Caperonia itapevae Külkamp, 2024

Külkamp, Josimar, Valduga, Eduardo & Iganci, João R. V., 2024, A new endangered species of Caperonia (Acalyphoideae, Euphorbiaceae) from South Brazil, with morphological and phylogenetic support, Phytotaxa 633 (1), pp. 29-40 : 32-36

Caperonia itapevae Külkamp , sp. nov. ( Fig. 2 )

Type:— BRAZIL. Rio Grande do Sul: Torres, Parque Estadual de Itapeva, 29°22’55.7”S 49°45’30.2”W, ca. 5 m, 08 May 2017, E. Valduga 788 (holotype RB 01456010!, isotypes ECT!, ICN!, K!, MBM!, NY!, PEL!, SPF!, UPCB!).

Diagnosis: — Caperonia itapevae is recognized by its monoecious reproductive system, its habit (perennial subshrub with woody subterranean structure), presence of prickles with dilated base, leaves with petiole up to 0.8 mm long, leaf margin with 5–15 teeth, presence of 1–2 pistillate flowers per inflorescence, staminate flowers with heteromorphic petals and unlobed staminal column at the apex. The new species is similar to C. heteropetala by the presence of prickles with dilated proximal portion, heteromorphic petals and staminal column unlobed at the apex. However, C. heteropetala is distinguished as herb or subshrub without a woody subterranean structure, petioles 1–9 mm long, and pistillate inflorescences with up to 8 pistillate flowers. Caperonia itapevae is also similar to C. linearifolia by the presence of a woody subterranean system, short petioles and leaves with pennate veins. Caperonia linearifolia is distinguished by its dioecy, filiform prickles with undilated base, leaf margin with 16–25 teeth, homomorphic staminate petals and staminal column with 3-lobed apex.

Description:—Subshrub, ca. 1 m tall, monoecious; woody subterranean structure present, internodes 1.8–12 cm long, with prickles 0.7–1.5 mm long, simple and glandular trichomes. Stipules 2–2.5 × 1–1.2 mm, green, ovate, with simple trichomes on both surfaces. Leaves: petiole absent to 0.8 mm long, with erect prickles; blade 3–10.5 × 2.7–4.1 cm, ovate to elliptic, base truncate, acute to revolute apex, penninerved, with 3–8 craspedodromous secondary veins, prickles with dilated base on veins of the abaxial surface, margin with 5–15 teeth; trichomes simple and glandular on both surfaces. Inflorescences unisexual, 7.7–15.1 cm long; axis with simple and glandular trichomes; bracts 1.5–2 × 1–1.5 mm, ovate, simple trichomes on the abaxial surface and glabrous on the adaxial surface; staminate flowers 18–26, pedicel ca. 1 mm long, basally articulated, with simple and glandular trichomes, buds ovate; sepals 5, 1.9–2.1 × 1.4–1.5 mm, homomorphic, ovate, fused at the base, apex acute, margin entire, pubescent on both surfaces; petals 5, heteromorphic, 3 of them oblong to obovate, 1.8–2 × 1.4–1.9 mm and 2 linear to elliptic, ca. 1 × 0.3–0.4 mm, adnate to the staminal column, glabrous, white; stamens 10, distributed in two whorls, staminal column ca. 1.8 mm long, glabrous, yellow, apex globose; pistillate flowers 1–2, pedicel 1–1.6 mm long, non-articulated; sepals 5, 2.5–3.1 × 1.8–2.1 mm, homomorphic, elliptic, base fused to the receptacle, apex acute, margin entire, ciliate, simple trichomes on both surfaces, green; petals 5, 2.1–2.5 × 1.4–1.9 mm, homomorphic, obovate to elliptic, apiculate apex, simple trichomes on abaxial surface, white, caducous with evident scar; ovary globose, muricate, with simple and glandular trichomes; styles 1–1.5 mm long, 30–36 laciniate, glabrous, yellow. Mature fruits not observed.

Distribution and habitat:— Caperonia itapevae is only known from its type collection in the northeast of Rio Grande do Sul state ( Fig. 3 ), in a low elevation area (ca. 5 m). Like all other species in the genus, C. itapevae grows in open environments associated with wetlands, in this case, small lakes alternating between being temporarily full and dry during the year. According to the Parque Estadual de Itapeva management plan ( SEMA 2006), the vegetation formations found in the protected area are classified as coastal scrubs and dense ombrophylous forest, both under the Atlantic Forest domain ( IBGE 2004). Caperonia itapevae was collected in a wet coastal scrub area characterized by small depressions with sandy soils and herbaceous to shrubby vegetation.

Preliminary conservation status:— Caperonia itapevae is known from a single record inside the Parque Estadual de Itapeva. According to IUCN (2023) criteria, the assessment of extinction risk based on using EOO is possible when there are sufficient records for the formation of a polygon, i.e., three or more. So, based in EOO, Caperonia itapevae presents Deficient Data (DD). However, the new species is known from one unique record, presents only one location embracing all the known population of the species up to now (4 km ²), and the region suffers high anthropogenic pressure causing severe environment fragmentation, with continuous loss of occurrence area and decline in habitat quality. Based on the above threats and the geographic criteria, we propose that C. itapevae is a critically endangered species (CR) based on B2ab (i,ii,iii) [B2 - Geographic distribution with an occupancy area less than 10 km 2; a. Severe habitat fragmentation and known presence of threatened situation; b. Observed continuous decline: (i) extent of occurrence; (ii) area of occupancy; (iii) habitat quality].

Although it occurs inside a protected area, anthropic pressure, mainly caused by the civil construction sector, is the main threat to C. itapevae and all other species present in most of the remaining natural areas along the coast of the state of Rio Grande do Sul. The civil construction sector is experiencing disorderly growth, which is threatening regional biological conservation. Northeast Rio Grande do Sul represents a transitional ecotone between the Atlantic

Forest and Pampa grasslands, and has long been recognized by harboring an exclusive flora, with many endemic taxa. Rambo (1950) referred to this region with the expression “Porta de Torres”, a corridor of migration for tropical taxa toward the subtropics. Recent new species discovered within this region highlight the knowledge gaps and the need for further floristic surveys. In addition to C. itapevae , the rare species Eriocaulon itapevense Alff & Stützel (in Alff et al. 2019: 200) and Chiropetalum ramboi (Allem & Irgang 1976: 285) Radcliffe-Smith & Govaerts (1997: 478) were recently described from the same protected area.

Caperonia itapevae is extremely rare; following the first record (Valduga 788), new expeditions were carried out in the same area, but no new specimens were found. New expeditions will be conducted in the region to register new occurrence records for the species. We also highlight the importance of including C. itapevae on the official red list of threatened species in Brazil and developing conservation strategies for species in the region.

Phenology: —Flowering and fruiting observed only in May.

Etymology: —The specific epithet refers to Parque Estadual de Itapeva, in the indigenous Guarani language, Ita = rock, and peba = flat. Itapeva was the name given to the flat rock formation currently known as Pedra do Itapeva, in the protected area. Here, we use the specific epithet as a reference to the Parque Estadual de Itapeva and in honor of the Guarani indigenous people who occupied this region for thousands of years and majestically lived in harmony with the natural environment.

Notes:—The original collection of Valduga 788 was first determined as C. linearifolia , an endemic species of the Pampa. However, when this sample was included in the phylogenetic study by Külkamp et al. (2023), this specimen (Valduga 788) emerged closely related to C. heteropetala , a species occurring in the coastal region of southeastern and northeastern Brazil. While studying collections of Caperonia from southern and southeastern Brazilian coastal areas, we found that the genus is underrepresented in herbarium collections, which makes it difficult to understand the geographic disjunction observed between the two evolutionarily and morphologically similar specimens. Therefore, we compared the Valduga 788 sample with geographically closely related species ( C. cordata , C. hystrix , and C. linearifolia ) and with the phylogenetically closest species ( C. heteropetala ). Based on exhaustive morphologic studies, we concluded that the specimen consisted of a new taxon ( C. itapevae ). The new species and C. heteropetala share morphological characters such as prickles with dilated bases ( Fig. 2C ), heteromorphic petals of staminate flowers ( Fig. 1 & 2F ) and a staminal column with globose unlobed apex ( Fig. 2G ). The staminate petals and the staminal column apex have demonstrated to be important characters to delimit species in Caperonia , because they have little interspecific variation ( Külkamp et al. 2021). Another important character that differentiates these taxa is the presence of a subterraneous woody structure, present in C. itapevae and absent in C. heteropetala . This subterraneous woody structure is also present in a few Caperonia species from the Pampa grasslands ( C. cordata , C. linearifolia ). The taxa presenting subterraneous woody structure do not occur in sites with permanent water, but in the vicinity of these areas. In contrast, most known species in Caperonia do not have this structure and can occur directly in contact with water. The main morphological differences between Caperonia species registered in the state of Rio Grande do Sul (geographically close), are presented in Table 1. Caperonia is poorly studied in Rio Grande do Sul state and collections are scarce, which makes it difficult to understand the morphological and distribution range of some taxa (Külkamp 2023, SpeciesLink 2023). The same is identified in Santa Catarina state, where only two records are known, one of C. hystrix dated 1946 (the northernmost known record of the species) and one of C. palustris from 2016 (SpeciesLink 2023). These few records in Rio Grande do Sul and Santa Catarina states may reflect the rarity of Caperonia in southern Brazil, or a gap in collections for this area.

Table 1. Main morphological differences between Caperonia species registered in Rio Grande do Sul state, Brazil.

Caperonia presents floating seeds that survive for long periods and germinate in water, which may explain the geographic disjunction between the two closely related taxa ( C. itapevae and C. heteropetala ) that recently diverged (3 Mya according to Külkamp et al. in prep.). A biogeographic hypothesis postulated by Rambo (1950) suggests that “the Torres region is a corridor of migration for tropical taxa toward the subtropics” and may explain this close relationship of C. itapevae with the tropical C. heteropetala . According to Lima & Parise (2020), coastal vegetation in southern Brazil suffered a significant interference from marine transgressions after the last glacial maximum. We hypothesized that the common ancestor of C. itapevae and C. heteropetala was widely distributed from southeastern to southern Brazil and with sea level oscillations, the populations were isolated and underwent allopatric evolution. Further studies will focus on historical biogeography with the aim of understanding geographical disjunctions present in Caperonia , also including the disjunction between African and New World taxa.

Here we do not formally classify Caperonia itapevae in section Aculeolatae , since this section does not constitute a single clade ( Fig. 1 ). Further studies with a wider phylogenetic sampling will be carried out to propose an accurate infrageneric classification for the genus.

Figures

FIGURE 1. Majority rule consensus tree of Caperonia (Euphorbiaceae) and related taxa based on the combined four markers (cpDNA [trnLF, trnTL] and nDNA [ETS, ITS]) obtained through Bayesian inference. Bayesian posterior probabilities (PPs) are indicated on each branch. Photos by JK.

FIGURE 2. Caperonia itapevae. A. Coastal scrub in the Parque Estadual de Itapeva. B. Habit of C. itapevae. C. Prickles on the stem of C. itapevae. D. Abaxial and adaxial leaf surface. E. Pistillate flower, top view, showing yellow styles. F. Staminate flower showing heteromorphic petals. G. Stamens adherent to the staminal column with unlobed apex. H. Larger petal of the staminate flower. I. Smaller petal of the staminate flower with proportional size. J. Petal of the pistillate flower. K. Sepals of the pistillate flower united at the base. Brown spots are scars from the insertion of the petals. Figure based on type specimen (Valduga 788). Photos by the authors.

FIGURE 3. Distribution map of Caperonia itapevae, restricted to Parque Estadual de Itapeva, state of Rio Grande do Sul, Brazil.