Clines revisited: The timing of pupping in the harbour seal (Phoca vitulina) |
| |
Authors: | J L Temte M A Bigg ‡ and Ø Wiig |
| |
Institution: | Department of Zoology, 421 Birge Hall, University of Wisconsin, Madison, Wisconsin 53706, USA;Department of Fisheries and Oceans, Pacific Biological Station, Nanaimo, British Columbia V9R 5K6, Canada;Norwegian Polar Research Institute, PO Box 158, N-1330 Oslo Lufthavn, Norway;‡Deceased autumn 1990 |
| |
Abstract: | The regional variation in the pupping season of the harbour seal ( Phoca vitulina ) was reviewed using the birth periods reported for 65 colony sites distributed over a range from 30.4 to 78.5 North latitude. The birth timing of P. v. vitulina was not related to latitude, but birthing in P. v. concolor along eastern North America exhibited a latitudinal cline. The timing of birth in P. v. richardsi varied in three distinct patterns: (1) a significant unidirectional latitudinal cline extending between Baja California and the west coast of Washington; (2) a cluster comprised of Puget Sound, Washington and Vancouver Island, British Columbia colonies in which birthing occurred an average of 65 days later than on the Washington coast; and (3) a cluster from northern British Columbia and Alaska which did not demonstrate a latitudinal cline. Insufficient data were available for the analysis of P. v. mellonae or P. v. stejnegeri . We found great regional variation in the timing of birth among all colonies, with mean birth dates occurring as early as 15 March and as late as 3 September. Little variation existed north of 50 . To the south of 50 , however, most of the variation could be attributed to correlation with latitude or to affiliation with the Puget Sound, Washington-Vancouver Island, British Columbia geographic area. Clinal variation in pupping could result from: (1) geographic variations in a selective factor with perhaps gene exchange between contiguous populations playing a role in smoothing the variation; or (2) for populations between Mexico and the west coast of Washington, regional variation in a non-selective environmental variable, such as photoperiod. |
| |
Keywords: | |
|
|