Interspecific hybridization between Betula cordifolia and B. populifolia at Valcartier, Quebec

Abstract

A cytological and morphological study using hybrid indices, pictorialized scatter diagrams, and polygonal graphs has been carried out on a collection of Betula cordifolia Regel, B. populijolia Marsh., and some hybrids of these two species × B. caerulea Blanch. (B. caerulea Blanch, and B. caerulea-grandis Blanch.). A somatic chromosome number of 28 was determined for plants of all accession numbers of these taxa. Measurements of morphological characters were also made on plants of B. papyrifera Marsh. Hybrid index values, a pictorialized scatter diagram, and polygons showed that plants of B. caerulea and B. caerulea-grandis were hybrids and (or) introgressants between B. cordifolia and B. populifolia, confirming the study by Brittain and Grant on the Grand Manan Island population in which the name × B. caerulea Blanchard was given to all individuals resulting from hybridization or backcrosses between these two taxa. Significant interlocality (Valcartier and Grand Manan Island) differences were noted for measurements of some characters: for B. papyrifera, the number of pairs of lateral veins in the leaf and guard cell length; for B. cordifolia, achene length, pairs of lateral veins in leaf, and guard cell length; for × B. caerulea, bract length and pairs of lateral veins in leaf; for B. populifolia, style length.