Mitochondrial genome recombination in the zone of contact between two hybridizing conifers
Juan Pablo Jaramillo-Correa 1 and Jean Bousquet 1*
1 Centre de recherche en biologie forestière, Université Laval
* To whom correspondence should be addressed. E-mail: bousquet{at}rsvs.ulaval.ca.
Submitted on March 1, 2005
Revised on April 20, 2005
Accepted on 2 August 2005
 |
Abstract |
|---|
Variation in mitochondrial DNA was surveyed at four gene loci in and around the zone of contact between two naturally hybridizing conifers, black spruce (Picea mariana) and red spruce (P. rubens) in northeastern North America. Most of the mtDNA diversity of these species was found in populations next to or into the zone of contact, where some individuals bore rare mitotypes intermediate between the common mitotypes observed in the allopatric areas of each species. Sequence analysis and tests for mtDNA recombination point to this phenomenon, rather than recurrent mutation, as the most tenable hypothesis for the origin of these rare mitotypes. From the ten mitotypes observed, at least four would be the product of recombination between four of the five putative ancestral mitotypes. Tests for cytonuclear disequilibrium and geographical structure of the putative recombinant mitotypes suggest that mtDNA recombination is not frequent and relatively recent on the geological time scale. MtDNA recombination would have been promoted by transient heteroplasmy due to leakage of paternal mtDNA since the Holocene secondary contact between the two species.
Key Words:
conifer, hybridization, mitochondrial DNA, mitochondrial recombination, spruce
