University of California Publications in Zoology Volume 17-24

University of California Publications in Zoology Volume 17-24

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This historic book may have numerous typos and missing text. Purchasers can usually download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1916 edition. Excerpt: ... in the Stikine region, it will be seen that not only are comparable ecologic niches on either side of the mountains usually filled by different species rather than subspecies, but that frequently the species are not especially closely related. Furthermore, among the few cases where two subspecies of a species do occur abundantly on either side of the mountains, there is hardly an instance where we were able to trace intergradation along the connecting valley of the Stikine. In some few cases where the birds were abundant enough for us to ascertain the fact, it was evident that certain subspecies, at this particular point, met as distinct species. All this argues for invasion from the southward, 011 either side of the Coast Range, of bird species and subspecies that met at a much later period along such channels as the Stikine Valley. The intrusion of a range of high mountains was productive of diverse climatic conditions in the two regions. This, in turn, resulted in differences in the reestablished plant and animal life to a far greater extent than would follow from the mere presence of a physical barrier such as a mountain mass. Differences of temperature and of humidity arose, so that at the present time the two areas, east and west of the Coast Range, respectively, form strongly contrasted faunal areas (dependent upon relative humidity), and they are somewhat different zonally (dependent upon temperatures). At a considerably later period than that at which the regions on either side of the mountains became habitable, conditions in certain of the river valleys traversing the barrier (as the Stikine) became such as to permit the existence of animal and plant life, and various species extended their ranges up or down such channels more

Product details

  • Paperback | 242 pages
  • 189 x 246 x 13mm | 440g
  • United States
  • English
  • black & white illustrations
  • 1236874056
  • 9781236874054