TY - JOUR
T1 - Evolutionary history of the arid climate-adapted Helichrysum (Asteraceae: Gnaphalieae): Cape origin and association between annual life-history and low chromosome numbers
AU - Andrés-Sánchez, Santiago
AU - Verboom, G. Anthony
AU - Galbany-Casals, Mercè
AU - Bergh, Nicola G.
PY - 2019/9/1
Y1 - 2019/9/1
N2 - © 2018 Institute of Botany, Chinese Academy of Sciences The basal grade of the large, widely-distributed Helichrysum-Anaphalis-Pseudognaphalium (HAP) clade (Asteraceae, Gnaphalieae) comprises exclusively southern African taxa. These species possess unusual trait combinations relative to the remaining species (a high proportion of annuals, unusual capitulum arrangement, and low base chromosome numbers). A time-proportional Bayesian phylogenetic hypothesis is generated from nuclear ribosomal sequences from 110 accessions. Ancestral area, life history, and base chromosome number are reconstructed using maximum likelihood, and correlations between life-history and chromosome number are tested in a phylogenetic framework. The results show that the HAP clade probably originated and experienced initial diversification in the Greater Cape Floristic Region in the Early to Middle Miocene. The ancestor of the HAP clade is inferred to have been perennial with x = 7 base chromosome number. Several independent acquisitions of the annual life-history are inferred, accompanied by reductions to x = 4 and 5. A single reversal to perennial life history is associated with a subsequent change back to the state of x = 7. Origin and early diversification within the HAP clade follows the pattern of multi-area seeded radiations within southern Africa, with subsequent migrations to the rest of Africa and the Northern Hemisphere. Occupation of drier habitats with shorter growing seasons may select for the acquisition of a shorter life-cycle, and our results indicate a strong association between short life-cycle and reduced chromosome number.
AB - © 2018 Institute of Botany, Chinese Academy of Sciences The basal grade of the large, widely-distributed Helichrysum-Anaphalis-Pseudognaphalium (HAP) clade (Asteraceae, Gnaphalieae) comprises exclusively southern African taxa. These species possess unusual trait combinations relative to the remaining species (a high proportion of annuals, unusual capitulum arrangement, and low base chromosome numbers). A time-proportional Bayesian phylogenetic hypothesis is generated from nuclear ribosomal sequences from 110 accessions. Ancestral area, life history, and base chromosome number are reconstructed using maximum likelihood, and correlations between life-history and chromosome number are tested in a phylogenetic framework. The results show that the HAP clade probably originated and experienced initial diversification in the Greater Cape Floristic Region in the Early to Middle Miocene. The ancestor of the HAP clade is inferred to have been perennial with x = 7 base chromosome number. Several independent acquisitions of the annual life-history are inferred, accompanied by reductions to x = 4 and 5. A single reversal to perennial life history is associated with a subsequent change back to the state of x = 7. Origin and early diversification within the HAP clade follows the pattern of multi-area seeded radiations within southern Africa, with subsequent migrations to the rest of Africa and the Northern Hemisphere. Occupation of drier habitats with shorter growing seasons may select for the acquisition of a shorter life-cycle, and our results indicate a strong association between short life-cycle and reduced chromosome number.
KW - AUSTRALIAN GNAPHALIEAE
KW - COMPOSITAE
KW - EXTERNAL TRANSCRIBED SPACER
KW - FLORA
KW - GENOME SIZE VARIATION
KW - Helichrysum
KW - INFERENCE
KW - L.
KW - NUCLEAR-DNA CONTENT
KW - PHYLOGENETIC-RELATIONSHIPS
KW - POLYPLOIDY
KW - ancestral character state reconstruction
KW - chromosome evolution
KW - life form
KW - phylogeny
KW - southern Africa
UR - http://www.mendeley.com/research/evolutionary-history-arid-climateadapted-helichrysum-asteraceae-gnaphalieae-cape-origin-association
U2 - 10.1111/jse.12472
DO - 10.1111/jse.12472
M3 - Article
VL - 57
SP - 468
EP - 487
JO - Journal of Systematics and Evolution
JF - Journal of Systematics and Evolution
SN - 1674-4918
IS - 5
ER -