Planting Natives: Implications for genetic pollution

Deborah L. RogersDirector of Conservation ScienceCenter for Natural Lands Managementand Conservation GeneticistGenetic Resources Conservation ProgramUniversity of California

CNPS Conservation ConferenceSeptember 8, 2007Santa Cruz, CA

CNLM PreserveLake County, CA

Planting Natives: Implications for genetic pollution

andClosing the gap between ‘landscaping’ and

‘genetic restoration’

Photo: D.L. Rogers

Presentation Outline

1. Genetic Contamination: what is it?2. Why it is difficult to develop appropriate

guidelines for GC3. Case studies of potential GC4. Approaches and priorities for managing GC5. Emerging research6. Resources

CNLM Coachella Valley PreservePhoto: D.L. Rogers

1. Genetic Contamination: What is it?

• Introduction of germplasm to a native population that can, through hybridization, eventually undermine the local adaptations and/or evolutionary potential.

• Opposite of genetic restoration.

• Includes:

i. ‘Unnatural’ hybridizations, including inter-and intra-specific.

ii. Genetic swamping, dilution, or erosion of native genetic diversity.

iii. Outcrossing depression, or undermining local adaptations.

Mechanisms of Outbreeding Depression

• Different chromosome structures or numbers (ploidy)

• Environmental dependent: loss of local adaptation in hybrids (only exhibits in some enviroments; GxE)

• Enviromentally independent: disruption of favorable interactions among loci (coadaptation) in F1 or later generations

Can involve one or more mechanisms simultaneously

Presentation Outline

1. Genetic Contamination: what is it?

2. Why it is difficult to develop appropriate guidelines for GC

3. Case studies of potential GC

4. Approaches and priorities for managing GC

5. Emerging research6. Resources

Photo: D.L. Rogers

2. Why is it so difficult … Plants are complicated!Trait Plants Animals

Sources of DNA Nucleus, chloroplasts, mitochondria

Nucleus, mitochondria

Genome size Redwood31,600 Mb

Human3,000 Mb

Ploidy Often > diploid Typically diploidMode of reproduction

Varied Typically sexual

Transmission genetics

Varied Biparental, maternal

Hybridization More common Less commonRestoration authority

Less restricted More restricted

Restoration options

More: spatial structure, banks, propagules

Fewer©D.L. RogersGenetic Resources Conservation ProgramUniversity of California

2. Why is it so difficult to develop appropriate guidelines to prevent or reduce the frequency of genetic contamination?

i. Rarely sufficient informationii. Genetic information is often based on neutral

genetic markersiii. Context dependentiv. Different spatial scales of adaptation for different

traitsv. Adaptation to past environments: is ‘locally adapted’

a sufficient criterion in the face of rapid environmental change?

vi. Difficulty of determining ‘adaptive genetic variation’ for threatened/endangered species

CNLM Rancho Guadalupe Dunes Preserve, Guadalupe, CA

Relationship between molecular and genetically based phenotypic variation

between molecular andphenotypic variation

Reed and Frankham 2001

Defining genetic units

CBALocation

Lineages

Environment

Adaptations

3. Case studies: potential genetic contamination

(from genetic restoration projects)

Case Study #1:Sequoia sempervirens

• Muir Woods National Monument (NPS)

• The Muir Woods coast redwood (Sequoiasempervirens) stand is one of the most southern old-growth redwood stands

• Unknown relationship to range-wide genetic variation (might be distinct)

Slide provided by S.Fritzke, NPS

• Privately grown seedlings (unknown origin) were planted as ‘memorial trees’ in the 1960s; Seedlings of unknown origin were planted by concessionaire

• Park policies changed and trees were never removed

• Trees now of reproductive age

• Removal must be strongly justified because of public pressure to ‘conserve’ allredwoods

S. Fritze

Issue:

Potential genetic contamination of native stand of coast redwoodby nonlocal, possibly non-adapted planted trees.

Recommendation:

Depending on number of planted trees, probable origin (any informationfrom records?), and known spatial distribution of genetic diversity inthis species, may not be a significant problem. Any genetic study wouldrequire reference samples from the rest of the redwood range and may not give conclusive results. Monitor. Could remove new seedlings or sprouts to minimize contribution to the gene pool.

Case study #2: Camissonia cheiranthifolia

• Camissonia cheiranthifolia in GGNRA

• Two distinct subspecies in California

• The non-local subspecies – C.c. suffruticosa –accidentally introduced in 1982

• Cross-breeding with native subspecies – C.c.cheiranthifolia – is evident

S. Fritzke 2005

Issues:

• Cross-breeding with native subspecies – C.c. cheiranthifolia – is evident

• Hybrids are spreading, and are difficult to identify

• Unknown threat to local subspecies and dune restoration efforts

• ‘Volunteer fatigue’

S. Fritzke 2005

Recommendation

Continue efforts, vigorously, to remove non-native subspecies.

Remove hybrids if in doubt.

Assume maladaptation of non-native subspecies in absence of information.

Provide education for volunteers, staff.

Case study #3: genetic erosion

Eelgrass (Zostera marina), a species ofseagrass, plays an important role in its ecosystem by stabilizing sediment, regenerating nutrients, and enhancing the survival of invertebrates in shallow coastal waters. Using a field survey, we determined the genotypes of eelgrass (Zostera marina) in particular highintertidal sites in Sacramento Landing and Marshall Beach, both located in Tomales Bay, California. Previous research indicates that eelgrass areas survived in disturbances and flourished in normal conditions better when they had more genetic diversity.

M. Parsian, A.R. Hughes, J.J. Stachowicz, K.Doo, and J. Moore (UC Davis)

Also: Williams and Davis, 1996, 2001

Case study #4

Wolf‘s evening primrose (Oenothera wolfii)

• Threatened, Oregon• Some genetic evidence of

hybridization with O. Glazioviana, a garden escape (Paper in press)

Case study #5: California poppy (Eschscholzia californica)

• Highly variable species (in flower size and color, seed dormancy,adaptation to soil type, etc.)

• North coastal populations from moist sites are obligate perennialsand have no seed dormancy

• Further inland and in southern California, populations from dryhabitats are usually obligate annuals and have high seed dormancy

• Genetic contamination is likely, given wide artificial distribution ofcommercial lines for landscaping purposes

Case study #6:

Monterey pine (Pinus radiata)

D.L. Rogers

4. Approaches and Priorities: When do ‘genetically appropriate plants’ make a difference?

Landscaping project is:

i. Large

ii. Close to native populations

iii. Sexually compatible with native populations

iv. Wind-pollinated

v. Limited genetic diversity or clonal

vi. From distant or unknown source population

Indicators of Genetic Contamination Risk

Priorities: more vulnerable populations?

Areas or species with more genetic structure

• Heterogeneous habitat• Isolated populations• Low gene flow (e.g., gravity-

dispersed seed, insect pollinated)

• Polyploid within species

• Ecotypes

ApproachesStructure guidelines by:

1. Taxonomic group (genera, life form, etc.

2. Proximity to native populations (e.g., urban, suburban, rural)

3. Context – risk to native pops

The Forest Service is a leader in developing guidelines for the responsible movement of genetic material for commercial forest tree species … but seed zones and seed transfer rules for ALL species may not be a practical approach to conserving genetic integrity.

Example of seed-specific seed zones for Ponderosa pine (var. scopulorum) in FS regions 1 and 2. This map shows seed zones for Montana and northern Wyoming. Within each of the six zones, the maximum movement allowed among elevations is 700 ft. if collected below 4,000 ft. and 1,000 ft. if collected above. Adapted from map provided by M.F. Mahalovich.

5. Emerging Research

Kreyenhagen Hills Conservation Bank

1. Importance of maintaining genetic diversity2. Connecting the ‘great divide’ between neutral and

adaptive genetic diversity studies

Species with considerable local genetic structure as compared with rangewide structure

Species Rangewide or regional

Local

Clarkia springvillensis

McCue et al. 1996

McCue et al. 1996

Pinus albicaulis Jorgenson et al. 1997

Rogers et al. 1999

Pinus ponderosa Mitton et al. 1977, 1980

Linhart et al. 1981

Sequoia sempervirens

Anekonda et. al 1994

Rogers 2000, Westfall and Rogers 2004

Avoiding cascading effects throughout the ecological community

“Conserving genetic diversity is more than a species issue … it is an important community issue … nearly 60% of arthropod diversity could be accounted for by genetic diversity in cottonwood stands … MVP concept may be inadequate for describing the genetic diversity needed in a producer to maintain species diversity in the dependent community … conserving genetic diversity in dominant plant species may be just as important as conserving genetic diversity in rare and endangered species.”

Whitham et al. 2003, Wimp et al. 2004.

(Photo from G. Allan)

The Challenge of Providing Genetic Information: the ‘Great Divide’

Quantitative genetics• Traits that have a

continuous distribution of values or phenotypes

• Influenced by several or many genes

• Experimental design and analysis separates ‘environmental’ effects from ‘genetic’ effects

• May reflect adaptive genetic variation

Molecular/allozyme• Traits expressed as

‘presence/absence’ or different alleles

• Measured in allele frequencies and distributions

• Single-locus (typically)• Typically reflect neutral

genetic variation

Linking phenotype with genotype

• Phenotypic traits

• Allozymes

• (DNA) Fragment-based methods

• (DNA) Sequence-based methods

Candidate genes, SNPs

Sequence-based methods• Whole genome projects still few• ESTs (Expressed Sequence Tags) more feasible and

less expensive; resequencing reveals genetic variation in expressed genes

• Many projects (species) of gene resequencing (e.g., from genes identified in model organisms)

• Screen for diversity within gene sequences (SNPs—Single Nucleotide Polymorphisms)

• Allows direct diversity comparisons within and among species because orthology of genes can be determined

• Increasingly high-throughput (many genes, many individuals) and affordable

• Can link ‘candidate genes’ with fast molecular techniques

Presentation Outline

1. Genetic Contamination: what is it?2. Why it is difficult to develop appropriate guidelines

for GC3. Case studies of potential GC4. Approaches and priorities for managing GC5. Emerging research6. Resources: see publications and list of resources at:

www.grcp.ucdavis.edu

Photo: Peter Knapp