Differential gene expression and morphological variation in tequila bats (Leptonycteris yerabauenae)

: adaptations to migration

Abstract

The study of migration has mainly focused on understanding the patterns and routes that animals follow, and how these movements affect the genetic composition of populations. Studies on the morphology of wings coupled with predictions of the aerodynamic theory have shown that even the slightest differences in the shape of wings can have a significant effect on the foraging behaviour and flying ability of bats. More recently, genomic studies opened the door to understand the genetic makeup responsible for triggering and controlling the behaviour. In this thesis, I used genetics to test if the tequila bat (Leptonycteris yerbabuenae) is maintaining matrilineal gene flow across its range. Using mtDNA I show that the populations of southern, central and northern Mexico belong to the same species and do not show clear patterns of population structuring but that two haplotype groups may exist. Gene flow is maintained across its range with differences in migratory behaviour observed between the northern and southern populations. My analysis on wing morphology shows that the migratory population has wings with higher aspect ratio and more pointed wing tips that allow them to sustain long-distance flight better than the resident populations; in contrast, the non-migratory populations show morphological adaptations to manoeuver better in a more cluttered environment including a shorter humerus, lower aspect ratio and wing loading. By looking at differences in gene expression I was able to detect potential genes influencing the migratory behaviour. Migratory bats appear to have the genetic potential to build more synaptic connections that may allow them to store new information from the environment and show higher expression of genes associated with exploration behaviour compared with resident populations; furthermore, I show that circadian clock genes, influenced by the environment, may contribute to the regulation of the expression of migration. My results on the gene expression of blood show that migratory bats and have a high immune tolerance toward pathogens explained by a diversity of MHC complexes, natural cell killers, antiviral interferons and other immune regulatory elements, traits that could explain how these animals stay healthy despite the inherently challenging task of migrating and moving to new areas potentially containing novel pathogens. This project opens the door to future studies on the mechanisms controlling migration in bats and offers a novel way to understand how genes and the environment paved the way for the evolution of migration, and how phenotypic plasticity continues to shape these organisms.

Date of Award	19 Mar 2019
Original language	English
Awarding Institution	University of Bristol
Supervisor	Gareth Jones (Supervisor)