Browsing by Subject "Mate choice"
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Item The cognitive biology of mate choice in túngara frogs (Physalaemus pustulosus)(2010-05) Akre, Karin Lise; Ryan, Michael J. (Michael Joseph), 1953-; Cummings, Molly E.; Domjan, Michael; Fuiman, Lee A.; Mueller, Ulrich G.Sexual selection is responsible for a great diversity of elaborate male traits. A general female preference for males that have exaggerated traits drives this process, but the reasons females exhibit this preference are often unclear. Recent advances in understanding signal evolution have emerged from studies of receiver psychology that focus on how receivers perceive and process communication signals. I apply the perspective of receiver psychology to understand female preference for elaborate signals in túngara frogs (Physalaemus pustulosus). Male túngara frogs produce advertisement calls of variable complexity. Females exhibit a strong preference for complex to simple calls, but previous studies have not found consistent patterns of preference between calls of variable complexity. In my doctoral research, I investigate the function of variable complexity in túngara frogs. Specifically, I address the following questions: 1) Are calls of variable complexity especially relevant to females in certain contexts? Do males respond to female behavior by increasing their production of complex calls? 2) Does male to female proximity influence female response to call complexity? 3) Are females constrained by their perceptual biology in discriminating differences in call complexity? 4) Can females remember attractive males over silences between bouts of advertising? Is working memory for attractive males dependent upon signal complexity? And 5) Does signal memorability increase with signal complexity in a linear relationship? These studies provide several new perspectives to an understanding of female preference for elaborate signals. Phonotaxis experiments demonstrate that females use elicitation behaviors to influence male production of complex calls, that proximity influences female response to signal elaboration, that females are constrained by their perceptual biology in discriminating between complex calls, that memory can influence the evolution of signal complexity, and that memorability and signal complexity share a non-linear relationship.Item The development and execution of mate choice in túngara frogs(2009-05) Baugh, Alexander Taylor; Ryan, Michael J. (Michael Joseph), 1953-Interest in the question of when and how species recognition and mate preferences emerge in animals with strong species-typical predispositions has faded since the time of the classical ethologists. In its place, the role of plasticity has surfaced as a central emphasis in the study of animal behavior. Here, I step back and examine the origin and execution of sexual behavior in a tropical frog for which auditory predispositions are key. These experiments challenge assumptions about behavioral development, auditory perception, and stereotyped behavior. First, I illustrate when and how a sex- and species-typical behavior—conspecific phonotaxis—emerges during development. This study demonstrates that phonotaxis, presumably restricted to mature females, is present in both sexes early in postmetamorphic development—potentially long before such behavior might serve an adaptive function. I place this result in the context of hypotheses regarding the development of learned versus non-learned behaviors, and in light of the potential for perception to be altered by physiological changes occurring concomitantly with ontogeny. Next, I describe a set of dynamic mate choice studies that highlight how decision-making in a relatively simple system is more flexible, and less stereotyped, than was previously assumed. Results here show that frogs temporally update their mate choice decisions in a moment-to-moment fashion as advertisement signals change in real time. By decomposing the decision-making process, I determine the stimulus parameters essential for commitment to an initial phonotactic approach. These studies are followed up by experiments that reveal a high level of individual variation in female choosiness during mate choice. Lastly, I describe a mate choice study that revealed categorical perception in frogs, the first “lower” vertebrate now known to exhibit a perceptual mode previously considered a hallmark of “higher” organisms. Collectively, I make the following arguments: (1) constraints on sensory systems play a larger role in shaping behavior than is generally appreciated, irrespective of the involvement of learning; (2) unstudied sources of variation may contribute significantly to the raw material for sexual selection; and (3) phonotaxis in anurans amphibians is not the simple, stereotyped behavior that has been suggested of it in the past.Item Deviation from panmixia via assortative mating and divergent habitat preferences(2014-12) Jiang, Yuexin, Ph. D.; Bolnick, Daniel; Kirkpatrick, Mark, 1956-; Singer, Michael; DeAngelis, Donald; Leibold, MathewThe speciation process is often viewed to start from panmictic populations. Understanding the evolutionary mechanisms that cause populations to deviate from panmixia is essential to understanding the initial stage of population divergence that may lead to speciation. My dissertation focuses on the evolution of two mechanisms that cause deviation from panmixia: assortative mating and divergent habitat preferences. The first chapter is a meta-analysis on published measures of the strength of assortative mating within natural animal populations. Results showed that deviation from panmixia via weak positive assortative mating was typical within natural animal populations, while disassortative mating was rare or absent. Results also suggested that assortative mating did not typically evolve adaptively, but instead as an incidental consequence of other mechanisms, such as spatial segregation. Divergent habitat uses are important drivers of spatial segregation. The second chapter revealed a behavioral mechanism of divergent habitat uses between parapatric lake and stream threespine stickleback populations. The results showed strong divergent rheotaxis between lake and stream fish during their breeding season. The divergence is likely to contribute to the sorting of lake and stream fish into their natal habitats and promote habitat-based assortative mating. The third chapter focused on the neuroanatomical and morphological mechanisms of rheotaxis. Results showed significant correlations between the numbers of neuromasts (functional units of the lateral line) and rheotaxis in both lab-reared and wild-caught threespine stickleback. Results also showed heritable divergence in lateral line structure between parapatric lake and stream stickleback, suggesting that divergent rheotaxis and the resulting divergent habitat uses are likely to have a heritable component. In summary, my dissertation revealed ultimate evolutionary mechanisms of assortative mating and proximate evolutionary mechanisms of divergent habitat uses. These results shed light on the understanding of the beginning of population divergence and ultimately speciation.Item Experience and mate choice in sailfin mollies (Poecilia latipinna)(2014-05) Stewart, Audrey Julia; Ryan, Michael J. (Michael Joseph), 1953-Learning and experience shape mate preferences in many species. My thesis investigates the role of experience on mating behavior of male and female sailfin mollies (Poecilia latipinna). In the first chapter I explore whether adult experience influences male sailfin molly mate preference for their sexual parasite, the Amazon molly (Poecilia formosa), and whether experience could account for reproductive character displacement (RCD) of male mate preference in this species. Sailfin males from sympatric populations show a stronger preference for conspecific females over Amazon mollies than do males from allopatric populations. I exposed males from sympatric and allopatric populations to either a sailfin female or an Amazon prior to a mating trial with an Amazon. For the allopatric population, males with recent experience with an Amazon directed fewer mating behaviors towards an Amazon during mating trials than did males with recent experience with a sailfin. Males from the sympatric population, however, performed the same amount of mating behaviors towards an Amazon regardless of experience. Thus adult experience influences mating preferences and suggests that experience may play a role in RCD in this species. In the second chapter I investigate whether a learned sensory bias could influence female mate preferences. Sensory biases that influence mate preferences can arise through selection on the sensory system in foraging and predator detection domains. I tested whether a learned preference originating outside of the mating domain, specifically a color-based food preference, can be transferred to a color-based preference for a male trait. I trained female sailfin mollies to associate either green or blue with food and then tested their preference for animated male sailfins featuring either a blue or green spot. I found that females did not prefer the male with the same color spot to which they had been conditioned. I discuss the problem of learned preference transfer and suggest directions for future research into the role of learning in sensory bias.Item Influences of predation risk on mate evaluation and choice in female túngara frogs, Physalaemus pustulosus(2010-05) Bonachea, Luis Alberto; Ryan, Michael J. (Michael Joseph), 1953-; Muller, Ulrich G.; Pianka, Eric R.; Bolnick, Daniel I.; Bell, Chris J.Female choice is an important selective force shaping the evolution of communication and speciation in animals. However, predation risk can impose severe costs on longer searches and choosiness, thereby limiting the expression of female preferences for specific male traits. The work detailed in this dissertation explores how mate choice and sexual selection can be influenced by predation risk in túngara frogs. I begin by examining the effects of multiple simulated cues of predation risk on female search behavior and mate choice, taking a departure from the standard presence/absence paradigm used in similar studies to explore responses to quantitative variation in perceived predation risk. I demonstrate that light, longer travel times, and acoustic cues of predators are all sufficient to sway females away from otherwise more attractive conspecific males. Next, I explore the role of predation risk in altering female permissiveness, or the range of signals females will respond to. Using an artificial series of calls intermediate between heterospecific and conspecific, I demonstrate that predation risk dramatically increases the range of signals females will respond to, including a small number of females choosing pure heterospecific calls. Next I attempt to bridge a logical gap with our understanding of search costs, testing questions about how female search paths change with increasing distance. I demonstrate that females use more direct paths and move faster under higher light conditions, potentially reducing sampling but also reducing encounter rates with predators. Lastly, I examine factors that influence how individual females vary in their response to perceived risk, particularly hormonal state and experience. I demonstrate that naïve, captive-bred females respond to acoustic cues produced by natural predators in a manner similar to wild females and that, while hormonal state is obviously important in determining female receptivity, it has little effect directly on how females respond to predators. Together, these studies demonstrate that predation risk not only changes how females respond to conspecific males, but also increases female permissiveness and constrains search behavior. Predation risk can strongly influence and potentially even negate the expression of female preferences, having profound consequences for communication and the evolution of reproductive isolation between populations.Item Investigating the female mate preference brain : identifying molecular mechanisms underlying variation in mate preference in specific regions of a swordtail (Xiphophorus nigrensis) brain(2011-05) Wong, Ryan Ying; Hofmann, Hans A.; Cummings, Molly E.; Ryan, Michael J.; Crews, David; Zakon, Harold H.Choosing with whom to mate is one of the most important decisions a female makes in her lifetime and inter-individual variation of these preferences can have important evolutionary consequences. In order to get a complete understanding of why and how females choose a mate, we must identify factors that can contribute to variation of female mate choice. Many decades of research sought to understand ultimate mechanisms of female mate choice with proximate mechanisms receiving a lot more attention in recent years. For my thesis, I identify intrinsic and extrinsic factors that correlate with individual variation of female Xiphophorus nigrensis mate preference. I provide evidence that a female’s size (e.g. age and sexual experience) as well as male behavioral displays can predict female mate preference. Using genes associated with female mate preference (neuroserpin, neurologin-3), I identify four brain regions (Dl, Dm, HV, POA) that show significant differences in gene expression between females exhibiting high preference for males relative to females displaying little mate preference. Neuroserpin and neuroligin-3 gene expression within these brain regions are also positively correlated with female mate preference behavior. Two of these brain regions (Dm and Dl) integrate multisensory information and are found in the putative teleost mesolimbic reward circuitry; the other two regions (HV and POA) are involved in sexual behaviors. With the implication of the reward circuitry, I assess whether there are changes in dopamine synthesis (via tyrosine hydroxylase, TH) in dopaminergic brain regions associated with the degree of mate preference. I do not find evidence of rapid changes (within 30 minutes) of TH expression (i.e. dopamine synthesis) in dopaminergic brain regions related to variation in female mate preference. Collectively my results suggest that mate preference behavior in the brain may be coordinated not just through regions associated with sexual response but also through forebrain areas that may integrate primary sensory information, with no associated changes of a proxy for dopamine synthesis in dopaminergic brain regions.Item Mate choice and hybridization within swordtail fishes (Xiphophorus spp.) and wood warblers (family Parulidae)(2011-05) Willis, Pamela Margaret; Ryan, Michael J. (Michael Joseph), 1953-; Bolnick, Daniel I.; Mueller, Ulrich G.; Rosenthal, Gil G.; Singer, Michael C.Behavioral isolation is an important barrier to gene flow, contributing to the formation and maintenance of animal species. Nevertheless, hybridization occurs more commonly than is generally recognized, occurring in over ten percent of animal species in the wild. Although the genetic consequences of hybridization are of considerable interest given their evolutionary implications, the reasons that animals choose to mate with other species are less clear. I apply mate choice theory to the question of hybridization, using wood warblers (family Parulidae) and swordtail fishes (genus Xiphophorus) as study systems. Over half of the 45 species of North American wood warbler have produced hybrids. Using comparative methods, I address the questions: Do ecological and demographic factors predict hybridization in this family? Similarly, how do phylogeny, song similarity, and sympatry with congeners correlate with hybridization? As with North American wood warblers, behavioral isolation is also considered of primary importance in isolating sympatric species of swordtail fishes. Two species, X. birchmanni and X. malinche, hybridize in several locations in the wild. Through experimentation with these and other Xiphophorus species, I investigate some of the factors that cause female mate choice to vary, possibly contributing to hybridization. Specifically, I address the following questions: Do females become less choosy when predation risk is high, or encounter rates with conspecifics are low? Are female preferences for conspecifics innate, or can they be modified by experience? And, do female preferences for conspecifics vary among species, populations, or experiments? These studies illustrate the utility of treating hybridization as just another possible outcome of variation in mate choice. I find that warbler hybridization correlates with ecological and other variables, that female swordtails become more responsive to heterospecifics when mate choice is costly, and that female preferences for conspecifics are species- and context-dependent. As animal hybridization can have important evolutionary consequences, studying the factors that contribute to this variation can enhance our understanding of the evolutionary process.Item Mating evolution in Gambusia (Poeciliidae) : an integration of behavior, molecules and morphology(2014-05) Wang, Silu; Cummings, Molly E.; Hofmann, Hans A; Ryan, Michael JFemale mate choice and male courtship display are critical behaviors for the understanding of character evolution driven by sexual selection. This thesis is designated to understand the evolutionary mechanism of these two behaviors with mosquito fish (Gambusia). In the first chapter, collaborated with Dr. Mark Kirkpatrick, we demonstrated positive coevolution of courtship display and morphological signatures of male coercion and male advantage in sexually antagonistic adaptation across 10 Gambusia species. This finding suggested that male display may have caused the evolution of morphologies involved in SAC, or conversely it may have evolved as a palliative byproduct of the morphologies. This unexpected observation raised new interpretation about evolutionary cause and consequence of displays across different mating systems. The second chapter examined whether neuromolecular underpinning of G. affinis female mate choice is canalized or plastic in mating systems that show variable extant of mate choice. With Dr. Mary Ramsey, we should positive correlations between gene expression and female preference strength during exposure to courting heterospecific males, but a reversed pattern following exposure to coercive heterospecific males. This suggested that the neuromolecular entities associated with female preference are plastic and responsive to different male phenotypes (courting or coercive) rather than a canalized response linked to mating system. Further, I proposed that female behavioral plasticity may involve learning because female association patterns shifted with experience/age. Compared to younger females, I find that more experienced females spend less time near coercive males but associate more with males in the presence of courters. We thus suggested a conserved learning-based neuromolecular process underlying the diversity of female mate preference across the mate choice and coercion-driven mating systems.Item Polymorphic mating signals and female choice in an Amazonian frog(2014-12) Guerra, Mónica Alexandra; Ryan, Michael J. (Michael Joseph), 1953-; Cannatella, David C.; Phelps, Steve; Mueller, Ulrich; Funk, ChrisSexual selection, more specifically mate choice, is one of the most important mechanisms responsible for signal evolution and assortative mating. My thesis integrates genetic analysis, behavioral assays and morphological observations to understand the evolution of polymorphic male mating signals in the frog Peters’ Dwarf Frogs (Physalaemus petersi). In this frog, different populations form distinct genetic clades that coincide with the type of advertisement call males produce. My thesis has four chapters: the first chapter investigates the role of sexual selection in the origin and maintenance of polymorphic mating signals and its consequences for reproductive isolation. I demonstrate strong female mate choice for male signals at a sympatric site. I propose that sexual selection is responsible for the maintenance of different call morphs in sympatric populations, and it likely contributed to the origin of polymorphic male signals. Males of P. petersi form choruses. Males that produce different call morphs are found calling together in sympatric populations. This set up the question if Peters’ Dwarf Frogs use acoustic cues to join choruses in nature. In the second chapter, I demonstrated that the males perform phonotaxis to choruses of similar call frequency. Along with the previous studies of female phonotaxis, the results suggest the pattern of discrimination of males and females are similarly based on the frequency of the call. Evolution of some behaviors results from changes in morphology; for instance, advertisement calls are normally restricted to males, which have larger larynges and muscles than females. In the third chapter, I investigate the ontogenetic morphological differences between males and females of a model in animal communication and close relative of P. petersi, the túngara frog, Physalaemus pustulosus. The results constitute the first comparison between males and females in the ontogeny of the vocal apparatus of a common frog, and contribute to the general knowledge of developmental differences in sound-producing organs. Lastly, in the fourth chapter, I investigated the developmental differences between males of two populations of Peters’ Dwarf Frog that produce different types of calls. I found the laryngeal growth is significantly different between P. petersi males that produce different types of calls.Item The Quantitative Genetics of Mate Choice Evolution: Theory and Empiricism(2012-11-15) Ratterman, Nicholas 1981-The evolution of mate choice remains one of the most controversial topics within evolutionary biology. In particular, the coevolutionary dynamics between ornaments and mating preferences has been extensively studied, but few generalizations have emerged. From a theoretical standpoint, the nature of the genetic covariance built up by the process of mate choice has received considerable attention, though the models still make biologically unrealistic assumptions. Empirically, the difficulty of estimating parameters in the models has hindered our ability to understand what processes are occurring in nature. Thus, it is the goal of this dissertation to contribute to the field both theoretically and empirically. I begin with a review of the evolution of mate choice and demonstrate how the lack of cross-talk between theoretical and empirical pursuits into studying mate choice has constrained our ability to extract basic principles. The review is followed by a new model of intersexual selection that relaxes some of the critical assumptions inherent in sexual selection theory. There are two empirical studies whose goal is to measure mating preference functions and genetic correlations in a way that can be related back to theory. Finally, I conclude by setting the stage for future endeavors into exploring the evolution of mate choice. The results presented herein demonstrate four things: (i) a lack of communication between theoretical and empirical studies of mate choice; (ii) genetic drift plays a much larger role in preference evolution than previously demonstrated; (iii) genetic correlations other than those explicitly modeled are likely to be important in preference evolution; and (iv) variation in mating preferences can eliminate intersexual selection altogether. From these four findings it can be concluded that a tighter link between theory and empiricism is needed, with a particular emphasis on the importance of measuring individual-level preference functions. Models will benefit from integrating the specific phenotypes measured by empiricists. Experimentation will be more useful to theory if particular attention is paid to the exact phenotypes that are measured. Overall, this dissertation is a stepping stone for a more cohesive and accurate understanding of mate choice evolution.Item When chytrid doesn't kill : how it spread in túngara frogs and how females might avoid it(2016-12) Rodríguez Brenes, Sofía Maciel; Ryan, Michael J. (Michael Joseph), 1953-; Bolnick, Daniel I; Cannatella, David C; Mueller, Ulrich G; Puschendorf, RobertMy dissertation aims to examine how pathogen-induced stress might affect reproductive behaviors such as sexual communication, mate choice, and reproductive success. To pursue this topic I studied the interaction between an emergent infectious disease, chytridiomycosis, caused by the chytrid fungus Batrachochytrium dendrobatidis (Bd), and the tropical tungara frog as its host. The first goal of the dissertation was to understand the basic epidemiology of chytridiomycosis in this wide-spread tropical lowland anuran. From 2010 to 2015, I sampled annually for the presence of B. dendrobatidis in populations of tungara frog along an approximately 750 km transect, ranging from the mountains of western Panama to inside the Darien Gap. Highland populations in western Panama were already infected with B. dendrobatidis at the start of the study. In central Panama, I collected the first positive samples in 2010, and by 2014, I detected B. dendrobatidis in samples from remote sites in eastern Panama (Darien National Park) where B. dendrobatidis had not been documented before. I discuss the importance of studying B. dendrobatidis in lowland species, which may serve as potential reservoirs and agents of dispersal of B. dendrobatidis to highland species that are more susceptible to chytridiomycosis. The second goal of my thesis was to understand how B. dendrobatidis might influence frog reproductive behavior. Some anuran species, including the tungara frog, seem to be tolerant to chytridiomycosis, but for others it is lethal. Tolerant species carry the pathogen, but do not exhibit symptoms of chytridiomycosis and their populations are not declining. Although chytridiomycosis might not be lethal for such tolerant species, it might nonetheless have other long-term effects. Such sub-lethal effects of chytridiomycosis have received little research attention. I examined how the potential pathogen-stress effects induced by B. dendrobatidis influence reproductive behavior such as sexual communication, mate choice, vigor, and reproductive success in the tungara frog. I tested the hypothesis that B. dendrobatidis influences the male mating call, and that females can use mating call cues to assess B. dendrobatidis infection. I performed female phonotaxis experiments to determine if males infection with B. dendrobatidis influences female mate choice, and I determined if there is a cost of the response to the infection in offspring number and development. Overall, the research presented here improves our understanding of the physiological and behavioral trade-offs confronted by a species during response to a pathogen and shows that B. dendrobatidis can have long-term population-level effects in tolerant species that are not severely affected by the disease. In addition to frogs and salamanders, emerging infectious diseases affect a number of other important lineages including honeybees, bats, birds, and humans. Study of the effects of non-lethal infections might therefore have more general application towards our understanding of the interactions between devastating pathogens and their wildlife hosts.