''Hainanecio'' ( zh, s=海南菊属) is a

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

of flowering perennial herb endemic to

Hainan Island Hainan is an island province and the southernmost province of China. It consists of the eponymous Hainan Island and various smaller islands in the South China Sea under the province's administration. The name literally means "South of the Sea ...

China China, officially the People's Republic of China (PRC), is a country in East Asia. With population of China, a population exceeding 1.4 billion, it is the list of countries by population (United Nations), second-most populous country after ...

. A single species, ''Hainanecio hainanensis'', has been described from three populations on Hainan Island. It grows in shade in dense, broadleaved evergreen forests at 900–1200 m above sea level. It flowers from July to August and fruits in September to November. The sole species was first described as ''Senecio hainanensis'' by C. C. Chang & Y. C. Tseng (1974) before being transferred to '' Sinosenecio'' by C. Jeffrey & Y. L. Chen (1984). It was believed to be the southernmost-occurring species of ''Sinosenecio'' before being reclassified in 2011 by Y. Liu & Q. E. Yang as its own genus and species. Molecular phylogenetic analysis places ''H. hainanensis'' as an isolated member of the subtribe Senecioninae, being only distantly related to ''Sinosenecio'' species with basic chromosome number 30 or '' Tephroseris'' species with basic chromosome number 24. ''Hainanecio'' chromosomes are significantly smaller (0.8–1.8 μm) than those typical of ''Sinosenecio'' (1.2–4.0 μm). ''Hainanecio hainanensis'' may have 1 to several stems, with a stout rhizome up to 10 mm in diameter. The plant has several radical petiolate leaves of ovate to obovate shape with pinnate veining. The single radiate capitulum is white and composed of elliptic-oblong ray florets and many disc florets. The plant has truncate style arms, polarized and radial endothecial cell wall thickenings, and a cylindrical filament collar. It differs notably from ''Sinosenecio'' in its anthers that are rounded at the base and have ovoid and bubble-like anther apical appendages with enlarged abaxial cells. The plant lacks a pappus and has an obovoid, glabrous achene. Its

pollen Pollen is a powdery substance produced by most types of flowers of seed plants for the purpose of sexual reproduction. It consists of pollen grains (highly reduced Gametophyte#Heterospory, microgametophytes), which produce male gametes (sperm ...

grains have a coarse tectum layer and are helianthoid and triporate rather than senecioid and tricolporate as seen in ''Sinosenecio''. Like the subtribe Tussilagininae, it has polar and radial endothecial cell wall thickenings, cylindric antheropodia, and a basic chromosome number of 29.

References

Flora of China Monotypic Asteraceae genera Senecioneae {{Senecioneae-stub