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

Introduction

Issues

1. What is the reproductive and genetic status of declining native pitch pine, Pinus rigida Mill., in Canada?
2. Are native populations suitable seed sources for species restoration and range expansion?
3. 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

Conclusions

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.

Reference

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.