Major climatic and tectonic episodes can drive speciation; rising sea levels can close land bridges ... show that major events in the diversification of squirrels are timed with large-scale changes in ...

For example, reproductive isolation is weak in the early stages of speciation, but changes to strong or complete in later stages of speciation (Figure 2). One or more of the many types of ...

I often enjoy the more common side of nature, the nature in our own backyards or neighborhood park that we see every day – for example, the eastern gray squirrel (Sciurus carolinensis). It’s likely ...