| speciation in reverse: morphological and genetic evidence of the collapse of a three-spined stickleback (gasterosteus aculeatus) species pair. | historically, six small lakes in southwestern british columbia each contained a sympatric species pair of three-spined sticklebacks (gasterosteus aculeatus). these pairs consisted of a 'benthic' and 'limnetic' species that had arisen postglacially and, in four of the lakes, independently. sympatric sticklebacks are considered biological species because they are morphologically, ecologically and genetically distinct and because they are strongly reproductively isolated from one another. the restr ... | 2006 | 16448405 |