Leptochelia dubia is a dioecious tube-building tanais, which broods its young and exhibits marked sexual dimorphism. The species is widely distributed in the Pacific, Atlantic, Mediterranean and Indian Oceans, but to date there are no published accounts of its ecology. L. dubia is one of the most abundant of the small Crustacea in Tomales Bay, where it may attain densities of 30,000/m2 in soft bottom communities.

In studies of plant-pollinator interactions, much attention has been paid to interspecific variation in foraging behaviors among pollinators and their consequences for plant reproduction and the stability of plant-pollinator communities. In contrast, there has been little consideration of intraspecific variation and its consequences. Specifically, male and female pollinators may forage differently due to differences in phenology, nutritional requirements, and behavior. Here, we compare male and female foraging patterns of the rare declining eastern regal fritillary butterfly, Speyeria idalia idalia. Using a 21-year dataset, which monitored the abundance, sex, and foraging of S. i.idalia across grasslands within Fort Indiantown Gap National Guard Training Center in Pennsylvania, USA, we asked whether males and females differed with respect to the diversity of nectar plants visited and the floral compositions which they visited. To better understand the behavior of individual butterflies and draw inferences about repercussions for plant fitness, in 2019 we collected pollen loads directly from male and female S. i.idalia in these same grasslands and compared the diversity, composition, and size of pollen loads between the sexes after identifying pollen grains to the lowest taxonomic unit. Both datasets point to the dominant use of three nectar species by both sexes, but also show evidence of sex specific foraging pattern. Males and females differ statistically, although slightly, in the composition of plant species visited and plant species per pollen load. Females visit a significantly greater diversity of plant species when accounting for both abundance and evenness of plants visited. In contrast, pollen loads found on males contained ~3 more species on average than female pollen loads, but this difference is not supported when accounting for evenness of pollen grains/species. Finally, we find individual male butterflies carry more pollen grains than females on average. Our results contribute to understanding pollinator resource use more broadly, with implications for pollination dynamics. For conservation of this rare species our results further emphasize the importance of nectar plants critically important for male and female members of S. i. idalia. / Biology

Environmental variation, an important source of phenotypic variation, can influence phenotypes, fitness and even rates of evolution. My thesis explores the effects of evolutionary change on the response to different types of environmental variation. In the first study, I examined the evolution of environmental canalization in adaptively diverged populations of Drosophila melanogaster that vary in degree of genetic canalization. I use these populations to test the congruence hypothesis which predicts that genetic canalization is a co-product of the evolution of environmental canalization and thus should be correlated. My results show that, despite adaptive evolutionary changes in morphology and genetic canalization, these populations have similar degree of variability due to environmental variation. In the second study, I explore how both variation in temperature and food quality during development influence patterns of sexual dimorphism in wing morphology in adaptively diverged populations of Drosophila melanogaster. I compare the relative contributions of adaptation, food availability and temperature on sexual size and shape dimorphism of the Drosophila wing. In particular, I focus on how these factors influence size-shape allometry both in general and in a sex-specific manner. My results show that despite the large adaptive divergence and a strong influence of environmental manipulation on wing size and shape, sex-specific patterns of condition dependence remain relatively consistent between the two populations. In the third study, I explore the evolutionary patterns of condition-dependent sexual size dimorphism among 27 different species from the melanogaster species group with varying degrees of sexual size dimorphism. Using food availability manipulations during development, I examine how sexual size dimorphism changes in response to condition at both the intra-specific and the inter-specific level. The results of this study suggest that, although we see a correlation between sexual size dimorphism and condition dependence among traits within most species, sexual dimorphism and condition dependence do not seem to have a correlated evolution among species of the melanogaster species group. / Dissertation / Doctor of Philosophy (PhD)

Studies have shown that facial sexual dimorphism, ranging on a continuum from very feminine to very masculine, affects observers’ ratings of dominance and threat. These studies, however, have used forced-choice paradigms, in which a pair of faces that have been manipulated to appear more masculine (masculinized) and feminine (feminized) are presented side by side. They are susceptible to demand characteristics, situational aspects of the experiment which produce the desired outcome, because participants may be able to draw the conclusion that faces which appear more masculine should be rated as more dominant. In this dissertation, I evaluated whether facial sexual dimorphism affects observers' threat perceptions in a way that minimizes the confounds caused by demand characteristics. In Experiment 1 and Experiment 2, I presented observers with masculinized and feminized faces individually, rather than in pairs, and for an extremely brief duration (Experiment 1). I predicted that observers would assign higher dominance (Experiment 1) and threat ratings (Experiment 2) to masculinized faces. Observers assigned higher dominance (Experiment 1) and threat (Experiment 2) ratings to masculinized faces, even when they were presented individually, and for as little as 100 milliseconds (ms) (Experiment 1). This would suggest that they can appraise differences in facial sexual dimorphism following very brief exposure. I proceeded to evaluate the effects of facial sexual dimorphism on men’s selective attention, while reducing the effects of demand characteristics, by testing for an attentional bias towards task-irrelevant masculinized men’s faces. In Experiment 3, forty-five men completed a Posner Cueing Paradigm in which they classified shapes, presented either right or left of center screen after a masculinized or feminized man’s face was presented in either the same or opposite location. Participants were faster to classify the shape following the presentation of a masculine face; however, they were not faster when a masculine face cued target position. In Experiment 4, forty-four men completed a Flanker Task in which they judged letter orientation (i.e., upright or upside-down), while ignoring flanking faces. Participants’ RT was not affected by Morph Type (i.e., whether the face was masculinized, feminized or unmodified). In Experiment 5, forty-one men completed a Dot Probe Task. They were presented with two facial photographs of different Morph Types to the left and right of center screen. This was followed by the presentation of a target shape, in the location of one of the faces. Participants’ objective was to classify shape orientation. Facial sexual dimorphism did not affect participants' classification speed. In Experiment 6, I primed participants with images meant to induce fear or arousal before each trial of a Dot Probe Task. Following the presentation of a fear inducing picture, participants RT to classify shapes when a masculinized face cued target position did not differ from when a feminized face cued target position. The two different presentation times did not create different patterns of results, indicating that masculinized faces did not induce either a cueing or inhibitory affect. Overall, my results do not support my hypothesis that men selectively attend to masculinized faces when they are presented as irrelevant information. I conclude by discussing future directions for evaluating the effects that facial sexual dimorphism has on observers’ interpersonal perceptions of threat and dominance, while controlling for the effects of demand characteristics.

Acetaminophen overdose is the leading cause of acute liver failure, with one available treatment, NAC. Yet, NAC effectiveness diminishes about ten hours after APAP overdose, urging for therapeutic alternatives. Promoting intrinsic liver regeneration could address this unmet need by temporally activating key hepatocyte regenerative pathways in order to accelerate recovery from acute APAP-induced liver injury. In aim 1, we established an efficient, safe, non-integrative method to transiently express HGF and EGF in hepatocytes via nucleoside-modified mRNA-LNP delivery in mice. We confirmed specific hepatotropism of mRNA-LNP via intravenous injection of firefly luciferase encoding mRNA-LNP, with protein expression lasting about 3 days. In the liver, virtually all hepatocytes were transfected along with a subpopulation of endothelial and Kupffer cells. In homeostasis, HGF mRNA-LNP efficiently induced hepatocyte proliferation. In a chronic liver injury mouse model recapitulating nonalcoholic fatty liver disease, injections of both HGF and EGF mRNA-LNP sharply reversed steatosis and accelerated restoration of liver function. Likewise, HGF and EGF mRNA-LNP accelerated liver regeneration after APAP-induced acute liver injury with rapid return to baseline of levels of serum liver injury markers such as ALT. This study introduced mRNA-LNP as a potentially translatable safe therapeutic intervention to harness liver regeneration via controlled expression of endogenous mitogens in vivo. In aim 2, we characterized the sexually differential injury induced between males and females following APAP overdose. Consistent with the literature, our data showed higher resistance of female mice to APAP, shown by reduced liver necrosis, cell death, and detection of serum injury markers compared to males. Moreover, our single-cell RNA sequencing analyses revealed that female hepatocytes and endothelial cells express significantly higher levels of GH receptor and GH pathway activation than male cells, while males have upregulated inflammatory and cell death pathway activation. Therefore, in aim 3, we took advantage of the greater resistance of female mice and greater activation of the GH pathway to evaluate a novel treatment for APAP-induced acute liver injury utilizing growth hormone. Sex hormones and their receptors have been implicated in driving sexual dimorphism in many liver processes. Specifically, pituitary GH secretory patterns, pulsatile in males and near-continuous in females, determine the sex bias in many liver metabolic functions. In harnessing this female-specific advantage, we demonstrated that injection of recombinant human GH protein in APAP-injured mice accelerates liver recovery, promotes survival, and is superior to standard-of-care NAC. Delivery of slow-released human GH mRNA-LNP also rescues males from APAP-induced death that otherwise occurred in control mRNA-LNP-treated mice. In conclusion, this study demonstrates a sexually dimorphic liver repair advantage in females following APAP overdose, leveraged by establishing GH as an alternative treatment, delivered either as recombinant protein or mRNA-LNP, to potentially prevent liver failure and liver transplant in APAP-overdosed patients. / 2025-11-02T00:00:00Z

No description available.

Sex estimation of unknown individuals is one of the primary goals of biological anthropologists. The adult skull is often used in sex estimation, due to its marked traits of sexual dimorphism. However, estimating skeletal sex from juvenile remains is controversial due to the uncertainty surrounding the presence of sexual dimorphism prior to sexual maturity. The aim of this study was to apply geometric morphometric shape analysis to non-adult skulls to explore patterns of sexual dimorphism during ontogeny and to identify the most dimorphic region(s) of the skull. Computed tomographic (CT) scans were acquired from the New Mexico Decedent Image Database comprising 101 male and 99 female skulls ranging in age between birth and 21 years. Three-dimensional coordinates (42 landmarks and 290 curve semilandmarks) were placed on surface models generated from the CT scan and four landmark configurations were evaluated: the anterior cranium, mandible, supraorbital margin and glabella, and mastoids. Generalized Procrustes superimposition, principal component analysis, and discriminant function analysis were applied to all four configurations independently. In line with previous studies, results demonstrated a low degree of sexual dimorphism and poor cross-validated classification accuracy in individuals less than 13 years of age, with the highest accuracy in the mandible and the anterior cranium. The shape similarities found between the sexes prior to 13 years of age prevent consideration of the craniofacial bones as a sex indicator in the early stages of development but support its use in adolescent individuals, especially when using multiple regions of the face.

No description available.

No description available.

Adult green anoles, Anolis carolinensis, exhibit numerous sex differences resulting from divergent strategies for maximizing reproductive success. I focused on the ontogeny of sex differences in behavior in juveniles, in relation to adult sex differences, by documenting the behavior of free-ranging juveniles, examining the structure and use of headbobbing displays, and determining the role of the androgen testosterone (T) in producing behavioral sex differences. Field observations indicated that juvenile males eat and forage actively more often than juvenile females. This divergent feeding behavior may result from sexual selection, given that body size is a major factor in determining the reproductive success of males. Analyses of headbobbing displays, used by adults in aggressive and sexual interactions, revealed that juvenile males and females each give the same three A, B, and C display types described for adults. However, there may be a maturational component to display structure, as juvenile displays differ from those of adults in within-display temporal structure, and are not as stereotyped. Concerning display use, social context affects neither the types of display interactions observed nor the rates of displays and related behaviors. However, size affects nearly every aspect of display behavior. Both juvenile males and females show increased display rates and probabilities of expressing display-related behaviors with increasing body size, although in the largest juveniles, male display rates become higher than those of females. These results, like those from analyses of display structure, suggest a maturational component to display use, perhaps mediated by changes in the underlying motivational states of juveniles. Consistent with the divergence in display rates in large juveniles, males of approximately 30 d of age and older have higher plasma T concentrations than females. Furthermore, juvenile males and females that have been given T implants each respond with increased behavior levels, approaching those of breeding adult males. These analyses indicate that sexual dimorphisms in behavior in adults likely arise through underlying physiological differences between males and females that mediate the expression of behavior, rather than through fundamental sex differences in the ability to perform these behaviors. / Ph. D.