Melocactus broadwayi (Britton & Rose) Berger (1926: 78

Hoxey, Paul & Gdaniec, Andrew, 2021, An evaluation of the Cactaceae of Barbados, Grenada, Saint Vincent, and The Grenadines, Phytotaxa 483 (1), pp. 25-74 : 40-46

4. Melocactus broadwayi (Britton & Rose) Berger (1926: 78 , 103) ≡ Cactus broadwayi Britton & Rose (1922: 229) ≡ Melocactus intortus subsp. broadwayi (Britton & Rose) Guiggi (2006: 340) .

Type:— TRINIDAD AND TOBAGO. Tobago Island, 1921, G. Freeman s.n.

Lectotype (designated here):—[icon] fig. 231 in Britton & Rose (1922) ( Fig. 14 ).

Description:—Plants a little taller than wide, to 20 cm across, yellowish green, sometimes branching from the body just below the cephalium to form clusters of 10–15 heads. Ribs 14–18, 10– 15 mm high, 10–20 mm wide at base, rounded. Areoles round with white felt. Radial spines 8–12, spreading, slightly curved inwards, reddish brown but fading to straw yellow with age. Central spines 1–3, similar to radials but a littler stouter. Cephalium small, 6–7 cm broad and a little less tall, made up of soft reddish-brown bristles and white wool. Just occasionally a plant is found with an elongated cephalium, taller than wide. Flowers pink, opening mid-afternoon. Fruit clavate, 25 mm long, purple red.

Distribution in the study area ( Fig. 2D ):— Outside of Tobago island (locus classicus of Melocactus broadwayi ) this species occurs on Grenada, Saint Vincent, and the majority of The Grenadines. We confirmed the distribution within the Grenadines Islands, but with one notable exception, Union island (see next species for an explanation for this anomaly).

Melocactus broadwayi is rather difficult to find in the main islands of Saint Vincent and Grenada. On Saint Vincent we only encountered one population with the help of some local fishermen. The plants grow on a high, vertical coastal cliff and are only visible and accessible by boat. This population on Saint Vincent was cited by Plumier, so we were pleased to find it still in existence after over 300 years. M. broadwayi probably has a very limited distribution on Saint Vincent because of the lack of exposed rocky areas and the range is restricted to vertical coastal cliffs. On Grenada the species is likely to be present in larger numbers, but restricted again to coastal habitats. We found just two small populations with only a handful of plants in each. It is becoming scarce there because of collecting and habitat destruction due to coastal development. A local guide took us to one population but we could only find two or three small plants where he said there used to be many. He blamed the situation on local inhabitants collecting plants for horticultural use. Healthy and much larger populations still exist on The Grenadines, especially the more remote uninhabited islands and rocks where they can be found in good numbers.

General distribution:— Outside of the study area the species is only known with certainly from Tobago island (the type location). Note that on Saint Lucia, the next island to the north of Saint Vincent, neither Howard (1989: 408) nor Taylor (1991: 78) report M. broadwayi and we believe the Melocactus found there is referable to M. intortus .

Discussion:— We are treating Melocactus broadwayi as a distinct species, following Howard (1989: 408), Taylor (1991: 78), and Hunt et al. (2006: 186). M. broadwayi has been considered as closely related to Melocactus intortus , which grows further north in the Lesser Antilles. Guiggi (2006: 340) proposed M. broadwayi as subspecies of M. intortus (new proposed combination by Guiggi l.c.). Morphological differences between M. broadwayi and M. intortus refer to stem (smaller), cephalium (shorter), radial spines (curved vs. straight in M. intortus ) (see Fig. 15 ), flowers larger, clearly emerging beyond the cephalium (vs. slightly emerging in M. intortus ), and having thin petals (about 4–6 longer than broad vs. about 2 times longer than broad in M. intortus ), which often recurve backwards (vs. not bend backwards in M. intortus ); Fig. 16 , and stigma lobes (white and exserted vs. pink and not exserted in M. intortus ).

The flower structure of Melocactus broadwayi is much more reminiscent of the “curvispinus” group of Melocactus as defined by Taylor (1991: 61). This group has a very wide distribution from Peru, Colombia, Mexico, Venezuela, and the Caribbean region ( Cuba, the Dutch Antilles, Venezuelan offshore islands and possibly Jamaica). We believe that M. broadwayi is a member of this group and not closely related to M. intortus . The nearest population of a taxon in the “curvispinus” group is Melocactus curvispinus subsp. caesius (Wendland) Taylor (1991: 75) from Patos Island between Venezuela and the island of Trinidad (see Britton 1921).

The morphology of the plants in the field is usually constant in all populations visited with similar-sized bodies. We usually found a few plants per population in the fruiting stage and at some localities, flowers too. Most individuals remain unbranched but some form new heads from the body just below the cephalium. This generally results in a ring of heads, which in turn will produce cephalia. This behaviour is not restricted to individuals that have a damaged apex and the branching is probably an adaptation to increase flowering capacity without extending the original cephalium. The population on Frigate Island (south coast of Carriacou) is the best place to observe the large multi-branched specimens ( Fig. 17 ). We observed good seedling recruitment in most populations and young immature plants are present in significant numbers.

Melocactus broadwayi is usually found growing on exposed rocks or grassy banks close to the sea with little other vegetation. Unlike Mammillaria mammillaris it is not just restricted to steep cliffs and will grow on flatter terrain. It can often be the dominant plant on these inhospitable habitats ( Fig. 18 ). Plants can often be found on coastal rocks, just a few metres from the sea where they must be able to survive the salt spray and occasional submergence in sea water during stormy conditions ( Fig. 19 ).

Typification of Melocactus broadwayi :— Britton and Rose (1922: 230) stated in the protologue that the type material of Cactus broadwayi was collected by W. G. Freeman from Tobago in 1921 and they continued: “Figure 231 is from a photograph of the plant sent by W. G. Freeman from Tobago ”. This illustration can be considered type material. There is also a specimen in New York Botanical Garden (NY00118694!) which is annotated “ Cactus broadwayi B&R Tobago, B.W.I. W.G. Freeman 1921”. This is may be the plant illustrated by Britton and Rose but it has not been stamped “Examined for THE CACTACEAE ”. There is no evidence it was preserved prior to the publication of the protologue so it is not strictly eligible as the lectotype according to the Art. 9.3 of ICN. That leaves the illustration ( Britton and Rose 1922: Fig. 231) as the only type material cited in the protologue, which we designated here as the lectotype.

Specimens examined:— GRENADA. 4–10 March 1979, Howard 18829 (NY) .

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 14. Reproduction of the lectotype illustration of Cactus broadwayi (≡Melocactus broadwayi) (Britton and Rose 1922: Fig. 231).

FIGURE 15. Typical example of Melocactus broadwayi (Hoxey 1669.01) in fruit, growing on Petit Mustique.

FIGURE 16. Melocactus broadwayi (Hoxey 1663.01) in flowers with long recurved petals and well exerted from the cephalium, Bequia.

FIGURE 17. Multi-headed Melocactus broadwayi (Hoxey 1695.03) growing on Frigate Island, off the south coast of Carriacou.

FIGURE 18. Dense population of Melocactus broadwayi (Hoxey 1703.0) on the windswept coast of Sandy Island, Grenada.

FIGURE 19. Melocactus broadwayi (Hoxey 1668.02) on coastal cliffs just out of the reach of the waves breaking on the rocks below, The Pillories, north of Mustique.