Maternal effects predominate over local adaptation in seedling emergence of Echinacea angustifolia

Amy B. Dykstra, Ruth G. ShawUniversity of Minnesota

Acknowledgements:• Brad Dykstra• Stuart Wagenius• Team Echinacea• Plant Biological Sciences graduate program,

University of Minnesota• National Science Foundation• Minnesota Center for Community Genetics• Chicago Botanic Garden• Grand River National Grassland• The Nature Conservancy• Minnesota Department of Natural Resources• South Dakota Department of Natural Resources

IntroductionConversion of land to agricultural use has resulted in the loss of an estimated 82-99% of the North American tall grass prairie habitat (Samson and Knopf, 1994). Recently, interest in restorations of native habitat has increased. Restoration guidelines commonly recommend using local germplasm, to maximize local adaptation and reduce the likelihood of outbreeding depression. However, nearby populations in fragmented habitat may not contain sufficient genetic diversity for successful reintroductions (Broadhurst et al. 2008). The purpose of this study is to assess the degree of local adaptation in the emergence and survival of Echinacea angustifolia seedlings.

AbstractEchinacea angustifolia is a long-lived perennial native to the North American prairies. To detect local adaptation in E. angustifolia, I collected seeds from northwestern South Dakota, north-central South Dakota, and west-central Minnesota, and sowed the seeds from each source into prairie restorations located near each source population. Seedling emergence was highest for the western Minnesota and western South Dakota seeds and lowest for the central South Dakota population in all three sowing sites. These results are consistent with the common finding that maternal effects predominate in seedling germination or emergence. There is no evidence for local adaptation at this early stage in the life cycle of E. angustifolia. I will continue to monitor survival and growth of the seedlings, since local adaptation may be expressed at later stages.

ReferencesBroadhurst L. M., Lowe A., Coates D. J., Cunningham S. A.,

McDonald M., Vesk P. A. and Yates C. 2008. Seed supply for broadscale restoration: maximizing evolutionary potential. Evolutionary Applications 1: 587-597.

R Development Core Team. 2009. R: A language and environment for statistical computing. R Foundation for Statistical Computing, Vienna, Austria.

Samson F. and Knopf F. 1994. Prairie conservation in North America. BioScience. 44: 418-421.

Study species:Echinacea angustifolia(narrow-leaved purple coneflower)• Long-lived perennial• Single taproot• Reproduces only by seed• Rarely flowers before third year•May or may not flower each year• One or more inflorescences per season• Self-incompatible• Pollination by generalist insects• No specialized seed dispersal

Collection sites (Figure 1)• Grand River National Grassland

(northwestern SD)• Samuel H. Ordway, Jr. Memorial Preserve

(TNC) (north-central SD)• Staffanson Prairie (TNC) (west-central MN)

Seed collections: Sept. 2008• Collections along an east-west transect from

northwestern South Dakota to western Minnesota–Moisture gradient–Similar growing season–Consistent day-length• Capitula collected from 50 randomly selected

individuals at each site

Seed sowing: November 2008• Achenes from each individual were counted and

divided into 6 lots• Two seed lots from each individual were sown into

each of three experimental plots• Seed lots were assigned random locations in a grid• Precise sowing locations were marked with nails

(Figure 2)

nail

Figure 2. E. angustifolia achenes on the ground near a nail marking the precise sowing location.

achenes

Assessment of seedling emergence: May 2009• Each sowing location was exhaustively

searched• Seedlings were positively identified by

presence of cotyledons• Seedlings were marked with colored

toothpicks (Figure 3)

Figure 3. E. Angustifolia seedling, with 2 cotyledons and a true leaf, marked with a blue plastic toothpick.

Figure 1. Seed collection locations. Left, Grand River National Grassland, SD. Below, map of Echinacea angustifolia distribution with seed collection and sowing locations marked with yellow stars. Below right, Staffanson Prairie, MN.

Analysis• Generalized linear models (glm)

–Binomial response: number of seedlings per number of achenes sown

–Predictors: seed source, sowing site, block• Analysis of variance for model comparison• All analyses performed with R (R Development Core

Team 2009)

Results• Significant effect of seed source and sowing site• No significant seed source by sowing site interaction• Seedling emergence was highest for seeds collected

in western South Dakota and western Minnesota, and lowest for seeds collected in central South Dakota, at all three sowing sites (Figure 4)• Seedling emergence was highest in western

Minnesota, intermediate in central South Dakota and lowest in western South Dakota (Figure 4)

Figure 4. Seedling emergence of E. angustifolia in a reciprocal sowing experiment. GRNG=Grand River National Grassland; SHOrd=Samuel H. Ordway, Jr. Memorial Preserve; SPP=Staffanson Prairie; PL=Perch Lake WPA, north-central SD; WMAHL= Hegg Lake WMA, MN.

Conclusions•Maternal effects predominate over local adaptation• Local adaptation may manifest at later

developmental stages• Future directions: monitor survival for additional

seasons