Australian cockroach systematics

Giant burrowing cockroaches are a group of large (but charming!) insects found only in Australia. Though one would normally assume morphological similarity implies relatedness, it's now known these insects have acquired burrowing forms multiple times independently from wood-dwelling ancestors. This remarkable case of "parallelism" is particularly fascinating given these insects are separated by tens of millions of years of evolution. My current systematics research uses phylogenetics to look into how giant burrowing cockroach species and genera are related to one another and how the current taxonomic framework for the group might be improved.

If closely related organisms have undergone repeated and near-identical evolutionary changes over time, will they use the same genetic "toolkit" to do so in each instance? This is an intimidating question, but its answer could illuminate whether evolution is a constrained–and therefore predictable–process or a completely random one. I use burrowing cockroaches and their endosymbionts, bacteria that live inside the insects' cells, alongside phylogenetic methods to better understand the molecular basis of such changes.

Can we predict evolution? 

Blattabacterium symbionts

Blattabacterium is a bacterial endosymbiont that lives inside the fat body, similar to that of a human's liver, in almost all cockroach species. Cockroaches subsist on very nitrogen-poor diets, but Blattabacterium acts as something of a recycling depot for their hosts by metabolising their nitrogenous waste into essential amino acids.

 

What of the bacteria present in cockroaches that have evolved a burrowing lifestyle in parallel? Does host parallel evolution extend to parallel evolution in their symbionts? I work with whole Blattabacterium genomes to address these questions, investigating characteristics such as gene inventories to see how these bacteria have responded to their hosts moving underground. 

Adapted from Lo et al. (2007).

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