THE EVOLUTION OF CONVERGENCE
An understudied albeit common case of adaptation is what is vaguely known under the term “convergence”. Convergent evolution is loosely defined as pertaining to organisms that independently acquire similar characteristics while evolving in similar ecosystems. Although this seems very straight forward, the idea that convergence produces the same functional kinds across species is often a philosophical oversimplification making its extrapolation to complex systems very tenuous. Additionally, the paradigm of “repeated similarity across unrelated groups” seemingly challenges the neo-darwinistic idea of absolute randomness of evolution and subsequently has been hijacked by creationists for their purposes. Thus, it not only makes for an interesting, but necessary philosophical discussion, which should be backed by empirical data.
To be able to get at this interesting phenomenon of evolution I am developing a new theoretical and experimental framework for studying convergence comparatively and systematically by long term interdisciplinary research on two ectoparasitic groups - the Siphonaptera (fleas) and the bat flies (Streblidae and Nycteribiidae). They are interesting to me because they represent independent (phylogenetically not closely related) experiments of evolution that, arising from non-parasitic ancestors, converge upon similar adaptations. Both groups rapidly radiated into a similar ecological niche (animal fur), and are sometimes even overlapping in host species preference. Their adaptations involve several levels of prominent organismal features and (supposedly) major underlying gene pathways, like the reduction, loss or gain of limbs, wings and eyes, the extreme modification of mouthparts for blood sucking, the change of the general body form, reproductive peculiarities (e.g. diapause in the larval stage, viviparity), or the expression of combs and spines.
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