Abstract Detail

Ecological Section

Giddens, Jonathan [1], Elisens, Wayne [2].

Ecogeographic Pattern of Bract and Cypselae Variation in Iva annua (Asteraceae: Heliantheae) and its Taxonomic Significance.

Inflorescent bract and cypsela dimensions were determined and analyzed from 148 herbarium specimens and individuals in 15 field populations throughout the geographic range of Iva annua to test hypotheses of infraspecific taxonomy and ecogeographic structuring. Zero to three infraspecific taxa have been proposed for Iva annua including vars. annua and caudata, and the extinct cultigen var. macrocarpa. Bract dimensions ranged threefold in length (L), fivefold in width (W), and threefold in W/L ratios among populations and specimens. Mature cypselae displayed a twofold range of variation in lengths and widths and exhibited a close positive association (r=0.88) between length and width. A post-hoc analysis of inflorescence bract W/L ratio data for populations was conducted by performing a one-way ANOVA comparing populations located within the Eastern Temperate Forest and Grassland ecoregions (EPA Level One). Populations organized into eco-regions were statistically significant (F= 212.3, p<0.001) with 67.8% of the variability explained by eco-region. Because high levels of variation in these characters were observed within individuals and within and among populations, taxonomic recognition of vars. annua and caudata remain problematic, are not based on consistent or unique characters, and is not recommended. The large cypselae described from archaeobotanical sites differ significantly from those from extant populations and accord with recognition of an extinct var. macrocarpa.

1 - University Of Oklahoma, Plant Biology, 770 Van Vleet Oval # 204, Norman, OK, 73019, USA
2 - University Of Oklahoma, Department Of Botany And Microbiology, 770 Van Vleet Oval, Norman, OK, 73019, USA, 405/325-6281

Keywords:
morphology
Asteraceae
Iva
Ecogeography
Heliantheae
taxonomy.

Presentation Type: Poster:Posters for Sections
Session: P
Location: Hall D/The Shaw Conference Centre
Date: Monday, July 27th, 2015
Time: 5:30 PM
Number: PEC006
Abstract ID:1185
Candidate for Awards:Ecological Section Best Graduate Student Poster