Opuntia dillenii (Ker Gawler) Haworth (1819: 79)

Hoxey, Paul & Gdaniec, Andrew, 2021, An evaluation of the Cactaceae of Barbados, Grenada, Saint Vincent, and The Grenadines, Phytotaxa 483 (1), pp. 25-74 : 49-50

6. Opuntia dillenii (Ker Gawler) Haworth (1819: 79) ≡ Cactus dillenii Ker Gawler (1817 : t. 255) ≡ Opuntia stricta var. dillenii (Ker Gawler) Benson (1969: 126) .

Type:— not stated but in cultivation in London (not preserved).

Lectotype (designated by Benson 1969: 126):—[icon] t. 255 in Ker Gawler (1817, image of the lectotype available at https://www. biodiversitylibrary.org/item/9039#page/251).

Description:—Plant forming extensive clumps of spreading pads ( Fig. 24 ). Joints obovate to oblong, epidermis blueish green and glaucous. Areoles evenly spaced with white felt. Spines stout, 2–10, usually curved, yellow. Glochids numerous, yellow, appear from upper edge of areoles only (but occasionally absent). Flowers usually appear on the edge of the pads. yellow (orange-yellow on Barbados) petals. Fruits (when mature) 7–9 cm long, purple red, juicy red pulp, usually spineless but with numerous glochids.

Distribution in the study area ( Figs. 2F–2I ):— Opuntia dillenii is found on most of The Grenadines and Grenada, but not on Saint Vincent. It also occurs on Barbados. On Barbados we only found the species on the north coast of the island, growing on coral limestone and in the Scotland sandstone district.

General distribution:— This species is widespread in the Lesser Antilles and Greater Antilles.

Discussion:— We agree with the taxonomic treatment by Howard (1989: 412) and Taylor & Zappi (2004: 192) who recognized Opuntia dillenii as a separate species widespread in the Caribbean region. On the other hand, Hunt et al. (2006: 202) suggested it may just be a spiny form of Opuntia stricta . We consider O. dillenii as a native species of the Lesser Antilles. Note however, that the fruit is sweet, edible, and a useful as food source, so it may have been introduced by human at least in some sites. Early settlers could easily have dispersed this species by transporting pads as they travelled amongst the islands. Nevertheless, it is probably dispersing itself naturally now as we encountered the species on small islands of difficult access (e.g. Pigeon island off Bequia) which is unlikely to have been inhabited, and local people take little interest in the plant today.

The flower of Opuntia dillenii is reported to be yellow, but on Barbados it is orange-yellow coloured. We only saw flowering plants on Union Island ( Fig. 25 ) and Barbados ( Fig. 26 ) and confirmed this observation. Most plants had green immature fruits but occasionally we found mature purple fruits ( Fig. 27 ).

Howard (1989: 415) reports Opuntia wentiana from Grenada, the only locality he notes in the Lesser Antilles. This is supported by the specimen R.A.Howard 18335 (A01677346!) collected at Pointe Saline. We failed to find this species on Grenada and we believe Howard’s specimen is probably a weakly-spined form of O. dillenii , either growing in poor conditions or showing juvenile characteristics.

Specimens examined:— BARBADOS: 30 September, 1915, Rose 21180 (US). GRENADA. 30 March 1977, Howard 18335 (A); Carriacou, 7–25 March 1950, Howard 10891 (GH) . ST. VINCENT & THE GRENADINES. Bequia , 20 March 1977, Howard 18245 (A) .

Figures

FIGURE 2. Distribution of cacti on Barbados, Grenada, Saint Vincent and the Grenadine islands based on observations by the authors. A. Acanthocereus tetragonus. B. Cereus repandus. C. Mammillaria mammillaris. D. Melocactus broadwayi. E. Melocactus intortus. F. Opuntia dillenii. G. Pilosocereus curtisii H. Selenicereus plumieri I. Opuntia dillenii (Barbados). J. Pilosocereus barbadensis (Barbados).

FIGURE 24. Opuntia dillenii (Hoxey 1695.04) with Frigate Island, off the south coast of Carriacou.

FIGURE 25. Opuntia dillenii (Hoxey 1676.03) yellow flower, Union Island.

FIGURE 26. Opuntia dillenii (Hoxey 1708.02) with orange flower, Barbados.

FIGURE 27. Opuntia dillenii (Hoxey 1704.05) pad with typical spination and ripe fruit, Ronde Island.