 The divergence and speciation within bottlenose dolphins has been largely due to climate and environmental changes over history . According to research , the divisions within the genus correlate with periods of rapid climate change . For example , the changing temperatures could cause the coast landscape to change , niches to empty up , and opportunities for separation to appear . In the Northeast Atlantic , specifically , genetic evidence suggests that the bottlenose dolphins have differentiated into coastal and pelagic types . Divergence seems most likely due to a founding event where a large group separated . Following this event , the separate groups adapted accordingly and formed their own niche specializations and social structures . These differences caused the two groups to diverge and to remain separated . 
