in two subspecies of the Mediterranean lizardPodarcis hispanica. One subspecies,P. h. atrata, inhabits a number of small islets near the Spanish coast. It is mainly ground dwelling. The other subspecies,P. h. hispanica, was sampled on the mainland of Spain. It frequently occupies vertical elements within its habitat. Our data do not support the notion of a trade-off between both types of locomotion. Individuals ofP. h. hispanicaboth run and climb faster than those ofP. h. atrata. There is no difference between subspecies in ability to cling onto tilted substrates. Predictions on the morphology of both subspecies, inspired by biomechanical arguments, are not supported by our measurements.

Genetic divergence among sympatric colour morphs of the Dalmatian wall lizard (Podarcis melisellensis)

If alternative phenotypes in polymorphic populations do not mate randomly, they can be used as model systems to study adaptive diversification and possibly the early stages of sympatric speciation. In this case, non random mating is expected to support genetic divergence among the different phenotypes. In the present study, we use population genetic analyses to test putatively neutral genetic divergence (of microsatellite loci) among three colour morphs of the lizard Podarcis melisellensis, which is associated with differences in male morphology, performance and behaviour. We found weak evidence of genetic divergence, indicating that gene flow is somewhat restricted among morphs and suggesting possible adaptive diversification.

Sex‐specific differences in ecomorphological relationships in lizards of the genus Gallotia

Summary 1. Males and females often differ from one another in phenotypic traits due to differential investment in traits relevant to the fitness of each sex. However, how differences in sexually dimorphic traits affect ecologically relevant performance traits and whether these are correlated with variation in ecology remains poorly understood. 2. Here, we test the co-evolution of head shape, bite force capacity and diet in male and female lizards (Gallotia) from the Canary Islands, known to be sexually dimorphic. We collected data on bite force and head size and shape for both sexes of all seven extant species on all seven islands of the archipelago (ten evolutionary-independent lineages). Moreover, we collected diet data for five out of the seven species (eight lineages). 3. Our results show that the evolution of head morphology is associated with the evolution of bite force in both sexes. However, only in females is the evolution of head morphology and bite force associated with the evolution of diet. In males, head morphology and bite force are decoupled from the evolution of diet. In conjunction with the male head shape characterized by a broad rostrum, this suggests that head shape and bite force may be evolving principally under sexual selection in males. 4. Our data thus suggest that head morphology and associated functional traits may evolve under different selective pressures in the two sexes.

Deterring predators, daunting opponents or drawing partners? Signaling rates across diverse contexts in the lizard Anolis sagrei

Although the visual display behavior in Anolis lizards has received ample attention, the function of dewlap extensions (DE), push-ups (PU), and head-nods (HN) in general, and in Anolis sagrei in particular, remains highly equivocal. Therefore, our primary goal was to quantify the display rates of these visual signal types (DE, PU, and HN) in a variety of contexts, using A. sagrei as study species. To our knowledge, this is the first study to test individuals of both sexes in a repeated-measures design across multiple contexts, including predator, non-predator and social interactions (mirror, male–male, male–female, female–male). We found that males have an overall higher signaling rate than females across all contexts. In addition, we found that lizards of both sexes exhibited higher display rates in the presence of conspecifics than when confronted with a predator or non-predator, suggesting that DE, PU, and HN function in intraspecific communication, not in predator deterrence. Whereas females did not significantly raise display rates in a consexual and heterosexual context with respect to subject-alone context, males did. The PU signal type only appears to play a major role for A. sagrei males during aggressive encounters. During heterosexual interactions, increased frequencies of all signal types suggest that DE, PU, and HN are essential for male courtship. Finally, we suggest that intersexual selection is probably a driving force for frequency-related dewlap use in both sexes. In contrast, pronounced intersexual differences were detected for PU and HN rates within a social context.

Characterization of polymorphic microsatellite markers in the Dalmatian wall lizard Podarcis melisellensis (Squamata: Lacertidae)

We describe polymerase chain reaction primers and amplification conditions for 13 highly polymorphic microsatellite DNA loci isolated from the Dalmatian wall lizard, Podarcis melisellensis. The number of alleles per locus ranged from 12 to 41, with levels of observed heterozygosity between 0.62 and 0.94. Most of these loci were successfully cross‐amplified in the closely related species P. sicula, but levels of polymorphism were always lower.