Species ranges as a quintessential biologica…

A question that vexes me greatly is why scrub oak (or Gambel oak, Quercus gambelii) lives some places and not others. Why, for instance, does the species almost completely disappear north of Boulder, Colorado, but extend into the Sierra Madre Mountains of Wyoming west of the Continental Divide? Why does it carpet the lower slopes of the Wasatch, but barely occur at a similar elevation and latitude near Fort Collins?

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