Molecular detection of invertebrate prey in vertebrate diets: trophic ecology of Caribbean island lizards

Understanding community assembly and population dynamics frequently requires detailed knowledge of food web structure. For many consumers, obtaining precise information about diet composition has traditionally required sacrificing animals or other highly invasive procedures, generating tension between maintaining intact study populations and knowing what they eat. We developed 16S mitochondrial DNA sequencing methods to identify arthropods in the diets of generalist vertebrate predators without requiring a blocking primer. We demonstrate the utility of these methods for a common Caribbean lizard that has been intensively studied in the context of small island food webs: Anolis sagrei (a semi‐arboreal ‘trunk‐ground’ anole ecomorph). Novel PCR primers were identified in silico and tested in vitro. Illumina sequencing successfully characterized the arthropod component of 168 faecal DNA samples collected during three field trips spanning 12 months, revealing 217 molecular operational taxonomic units (mOTUs) from at least nine arthropod orders (including Araneae, Blattodea, Coleoptera, Hemiptera, Hymenoptera, Isoptera, Lepidoptera and Orthoptera). Three mOTUs (one beetle, one cockroach and one ant) were particularly frequent, occurring in ≥50% of samples, but the majority of mOTUs were infrequent (180, or 83%, occurred in ≤5% of samples). Species accumulation curves showed that dietary richness and composition were similar between size‐dimorphic sexes; however, female lizards had greater per‐sample dietary richness than males. Overall diet composition (but not richness) was significantly different across seasons, and we found more pronounced interindividual variation in December than in May. These methods will be generally useful in characterizing the diets of diverse insectivorous vertebrates.     

The Effect of Host Constitution on the Development of Plasmodium floridense*

More than 15,000 lizards from South Georgia were examined over a period of 16 years. Five percent of Sceloporus undulatus and 36% of Anolis carolinensis were found to harbor Plasmodium floridense. Development of 28 natural new infections was followed in detail as soon as they became patent and comparisons in the 2 host species made of intensity and duration of infections and of merozoite means during the periods of acute rise and decline. During the acute rise, the merozoite mean in Sceloporus was 10.6 ± 0.11 (8,495 segmenters counted), compared with 13.44 ± 0.15 in Anolis (3,805 counted); during the decline, the merozoite means were 8.55 ± 0.13 (3,305 counted) and 10.28 ± 0.09 (6,772 counted), respectively. It took an average of 150 (100–253) days for the infection to run its course in Sceloporus, compared with the average of 71 (60–90) days in Anolis; the peak of parasitemia in Sceloporus was 11,600 parasites/10,000 red cells, compared with 1,600 in Anolis. Both lizard genera produced 5–10% gametocytes.     

The value of comparative approaches to our understanding of puberty as illustrated by investigations in birds and reptiles

This article is part of a Special Issue "Puberty and Adolescence". Studies of birds and reptiles have provided many basic insights into the neuroendocrine control of reproductive processes. This research has elucidated mechanisms regulating both early development, including sexual differentiation, and adult neuroendocrine function and behavior. However, phenomena associated with the transition into sexual maturation (puberty) have not been a focus of investigators working on species in these taxonomic classes. Research is complicated in birds and reptiles by a variety of factors, including what can be extended times to maturation, the need to reach particular body size regardless of age, and environmental conditions that can support or inhibit endocrine responses. However, careful selection of model systems, particularly those with available genetic tools, will lead to important comparative studies that can elucidate both generalizability and diversity of mechanisms regulating the onset of reproductive maturity.     

A comparative analysis of clinging ability among pad-bearing lizards

We examined clinging ability, subdigital pad area and body mass in 14 pad-bearing lizard species from three families to test three predictions: (1) clinging ability and pad area should be tightly correlated among species; (2) pad area and clinging ability should scale similarly to body mass among 14 species; and (3) functional similarity in clinging capabilities should exist among species despite differences in body mass. Our results confirm two predictions; clinging ability is tightly correlated with pad area, even when the effects of body size are removed, and the lizards examined are approximately functionally similar in their clinging capabilities. Nevertheless, despite the tight correlation between pad area and clinging ability, pad area scales with body mass by a lower slope than clinging ability. Overall, these results indicate that although pad area is a strong determinant of clinging ability, other factors enable these lizards to maintain functional similarity.     

The effect of prey availability on offspring survival depends on maternal food resources

Maternal nutrition can strongly influence embryo development and offspring fitness. The environmental matching hypothesis posits that developmental conditions affect offspring in ways that enable them to appropriately deal with similar post‐developmental conditions, although mismatches between developmental and post‐developmental environments will reduce fitness. To test this hypothesis, reproductive lizards (Anolis sagrei) were reared in environments with high versus low prey availability. The resultant offspring were then reared reciprocally under the same two prey conditions that their mothers experienced. High levels of prey available to mothers increased egg production, although the survival of eggs was low compared to those produced by mothers in the low‐prey treatment. Low prey availability to offspring reduced growth, regardless of the amount of prey available to their mothers. Low prey availability also compromised offspring survival, although this negative effect was only present when mothers experienced high‐prey conditions, whereas matching of low‐prey conditions in maternal and offspring stages resulted in high survival. However, because the mismatch of low maternal and high offspring prey availability resulted in similar offspring survival to the matched treatments, our results do not fully support the environmental matching hypothesis. Nevertheless, the present study highlights the interactive role of maternal and post‐hatching environments in generating variation in offspring fitness. © 2015 The Linnean Society of London, Biological Journal of the Linnean Society, 2015, 115 , 437–447.     

Control of the pars intermedia of the lizard,Anolis carolinensis

Summary The ultrastructure of the intermediate lobe of the hypophysis was studied in Anolis carolinensis with the use of a threefold aldehyde fixative. Lizards with a brown skin were selected. The possibility of two types of secretory cells is discussed; neither cell type is innervated. Type I cells are rarely found and contain dense granules approximately 0.3 m in diameter; Type II cells vary widely in secretory activity. Most of the Type II cells contain a large number of dense secretory granules (up to about 1.3 m in diameter) almost filling the cytoplasm. Rough endoplasmic reticulum (RER), Golgi apparatus and mitochondria are poorly developed. Only some of these cells show signs suggesting a high secretory activity, namely a well developed RER, Golgi apparatus and numerous mitochondria. In these cells the RER sometimes forms large intracisternal droplets (up to 7 m in diameter). Two of the animals exhibited a more uniform, high secretory activity. Large (about 2 m in diameter), pale vacuoles, probably of extracellular character, were found mostly in the vicinity of the perivascular septum. Their role in the release of MSH is discussed. The present data, which are discussed with reference to earlier findings (Forbes, 1972), form the morphological basis for an experimental study on regulation of MSH release (Larsson et al., 1979).Supported by grants from the Swedish Natural Science Research Council (to P. Meurling) and the Royal Physiographic Society of LundThe authors are indebted to Mrs. Ingrid Hallberg, Mrs. Kirsten Thörneby and Mrs. Lena Sandell for valuable technical assistance and to Miss Inger Norling for photographic aid     

Size but not relatedness drives the spatial distribution of males within an urban population of Anolis carolinensis lizards

The way that individuals are spatially organized in their environment is a fundamental population characteristic affecting social structure, mating system, and reproductive ecology. However, for many small or cryptic species, the factors driving the spatial distribution of individuals within a population are poorly understood and difficult to quantify. We combined microsatellite data, remote sensing, and mark–recapture techniques to test the relative importance of body size and relatedness in determining the spatial distribution of male Anolis carolinensis individuals within a focal population over a five‐year period. We found that males maintain smaller home ranges than females. We found no relationship between male body size and home range size, nor any substantial impact of relatedness on the geographic proximity. Instead, the main driver of male spatial distribution in this population was differences in body size. We also found no evidence for offspring inheritance of their parent''s territories. Males were never sampled within their father''s territory providing strong support for male‐biased dispersal. This study introduces a novel approach by combining standard mark release capture data with measures of pairwise relatedness, body size, and GPS locations to better understand the factors that drive the spatial distribution of individuals within a population.     

Clothing color mediates lizard responses to humans in a tropical forest

Identifying how ecotourism affects wildlife can lower its environmental impact. Human presence is an inherent component of ecotourism, which can impact animal behavior because animals often perceive humans as predators and, consequently, spend more time on human-directed antipredator behaviors and less on other fitness-relevant activities. We tested whether human clothing color affects water anole (Anolis aquaticus) behavior at a popular ecotourism destination in Costa Rica, testing the hypothesis that animals are more tolerant of humans wearing their sexually selected signaling color. We examined whether clothing resembling the primary signaling color (orange) of water anoles increases number of anole sightings and ease of capture. Research teams mimicked an ecotourism group by searching for anoles wearing one of three shirt treatments: orange, green, or blue. We conducted surveys at three different sites: a primary forest, secondary forest, and abandoned pasture. Wearing orange clothing resulted in more sightings and greater capture rates compared with blue or green. A higher proportion of males were captured when wearing orange whereas sex ratios of captured anoles were more equally proportional in the surveys when observers wore green or blue. We also found that capture success was greater when more people were present during a capture attempt. We demonstrate that colors “displayed” by perceived predators (i.e., humans) alter antipredator behaviors in water anoles. Clothing choice could have unintended impacts on wildlife, and wearing colors resembling the sexually selected signaling color might enhance tolerance toward humans.