Najas marina subsp. armata, Horn

Troia, Angelo, 2022, The unnoticed northward expansion of Najas marina subsp. armata (Hydrocharitaceae) in the Mediterranean area: an effect of climate change?, Willdenowia 52 (1), pp. 91-101 : 93-94

Najas marina subsp. armata in Sicily

Although Najas marina subsp. armata was not reported from Sicily in the checklists and floras of Lojacono-Pojero (1908–1909), Uotila (2009), Pignatti & al. (2017) and Bartolucci & al. (2018), its presence on the island was reported in some 20 th century works, namely Fiori (1923), Maire (1952), Horn af Rantzien (1952) and Pignatti (1982). Also Triest (1987) had some doubts: “whether subsp. armata occurs in Sicily could not be stated here”. Owing to the lack of specific reports and specimens, it can be hypothesized that these references are based on occasional casual populations (and misidentifications cannot be excluded, at least in the first case).

Even before Fiori (1923), the taxon was clearly drawn in the pre-Linnaean work of Francesco Cupani (1657– 1710), under the polynomial “ Fluvialis atrorubens, angusto brevique folio, undequaque spinis infesto ” (Cupani 1713: t. 160; Fig. 1). It can be assumed that the collection site was in Sicily, but it is impossible to know if the depicted plant was cultivated, escaped from cultivation or casual. Even though the full details are not known, this is a very interesting report, deserving further investigation, also because the period 1675–1715 has been said to denote the climax of the “Little Ice Age” in Europe (Luterbacher & al. 2001).

The oldest herbarium specimens found are dated between 2005 and 2008 (Barone & al. 2007; Galesi in Giardina & al. 2007; Sciandrello 2009; see above in Introduction). In addition to the records mentioned above, new populations were found during the present investigations (see Table 1 and Appendix), all of them in the thermomediterranean bioclimatic belt (Bazan & al. 2015).

Most of the sites where Najas marina subsp. armata occurs in Sicily ( Fig. 2 ) are reservoirs or farm ponds (Table 1), which are artificial habitats of different sizes (from 0.001 to 0.9 km 2). There are two important exceptions in coastal, natural, shallow lakes within protected areas. The first is Lago Murana, within the Reserve “Lago Preola e Gorghi Tondi”; this lake was dry for 23 years owing to reduced rainfall and illegal wells but returned to being a lake in 2005 (Andreotti 2007); in 2012 a submerged meadow with Chara sp. was present (Salvatore Pasta pers. comm.), and only in 2018 was N. marina subsp. armata found there instead of the Chara meadow (Troia & al. 2018). The second is Biviere di Gela, also a shallow lake within a reserve; N. marina subsp. armata was not reported there in 2006 (Brullo & Sciandrello 2006) but was collected there in 2008 (Minissale & Sciandrello, CAT 031869, see Appendix). In both cases, it is clear that N. marina subsp. armata recently arrived and colonized those sites.

According to the available data, the taxon in Sicily grows in permanent waters (but in Spain it was reported also in temporary waters; Cirujano & Lopez Alberca 1984).

Data for Sicilian populations seem to confirm the ecology of Najas marina subsp. armata, which according to the literature prefers waters rich in Cl−, Ca2+ and SO 2− 4 (Cirujano & Lopez Alberca 1984; Triest 1989), with conductivities ranging from 1.45 to 9 mS/cm−1 (Triest 1989). Najas marina subsp. marina seems to be different, with results showing it to be absent in waters rich in Ca2+ and HCO − but with a similar range of conductivities (Triest 3 1988, 1989, under N. marina subsp. intermedia). Najas major grows mainly in waters rich in Ca2+ and HCO − with 3 a conductivity of 0.34–1.25 mS/cm−1 (Triest 1989, under N. marina subsp. marina).

Figures

Fig. 2. Distribution of Najas marina subsp. armata in Sicily (red dots) and unique (extinct) location of N. major at Mondello (blue square). For each population, the year of first finding is shown (see also Table 1 and Appendix).