Provisional distribution and habitat texts for Potamogetonaceae taxa
(by Christopher D. Preston, for Flora Nordica 12)
Groenlandia densa map

Distribution. Nem. – D confined to Jutland, NJy Nebel Sø, known only from one undated (but pre-1900) specimen, ØJy, VJy, always uncommon, recorded from most known sites in ØJy since 1970 but there are few recent records from VJy except in the Ribe area, SJy formerly widespread but with few recent records. N – Hagström cites Frederiksstad, 1883, herb. Christian. S recorded only from one locality, Hl Söndrum 1874-1881 (Georgson et al. 1997). The northernmost world localities for G. densa as a native were in Scotland, D Njy and S Hl but it is extinct in all three areas.

Habitat. Shallow water 0.1-0.5 m deep in ditches, streams, slowly flowing rivers, mill ponds and occasionally lakes (also ‘Kanalen’). Water characteristics?

1. Potamogeton natans

Distribution. Nem-NBor. – D common throughout. S common in all lowland areas where there are aquatic habitats, rare in montane districts. F common throughout, except perhaps in the northernmost provinces of EnL and InL.

Habitat. P. natans grows in standing or slowly flowing freshwater in lakes, ponds, pools in mires, marl pits, peat cuttings [‘tørvegrav’], rivers, streams, ditches and canals. More rarely, it is found in marshes and dried-out ponds and, in some areas, in more rapidly flowing lowland streams and rivers. In northern Norden it tends to become increasingly restricted to lakes, and is less frequent in rivers and streams. It is found at a range of water depths and tolerates a wide range of water chemistry, but is most frequent and luxuriant at depths of 0.5-1.5 m in oligo-mesotrophic to meso-eutrophic waters. It is most frequent on inorganic substrates, from fine-grained silt and soft mud and clay to gravel, but it may also be found on peat. Salinity – see Luther.

4. Potamogeton lucens

Distribution. Nem-MBor(-NBor?)D scattered throughout, least frequent in NJy, has declined elsewhere but still locally frequent in Sjae, where even historically there were more records than elsewhere. S occasional or even locally frequent in areas of richer soils north to SE Jmt and Mpd; further north only known from LyL Stensele (1959) (check LyL not LL) and Nb Luleå (1899). F uncommon, more frequent than elsewhere in V, U and EH in the south and Kn, Ks and the adjacent parts of OP and PeP in the north, rare in other provinces and absent both from a large area of west central Finland (where there are few lakes) and from the far north.

Habitat. A plant of larger water bodies, including lakes, rivers and larger ditches, where it usually grows in water 1-3 metres deep. In D and S it is a species of calcareous but oligotrophic or mesotrophic waters over a range of substrates (list!). It is declining in areas of intensive agriculture because of eutrophication. In F, where there is little calcareous rock, it is restricted to species-rich lakes which are naturally more nutrient-rich and less acidic than normal; in the Finnish context these would be regarded as eutrophic.

7. Potamogeton gramineus map

Distribution. Nem-NBor. – D formerly widespread throughout, now frequent only in NJy, rare elsewhere. S frequent throughout, though declining in some arteas such as the agriculurally intensive coastal fringe of Klm, where it has been lost from streams. F frequent throughout, except in EP and KP where there are few lakes.

Habitat. Shallow to moderately deep (0.1-2 m), clear water in lakes, rivers, streams and ditches; less frequent in ponds. It grows in moderately mineral-rich, oligotrophic to mesotrophic water over a range of stony, sandy, fine-grained mineral and peaty substrates. In lakes it is usually found in water less than 1 m deep; it often occurs in places where water levels fluctuate and is tolerant of short periods of desiccation. In D NJy its stronghold is now the lakes at the edge of coastal dunes. It can grow in fairly rapidly flowing streams and rivers.

10. Potamogeton polygonifolius

Distribution. Nem-BNem. Suboceanic. D frequent in Jutland, especially in the west  and in Brn (check both in AFD results), rare and declining (check) in Fyn, and perhaps extinct in north-west Sjae (last collected when?). S frequent in areas of acidic rocks from Sk to Vrm, west Vsm and Ög, rare further north and reaching its northern limit in Hls (fide Hagström, check spms LD, UPS). F long known from A, discovered more recently on the mainland where it is now known from how many sites? in V and from a single site at EK Vehkalahti.   

Habitat. A calcifuge, found in shallow, oligotrophic water which is often iron-rich and strongly peat-stained. It is most characteristically found in small, standing or slowly flowing water bodies such as streams, ditches and pools and runnels in heaths and mires. It is even recorded as a colonist of flooded depressions at the base of wind-blown trees.(better phrasing?). Somewhat shade-tolerant?

11. Potamogeton coloratus

Distribution. Nem. – D NJy, Øjy, LFM, always uncommon, and with very few post-1950 records, FyL, Sjae, formerly widespread, now very rare, having declined because of eutrophication (other reasons too? drainage? land-use changes, eg lack of peat cutting??). S formerly in four localities in southwestern Sk, Anderslöv (fide Weimarck 1963, no specimen seen), Arrie (last collected 1883 but check Tis P.s.e. 8), Bulltofta (last collected 1895) and Eskilstorp (last collected 1894), eliminated from these sites by urban development and falling water levels; Gtl frequency??.    

Habitat. Shallow, calcareous but nutrient-poor water. It is usually found over peaty substrates, rarely over ‘argillosum’. In Denmark, found in water 0.15-0.8 m deep, especially in ditches and peat cuttings in calcareous peatlands (geology? esp of Jutland sites?). The habitat of the specimens from S Sk is not known, but their morphology suggests that they grew in at least 0.3 m water. Gotland?

12. Potamogeton alpinus

Distribution. Nem-NBor. Widespead in D Jutland, Sjae and Brn, perhaps less frequent even here than formerly and now rare or absent in FyL (last collected in 1945) and LFM (last collected in 1925).  S present in all provinces except Öl and usually frequent, although rarer in agriculturally managed landscapes than elsewhere. F frequent throughout, even in areas such as EP where there are few lakes.

Habitat. Lakes, ponds, slow-flowing rivers, streams and ditches. It is tolerant of a wide range of nutrient levels. Although it is most frequent on soft, muddy or peaty substrates it can also grow in sand or sandy gravel. As a plant with rather few floating leaves, its optimum depth lies between that favoured by shallow water species such as P. gramineus and the deeper water to which P. lucens, P. perfoliatus and P. praelongus are best adapted. In F it is the only Potamogeton species found in many inland small streams and rivers, even in places where the current is fairly rapid, growing in small, dense patches with floating leaves. In these habitats it is associated with few macrophytes other than Sparganium glomeratum and S. natans. By contrast, its stands in Finnish lakes are usually less dense and plants in this habitat often lack floating leaves. 

13. Potamogeton praelongus

Distribution. Nem-NBor. – D formerly scattered throughout, though absent from Brn and the smaller islands, now rather rare. S widespread; occasional or even frequent in areas of mineral-rich lakes, perhaps under-recorded in Lappmark. F present throughout, its frequency depending solely on the availability of suitable habitats.

Habitat. This is a deep-water species, usually found at depths of at least 1 m in mesotrophic lakes, rivers which expand into lakes, other slowly flowing lowland rivers and, less frequently, in large ditches. Its optimum depth in Finnish lakes is 1.5-3 m, and it descends to 5 m (Luther 1951 – from Pedersen 1976, check!). P perhaps cites 7 m in Denmark?? It is a plant of clear, moderately mineral-rich water and is usually rooted in mineral substrates. There is often a gap between the macrophytes in the shallow water around the edges of lakes and the deeper water in which P. praelongus grows. Salinity??

15. Potamogeton perfoliatus

Distribution. Nem-NBor. – D Frequent in SJy, VJy, ØJy and Sjæ, less common elsewhere, no specimen seen from Brn (although there are 19th century literature records and P. x nitens occurs there) and the species is absent from the smaller islands. S present in all provinces except Gtl; frequent in Baltic and Bothnian coastal regions, and inland where there are suitable habitats. F frequent in all coastal areas and inland in all regions except those few areas where there are few lakes.

Habitat. Large freshwater bodies, including lakes, rivers and streams, at moderate depths (typically over 1 m, any Baagoe data?), extending into shallower water (sometimes as shallow as 10 cm) in sites which are not prone to desiccation. In the shallowest sites it does not flower, and its optimum water depth is greater than that of P. alpinus and P. gramineus but less than that of P. praelongus. It is tolerant of a range of trophic status, from oligotrophic to meso-eutrophic. It grows in salinities up to 0.7% (Pedersen – check other sources). It extends into the coastal reaches of fjords in D and is abundant along the coast all round the Gulf of Bothnia and the Gulf of Finland, growing in harbours, bays and in places where the open water is sheltered by islands. It is usually found on hard mineral substrates such as sand or gravel.

16. Potamogeton crispus

Distribution. Nem-BNem. – D widespread, uncommon in the oligotrophic, sandy areas of NJy and VJy, frequent elsewhere. S occasional or frequent in areas of nutrient-rich soils from Sk to Vg, south-east Vsm and Srm, rarer towards its northern limit in Dls, south-east Dlr and Upl and with an outlying locality in Jmt Aspås, Indalsälven. F restricted to A and a few mainland sites in V, U (one locality, at Tammisaari) and EH, reaching its northern limit at EH Kangasala; it has been discovered only recently at well-studied lakes in U and EH, suggesting that it may be spreading.

Habitat. Lakes, rivers and streams, drainage channels, ditches and man-made ponds, usually in relatively shallow water (to depths of 1(-1.5) m) in eutrophic conditions. It also occurs more rarely in calcareous but oligotrophic lakes. Its sites in mainland Finland are fairly large, open, naturally eutrophic lakes where it grows at depths of at least 1 m.

20. Potamogeton friesii

Distribution. Nem-SBor(-MBor). – D occasional at coastal and inland sites in NJy, ØJy, VJy and Sjae, rare and not recorded recently from the southerly provinces of SJy (last collected 1921), FyL (last collected 1899) and LFM (one specimen seen, 1879) and absent from Brn. S widespead but very uncommon in both coastal and inland localities north to eastern Dlr and Upl. Further north it is found at Gst Gefle is this Gävle?? if so, coastal, inland in SE Jmt (Håsjö) and along the northern edge of the Gulf of Bothnia in Nb. F in several sites in A, extending eastwards as a rare species in coastal localities in the Gulf of Finland in V, U and EK. Northwards from A there are sites on the coast of the Gulf of Bothnia at St Pori and almost continuously from KP Karleby northwards. Inland it is known from southern Finland at a few sites in V and at EH Hollola (Lake Pihlajaniemi) in the south, and in northern Finland from Ks Salla (Aatsinki), SoL Sodankylä (Jeesiöjoki) and several sites in KiL Kittilä.

Habitat. Inland, this species occurs in naturally nutrient-rich, neutral or basic waters with good water quality. Characteristic coastal sites include creeks and pools which have been cut off from the sea by land uplift but still occasionally receive salt spray or seepage, and former river channels once connected to the sea but now separated from the main water course. Salinity? At the northern end of the Gulf of Bothnia it grows in sheltered pools, small harbours and small channels cut to allow boats to reach the shore.

21. Potamogeton pusillus

Distribution. Nem-MBor. – Occurs throughout D, but uncommon and much less frequent than P. berchtoldii in Jutland and Brn, frequent in Sjae and apparently replacing P. berchtoldii completely in the southernmost islands, including LFM. S widespread in both inland and coastal sites north to SE Dlr and Upl but local or rare in all the provinces in which it occurs. Although it is probably under-recorded, it is undoubtedly much less frequent in this area and more exacting in its ecological requirements than P. berchtoldii. Further north it is restricted to the Bothnian coast with the exception of inland localities in Jmt Stugu and, north of the Gulf, Nb Överkalix. Add  other inland localities if confirmed. F along the entire coast of the Gulf of Finland and Gulf of Bothnia; very rare inland in southern Finland, in EH Asikkala, Hattula, Hollola, ES Parikkala and PS Rüstavesi (check last place name!)..

Habitat. Lakes, ponds, pits, slowly flowing rivers, ditches and ‘kanalen’, in water up to 1(-1.3) m deep. It is a plant of mineral-rich or eutrophic waters, sometimes found in rather polluted habitats. It is also tolerant of slightly brackish conditions, and grows in sheltered bays in the Gulf of Bothnia and Gulf of Finland, and in pools and creeks behind the shore which retain a slight saline influence. At the northern edge of its range it is found in very shallow coastal waters (often less than 10 cm deep) in the Gulf, on mineral substrates mixed with a little sand, and further north in Nb Överkalix on the sandy edges of a lake-like stretch of the Kalix river.

22. Potamogeton rutilus

Distribution. Nem-SBor(-NBor). – D restricted to western VJy and to Brn Almindingen, always occurring at sites within 25 km of the sea. S rare, with very scattered localities from Sk to Vg (if confirmed) and Upl; very rare further north in south-east Jmt and at a single site in LyL SE of Tärnasjön. F rare, with a few scattered localities in southern Finland at V Parainen, U Espoo, EH Vesijärvi, ES Parikkala, EP Kristiinankaupunki and PK Tohmajärvi (Särkijärvi), and a single area (1 site??) in northern Finland, at Ks Määttälänvaara. Although the distribution of the species suggests that it is relictual, this might not always be the case. Bertilsson et al. (2002) suggest that it may be a spontaneous incomer in S Vg (check specimens!) and the one known locality in F EP, discovered in 1983, is a shallow bay recently separated from the sea, which presumably has been colonised fairly recently.

Habitat. Clear, mineral-rich water in lakes, often in sites with a rich aquatic flora, and more rarely in marl pits and in shallow bays recently separated from the sea. It usually grows in relatively shallow water 0.1-1 m (check H565351 - 3.2m?) deep over a variey of substrates including sand and soft, sometimes calcareous, mud. See details of D Fil Sø in Eriksson et al., 1949, Bot. Tid. 48, cited by Pedersen. Translate RDB.

23. Potamogeton obtusifolius

Distribution. Nem-MBor. – D occasional to frequent throughout check AFD maps. S frequent in the southern mainland from Sk to Dlr and Upl or Gst, no info yet on latter; further north known from southern Hrj, central and eastern Jmt and the coastal provinces north to NbF frequent in the south-west, especially in eastern V, U, St and EH, scattered elsewhere north to KiL and SoL (InL to check) with concentrations in some areas, including PS, Ks and around the head of the Gulf of Bothnia in OP and PeP.

Habitat. Shallow, eutrophic water in sheltered bays in lakes and at the slow-flowing edges of rivers and in large ponds, marl and clay pits and ditches; sometimes present in great abundance. It usually grows in water 0.3-0.8 m deep, but occasionally at depths of at least 1.25 m. It usually occurs over soft, at least partially mineral substrates including clay and mud, more rarely over sand and peat. ‘Kanalen’ in D. Based mainly on Sm flora, check other sources.

24. Potamogeton berchtoldii

Distribution. Nem-NBor. – Widespread and frequent in most of D, but apparently absent from the more southerly islands, including SJy Als, FyL Ærø and Langeland and D LFM (all specimens traced are referable to other taxa). S frequent throughout, although less common in areas where acidic soils preominate than elsewhere. F frequent throughout.

Habitat. Large and small standing waters, including ponds, rock pools and the more sheltered parts of lakes, ditches, slowly flowing streams and rivers and the sheltered edges of more rapidly flowing rivers. In the cultural landscape it has been favoured by the creation of small waters such as clay pits and ponds for grazing animals. It is absent from the most oligotrophic waters but otherwise tolerant of a wide range of nutrient levels, and also occurs, albeit rarely, in brackish water. It is usually rooted in soft substrates (including clay, mud and silt) but is sometimes found on fine sand. It is frequent at depths between 30 cm and 1 m, and occasionally found in very shallow water. In clear lakes it may grow in water up to 4.5 m deep, although only small palnts are found at depths of 2 m or more.

25. Potamogeton trichoides

Distribution. Nem. – D rare in the south, but almost certainly under-recorded; absent from the north. VJy Ribe, last collected 1902, SJy one area on west coast and two on the east name them!, LFM and south Sjae scattered sites, Brn Almindingen 1887. S restricted to two provinces in the south-west. In Sk it has been recorded since 1980 at only x out of a total of y sites from which material has been checked. It is, however, difficult to assess trends in this species, which is not only easily overlooked but is also capable of acting as a pioneer colonist. Visits to former sites alone do not necessarily give a complete picture of its current distribution. In Bh there is a concentration of recent records in the Göteborg area (assuming specimens prove OK). This is more consistent with its behaviour in Britain, where it does not appear to be declining.

Habitat. Small, eutrophic, often man-made water bodies including pools, mill ponds, clay and marl pits, kanal (S) and ditches, often on or near the coast. 

27. Potamogeton compressus

Distribution. Nem-SBor(-MBor). – D widespread, recorded in all provinces except LFM and formerly not uncommon in ØJy, VJy, western SJy and eastern Sjae, now rather rare and not recorded recently from FyL and Sjae. S widespread but uncommon in the south and east, absent from many western provinces and from western Vg, Dlr and Jmt. There is a high proportion of old records in provinces such as Sk, Vg and Srm, suggesting a decline in the south. F widespread but very uncommon in southern Finland, with concentrations in EH and PS, somewhat more frequent in the coastal region of OP and in PeP, Ks, KiL and SoL.

Habitat. In meso-eutrophic or + eutrophic water 0.5-2 m deep at the quiet edges of rivers or in their backwaters or associated ox-bow lakes, and in streams, sheltered bays in lakes, deep ponds (including mill ponds) and large ditches. It usually grows on soft silt or mud, but is occasionally found on former substrates such as fine sand. S to do.

28. Potamogeton acutifolius

Distribution. Nem-BNem. – D formerly widespread but rare, it has declined greatly in the last 150 years. In Jutland it persists as a rare species in Sjy but is probably extinct in Øjy (specimens seen from Kolding, undated but pre-1900, and Torrild Nørreskov 1913). It also appears to be extinct in FyL (Assens area 1887, Knudsbølle 1851, Ø. Skerninge 1851), LFM (Fyret, Vejrø, 1898) and Brn (Hundse Myre 1850). Atlas Fl. Danica database records a checked specimen from LFM, not found by CDP in herbarium, 9.2002. It was widespread in 19th century in Sjae, especially in the Copenhagen area, but is now rare there too. S formerly widespread but very local and patchily distributed in S. Sweden from Sk to Vsm and Upl; it has declined thoughout its range and is now very rare in all the provinces in which it is still extant. It reaches its current northern limit at Srm Aspö (Ryberg & Wanntorp 2001 specimen said to be at S but not seen 2003) and Upl Ingarö.

Habitat. A plant of the cultural landscape (‘kulturskapade’ – this translation OK?), found in shallow, nutrient-rich but clear and often at least slightly (check) calcareous water in lakes, ponds, pits, ditches and rivers (what sort of rivers?); also ‘kanal’ (Sjae) and ‘kanaler’ (Srm, Vg). Decipher Malmgren (1982) and translate RDB.

29. Potamogeton vaginatus map

Distribution. MBor. S Gulf of Bothnia from Mpd Tynderö (are there recent records from Mpd?) northwards to Nb, and in freshwater lakes add details of Stefan Ericsson’s site(s); formerly also south of this range at four outlying sites in S Upl, in the Baltic at Köpmanholm (collected 1910), Stora Värtan (1846) and Värmdö (1882-1896) and in freshwater at Ulvsundasjön (1890). F Gulf of Bothnia from St Pori northwards to PeP, and in an inland lake, Kampsajärvi, ?? km N.E. of the head of the Gulf at PeP Rovaniemen.

Habitat. In the Gulf of Bothnia P. vaginatus usually grows offshore in water at least 1.5 m deep, where it may occur in quantity in + pure stands or with P. perfoliatus. It appears to favour a degree of shelter, growing for example on the sheltered sides of islands. Sometimes colonies are found by the shore in water as shallow as 40 cm in periods of low water level; it is not known whether these plants are short-lived  colonists from deeper water or permanently established populations. Because of the inaccessibility of its habitat, plants are less frequently recorded in situ than when cast up on the shoreline or in flotsam. Add details of Stefan Ericsson’s site(s) and Finnish and Norwegian lakes.

32. Potamogeton filiformis

Distribution. Nem-NBor. D F all along the coast of the Gulf of Finland and Gulf of Bothnia. The only inland site in southern Finland is EH Vesijärvi but further north it occurs inland in scattered sites in Kn and the Lapland provines, and more frequently in the calcareous lakes of Ks.

Habitat. A plant of shallow water, most frequently found at depths of 10-30 cm although sometimes found in water at least 70 cm deep. It is most frequent at the edge of the Baltic and Gulfs of Bothnia and Finland, where it is characteristically found on harder substrates such as sand and even stones and boulders; plants are sometimes restricted to the sheltered edge of large stones and boulders. Plants occur more rarely on softer substrates, including soft mud and silty sand. Typical associates include Callitriche hermaphroditica, Eleocharis acicularis, Zannichellia palustris sens. lat. and Chara spp. The species is rarer in fresh water, where it usually occurs at the edge of neutral or base-rich lakes, rooted in hard mineral substrates such as sand and gravel. marl? Look up Finnish P. filiformis-type lake (known from Ks). Lakes through which rivers flow are a characteristic habitat in Finland. Stream and river habs, ditches by sea etc?? The ecological requirements of P. filiformis overlap with those of P. pectinatus and the two species often grow together, but P. filiformis extends into shallower water and more exposed sites, whereas P. pectinatus extends to deeper water.

34. Potamogeton pectinatus map

Distribution. F frequent along the coast of the Gulf of Finland from A eastwards to EK, and along the southern half of the Gulf of Bothnia; it is less frequent in the northern half but extends northwards to OP Kuivaniemi (specimens from PeP still to check). There is only one inland site, at PS Valvatus lake.

Habitat.


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