abstract: The elaborate signals of animals are often costly to produce and maintain, thus communicating reliable information about the quality of an individual to potential mates or competitors. The properties of the sensory systems that receive signals can drive the evolution of these signals and shape their form and function. However, relatively little is known about the ecological and physiological constraints that may influence the development and maintenance of sensory systems. In the house finch (Carpodacus mexicanus) and many other bird species, carotenoid pigments are used to create colorful sexually selected displays, and their expression is limited by health and dietary access to carotenoids. Carotenoids also accumulate in the avian retina, protecting it from photodamage and tuning color vision. Analogous to plumage carotenoid accumulation, I hypothesized that avian vision is subject to environmental and physiological constraints imposed by the acquisition and allocation of carotenoids. To test this hypothesis, I carried out a series of field and captive studies of the house finch to assess natural variation in and correlates of retinal carotenoid accumulation and to experimentally investigate the effects of dietary carotenoid availability, immune activation, and light exposure on retinal carotenoid accumulation. Moreover, through dietary manipulations of retinal carotenoid accumulation, I tested the impacts of carotenoid accumulation on visually mediated foraging and mate choice behaviors. My results indicate that avian retinal carotenoid accumulation is variable and significantly influenced by dietary carotenoid availability and immune system activity. Behavioral studies suggest that retinal carotenoid accumulation influences visual foraging performance and mediates a trade-off between color discrimination and photoreceptor sensitivity under dim-light conditions. Retinal accumulation did not influence female choice for male carotenoid-based coloration, indicating that a direct link between retinal accumulation and sexual selection for coloration is unlikely. However, retinal carotenoid accumulation in males was positively correlated with their plumage coloration. Thus, carotenoid-mediated visual health and performance or may be part of the information encoded in sexually selected coloration. / Dissertation/Thesis / Ph.D. Biology 2011

abstract: Colorful ornaments in animals often serve as sexually selected signals of quality. While pigment-based colors are well-studied in these regards, structural colors that result from the interaction of light with photonic nanostructures are comparatively understudied in terms of their consequences in social contexts, their costs of production, and even the best way to measure them. Iridescent colors are some of the most brilliant and conspicuous colors in nature, and I studied the measurement, condition-dependence, and signaling role of iridescence in Anna's hummingbirds (Calypte anna). While most animal colors are easily quantified using well-established spectrophotometric techniques, the unique characteristics of iridescent colors present challenges to measurement and opportunities to quantify novel color metrics. I designed and tested an apparatus for careful control and measurement of viewing geometry and highly repeatable measurements. These measurements could be used to accurately characterize individual variation in iridescent Anna's hummingbirds to examine their condition-dependence and signaling role. Next, I examined the literature published to date for evidence of condition-dependence of structural colors in birds. Using meta-analyses, I found that structural colors of all three types - white, ultra-violet/blue, and iridescence - are significantly condition-dependent, meaning that they can convey information about quality to conspecifics. I then investigated whether iridescent colors were condition-dependent in Anna's hummingbirds both in a field correlational study and in an experimental study. Throughout the year, I found that iridescent feathers in both male and female Anna's hummingbirds become less brilliant as they age. Color was not correlated with body condition in any age/sex group. However, iridescent coloration in male Anna's hummingbirds was significantly affected by experimental protein in the diet during feather growth, indicating that iridescent color may signal diet quality. Finally, I examined how iridescent colors were used to mediate social competitions in male and female Anna's hummingbirds. Surprisingly, males that were less colorful won significantly more contests than more colorful males, and colorful males received more aggression. Less colorful males may be attempting to drive away colorful neighbors that may be preferred mates. Female iridescent ornament size and color was highly variable, but did not influence contest outcomes or aggression. / Dissertation/Thesis / Ph.D. Biology 2012

Abstract Females may either mate with one (monandry) or several (polyandry) males during a single breeding season. The polyandrous mating system has prompted numerous studies since the recognition of a widespread occurrence of mixed paternity among animals. Consequently, the benefits of polyandry have become well-established, and the female role in sexual selection upgraded. Females may gain both material and genetic benefits from multiple mating. Hence, the occurrence of polyandry is understandable, whereas monandry remains an evolutionary puzzle especially among species with male nutrient provisioning. I studied both the life history variation among female mating tactics and the adaptive significance of monandry in varying environmental conditions in the green-veined white butterfly [Pieris napi, (L. 1758)], which is a predominantly polyandrous species with nuptial feeding. I used a combination of explicit laboratory experiments and field studies. My results show that monandry and degrees of polyandry are distinct strategies with life history differences reaching beyond mating frequencies. Polyandry corresponded with a higher lifetime fecundity than monandry in P. napi. Polyandry was, however, associated with relatively low fecundity during the early days of reproduction. Thus, monandry is beneficial if time for reproduction is limited severely enough or other female traits or behaviours associated with polyandry are traded off against longevity. Due to temporal variation in reproductive rate among mating tactics, offspring of polyandrous females have less time to complete development. Accordingly, polyandrous females developed at a faster rate as larvae than monandrous ones under optimal conditions. Despite growth rate variation, monandrous females were more likely to contribute to additional summer generation in conditions that allow production of only a partial second generation, and thus monandry is favoured under these conditions. Genetic variation in female mating tactics will not only prevail if environmental conditions do not allow all individuals to contribute evenly to the directly breeding generation in bivoltine populations, but also if even the production of a single generation per year is time-limited. A general conclusion would be that seasonality and unpredictability of fitness in the wild drives the evolution of optimal female mating tactics and promotes the maintenance genetic variation in mating frequencies, regardless of the direct benefits of nuptial feeding. Even if a high degree of polyandry would be the most profitable mating tactic in an average year, strong annual variation in weather conditions and the duration of summer may create possibilities for a temporally fluctuating selection that promotes a co-existence of different mating tactics because variance of fitness is likely increase with an increasing mating frequency.

One of the most striking things about many animals is that they can be defined by the ways in which they move. Moving costs metabolic energy and is a significant contributor to the daily energy balance of organisms and therefore fitness. Balancing energy needs is critically important to species inhabiting areas of limited resources. The metabolic cost of locomotion is influenced by physiological, morphological and behavioural factors that vary across species. The influence of these factors within species is less well understood. The objective of my PhD is to elucidate the potential for variation in locomotor performance, in particular the energy consumed and the biomechanics of locomotion within a species, in response to differences in season, sex, age and the nature of the terrain. The Svalbard ptarmigan (Lagopus muta hyperborea) is the only year-round avian resident of the Arctic archipelago of Svalbard. Svalbard is characterized by extreme photoperiodic and climatic conditions, with 24 hours of daylight in summer and continuous darkness in winter, when ice makes food unpredictable. As a result, ptarmigan annually gain significant fat stores, as much as doubling their body mass in winter. The consequences of such large gains in mass upon the metabolic cost and biomechanics of terrestrial locomotion are yet to be quantified. The Svalbard ptarmigan represents a unique opportunity to gain insight into avian adaptations.Using respirometry, I present evidence that winter birds are able to carry their fat stores at no metabolic cost. Using kinematic and force plate data, I show that acquiring fat results in reduced locomotor performance in terms of speed and take-off ability. As well as exhibiting phenotypic variation, male and female Svalbard ptarmigan are behaviourally very different. I present evidence that these behavioural differences are reflected in the metabolic cost of locomotion. In particular, males are both more efficient and faster than female birds during both summer and winter. I suggest that this results from sexual selection upon male locomotor performance. Furthermore, I present data demonstrating that sub-adult males experiencing their first winter possess the same metabolic and speed capabilities of adults. These data may indicate that selection for improved male locomotor performance may act upon sub-adult birds. Regardless of season, age or sex, Svalbard ptarmigan must locomote on a predominantly sloping terrain. The influence of inclines upon the metabolic cost of locomotion in birds is poorly understood. I provide evidence that at the same degree of incline, the cost of lifting 1 kg by 1 vertical metre is similar regardless of season and is therefore dictated by increased positive work. However, this cost varies according to the degree of incline and may be influenced by gait.The principal findings of the 5 first author papers presented are that behavioural, physiological and morphological variation within a species can have significant impacts upon the metabolic cost of locomotion and other aspects of locomotor performance. The potential for intraspecific differences should therefore be taken into account in future research regarding the patterns of energy expenditure in animals.

It is now widely accepted that adaptation to different ecological niches can result in the evolution of new species. However, when gene flow persists speciation must overcome the antagonism between selection and recombination: Specifically, if gene flow persists, recombination will break down the genetic associations between alleles that characterise emerging species and cause reproductive isolation. Accordingly, genetic architectures that impede recombination can slow the breakdown of linkage disequilibrium and facilitate speciation. Mimicry in tropical butterflies has long been championed as an example of adaptation driving speciation. In the Neotropical genus Heliconius, distantly related pairs of unpalatable species often converge on the same bright warning-pattern to more efficiently advertise their distastefulness to predators. In contrast, closely related taxa often belong to different mimicry rings. The sister species, Heliconius melpomene and H. cydno are sympatric across much of Central and northern South America. Using artificial butterflies I reveal selection against non-mimetic hybrid colour patterns between these two species. These colour patterns are also used as mating cues and mimetic shifts may cause both pre-mating and post-mating isolation. However, shifts in colour pattern cannot drive reproductive isolation alone; rather, they must be accompanied by corresponding mate preferences. Associations between trait and preference loci may be broken down by mating and subsequent recombination. I demonstrate a genetic linkage between loci for both male and female mate preference and wing colour pattern in Heliconius cydno and H. melpomene. In addition, I present evidence for further associations between alleles affecting hybrid sterility and host-plant use and colour pattern loci. All this implies that linkage between traits that contribute to reproductive and ecological isolation is a general phenomenon in Heliconius with an underlying adaptive basis. Overall these results expose a genetic mechanism that, by impeding recombination, can facilitate speciation in the face of gene flow.

Sexual selection is a frame of reference that attempts to explain exaggerated signaling traits, including acoustic signals between male and female animals. Contemporary studies in the field of sexual selection are focused on the evolution of female mating preferences, with particular emphasis being placed on the good genes models of sexual selection. Here I investigate whether sexual selection is in operation in the acoustic communication system of the field cricket, Gryllus bimaculatus. Through development of new methodology I show that female crickets have a distinct and repeatable preference and selectivity for certain male song traits. For sexual selection to operate in acoustic communication systems, males must advertise some aspect of their phenotype that will influence female choice. I demonstrate that the basis for arguments invoking sexual selection for spectral song traits in a sister species, G. campestris, which is that tegmen harp area predicts song frequency, is an invalid assumption for sound production in G. bimaculatus. As a result of this finding I investigated what aspects of male song were condition- and morphology-dependent. Temporal and spectral male song traits did not convey information regarding body condition, body size or the ability to withstand developmental instability (as indicated by fluctuating asymmetry). I was unable to detect handicap sexual selection for spectral characteristics of male song despite repeatable female preference for male song frequency. Furthermore, female preference for spectral bandwidth of male song, thought to be a sexually selected trait, was shown to be governed by preference for frequency and therefore not a distinct preference. The lack of detectable sexual selection, together with observed patterns of phenotypic variation in signals and the equivalent response system, suggest that some of the male song traits function for mate recognition. However, sexual selection for call traits not considered here (e.g. duration of calling) is probable. / Dissertation (MSc (Zoology))--University of Pretoria, 2006. / Zoology and Entomology / unrestricted

Patterns of sperm usage in multiply-mated females have profound fitness consequences for males, and create strong selective pressure on male behavior. In the cooperative theridiid spider Anelosimus studiosus Hentz 1850 adult males are tolerated in females' webs, and females have been observed to mate multiply with different males. In this experiment, virgin females were mated with two different males on consecutive days under controlled conditions to determine paternity patterns and behavioral responses of males to non-virgin females. The paternity of broods was analyzed using randomly amplified polymorphic DNA (RAPDs). Fifteen broods were analyzed and complete first male sperm precedence was found. Mating behavior differed between first and second males with the first males attempting fewer intromissions, but having a longer total time of intromission. This suggests that the second males are either prevented from normal copulation, or are reacting to the different condition of the females. The sperm precedence pattern is discussed with respect to its ramifications for male behavior, juvenile inclusive fitness, and the evolution of cooperative behavior.

No description available.

京都大学 / 新制・課程博士 / 博士(理学) / 甲第24459号 / 理博第4958号 / 新制||理||1708(附属図書館) / 京都大学大学院理学研究科生物科学専攻 / (主査)教授 本川 雅治, 准教授 中野 隆文, 教授 中務 真人 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DGAM

Sexual selection shaped psychological mechanisms in both sexes to assess potential mates for evidence of mate quality (Buss, 2005). Attraction preferences are one such mechanism (Sugiyama, 2005) and physical attraction preferences are sensitive to fitness-promoting traits present in a potential mate. Physically attractive traits are thought to act as signals of good genetic quality (Neff & Pitcher, 2005) and are preferred because of the advantage such quality bestows towards reproductive success. Specifically, genetic quality is proposed to be a biological requirement necessary for physically attractive traits to develop and be maintained (Johnstone & Grafen, 1993). Furthermore, genetic quality is heritable to offspring, thereby increasing offspring reproductive success (Orr, 2009). All mating decisions inherently involve trade-offs due to costs inflicted on time and resources when choosing a long-term mate. Assessing a mate for genetic quality is imperative to ensuring one selects a quality mate with heritable fitness benefits towards offspring reproductive success (Buss, 2005). In order to minimize costs and maximize benefits when making mate selection decisions, humans use multiple and redundant signals of mate quality (Fink & Penton-Voak, 2002; Møller & Pomiankowski, 1993). Accordingly, this study supposed that siblings act as redundant signals of genetic quality that would factor into mating decisions. Because genetic quality is heritable (Houle, 1991) and visible through physical attractiveness (Thornhill & Gangestad, 1999), this study explored the possibility that knowledge of relatedness influenced attractiveness judgments of human faces. Supporting the main hypothesis of the current study, siblings affected judgments of physical attractiveness for target faces. Analyses showed this effect to be driven entirely by female raters for both male [t(62)=3.87, p<.001] and female [t(61)=2.24, p=.029] target faces. Secondary analyses examining the effects of sibling pair attractiveness differences (low vs. high) showed that relatedness significantly increased female ratings of facial attractiveness for both low and high facially attractive male and low facially attractive female target faces. Results offer two possible conclusions as to the role relatedness may serve in mate quality assessments that align with parental investment as well as kin selection assumptions.