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 spec ies, with confirmed or expanded base numbers for the genera Gynoxys (x = 40), Lasiocephalus (x = 20), Pentacalia (x = 20, ca. 50), and Jesse a (x = ca. 50). The base number for the tribe is x = 10, which is foun d in various multiples. The Blennospermatinae are one of the most dist inct groups with a base of x = 9, considered an aneuploid reduction fr om x = 10. A new subtribe, Abrotanellinae, is established for the sout hern South American and southwest Pacific genus Abrotanella, which als o has x = 9 and has often been placed in the Blennospermatinae. Number s based on x = 30 and aneuploid reductions are found in the Tussilagin inae, in many Australian Senecio, and in the Macaronesian Pericallis o f the Senecioninae. The origin of such numbers is discussed. An anomal ous North American group of Senecio (Packera) has variable numbers mos tly 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 Hemi sphere, and groups like Emilia have recently dispersed from that area. Occurrences of n = 5 in Emilia, n = 10 in some American and Australia n Senecio, and n = 14-16 in some tussilaginoids are considered as redu ctions.