Biological Journal of the Linnean Society, 2003, 80, 261–268. With 2 figures © 2003 The Linnean Society of London, Biological Journal of the Linnean Society, 2003, 80, 261–268 261 Blackwell Science, LtdOxford, UKBIJBiological Journal of the Linnean Society0024-4066The Linnean Society of London, 2003? 2003 802 261268 Original Article CAM IN PITCAIRNIOIDEAE F. REINERT ET AL. *Corresponding author. E-mail: claudia@biologia.ufrj.br The evolution of CAM in the subfamily Pitcairnioideae (Bromeliaceae) FERNANDA REINERT 1 , CLAUDIA A. M. RUSSO 2 * and LEANDRO O. SALLES 3 1 Departamento de Botânica, Instituto de Biologia, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil 2 Departamento de Genética, Instituto de Biologia, Centro de Ciências da Saúde, Universidade Federal do Rio de Janeiro, Rio de Janeiro, RJ 21541–570, Brazil 3 Departamento de Vertebrados, Museu Nacional, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil Received 28 August 2002; accepted for publication 7 March 2003 A molecular phylogeny for the subfamily Pitcairnioideae was inferred to examine the distribution of crassulacean acid metabolism in the subfamily. For this purpose, a neighbour-joining tree with p-distances was built using a MatK chloroplast gene data set. The phylogenetic results of our analysis confirmed the monophyletic condition of most gen- era examined: Brocchinia, Dyckia, Encholirium, Fosterella, Hechtia and Puya. A paraphyletic basal sequence showed Hechtia branching off from the basal node, followed by Brocchinia, Cottendorfia + Navia phelpsiae, and Puya. The remaining taxa were divided into two groups: (a) Deuterocohnia meziana, Dyckia, Encholirium; Fosterella; Deutero- cohnia spp. + Pitcairnia heterophyla; (b) Pepinia, Pitcairnia spp. and Navia igneosicola. The basal placement of the CAM genera Hecthia indicates that CAM may be a ‘primitive condition’ in Pitcairnioideae and that C 3 species may have lost the ability to induce CAM. In this molecular tree, CAM metabolism appeared scattered throughout the tree. Current knowledge, however, does not exclude the possibility that CAM arose only once and it has been switching on and off in various lineages. Further detailed studies on photosynthetic metabolisms and the phylogenetic distri- bution of characters will provide a better basis on which to evaluate photosynthetic origins. © 2003 The Linnean Society of London, Biological Journal of the Linnean Society, 2003, 80, 261–268. ADDITIONAL KEYWORDS: chloroplast gene MatK – molecular systematics – photosynthetic metabolic pathways – plant phylogeny. INTRODUCTION Crassulacean acid metabolism (CAM) is a metabolic pathway found in the photosynthetic tissues of some plants. At night CAM plants take up CO 2 which is fixed into malate via phosphoenolpyruvate carboxy- lase (PEPC). During the day, malate is decarboxylated and the CO 2 is used in the C 3 pathway (photosynthetic carbon reduction cycle). CAM-type PEPC is quite dif- ferent from C 3 and C 4 types. For instance, the V max of CAM-type PEPC is C 4 -like but its relatively low K m is C 3 -like (Leegood, 1993). Furthermore, CAM-type PEPC is a tetramer whereas the C 4 type is a dimer, which may account for its lower sensitivity to malate inhibition and to pH variation (Wedding, Black & Meyer, 1990). During CAM circadian cycles, PEPC is activated by kinase phosphorylation while higher levels of PEPC and PEPC-mRNA regulate CAM metabolism during transition from C 3 to CAM in intermediate plants (Ting et al., 1993). CAM plants minimize water loss through evaporation by opening their stomata mostly at night, differing from C 3 and C 4 species. Thus, when- ever water supply is low or day-time temperatures are high, CAM plants have an enormous physiological advantage over C 3 and C 4 plants. In the plant kingdom, CAM is widely and discontin- uously distributed. More than 10% of all vascular Downloaded from https://academic.oup.com/biolinnean/article/80/2/261/2636364 by guest on 01 July 2022