The Sheffield meeting was a return to our traditional format of AGM weekend meetings – with no special anniversaries or topics to consider in the symposium session. For all that it was a very successful meeting, due in no small part to the impeccable arrangements made by Tom Blockeel. The venue, Tapton Hall, was pleasant enough and – as one member noted – offered no nonsense service at no nonsense Yorkshire prices.
There are many interesting bryological sites of interest within striking distance of the city. Tom’s local expertise and superb field knowledge showed through here. Surprisingly he took the meeting not west towards the Peak District but east, towards intensively farmed land. What initially appeared to be an unpromising and disturbed woodland turned out to be a marvellous site, holding many rarities.
I am also grateful to the speakers who provided an interesting day of talks covering tropical, temperate and laboratory bryophytes. As usual, accounts of the lectures follow, written by the speakers.
Mr J. Goode (Royal Holloway and Bedford New College, Egham, Surrey): Caulonema, chloronema, rhizoids and plates in the moss protonema.
Moss protonemata represent an ideal model system with which to answer fundamental questions in plant cell biology. They are small, grow rapidly, are relatively simple and can be easily cultivated under axenic conditions in the laboratory.
The moss protonema is the juvenile stage of growth of mosses, from spore germination until the production of the mature gametophyte shoot. Protonema are also produced by regeneration of either specialised vegetative reproductive propagules (gemmae), or of virtually any part of the moss plant. In the majority of protonemata, the spore germinates to produce a tip-growing filament which divides and branches, and eventually produces a gametophore shoot as a modified side-branch. This progression can be summarised as 1-D to 3-D.
Tetraphis pellucida and Sphagnum fimbriatum are different in that the protonema has an intermediary two-dimensional plate phase, produced from the filamentous phase and from which the shoot is formed; a 1-D to 2-D to 3-D progression. These mosses differ from each other in the mechanism of plate formation: in Sphagnum plates are formed at the tips of chlorophyllose filaments, and in Tetraphis they are formed as modified side branches.
There is a wide array of types of filaments in the protonema. Although in some cases the distinction between different types is clear-cut, absolute distinctions between filamentous types is ill-advised owing to the developmental plasticity shown by the protonema.
Although widely regarded as a simple phase of growth, some protonema exhibit quite complex structures. Dicranoweisia cirrata produces specialised protonemal gemmae by means of an abscission cell, and Bryum tenuisetum produces abscission cells which produce gemmae by fragmenting the chloronemal filaments. Other protonema, including Rhytidiadelphus loreus and Bryum flaccidum produce unspecialised gemmae by sub-apical cell divisions and the subsequent rounding off of cells to form short fragments of ‘brood cells’. If these are then transplanted to fresh media they regenerate in a manner similar to the regeneration of gemmae.
Dr T.A. Hedderson (University of Reading): Influences of size, phylogeny and water relations on life history variation in mosses.
Life histories (the combination of age-specific fecundities and survival probabilities which organisms display in some particular environmental context) are of great interest to evolutionists since they define the operation of the joint processes of natural selection and adaptation. Physiological and energetic realities mean that life history traits will be involved in trade-offs (e.g. Schaffer, 1974; Stearns, 1976) and should thus co-evolve to yield adaptive ‘tactics’ in specific ecological contexts (e.g. Stearns, 1976; Brown, 1983).
Comparative approaches have been widely used to identify such tactics, generally emphasising the importance of age-specific mortality or spatio-temporal patterns of resource availability to selection on life histories (Harper, 1967; Southwood, 1977; Stearns, 1976). However, other ecological factors may be important, and traits may be constrained allometrically, or by peculiarities of physiology or development in some organisms (see review in Stearns. 1980). Furthermore, phylogenetic effects seem to be pervasive, suggesting that microevolutionary forces acting on life-histories are constrained within larger phylogenetic lines.
The existence of such a suite of interacting factors has important implications for comparative approaches to the study of life histories, and raises a number of questions relating to the existence of life history tactics and our perception of them. This analysis addresses five of these questions for a group of mosses: 1) Does taxonomic level significantly affect life history variation? 2) Does covariation of life history traits depend on taxonomic level or phylogenetic affinity? 3) What are the relationships of life history traits and their patterns of covariation with gametophyte size? 4) Is there a relationship between life history variation and morphological variation associated with water relations? 5) Are phylogenetic effects mediated by difference in size or water relations among taxonomic groups?
The analysis included a total of 336 species from the Pottiales, Funariales and Polytrichales, representing nine families and 52 genera, for which data were available on five life history traits (i. sexuality, ii. presence or absence of specialised asexual reproductive diaspores, iii. longevity, iv. median spore diameter, v. number of spores per capsule (estimated as the ratio of capsule volume to spore volume minus 35% for interspore space)), size (the only readily available measure is maximum length of the female gametophyte), and five water relations traits (i. growth form, ii. stem structure, iii. leaf papillosity, iv. nature of the leaf margin, v. nature of the leaf apex).
Univariate and Multivariate Nested Analysis of Variance revealed strong taxonomic effects on individual life history traits and the ways in which traits covary. Principal Components Analyses within orders and families also show that the ways in which life history traits covary differs among higher taxonomic levels. Size has only a small effect on variation in individual life history traits, and regression analyses yielded either non-significant or low R² values.
A Canonical Correlations Analysis was used to examine joint variation among life history and water relations traits. This analysis revealed a clear relationship between life history variation and variation in morphological design associated with differing water relations. The first Canonical Variate from the water relations set ranks species from those with poorly developed water uptake and/or retention mechanisms. The life history Variate associated with it ranks species from those that are small, short lived, and produce few large spores to those with the opposite suite of traits. Variation on the water relations Variate accounted for 70% of variation on the life history Variate. Plots of species on the first pair of Canonical Variates revealed again the influence of phylogeny, with each family occupying a unique region of the reduced space. The relationship between water relations and life history seen across all species is sometimes weakened when examined across species within families.
After statistically removing the effects of size and water relations by Analyses of Covariance and Regression procedures, all phylogenetic effects noted earlier still persist.
Patterns of life history variation seen across species may result from a number of co-acting factors including phylogenetic inertia, ecological forces and allometrically forced relations with size. The influence of phylogeny is particularly great and phylogenetic information needs to be included explicitly as part of comparative analyses.
Brown, K.M. (1983). Do life history tactics exist at the intraspecific level? Data from freshwater snails. Am. Nat. 121: 871-879.
Harper, J.L. (1967). A Darwinian approach to plant ecology. J. Ecol. 55: 242-270.
Schaffer, W.M. (1974). Optimal reproductive effort in fluctuating environments. Am. Nat. 108: 783-790.
Southwood, T.R.E. (1977). Habitat, the templet for ecological strategies? J. Animal. Ecol. 46: 337-365.
Stearns, S.C. (1976). Life history tactics; a review of the ideas. Quart. Rev. Biol. 51: 3-47.
Stearns, S.C. (1980). A new view of life history evolution. Oikos 35: 266-281.
Dr S. Russell (British Antarctic Survey, Cambridge): Bryofloristic relationships within southern African forests.
The degree of uniformity shown by the vascular flora of the inland forests of southern and eastern Africa has led to the inclusion of this vegetation in a single ‘Afromontane’ phytochorion. Recent improvements in knowledge of the bryoflora of the region – particularly in Tanzania and South Africa – permit a more detailed understanding of biogeographic relationships among the ‘islands’ of forest vegetation that occur in the Afromontane ‘archipelago’, viz.:
- A far larger proportion of southern Africa’s bryoflora occurs in the forest biome than is the case for the vascular flora.
- The drop in forest species numbers from the Equator to the Cape is not as evident among bryophytes as it is for vascular plants.
- Many bryological examples can be cited to support the diminution in numbers of tropical species southwards, and temperate species northwards along the Afromontane chain. However, the trend is not as marked among mosses and liverworts as it is with the vascular plants.
- Adjacent forest regions show an average 50% greater similarity when compared on the basis of their bryofloras rather than the flowering plants alone. Concomitant lower levels of endemicity are displayed by the forest regions, when their total flora is considered.
A low apparent degree of affinity between the forests of Malawi and those of neighbouring Zimbabwe and Tanzania may at present be explained by the poor knowledge of the Malawian bryoflora. This situation will be remedied as results become available from several collecting expeditions to the Malawi-Zimbabwe region that are taking place during the early 1990s.
Mr B.J. O’Shea (London): Beginner’s guide to tropical bryology – the BBS Tropical Bryology Group trip to Mount Mulanje, Malawi.
The BBS TBG stated some time ago its wish to organise a tropical collecting trip, and the activity on Bryologia Africana (the new African flora) and the current gap in our knowledge of African bryophytes – the ‘Malawi gap’- served to make Mount Mulanje in Malawi the target.
The expedition numbered nine botanists – three academics, two herbarium staff, three conservationists and one amateur. Three of the party were from Africa, and the leader, Shaun Russell, moved from Africa to England during the course of organising the trip.
The trip took place from 12 June to 4 July 1991, and was based at the National Herbarium and Botanic Garden, Zomba, which also provided logistic help. We were on the mountain for 12 days, with 3 more days around the base.
The base of Mount Mulanje is at about 800 m, and at this height it is about 26 x 22 km in size. The plateau area of rolling grassy uplands, intersected by deep forested ravines and gullies, is at about 1800 m to 2100 m. Above the plateau are deeply fissured boulder-strewn rock slabs and walls, and there are 20 peaks that exceed 2500 m. The highest peak is Sapitwa at 3002 m.
It is a popular walking area and there are well-marked paths, and huts to stay in (the paths and huts being maintained by forestry staff). The rock is largely granitic, giving landscapes reminiscent of Scotland, but particularly to the south of the mountain there are areas of rain forest in the ravines and on the south-facing cliffs.
Bryophyte collecting in Malawi was until recently very limited, and Mount Mulanje is probably the richest area. Before the expedition, there were only 205 mosses and 97 hepatics recorded from Malawi, of which 98 and 59 respectively were from Mount Mulanje.
The expedition covered a large area of the mountain, and collected about 4500 packets from a wide variety of habitats. Some of the areas of the mountain damaged by agriculture and forestry were visited, with the aim of providing evidence of the reduction in bryophyte numbers in such areas. The disturbed areas were clearly less rich, and this underlined the concern of the authorities about deforestation on the mountain – several hundreds of lives were lost earlier this year on the NE of the mountain owing to landslides, widely blamed on deforestation, and the water supply of much of southern Malawi depends on water captured by Mount Mulanje.
Our collections are now being catalogued at Reading University Herbarium, and the task of identification is now about to begin. We hope that out results will add to the pressure for making Mount Mulanje a National Park and a Biosphere Reserve.
Ms A.J. Russell and Prof D.J. Cove (University of Leeds): Studying protonemal development using time-lapse video recording.
Physcomitrella patens is being used for studies of development in Leeds because, as in other Funariales, the pattern of development from newly regenerated protonema to the formation of gametophores is marked by clearly defined transitions from one cell type to another. The apical protonemal cells respond to environmental stimuli in a similar manner to higher plants. The techniques of genetic analysis, including the isolation of developmental and physiological mutants, are being used to study the role of plant hormones in development and the molecular basis of tropic responses.
Time-lapse microscopy has previously been used to study the gravitropic response of moss filaments grown in the dark. We have now developed a method of filming protonema in the light to enable more detailed observation of light-mediated steps in development and to obtain data on their timing. To avoid the problems of unnatural growth of filaments caused by their confinement on a microscope slide and/or the continual perfusion of liquid medium, cultures are grown on a thin layer of agar surrounded by deep agar, and filmed using an inverted microscope.
Using this technique we have been able to obtain data on the comparative growth rates and cell cycle times of chloronema and caulonema and film the transition from one cell type to another. The hypothesis that the timing of the cell cycle is related to cell volume can be tested.
Spore germination and the regenerative effect of light on dark-grown filaments have been compared. The increase in mitotic activity and lack of a polar direction of side-branch initiation has lead to the hypothesis that spore germination and cell regeneration represent a preferred starting point for development.
The plant hormone cytokinin, which at certain concentrations causes a massive increase in budding in the moss, is known to have a promotive effect on cell division. It has been possible, using time- lapse, to compare the first cell divisions of natural buds with those of cytokinin-induced buds. We found no increase in the timing of cell division in response to cytokinin. While the initial steps in bud formation such as the movement of chloroplasts into the apex of an initial and the formation of the vacuole in the stalk area appear to be the same in both cases, the subsequent pattern of cell division in natural bud formation is disrupted by the addition of cytokinin. Particularly noticeable is the inhibition of the early development of rhizoids.
We are planning to use this technique to film the effects of specific inhibitors on growth. From observations of these and normal cellular events we hope to gain more insight into developmental mechanisms.
Knight, C.D. and Cove, D.J. (1988). Time-lapse microscopy of gravitropism in the moss Physcomitrella patens. In J.M.GIime(ed.), Methods in Bryology, pp. 127-129. Hattori Botanical Laboratory, Nichinan, Japan.
Mr G. Rothero (Dunoon, Argyll): The bryophyte dominated snow-beds of the Scottish Highlands.
As a result of ideas mooted by the conservation committee of the BBS and taken up (and paid for!) by the NCC in Scotland, I spent the summers of 1989 and 1990 visiting a substantial proportion of the hills in the Highlands where the snow lies into mid-summer or later. The first year concentrated on the Cairngorm area and the second covered as much as was possible of the rest. A bryophyte species list with an assessment of relative abundance was compiled for each site and a series of quadrat samples recorded for community analysis.
Broadly speaking, the major division of sites is between the deep coire sites with a high amplitude of relief, crags and block scree and the ‘nivation hollow’ type of site with rounded features, low relief and large areas of fine substrate. The former occurs widely but the latter is concentrated on the Cairngorm plateau with outliers in the Ben Alder Forest and on Creag Meagaidh. The ‘coire type’ site, with its great variety of habitat, often has the most impressive species lists, but the best examples of the snow-bed bryophyte communities come from the finer, more uniform substrates of the ‘nivation hollow’ sites.
Where the substrate is fine and is subject to frost-heave then the vegetation is likely to be some form of Marsupella brevissima – Anthelia juratzkana snow-bed, often in the form of a wrinkled crust of small hepatics. Within forms of this community some very rare plants occur. Marsupella condensata can be abundant on some Cairngorm sites, and on Creag Meagaidh and Ben Lawers both male plants and sporophytes occur occasionally. Other rarities which seem to have a more sporadic occurrence are Marsupella arctica, M. sparsifolia and Gymnomitrion apiculatum – though the last two are exceedingly difficult to pick out in the field.
Where the substrate is more stable but still relatively fine, large stands of the Polytrichum sexangulare – Kiaeria starkei snow-bed occur, particularly in melt-water channels. These may be dominated by one or the other of the mosses, the largest pure stands being of Kiaeria starkei, sometimes covering over 100 m². Often associated with this community are stands of Moerckia blyttii and Pleurocladula albescens, as well as large cushions of more cosmopolitan species like Cephalozia bicuspidata, Nardia scalaris and Barbilophozia floerkei. Where the substrate is permanently irrigated there can be large areas dominated by Pohlia ludwigii snow-bed, visible from a distance as a bright green carpet, often bordering burns.
In spring communities associated with melt-water, spectacular and very visible stands of Pohlia wahlenbergii var. glacialis may occur, often at some distance from the snow-beds themselves. Scapania paludosa occurs as cushions in springs at the base of block scree (where it may grow with Rhizomnium magnifolium). Rather more remote from the late snow but irrigated by melt-water, a small number of mires contain substantial populations of Sphagnum lindbergii.
On rocks associated with the areas of late snow-lie a number of interesting Andreaea species occur. Andreaea nivalis can be abundant on rocks in burns, on crags with permanent irrigation and on irrigated gravel. This level of abundance is limited to the Cairngorms and the Ben Nevis- Aonachs massif. In one or two of the larger melt-water burns in the Cairngorms Andreaea frigida is common, occurring with Andreaea nivalis. On flat rock surfaces in the areas of latest snow-lie, Andreaea blyttii can be abundant and is certainly widespread. This species is easily picked out and it is a puzzle as to how it has been overlooked in the past.
On the crags and screes in the coires a few more interesting species occur. Marsupella boeckei var. boeckei forms green wefts on irrigated steep rock faces and bears little resemblance to the var. stableri which is common. Brachythecium glaciale, B. reflexum and, more rarely, Lescuraea patens can be found, usually associated with the litter of the fern Athyrium distentifolium in the block scree. Irrigated rocks in one or two coires have Hygrohypnum molle, H. smithii and in one case Hygrohypnum styriacum, a surprising addition to the British flora.
All of these sites are wonderful places, most are remote and, in their snowy garb for most of the year, seem inviolate. The tiny total area involved (some 160 to 200 hectares seems a reasonable estimate) makes the snow beds vulnerable. The major threat is amply demonstrated by a visit to the Cairngorm plateau on a good day in the summer; today it is possible to count hundreds of walkers where only ten years ago there would only have been a handful. A similar situation has already arisen on Aonach Mor and Aonach Beag in the Nevis range. The increase is due to the ease of access provided by the skiing facilities which depend on summer income for their existence. A pro-active management policy for the high hills is an urgent issue.
Mr N. Hodgetts (Joint Nature Conservancy Council, Peterborough): Bryophytes in the new conservation agencies.
In the Environmental Protection Act 1990, the Nature Conservancy Council was reorganised into four separate bodies; English Nature, the Nature Conservancy Council for Scotland (soon to become Scottish Natural Heritage), the Countryside Council for Wales and the Joint Nature Conservation Committee (JNCC). The lower plant specialist post went to the Species Conservation Branch of the JNCC. The JNCC was set up to deal with Great Britain-wide issues that could not be dealt with effectively on a country-by-country basis. For example, legislative matters, setting standards for survey, monitoring and site selection, advice to government, liaison with national voluntary organisations (such as the BBS), coordinating conservation initiatives and international matters.
Within the JNCC, the Species Conservation Branch has special responsibility for legally protected species, reviewing the schedules of the Wildlife and Countryside Act 1981, Red Data Books, the National Vegetation Classification, the Invertebrate Site Register and lower plant conservation.
Current bryophyte work in the JNCC includes selection of rare species to recommend for addition to the schedule of fully protected species in the Wildlife and Countryside Act: 31 species have been submitted. The Red Data Book (RDB) project is well under way, and a RDB for bryophytes should be produced in 1993-4. Other proposed publications currently being worked on include SSSI selection guidelines for lower plants (in use but not yet published), field guides to selected groups, popular pamphlets to promote lower plants and management guidelines. Monitoring rare and threatened species is another aspect of the JNCC’s work. International groups with JNCC involvement such as the IUCN bryophyte specialist group and the European Committee for the Conservation of Bryophytes also have a number of initiatives under way.
The JNCC research programme has yet to be finalized but proposals include grazing experiments, climate change monitoring, ecological studies on oceanic bryophytes, the development of work on lower plant community types and ensuring adequate representation for bryophytes in the Nature Conservation Review.
Recent work in the country agencies has included bryophyte surveys in western oceanic woodlands and snow patch vegetation in Scotland. Proposed work includes further woodland surveys, monitoring projects and pollution studies. Initiatives such as the BBS Recorders Scheme and the activities of Plantlife are also likely to give bryophyte conservation a boost.
In conclusion, bryophyte conservation does not seem to have suffered significantly from the reorganisation of the NCC, and may actually benefit in the long run. In particular, the international scene is developing well, sites are being afforded protection specifically for their bryophytes and professional conservationists are coming to terms with the idea of conserving bryophytes, even embracing it enthusiastically.
Field excursion, 15 September 1991
The meeting visited two sites on the Magnesian Limestone east of Sheffield. Although the countryside here is less attractive than in the Peak District to the west, the limestone is relatively little known to bryologists and it supports some very interesting communities. The naturally dry climate was exacerbated on this occasion by two months of almost unbroken drought, and conditions were not good for field work.
The first site was at Anston Stones Wood between South Anston and Worksop. This important wood occupies a small steep-sided valley along the busy A57 road, and it is traversed by a railway line and a rather polluted stream! Nevertheless, the wooded banks, with low crags and limestone boulders, continue to support rich bryophyte communities.
Some species which are more characteristic of the wetter uplands manage to survive here, though not very luxuriantly. These include Scapania aspera, Apometzgeria pubescens, Distichium capillaceum, Tortella tortuosa and Neckera crispa. On the other hand there are also species present which have a broadly Mediterranean or Mediterranean-Atlantic distribution. Tortula marginata is one of these: it is a rarity in northern England, but it is a characteristic species of Magnesian Limestone woods. More surprising is the occurrence of Marchesinia mackaii. The station here is one of four recently discovered in the area where Yorkshire, Derbyshire and Nottinghamshire meet. The known population was seen and a new one located on the northern side of the wood. In both places it is accompanied by Cololejeunea rossettiana. Perhaps even more remarkable, in view of its great rarity in Britain, is the occurrence of Anomodon longifolius. This was relocated on the boulder where it was found a few years ago. There is just a single patch of it, associated with A.viticulosus, but it appears to be holding its ground.
Other locally rare species which were seen in the wood included Leiocolea badensis, Fissidens cristatus, Eucladium verticillatum, Gymnostomum calcareum, Homalia trichomanoides and Isothecium myurum. Amblystegium compactum, growing as it so often does on dark damp ledges at the bottom of an overhanging crag, attracted a lot of attention. A new record for the wood was Ephemerum serratum var. minutissimum, collected by Jeff Duckett on a damp path by the stream. Some members commented on the species which were not present. There was no Lejeunea (though this is known in small quantity on Magnesian Limestone over the Derbyshire border) and there was no Porella platyphylla. Epiphytes, in this dry and polluted district, were almost non- existent.
In the mid afternoon, a reduced party moved on to the Don valley at Sprotborough near Doncaster, to pay respects to Desmatodon cernuus at its best (and perhaps the only reliable) British site. A large quantity of the species was demonstrated on a railway embankment, the setae so dense in some of the patches as to colour the ground. Many of the capsules, however, had been lost, presumably grazed by invertebrates. This population is restricted to a small area covered with highly calcareous matter, about which there was much speculation. Further plants occur a little distance away on the bank of the riverside track. The locality is in a derelict area of old quarries, which are soon to be used for tipping, but the site on the railway embankment is presumably safe from destruction. Other species seen included Leiocolea badensis and Aloina aloides.