Bartsia alpina L.
2003; Wiley; Volume: 91; Issue: 5 Linguagem: Inglês
10.1046/j.1365-2745.2003.00809.x
ISSN1365-2745
Autores Tópico(s)Plant Diversity and Evolution
ResumoScrophulariaceae Tribe Pedicularieae (Rhinantheae) Bartsia L. [subdivided into Section Bartsia by Molau (1990) and his description of the species is incorporated in the following account]. A tufted perennial hemiparasitic herb with a short woody subterranean rhizome bearing, often abundantly at the nodes, adventitious roots with sparse root hairs. Haustoria develop on those adventitious roots in contact with neighbouring roots of host plants. The aerial shoots annual, erect or ascending, 8–30(−40) cm tall, unbranched or with a few short lateral branches, the stems pilose to hirsute with retrorse, white eglandular hairs. Leaves 10–25 × 6–15 mm, remote, decussate, sessile, herbaceous or subcoriaceous, ovate, apex obtuse to subacute, rounded to truncate at base, glabrous and rugose above, pilose to hirsute beneath, margins crenate–serrate. Inflorescence relatively loose, terminal with (1–)4–8(−11) floral nodes; bracts like the leaves but decreasing in size upwards, dull purple, exceeding the calyx; flowers 17–22 mm long, shortly pedicellate. Calyx green, often suffused with purple, glandular-hirsute with violet hairs, 6–10 mm long, tubular-campanulate, 4-cleft; the lobes narrowly triangular, obtuse to acute, entire, about as long as the tube or shorter. Corolla 15–20 mm, with a cylindrical tube and 2-lipped limb, violet or deep purple; upper lip entire or emarginate, longer than the lower; lower lip 3-lobed. Stamens 4, didynamous; anthers hairy, equally mucronate at the base. Style 14–20 mm long, pale violet, straight, decurved at apex; the stigma capitate ± exserted. Capsule narrowly ovoid, about twice as long as the calyx, hirsute, held ± erect in fruit, dehiscing into two valves, many-seeded. Seeds winged, 0.7–1.6 mm long, with mass 0.08–0.19 mg. Bartsia alpina shows rather little variation. Several forms with deviating corolla pigmentation appear occasionally throughout the distributional range but are of no taxonomical value: the yellow-flowered var. jensenii Lange described from Greenland, f. ochroleuca Blytt from Norway, and the rose-coloured var. pallida Wormskj. ex Lange from Greenland, also observed at Abisko, northern Sweden. None of these has been reported from the British Isles. Most variation is in shoot size and leaf dimensions which may be partially correlated to degree of exposure, grazing and nutrient status; plants from Scottish cliff-ledge populations are often much larger than those of English mire and pasture populations which are subjected to sheep and cattle grazing. According to Molau (1990) the number and position of teeth on the leaf margins show geographically correlated variation. Following an assessment of tooth number in Swedish populations and examination of more than 6000 herbarium specimens of B. alpina from its entire range, he suggested that its distribution includes two different sets of populations: subarctic populations north of 59° N latitude (but including the British populations) with a mean of 7–10 teeth, and alpine populations including all other populations south of 59° N latitude with a mean of 10–14 teeth. However, examination of herbarium specimens in The Natural History Museum, London, does not support this simple geographical separation. To what extent Molau's forms may be correlated with cytological races [see section VI (D)] is unresolved. Bartsia alpina is a native herb of moist basic soils in upland meadows and pastures, on unstable flushed slopes resulting from stream erosion, in hummocky calcareous marshes grazed by cattle and sheep in northern England (Pigott 1956), and on ungrazed periodically inundated ledges of calc-schist crags in herb-rich swards, mostly in the Scottish Breadalbane mountains (Lusby & Wright 1996; Wigginton & Rothero 1999). Bartsia alpina is geographically restricted to two areas in the British Isles, northern England and the central Scottish Highlands (Fig. 1). It is extremely rare in northern England, where it is known from only two sites in Cumbria (a few plants in Orton pastures and a large population in marshy pastures in the Crosby Gill SSSI (Ratcliffe 1977; Halliday 1997; Wigginton & Rothero 1999)); just a few plants still survive in Great Close Mire, Malham, North Yorkshire (Ratcliffe 1977; Wigginton & Rothero 1999), and the Upper Teesdale NNR, in County Durham where it is locally frequent (Bradshaw & Clarke 1965; Ratcliffe 1977). In Scotland, it is very local but may be frequent where it occurs in the Breadalbane range of Perthshire and in Argyll (Lusby & Wright 1996); the two largest populations in the British Isles occur on Beinn Laoigh and Meall Ghaordie (G.P. Rothero, unpublished report to Scottish Natural Heritage). The distribution of Bartsia alpina in the British Isles. (○) pre 1950; (•) 1950 onwards. Each dot represents at least one record in a 10-km square of the National Grid. Mapped by Henry Arnold, Biological Records Centre, Centre for Ecology and Hydrology, mainly from records collected by members of the Botanical Society of the British Isles. It is frequent in the mountainous areas of northern Europe westwards from the Urals through northern Russia into Finland, Norway and Sweden, with small disjunct populations in the floristically rich mires of Östergotland and Gotland. It is abundant in Iceland and occurs in the Faroe Isles. The species is present in many mountain ranges in central Europe, including the Sudeten, Tatra, Jura, the Alps, the Massif Central of France, Carpathians, southern Alps, Velebit, Bosnia-Herzegovina, southwards to the Pyrenees and south-west Bulgaria (Fig. 2). Outside Europe B. alpina is present in Greenland, and in north-eastern Canada around Hudson Bay southwards to Labrador (Fig. 2). The amphiatlantic, arctic-montane distribution of Bartsia alpina from Hultén & Fries (1986). The species is of common or fairly common occurrence within the hatched areas; solid circles (•) are isolated, but fairly exactly indicated occurrences; and solid lines indicate regions of incompletely or approximately stated occurrences. Contours and shading define areas of 200, 1000, and 2000 m a.s.l. Reprinted with permission. Bartsia alpina has been included in the arctic-alpine element of the British Flora (Dist. Br. Fl.) and described as European Arctic-montane by Preston & Hill (1997). It is classified as an amphiatlantic, arctic-montane species by Hultén & Fries (1986). The altitudinal range of B. alpina in the British Isles extends from 245 m near Orton, Cumbria (Halliday 1997) and from 510 m on Beinn an Dothaidh to an upper limit of 950 m on Creag Mhor, in the central Scottish Highlands, where most of the sites are between 600 and 800 m (Wigginton & Rothero 1999). In western and northern Norway it descends almost to sea level, and is very common throughout the mountains where it ascends to 1100 m in northern Norway and to 1960 m on Jotunheim, southern Norway (Atl. N. W. Eur.). In the Alps it reaches 3100 m, Schwarzwald 900–1450 m, Tatra 1000–2128 m, Velebit 1400–1798 m and Bosnia-Herzegovina 1500–1800 m (Vergl. Chor., Vol. 2, 1978). The lower distribution limits of B. alpina in Highland Scotland can be correlated with the 20 °C mean annual maximum isotherm; however, in northern England the limiting temperature is c. 25 °C and in Scandinavia 28 °C (Conolly & Dahl 1970). Bartsia alpina has been described by Ferreira (1959) as a distinctly basiphilous species which, in the central Highlands of Scotland, is confined to soils developed over soft, calcareous mica-schists of the Dalradian Series. Cliff ledge Dryas heath communities, containing B. alpina, on Creag Mhor, Perthshire, occur on a skeletal brown loam (Pl. Comm. Scot.). In similar communities on Ben Lui (= Beinn Laoigh), Perthshire, Elkington (1971) describes the occurrence of B. alpina in humic brown soils. In England, the plant is confined to soils developed on deposits overlying Carboniferous limestone – in particular, to small marshes flushed with water from calcareous springs, and characterized by the formation of hummocks with intervening bare patches. Such habitat complexes occur on slopes and hollows in the undulating moraine deposits on Widdybank Pastures in Upper Teesdale. Pigott (1956) described the development of one particular turfy marsh in a small area of the old cattle pasture, where the marshy ground of a broad soakway, below a series of springs, consists of a patchwork of hummocks scattered over a more or less smooth sloping expanse of sparsely turf-covered calcareous, muddy gravel. The hummocks are residual pieces of the surrounding continuous turf and soil mantle of the pasture. The active erosive agents are cattle trampling and patchy disruption of the turf with subsequent washing away of the silty mud during wet periods (see also IV). The hummock top habitat of populations of B. alpina consists of highly calcareous, gravelly clay with a CaCO3 content of 36–41%. Similar examples are found in Great Close Mire at Malham, in Orton Pastures and in the Crosby Gill SSSI. Soil analyses from some British habitats are given in Table 1. The data confirm that B. alpina is a calcicole in the British Isles; extractable Ca is > 300 mg 100 g−1 dry soil, with soil pH > 6.0 (Pl. Comm. Scot.). Additional measurements of soil pH have been made on samples collected from sites in Upper Teesdale, from Cetry Bank (6.9 and 7.2) and from cattle pasture on Widdybank Farm (6.4), also from the two main sites in the Crosby Gill SSSI (6.7 and 6.9). Quested et al. (2002) have investigated the role of Bartsia alpina and other root hemiparasitic Scrophulariaceae in nutrient cycling in a habitat low in available nitrogen and phosphorus on a solifluction creep soil in northern Sweden. The open site (400 × 600 m) on a gentle, north-facing slope, at c. 400 m a.s.l., is in the subalpine birchwoods close to Abisko (68°21′ N, 18°49′ E) and the local population of B. alpina consists of some 10 000 individuals (clones and genets) (Molau 1995). The species composition of the vegetation comprises dwarf shrubs, graminoids, herbaceous plants and Sphagnum species (Nilsson & Svensson 1997). The N content of mature green leaves and the N, P and C content of standing leaf litter were measured, including the most abundant hemiparasites in the community, B. alpina and Pedicularis lapponica, and also in co-occurring potential host species (Quested et al. 2002). In samples of fresh leaves and litter of dicot herbs (n = 4) the percentage N ± SE was 2.85 ± 0.05 and 2.00 ± 0.04 in B. alpina, 4.18 ± 0.06 and 1.81 ± 0.05 in P. lapponica, compared with 2.79 ± 0.02 and 0.77 ± 0.04 in the potential host Polygonum viviparum (Persicaria vivipara). In contrast, in the dwarf shrubs it was 2.53 ± 0.03 and 0.74 ± 0.02 in Betula nana, 1.00 ± 0.02 and 0.69 ± 0.02 in Empetrum nigrum ssp. hermaphroditum, in Vaccinium uliginosum 1.72 ± 0.10 and 0.48 ± 0.03, and in V. vitis-idaea 0.91 ± 0.01 and 0.83 ± 0.09, respectively. Thus fresh leaves of the hemiparasites had greater N concentrations than the leaves of the host species, and this difference was even more marked in leaf litter. Litter of B. alpina and of the above four potential dwarf shrub host species was decomposed alone and in two species mixtures, in a laboratory microcosm experiment. Bartsia alpina litter decomposed faster and lost between 5.4 and 10.8 times more N than that of the dwarf shrubs. Mixtures of dwarf shrub and hemiparasite litter showed significantly more mass loss and CO2 release than expected on the basis of the component species decomposing alone. Nutrient release from the rapidly decomposing litter of B. alpina may stimulate decomposition in the poor quality litter of the dwarf shrubs by enabling faster utilization of C substrates. Quested et al. (2003) have tested the hypothesis that plant growth is enhanced by the litter of B. alpina, in comparison with litter of co-occurring dwarf shrub species, using a pot-based bioassay approach. Growth of Betula nana and Poa alpina was up to 51% and 41% greater, respectively, in the presence of B. alpina litter, than when grown with dwarf shrub litter (Betula nana, Empetrum nigrum ssp. hermaphroditum and Vaccinium uliginosum). The nutrient concentrations of Betula nana grown with B. alpina litter were almost double those of plants grown with dwarf shrub litter, and a significantly greater proportion of biomass was allocated to shoots rather than roots, strongly suggesting that nutrient availability was higher where B. alpina litter was present. A further extended comparison of leaf and litter tissue quality, N resorption and decomposability in hemiparasites with those of a wide range of other plant groups (involving a total of 72 species and including other groups with access to alternative nutrient sources, such as N fixers and carnivorous plants) was carried out by Quested et al. (2004), and reinforced the results described above. A litter trapping experiment was also carried out by Quested et al. (2004) to assess the potential impact of hemiparasites on nutrient cycling. Bartsia alpina was estimated to increase the total annual N input from litter to the soil by c. 42%, within 5 cm of its stems. The results provide evidence of a novel mechanism by which hemiparasites (in parallel with N fixing species) may influence ecosystems in which they occur. Through the production of nutrient rich, rapidly decomposing litter, B. alpina potentially greatly enhances the availability of nutrients within patches where it is abundant, with possible consequent effects on small scale biodiversity. The National Vegetation Classification (Rodwell 1991, 1992) records B. alpina as scarce in two communities (M10 and CG14). It occurs in Carex dioica–Pinguicula vulgaris mire (M10), an expanded version of the Pinguiculo-Caricetum dioicae (Jones 1973emend. Wheeler 1975, 1984), in the Molinia caerulea–Eriophorum latifolium variant of the Briza media–Primula farinosa subcommunity which is predominantly centred on the Pennines of northern England. This low productivity, base-rich, ground water-fed fen vegetation type has affinities with the 'turfy marshes' previously described by Pigott (1956) from Upper Teesdale, and included by Wheeler (1980) in the Caricion davallianae small-sedge mire, in particular the B. alpina variant of the Pinguiculo-Caricetum molinietosum, together with Juncus alpinoarticulatus, Kobresia simpliciuscula, Saxifraga aizoides and Tofieldia pusilla. Bartsia alpina is also found in the calcareous marshes of the Malham Tarn area (Sinker 1960), included by Wheeler (1980) in the Sesleria variant of the same sub-association, with Sesleria caerulea, Festuca ovina, Leontodon autumnalis and Campanula rotundifolia. At Orton pastures, Cumbria, B. alpina occurs in an example of sub-association filipenduletosum (Wheeler 1980), a species-rich community of spring mires with the distinguishing species Angelica sylvestris, Cirsium palustre, Filipendula ulmaria, Lotus pedunculatus and Mnium longirostrum (Plagiomnium rostratum). Carex capillaris also occurs at Orton near the Bartsia location. In the central Scottish Highlands, B. alpina is found in the Dryas octopetala–Silene acaulis ledge community (CG14), in which Alchemilla alpina, Campanula rotundifolia, Carex capillaris, C. pulicaris, Dryas octopetala and Persicaria vivipara are constant species. This vegetation type is synonymous with the Dryas-Salix reticulata nodum of McVean & Ratcliffe (Pl. Comm. Scot.). It is a community which represents the nearest approach to the European montane dwarf-shrub heaths of the Elyno-Seslerietea (recast by Oberdorfer (1978) as the Seslerietea variae). Within this class, the Dryas-Silene community is closest to the kinds of Scandinavian vegetation included by Nordhagen (1928) in the species-rich Dryas association within the alliance Kobresieto-Dryadion (Elynion Bellardii) with which it shares a number of species: Astragalus alpinus, Bartsia alpina, Carex atrata, C. capillaris, C. rupestris, Dryas octopetala and Salix reticulata. In two localities in the Scottish highlands, B. alpina has also been recorded in stands of the Luzula sylvatica–Geum rivale tall-herb community (U17), and in a single locality the associated species seem closest to CG11, the Festuca ovina–Agrostis capillaris–Alchemilla alpina grass heath (G.P. Rothero, unpublished report for Scottish Natural Heritage). On calcareous soils in the alpine-subalpine region of Norway and northern Scandinavia, B. alpina occurs in four associations in the alliance Kobresieto-Dryadion: in the Caricetum nardinae, Kobresia myosuroidis, Cassiopetum tetragonae dryadetosum and Dryadetum octopetalae (Nordhagen 1936, 1955). Examples of some of these communities have also been described for west Finnmark, in Norwegian Lappland (Coombe & White 1951), where B. alpina occurs in dry heaths on well drained dolomite, and in intermediate habitats between this type and the wettest calcicolous bogs. In the Pältsa region of northernmost Sweden B. alpina occurs in three associations of the Dryadion alliance (Hedberg et al. 1952). In the mountains of the Torneträsk area of northern Sweden, B. alpina occurs in snow-bed communities on circum-neutral calcareous soils: in the species-rich Salicetum polaris association referred to the alliance Polarion and in the Trollius europaeus society in the alliance Ranunculo-Poion alpinae (Gjærevol 1950). In the subalpine belt, B. alpina occurs in open forest ecosystems in which Betula pubescens ssp. tortuosa (ssp. czerepanovii) is the most abundant tree. Where the ground vegetation is of the meadow type, B. alpina is present in the Geranium–Vaccinium myrtillus communities (Sonesson & Lundberg 1974). In Finland, B. alpina occurs in rich, open, treeless Sphagnum warnstorfii fens in the forest zone, in areas of supplementary nutrient effect, together with Carex capillaris, C. vaginata, Festuca ovina, F. rubra, Angelica sylvestris, Cirsium heterophyllum, Crepis paludosa, Equisetum pratense, Filipendula ulmaria, Galium uliginosum, Geranium sylvaticum, Geum rivale, Parnassia palustris, Saussurea alpina and Solidago virgaurea (Eurola et al. 1984). Bartsia alpina occurs in subalpine and alpine Calcareous Small Sedge Fens referred to the alliance Caricion davallianae, in the order Tofieldietalia, in Central Europe (Ellenberg 1988). In Poland, in the high-mountain calcareous grasslands of the Tatra mountains, B. alpina is a characteristic species of the order Seslerietalia coerulea (= variae) in the class Elyno-Seslerietea, and is also a constant in the Versicoloretum typicum association (Szafer 1966). The abundance of several of the rare Teesdale plant species, including B. alpina, on the tops of hummocks in the turfy marshes, may be contrasted with their relative scarcity in the nearby closed hay meadows under the competition of the lusher vegetation. A detailed description of the vegetation in a small area of turfy marsh is given by Pigott (1956). The site he described was enclosed in 1956 by a wire and post fence to prevent grazing and trampling by cattle. After 20 years there was little change in the composition of the vegetation, although, in the years following enclosure, the number of flowering-shoots of B. alpina increased from fewer than 10 to > 200 (Pigott 1978). The results of surveys carried out in 1976–81 and in 2000 show that during this period the frequency of B. alpina in various base-rich flushes in Widdybank Pasture has declined (unpublished report by R. Jerram for English Nature). It is clear that grazing regime is one of the most important factors. There is evidence that the vegetation has become coarser, with locally increased abundance of taller rushes and that once relatively open swards with patches of bare soil have become closed. The implications are that the pasture should be well grazed by the right type of stock and at the right time of year (see XI). Although grazing and trampling by cattle in this habitat are crucial for the maintenance of populations of B. alpina, leaf size is much reduced and the incidence of flowering and fruiting is greatly affected. Bartsia alpina forms local populations of dense clones with branching, perennial rhizomes. The density and vigour of British populations fluctuate mostly in response to grazing and trampling pressures by sheep and cattle and their management (see also IV, XI). In northern England, at Cetry Bank, Upper Teesdale NNR, on the steepest part of an eroded boulder-clay river bank with some evidence of grazing, there were some 300 flowering shoots in 1979, in 1985 there were > 1000 shoots, but only two in flower. In the Crosby Gill SSSI, in grazed neutral grassland, there were c. 263 shoots in total in the two main colonies on Hazel Moor in 1985, c. 440 in 1986, c. 890 in 1988, and c. 830 shoots in 1990; here plants though very short and highly branched with small leaves usually flower under the evidently favourable grazing regime (Crosby Gill: Bartsia alpina: Status Report 1993, by N.A. Robinson, English Nature NW Region, unpublished). In cattle-grazed Orton pastures, in three holdings there were some 234 shoots but only 11 inflorescences in 1993. The largest populations occur in Scotland where the plant is confined to ungrazed cliff ledges of calcareous schist which are subject to some irrigation (G.P. Rothero, unpublished report to Scottish Natural Heritage). Direct counts on crags are difficult so population estimates are based on more easily seen flowering shoots which were estimated to account for 20% of the total shoot populations; in Ben Laoigh, NNR, on one area of crags some 1750 shoots, on another c. 1125, and on a third area of crags c. 314 were recorded in 1995; on the large steep crags of Creag Laoghain, Meall Ghaordie, a total of > 1845 shoots were recorded in the same year. In its montane and subarctic habitats, the aerial shoots die down in the autumn and the overwintering buds of Bartsia alpina are clearly extremely tolerant of freezing temperatures in winter. It is rarely subjected to drought, being confined to moist habitats and having high transpiration rates day and night which facilitate the movement of water from host species to the hemiparasite [see VI (E)]. Bartsia alpina is a hemiparasite forming dense clones with perennial, branching, sympodial rhizomes composed of the persistent basal portions of previous generations of annual aerial shoots (Mathiesen 1921; Molau 1990). At the start of every growing season rhizomes develop from overwintering buds found in the axils of the uppermost scale leaves at the base of each dead aerial shoot. Each rhizome bears decussated scale-leaves and either grows in a direction horizontal to the ground surface, with elongated internodes, or may have quite short internodes and grow vertically, dependent upon the substrate nature. Plants sometimes have a lengthy and much thickened (to c. 5–8 mm diameter) root, which could be the original main root axis. Adventitious root formation at the nodes is very variable and perhaps reflects host environment and nutrient availability. In early summer, an innovation-bud develops in each of the axils of two opposite scale-leaves on each rhizome, either near the point where an elongated rhizome is beginning to turn upwards, or at the base of a vertical growing rhizome. The growing points of the rhizome show reduced internodes and die towards the end of the growing season, to be replaced in the following year by newly expanding rhizomes developing from overwintering buds formed at the bases of the dying aerial shoots. By the following mid-late summer new, unbranched aerial shoots arise from each of the two innovation-buds, some shoots remain vegetative whilst others are flower-bearing. After flowering and fruit-setting, the shoots die down leaving a persistent, subterranean basal portion immediately above the innovation-buds, and winter-buds are formed in the axils of the uppermost scale-leaves. Growth of the sympodial rhizome is continued by the development of these winter-buds. Seedlings, which develop from seed germinating in early summer, produce buds in the axils of the cotyledons. Whilst the uppermost part of the primary shoot dies, in the following growing season one of these buds develops into a foliage bearing shoot (Heinricher 1910). Further development of seedlings proceeds as described above for mature plants, but there is a time lag of at least 5 years, but more usually 10 years, from seed germination to first flowering (Mathiesen 1921; Molau 1995). In material collected in Iceland, Musselman & Rich (1976) observed developing haustoria in the region of maturation behind the root tip on those adventitious roots of B. alpina in contact with neighbouring plant roots. They suggested that perhaps the production of adventitious roots ensures a continual supply of haustorial contacts. It was not clear in their study how long the haustoria survived; no haustoria examined appeared to be more than 1 year old. The presence of haustoria was confirmed on Carex sp., Bistorta (Persicaria) vivipara and Empetrum eamesii. The haustoria of B. alpina are small (0.1–1.0 mm in diameter), whitish in colour and their internal organization is similar to that of other parasitic Scrophulariaceae (Musselman & Dickison 1975). The vascular core of the haustorium resembles that of the related genera Melampyrum and Euphrasia in being only moderately developed. Like the vascular core elements of other parasites, the vessel elements are irregularly shaped with scalariform thickenings and lateral perforation plates. In the haustorium of B. alpina, the axial strands which extend from the vascular core to the xylem of the host are bowed similar to those of the Aureolaria type. In mature haustoria a continuous xylem conduit is present from the parasite to the host, but there is a striking lack of phloem sieve elements. Visual examination of root connections and 14C labelling of suspected host species have been used by Nilsson & Svensson (1997) to identify the host range of two hemiparasites, B. alpina and Pedicularis lapponica; the latter method was more sensitive than root examination. This study was carried out in a subalpine open area close to Abisko, northern Sweden [see II (B)]. Both species made parasitic root connections to most other species in the surrounding vegetation. The 14C labelling revealed that the preferred hosts of B. alpina were 15 species in the families Betulaceae, Cyperaceae, Empetraceae, Equisetaceae, Ericaceae, Fabaceae, Lentibulariaceae, Liliaceae, Polygonaceae and Salicaceae, but the highest percentage of connections were to Pinguicula vulgaris > Carex norvegica, Salix glauca and Tofieldia pusilla. Visual examination of root connections also confirmed that the following were host species: Andromeda polifolia, Carex norvegica > Astragalus alpinus, Festuca ovina > Polygonum viviparum (Persicaria vivipara), Tofieldia pusilla and Vaccinium uliginosum. Leaves collected in August, 2002 from cattle pasture on Widdybank Farm, Upper Teesdale, had a mean stomatal frequency (n = 15) of 56 ± 6 mm−2 on the under surface but no obvious guard cells on the upper surface (W.J. Davies, personal communication). Roots of Bartsia alpina collected in mid-July 2002 from Hazel Moor, Crosby Gill SSSI, and in August 2002 from Cetry Bank, Upper Teesdale were examined and found to be non-mycorrhizal (D. Johnson, Irene Johnson and G. Palfner, personal communication). Harley & Harley (1987) record both the presence and absence of VA mycorrhiza in B. alpina from continental Europe. It is reported by Michelsen et al. (1998) to be non-mycorrhizal in a heath tundra site near Abisko, northern Sweden. A nanophyllous to microphyllous proto-hemicryptophyte with long-lived rhizomes; in an isolated population in a small fen in the Abisko area of northern Sweden (125 clones observed during a 5-year period), recruitment was shown by Molau (1990) to be extremely slow; the mean individual life span (population turnover) was 194 years. Propagation seems generally to be by vegetative spread, especially fragmentation of the rhizome. In the British Isles seedlings have been noted occasionally and, although their survival has not been monitored, their presence indicates that recruitment sometimes takes place by this means (Wigginton & Rothero 1999). Seed reproductive effort has been assessed by Molau (1995) in terms of the fate of the originally initiated ovules in the average B. alpina capsule. Only 27% of ovules turned into dispersed seeds (73% were lost to abortion, predation and non-dispersal) and of these 24% were viable, but only 0.002% of the seeds produced new flowering genets. Chromosome counts of B. alpina suggest that a range of cytotypes occurs. Whether these may be in part correlated to the morphological types recognized by Molau (1990) is, however, unclear. No counts of Scottish material have as yet been made. Material examined from Upper Teesdale, Durham and Great Close Mire, Malham, North Yorkshire (Elkington 1974, 1978), shows 2n = 24. This is the predominant number recorded throughout the European range of the species (F.J. Rumsey, unpublished; Molau 1990; Dobeš & Vitek 2000). A deviating count of c. 2n = 28 by Böcher & Larsen (1950) of material from West Greenland, led them to suggest that arctic material may differ in base number from that in Central Europe. Subsequent counts from the Scandinavian arctic have consistently given counts of 2n = 24. Confirmation of the apparently aberrant number from Greenland is therefore desirable, as would be counts from the North American portion of the amphi-atlantic range. Favarger (1953) suggested 2n = 24 represents the tetraploid level as Mattick (in Tischler 1950) reported 2n = 12 from Tyrolean specimens. Confirmation of this count is desirable because a base number of x = 6 seems unlikely given the range demonstrated elsewhere in the Pedicularieae, even assuming a near basal position for Bar
Referência(s)