Abstract Detail

Systematics

Allen, Geraldine [1], Kaye, Thomas [2], Kierstead, Julie [3].

Untangling taxonomic complexities and the conservation of rare asters (Eucephalus, Asteraceae).

Taxonomically difficult species complexes present a challenge for the delineation and conservation of rare taxa. A detailed understanding of genetic and phenotypic variation in these groups is required to identify the taxonomic units of concern for conservation management. The genus Eucephalus consists of 10 species in Cordilleran western North America, of which several are rare. Eucephalus is most diverse in the Klamath Mountains of southwestern Oregon and northern California, where five species occur. One of these (E. ledophyllus) has purple-rayed flower heads; the other four (E. breweri, E. glabratus, E. tomentellus and E. vialis) are rayless or nearly so. The wayside aster E. vialis is rare and of conservation concern in both Oregon and California. We investigated morphological and genetic characteristics of all five species in the Klamath region. Multivariate analyses of morphological data from 275 field-collected and herbarium specimens showed that none of the species are well separated morphologically; instead they form a continuous series from E. vialis to E. ledophyllus. Leaf size, leaf pubescence and phyllary shape are important differentiating characters. The purple-rayed E. ledophyllus is usually identifiable by ray number, but intergrades with few-rayed and rayless forms, especially E. tomentellus. Ray number is often highly variable within individuals, with rayless and rayed heads occurring on the same plant. We identified three distinct molecular groups based on sequencing of the ITS nrDNA region in 108 specimens, but these groups did not correspond closely with morphological differences. One ITS group characterized E. breweri, which is uncommon in the Klamath region. The other two ITS groups occurred in all remaining species, indicating little molecular differentiation. Commonly occurring ITS ribotypes in these sequence groups were shared across species. We examined geographic patterns in both morphological and molecular data. Three of the species in this study (E. breweri, E. ledophyllus and E. vialis) have broad regional distributions and are partly allopatric. The other two (E. glabratus and E. tomentellus) are localized in the Klamath region, where they co-occur with all of the other species. The ITS groups were not geographically distinct, although we observed some latitudinal variation in ribotype frequencies. Morphological extremes of this species complex are recognizable as distinct species; the intermediate species E. glabratus and E. tomentellus are poorly marked and separated by somewhat arbitrary boundaries. Our study illustrates the contradictions inherent in defining species boundaries in complex groups.

1 - University Of Victoria, Department Of Biology, PO Box 1700 Station CSC, Victoria, BC, V8W 2Y2, Canada
2 - Institute for Applied Ecology, 563 SW Jefferson Ave., Corvallis, OR, 97333-4602, USA
3 - USDA Forest Service, Shasta-Trinity National Forest, 3644 Avtech Parkway, Redding, CA, 96002

Keywords:
Asteraceae
Eucephalus
ITS
morphometrics
genetic diversity
rare plant conservation.

Presentation Type: Oral Paper
Session: SYS3, Systematics III: Asterids part 2
Location: Tucson G/Starr Pass
Date: Wednesday, July 31st, 2019
Time: 4:00 PM
Number: SYS3010
Abstract ID:548
Candidate for Awards:None