Ph.D. student, University of Sheffield
The ability of a species to adapt to the local environment is one of the key processes that generate and maintain biodiversity. In the absence of adaptation, the changing environment drives the species to extinction. The process is fuelled by divergent selection pressures that act on the populations in distinct environments. The selection acts on the inherent variations present in the population; with the traits which render the individuals with better survivability and reproduction prevailing in that population under that environment. Over generations, this cause accumulation of differences between populations in different environments. The migration of individuals from one population to other, which are under different selection pressures, opposes the selection as it increases gene flow. At the same time, migration increases variation in the populations, a key requirement for selection. This is a poorly understood mechanism that finds practical implications in biodiversity management- when is it advantageous to facilitate migration as opposed to local adaption? The study system of the marine snail Littorina saxatilis lets us examine this poorly understood interaction between dispersal and adaptation in the wild. The two diverging ecotypes of the snail can be observed across Europe on the rocky shores. Few meters apart, the two ecotypes live in distinct habitats and face different selection pressures- one of crab predation, other of wave action. To adapt, these ecotypes have acquired traits which make them structurally and behaviourally distinct. Despite this, these ecotypes meet in small contact zones and hybridize. These hybrid zones are natural laboratories which allow the ecologists to study which traits are diverging and facilitating adaptation. Theory suggests that adaptation is dependent on the genetic architecture of the traits underlying divergent selection. My research is to elucidate the genetic architecture of such divergent traits in this species. I have been able to identify the principal traits under selection and through association analysis in multiple contact zones on the western coast of Sweden, identify what are the genes associated with these traits. Principles developed through this study can be extrapolated to common species that provide ecosystem services.
Abstract: Studies of the genetic basis of adaptive changes in natural populations are now addressing questions that date back to the beginning of evolutionary biology, such as whether evolution proceeds in a gradual or discontinuous manner, and whether convergent evolution involves convergent genetic changes. Studies that combine quantitative genetics and population genomics provide a powerful tool for identifying genes controlling recent adaptive change. Accumulating evidence shows that single loci, and in some cases single mutations, often have major effects on phenotype. This implies that discontinuous evolution, with rapid changes in phenotype, could occur frequently in natural populations. Furthermore, convergent evolution commonly involves the same genes. This implies a surprising predictability underlying the genetic basis of evolutionary changes. Nonetheless, most studies of recent evolution involve the loss of traits, and we still understand little of the genetic changes needed in the origin of novel traits.
Pub.: 21 Sep '10, Pinned: 14 Sep '17
Abstract: Changes in environmental conditions can rapidly shift allele frequencies in populations of species with relatively short generation times. Frequency shifts might be detectable in neutral genetic markers when stressful conditions cause a population decline. However, frequency shifts that are diagnostic of specific conditions depend on isolating sets of genes that are involved in adaptive responses. Shifts at candidate loci underlying adaptive responses and DNA regions that control their expression have now been linked to evolutionary responses to pollution, global warming and other changes. Conversely, adaptive constraints, particularly in physiological traits, are recognized through DNA decay in candidate genes. These approaches help researchers and conservation managers understand the power and constraints of evolution.
Pub.: 09 May '08, Pinned: 14 Sep '17