Population Genetic Structure of Asclepias Tuberosa in Northwest Iowa: A Comparison Within and Between Remnant Prairies and Commercially Available Seed

Isolated in scattered remnants, less than 0.1% of Iowa\u27s original tallgrass prairie remains. The small populations remaining are at risk for reduced genetic diversity, inbreeding depression, and outbreeding depression. In light of these concerns, we used microsatellite analysis to assess the genetic structure of butterfly milkweed (Asclepias tuberosa) populations on prairie remnants in northwest Iowa. We compared remnant populations with a restoration population at Dordt College in Sioux Center, Iowa, and with an Oklahoma seed source. Microsatellites identified for use in common milkweed (Asclepias syriaca) had sufficient polymorphism information content (PIC) across the butterfly milkweed (A. tuberosa) populations sampled (mean PIC = 0.624). The FIS values indicated a lack of inbreeding (mean FIS = −0.1455) even in the commercially expanded seed. The pairwise FST values showed a low degree of differentiation among the remnants (mean FST = 0.0453) but a moderate degree (mean FST = 0.105) of differentiation when comparing the remnants to the Dordt restoration or to seed from Oklahoma. Despite massive loss and fragmentation of the tallgrass prairie, our microsatellite analysis revealed no evidence of inbreeding in A. tuberosa. However, evidence of genetic differentiation suggests that effort should be made to preserve the diversity still present. Seed expansion efforts appear to have had minimal impact on overall genetic diversity, although the diversity in particular selectable traits may be reduced. The differences between the genetics of the propagated seed at the Dordt restoration and the Oklahoma seed when compared to native remnants support the usefulness of source-identified seed

Genetic Diversity of Asclepias Tuberosa in Iowa Prairies

Reduced population size can result in the loss of genetic diversity, which in turn can make organisms more susceptible to environmental challenges. In Iowa less than one percent of the original tallgrass prairie remains, isolated in a few remnant prairies. We are undertaking a long term project to assess the genetic variability in native prairie plants on remnant prairies in Northwest Iowa. We are testing six microsatellite sequences for butterfly milkweed (Asclepias tuberosa) from the Steele Prairie State Preserve, Broken Kettle Grasslands, a private prairie near Cherokee IA, a prairie restoration project on the Dordt College campus and populations from suppliers in Oklahoma and Pennsylvania. We hope to answer the following questions: A) Do nearby remnant prairies share alleles and have similar allelic diversity? B) Is there evidence for inbreeding in remnant populations? C) Is there evidence that plant populations found in local native prairies are genetically distinct from restored prairies and from those originating outside the state of Iowa? Preliminary results suggest that A) Essentially all of the alleles are found in at least 2 of the populations analyzed B) the degree of homozygosity is not higher than expected values and C) the four remnant prairie populations of butterfly milkweed that were tested show little genetic differentiation from each other but show moderate differentiation from commercial seed. The answers to these questions will help inform strategies for prairie conservation and restoration in Iowa and across the Midwest

Population Genetic Structure of \u3ci\u3eAsclepias Tuberosa\u3c/i\u3e in Northwest Iowa: A Comparison Within and Between Remnant Prairies and Commercially Available Seed

Isolated in scattered remnants, less than 0.1% of Iowa’s original tallgrass prairie remains. The small populations remaining are at risk for reduced genetic diversity, inbreeding depression, and outbreeding depression. In light of these concerns, we used microsatellite analysis to assess the genetic structure of butterfly milkweed (Asclepias tuberosa) populations on prairie remnants in northwest Iowa. We compared remnant populations with a restoration population at Dordt College in Sioux Center, Iowa, and with an Oklahoma seed source. Microsatellites identified for use in common milkweed (Asclepias syriaca) had sufficient polymorphism information content (PIC) across the butterfly milkweed (A. tuberosa) populations sampled (mean PIC ¼ 0.624). The FIS values indicated a lack of inbreeding (mean FIS ¼ 0.1455) even in the commercially expanded seed. The pairwise FST values showed a low degree of differentiation among the remnants (mean FST ¼ 0.0453) but a moderate degree (mean FST ¼ 0.105) of differentiation when comparing the remnants to the Dordt restoration or to seed from Oklahoma. Despite massive loss and fragmentation of the tallgrass prairie, our microsatellite analysis revealed no evidence of inbreeding in A. tuberosa. However, evidence of genetic differentiation suggests that effort should be made to preserve the diversity still present. Seed expansion efforts appear to have had minimal impact on overall genetic diversity, although the diversity in particular selectable traits may be reduced. The differences between the genetics of the propagated seed at the Dordt restoration and the Oklahoma seed when compared to native remnants support the usefulness of source-identified seed