Sources And Consequences of Ecological Intraspecific Variation In The Florida Scrub Lizard (Sceloporus Woodi)

Sceloporus woodi is a small, sexually dimorphic Iguanid lizard endemic to dry xeric habitats in Florida. This species is most often found in sand-pine scrub habitats, but also inhabits relic long-leaf pine islands within the scrub of the Ocala National Forest in north central Florida. In the current study I investigated seasonal and sexual variation in foraging behavior of S. woodi and compared microhabitat use, behavior, diet, morphology, and ectoparasite load at a pine island site to S. woodi in scrub habitats. No variation in movement patterns existed between seasons and sexes. However significant seasonal and sexual differences did exist in the way S. woodi attacked prey. Using the proportion of attacks on prey made while stationary and lag sequential analysis, I found that females are more willing to move greater than one body length to attack prey items than males and both sexes are more apt to move to attack prey during the post-breeding season. These behavioral differences translated into a more diverse and higher volume diet in females during the breeding season. Even though both sexes showed the same seasonal patterns in foraging behavior, their diets changed in the opposite manner. Female diets decreased in volume and the number of prey types in the post-breeding season while male diets increased in both characteristics. Lizards at the pine island site used trees most often while lizards in the scrub used terrestrial habitats most often. Behavior was similar between habitats, but individuals did move their heads more often at the pine island site. At the pine island site lizards had significantly lower body temperatures, consumed less diverse prey, and had lower ectoparasite loads. Lizards in the long leaf pine had longer limbs than their counterparts in scrub habitats. However, only females differed in body shape between habitat types. This study has identified sources and consequences of variation in the foraging behavior of S. woodi. Additionally this study has shown that S. woodi in pine island habitats may differ ecologically from S. woodi in scrub habitats

Selective Utilization of Microhabitats by Web-building Spiders

Natural enemies are members of complex ecological communities, and their ability to contribute to the biological control of pest organisms is strongly influenced by a convoluted network of ecological interactions with many other organisms within these communities. Researchers must develop an understanding of the mechanisms that shape trophic webs to predict and promote top-down effects of predators. The behavior of predators can have a strong influence on their potential as biological control agents. Web-building spiders are a useful example organism for the study of natural enemy behavior because of the experimentally tractable nature of their foraging behavior. Specifically, patterns in microhabitat utilization and web construction by spiders provide insights into foraging behavior and pest-suppression potential. In field collections, spiders were found to utilize microhabitats in a species-specific manner. Molecular gut-content analysis and a mathematical model showed that two spiders belonging to different web-building guilds differed in their dependence on microhabitat-specific prey activity-densities. In particular, the sheet-weaving guild constructed webs in microhabitats with the highest densities of springtails (Collembola). High dependence on this non-pest prey also correlated with evidence of increased intraspecific competition, and implies a potential negative effect of springtails on the consumption of pest insects, such as aphids. In laboratory two-choice assays, sheet-weaving spiders selected microhabitats and constructed webs in a flexible, stepwise manner, which allowed spiders to regulate their investment of silk resources to match the profitability of the microhabitat. Spiders also exhibited prey-specific shifts in foraging behavior, constructing webs in the presence of mobile, non-pest springtails, but utilizing active foraging tactics in the presence of sedentary, pest aphids. However, in factorial no-choice assays, pest-consumption rates were not significantly affected by the presence of non-pest springtails, indicating that prey-specific foraging-mode shifts are compatible with biological control. From these results, it is clear that the flexible foraging behavior of web-building spiders has a strong influence on their roles in ecological communities and their position within food webs. This dissertation highlights the importance of understanding the nuances of natural-enemy behavior for properly assessing and promoting biological control services

Structural analyses in the study of behavior: From rodents to non-human primates

The term "structure" indicates a set of components that, in relation to each other, shape an organic complex. Such a complex takes on essential connotations of functionally unitary entity resulting from the mutual relationships of its constituent elements. In a broader sense, we can use the word "structure" to define the set of relationships among the elements of an emergent system that is not determined by the mere algebraic sum of these elements, but by the interdependence relationships of these components from which the function of the entire structure itself derives. The behavior of an integrated living being can be described in structural terms via an ethogram, defined as an itemized list of behavioral units. Akin to an architectural structure, a behavioral structure arises from the reciprocal relationships that the individual units of behavior establish. Like an architectural structure, the function of the resulting behaving complex emerges from the relationships of the parts. Hence, studying behavior in its wholeness necessitates not only the identification of its constitutive units in their autarchic individuality, but also, and importantly, some understanding of their relationships. This paper aimed to critically review different methods to study behavior in structural terms. First, we emphasized the utilization of T-pattern analysis, i.e., one of the most effective and reliable tools to provide structural information on behavior. Second, we discussed the application of other methodological approaches that are based on the analysis of transition matrices, such as hierarchical clustering, stochastic analyses, and adjusted residuals. Unlike T-pattern analysis, these methods allow researchers to explore behavioral structure beyond its temporal characteristics and through other relational constraints. After an overview of how these methods are used in the study of animal behavior, from rodents to non-human primates, we discussed the specificities, advantages and challenges of each approach. This paper could represent a useful background for all scientists who intend to study behavior both quantitatively and structurally, that is in terms of the reciprocal relationships that the various units of a given behavioral repertoire normally weave together

Structural analyses in the study of behavior : From rodents to non-human primates

Ajuts: J-BL's research was funded by Natural Sciences and Engineering Research Council of Canada (NSERC, Discovery Grant #: 2015-06034 to J-BL). MC, SA, and GC's research was funded by a grant from the University of Palermo, Italy.The term " structure " indicates a set of components that, in relation to each other, shape an organic complex. Such a complex takes on essential connotations of functionally unitary entity resulting from the mutual relationships of its constituent elements. In a broader sense, we can use the word " structure " to define the set of relationships among the elements of an emergent system that is not determined by the mere algebraic sum of these elements, but by the interdependence relationships of these components from which the function of the entire structure itself derives. The behavior of an integrated living being can be described in structural terms via an ethogram, defined as an itemized list of behavioral units. Akin to an architectural structure, a behavioral structure arises from the reciprocal relationships that the individual units of behavior establish. Like an architectural structure, the function of the resulting behaving complex emerges from the relationships of the parts. Hence, studying behavior in its wholeness necessitates not only the identification of its constitutive units in their autarchic individuality, but also, and importantly, some understanding of their relationships. This paper aimed to critically review different methods to study behavior in structural terms. First, we emphasized the utilization of T-pattern analysis, i.e., one of the most effective and reliable tools to provide structural information on behavior. Second, we discussed the application of other methodological approaches that are based on the analysis of transition matrices, such as hierarchical clustering, stochastic analyses, and adjusted residuals. Unlike T-pattern analysis, these methods allow researchers to explore behavioral structure beyond its temporal characteristics and through other relational constraints. After an overview of how these methods are used in the study of animal behavior, from rodents to non-human primates, we discussed the specificities, advantages and challenges of each approach. This paper could represent a useful background for all scientists who intend to study behavior both quantitatively and structurally, that is in terms of the reciprocal relationships that the various units of a given behavioral repertoire normally weave together

How Bright and How Nasty: The Economics of Variable Aposematic Traits

Although the theory about the evolution and maintenance of aposematism predicts distinct and uniform warning signals, variation in both signal and defence is common across many taxa, and some species also show correlations between signal and defence. One hypothesis to explain these correlations is honest signalling of defence in prey through the framework of resource competition enforcing a tradeoff. Competition for antioxidant molecules that have dual functions as pigments and in protecting against oxidative stress from toxin sequestration or production have been suggested as a specific candidate resource limitation that could explain warning signal honesty. In Chapter 2 I report an experiment using the large milkweed bug (Oncopeltus fasciatus) as an aposematic model prey that naturally varies in colour and toxicity. By raising milkweed bugs on diets of controlled toxicity and measuring their defence, signal expression, and oxidative stress, I test the expectations of the resource competition model. I found that milkweed bugs overall did not show a correlation between signal in terms of colouration and their level of chemical defence, but that there was a relationship between signal and glutathione amount, a measure of total antioxidant capacity, in the most toxic bugs. These results suggest a mechanistic link between oxidative stress, warning signals and chemical defences in large milkweed bugs. In Chapter 2 I briefly review the concept of dietary wariness, and in Chapter 4 I apply this in practice, using praying mantids (Hierodula membranacea) as a generalist invertebrate predator. I present them with O. fasciatus raised on one of three diets that differ in chemical defence, one species of nontoxic seeds (Helianthus annus) and two different species of their toxic host plants (genus Asclepias). I tested mantids with nontoxic milkweed bugs and measured their level of neophobia and dietary wariness, then tested them with the Asclepias-raised bugs to measure their avoidance learning. Mantids did not learn to avoid the milkweed bugs, even when possibly facing chronic poisoning from consuming them. My results suggest that avoidance learning of toxic prey in predators is not universal. These experiments further our understanding of variation in aposematic traits in prey by examining two key but less explored hypotheses for why signals might vary: resource competition and dietary wariness

Water and energy balance in the Namib sand-dune lizard, Angolosaurus skoogi

Includes bibliographical references.The field metabolic rate (FMR) and water flux of the herbivorous Namib sand-dune lizard, Angolosaurus skoogi, was measured during the summer non-breeding period (early January) by means of doubly labelled water. FMR was about half that expected for a lizard of this size. Water flux and laboratory measured standard metabolic rates were, however, typical of other desert lizards. It thus appeared a priori that this species was behaviourally reducing metabolic costs through reduced activity. This generated questions with regard to the ecological and physiological significance of low FMRs. Is the reduction forced by intolerable environmental conditions or the need to stay in positive water and energy balance? Alternatively, is activity reduction voluntary and geared towards optimizing growth and storage, possibly in preparation for periods of physiological stress ? The research required to answer these questions forms the basis of this thesis. There has been much discussion about the evolutionary and ecological significance of growth rates. The consensus seems to be that, under most circumstances, animals are adapted in ways that maximize growth or optimize growth in relation to realistically attainable rates of gross energy intake. Animal behaviour may be influenced by factors unrelated to growth considerations such as starvation, involuntary hypo/hyperthermia, predator evasion and social interactions. These factors may be difficult to identify and isolate, making this hypothesis difficult to test. Previous studies on the biology of A. skoogi have shown that this species has a perennially available food source, a wide range of potential body temperatures at its disposal and a low predation risk. Social interaction appear to be confined to the breeding season. This species is thus a particularly suitable subject for a scope for growth optimization study