Neotropical Ticodendraceae

Description

Medium-sized cloud forest tree. Leaves alternate, elliptic-ovate, subcoriaceous with pinnate venation (8-13 secondary veins), serrate margins, glabrous upper sides and variable density of simple hairs on abaxial surface (woolly in early stages); petioles grooved above; stipules encircling stem, caducous (leaving scar). Flowers unisexual, borne on catkins 1.5-4 cm long, either simple or with cymulose branching and sometimes terminating with a single female flower. Male flowers with no perianth and 4-8 (-many) anthers in 2-4 verticils; borne on 1- to 3-flowered partial inflorescences distributed verticillately along main axis and each subtended by a single bract; anthers basifixed, dehiscing through longitudinal slits. Female flowers solitary, 2(-3) stigmas with vestigial perianth on top of ovary, each flower subtended by three deciduous bracts; ovary inferior, syncarpous (2 carpels), 4-locular. Fruit an asymmetrical drupe, somewhat fleshy and mucilaginous, with a single seed.

Notes on delimitation

• There has been much discussion of the placement of this family, with suggestions including Urticales, Dilleniales and Rosales (Gómez-Laurito & Gómez, 1989). 
• Subsequent anatomical studies (e.g. Tobe, 1991) indicated that it would be more appropriately in the Fagales. 
• This has since been supported by molecular studies (e.g. Manos & Steele, 1997), placing it close to Betulaceae and in a common clade with the Casuarinaceae.

Distribution in the Neotropics

• Central America (Costa Rica, Guatemala, Panama, Nicaragua, Honduras) and Mexico.
• In sparse stands or as isolated individuals in montane evergreen forest.

Distinguishing characters (always present)

• There are no completely distinctive features, hence the initial uncertainty about the status of this family (see above). 
• It is the combination of characters (i.e. simple alternate leaves with serrate margins, stipules encircling the stem, catkin-like inflorescences with absent or vestigial perianth, inferior ovary, drupaceous fruit...) that defines it. 
• However, the structure of the inflorescence, with its arrangement of unisexual flowers in cymules (partial inflorescences) subtended by bracts and distributed along the main axis in verticils (male) or solitary (female), sometimes with a female flower at the end of a male inflorescence, provides an identifiable combination.

Other important characters

• The wood is yellowish, and the bark slash reputedly has a purplish tinge.

Key differences from similar families

This family may perhaps be confused with other members of the Fagales, but differs in the following ways:

• Fagaceae - drupaceous fruit, circular stipule scar around twig.
• Betulaceae - drupaceous fruit (otherwise quite similar to Alnus Mill, but differs in its circular stipule scar).
• Myricaceae - absence of gland dots in leaves, inferior ovary.
• Juglandaceae - simple leaves.
• Cecropiaceae - Although its leaves and stipule scars are superficially similar to some Cecropiaceae, it differs in its bicarpellate ovary and the well differentiated and free stigmas.
• Ticodendron also bears a resemblance to certain Ulmaceae such as Zelkova Spach, but differs in its four ovules (three of which abort in the early stages of development).

Number of genera

• One genus, Ticodendron Gómez-Laur. & L.D.Gómez, with only one species (T. incognitum Gómez-Laurito & Gómez P.)

Status

• Native.

General notes

• Known locally as jaúl macho, jaúl nazareno, duraznillo or candelillo morado.
• Its wood is used for fuel.

Important literature

Gómez-Laurito, J. & Gómez P., L.D. (1989). Ticodendron: a new tree from Central America.  Ann. Missouri Bot. Gard. 76:1148-51.

Gómez-Laurito, J. & Gómez P., L.D. (1991). Ticodendraceae: a new family of flowering plants.  Ann. Missouri Bot. Gard. 78:87-88.

Hammel, B.  and W. G. Burger . 1991. Neither oak nor alder, but nearly: the history of Ticodendraceae. Ann.Missouri Bot. Gard. 78:89-95.

Manos, P. S. and K. P. Steele. 1997. Phylogenetic analyses of 'higher' Hamamelididae based on plastid sequence data. Amer. J. Bot. 84:1407-1419.

Tobe, H. (1991). Reproductive morphology, anatomy and relationships of Ticodendron.  Ann. Missouri Bot. Gard. 78:135-142.

Stevens, P. F. (2001 onwards). Angiosperm Phylogeny Website. Version 9, June 2008.