• Genetic Considerations in Restoration Ecology

• Linhart, Y.B. 1995. Restoration, revegetation and the importance of genetic and evolutionary perspectives. Proceedings: Wildland Shrub and Arid Land Restoration Symposium. USDA Intermountain Research Station

• Linhart proposed very restrictive guidelines:

– Use nearby local native species

• Within 100 m for herbs

• Within 1 km for woody plants

• Precise local adaptations:

– “Plant genomes show very precise adaptations to local conditions. Introduction of non-local materials may lead to failure of revegetation projects and endanger long-term health of nearby populations.”

• Studies of genetic variability show:

– Geographic range accounts for largest variation

– Species with large ranges are more variable than endemics

– Breeding system:

• Outcrossers more variable

– Variability is within populations

• Inbreeders less variable

– Variability is among populations (populations differ)

• Genetic variability

– Primary factors affecting genetic variability:

• Breeding systems

• Selective pressure

– Natural selection, heterogeneity of environment

• Genetic drift

• Gene flow

• Some arguments against restrictive genetic guidelines

– Precise adaptations? Niche displacement

– “No organism is perfectly adapted; all fail to adapt to their environments in some ways and to differing degrees” Fisher, 1930

– Competitive advantage may be conferred on a less optimally adapted genotype because it has less competition where it finds the opportunity to flourish.

• Some arguments against restrictive genetic guidelines 2

– Genetic variation is variation between plants

• One plant does not have variation

• One seed has a different genetic makeup than another seed

– The place where a plant is most common may be the place that has the most poorly adapted genotypes.

– Precise adaptation may be occurring at the ends of a plant’s range

• Some arguments against restrictive genetic guidelines 3

– Plants can adapt to the environment genetically, or by plasticity

• Some species have high geographic variability (Douglas fir, loblolly pine)

• Some species do not (western red cedar, white pine)

• What is identified as geographic variation may actually be a response to an environmental gradient

– Which could occur over a 1000 km or 1 km.

• “Why do we care about genetics?”

• 12 factsheets from Genetic Resources Conservation Program, U.C. Davis

• Why is genetic diversity important?

– It may gauge a species ability to adapt to changing environment.

– Populations may be able to occupy different ecological niches.

• How can genetic information be valuable in natural resource management?

– For establishing taxa.

– To assess normal levels of diversity.

– To assess gene flow.

– To determine where to collect seeds.

– To understand how the ecology of a species has evolved (bottlenecks, dispersers).

– To track human-assisted plant movement.

• Why is genetic diversity dynamic?

– Migration

– Mutation

– Genetic drift

– Selection

• Are patterns of genetic diversity important?

– Broadly distributed pollen and seeds suggest little local genetic differentiation.

– Selfing, heavy seeds, quick germination suggest differences from one population to another.

– Strong selection pressures (climate) may result in locally differentiated populations.

• What are the genetic risks associated with a planting decision?

– Genetic consequences can be because of the amount and type of diversity introduced.

• Lower amount can lead to genetic erosion.

– Collect from adequate number of well-spaced donors.

• Wrong kind can lead to loss of local adaptations.

– Match site conditions.

• Can genetic diversity be influenced by nursery practices?

– Nursery plants are a sub-sample of natural diversity.

– Subsequent filtering (for size, speed of germination, etc.) further reduces sample.

– Supplying adequate water, moisture and light is essentially diversity-neutral.

• What is genetic erosion and how can it be managed?

– May occur quickly with a large population or habitat loss.

– May occur slowly

• Fragmentation

• Selective harvest

• Re-planting with material with narrow genetic range.

– Addressing genetic erosion

• Collect materials that represent the genetic diversity of the geographic area.

• Obtain geographic source information when buying nursery plants.

• Use caution when planting cultivars.

• Encourage nurseries that use practices that maximize genetic diversity.

• Is genetic management important in urban landscapes?

– Choosing appropriate geographical source insures that plants are well-adapted to planting site. (?)

– Also provides continuity with neighboring populations and bridges to disjunct populations.

– Habitat for native specialist animals (esp. insects).

M.L. Guinon. 1992. Seed and Plant Procurement Guidelines. U.S. Forest Service, Forest Nursery Associaton Proceedings. General Technical Report RM-221. USDA Forest Service, Rocky Mountain Forest and Range Experiment Station.

Four General Genetic Categories of Plants

Outcrossers
Genetically diverse, high gene flow

Inbreeders
Locations of donor plants should be well defined to match with receiving sites.

Endemics
High site specificity. Collect from site.

Threatened and endangered species
Many T&E species would benefit from increased gene flow.