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Veronica catenata Pennell, Pink Water-speedwell

Account Summary

Native, rare. Circumpolar temperate, but disjunctly so; introduced in C Africa and S Australia.

1934; Praeger, R.Ll.; Co Fermanagh.

June to September.

Growth form, identification and preferred habitats

Pink Water-speedwell may remain under-recorded, as not everyone in the field yet separates it from the very similar V. anagallis-aquatica (Blue Water-speedwell), although the two were recognised as distinct species over 100 years ago (Pennell 1921). These two aquatic, semi-aquatic and terrestrial, usually annual but occasionally short-lived perennial species, obviously differ in flower colour and, in addition, V. catenata has its pedicels shorter than its bracts at flowering time and they spread at right-angles after flowering. It also has narrower leaves, purple-tinged stems and fewer and more widely spaced flowers per inflorescence than V. anagallis-aquatica (An Irish Flora 1996; Burnett 1997). Having said this, the two species cannot reliably be distinguished without flower and/or fruit characters (J.H. Burnett, in: Rich & Jermy 1998). However, of vegetative characters, the most useful are the absence of basal petiolate leaves in V. catenata and the more marked, frequent, small serrations of the leaves of V. anagallis-aquatica (Burnett 1997).

When growing in more disturbed, trampled sites, V. catenata produces small plants that behave as annuals and young plants develop basal branches that grow into flowering branches, rather than prostrate or procumbent, leafy spreading stoloniferous stems, like those produced by V. anagallis-aquatica (Preston & Croft 1997; Stace et al. 2015). In more terrestrial, waterside sites, the hollow, glabrous stems, 20-30 cm long, shortly creep, root and then ascend in the same manner as V. anagallis-aquatica (Fitter 1987; Sell & Murrell 2007).

V. catenata appears to have a somewhat wider habitat range than either V. anagallis-aquatica or V. beccabunga (Brooklime), strongly preferring exposed bare mud at the margin of shallow, standing or running water, although it can also grow in much deeper water than these other species, down to 1 m deep in streams, ditches and seasonally flooded ground on the margins of water bodies. In addition, it can be found growing in flushes, on riverside rocks and in coastal sites, where it is occasionally flooded by brackish water. Having said all this, V. catenata most frequently occurs in B & I as a waterside terrestrial plant, preferably in open, disturbed ground (Burnett 1997; Stace et al. 2015).

While it can occur on fertile, moderately acidic soils, V. catenata is more frequently recorded in calcareous surroundings (Preston & Croft 1997). The established strategy of V. catenata is categorised as R/CR, meaning it is intermediate between a straight Ruderal species and a more Competitive-Ruderal one (Grime et al. 1988, 2007).

Hybrids

V. catenata does overlap from time to time with V. beccabunga and with the more closely related V. anagallis-aquatica in both its ecology and occurrence, and it is capable of forming vigorous hybrids with the latter, although these have never been discovered in Fermanagh. The hybrid occurs throughout much of temperate Europe, sometimes forming large clones in streams. The hybrids develop long, many-flowered racemes but form very few 1- to 5-seeded capsules and are most easily recognised by their high degree of sterility (S.M. Walters & D.A. Webb, in: Tutin et al. 1972; Stace et al. 2015).

Flowering reproduction

As is the case with most aquatic or semi-aquatic species, when it is submerged, V. catenata does not flower, but remains entirely vegetative. Fortunately, completely submerged plants are unusual and the species is mostly either terrestrial or emergent and therefore capable of flowering. Flowering takes place between June and August, the pink flowers with reddish veins attracting flies that pollinate them or, failing this, they self-pollinate (Fitter 1987). Capsules are borne on relatively robust pedicels (stouter than in V. anagallis-aquatica) that may thicken after pollination. The capsule is enclosed within narrowly ovate, obtuse sepals which rarely exceed the orbicular capsule which is usually broader than long (3-4 mm broad, 3-3.5 long). It is always deeply notched at the apex in mature, un-dehisced capsules (Burnett 1997).

Presumably, in common with other wetland Speedwell species, seed dispersal would mainly be by wind blowing across the open capsule, but some seed may be ingested by grazing animals and become transported internally by cattle, horses and birds, especially ducks. Other seed might very possibly be dispersed in flowing water.

There is just one estimate of seed longevity in the soil seed survey of NW Europe, which reckoned that survival in soil is short-term persistent (ie 1-5 years) (Thompson et al. 1997).

Fermanagh occurrence

As mentioned under V. anagallis-aquatica, this is a rare species in B & I apart from in the more continental region of Britain lying south of the Humber-Severn line (Preston & Croft 1997). V. catenata is certainly rare in Fermanagh, occurring on exposed mud by lakeshores and, more rarely, on sheltered shallow stretches of river-banks in just 14 tetrads scattered around the VC. Thirteen of the Fermanagh tetrads have post-1975 records. It has been found almost entirely on lowland lakeshore sites, plus just a single occurrence on the Colebrooke River.

Irish occurrence

Like these other two wetland speedwells (V. anagallis-aquatica and V. beccabunga), V. catenata has been recorded from almost all Irish VCs (Cen Cat Fl Ir 2), but of these three species it is by far the least familiar. On the evidence of the records published in the FNEI 3 and in the Flora of Co Dublin, Fermanagh appeared to have more locations for this species in the post-1975 era than anywhere else in Ireland. The New Atlas hectad map now shows that the species is rather well represented in the Irish Midlands, with numerous scattered stations elsewhere across the island, including near the N coast (A. Horsfall, in: Preston et al. 2002).

British occurrence

Locally frequent in C, E & SE England and Midland Ireland, but scattered, coastal and scarce to rare in Wales, SW & N England, Scotland and the Channel Isles (New Atlas; Sell & Murrell 2007). Over the period 1960-97, in the opinion of J.H. Burnett (1997), V. catenata did not decline in abundance in England as much as V. anagallis-aquatica did, and he raised the question, can it be that these species demonstrate cyclical changes in abundance and distribution? This is a phenomenon, he points out, that botanists have been slow to investigate.

European and world occurrence

V. catenata is widespread but thinly scattered and very probably uncommon across most of Europe from 58°N southwards and eastwards to C Europe and W Asia. It is, however, absent from Iceland and most of the Mediterranean region. The species is mapped by Hultén & Fries 1986, Map 1651) as being native in the Azores and N America, although considered introduced to C Africa (Ethiopia and Kilimandjaro) and S Australia. The fact that the same authors reckon the closely related V. anagallis-aquatica is probably not native in N America, raises a measure of doubt in the mind of the current author (RSF) that this species is indigenous in N America.

Names

The Latin specific epithet comes from the Latin 'catenatus', meaning 'linked', 'chained', or 'chain-like' (Chicheley Plowden 1972), but it is not obvious to the current author (RSF), to which plant feature this might allude.

Threats

None.