In caves one repeatedly finds strikingly convergent patterns of evolution in diverse sets of organisms involving 'regressive' traits such as the loss of eyes and pigmentation. Ongoing debate centers around whether these regressive traits arise as the result of neutral evolutionary processes, or rather by natural selection of 'constructive' traits that arise at the expense of eyes and pigmentation. Recent research on cavefish points to the latter, suggesting that the 'constructive' trait vibrational attractive behavior and the reduction of eye size may share a common genetic basis.See research article http://www.biomedcentral.com/1741-7007/10/108.
Gunter, H., & Meyer, A. (2013, January 24). Trade-offs in cavefish sensory capacity. BMC Biology. https://doi.org/10.1186/1741-7007-11-5