Metteniusaceae H.Karst.ex Schnizl.

Every, J.L.R. (2009). Neotropical Metteniusaceae.

Morphology

Description

Evergreen trees (4-20m tall); indumentum of 2-branched hairs. Leaves simple , alternate , petiolate , leathery, margins entire ; venation pinnate , tertiary veins parallel and +/- perpendicular to the midrib . Inflorescence an axillary cyme of up to 17 flowers. Flowers on short pedicels, bracteate, actinomorphic , bisexual ; calyx 5 lobed , imbricate , slightly fused at the base, persistent in fruit ; corolla fused for 1/3 of its length into a narrow tube, 5 lobed , lobes reflexed , inner surface tomentose ; stamens 5, alternipetalous, adnate to corolla , strongly exserted , monifliform, hairy sagittate anthers; ovary superior , carpels 4 highly reduced (appearing monomerous), unilocular, ovule 1, pendent from the apex , style 1, 2cm long. Fruit a drupe , asymmetrically ridged, 5-ribbed, mesocarp leathery, endocarp woody , indehiscent . Seed 1, endosperm abundant, white.

Distribution

Distribution in the Neotropics

• Canopy trees found from Costa Rica in montane forests down along the Andes of Colombia to Venezuela and into Ecuador and Peru at up to 2,000m.

Diagnostic

Distinguishing characters (always present)

• Flowers c. 4 cm.
• Moniliform anthers (resembling a string of beads), 1 cm long.
• Uniovulate ovaries.
• Stamens connected to the petals.
• 2 bracts immediately below the calyx.
• Stamens exserted.
• Filaments 1.5 cm long, free and curled backwards.
• Style 2 cm in length.

Other important characters

• Flowers fragrant.

Key differences from similar families

Metteniusa can be told apart from the following families (some of which have contained the genus) by the highlighted features, which the Metteniusaceae do not have:

• Cardiopteridaceae - small flowers (c. 4mm), stamens not exserted, small domatia on the underside of the leaves, two ovules, scorpioid inflorescence.
• Icacinaceae - free petals, two ovules and smaller flowers (3-7mm).
• Stemonuraceae - free petals, flat filament densely covered with white club-shaped hairs, the fruit flattened, bearing a large oblongfleshyappendage.
• Olacaceae - stamens opposite petals.
• Opiliaceae - unisexual flowers with tepals.
• Cornaceae - inferior ovary.

General Description

Number of genera

• Monogeneric: Metteniusa H.Karst.

Status

• Exclusively Neotropical.

General notes

• M. edulis H. Karst. has fruits which are reportedly edible.

Notes on delimitation

• The genus has been hard to place and has mainly found itself as a member of the Icacinaceae.
• The Metteniusaceae has, however, been sporadically accepted as a family in its own right ever since Karston (1859) described it in the Flora of Colombia.
• Recent molecular work has strengthened the case for the monotypic family as Gonzalez et al (2007) placed Metteniusa H.Karst. as an isolated genus near the base of the lamiid clade.

Literature

Important literature

González, F., J. Betancur, O. Maurin, J. V. Freudenstein & Mark W. Chase. 2007. Metteniusaceae, an early-diverging family in the lamiid clade. Taxon 56(3): 795-800.

Howard, R. A. 1940. Studies of Icacinaceae. I. Genera to be excluded. Journal of the Arnold Arboretum 21: 485-6.

Karsten, G. K. W. H. 1859. Metteniusaceae. Pp79-80, t. 39 in: Florae Colombiae 1. Ferdinandi Duemmleri successors, Berlin.

Kårehed, J. 2001. Multiple origin of the tropical forest tree family Icacinaceae. American J. Bot. 88: 2259-2274.

Lozano-C., G. & de Lozano, N. B. 1988. Metteniusaceae. Flora de Colombia 11. Instituto de Ciencias Naturales, Universidad Nacional de Colombia, Bogata.

Maas, P. J. M. & Westra, L. Y. Th. 2005. Neotropical Plant Families. 3rd ed. P. 307. A.R.G. Gantner Verlag K.G., Ruggell.

Stevens, P. F. (2008). Angiosperm Phylogeny Website. Version 9 onwards. http://www.mobot.org/MOBOT/research/APweb/.

Utteridge, T.M.A. and Brummitt, R.K. 2007. Metteniusaceae. In: Heywood, V.H., Brummitt, R.K., Culham, A. and Seberg, O. (eds.). Flowering plant families of the world, p. 215. Kew: Royal Botanic Gardens, Kew.