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Abstract Detail

Genetics Section

Harrington, Judy [1], Reid, Scott [1], Black, William [2], Brick, Mark [1].

Was Rydberg Right? Evidence for Distichlis stricta as a species distinct from D. spicata.

The North American grass species Distichlis stricta (Torrey) Rydberg, commonly called inland or desert saltgrass, was proposed in 1905 as a separate species from D. spicata (L.) Greene. D. stricta has not been recognized as a separate species in recent taxonomic classifications because its morphological traits overlap those of D. spicata. However, Bell found molecular evidence that D. spicata is polyphyletic. Was Rydberg right? The published chromosome number for D. spicata is 40. A recently-discovered 38-chromosome race of saltgrass is distributed over an area similar to that described by Rydberg for D. stricta. To determine whether the two chromosome races differ substantially, we analyzed chloroplast and nuclear DNA in 197 plants collected from twelve sites in the western United States. Five sites had the 40-chromosome race and seven sites had the 38-chromosome race. Noncoding intergenic segments of chloroplast DNA were amplified and cut with restriction enzymes. Plants with 40 chromosomes contained a single chloroplast haplotype, while plants with 38 chromosomes contained multiple chloroplast haplotypes distinct from the 40-chromosome haplotype. Amplification of nuclear simple sequence repeat segments revealed several alleles that were common in one chromosome race but rare in the other. Amplification with a randomly amplified polymorphic DNA (RAPD) primer resulted in different banding patterns between the two races. A published RAPD marker for females in this dioecious grass reliably identified females in 40-chromosome populations but not in 38-chromosome populations. In addition to the molecular traits that differentiate between the two races, flowering times may differ. In a common garden experiment, 38-chromosome plants began flowering one month earlier than 40-chromosome plants. These results suggest that the two chromosome races are geographically and genetically distinct with little gene flow between them. We propose that the 38-chromosome race represents Rydberg’s D. stricta and the 40-chromosome race represents D. spicata.

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1 - Colorado State University, Soil and Crop Sciences, 1170 Campus Delivery, Fort Collins, Colorado, 80523, USA
2 - Colorado State University, Microbiology, Immunology and Pathology, 1682 Campus Delivery, Fort Collins, Colorado, 80523, USA

molecular phylogenetics.

Presentation Type: Poster:Posters for BSA Sections
Session: P2
Location: Event Tent/Cliff Lodge
Date: Tuesday, July 28th, 2009
Time: 5:30 PM
Number: P2GN004
Abstract ID:159