Function of weaponry in females: the use of horns in intrasexual competition for resources in female Soay sheep

In many species, females show reduced expression of a trait that is under sexual selection in males, and this expression is thought to be maintained through genetic associations with the male phenotype. However, there is also the potential for the female trait to convey an advantage in intrasexual conflicts over resources. We tested this hypothesis in a feral population of Soay sheep, in which males and females have a polymorphism for horn development, producing either full (normal horned), reduced (scurred) or no (polled, females only) horns. During the lambing period, females who possessed horns were more likely to initiate and win aggressive interactions, independent of age, weight and birthing status. The occurrence of aggression was also context dependent, decreasing over the lambing period and associated with local density. Our results demonstrate that a trait that confers benefits to males during intrasexual competition for mates may also be used by females in intrasexual competition over resources: males use weaponry to gain mates, whereas females use weaponry to gain food

Explaining additional genetic variation in complex traits

Genome-wide association studies (GWAS) have provided valuable insights into the genetic basis of complex traits, discovering >6000 variants associated with >500 quantitative traits and common complex diseases in humans. The associations identified so far represent only a fraction of those that influence phenotype, because there are likely to be many variants across the entire frequency spectrum, each of which influences multiple traits, with only a small average contribution to the phenotypic variance. This presents a considerable challenge to further dissection of the remaining unexplained genetic variance within populations, which limits our ability to predict disease risk, identify new drug targets, improve and maintain food sources, and understand natural diversity. This challenge will be met within the current framework through larger sample size, better phenotyping, including recording of nongenetic risk factors, focused study designs, and an integration of multiple sources of phenotypic and genetic information. The current evidence supports the application of quantitative genetic approaches, and we argue that one should retain simpler theories until simplicity can be traded for greater explanatory power

Selection and genetic variation of weaponry in a large mammal

Understanding the maintenance of the variation that is typically observed in natural populations has been a central aim of evolutionary biology. In a feral population of Soay sheep on the island of Hirta, St.Kilda there is a phenotypic polymorphism for horns with males growing either normal or reduced (scurred) horns, and females growing either normal, scurred or no (polled) horns, with further variation in horn size within each of the horn types. This thesis examines the potential factors which maintain these polymorphisms. I first present an overview of the literature relating to the factors that potentially maintain variance in traits in natural populations. In chapter two I present an analysis that suggests that polymorphisms in both horn type and horn size may be maintained by trade-offs between allocation to reproductive success and survival in males, and by sexually antagonistic selection between males and females. In chapter three I test the hypothesis that female weaponry may convey an advantage in intrasexual conflicts over resources, rather than just being expressed as a consequence of genetic associations with the male phenotype. Chapter four examines the environmental factors which create variation between individuals in their horn length, revealing that individuals vary in response to the environment. In chapter five I investigate whether the temporally fluctuating environmental conditions of St.Kilda generate fluctuating selection on the horn length of normal-horned males, revealing that this mechanism constrains the evolution of horn length potentially maintaining variance. In chapter six I examine the genetic relationships between morphological traits, revealing that these relationships are dependent upon the environmental conditions experienced during the first year of life. Finally, I discuss the wider implications of these findings for our understanding of the maintenance of trait variation in the wild

PinR mediates the generation of reversible population diversity in Streptococcus zooepidemicus

Opportunistic pathogens must adapt to and survive in a wide range of complex ecosystems. Streptococcus zooepidemicus is an opportunistic pathogen of horses and many other animals, including humans. The assembly of different surface architecture phenotypes from one genotype is likely to be crucial to the successful exploitation of such an opportunistic lifestyle. Construction of a series of mutants revealed that a serine recombinase, PinR, inverts 114 bp of the promoter of SZO_08560, which is bordered by GTAGACTTTA and TAAAGTCTAC inverted repeats. Inversion acts as a switch, controlling the transcription of this sortase-processed protein, which may enhance the attachment of S. zooepidemicus to equine trachea. The genome of a recently sequenced strain of S. zooepidemicus, 2329 (Sz2329), was found to contain a disruptive internal inversion of 7 kb of the FimIV pilus locus, which is bordered by TAGAAA and TTTCTA inverted repeats. This strain lacks pinR and this inversion may have become irreversible following the loss of this recombinase. Active inversion of FimIV was detected in three strains of S. zooepidemicus, 1770 (Sz1770), B260863 (SzB260863) and H050840501 (SzH050840501), all of which encoded pinR. A deletion mutant of Sz1770 that lacked pinR was no longer capable of inverting its internal region of FimIV. The data highlight redundancy in the PinR sequence recognition motif around a short TAGA consensus and suggest that PinR can reversibly influence the wider surface architecture of S. zooepidemicus, providing this organism with a bet-hedging solution to survival in fluctuating environments

Free Fermionic Heterotic Model Building and Root Systems

We consider an alternative derivation of the GSO Projection in the free fermionic construction of the weakly coupled heterotic string in terms of root systems, as well as the interpretation of the GSO Projection in this picture. We then present an algorithm to systematically and efficiently generate input sets (i.e. basis vectors) in order to study Landscape statistics with minimal computational cost. For example, the improvement at order 6 is approximately 10^{-13} over a traditional brute force approach, and improvement increases with order. We then consider an example of statistics on a relatively simple class of models.Comment: Standard Latex, 12 page

New County Records of Amphibians and Reptiles from South Texas, USA

Several species of amphibians and reptiles reach their northern range limit in south Texas, USA. Herpetological research in the area, as well as frequent visits from amphibian and reptile enthusiasts, have helped to form a more complete understanding of amphibian and reptile distributions across the region. However, gaps in the recognized distribution of many species remain. Efforts to better document species occurrence are confounded by the lack of public land and the fact that most of south Texas is privately owned, making access to suitable habitat difficult (Schmidly et al. 2001