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Abstract Detail

Systematics Section/ASPT

Baldwin, Bruce G. [1], Kyhos, Donald W. [2].

Revisiting evolutionary shifts in habitat, habit, and chromosomal structure and number in the pincushions (Chaenactis; Compositae–Chaenactideae).

A half century ago, D. W. Kyhos published cytogenetic and biosystematic evidence for dysploidization in annual pincushions (Chaenactis sect. Chaenactis) associated with an ecological shift from the Mediterranean-like California Floristic Province (CA-FP) to the southwestern deserts. In light of recent findings that Californian hotspots for especially young neoendemics are predominantly concentrated in the deserts and desert edges, Kyhos’s example in Chaenactis warrants more attention in considering origins of desert flora, in addition to considering the importance of chromosome evolution at the homoploid level. Nuclear rDNA (nrDNA) and chloroplast DNA (cpDNA) trees based on sampling of populations within and across the ~18 widely recognized species of Chaenactis reinforce Kyhos’s hypothesis and his subsequent unpublished cytogenetic evidence for the evolution of more extensive diversity of desert lineages with derived (2n = 5II) dysploid conditions. Both in the cpDNA and nrDNA trees, the desert-dwelling C. fremontii, C. stevioides, and other, undescribed 2n = 5II lineages nest within a grade of lineages corresponding primarily to the endemic CA-FP (2n = 6II) C. glabriuscula complex. The closely related C. xantiana (2n = 7II) evidently represents an example of ascending dysploidy in the same clade. Within Chaenactis, desert ecology is not unique to the 2n = 5II lineages, which are often confused with distant (2n = 8II) relatives that represent an independent occupancy of the deserts, in Chaenactis sect. Acarphaea (e.g., C. carphoclinia). Contrary to ideas predating Kyhos’s work about ecological evolution in Chaenactis, the molecular phylogenetic results indicate that Chaenactis was ancestrally annual (x = 8) and originated in seasonally dry or xeric environments of southwestern North America, with probably a single origin of perenniality associated with colonization and subsequent diversification in higher montane habitats across western North America, in sect. Macrocarphus.

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1 - University Of California Berkeley, Jepson Herbarium & Department of Integrative Biology, 1001 Valley Life Sciences Building, MC 2465, Berkeley, CA, 94720-2465, USA
2 - University of California, Davis, Department of Plant Biology, Davis, CA, 95616, USA

chromosome rearrangements
cryptic diversity
ecological transitions
habital shifts
habitat shifts.

Presentation Type: Oral Paper:Papers for Sections
Session: 60
Location: Salon 2/The Shaw Conference Centre
Date: Wednesday, July 29th, 2015
Time: 10:30 AM
Number: 60010
Abstract ID:798
Candidate for Awards:None

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