Zygophyllum L.
A genus with about 117 species typical of the tropical and arid zones of the western half of the Old World, reaching adjacent areas of Mediterranean and/or very continental climates (Central Asia) and with some more presence in the Neotropical region. The genus has undergone many modifications in its taxonomic treatment: initially it was a genus with a large number of species, including those with succulent leaflets and schizocarp fruit. Subsequently these species were joined with another present in Inner Mongolia (Tetraena mongolica) in the genus Tetraena (Beier et al., 2003). Currently, a more synthetic treatment is opted for (Christenhusz et al. 2018), which merges both genres.
According to Beier et al. (2003), the fruits of species formerly included in Tetraena are schizocarps, not capsules. Although the term “capsule” is used throughout the literature consulted, except in Flora Iberica, the terminology proposed by Beier et al. (2003) is followed here. To refer to the appendages of the staminal filament, the term “scale” is used.
The type species of the genus is Z. fabago L. a herbaceous perennial plant with a somewhat lignified base, it can reach up to 1(1.5) m in height, leaves bifoliolate, flat, not fleshy, ellipsoid leaflets and fruits an elongated capsule (3-4 cm), dehiscent, with 4-5 flattened seeds; it grows in nitrified and even anthropic environments (walls, ruins, etc.); it is possibly native to the eastern Mediterranean region; in North Africa it was cited in Egypt, where it seems to have become extict [Red List of the Vascular Plants of Egypt (Flora Aegyptiaca Vol 1, 2000)], however since the past few centuries, it has been widely distributed almost anywhere in the world, possibly due to human activity. Currently, it has not been assessed at a global level on the IUCN Red List of Threatened Species.
Barone, R. 2003. Zygophyllum wartelotii Maire (Zygophyllaceae), nueva cita para el Archipiélago Canario. Bot. Macaronésica 24: 173-178.
Beier, B.A., Chase, M.W. & Thulin, M. 2003. Phylogenetic relationships and taxonomy of subfamily Zygophylloideae (Zygophyllaceae) based on molecular and morphological data. Plant Systematics and Evolution, 240(1/4): 11-39.
Ghazanfar, S. & Osborne, J. 2015. Typification of Zygophyllum propinquum Decne. and Z. coccineum L. (Zygophyllaceae) and a key to Tetraena in SO Asia. Kew Bulletin 70: 38.
Hosny, A. I. 1977. New taxa of Zygophyllum from Egypt. Bot. Notiser 130: 467-468.
Marrero, M.V. & Carqué, E. 2004. Zygophyllum gaetulum. In Bañares et al. Atlas y Libro Rojo de la Flora Vascular Amenazada de España. Dirección General de Conservación de la Naturaleza. Madrid. 915.
Key to species
1 Leaflets flat Zygophyllum decumbens
1 Leaflets thick, circular in cross section 2
2 Fruit winged, with wings wider than the middle part of the fruit Zygophyllum dumosum
2 Fruit wingless 3
3 Fruit not subglobose 5
3 Fruit subglobose 4
4 Length of fruit peduncle subequal to that of the fruit. Schizocarp with small warts Zygophyllum geslinii
4 Length of fruit peduncle shorter than the fruit (¾ of its length). Schizocarp smooth Zygophyllum fontanesii
5 Fruit cylindrical or subcylindrical, with top half not expanded into 5 free lobes 6
5 Fruit pyriform, bell-shaped or obconic, with top half expanded into 5 free lobes 7
6 Fruit peduncle same or longer than the fruit Zygophyllum coccinea
6 Fruit peduncle shorter than the fruit (Z. gaetulum waterlotii) Zygophyllum gaetulum
7 Fruit with extended or recurved apical lobes 8
7 Fruit with neither extended nor recurved apical lobes 9
8 Mature fruit with the lower part subequal to the recurved apical lobes Zygophyllum cornutum
8 Mature fruit with the lower part longer than the apical lobes (c. 1-3 mm) not recurved (Z. gaetulum gaetulum) Zygophyllum gaetulum
9 Solitary flowers Zygophyllum album
9 Flowers arranged in groups of 2-3(4) Zygophyllum aegyptium
Updated by: J.F. Mota, J. Güemes & F.J. Pérez García.