Unravelling the mystery of migratory behaviour in the Bogong moth Agrotis infusa using genomics and novel automated monitoring techniques

Abstract

An exceptionally impressive example of animal navigation is presented by the Bogong moth Agrotis infusa, that migrates over 1000 km from widely distributed winter breeding grounds to a relatively confined summer range in the Australian Alps, consistently arriving to the same sites as its predecessors, despite never having an opportunity to learn the migratory route, or indeed, the location of its destination. The Bogong moth then waits out the summer in a dormant state known as aestivation, lining the walls of cool cracks and crevices in high altitude granite outcrops, where it forms massive assemblages with an estimated 17000 moths per square metre. Recent and ongoing investigations into the sensory and neurological capabilities of the Bogong moth have revealed that it possesses a "compass sense" that relies on geomagnetic and stellar information. However, since the migratory direction of the Bogong moth varies across its breeding range, a compass is not sufficient on its own for the moth's navigation. How, for instance, does a Bogong moth know - given its starting location - in which direction to migrate? The objective of this thesis is to understand the basis of the Bogong moth migratory direction. Even though this thesis opens as many questions as it answers, significant progress towards achieving this objective is presented (in two parts) herein, primarily through development of the scientific infrastructure for studying Bogong moth biology more generally. Part I introduces a new method for quantitatively measuring Bogong moth activity and abundance using automated camera-based detection, which is then used to model the influence of abiotic factors on Bogong moth behaviour, and to measure the arrival, departure, and population dynamics of the moths in their summer range. In addition to its utility in addressing ethological questions, this new method enables quantitative long-term monitoring of the Bogong moth population, which may prove invaluable for conservation efforts (the Bogong moth has recently been assessed as endangered for the IUCN Red List). In part II, the annotated sequence of the Bogong moth genome is presented, opening the door to high-throughput molecular research on the moth. Extensive differential gene expression in the sensory and brain tissue of migrating and aestivating moths is observed, along with evidence of epigenomic modification. Finally, the results of re-sequencing the genomes of 77 Bogong moths collected from across their breeding and summer ranges are presented, which show that the Bogong moth population is panmictic, and harbours a vast quantity of rare genetic variants. Interestingly, a small number of variants are highly correlated with migratory direction, indicating promising avenues for further research into the genetic basis of migratory direction.