Melanin‐based coloration is related to parasite intensity and cellular immune response in an urban free living bird: the feral pigeon Columba livia

Melanin‐based coloration is widespread among vertebrates, but the adaptive function of this trait remains poorly known. Recently, it has been shown that differently coloured individuals have different abilities to cope with parasites. This correlation between melanin‐based coloration and immunity could be explained by the pleiotropic effects of genes coding for melanin pigmentation on the immune system (‘genetic link’ hypothesis) but also because differently coloured individuals may exploit alternative habitats varying in parasite exposure, which leads to different development of the immune function (‘exposure’ hypothesis). As feral pigeons Columba livia are genetically polymorphic with respect to melanic coloration, they constitute an ideal model system to address such hypotheses. In this study, we showed that darker melanic individuals had a lower endoparasite intensity (reflecting host susceptibility) and had a greater cellular immune response to PHA injection than paler ones, whereas parasite prevalence (reflecting exposure to vectors) was similar between colorations. These results provide a correlative support of the ‘genetic link’ hypothesis: differently coloured individuals might be similarly exposed to parasites but darker ones might have a better ability to control the infection. This suggests that parasitism could play a crucial role in the maintenance of colour polymorphism in natural populations, which opens the interesting possibility that differently coloured individuals could be adapted to alternative environments varying in parasite diversity and exposure.     

Immune function, parasitization and extended phenotypes in colour polymorphic pygmy grasshoppers

Ecological and evolutionary consequences of host–parasite interactions have attracted considerable attention from evolutionary biologists. Previous studies have suggested that immune responsiveness may be genetically or developmentally linked with colour pattern, such that the evolution of animal colour patterns may be influenced by correlated responses to selection for parasite resistance. We studied interactions between the endoparasitic fly Leiophora innoxia (Meigen) (Diptera: Tachinidae) and its colour polymorphic pygmy grasshopper host Tetrix undulata (Sow.) (Orthoptera: Tetrigidae) to test for morph‐specific differences in parasitization and immune defence, and host‐induced variation in parasite phenotypes. Our results revealed that c. 2 and 30% of adult grasshoppers collected from the same natural population in two subsequent years, respectively were parasitized. Parasite prevalence was independent of host sex and colour morph. Pupae were larger if the parasite had developed in a female than in a male host, possibly reflecting host resource value or a physical constraint on larval growth imposed by host body size. Pupal size was also associated with host colour morph, with individuals that had developed in dark morphs being smaller at pupation compared to those that developed in paler morphs. However, immune defence, measured as the encapsulation response to a novel antigen, did not differ among individuals belonging to alternative colour morphs or sexes. Darker morphs warm up more quickly and prefer higher body temperatures than paler ones. Encapsulation was not influenced by maintenance temperature (15 vs. 30 °C), however, suggesting that indirect effects of coloration on parasite resistance mediated via differential body temperature are unlikely. The dependence of parasite body size on host colour morph may thus reflect plasticity of growth and development of the larvae in response to differential host body temperature, rather than variable host immune defence. © 2005 The Linnean Society of London, Biological Journal of the Linnean Society, 2005, 85 , 373–383.     

The adaptive function of melanin-based plumage coloration to trace metals

Trace metals produced by anthropogenic activities are of major importance in urban areas and might constitute a new evolutionary force selecting for the ability to cope with their deleterious effects. Interestingly, melanin pigments are known to bind metal ions, thereby potentially sequestering them in inert body parts such as coat and feathers, and facilitating body detoxification. Thus, a more melanic plumage or coat coloration could bring a selective advantage for animals living in polluted areas. We tested this hypothesis by investigating the link between melanin-based coloration and zinc and lead concentrations in feathers of urban feral pigeons, both at capture time and after one year of captivity in standardized conditions. Results show that differently coloured pigeons had similar metal concentrations at capture time. Metal concentrations strongly decreased after one year in standardized conditions, and more melanic pigeons had higher concentrations of zinc (but not lead) in their feathers. This suggests that more melanic pigeons have a higher ability to store some metals in their feathers compared with their paler counterparts, which could explain their higher success in urbanized areas. Overall, this work suggests that trace metal pollution may exert new selective forces favouring more melanic phenotypes in polluted environments.     

Space use and genetic structure do not maintain color polymorphism in a species with alternative behavioral strategies

Space use including territoriality and spatial arrangement within a population can reveal important information on the nature, dynamics, and evolutionary maintenance of alternative strategies in color polymorphic species. Despite the prevalence of color polymorphic species as model systems in evolutionary biology, the interaction between space use and genetic structuring of morphs within populations has rarely been examined. Here, we assess the spatial and genetic structure of male throat color morphs within a population of the tawny dragon lizard, Ctenophorus decresii. Male color morphs do not differ in morphology but differ in aggressive and antipredator behaviors as well as androgen levels. Despite these behavioral and endocrine differences, we find that color morphs do not differ in territory size, with their spatial arrangement being essentially random with respect to each other. There were no differences in genetic diversity or relatedness between morphs; however, there was significant, albeit weak, genetic differentiation between morphs, which was unrelated to geographic distance between individuals. Our results indicate potential weak barriers to gene flow between some morphs, potentially due to nonrandom pre‐ or postcopulatory mate choice or postzygotic genetic incompatibilities. However, space use, spatial structure, and nonrandom mating do not appear to be primary mechanisms maintaining color polymorphism in this system, highlighting the complexity and variation in alternative strategies associated with color polymorphism.     

Gudgeon fish with and without genetically determined countershading coexist in heterogeneous littoral environments of an ancient lake

Countershading, characterized by a darker dorsal surface and lighter ventral surface, is common among many animals. This dorsoventral pigment polarity is often thought to be adaptive coloration for camouflage. By contrast, noncountershaded (melanistic) morphs often occur within a species due to genetic color polymorphism in terrestrial animals. However, the polymorphism with either countershaded or melanistic morphs is poorly known in wild aquatic animals. This study explored the genetic nature of diverged color morphs of a lineage of gudgeon fish (genus Sarcocheilichthys) in the ancient Lake Biwa and propose this system as a novel model for testing hypotheses of functional aspects of countershading and its loss in aquatic environments. This system harbors two color morphs that have been treated taxonomically as separate species; Sarcocheilichthys variegatus microoculus which occurs throughout the littoral zone and Sarcocheilichthys biwaensis which occurs in and around rocky areas. First, we confirmed that the divergence of dorsoventral color patterns between the two morphs is under strict genetic control at the levels of chromatophore distribution and melanin‐related gene expression under common garden rearing. The former morph displayed sharp countershading coloration, whereas the latter morph exhibited a strong tendency toward its loss. The crossing results indicated that this divergence was likely controlled by a single locus in a two‐allele Mendelian inheritance pattern. Furthermore, our population genomic and genome‐wide association study analyses detected no genome‐wide divergence between the two morphs, except for one region near a locus that may be associated with the color divergence. Thus, these morphs are either in a state of intraspecific color polymorphism or two incipient species. Evolutionary forces underlying this polymorphism appear to be associated with heterogeneous littoral environments in this lake. Future ecological genomic research will provide insight into adaptive functions of this widespread coloration, including the eco‐evolutionary drivers of its loss, in the aquatic world.     

Thermal environment shapes cuticle melanism and melanin-based immunity in the ground cricket Allonemobius socius

The thermal melanin hypothesis posits that ectothermic individuals of larger size or from colder environments exhibit darker cuticles due to melanin’s efficacy in absorbing solar radiation. However, melanin is also a crucial component of arthropod immunity. Thus, thermal selection for increased cuticle darkness may profoundly influence melanin-based immune function. In this study, we address the relationships between the thermal environment (season length), cuticular melanism and two aspects of melanin-based immunity across nine thermally distinct populations of the cricket Allonemobius socius. We found that season length (i.e. degree days) and body size had a positive association with cuticle melanism in both sexes across populations, supporting the thermal melanism hypothesis. Despite their smaller size, males were found to have darker cuticles and superior melanin-based immunity. This pattern may be the result of additional selection on males due to sex-specific temperature-dependent activities, such as male calling song. Perhaps most interestingly, we found that short season length populations (i.e. colder) exhibited a greater phenoloxidase activity (aspect of the melanin-based immune system) in addition to darker cuticles in both sexes. This pattern is consistent with direct thermal selection on cuticular color, coupled with indirect selection on melanin-based immunity due to pleiotropy. Thus, thermal selection on cuticle darkness appears to indirectly shape the evolution of pathogen resistance in this system, and potentially for other terrestrial arthropod systems whose ranges encompass a significant thermal gradient.     

Does urbanization ameliorate the effect of endoparasite infection in kangaroo rats?

Urban development can fragment and degrade remnant habitat. Such habitat alterations can have profound impacts on wildlife, including effects on population density, parasite infection status, parasite prevalence, and body condition. We investigated the influence of urbanization on populations of Merriam''s kangaroo rat (Dipodomys merriami) and their parasites. We predicted that urban development would lead to reduced abundance, increased parasite prevalence in urban populations, increased probability of parasite infection for individual animals, and decreased body condition of kangaroo rats in urban versus wildland areas. We live trapped kangaroo rats at 5 urban and 5 wildland sites in and around Las Cruces, NM, USA from 2013 to 2015, collected fecal samples from 209 kangaroo rats, and detected endoparasites using fecal flotation and molecular barcoding. Seven parasite species were detected, although only two parasitic worms, Mastophorus dipodomis and Pterygodermatites dipodomis, occurred frequently enough to allow for statistical analysis. We found no effects of urbanization on population density or probability of parasite infection. However, wildland animals infected with P. dipodomis had lower body condition scores than infected animals in urban areas or uninfected animals in either habitat. Our results suggest that urban environments may buffer Merriam''s kangaroo rats from the detrimental impacts to body condition that P. dipodomis infections can cause.     

Eumelanin‐based colouration reflects local survival of juvenile feral pigeons in an urban pigeon house

Urbanisation introduces deep changes in habitats, eventually creating new urban ecosystems where ecological functions are driven by human activities. The higher frequency of some phenotypes in urban vs rural/wild areas has led to the assumption that directional selection in urban habitats occurs, which may thereby favour some behavioural and physiological traits in urban animal populations compared to rural ones. However, empirical evidence of directional selection on phenotypic traits in urban areas remains scarce. In this study we tested whether eumelanin‐based colouration could be linked to survival in two urban populations of the feral pigeon Columba livia. A number of studies in different cities pointed out a higher frequency of darker individuals in more urbanised areas compared to rural ones. To investigate whether directional selection through survival on this highly heritable trait could explain such patterns, we conducted mark–recapture studies on two populations of feral pigeons in highly urbanized areas. We predicted that darker coloured individuals would exhibit higher survival and/or philopatry (integrated into ‘local survival’) than paler coloured ones. No difference in local survival was found between adults of different colouration intensities. However, on one site, we found that darker juveniles had a higher local survival probability than light ones. Juvenile local survival on that site was also negatively correlated with the number of chicks born. This suggests the existence of colour‐ and/or density‐dependent selection processes acting on juvenile feral pigeons in urban environments, acting through differential mortality and/or dispersal.     

Differential Haemoparasite Intensity between Black Sparrowhawk (Accipiter melanoleucus) Morphs Suggests an Adaptive Function for Polymorphism

Recent research suggests that genes coding for melanin based colouration may have pleiotropic properties, in particular conveying raised immune function. Thus adaptive function of polymorphism may be associated with parasite resistance. The black sparrowhawk Accipiter melanoleucus is a polymorphic raptor with two morphs. Over most of its range the light morph is commonest, however within the recently colonised Western Cape of South Africa the dark morph predominates. The species breeds in winter throughout South Africa, however unlike in the rest of the species'' South African range, the Western Cape experiences a winter rainfall regime, where arthropod vectors which transmit haematozoan parasites may be more abundant. We hypothesise that the higher frequency of dark morph birds in this region may be due to their improved parasite resistance, which enables them to cope with higher parasite pressure. If so, we predict that dark morph black sparrowhawks would have lower parasite burdens than light morph birds. Within our population the prevalence of the two most common haematozoan parasites was high, with 72% of adults infected with Haemoproteus nisi and 59% of adults infected with Leucocytozoon toddi. We found no difference in prevalence for either parasite between adult morphs, or between chicks of different parental morphs. However, within adults infected with H. nisi, infection intensity was significantly higher in light morphs than dark morphs. This suggests that dark morphs have lower parasite loads than light morphs due to resistance rather than morph-specific habitat exploitation. Greater resistance to Haemoproteus parasites may therefore be one of the mechanisms through which dark morph black sparrowhawks have a selective advantage in this region and may explain why they are most common in our study area. In other regions, the cost to benefit ratio may be in favour of the light morph, where parasites are less abundant or virulent.     

Maintenance of polymorphic females: do parasites play a role?

The role of parasites in explaining maintenance of polymorphism is an unexplored research avenue. In odonates, female-limited color polymorphism (one female morph mimicking the conspecific male and one or more gynochromatic morphs) is widespread. Here we investigated whether parasitism contributes to color polymorphism maintenance by studying six species of female dimorphic damselflies using large databases of field-collected animals. We predicted that androchrome females (male mimics) would be more intensively parasitized than gynochrome females which is, according to previous studies, counterbalanced by the advantages of the former when evading male harassment compared to gynochrome females. Here we show that in Ischnura denticollis and Enallagma novahispaniae, androchrome females suffer from a higher degree of parasitism than gynochromatic females, and contrary to prediction, than males. Thus, our study has detected a correlation between color polymorphism and parasitic burden in odonates. This leads us to hypothesize that natural selection, via parasite pressure, can explain in part how androchrome and gynochrome female color morphs can be maintained. Both morphs may cope with parasites in a different way: given that androchrome females are more heavily parasitized, they may pay a higher fecundity costs, in comparison to gynochrome females.     

黑带食蚜蝇体色变异的研究

通过对黑带食蚜蝇Episyrphus balteatus(De Geer)体色变异的研究,发现黑带食蚜蝇存在深色型和浅色型2种基本形式,体色变异具有明显的季节性,深色型个体出现在温度较低的秋季及早春,浅色型个体发生在温度较高的春夏季节;在腹部色斑方面,深色型和浅色型个体中均存在变异,可划分为8种类型,腹部色斑的变异在浅色型个体中较为丰富,腹部不同体节背板上色斑的变异程度不同;黑带食蚜蝇在体型大小方面同样存在差异,这些变异的多态性可能是食蚜蝇系统学研究中异名产生的一个重要原因。因此,食蚜蝇类群的个体体色变异在系统学研究中是一个必须特别注意的问题。     

Green‐brown polymorphism in alpine grasshoppers affects body temperature

1. Ectothermic animals depend on external heat sources for pursuing their daily activities. However, reaching sufficiently high temperature can be limiting at high altitudes, where nights are cold and seasons short. We focus on the role of a green‐brown color polymorphism in grasshoppers from alpine habitats. The green‐brown polymorphism is phylogenetically and spatially widespread among Orthopterans and the eco‐evolutionary processes that contribute to its maintenance have not yet been identified.
2. We here test whether green and brown individuals heat up to different temperatures under field conditions. If they do, this would suggest that thermoregulatory capacity might contribute to the maintenance of the green‐brown polymorphism.
3. We recorded thorax temperatures of individuals sampled and measured under field conditions. Overall, thorax temperatures ranged 1.7–42.1°C. Heat up during morning hours was particularly rapid, and temperatures stabilized between 31 and 36°C during the warm parts of the day. Female body temperatures were significantly higher than body temperatures of males by an average of 2.4°C. We also found that brown morphs were warmer by 1.5°C on average, a pattern that was particularly supported in the polymorphic club‐legged grasshopper Gomphocerus sibiricus and the meadow grasshopper Pseudochorthippus parallelus.
4. The difference in body temperature between morphs might lead to fitness differences that can contribute to the maintenance of the color polymorphism in combination with other components, such as crypsis, that functionally trade‐off with the ability to heat up. The data may be of more general relevance to the maintenance of a high prevalence polymorphism in Orthopteran insects.

     

Living in the city: can anyone become an ‘urban exploiter'?

Aim As urban landscapes expand, shifts in biodiversity are occurring. This is leading biogeographers and ecologists to consider human‐dominated landscapes in their current work. One question that arises is: what characterizes those species that are widespread in the most highly urban environments compared with those restricted to less urbanized areas in the city? Here, we aim to identify the traits that enable species to become urban exploiters, i.e. to dominate highly urbanized surroundings. Identifying these traits may help us better predict and possibly mitigate the biotic homogenization occurring in these areas. Location Israel in general, with special focus on the city of Jerusalem. Methods Combining literature and field‐based data for birds in Israel we compared phenotypic, behavioural and life‐history traits between urban exploiters and urban adapters. The latter occur in urban landscapes, but are characteristic of the less urbanized parts of the city. We then examined the trends along a finer field‐sampled gradient of increasing urbanization from sub‐natural to downtown areas within the city of Jerusalem. Results Urban exploiters and adapters differed primarily in social structure and migratory status: exploiters were significantly more social and sedentary than urban adapters. Clear trends were also seen for dietary preferences along a gradient of increasing urbanization in Jerusalem, such that, with increasing urbanization, the proportion of granivorous species increased whereas the proportion of species feeding on invertebrates declined. In contrast, neither relative brain size nor behavioural flexibility, as measured by feeding innovations, differed significantly among urban exploiters and adapters in Israel or along the urbanization gradient in Jerusalem specifically. Main conclusions The results of our study suggest that being successful in more vs. less urbanized environments in the city is not necessarily a factor of brain size nor of how flexible and behaviourally innovative the species is; rather, it depends on a combination of traits, including diet, degree of sociality, sedentariness and preferred nesting sites.     

Some like it hot: Intra-Population Variation in behavioral Thermoregulation in Color-Polymorphic pygmy Grasshoppers

Ectothermic animals rely on external heat sources and behavioral thermoregulation to control body temperature, and are characterized by possessing physiological and behavioural traits which are temperature dependent. It has therefore been suggested that constraints on the range of body temperatures available to individuals imposed by phenotypic properties, such as coloration, may translate into differential fitness and selection against thermally inferior phenotypes. In this paper, I report an association between thermal preferences and thermal capacity (the ability to warm up when insolated) across different genetically coded color morphs of the pygmy grasshopper Tetrix subulata. Data on behavioral thermoregulation of individuals in a laboratory thermal gradient revealed a preference for higher body temperatures in females than in males, and significant variation among colour morphs in preferred body temperatures in females, but not in males. The variation in females was in perfect accordance with estimates of morph-specific differences in thermal capacity. Thus, dark morphs not only attain higher temperatures when exposed to augmented illumination, but also prefer higher body temperatures, compared to paler morphs. This intra-population divergence probably reflects an underlying variation among colour morphs in temperature optima, and is consistent with the notion that coloration, behaviour and physiology evolve in concert.     

Personality traits and behavioral syndromes in differently urbanized populations of house sparrows (Passer domesticus)

Urbanization creates novel environments for wild animals where selection pressures may differ drastically from those in natural habitats. Adaptation to urban life involves changes in various traits, including behavior. Behavioral traits often vary consistently among individuals, and these so-called personality traits can be correlated with each other, forming behavioral syndromes. Despite their adaptive significance and potential to act as constraints, little is known about the role of animal personality and behavioral syndromes in animals' adaptation to urban habitats. In this study we tested whether differently urbanized habitats select for different personalities and behavioral syndromes by altering the population mean, inter-individual variability, and correlations of personality traits. We captured house sparrows (Passer domesticus) from four different populations along the gradient of urbanization and assessed their behavior in standardized test situations. We found individual consistency in neophobia, risk taking, and activity, constituting three personality axes. On the one hand, urbanization did not consistently affect the mean and variance of these traits, although there were significant differences between some of the populations in food neophobia and risk taking (both in means and variances). On the other hand, both urban and rural birds exhibited a behavioral syndrome including object neophobia, risk taking and activity, whereas food neophobia was part of the syndrome only in rural birds. These results indicate that there are population differences in certain aspects of personality in house sparrows, some of which may be related to habitat urbanization. Our findings suggest that urbanization and/or other population-level habitat differences may not only influence the expression of personality traits but also alter their inter-individual variability and the relationships among them, changing the structure of behavioral syndromes.     

Phenotypic plasticity in insects: the effects of substrate color on the coloration of two ground-hopper species

SUMMARY The question of how phenotypic variation is maintained within populations has long been a central issue in evolutionary biology. Most of these studies focused on the maintenance of genetic variability, but the phenotype of organisms may also be influenced by environmental cues experienced during ontogeny. Color polymorphism has received particular attention in evolutionary studies as it has strong fitness consequences. However, if body coloration is influenced by the environment, any conclusions on evolutionary consequences of fitness trade-offs can be misleading. Here we present data from a laboratory experiment on the influence of substrate color on three aspects of the coloration of two ground-hopper species, Tetrix subulata and Tetrix ceperoi . We reared hatchlings either on dark or on light substrates, using a split-brood design. Although the type of pronotal pattern changed mainly in response to nymphal development, the basic color was strongly influenced by the substrate color. In both species, black and dark olive color morphs were found more frequently on the dark substrate, whereas the gray color morph dominated on the light substrate. These findings have considerable implications for our understanding of color morph evolution as they show that color polymorphism may not only be maintained by natural selection acting on discrete color morphs, but also by phenotypic plasticity, which enables organisms to adjust to the environmental conditions experienced during ontogeny. This facultative morphology is opposing to the prevailing view of color morph adaptation, which assumes a purely genetic determination and co-evolution of discrete color morphs with life history traits.     

Water temperature,not fish morph,determines parasite infections of sympatric Icelandic threespine sticklebacks (Gasterosteus aculeatus)

Parasite communities of fishes are known to respond directly to the abiotic environment of the host, for example, to water quality and water temperature. Biotic factors are also important as they affect the exposure profile through heterogeneities in parasite distribution in the environment. Parasites in a particular environment may pose a strong selection on fish. For example, ecological differences in selection by parasites have been hypothesized to facilitate evolutionary differentiation of freshwater fish morphs specializing on different food types. However, as parasites may also respond directly to abiotic environment the parasite risk does not depend only on biotic features of the host environment. It is possible that different morphs experience specific selection gradients by parasites but it is not clear how consistent the selection is when abiotic factors change. We examined parasite pressure in sympatric morphs of threespine stickleback (Gasterosteus aculeatus) across a temperature gradient in two large Icelandic lakes, Myvatn and Thingvallavatn. Habitat‐specific temperature gradients in these lakes are opposite. Myvatn lava rock morph lives in a warm environment, while the mud morph lives in the cold. In Thingvallavatn, the lava rock morph lives in a cold environment and the mud morph in a warm habitat. We found more parasites in fish living in higher temperature in both lakes, independent of the fish morph, and this pattern was similar for the two dominating parasite taxa, trematodes and cestodes. However, at the same time, we also found higher parasite abundance in a third morph living in deep cold–water habitat in Thingvallavatn compared to the cold‐water lava morph, indicating strong effect of habitat‐specific biotic factors. Our results suggest complex interactions between water temperature and biotic factors in determining the parasite community structure, a pattern that may have implications for differentiation of stickleback morphs.     

Immune and Stress Responses Covary with Melanin-Based Coloration in the Barn Swallow

Eumelanin and pheomelanin are the main endogenous pigments in animals and melanin-based coloration has multiple functions. Melanization is associated with major life-history traits, including immune and stress response, possibly because of pleiotropic effects of genes that control melanogenesis. The net effects on pheo- versus eumelanization and other life-history traits may depend on the antagonistic effects of the genes that trigger the biosynthesis of either melanin form. Covariation between melanin-based pigmentation and fitness traits enforced by pleiotropic genes has major evolutionary implications particularly for socio-sexual communication. However, evidence from non-model organisms in the wild is limited to very few species. Here, we tested the hypothesis that melanin-based coloration of barn swallow (Hirundo rustica) throat and belly feathers covaries with acquired immunity and activation of the hypothalamic–pituitary–adrenal (HPA) axis, as gauged by corticosterone plasma levels. Individuals of both sexes with darker brownish belly feathers had weaker humoral immune response, while darker males had higher circulating corticosterone levels only when parental workload was experimentally reduced. Because color of belly feathers depends on both eu- and pheomelanin, and its darkness decreases with an increase in the concentration of eu- relative to pheomelanin, these results are consistent with our expectation that relatively more eu- than pheomelanized individuals have better immune response and smaller activation of the HPA-axis. Covariation of immune and stress response arose for belly but not throat feather color, suggesting that any function of color as a signal of individual quality or of alternative life-history strategies depends on plumage region.     

Fixed green and brown color morphs and a novel color-changing morph of the Pacific tree frog Hyla regilla

Pacific tree frogs Hyla regilla are typically either green or brown in dorsal coloration. The frequency of green and brown individuals is known to fluctuate seasonally. Previous investigators have generally assumed that the green and brown body colors represent a "fixed" polymorphism and that seasonal changes in the proportion of the two body colors are a consequence of differential survival of the two color morphs. Here we report that, in addition to the "fixed" (i.e., non-color-changing) green and brown morphs of H. regilla, there are some individuals that can change hue between green and brown. The distribution of color-change ability in our study population is bimodal, suggesting that "color changers" are a distinct morph rather than one extreme of a continuous distribution of color-change ability. Our findings suggest that background brightness, not hue, triggers color change in the newly discovered morph and that this change requires days to weeks to occur. Such slow color change is not well suited for making short-term changes in color as a frog moves between differently colored substrates. Rather, seasonal changes in habitat characteristics and/or microhabitat use are likely to maintain color-change ability. Color polymorphism and color-change ability appear to represent alternative responses to divergent selection for crypsis in a heterogeneous, seasonally variable environment.     

Using Parasitic Load to Measure the Effect of Anthropogenic Disturbance on Vervet Monkeys

Vervet monkeys, Chlorocebus pygerythrus, thrive in urban areas of KwaZulu-Natal, South Africa, and present a suitable model to assess parasitic load as a measure of anthropogenic disturbance, such as urbanization. We collected vervet monkey faecal samples from four study sites representing a gradient of land use and urbanization. We assessed faecal parasites using the faecal flotation method calculating eggs per gram and parasite richness. Overall, the more urban vervet monkey populations had a significantly higher parasite richness and abundance. Our study shows the applicability of using parasite load to measure the effect of urbanization on wildlife.