Chromosome numbers in compositae, XVII: Senecioneae III

A brief review is offered of major chromosome number variations in the Senecioneae based on recent delimitations of the tribe. An additional 78 chromosome reports are provided, including 19 new reports for species, with confirmed or expanded base numbers for the genera Gynoxys (x = 40), Lasiocephalus (x = 20), Pentacalia (x = 20, ca. 50), and Jessea (x = ca. 50). The base number for the tribe is x = 10, which is found in various multiples. The Blennospermatinae are one of the most distinct groups with a base of x = 9, considered an aneuploid reduction from x = 10. A new subtribe, Abrotanellinae, is established for the southern South American and southwest Pacific genus Abrotanella, which also has x = 9 and has often been placed in the Blennospermatinae. Numbers based on x = 30 and aneuploid reductions are found in the Tussilagininae, in many Australian Senecio, and in the Macaronesian Pericallis of the Senecioninae. The origin of such numbers is discussed. An anomalous North American group of Senecio (Packera) has variable numbers mostly near n = 23. Most Western Hemisphere Senecioninae have numbers of n = 20 or multiples thereof, with higher numbers in many Andean groups. Numbers of n = 10 or lower are mostly restricted to the Eastern Hemisphere, and groups like Emilia have recently dispersed from that area. Occurrences of n = 5 in Emilia, n = 10 in some American and Australian Senecio, and n = 14-16 in some tussilaginoids are considered as reductions.