1. Some closely related species of snails cannot mate because their shells spiral in opposite directions, making it impossible for their reproductive organs to be aligned. The type of evidence is mechanical incompatibility. 2. Although some closely related (but separate) species of salamander can mate with each other to produce offspring, the offspring fail to develop normally and cannot reproduce. The type of evidence is gametic incompatibility. 3. In North America, one species of garter snake lives primarily in the water, while another species lives primarily on land. Therefore, they rarely meet and mate. The type of evidence is