First record of alien naturalized populations of the crop Cucurbita moschata (Cucurbitaceae) in Spain, with remarks on typification status

Description and typification notes

Cucurbita moschata Duchesne, Essai Hist. Nat. Courges: 7 (1786)

Gymnopetalum calyculatum Miq. in Fl. Ned. Ind., Eerste Bijv. (2): 332 (1861)

Lectotypus (designated here): Label 1: “Gymnopetalum ? calyculatum Mq, Banka, (J. Amand)”; Label 2: A. Cogniaux Monogr. Cucurb. H “Cucurbita moschata Duch.” (probably Cogniaux’s handwriting); U (U0001457!).

An annual species characterized by softly hairy, non- to shallowly 3-5 lobed leaves, 15-30 ´ 20-40 cm, without or with whitish blotches; tendrils bifids or trifids; sepals free, mostly linear, but sometimes lanceolate together with flowers with broadened apices (Fig. 1); corolla yellow-orange, 8-12 cm long; fruiting peduncle 5-ribbed thickened and dilated or cylindrical, 5-10 cm long, widely flat at the fruit attachment; fruits covered by a wipeable waxy layer, dumbbell and solid green or pyriform and cream-coloured with light green longitudinal reticulate mottled stripes (usually in bands), up to 35 cm length; seeds elliptical, 8-15 ´ 4-7 mm, with a rounded marginal bulge, margin mostly with a colour shade slightly different from the surface, marginal wings developed very strongly. Most of these morphological features correspond to the main features used to distinguish it from the other domesticated species of this genus, C. ficifolia, C. maxima and C. pepo (Tab. 1).

Fig. 1 Cucurbitamoschata Duchesne. A – habit, B – flower (side view), C – flower (front view), D – mature fruit (drawing by Joaquín Moreno).

Regarding the protologue of C. moschata, Paris (2000) already stated that this name was validly published by Duchesne (1786) in the Essai sur l’Historie Naturelle des Courges, and hence, Duchesne was solely responsibility for the authority. On the GBIF database (www.gbif.org), three different entries were found related to the type specimens of the name C. moschata. Firstly, the mention of the type specimen of this name held at the Missouri Botanical Garden (MO1722018) should be considered a mistake, since no voucher is apparently held at MO only at F, LPB and NY (Teisher, pers. comm.). The voucher information corresponds to the collection of T.J. Killien (nº 1267) made in Bolivia during 1989, but no publication has been found about this likely typification and, at least, the voucher at F (barcode F2013050!; Bolivia, Santa Cruz, Cordillera, Tatarenda, 30 km S of Rio Grande on road to Camiri, 19º08’S 63º15’W, 700 m, first range of Andes with semi-deciduous forest and slash and burn agriculture, soils generally sandy, Tim Killeen 1267, 16 Oct 1985) does not bear any identification of type material. Therefore, the typification of the name C. moschata is still an uncompleted task, as with many other cultivated species, which were initially described without any direct reference to a herbarium voucher or collection. The second mention concerns the accepted synonym Gymnopetalum calyculatum Miq., the description of which (Miquel 1860) was based on material collected from Bangka by J. Amann (pseudonym of W.S. Kurz, seeVan Steenis-Kruseman and Van Steenis 1950). De Wilde and Duyfjes (2010) designated a voucher kept at the herbarium U (barcode U0001457!) as the holotype. However, the use of the term holotype by these authors cannot be adequate, as Miquel (1860) only referred to Amann’s gathering activity but not to a specific sheet. Hence, there is no certainty that other duplicate material was not used to prepare the description of this name by the original author (ICN, Art. 9.1), though no additional specimens were found at NL, L, U and WAG (M. Scherrenberg, pers. comm.). Therefore, the voucher U0001457 should be considered as the lectotype of the name G. calyculatum. Finally, the third reference corresponds to a specimen of the name C. sulcata Blanco kept at L (barcode L0585284!; Cucurbita sulcata, Merrill, Species Blancoanae nº 152, labelled as neotype by J.K. Veldkamp 2/03, labelled as C. moschata by W.J.J.O de Wilde & Duyfjes, 2011), which was selected as neotype by Veldkamp on the specimen; however, Veldkamp never published his designation, which is thus ineffective. The name C. sulcata is currently considered a synonym of the species C. maxima, but the identification of this particular voucher was corrected to C. moschata on the specimen by De Wilde and Duyfjes. To avoid the effect of destabilizing the nomenclature of the name C. sulcata, an effective typification should be based on a specimen whose identification corresponds to the original description (Blanco 1837).

Habitat and populations

The populations of C. moschata were found growing in the central part of the course of the River Vinalopó (named the Middle Vinalopó district), which runs across the inner central part of Alicante Province (Spain), crossing semiarid and arid areas. At this geographical zone of the river, the watercourse is not continuous, and it can remain totally dry for long periods of time, even in excess of one year. This ecological peculiarity, added to the climatic characteristics of the area, contributes to soil salinity.

Four scattered populations, with up to 10 specimens each, of C. moschata have been discovered along five kilometres of this river basin, most of them growing clearly away from the direct influence of the main course of the water. The largest population, about 10 individuals, appeared on sandy soils on the upper part of the terrace of the river. At a distance of approximately two kilometres downstream, another well-established population with 5 individuals grew close to secondary dry channels of this river, characterized by gravel and sandy soils. The other two populations, formed by 2-3 individuals, and some isolated individuals of C. moschata were placed on the shallow area of meander scars and along the edges of the riverbed, both upstream and downstream in reference to the largest populations.

The first observations of them were noted in 2016, when only the two above-mentioned largest populations were initially identified with five and two reproductive individuals, respectively. Over the years these populations of C. moschata have developed autonomously, with increasing numbers of individuals, while new subpopulations or isolated individuals have been found far from them, being fully reproductive. Although the size of the population may be different from year to year, the annual appearance of new specimens seems to be entirely independent, based on the development of functional seeds, which seem to germinate under the ecological conditions of this area. In addition, no crops were found close to the observed populations.

The populations of C. moschata, in general, appear intermixed with wild shrubby and grassland vegetation (e.g., Atriplex halimus L., Cynodon dactylon (L.) Pers., Tamarix gallica L., together with other naturalized alien species along the river, such as Physalis peruviana L., Stenotaphrum secundatum (Walt.) Kuntze, Solanum lycopersicum L. and S. sisymbriifolium Lam. Independently of the size and location of the population, the observed individuals were fully reproductive, and well-developed mature fruits were easily found.

Climate and watercourse features

On the basis of the recent studies of José Ramón Coves (pers. comm.), the main features of the water of the River Vinalopó along the studied area are an average water temperature of about 20 °C, with an electric conductivity ranging from 2.8 to 5.9 mS cm^-1, pH 7.66 (7.3-7.8) and an average nitrate concentration of 75 mg L^-1 (25-180 mg L^-1). The weather conditions of the studied area are characterized by typically Mediterranean climate, with remarkably dry summers. The annual average rainfall is 345 mm, with maximum values in September (43 mm) and minimum in July (6 mm). The average monthly values of temperatures are always above 0 °C, January being the coldest month with minimum average temperatures of 7.7 °C whereas the maximum values were registered in both July and August (mean values of 25.1 °C and 24.9 °C, respectively). According to these rainfall and temperature data, the studied area corresponds truly to a semiarid area belonging to an inferior Mesomediterranean belt.

Naturalized specimens observed of Cucurbita moschata

Hs, Alicante: Elda, River Vinalopó, 38º27’09’’N 0º48’12’’W, 337 m, 12 Nov 2017, A. Juan AJ117 (ABH 82475). Elda, River Vinalopó, left side of the river, upper part of the terrace of the river, 38º27’06’’N 0º48’13’’W, 335 m, 20 Nov 2017, A. Juan & I. Juan AJ118 (ABH 82476). Elda, River Vinalopó, upper part of the terrace of the river, 38º27’04’’N 0º48’12’’W, 335 m, 14 Sept 2018, A. Juan, J. Moreno & A. Terrones (ABH 82477). Elda, River Vinalopó, secondary dry channel, 38º26’51’’N 0º48’13’’W, 330 m, 27 October 2018, A. Juan, J. Moreno & A. Terrones (v.v.). Elda, River Vinalopó, terrace of the river, 38º28’16’’N 0º48’15’’W, 370 m, 24 Nov 2019, A. Juan, J. Moreno & A. Terrones (v.v.).

Distribution of the Cucurbita moschata in Spain

Specific geographic references to Cucurbita moschata as crop have been reported only from the northeast of the Iberian Peninsula (Barcelona province), where it also behaves as an occasional alien growing on the margin of the river (Gómez-Bellver et al. 2019). The newly found C. moschata populations in Alicante are very distant. The populations of C. moschata found in Alicante Province have been documented since 2016 and most recently have been observed to be composed of at least 25 reproductive individuals.

Morphological aspects

The collected specimens of Cucurbita moschata show morphological features that fully fit the typical diagnostic characteristics of the species (Teppner 2004,De Wilde and Duyfjes 2010), though certain variabilities related to the leaves, sepals and fruits were detected among the studied specimens. The leaves were shallowly lobed, and either without or with whitish blotches. Most of the samples were characterized by the unique presence of linear sepals, but some specimens showed flowers with lanceolate sepals together with flowers with broadened sepals. Two types of fruits were observed: (i) dumbbell and solid green with a fruiting pedicel widely flat at the fruit attachment, and (ii) more rarely, pyriform and cream-coloured with light green longitudinally reticulated mottled stripes (usually in bands) with 5-ribbed thickened and dilated peduncles at the fruit attachment. The observed minor morphological variations are likely derived from the existence of numerous cultivars of this species, which vary greatly in fruit shape and colour (Lira 1995,Teppner 2004,De Wilde and Duyfjes 2006).

The main morphological characters distinguishing C. moschata plants or fruits from the closely related species, C. pepo and C. maxima, are basically related to the indument, leaves and fruit stalk (Lira and Rodríguez Arévalo 1999,Teppner 2004,Tab. 1). While C. moschata is a soft-haired plant with non- to shallowly lobed leaves, smoothly grooved stems and a hard, smoothly angled fruit stalk widened at the apex, C. maxima is characterized by hispid, unlobed (or slightly lobed) leaves and rounded stems, with the fruit stalk soft and rounded, not enlarged at the apex. Finally, C. pepo is typically spiculate with grooved stems and palmately lobed, often deeply cut and prickly leaves, with a hard and markedly angular fruit stalk sometimes slightly widened at the apex.

The following dichotomous key is based on Fernandes (2005) to which C. moschata was added to facilitate the plant identification:

1. Plants with short glandular hairs, generally climbing; leaves 3-5-lobed, with rounded or obtuse segments; fruit with white flesh, seeds black.….….….….….….….... C. ficifolia

– Plants hispid with short, stiff hairs, prostrate or climbing; leaves from entire to clearly lobed, with triangular segments; fruit with pale or yellow or yellow-orange flesh, seeds white or orange ...................................... 2

2. Leaves entire or slightly lobed; rounded stems; fruit stalk subcylindrical, rounded, soft ............. C. maxima

– Leaves shallowly to deeply lobed; grooved stems; fruit stalk different .................. 3

3. Plant prickly, spiculate; leaves palmate, shallowly to deeply lobed; fruit stalk notably angled, slightly broadened at attachment on the fruit apex; fruit with light-coloured yellow to orange flesh; seed margin with similar colour and texture as the surface ….….….….….….….…. C. pepo

– Plant softly hairy; leaves shallowly lobed; fruit stalk slightly angled, mostly abruptly broadened at attachment on the fruit apex; fruit with orange flesh; seed margin with a different colour and texture than the surface ...................................... C. moschata

Distribution and alien status of C. moschata and related species

The presence of C. moschata out of cultivation is quite scarce not only around the Mediterranean basin but also around the European continent. Ardenghi and Mossini (2015) have reported the presence of two non-cultivated populations in Italy, located along an irrigation canal among rice fields, together with scattered vegetable refuse. According to these authors, the populations almost certainly grow from seeds rejected as food waste, since the observed seedlings likely derived from fruits produced in previous years. In addition, occasional reports of C. moschata from northern European territories have been also indicated (Jonsell and Karlsson 2010,Verloove 2018). Jonsell and Karlsson (2010) stated the doubtful mention of this taxon in Sweden during the 1950s and no new mention is available, and, Verloove (2022) reported it on a dump in Belgium. In Spain, Gómez-Bellver et al. (2019) recently reported alien plants of C. moschata growing on the margin of the river Llobregat. Based on Richardson et al. (2000), these mentions might be considered as ephemeral casual alien plants. Contrary to these previous reports, our direct field observations yielded the lack of any vegetable crops close to this stretch of the river, including cultivated plants of C. moschata. Therefore, the existence of these non-cultivated populations of C. moschata might have originated from seeds of old discarded agricultural waste in some remote area upstream of the river, as neither farming litter nor current cultivation has been observed close to the studied area. The existence of a large number of individuals cut off from the riverbed together with their repetitive presence during several years would denote a certain population stability. Consequently, the presence of C. moschata populations along the basin of the River Vinalopó, and their subsequent propagation over the years, would be nowadays considered as autonomous and well established, and not directly bound to any current agricultural activity. Although most free-living plants of the cultivated species of Cucurbita are reported as casual offspring from nearby fields, on the basis on our observations we consider the described Alicante populations of C. moschata as the first ones to be naturalized in Spain.

Regarding closely related species (C. ficifolia, C. maxima and C. pepo), only two mentions (Barcelona and Valencia, based on herbarium specimens) were reported for C. ficifolia, growing in fields of carob trees. Conversely, the species C. pepo and C. maxima both have been largely reported for different Spanish provinces (e.g.,Serra 2007,Sanz Elorza et al. 2009, and more than 250 occurrences on GBIF), including the Balearic and the Canary Islands. Most of the observations of these three species based on the labels of vouchers and existing literature reported the presence of scarce specimens out of the crops (e.g.,Serra 2007,Gómez-Mercado 2009,Herrera and Campos 2010, among others). They were considered as casual alien plants as they typically grew in disturbed habitats near crop fields.

Ecological aspects

The existence of numerous small parcels of farmland on which are grown tomatoes, broad beans, peas, onions, and melons, among others things, basically for subsistence, is fairly extensive along the Vinalopó Valley, though they were not the main agricultural use for this territory (Juárez 2010). Nowadays, the discovered naturalized populations of C. moschata did not grow close to any pumpkin crops, and therefore, the river would be the main method of seed dispersal along the Vinalopó Valley. In fact, riparian habitats can act as ‘conveyor belts’ for propagules (Richardson et al. 2007), and they might be important corridors for seed dispersal, both for native and alien species (Pyšek and Prach 1995,Stohlgren et al. 1998). Many alien species spread along watercourses (Richardson et al. 2000), and their invasion success largely depends on their dispersal ability (Pyšek and Prach 1995). Ecological conditions also play an important role on the entrance into and stabilization of alien plant populations along watercourses (Iamonico 2021), especially for annual Cucurbita species (Lira 1995,OECD 2016). Cucurbita fruits can be buoyant in the watercourse (OECD 2016), and hence, the river would represent a potential means of long seed dispersal. Under the appropriate environmental conditions, including no severe frost, seasonably warm temperatures and well-drained soils (OECD 2016), the germination of seeds and development of offspring of C. moschata would be favoured, even in the existence of relative drought. The observed climatic conditions of the studied area coincided with the ecological requirements, although the water quality of this river is slightly alkaline and saline (José Ramón Coves, pers. comm.). In fact, a high number of non-cultivated individuals of Solanum lycopersicum (Solanaceae) belonging to different cultivars, including cherry and plum tomatoes, appear clearly naturalized along the Vinalopó river channel and its terrace, comprising well-established populations without direct intervention by humans (pers. obs.). The number of individuals of S. lycopersicum is quite high and their presence is so frequent that this species already coexists with the riparian natural vegetation of the river, and the long-time permanence of these individuals would be autonomous and even might be considered as invasive. Similarly, other alien non-agricultural species, as Drosanthemum hispidum (L.) Schwanthes, Ulmus pumila L., Rumex cristatus DC.,Cotula coronopifolia L. or Datura inoxia Mill., have also been observed and their populations are easily found along the River Vinalopó (Serra 2016,Juan et al. 2019). Among them, the species D. hispidum clearly shows an invasive behaviour, being the dominant species along the studied upper fluvial terraces of the River Vinalopó and close slopes (pers. obs.).