Knowledge on the molecular basis of natural variation represents a crucial missing piece needed to understand the evolution of diversity. My PhD research aims to investigate heritable variation underlying two features of ladybird wings: winglessness and plasticity of colour patterns.
The two-spot ladybird (Adalia bipuncata) has a rare, naturally occurring form that has distally truncated wings. The genetics underlying this phenotype are relevant in the context of aphid biocontrol and may shed light on initial molecular changes in the evolution of winglessness in insects. Compared to research on novel traits, investigations of trait loss are limited and its evolutionary importance potentially underestimated. In insects loss of flight and/or wings has occurred repeatedly and independently across almost all winged insect orders. The two-spot ladybird provides a excellent opportunity to investigate the underlying genetics of wing loss as it is a very suitable lab organism that is genetically polymorphic for the wingless trait. Previous research in Adalia has shown that one recessive locus controls the wingless phenotype. My own work using RNAi knock-down of candidate genes provides strong evidence for the involvement of one particular pathway of the wing development gene network. I aim to confirm this finding by obtaining partial sequences of these genes using a series of backcross families, and potentially by investigating gene expression patterns.
Phenotypic Plasticity in Colour Patterns
The Harlequin or Asian ladybird (Harmonia axyridis) is an invasive species that has an extraordinary number of colour morphs. One colour form called succinea shows striking phenotypic plasticity in its colour pattern, developing a much darker phenotype when reared in a colder environment. Currently the underlying molecular mechanisms of phenotypic plasticity in general is poorly understood, and the evolutionary importance of phenotypic plasticity remains debated. For Harmonia, it is believed that their plastic ability is adaptive as darker dorsal colour patterns allow individuals in a cold environment to more effectively absorb heat from sunlight (thermal melanism). I am currently conducting a large-scale selection experiment to investigate the heritable variation underlying phenotypic plasticity in f. succinea. The two groups that are being created during the selection experiment (High and Low lines) will be a valuable resource for investigations of the genetic basis of phenotypic plasticity in this system.