New species can become isolated from the ancestral species with respect to reproduction even if they occur in the same area- in the example of these fancy fish, this happened in three different stages!
Hey guys, whats down this way?
Habitat-specific selectionLake Malawi =sandy habitat at bottom of lake, rocky habitat on sides. Initially fish lived in same habitat but later filled these two empty niches. Beneficial mutations were selected in each and cichlids in each habitat developed separately, surviving to pass on favourable traits for their habitat.
Isn't that cousin Jerry?
We don't swim out there okay? There's some weird looking fish amongst that sand
Food-specific selectionInitially there were few fish in the lake (little interspecific competition). As populations grew, so did competition. The lake had a large number of empty feeding niches. Different fish began utilising specific food sources, filling various empty niches and developing separately.
Can we have dead skin and fish parasites for dinner?
You must eat all you plankton son!
I love to eat rock algae!
Sexual-specific selectionBright colours and patterns in the males were a reproductive strategy. Random mutations gave rise to a variety of new colours and patterns. This proved advantageous as females reacted positively. New alleles for the new colours were established in the population through successful reproduction.
Wow, look at those guys...
Cichlidae fish have evolved into more than 500 species today. The rapid speciation over a very short period illustrates sympatric speciation, where new species originate in the same geographical area as ancestral species.VERY COOL !