Organisms face the allocation problem of investing resources in different traits. Investment strategies are expected to maximise fitness by balancing the costs and benefits of investing in multiple traits used in diverse contexts, including acquiring territories, food, and mates. The trade-offs associated with trait investment are likely to be dynamic. For example, ecological factors, such as climate, temperature, and diet, and demographic factors, such as male and female densities and sex ratio, can affect trade-offs and, thereby trait investment. 

Many animals show strikingly exaggerated traits like antlers in Cervids. Such traits represent costly trade-offs because they decrease the residual resources available for allocation to other traits. Moreover, individuals within a population often exhibit variation in exaggerated traits, with relative trait sizes increasing with body size. This pattern of positive allometry where individuals ‘invest disproportionately more resources to traits as body sizes are larger’ has been proposed to be due to sexual selection. However, studies have also suggested that sexually selected traits might not universally display positive allometry; these studies provide examples of sexually selected traits that show slight negative to isometric scaling. More recent studies have proposed that whether sexually selected traits show positive allometry depends on the trait's behavioural context and functional relevance.   

A long history of examining resource investments using the approach of allometry has focused on quantifying how behaviours, morphology, and other traits scale with body size. Our understanding of the processes underlying the maintenance of positive allometry in a population is limited. Specifically, investigations of how dynamic changes in ecological and demographic factors affect positive allometry are few. Moreover, empirical studies investigating how trait allometries contribute to individual fitness are scarce. Such studies are necessary for deciphering the selective factors maintaining positive allometry in a population. 

Using the rupicolous agamid species Psammophilus dorsalis, we aim to understand how positive allometry in morphological traits is affected by dynamic variation in the selection environment. By employing microsatellite markers for genotyping and parentage analysis, we also propose to examine the contribution of positive allometry in morphological trait to reproductive fitness. Finally, in polygynous systems like P. dorsalis, males commonly use multiple traits in the competition for mates. We also aim to understand how investment patterns and relative scaling of the focal morphological traits affect the payoffs to other traits used in the competition for mates, including the diverse set of signals. The questions in the thesis will be answered using long-term morphology and demography datasets, together with behavioural observations and field experiments.