Genetic Diversity: A Primer

Most people recognize the first level of species diversity. Southcentral Ontario has a rich diversity of species, over 100 tree species—each with a particular function in our landscape, which is itself very diverse in terms of climate, landforms and soils.

Within a single species there are additional levels of genetic diversity. Many of our species occur across a large geographic range and population diversity or adaptive variation has evolved. This means, for example, that red oak in eastern Ontario evolved to be particularly adapted to those conditions. While in southwestern Ontario, in a different set of conditions the red oak evolved differently. The degree to which this diversity exists varies by species, but generally speaking it is not well known for most of our native species. This population diversity is why seed source matters in reforestation programs. You want to ensure that the source of seed is adapted to the conditions of your planting site. The Ontario Ministry of Natural Resources has developed Tree Seed Zones for Ontario to help people understand what sources of seed and seedlings are adapted to their areas.

For more information about population diversity and Tree Seed Zones, visit Ontario's Natural Selections.

A second level is individual diversity—within a population of a single species. Trees in one stand can differ in many ways including growth rate or seed production or disease resistance. It's how one tree is slightly different than its neighbour, but still the same species. This is very important and accounts for most of the genetic variation within a species.

A third level of diversity is within an individual tree's genetic code. Maladapted genes can result from the normal process of random mutation, but they are often hidden, that is are in a recessive state. This is especially true for many of our tree species that are outcrossing - they breed largely through pollination from distant, unrelated trees, brought by wind or insects. But sometimes outcrossing is prevented or reduced - for example in white spruce stands in southern Ontario have become smaller and smaller and also more distant from each other. The likelihood that related individuals will breed increases and recessive genes can become expressed, often with negative results - no seed set, lack of chlorophyll or poor vigour of the seedlings.

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	FGCA > About genetic diversity > What is genetic diversity?
	Genetic Diversity: A Primer Most people recognize the first level of species diversity. Southcentral Ontario has a rich diversity of species, over 100 tree species—each with a particular function in our landscape, which is itself very diverse in terms of climate, landforms and soils. Within a single species there are additional levels of genetic diversity. Many of our species occur across a large geographic range and population diversity or adaptive variation has evolved. This means, for example, that red oak in eastern Ontario evolved to be particularly adapted to those conditions. While in southwestern Ontario, in a different set of conditions the red oak evolved differently. The degree to which this diversity exists varies by species, but generally speaking it is not well known for most of our native species. This population diversity is why seed source matters in reforestation programs. You want to ensure that the source of seed is adapted to the conditions of your planting site. The Ontario Ministry of Natural Resources has developed Tree Seed Zones for Ontario to help people understand what sources of seed and seedlings are adapted to their areas. For more information about population diversity and Tree Seed Zones, visit Ontario's Natural Selections. A second level is individual diversity—within a population of a single species. Trees in one stand can differ in many ways including growth rate or seed production or disease resistance. It's how one tree is slightly different than its neighbour, but still the same species. This is very important and accounts for most of the genetic variation within a species. A third level of diversity is within an individual tree's genetic code. Maladapted genes can result from the normal process of random mutation, but they are often hidden, that is are in a recessive state. This is especially true for many of our tree species that are outcrossing - they breed largely through pollination from distant, unrelated trees, brought by wind or insects. But sometimes outcrossing is prevented or reduced - for example in white spruce stands in southern Ontario have become smaller and smaller and also more distant from each other. The likelihood that related individuals will breed increases and recessive genes can become expressed, often with negative results - no seed set, lack of chlorophyll or poor vigour of the seedlings. Page < 1 2 >