Molecular systematics and growth form evolution in the tribe (Cactaceae) Anita Lendel1,2 , Reto Nyffeler2 [email protected]; 2 Institut of Systematic Botany, University of Zürich, Switzerland

Growth form evolution

Cacti are very remarkable for their great diversity of specialized growth forms. The evolution of these characteristics, however, is still not un- derstood. The traditional idea formulated by Buxbaum in his „law of the abbreviation of the vegetative phase” is that there is a general „trend” in evolution leading from branched, columnar forms to unbranched, globular types. Trends usually have been described on the basis of morphoclines in order to establish evolutionary hypotheses, from which phylogenetic diversity is inferred. This is still the prevailing concept in current classi- fication systems in cacti. Instead, a better understanding of a wide range of morphological diversity could be provided from robust phylogenetic analyses, allowing to reconstruct the complex pattern of growth form evolution.

Results from phylogentics studies Growth form evolution — first investigations

Preliminary results from a molecular systematic analyses indicates that The preliminary findings illustrate the complex patter of growth form some lineages with exclusively globular growth forms (in particular evolution. Phylogenetic relationships among selected exemplars of and ), which previously have been thought to Trichocereeae mapped onto stem height character space and a classifi- be “highly derived” within Trichocereeae (in green), are not part of the cation into six growth-form classes. core group of the tribe. Furthermore, the sensu lato is 8(m) found to be polyphyletic. Esp. lan

Rau. rios outgroups 4 Ore. cel

Cereus alacriportanus M at 99 Micranthocereus albicephalus . in O t 2 Brasilicereus markgrafii ro . p Uebelmannia pectinifera er Ha Stetsonia coryne a. pse 80 zehntneri 1 Mil. 100 Melocactus zehntneri cae . rho Azureocereus hertlingianus Den Browningia chlorocarpa Ech 0.5 96 Pilosocereus floccosus . gla Ech Pilosocereus fulvilanatus . pen 63 Coleocephalocereus fluminensis Art. gla dybowskii or c m 0.2 62 . o Gymnocalycium denudatum m p a . i S r h a c Rebutia spinosissima H . h c Rebutia fidaiana E u a Cintia knizei b 0.1 . Rebutia steinbachii le C it 89 . r lanata le Rauheocereus riosaniensis C 0.05 c

Oreocereus celsianus o Gym. den

98 r

95 e 75 intertexta Reb. spi peruviana T fid Reb. pseudom. r i i kn Mila caespitosa c Cin. 62 rhodacantha h o b. ste 54 Re 0.01 Echinopsis glaucina c Echinopsis pentlandii e r

Arthrocereus glaziovii e Samaipaticereus corroanus e 87 a pomanensis e The patterns of character transition among the different growth form Echinopsis chiloensis 100 baumanii types in Trichocereeae are Cleistocactus ritteri now going to be investigat- ? ? Strict consensus of 46989 most-parsimonius trees of length 1237 derived from an analysis ed with the help of phylo- of the combined trnK/matK, rps16 and trnS-trnG data set. Bootstrap values are given above genetic correlation analyses the branches. ? ? and the estimation of trans- ? ? formation rate differences. The latter will be done in a ? ? likelihood framework using the software program MUL- TISTATE.