Callitriche brutia Petagna, Pedunculate Water-starwort
Account Summary
Native, scarce but locally abundant. Possible mis-identification. Mediterranean-Atlantic.
1986; McMullin, A.S.; Drummoy Lough.
May to October.
Growth forms and preferred habitats
Sometimes the terrestrial form of this annual or perennial is abundant on exposed mud of lakeshores during dry weather, but it is capable of growing in more ephemeral pools and in damp exposed ground, including beside ditches, puddles and in poached or rutted muddy ground in fields or by tracks. A floating aquatic form of this strictly calcifuge species also grows in more permanent shallow, still or slow-moving water of acid, nutrient-poor status (Preston & Croft 1997). The species is a self-pollinated annual, pollination being submerged or aerial (Lansdown 2008). The fact that it is frequently recorded in a variety of artificial man-made or disturbed habitats, such as sand- and gravel pits or rutted tracks, somewhat remote from other populations, indicates that sexual reproduction and seed dispersal are effective and sufficiently efficient to allow this to happen (Preston & Croft 1997).
C. brutia has only fairly recently been split off from C. hamulata s.l. (Intermediate Water-starwort) at species level, and it differs from that taxon by its asymmetric, notched leaf-tips and smaller fruits, which in the terrestrial form of the plant are distinctly (at least 2 mm) stalked (ie they are pedunculate). In reality, the separation of the two species is a very difficult one, especially in the field, due to considerable variation in both of them in their aquatic and, to a lesser extent, in their terrestrial growth forms. Subsequent to the Fermanagh Flora survey featuring in this website, Lansdown (2008) downgraded and reclassified C. hamulata as a variety of C. brutia. In this new Lansdown interpretation, var. hamulata appears to be more frequent in permanent, swift-flowing water, while var. brutia typically occurs in ephemeral water bodies and at the margins of lakes and streams. Also, plants from the southern part of the C. brutia species range in Europe tend to be var. brutia, with var. hamulata appearing the more frequent form in the north (Lansdown 2008).
In the Callitriche Handbook, Lansdown (2008) points out that, "C. brutia [including C. hamulata as a variety] can be distinguished from all other European Callitriche taxa by the strongly reflexed style, the remains of which are appressed to the side of the fruit, combined with the lack of a strongly ornamented exine [outer wall] on the pollen grains".
During the summer, terrestrial plants generally fruit abundantly, but non-fruiting plants, aquatic or terrestrial, often cannot be identified confidently and certainly not in the field.
Fermanagh occurrence
Field records of Pedunculate Water-starwort have been made in Fermanagh a total of 41 times in 21 tetrads (4%). Twenty-nine records were made in August and September 1986 by members of the EHS Habitat Survey Team when working around the southern portion of Upper Lough Erne (14 tetrads). Apart from this, only a further eight more remote records exist, most of which were made by RHN. The details of the latter are: swamp at Derryclawan, 2 km NNW of Lisbellaw, 30 May 1992; lakeshore at Mullaghfad, Gubbaroe Td, Lower Lough Erne, 30 October 1992; Lough Naman (B), Conagher Upper Td, 2 September 2009; Lough Formal, 19 August 2010, Lake Ecology Team, also 11 October 2010, RHN; by stream opposite old house, Tullygarry, near Meenatully Hill, 4 October 2010, RHN & HJN; gravel pit N of Derrin Mountain, 26 October 2010, RHN & HJN; and Lough A Waddy, 26 October 2010, RHN & HJN. The NI Lakes Survey made no records of this species.
As none of these records have vouchers, they are not fully acceptable as valid, but are included here and to some extent given the benefit of the doubt.
British and Irish occurrence
When it comes to considering mapped B & I distribution, C. brutia (in the Lansdown sense, including var. hamulata) equates with C. hamulata s.l. in the Preston & Croft (1997) and New Atlas sense. The map in the two latter references shows the relative abundance of C. hamulata s.l. in areas where acidic waters predominate, primarily in the N & W of both islands, and its scarcity elsewhere, ie in E England and C Ireland. There does not appear to be sufficient accurate data on C. brutia or C. hamulata s.l. to determine whether there has been any historical decline or increase (Preston & Croft 1997; R.V. Lansdown, in: Preston et al. 2002; Lansdown 2008).
European and world occurrence
C. brutia (including var. hamulata) or C. hamulata s.l. is a widespread species throughout N, W & C Europe, extending from Iceland and the Faeroes to Scandinavia southwards to the Pyrenees, Poland, the Czech Republic, N Italy, Greece and Romania. Beyond Europe, it has been recorded from Greenland, Morocco, Iran and the Caucasus. Var. brutia has been introduced to Australia and north island, New Zealand. Var. hamulata has been found to be widespread on the W coast of N America, where again, it is almost certainly an introduction (Lansdown 2008).
Callitriche hamulata Kütz. ex W.D.J. Koch s.s., Intermediate Water-starwort
Native, occasional and local. Suboceanic boreo-temperate.
1881; Stewart, S.A.; Carrick Lough, Dresternan Td.
June to September.
This is another taxonomically difficult species, previously regarded as a subspecies of C. intermedia and closely related to C. brutia (Pedunculate Water-starwort – see the C. brutia account on this website), itself once regarded as a variant of C. hamulata. Lansdown (2008) reversed the status of these two taxa, re-classifying C. hamulata as a variety of C. brutia!
Whatever its rank, this taxon is found in a wide variety of clear, acid, nutrient-poor waters at all levels.
Fermanagh occurrence
C. hamulata (or C. brutia var. hamulata) has been recorded in 37 Fermanagh tetrads (7%), 30 of them with post-1975 records. As the tetrad distribution map shows, this perennial appears to be thinly and widely scattered across the VC, typical habitats being lakes, muddy pools, streams and bog drains. In shallower, more temporary water bodies, the species (or variety) is very probably forced to behave as an annual. In contrast to the situation with C. brutia, in the Fermanagh Flora Database 29 of the 51 records of C. hamulata s.s. were located by the 1988-91 NI Lakes Survey. It is important to recognise and emphasise that knowledge of Callitriche species in Fermanagh and elsewhere is very incomplete and that the present details are only given for the guidance of future recording.
One of the best distinguishing features of this species or variety is the abruptly expanded, spanner-like tip of submerged leaves of the aquatic form of the plant (ie a broad, regular, apical notch). A very helpful set of three identification keys to this and the other species of Callitriche was published by R.V. Lansdown in the BSBI Plant Crib 1998, and now that a well-illustrated BSBI Handbook exists, covering all the Callitriche taxa in Europe (Lansdown 2008), it is hoped that future Water-starwort recording throughout B & I will be more securely founded than has previously been the case.