Opuntia bentonii Griffiths, Rep. (Annual) Missouri Bot. Gard. 22:25. 1911.

TYPE: FLORIDA: McClenny (Macclenny), cultivated plant, 26 Apr 1906, Harmon Benton s.n.; type specimen collected from cultivated plant (SAG), 24 Apr 1910, David Griffiths 8374 (HOLOTYPE: US- 2607635 [barcode 00115793]).

Note.— The voucher is notated“ HOLOTYPE,” but there is no indication when or by whom.The voucher was reannotated O.stricta by Lyman Benson in 1958 at the Herbarium of Pomona College via the Consortium of California Herbaria (2024) (Fig.1).

Distribution.— “… Fernandina, Florida, to the mouth of the Brazos [River, Texas], always in cultivation in the eastern portion of this range and native in southwestern Louisiana and Texas ” (Crook & Mottram 1995).

DESCRIPTION

Tight or irregular shrubs, 1.5–2 m across, 1–1.5(2) m tall; juvenile plants with semi-vertical or horizontal branches from which cladodes grow up and out, forming shrubs (Fig. 2). Cladodes subcircular, broadly ovate, or oval, 17–18 cm wide, to 28 cm long, never narrowly obovate; vascular system between areoles visible on first-year cladodes. Areoles widely spaced, elliptical, 3–4 per diagonal row, attended by light yellowish glochids initially less than 0.3 cm long in an adaxial crescent, often scattered throughout, in age lengthening to 1 cm and turning brown. Spines 0–2(3), 1.5–2.5 cm long, yellow, becoming white, gray, or black with age, porrect or gently deflexed, slender, terete, annulate with alternating shades of yellow, sometimes modestly twisted; occasionally shorter spines present, these semi-erect or gently reflexed; spines often absent from areoles; overall, plants modestly spiny in appearance (Griffiths 1911; Small 1933) (Fig. 3). Flowers yellow, attractive, 9–10 cm across, petaloid tepals broadly ovate, margins irregular; style greenish-white, stigma yellow or pale yellowgreen (never green); flower buds green, pointed sepaloid tepals ovate, acute, pointing toward the apex, unopened petaloid tepals rhomboid. Fruits copious, 3–4.5 cm long, egg-shaped or short-pyriform, areoles more or less distributed equally over surface of fruit; umbilici pronounced when new, later mildly depressed. Seeds numerous, roundish, modestly reniform ca. 2.5–3 mm in diameter, mostly flat, 1 mm unevenly thick margins (Fig. 4).

The only other large Opuntia growing in the foredunes along the east Texas Gulf Coast is O. anahuacensis. The two species were occasionally observed to be sympatric. They are easily differentiated (Table 1). Mature O. bentonii plants are shrubs to 1.5–2 m across and 1–1.5 m tall, whereas O. anahuacensis is a shorter, wider, low-spreading plant, 0.5(1) m tall and 2–3 m across. Opuntia bentonii has broadly obovate, oval, or subcircular cladodes that do not taper manifestly to their bases (Fig. 5). The surface of first-year cladodes may have elevated lines where vascular tissue connects areoles. Additionally, O. bentonii has all-yellow flowers, whereas O. anahuacensis may have all-yellow or red and yellow flowers. Opuntia bentonii has egg-shaped or short-pyriform, purplish-red fruits, whereas O. anahuacensis has pyriform, long-pyriform, or clavate fruits. Moreover, O. bentonii has yellow or pale yellowish-green stigmas in contrast to the white stigmas of O. anahuacensis.

Opuntia bentonii is not mentioned in the recent literature and botanists are generally unaware of the taxon. The reason for this may be because the species was conflated with the Florida beach cactus, O. stricta, by some authorities. However, O. stricta is not known to occur naturally in Texas. Or perhaps it has been confused with the very different O. anahuacensis (Table 1). Or because hundreds of vouchered herbarium specimens of O. stricta or O. dillenii (Ker Gawl.) Haw. are returned through a general online search for O. bentonii at the SEINet Portal Network (2024) (e.g., records ASU0297450 and PH 00777328). Narrowing the search to Texas returned about twenty records for O. stricta, but some were, in fact, O. anahuacensis or unidentifiable species. No records were recovered for O. bentonii in said searches. Misidentification of herbarium specimens is a persistent problem for Opuntia species that confounds the proper identification of plants (Majure et al. 2013). Likely all of these reasons account for the lack of information about O. bentonii. Nonetheless, searches of the Smithsonian Learning Lab (2024) and the Consortium of California Herbaria (2024) did recover images of several vouchered specimens. These vouchers were over 100 years old, and nothing more recent was recovered.

The ploidy of both species is unknown, and such knowledge would be useful differentiate them from other Texas Opuntia species.

ECOLOGY

Opuntia Small (1933) described plants of O. bentonii in northern Florida, but Griffiths (1911) reported that Florida plants of O. bentonii were always in cultivation and that O. bentonii was native only to southwestern Louisiana and Texas along the Gulf Coast. Populations of O. bentonii were observed by us in Louisiana from Sabine Lake to Pecan Island and west into Texas. Opuntia bentonii was observed by us in Texas in the foredunes at Matagorda, Seadrift, and Bolivar Peninsula, as well as Texas Point National Wildlife Reserve. At the latter location, infrequent plants of O. bentonii grew in the back dunes. Some plants of O. bentonii on Bolivar Peninsula grew near a popular, public beach and had been vandalized.

In the foredunes, there were generally no large shrubs except Yucca aloifolia L. and Y. recurvifolia Salisb., which sometimes grew in the general vicinity of O. bentonii at Texas Point National Wildlife Refuge. The cactus grew amongst typical low dune plants such as Uniola paniculata L., other perennial grasses and sedges, and herbaceous, broad-leaved plants including Amaranthus greggii S. Watson, Cakile geniculata (B.L. Rob.) Millsp., and Sesuvium portulacastrum (L.) L. The sporadic plants in the back dunes were loosely associated with Tamarisk sp, Iva frutescens L., and Baccharis halimifolia L. In most locations, the cactus was overgrown by the smaller plants, but judging by the robust fruit set, the plants did not appear to be adversely affected.The large, wide, shallow root systems reported for other Opuntias (Ramakatane 2003; Snyman 2006) probably occur in O. bentonii and likely help stabilize the dunes. In the foredunes, plants grow above the high tide mark of the Perigean spring tides. They face salt spray, wind-blown sand, and storms year-round.

Some plants of O. bentonii were infested with armored scale insects, but no plants were observed with signs of cactus moth, soft scale, or cactus weevils.Small ants, flies, beetles, bees, and Lepidopterans visited the plants, the latter three especially during bloom. It seems likely that the species is important to these insects.

In several locations, O. bentonii plants had black lesions (ca. 2–3 mm in diameter) on cladodes that coalesced to cover much of the surface, possibly caused by one or more of the fungi reported to affect O. ficus-indica (ChavarrÍa-Cervera et al. 2024). The blotches were dry and did not develop soft rot. Large plants were occasionally observed to have dieback in their centers. A similar dissolution of the plant centers was mentioned by Griffiths (1911) in cultivated plants. The precise cause was unclear to him.

Flowering in O. bentonii was observed from late April to early July. The greatest bloom was in late May to early June, and a few flowers were noted in early fall. Ripe fruit was observed beginning in July. Multiple cladodes at the Texas Point National Wildlife Refuge bore ripe fruits adjacent to aborted fruits. Aborted fruits also occurred on plants at Seadrift, Texas. However, the aborted fruits were of different shapes and colors at the two locations (Fig. 3; Fig. 6). Possibly the fruit failures were due to lack of pollination or larval insect damage to developing ovaries as reported for other Opuntias (Miller et al. 2009; Piña et al. 2010). Overt evidence of herbivory was not observed though some fruits showed damage indicative of small mammal or bird frugivory.

Opuntia bentonii was reported to be a possible component of the pest-pear invasion of Australia that devastated millions of square kilometers of agricultural land in the late Nineteenth and early Twentieth centuries (Alexander 1927). However, it is unclear if the references are actually to O. bentonii, O. anahuacensis, O. stricta, or some other species because the identification of Opuntia was imprecise at that time in Australia (Johnston & Tryon 1914). Therefore, the potential of O. bentonii as a weedy species is unknown. However, viable pieces of O. bentonii have been observed floating in the ocean surf and at least temporarily rooting among washed-up debris from Biloxi, Mississippi to Galveston, Texas. Thus, O. bentonii may be dispersed by maritime means as has been proposed for other Opuntias (Majure et al. 2007).