The Lobelioideae is a cosmopolitan group whose cytoevolution is discus
sed on a model of primitively high diploid chromosome numbers, in whic
h x = 14 is relatively plesiomorphic and x = 21 may be even more plesi
omorphic. This model is suggested from the high frequency of lobelioid
genera with x = 14, the probably plesiomorphic condition of x = 17 in
the sister group Campanuloideae (Campanulaceae). and the primitive x
= 15 in Stylidiaceae (Campanulales). It contrasts with that for a prim
itive x = 7 and paleopolyploidy to higher chromosome numbers. In our a
nalysis, the genus Lobelia shows three broad cytoevolutionary groups,
which probably have phylogenetic and infrageneric taxonomic significan
ce: (1) woody diploids with s = 21 in Chile and woody diploids with x
= 14 in Africa, Asia, and Hawaii: (2) herbaceous diploids with several
series of dysploid chromosome numbers n = 19, 13, 12, 11, 10, 9, 8, 7
, 6, mainly in Africa and Australia; (3) widespread and speciose herba
ceous taxa based on a very derived n = 7, with recent frequent euploid
rises (neopolyploidy) at or below the species level in subgenus Lobel
ia and allied or segregate genera. Other woody and herbaceous lobeliad
genera have comparable cytoevolutionary patterns. New chromosome coun
ts Cor Australian Lobelia, Pratia, and Isotoma illustrate the last two
cytoevolutionary groups.