Royal Botanic Gardens, Kew, U.K.
Shrubs, treelets or rarely trees, occasionally climbers, leaves deciduous and branches often armed; plants monoecious. Leaves simple, alternate, estipulate, entire. Inflorescence axillary, racemose, few-flowered, bracteate, greenish. Flowers small, greenish, hermaphrodite, actinomorphic, sepals (= tepals) 5, petals absent; stamens 10+, anthers 2-locular; ovary superior, 2-carpelate, unilocular, placentation basal< /A> , uni-ovulate, styles two, horn-shaped. Fruits fleshy, one-seeded, translucent or white, with remnants of sepals attached when ripe; seeds black, testa shiny.
Notes on delimitation
- The Achatocarpaceae has been treated as part of the Phytolaccaceae in the past, but now it stands alone as an independent family (APG II, 2003, Souza & Lorenzi 2005).
- Recent molecular studies using the markers rbcL and matK resolve Amaranthaceae-Chenopodiaceae as sister to the Achatocarpaceae (Kadereit et al. 2003, Cuénoud et al. 2002) and this evidence is supported by existing morphological data.
Distribution in the Neotropics
- The Achatocarpaceae is a small family (2 genera, 10-11 species) all endemic to the Neotropics.
Distinguishing characters (always present)
- Plants with alternate, simple, estipulate leaves with entire margins, often spiny.
- Flowers small, unisexual, in axillary racemes.
- Ovary superior, with one basal ovule and two horn-shaped stigmas.
- Sepals (= tepals) present, free< /A> ; petals absent.
- Fruit fleshy, one-seeded, white-translucent, sepals remaining in fruit.
Other important characters
Key differences from similar families
- It differs from the Amaranthaceae s.l. in having fleshy fruit with translucent skin (vs. dry fruit with different projections, dispersed mostly by wind); the Phytolaccaceae have mostly bi-many-locular ovaries, while the Achatocarpaceae has a one-locular ovary with one ovule.
Number of genera
1. Achatocarpus L. - around 10 species distributed mostly in Central and Northwestern South America in dryland vegetation.2. Phaulothamnus - a single species, P. spinescens A. Gray, from Mexico and S. United States.
- Endemic to the Neotropics. See above.
APG II, 2003. An update of the Angiosperm Phylogeny group classification for the orders and families of flowering plants: APG II. Bot. J. Linn. Soc. 141(4): 399-436.
Cuénoud, P., V. Savolainen, L.W. Chatrou, M. Powell, R.J. Grayer & M.W. Chase. 2002. Molecular phylogenetics of Caryophyllales based on nuclear 18S RDNA and plastid rbcL, atpB, and matK DNA sequences. Amer. J. Bot. 89(1): 132-144.
Souza, V.C. & Lorenzi, H. 2005. Botânica Sistemática: guia ilustrativo para identificação das famílias de Angiospermas da flora brasileira, baseado em APG II. Nova Odessa, Brazil: Instituto Plantarum.
How to cite
Zappi, D. (2009). Neotropical Achatocarpaceae. In: Milliken, W., Klitgård, B. & Baracat, A. (2009 onwards), Neotropikey - Interactive key and information resources for flowering plants of the Neotropics. http://www.kew.org/science/tropamerica/neotropikey/families/Achatocarpaceae.htm.