Theor Appl Genet (1996) 92:375 381 9 Springer-Verlag 1996 K. Zunk 9 K. Mummenhoff . M. Koch 9 H. Hurka Phylogenetic relationships of Thlaspis.I. (subtribe Thlaspidinae, Lepidieae) and allied genera based on chloroplast DNA restriction-site variation Received: 7 September 1995 / Accepted: 22 September 1995 Abstract Chloroplast DNA restriction-site variation was analyzed in 30 accessions representing 20 species from the major lineages in ThIaspi s.l. (previously described as genera by Meyer 1973, 1979) and allied genera from the subtribe Thlaspidinae (Peltaria, Tees- dalia, Cochlearia, Ionopsidium, Aethionema). A total of 161 variable restriction sites were detected. Phylogenetic analyses indicated a division of Thlaspi s.1. into three groups consistent with Meyer's genera Thlaspi s. str., Microthlaspi and Noccaea/Raparia. The genus Thlaspi s.1. as currently described proved to be paraphyletic because one of its major lineages, i.e. Thlaspi s. str., appeared to be more closely related to other genera (Peltaria, Teesdalia) than to the remaining lineages of Thlaspi s.l., i.e. Noccaea/Raparia and Microthlaspi. Se- quence divergence values (100 x p) between the Thlaspi s. 1. lineages were similar to values between these groups and related genera (Teesdalia, Peltaria), respectively. Chloroplast DNA variation was also used to assess subtribal classification of the genera studied. The cpDNA data were inconsistent with the controversial taxonomic classifications based on morphology. The molecular data would suggest that (1) the subtribe Thlaspidinae, as traditionally described, is not mono- phyletic; (2) the Thlaspidinae should be reduced to a group consisting of Thlaspi s. str., Peltaria, Teesdalia, Microthlaspi, Noccaea/Raparia, and that Aethionema should be excluded from the Thlaspidinae; and (3) Coch- learia and Ionopsidium represent the subtribe Coch- leariinae. Key words Thlaspi 9 Subtribe Thlaspidinae 9 Brassicaceae 9 Chloroplast DNA 9 Restriction-site variation 9 Molecular systematics Communicated by R. Hagemann K. Zunk 9 K. Mummenhoff 9 M. Koch 9 H. Hurka Spezielle Botanik, Fachbereich Biologie Universit/it Osnabriick, Bar- barastral3e 11, D-49069 Osnabriick, Germany Introduction Thlaspi L. s.1. is the largest genus of the subtribe Thlas- pidinae (tribe Lepidieae) and comprises approximately 75 species (A1-Shehbaz 1986). This genus is primarily defined by fruit characters (fruit an angustiseptate silicule, the valves keeled and usually winged; locules containing 2-6, rarely 1 10, seeds). Several controver- sial infrageneric classifications have been proposed, mainly based on fruit characters (reviewed in Mummen- hoffand Koch 1994). Meyer (1973, 1979) questioned the naturalness of the genus Thlaspi s.1.. By analyzing the anatomy of the seed testa, Thlaspi s.1.. was split into 12 segregate genera; the differences between them were considered too great to warrant their subordination, as sections or subgenera, to a single, broadly defined genus (Meyer 1973, 1979). This concept, however, was not followed by other authors (Hedge 1976; A1-Shehbaz 1986; Greuter et al. 1986; Schultze-Motel 1986). Recent- ly we have studied Thlaspi s.1. by isoelectric-focusing (IEF) analysis of Rubisco subunits (Mummenhoff and Zunk 1991) and cpDNA restriction-site analysis (Mum- enhoff and Koch 1994). The major splits in Thlaspi s.1. were strongly confirmed relative to the taxa studied and they correspond to Meyer's segregates Thlaspi s.str, Microthlaspi und Noccaea (including Raparia). Chloro- plast DNA sequence divergence between these groups was higher than that usually found in intrageneric ana- lyses and comparable to levels of divergence between related genera of other angiosperm families (Mummen- hoff and Koch 1994). Nevertheless, critical evaluation of the taxonomic status of these segregates should await the analysis of related genera such as Aethionema, Pel- taria and Teesdalia. Tribal, subtribal, and even generic, boundaries in the Brassicaceae are often arbitrarily drawn and, therefore, these taxa may often not reflect natural groups (Hedge 1976; A1-Shehbaz 1984). Likewise, there is little agree- ment among the various morphologically based classifi- cations as to the limits of the Thlaspidinae (Hayek 1911;