Nassella hyalina (Nees) Barkworth (1990: 610)

Verloove, Filip, Gonçalves Silva, Juan J. & Leliaert, Frederik, 2024, Critical notes on grasses (Poaceae) of Madeira, Portugal, Phytotaxa 670 (1), pp. 1-17 : 4-6

Nassella hyalina (Nees) Barkworth (1990: 610) ( Figure 1 )

(syn.: Stipa hyalina Nees )

Specimen examined: PORTUGAL. Funchal, Ribeira de João Gomes N of ER-118, track along river, rocky slope, etc., quite invasive but only locally, 20 April 2022, F. Verloove 14317 (BR, MADM).

This species is native from southern Brazil to northern Argentina ( Cialdella et al. 2013). Since the 1950’s it is a naturalized, troublesome weed in parts of Australia (New South Wales, Victoria; McLaren et al. 2004) where it primarily is a weed of indigenous grasslands. Climatic modelling suggests that the potential distribution of this weed in Australia is up to 900,000 hectares in areas with high rainfall zones. If this species was to become widespread, it could pose a significant threat to rangelands and grazing systems ( Humphries & Florentine 2021).

To our knowledge, Nassella hyalina is here reported for the first time as a naturalized alien in Europe and Macaronesia ( Verloove 2005a). In the past it was exceptionally recorded as an ephemeral introduction in sheep wool in e.g. Belgium and the British Isles ( Ryves et al. 1996, Verloove 2006).

In the island of Madeira, Nassella hyalina was discovered in April 2022 in the valley of the João Gomes stream, in the city of Funchal. The species is most abundant along a little-used track that leads to the stream. Locally, it forms a dense massive stand with at least 1,000 individuals. In addition, it also grows on basaltic rocks bordering the track. It appears to have been present in that locality for quite some time (it is clearly visible on Google Streetview images from June 2021 but earlier images, from the appropriate season, are unfortunately lacking). Its vector of introduction is unknown; the Botanic Garden of Funchal is nearby but the species is not known from there (pers. comm. Carlos Lobo, May 2022). Taking into account the bad reputation of several exotic stipoid grasses in climatologically similar regions (see e.g. McLaren et al. 2004), it would perhaps be useful to closely monitor this population.

Two further (alien) species of Nassella were already known from the island of Madeira, N. neesiana (Trin. & Rupr.) Barkworth and N. trichotoma (Nees) Hack. & Arechav. ( Press & Short 1994, Vieira 2002, Jardim & Sequeira 2008, Menezes de Sequeira et al. 2012, Muer et al. 2020), and four additional taxa are naturalized in the Mediterranean area ( Verloove 2005a, Andrieu & Verloove 2020). Because all of these species are potentially invasive and correctly determining their identity is important, an expanded key for their identification is presented below:

1 Lemma small, ± 2 mm long, strongly swollen and tuberculate in its upper half at maturity, terminated by an eccentric awn ca. 15–30 mm long which remains straight when dried ......................................................................................... Nassella trichotoma

1’ Lemma always longer, cylindrical to spindle-shaped, awn almost centric ...................................................................................... 2

2 Lemma ca. 3–4 mm long; crown surmounting the lemma indistinct and poorly differentiated from the body of the lemma ............ ....................................................................................................................................................................................... N. tenuissima

2’ Lemma often longer, clearly constricted below the crown ............................................................................................................... 3 3 Lemma glabrous between the veins at maturity ............................................................................................................................... 4

3’ Lemmas hairy between the veins at maturity ................................................................................................................................... 5

4 Lemma ca. 4 mm long, with corona 0.5 mm high and awn 35–40 mm long ................................................................... N. hyalina

4’ Lemma 6–10 mm long, with corona 1.5 mm high and awn 40–85 mm long ................................................................. N. neesiana

5 Glumes (8–)13–14(–17) mm long, awn included; lemma around 7(–9) mm long, slightly papillate on its surface, sparsely hairy, those on veins nearly reaching apex; small and discrete corona, barely 0.5 mm high, not constricted at base and continuous to body of lemma; awn (50–)65(–90) mm long ..................................................................................................................... N. poeppigiana

5’ Glumes very long, (18–)24–32(–35) mm long; lemma, 8–12 mm long, papillose and rough throughout, sparsely hairy in basal part, denser on veins; corona more developed, about 1 mm high and narrowed at the base; awn ≥ 90 mm long ............. N. longiglumis

Figures

FIGURE 1. Nassella hyalina in Funchal, 20 April 2022 (Photos F. Verloove).