Capsicum piuranum

Overview

Capsicum piuranum is a wild pepper endemic to the Piura Department of northern Peru, where it grows in cool, misty mountain forests at roughly 2,300–2,860 metres above sea level. It is not a domesticated chilli variety. Botanists recognise it as a separate species within the Andean group of Capsicum, a group whose members often have long flower stalks, unusual flower colours and fruit that is not hot.

Its appearance combines several distinctive features: a loosely scrambling shrub usually around two metres tall, strongly unequal pairs of leaves, hanging flowers with unusually long, pure-yellow tubular bells, and a purple or greenish-purple calyx with five pointed teeth. The nearly round mature berries turn orange to orange-red and are non-pungent. Each carries many small dark seeds, and two hardened structures are embedded within the fruit wall.

Although its yellow flowers resemble those of other wild Andean peppers, the particular combination of a narrow flower tube, purple calyx, equal calyx projections and orange berries is characteristic. A 2019 DNA study placed it near C. geminifolium and C. lycianthoides, rather than with the Bolivian species that it resembles most closely in flower shape.

Scientific name

Capsicum piuranum Barboza & S.Leiva

Family

Solanaceae

Native range

Piura, northern Peru (endemic)

Evolutionary group

Andean clade

Growth habit

Scrambling shrub, usually 2–2.2 m

Reference specimen

T. Mione 812, collected 22 March 2011

First described

16 January 2019

Flower

Pure yellow, tubular-bell-shaped

Calyx

Purple to greenish purple, five teeth

Ripe fruit

Orange to red; 9–12 mm

Pungency

Non-pungent

Seeds

Dark brown, approximately 50–80

Elevation

Approximately 2,300–2,860 m

Chromosomes

2n = 26

Conservation

Preliminary Critically Endangered (2022)

Discovery & naming

The scientific history of Capsicum piuranum is unusually recent. Its defining specimen was collected on 22 March 2011 by botanist Thomas Mione, who recorded the plant beside a road and a stream in Huancabamba Province, Piura. The collection, Mione 812, contained both flowers and fruit, providing the evidence needed to describe its reproductive structures in detail. The published locality was at 2,311–2,459 metres elevation, in the mountainous interior of the department.

The main reference specimen, or holotype, is held at the CORD herbarium in Córdoba, Argentina, accession CORD-00006936. A duplicate, called an isotype, is held at the New York Botanical Garden under NY-03231447. This specimen trail is important because it ties the name to a real wild population, including its flower and fruit characters, rather than to an uncertain horticultural label.

Additional collections expanded the botanical picture. In November 2015, M. Cueva and colleagues collected flowering and fruiting specimens in Bosque Mijal, near Chalaco in Morropón Province. During April and May 2017, collections around the Canchaque–Huancabamba road and the ascent towards Cuello del Indio helped researchers document living plants, take photographs, examine fruit interiors and obtain material for genetic work. Those observations also confirmed that the species was not just an unusual individual from the 2011 collection.

On 16 January 2019, Gloria E. Barboza, Carolina Carrizo García, Segundo Leiva González, Marisel Scaldaferro and Ximena Reyes published the paper Four new species of Capsicum (Solanaceae) from the tropical Andes and an update on the phylogeny of the genus in PLOS ONE. It introduced four new wild peppers: C. benoistii, C. longifolium, C. neei and C. piuranum. The name of the last was authored by Barboza and Segundo Leiva González.

The epithet piuranum refers directly to Piura, the Peruvian department where the plant was found. It is a geographic name reflecting the species' exceptionally limited documented range. The later 2022 monograph of the whole genus retained C. piuranum as a distinct species, placed it as species 35 in its treatment and added updated comparisons with other Andean peppers.

Plant & foliage

The plant is a densely branching, scrambling shrub, often around 2–2.2 metres tall, sometimes approaching three metres. Its thin, flexible branches lean or thread through other forest plants, rather than forming the compact upright crown familiar in garden chillies. Younger stems are green, shiny, smooth and lightly grooved. With age the bark becomes greenish-brown to dark brown; the original description records no visible lenticels, the small pores that appear on the stems of many shrubs.

One of its clearest features is the paired foliage. The leaves frequently emerge as two very different sizes at the same branching point, which botanists call anisophylly. The larger leaf is typically 12–17.7 cm long, sometimes only about 8 cm, and roughly 2.5–4.5 cm wide. It is usually elliptical, with a narrow, gradually tapering pointed tip and smooth margins. The base is often unequal on its two sides and narrows towards the leaf stalk.

The smaller companion is much shorter, normally 2.5–4.5 cm long and 1.5–2.6 cm wide, with a more oval outline and a blunt or slightly pointed tip. Its leaf stalk is commonly only 2–5 mm long. The larger leaf has seven to nine major side veins on either side of its central vein, while the smaller partner typically has three to four. This asymmetry is especially obvious on a branch carrying fruit, where several pairs can be seen together.

The leaf blades are thin and flexible rather than leathery. Their upper surfaces are dark green and glossy, with lighter, duller undersides. They are mostly hairless but may carry sparse, simple hairs, especially along major veins or edges. These hairs are recorded at approximately 0.5–1.2 mm long. The larger leaf stalks are sometimes slightly winged where the leaf base runs down onto them.

The 2019 description combines the foliage and branching details into a picture of a forest shrub adapted to sheltered, moist environments. It is not described as a true vine with tendrils: its growth is better understood as scrambling through nearby vegetation, with branches supported by the surrounding undergrowth. The striking contrast between the long main leaves and their short companions provides a useful field clue even when there are no flowers.

Flowers & calyx

The flowers are among the most distinctive of any Andean wild pepper. They develop singly or in groups of up to three from the leaf axils, hanging on slender, slightly curved 19–26 mm stalks. The stalks do not make a sharp bend immediately below the blossom. Flower buds are oval and pale yellow; opening flowers become uniformly yellow rather than having the purple-spotted centre seen in several other species.

Each corolla measures approximately 14.5–17 mm long and 12–17 mm across. Its shape is tubular-bell-shaped: a relatively long, narrow tube, about 11–12 mm, opens into five broad, short lobes. The lobes are normally upright or spreading slightly, not strongly folded backwards. Their tips have very small nipple-like surface cells that are visible under magnification. This structure makes the flower look rather like a little hanging golden lantern, unlike the broad white star of many domesticated peppers.

Directly behind the yellow flower is an unusually vivid structure: the calyx. It is a short, thick, cup-shaped base, usually purple or greenish purple and approximately 1.5–2.6 mm long. Around its edge stand five fleshy, pointed projections, normally 2.5–3 mm long, although smaller examples occur. They are roughly equal in size and held upright while the flower is open. The purple base contrasting with the pure-yellow corolla is one of the best features for recognising C. piuranum in photographs.

Inside the flower are five stamens with greenish-white filaments about 3–5 mm long and pale, yellowish-white anthers about 2–2.5 mm long. The white ovary is small and rounded; a narrow style approximately 7.5–8 mm long rises to a green, somewhat two-lobed stigma. The researchers recorded these tiny structures from both fresh and preserved material, because details of the corolla tube, anthers and calyx help separate similar-looking wild species.

Flower shape is not merely decorative here. A combination of five equal calyx teeth, a narrow yellow flower tube, erect lobes, long pendent stalks and mostly smooth leaves makes C. piuranum identifiable within a group that includes several superficially similar yellow-flowered peppers. The calyx changes as the fruit develops, turning its pointed teeth backward around the growing berry.

Fruit, pungency & seeds

The berries are small, nearly spherical and sometimes slightly flattened at their tops, measuring 9–12 mm across. Immature fruits may be green or nearly white. As they mature they pass into orange and orange-red, producing a bright colour against the dark green foliage. Fruits hang from stalks around 28–36 mm long, somewhat longer than the flowering stalks, and may turn away from the branch as they gain weight.

Despite the relationship with hot chillies, botanical researchers explicitly describe the ripe fruit as non-pungent. The original study used direct field observations, including tasting immature and mature berries, to establish pungency. That is a species-level botanical description, not a formal Scoville test; it supports treating the fruit as without the characteristic chilli heat, rather than assigning it a guessed SHU number.

One feature inside the berry is particularly unusual. The fleshy wall lacks the enlarged internal cells found in some other wild peppers, but contains two hard, pale yellowish-white stone cells. These are small hardened structures embedded in the fruit tissue, not extra seeds. One is visible in a cross-section of the published photographic plate. The researchers used both the presence of these structures and the shape of the fruit as identification characters.

The calyx remains attached at the base of the ripening berry. Its five pointed appendages, which stood upright behind the flower, extend to roughly 5–6.1 mm in fruit and curve backwards. The base itself stays quite small, around 4 mm across, rather than swelling into a large enclosing cup. This changing calyx posture gives the fruit a different outline from that seen at the flowering stage.

A single berry can hold around 50–80 seeds, an impressive number for a fruit barely more than a centimetre wide. The seeds measure approximately 2–2.2 mm long and around 2.5 mm wide, and are described as somewhat compressed, kidney-shaped to broadly wedge-shaped. Their colour is dark brown to nearly black. Under magnification, the seed coat has a distinctive net-like surface pattern formed by polygonal cells.

The fruit and seed anatomy help confirm the species even when flower colours have faded in a herbarium specimen. A small orange, non-hot berry with many dark seeds and two stone cells is markedly different from the larger, pungent red fruit and pale seeds of some other yellow-flowered wild peppers. It is this full set of features, not fruit colour by itself, that botanists use to identify C. piuranum.

Range & habitat

Capsicum piuranum is recorded only from Piura in the northern Peruvian Andes. This is an important detail: while several other Andean peppers extend into Ecuador, Colombia or Bolivia, the published records of this species are limited to a small highland area within Peru. Kew's Plants of the World Online also accepts the species and lists its native range as northwestern Peru.

The recorded elevation span is approximately 2,300–2,860 metres. Its natural setting is misty, montane rain forest, often with cool air, dependable moisture and rich soils. Plants have been documented along forest edges, roadside margins and the banks of small streams. These places allow some light into the vegetation while retaining humidity from the surrounding forest.

The 2019 authors described plants growing with other mountain-forest species, including Solanum, Streptosolen jamesonii, Begonia, Otholobium, Aphelandra and Juglans. This plant community gives a clearer picture of its home than a simple country label: the species belongs to the mixed shrub and understorey vegetation of humid Andean slopes, not to dry coastal farmland or lowland tropical forest.

Its recorded localities include the Canchaque–Huancabamba road and Cuello del Indio area in Huancabamba Province, and Bosque Mijal near Chalaco in Morropón Province. The original scientific paper maps its known occurrences; the later monograph provides an updated distribution figure alongside C. pereirae. These herbarium-backed points represent documented occurrences, not evidence that the species occupies every forest patch between them.

Botanical specimens record flowering from November through May, with the strongest fruiting records around March to May. That timing reflects the seasons observed in Piura; it is not a fixed timetable that can be applied to plants grown elsewhere. The published collection dates show that flowers and fruits can be present together, allowing researchers to match a distinctive yellow blossom to its orange berry.

For a species occurring at this elevation, the forest's humidity and streamside cover are important parts of its documented environment. The published records establish a plant of mountain edges and watercourses; they do not support treating it as a commonly cultivated garden pepper or assuming it will behave like a lowland tropical Capsicum.

Field collections & research

The 2011 specimen provides the formal starting point of the species' scientific name. It was collected with both flowers and berries beside a road and stream in Huancabamba Province. The collection's careful dating, locality information and preserved fruit allow later researchers to check whether newly discovered plants belong to the same species.

Collections in Bosque Mijal in 2015 expanded the documented localities to Morropón Province. The specimens were taken on 1 November by M. Cueva and colleagues, with collection numbers 2655–2658. These records are significant because they show that the species was observed outside the immediate area of the type collection while remaining confined to the Piura mountains.

During fieldwork in May 2017, Barboza and Leiva González collected specimens 4841 and 4842 along the Canchaque–Huancabamba road at approximately 2,341–2,346 metres. Their living material formed the basis of detailed photographs showing the same branch with leaf pairs, flowers, young fruit and mature berries. It also supplied material for the chromosome study published in 2019. Other 2017 collections near Abra Cruz Blanca reached elevations of about 2,860 metres.

These field observations were combined with specimens held in botanical collections and analysis of microscopic flower and fruit parts. The work was unusually complete for a newly described wild pepper: the original publication included a full species drawing, a photographic series, a distribution map, chromosome images and DNA-based comparisons. That combined evidence made it possible to separate C. piuranum from similar species without relying only on the colour of its flowers.

Genetics & evolutionary relationships

The 2019 research counted 26 chromosomes (2n = 26) in Capsicum piuranum, using actively dividing cells from germinated seeds of the 2017 research collection. This is the same chromosome count reported for several members of the Andean group, including C. longifolium, C. lycianthoides and C. rhomboideum. It differs from the 24 chromosomes commonly reported in several familiar domesticated pepper lineages.

The researchers arranged the chromosomes into nine pairs with central centromeres, three pairs with slightly off-centre centromeres, and one pair with a more strongly off-centre centromere. In conventional notation, that is 9 m + 3 sm + 1 st. One pair also carries a small satellite region associated with ribosomal DNA. Special staining revealed relatively little dense chromosome material, a pattern very similar to that recorded in C. longifolium.

DNA analysis used several markers from both the chloroplast and nuclear genome to compare the newly described species with other wild peppers. The result placed C. piuranum securely in the Andean clade. Within that group it was recovered as the close relative, or sister lineage, of an assemblage containing C. lycianthoides and C. geminifolium.

This is an interesting result because the plant's long, bell-shaped yellow flowers initially make it look rather like C. caballeroi, a species found far away in the Bolivian Yungas. Similar-looking flowers do not necessarily indicate the closest relationship. The chromosome and DNA results instead connect C. piuranum with wild peppers of the northern Andes.

Its importance is therefore broader than its rarity. Each newly documented Andean species helps researchers understand the diversity and evolutionary history of Capsicum beyond the familiar crop lines. C. piuranum contributes an unusual combination of non-pungent fruit, dark seeds, a purple calyx and a distinct 26-chromosome pattern to that wider picture.

Identification & lookalikes

The most immediately similar species in flower is Capsicum caballeroi of Bolivia. Both have yellow bell-shaped corollas, but their calyces are very different. C. piuranum has a purple or greenish-purple calyx with five roughly equal, upright projections, while C. caballeroi has a green calyx with ten unequal projections. The yellow flower lobes of C. piuranum stand outward or upright, whereas those of C. caballeroi bend backwards more strongly.

The ripe fruit makes the distinction even clearer. C. piuranum produces small orange-to-red, non-pungent berries with two stone cells and dark seeds. C. caballeroi produces generally larger, bright-red pungent berries, without those stone cells and with larger, pale seeds. The original paper drew on these combined differences rather than treating similar flowers as evidence that the plants were the same species.

Capsicum geminifolium can grow in the same broad region. Its flowers may also be yellow, but they are generally wider and funnel-shaped, often with purple or maroon spots inside. The calyx projections are typically longer and more variable in number and posture, and the plant is usually hairier. C. piuranum has more or less smooth glossy leaves, a relatively narrow floral tube, upright calyx teeth and an unspotted yellow corolla.

Another local lookalike is Capsicum rhomboideum. That species often has more flowers grouped at a leaf joint, smaller bell-like flowers and bright-red to dark burgundy berries. Its leaves are more broadly oval or diamond-shaped. By contrast, C. piuranum generally has one to three flowers per axil, noticeably longer and narrower yellow bells, long elliptical major leaves and more orange-coloured mature fruit.

For identification, the best combination is unequal leaf pairs, a pure-yellow corolla about 15–17 mm long, a purple five-toothed calyx, pendent stalks, orange non-hot fruit and dark seeds. Fruit colour or leaf shape on their own can be misleading among the many unusual wild peppers of the Andes.

Conservation

Capsicum piuranum has one of the narrowest documented distributions in the genus. In its 2019 original description, the researchers proposed Critically Endangered (CR) under IUCN assessment criteria, based on its restricted distribution and very small populations. The study calculated an extent of occurrence of 10.195 km² and an area of occupancy of 8 km², with only three known locations considered in the assessment.

The 2022 monograph retained a preliminary Critically Endangered assessment, specifically citing criterion C2a(i). It described a total population estimated at fewer than 250 mature individuals, with fewer than 50 in each subpopulation and an inferred continuing decline in mature individuals. These figures are part of the authors' published botanical assessments, not a claim that an independent official IUCN listing has been confirmed.

Small, isolated groups of plants can be vulnerable when their habitat changes. In this case, the known populations occur in mountain forest, streamside vegetation and forest margins, including sites near roads. Changes to the remaining misty forest and its water supply could therefore affect a species with few recorded places to persist. The researchers' threat assessment rests on that very limited occurrence and population size rather than on any claim that the species is commercially harvested.

Preserving the remaining high-elevation forest in Piura matters for more than one plant. Such habitats contain many local species living together under cool, wet conditions; C. piuranum is part of that community. Keeping herbarium specimens, accurate locality records and field photographs also supports future surveys, allowing botanists to recognise populations and assess their condition without confusing them with more widespread yellow-flowered peppers.