Article Abstract:
Larus glaucescens and Larus occidentalis go through a number of episodes of secondary contacts and separation, during which hybridization occurs but fails to swamp either species. Human-induced habitat alteration may be responsible for the genetic diversity in L. glaucescens. The populations of the L. glaucescens-occidentalis complex are sexually dimorphic, and the hybrid zone may be a possible barrier to gene flow. This zone is present from Juan de Fuca Strait, Washington, south to Coos Bay, Oregon. Hybrids have more genetic similarities with L. glaucescens.
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Article Abstract:
Information on the distribution of morphotypes, mate choice and reproductive performance in Glaucous-winged Gull and Western Gull were compared with sympatric members of the Larus Glaucescens-Occidentalis mate. Most backcrossing involves gulls that are close in phenotype to pure parentals. Selection-hybridization best described Larus Glaucescens-Occidentalis hybrid zone, wherein hybrids experience greater reproductive fitness.
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Article Abstract:
Research is presented concerning the use of 13 color characters to describe Dendroica nigrescens, Dendroica occidentalis, hybrid birds and recombinants. The hybridization of these warblers is discussed.
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