Climate warming and pitch pine
Genetic status and northward movement of a rare southern component of Canada's forest
Alex Mossler¹, Om Rajora², and John Major¹
¹Canadian Forest Service
²Biology Department, Dalhousie University
- What is the reproductive and genetic status of declining native pitch pine, Pinus rigida Mill., in Canada?
- Are native populations suitable seed sources for species restoration and range expansion?
- What are the climatic and environmental limitations to northward expansion of pitch pine in eastern Canada?
Objectives: Characterize the reproductive & genetic status of native pitch pine & assess its growth performance in Atlantic Canada.
Material and methods
- Collected seeds from 17 natural stands in disjunct Canadian population of pitch pine for analysis of reproductive fitness (seed production) and genetic diversity at 32 allozyme gene loci.
- Measured tree size (height, stem diameter), age & distances of sampled trees to their five nearest neighboring trees (a surrogate for tree stand density).
- Quantified seed yields and seed quality
- Established genetic field tests in Atlantic Canada
Results and discussion
- Seed yields, seed quality and reproductive efficiency were comparable to other eastern conifers and to pitch pine at the center of the geographic in the U.S.A.
- Most variations in reproductive traits attributable to significant differences among trees within stands (19-30%), and among stands within population (26-33%) due to increased inbreeding and effects of inbreeding depression on fitness traits.
- Genetic diversity at 32 allozyme gene loci was high relative to other widely disprersed conifers and to pitch pine at the center of geographic range in the U.S.A.
- Genetic drift for cone serotiny and chlorophyll deficiencies observed in some stands
Cones of pitch pine
The genetic and reproductive status of Canada's extant pitch pine populations suggest that:
- extant populations may be a remnant of a wider, past distribution during warmer climates of the present interglacial period, rather than an advancing population expanding its range northward,
- native pitch pine populations are suitable as genetic sources for species restoration in Canada,
- seed production is comparable in quantity and quality to trees at the centre of the geographic range, and
- no climatic limitations apparent 8 years after introduction to Atlantic Canada.
Dry, infertile, rocky sites typical of natural pitch pine populations.
Mosseler, A.; Rajora, O.P.; Major, J.E.; Kim, K.-H. 2004. Reproductive and genetic characteristics of rare, disjunct pitch pine populations at northern limits of its range in Canada. Conservation Genetics 5:571-583.