Nice YP CB1. A look at YP from several locations shows a good bit of local variation. As you know (for others who may not) all fish species that I know of exhibit local adaptation which may be visual (how the fish looks) or it may not be visual but rather be any of a hundred other functions. Over very long periods of time in seperate populations the local adaptation can become genetic . It is call Phenotypic plasticity which is the ability of an organism to change its phenotype in response to changes in the environment. Such plasticity in some cases expresses as several highly morphologically distinct results; in other cases, a continuous norm of reaction describes the functional interrelationship of a range of environments to a range of phenotypes (see Wiki ). Common examples are seen in Fla LMB and CNBG vs regular BG and LMB. In some instances new species are formed. In many other instances they go in to the ash bend of extinction.
It is my contention that Phenotypic plasticity can be found in human populations as well, case in point (not to come off sounding like Foxworthy but..) the tendancy of people that live in southern latitudes to chop up and shorten words and sentences ie, The daysr getnlonger! vs Springtime has brought about extended photoperiods. Because of hundreds of years coping with the heat our speech patterns have evolved in a way that uses the minimum number of calories while still communicating....if not for the advent of air conditioning we probably would have been reduced to a series of short grunts and facial gestures by now!
