Medicago peregrina Verloove & Gonggrijp sp. nov.

Figs 2, 3, 4

Type.

BELGIUM – Province of Liège • Goffontaine (Pepinster), River Vesdre; 50°33.88’N, 5°45.66’E; 25 Aug. 2022; Verloove F. 14585; gravelly area next to the river; a single specimen; holotype: BR [BR 0000027058572 V]; cultivated specimens grown from seed of the holotype will be deposited at P and K herbaria.

Diagnosis.

Genetically most closely related to Medicago heyniana but readily distinguished by its smooth seeds (vs rugose), smaller, hairy, blackening fruits with only two coils (vs larger, glabrous, yellow-greenish fruits with 2.5–4.5 coils), (sub) entire stipules (vs toothed), and an indumentum composed of simple, papillose hairs (vs simple, non-papillose hairs).

Description.

Annual herb, branched from the base; branches up to 28 cm long, prostrate to ascending, not rooting at the nodes; indumentum sparse to moderately dense, composed of subappressed to erect, simple, papillose hairs. Leaves trifoliolate; leaflets often folded along the midvein, which is sunken and conspicuous; leaflets ca 5 × 3 mm, obovate, with entire margins, apex retuse to emarginate and mucronulate; upper surface glabrous, lower surface hairy, especially along midrib. Stipules triangular, entire to very shallowly toothed at the base. Inflorescence consisting of a single flower, initially nearly sessile in the leaf axils; peduncle later elongating slightly, up to 6 mm long, always shorter than the subtending petiole; peduncle not aristate, but bearing a small bract ca 1 mm long, inserted 1–1.5 mm below the flower. Flowers small, ca 4.5 mm long, bright yellow. Standard ca 3 mm long, clearly exceeding the wings and keels; abaxial side suffused with pink near the apex. Wings and keels equal, ca 2 mm long. Anthers minute, 0.1–0.15 mm long. Calyx ca 3 mm long, sparsely pubescent; teeth narrowly triangular, about as long as the tube. Fruit ca 6 mm in diameter, uniformly pubescent with simple, papillose hairs; composed of two loosely appressed, flattish coils with soft walls (the second coil typically slightly smaller); coil face bearing ca 8 veins originating from the ventral suture and curving concentrically, with anastomoses before entering the lateral vein. Dorsal suture armed with two rows of slender, flexible, straight spines, widened and grooved at the base, and 2 - rooted; spines ca (0.5 –) 1–1.5 mm long, inserted almost parallel to slightly oblique to the coil face. Seeds 4–6 per coil, not separated by septa; smooth, yellowish brown, ca 1.7 × 1.1 mm.

Origin.

The native range of Medicago peregrina can only be hypothesized. However, by considering both the provenance of the imported wool and the inferred phylogenetic affinity of the species, its potential area of origin can be reasonably narrowed. Among the primary wool-exporting regions – Australia, South Africa, and South America – no native Medicago species are known to occur. These areas only host a limited number of widespread, cosmopolitan species that have become naturalized.

By contrast, the genus Medicago has its primary centre of diversity in the Caucasus, northwestern Iran, and northeastern Turkey (Badri and Ludidi 2023). Notably, several of the more recently described species of Medicago are native or even endemic to this region. The closest known genetic relative of M. peregrina is M. heyniana, a rare and narrowly distributed species confined to the eastern Mediterranean. Considering that a portion of the wool imported into the Vesdre Valley originated from the Middle East – as also evidenced by the presence of other wool aliens such as Trigonella caelesyriaca Boiss., native to parts of the Levant subregion of the Middle East – this area emerges as the most plausible native range of the newly described species.

Further support for this hypothesis comes from molecular evidence. The nuclear internal transcribed spacer (ITS) sequences place M. peregrina within a clade that includes both widely distributed species – such as M. sativa and M. polymorpha – and taxa with more geographically restricted ranges centred on the Middle East, the Caucasus, and adjacent regions. These include: M. constricta Durieu (eastern Mediterranean to Iran; all ITS sequences from Iran), M. daghestanica Rupr. ex Boiss. (Caucasus; sequence from the Northern Caucasus in Russia), M. lessingii Fisch. & C. A. Mey. ex Kar. (eastern Europe to western Siberia and Iran; sequence from Israel), M. rigiduloides (eastern Mediterranean to Central Asia; sequences from Iran), M. saxatilis M. Bieb. (southern Ukraine, Crimean Peninsula), and M. sinskiae Uljanova (northeastern Iran to southern Turkmenistan; sequences from Iran).

Additionally, sequences from more widespread species within the same clade – such as M. rigidula (L.) All. (GenBank accession numbers KX 027582, KX 027589) and M. polymorpha (MZ 356153, OK 036668) – also originate from Iran. This geographic clustering provides compelling evidence that the clade, and likely also M. peregrina, originated in the region encompassing Iran and adjacent territories, while acknowledging that some related taxa extend into the Caucasus and adjacent parts of eastern Europe.

Ecology.

Since Medicago peregrina was introduced as a contaminant in sheep wool, it is inferred that the species originally inhabited natural pastures historically grazed by sheep in its area of origin. This suggests that its ecological niche is similar to that of other species associated with traditional grazing lands.

Etymology.

The specific epithet peregrina – the feminine gender form that agrees with the gender of the generic name Medicago (see ICN Articles 23.5 and 62; Turland et al. 2025) – is derived from the Latin adjective peregrinus (masculine – peregrinus, feminine – peregrina, neuter – peregrinum), meaning “ foreigner ”, “ stranger ”, “ pilgrim ”, or “ temporary resident ”. It alludes to the species’ uncertain provenance and its presumed introduction far from its native range. The epithet also evokes a broader historical context: it has previously been applied to some alien plant species of unknown origin introduced through wool imports, so-called “ wool aliens ”. A notable example is Lepidium peregrinum Thell., described from the British Isles by Thellung (1913) and only later identified as native to Australia.

Preliminary IUCN conservation assessment.

The conservation status of Medicago peregrina is currently assessed as Data Deficient (DD) according to the IUCN Red List criteria. The species’ natural distribution, habitat preferences, and the number and size of its populations remain unknown. However, several considerations suggest that it may be rare, and possibly even extinct in parts of its potential native range.

Firstly, given the species’ introduction as a wool contaminant, it is hypothesized that M. peregrina is native to the grasslands of Iran, where largescale sheep breeding for wool production has occurred since the 19 th century. Overgrazing is a well-known threat to native flora in such pastoral systems. For example, Acacia loderi Maiden and Senna aciphylla (Benth. ex A. Gray) Randell, both native to Australia and recently also recorded as wool aliens along the Vesdre River (Verloove et al. in press), have experienced substantial population declines in their native range due to grazing pressure (Auld et al. 2015).

Secondly, significant taxonomic research has been conducted on the genus Medicago in Iran, including extensive herbarium studies (Mehregan et al. 2002), as well as detailed cytological and molecular phylogenetic work (e. g. Ghanavati et al. 2007; Ghanavati 2011; Sadeghian et al. 2014; Zareei et al. 2020; Bayat et al. 2021; Zareei et al. 2022). These investigations indicate that Medicago species are relatively well documented in surveyed parts of the country. Unless M. peregrina originates from an unsampled region of Iran, it is reasonable to suggest that it may indeed be very scarce (if not extinct) in known areas – although, given Iran’s very large size (~ 1.65 million km 2), it could still persist in poorly explored regions.

Finally, targeted field surveys throughout Iran are needed to clarify the species’ true distribution and conservation status.

Observations.

Belgium, Goffontaine (Pepinster), River Vesdre, 50°33.88’N, 5°45.66’E, 25 Aug. 2022, obs. by Filip Verloove, Sipke Gonggrijp, and Rutger Barendse, https://waarnemingen.be/observation/253272516/, https://waarnemingen.be/observation/253400528/, https://waarnemingen.be/observation/253566416/.

Notes.

The new species does not closely resemble any previously described taxon. According to the provisional infrageneric classification proposed by Small (2011), it belongs to Medicago sect. Spirocarpos Ser., subsection Spirocarpos, a morphologically heterogeneous and weakly supported group, often regarded as a “ dust bin ” taxon. Although its placement within this subsection is based on general fruit morphology, the new species exhibits several uncommon features, including an indumentum of papillose hairs.

Phylogenetic analyses based on both plastid (matK) and nuclear (GA 3 ox 1) markers consistently place M. peregrina in a clade closely related to M. heyniana, a rare and geographically restricted species currently considered the sole member of the monotypic sect. Heynianae Greuter. Medicago heyniana was originally described from the island of Karpathos in the eastern Aegean (Greuter 1970) and has since been reported from several other Greek islands (e. g. Amorgos, Anafi, Rhodos) and southwestern Turkey (Lassen 1983; Özhatay et al. 1999; Thanopoulos 2007; Kougioumoutzis et al. 2012).