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ALLOZYME VARIATION WITHIN AND AMONG MATURE POPULATIONS OF SPECKLED ALDER (ALNUS RUGOSA) AND RELATIONSHIPS WITH GREEN ALDER (A. CRISPA)
Author(s) -
Bousquet Jean,
Cheliak William M.,
Lalonde Maurice
Publication year - 1988
Publication title -
american journal of botany
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.218
H-Index - 151
eISSN - 1537-2197
pISSN - 0002-9122
DOI - 10.1002/j.1537-2197.1988.tb11245.x
Subject(s) - biology , alder , interspecific competition , population , reproductive isolation , gene flow , panmixia , genetic variation , zoology , evolutionary biology , botany , genetics , gene , demography , sociology
Vegetative tissues from 14 sexually mature populations of speckled alder ( Alnus rugosa (Du Roi) Sprengel) in Québec have been analyzed for electrophoretically demonstrable variation in 9 enzymes encoding a total of 15 loci. Speckled alder demonstrated a diploid‐like expression for all polymorphic loci investigated. Populations were in Hardy‐Weinberg equilibrium for the 9 polymorphic loci observed. The total expected heterozygosity was 0.173. Analysis of fixation indices indicated a slight deficiency of heterozygotes, relative to panmictic expectations. This was likely due to weak population differentiation, which did not follow any particular geographical trend. Qualitative estimates of interpopulation rates of gene flow were high, and in good agreement with the small pair‐wise population genetic distances and among‐population fixation index. Levels of genetic diversity and partition of this diversity were similar to previous observations obtained with the sympatric species A. crispa (Ait.) Pursh. However, no phenomena of interspecific hybridization were noted. The average genetic distance between these two alder species was large, with a value of 0.4, emphasizing the different ecological niches colonized by each of the two species. The estimate of divergence time between these two taxa was two million years. It is in agreement with the hypothesis of repetitive spatial isolation of each species in ice‐free refugia during the Pleistocene, thus promoting their reproductive isolation. The interspecific divergence noted at the enzyme level allowed for the easy electrophoretic identification of each taxon.