British Flora Research Articles

CYTOGENETIC VARIATION IN THE BRITISH FLORA: ORIGINS AND SIGNIFICANCE.

Cytogenetic variation in the British flora is discussed in relation to the taxonomy and evolution of species and to their distribution and past history. In polyploids there may be two or more cytotypes in Britain with different distributions and ecology, e.g. Empetrum nigrum and Hippocrepis comosa; alternatively only one cytotype is present in Britain, but it forms part of a wider polyploid pattern, the study of which may clarify past patterns of migration, e.g. Potentilla fruticosa and Sisyrinchium bermudiana. The study of polyploids may also have taxonomic significance, e.g. Cochlearia, Symphytum and Mentha. In some situations gene flow between polyploid levels takes place and may be in both directions. In other polyploid groups sexually sterile cytotypes may be maintained by vegetative reproduction, e.g. Ranunculus ficaria and Holcus mollis or by gametophytic apomixis. In some cases a polyploid and aneuploid series may be maintained in which all the components are fertile; this situation is discussed in relation to the genus Erophila. There has been considerable emphasis in the past in attempting to identify the genomic ancestors of allopolyploids; two British species, Spartina anglica and Senecio cambrensis are among the few examples of recent allopolyploids of known origin; in both cases formation has depended on the establishment of an introduced species as one parent. The significance of B chromosomes is discussed; although a range of British species contain B chromosomes it has only been possible to investigate their adaptive significance in one case. Interchanges exist in British species either in the heterozygous form, e.g. in Alopecurus species, where they can be identified by their meiotic consequences, or in the homozygous form, e.g. Epilobium sect. Epilobium species, where they can be identified by meiotic analysis of hybrids. The use of modern cytogenetic techniques including chromosome banding and in-situ hybridization and the investigation of characteristics such as infra-species variation in DNA amounts are discussed in relation to future cytogenetic investigations of the British flora.

POST-MEDIEVAL AND RECENT CHANGES IN BRITISH VEGETATION: THE CULMINATION OF HUMAN INFLUENCE.

Although measurable climatic fluctuation in temperature and wetness has occurred between A.D. 1700 and 1984, lack of earlier records and the complicating effects of human influence militate against detection of vegetational response in Britain. Vegetational change during this period is thus regarded as almost entirely the result of anthropogenic factors. Agriculture, now affecting c. 80% of Britain's surface, is overwhelmingly the most important such factor. Original vegetation had been mostly destroyed or heavily modified by a.d. 1700, notably through removal of the former forest cover and draining of lowland wetlands. The last 300 years have seen continuing development of farming and other land uses, to the point where very little natural vegetation now remains, and the main extent of semi-natural types is located in the uplands. Many distinctive semi-natural vegetation types actually created by man over several centuries of low input-low output management have decreased greatly since A.D. 1700, and rate of loss has even accelerated since 1940-1950. Only 5% of permanent lowland grasslands now remain agriculturally unimproved neutral grassland and only an estimated 20% of the extent of pre-1940 calcareous grassland is now assignable to that category floristically. Lowland acidic heath has declined by 78% in area since A.D. 1830, and by 40% of the 1950 level. Lowland rich fens are reduced to scattered remnants, the largest expanse (the East Anglian Fenland) having decreased from 3380 km2 in ad 1630 to 10 km2 in 1984. Forest cover was reduced to 5·4% by 1924, but has increased to 9·4%, largely through planting of alien conifers in upland districts. Since 1930 an overall 46 % of ancient semi-natural broadleaved woodland has been lost, largely by conversion to conifer plantation but also through grubbing out. An estimated 300000 ha of ancient semi-natural woodland remains, representing 14% of existing woodland and 1·3% of Britain's land surface. The total extent of hedges in England and Wales was reduced by an estimated 140000 miles (28%) between 1946-1947 and 1974. Urban-industrial growth, including roads, railways, water-use, mineral extraction and energy generation, has directly obliterated large areas of vegetation and caused chemical pollution. Waste ground associated with these activities often develops semi-natural plant communities through spontaneous succession, and may become floristically rich. Pollution affects especially fresh water through both toxic residues and eutrophication from nutrient enrichment (including run-off of agricultural fertilizers). Atmospheric pollution causes acid deposition especially damaging locally to the lichen flora, and induces biological changes in lakes and rivers in districts of acidic rocks. Recreational pressures have caused increasing disturbance to vegetation locally, and less directly through working of Sphagnum bogs for horticultural moss litter and surface mining of limestone pavements for rockery stone. Collecting of plants as a hobby has also brought some species, notably rare ferns, orchids and'alpines'to dangerously low population levels, or even local extinction. The British flora has been profoundly modified by human influence. Only 19 vascular species are known to have become extinct, but many have declined greatly during the last 300 years and, for species in some habitats, especially semi-natural grasslands, rate of decrease has accelerated since 1940. Of 317 nationally rare species 117 (37%) have declined by at least 33 % since 1930. Human agency has also introduced to Britain at least 239 plant species which now grow wild, and extended the distribution of at least 363 others. Some are still increasing but others, notably weeds of arable land, are decreasing again. Conservation measures include setting up nature reserves to contain adequate representation of all semi-natural and natural vegetation types, and of populations of all native plant species. The aim is to give protected area status to c. 10% of Britain's surface through appropriate control and management designed to maintain or enhance the nature conservation interest. At present c. 1% is managed as nature reserve of one or other category and another 6% has been designated as Sites of Special Scientific Interest. Wild plants are now legally protected against unauthorized picking and uprooting, and 61 rare species are protected by special measures. Wider environmental conservation measures to reduce damaging human impact on vegetation and flora include inputs to and by local authorities and their planning system, persuasion of landowners and resource managers, and pollution control; supported by an educational and publicity programme, and by relevant research and information.

THE FLORA AND VEGETATION OF BRITAIN: ECOLOGY AND CONSERVATION.

A main aim of studies of the British flora in future must be ecological, with plant ecology developed as a multidisciplinary and experimental science which has as its primary purpose the understanding of vegetation. The response of species to environment is largely mediated through the response of vegetation. It is essential to have an accepted and widely understood classification of British vegetation. Destruction of the more natural types of vegetation, with accompanying loss of species, should be a matter of national concern as many communities are irreplaceable. Their loss represents irreversible damage to our cultural heritage and a deterioration of the quality of our environment. Ecological understanding of vegetation is necessary to ensure that conservation achieves its primary purpose.

Lichens of Colonsay

SynopsisThe results of eight days' recording and collecting of lichens on the island of Colonsay are presented. A wide range of habitats were studied but particular attention was paid to the two relict oak-woodlands and some areas of calcareous machair. An impressive total of 342 lichen taxa was recorded, and two species were added to the British flora.

Variation in genome size—an ecological interpretation

Previous attempts to explore the significance of variation in genome size have involved comparisons with respect to life history1–4, taxonomic and evolutionary affiliations5–9 and geographical distribution10,11. Here we examine variation in the British flora. Large genomes are particularly associated with Mediterranean geophytes and grasses in which growth is confined to the cool conditions of winter and early spring. We suggest that large genomes have evolved under circumstances in which growth is limited by the effect of low temperature on rates of cell division and are part of a mechanism whereby growth at low temperature is achieved by rapid inflation of large cells formed during a preceding warm dry season. Where moisture supply allows growth to occur in the summer, temporal separation of mitosis and cell expansion confers no advantage and the longer mitotic cycle of large cells is likely to restrict rates of development; here the effect of natural selection has been to reduce cell and genome size.

The effects of host‐plant distribution and local abundance on the species richness of agromyzid flies attacking British umbellifers

Abstract. 1. The number of agromyzid species (Diptera: Agromyzidae) attacking British Umbelliferae generally increases with the size of the geographic range of the host, measured as occupied 10 km squares in the Atlas of the British Flora (Lawton & Price, 1979).2. In the present study we tried to explain the large, residual variation in this species—area relationship using two new variables, namely the local abundance of the host plant, and the number of habitats within which it grows.3. Local abundance was estimated from eight floras that map plant distributions within English countries by tetrads (2 times 2 km squares). Local abundance was defined as:Total number of occupied tetradsTotal number of available tetrads within occupied 10 km squares4. The number of habitats occupied by each host plant was taken from the only county flora to record plant habitats objectively, that for Warwickshire.5. We expected to find a correlation between local abundance and the residuals from the national species—area relationship, with locally scarce plants having fewer agromyzids than expected from the sizes of their national ranges, and vice versa.6. What we found was that size of geographic range and local abundance were highly correlated; hence their relative contributions to agromyzid species richness were difficult to disentangle. Residuals from the national species—area relationship were positively correlated with local abundance, but the relationship marginally failed to achieve statistical significance (P= 0.06).7. In contrast, the number of habitats occupied by each species of umbellifer in Warwickshire had a marked effect upon agrornyzid species richness, with plants that grow in more habitats supporting more species of insects. Not surprisingly, local abundance and number of habitats occupied were highly correlated.8. Lawton & Price's observation that aquatic umbellifers are faunally impoverished now emerges as part of the general effect of number of habitats occupied by the host plants on agromyzid species richness.9. Once the number of habitats occupied by each host plant in Warwickshire was entered into a multiple regression, the effect of size of host geographic range on agromyzid species richness was no longer statistically significant.10. A combination of the number of habitats occupied, and leaf‐form of the host (the latter taken from Lawton & Price, 1979), explains 61% of the variation in agromyzid species richness on British Umbelliferae.

THE LATE DEVENSIAN VEGETATIONAL HISTORY OF THE WHITLAW MOSSES, SOUTHEAST SCOTLAND

SUMMARYLate Devensian Late‐glacial deposits are described from the Whitlaw Mosses, near Melrose, Roxburghshire (now Borders). Pollen diagrams and macro fossil lists are given for the bottom sediments of Beanrig Moss and Blackpool Moss, two small fens lying in hollows in the undulating boulder clay of Tweeddale. The succession of taxa through the sediments indicates interstadial conditions followed by stadial conditions.Critical determinations of certain microfossil and macrofossil indicator taxa, permits the identification of certain plant communities. These are as follows: Communities identified from within the stadial are;(1) bare‐ground communities of open, wind‐exposed areas with Artemisia cf. norvegica and Papaver spp. of the section scapiflora as the main indicator types;(2) bare‐ground communities in sheltered areas of long snow‐lie with such species as Salix herbacea, Polytrichum norvegicum and P. alpinum.The main communities identified in the interstadial are as follows:(1) scrub with abundant Juniperus and sparse tree birches (e.g. B. pubescens);(2) base‐rich, well‐drained short turf with abundant Helianthemum;(3) damp, tall‐herb meadows in which Rumex acetosa is important;(4) dwarf‐shrub heath with Dryas octopetala and Betula nana;(5) open‐ground communities with Artemisia spp. and Hippophaë.Communities identified from both the stadial and interstadial are:(1) short‐turf calcareous flushes or springs with Selaginella and various mosses;(2) fens and marshy lake margins with, e.g. Homalothecium nitens.Several taxa have not hitherto been found in the Late Devensian of the British Isles, amongst which are Artemisia cf. campestris, A. sect. dracunculus, A. cf. maritima s.l., Gypsophila repens/fastigiata, Hedysarum cf. hedysaroides, Minuartia rubella, Rhacomitrium cf. canescens and Vactinium vitis‐idaea. The identification of the pollen grains and macro fossils is discussed and comments are made on the biogeographical and ecological implications of the records, especially of those species which are now no longer part of the British flora.

The authorship of Plantae rariores agro Dunelmensi indigenae

Stephen Robson (1741–1779) and his nephew Edward Robson (1763–1813) were both Quaker botanists who lived in Darlington, County Durham. Stephen is best known for his British Flora published in 1777, and Edward had a considerable reputation as a particularly competent botanist. Some confusion seems to exist regarding the authorship of a rare plant list for Durham, Plantae rariores agro Dunelmensi indigenae, attributed to Stephen Robson in most recent bibliographical literature. This paper re-examines the evidence for the authorship of this list and suggests that although Stephen Robson produced a short list of local plants the longer and more critical list, Plantae rariores … was compiled by his more knowledgeable nephew Edward.

Species for biomass production in north western European conditions

SYNOPSIS The British flora which is representative of a large area of western Europe consists of approximately 3,500 species from 146 families. This list has been scanned for species suitable for biomass production. A number of families, notably the Leguminosae, Rosaceae and the Salicaceae, contain potentially suitable species which have not hitherto been investigated. Because of the importance of maintaining a self-supporting, and hence a renewable system, woody plants have a particular advantage. Financial considerations may be a constraint on long term investment, and hence short rotation forestry is considered a promising choice for the production of a renewable source of energy.

Buddleia davidii in Britain: History and development of an associated fauna

Buddleia davidii was introduced to Britain in the 1890s and began to colonise waste land and building sites in the 1930s. It now occurs in almost every town, especially on calcium-rich soil to which it is highly tolerant. No native or introduced plant produces flowers that are so attractive to butterflies and other insects. Eleven species of Lepidoptera caterpillars are known to feed on buddleia leaves or flowers, among them Cucullia verbasci, previously restricted to the Scrophulariaceae. The shrub is in every sense a useful introduction, exploiting a previously unfilled niche, and its development of an associated fauna as well as the attractiveness of its flowers to nectar-feeding insects makes it a welcome addition to the British flora.

British bryophyte floras and check-lists, 1954–1978

British bryophyte floras and check-lists, 1954–1978

History of the British Flora, 2nd Edition

History of the British Flora, 2nd Edition

Algae of saltmarshes on the South and Southwest coasts of England

During a short excursion the algal vegetation of three saltmarshes along the Bristol Channel and two on the English south coast was investigated. The results are compared with data collected in Norfolk and in the Wadden area and show that the algal vegetation along the Bristol Channel is a typical estuarine one. The southern English marshes are rich in algal species and communities. Cladophora globulina (Kutz.) Kutz. is reported as new to the British marine flora.

W. K. Martin The concise british flora in colour

W. K. Martin The concise british flora in colour

Land Reclamation and the Botanical Significance of Some Former Mining and Manufacturing Sites in Britain

Whilst major new industrial development sometimes poses a threat to scenic values and ecologically important habitats, it is also evident that industry has contributed significantly to the present-day biological resources of the British Isles. In particular, several former mineral-extraction sites have been maintained and developed specifically for the security and management of wildlife, and now constitute important habitats for the protection and survival of less-common members of the British flora. Several locations have even been successfully defended on biological grounds against proposals to reutilize them for disposing of industrial wastes and domestic refuse.

Life-history and culture of Gracilaria foliifera (Rhodophyta) from South Devon

Three species of Gracilaria, G. foliifera (Forsk.) Børg., G. verrucosa (Huds.) Papenf., and G. bursa-pastoris (S. M. Gmel.) Silva are recognized from the British flora (Parke & Dixon, 1976). In Britain G. verrucosa is widely distributed, although not common, whereas the other two species are rare and their distribution restricted (Newton, 1931). G. foliifera was described from the Red Sea as Fucus foliifer Forsk. (Børgesen, 1932). Plants referable to this species are now reported from various parts of the world, including both the eastern and western coasts of the north Atlantic (South & Cardinal, 1970; Taylor, 1957, 1960). However, considerable variation exists within species of Gracilaria (e.g. May, 1948), thus delimitation of species is often extremely difficult. Gracilaria foliifera from Britain (Fig. 1 A) is similar morphologically to the original material of Fucus foliifer as illustrated by Børgesen (1932, fig. 1), and therefore, we have limited our consideration to G. foliifera as it occurs in Britain (also see Harvey, 1846, pl. 15). However, little information is available on G. foliifera from the British Isles, and in the present instance we have investigated the life history of this alga in culture together with preliminary results on growth in small-scale tanks with running sea water.

History of the British Flora

History of the British Flora

REVIEWS

Book Reviwed in this article: The History of the British Flora. By Sir Harry Godwin. The Euphorbiaceae of Borneo. By H. K. Airy Shaw. Ecology of Plants in the Tropics. (Studies in Biology No. 58, Institute of Biology.) By Daniel H. Janzen. Pacific Plant Areas. Volume 3. Ed. by M. M. van Balgooy. The Liverworts of New Zealand. By K. W. Allison and John Child. Paleoecology of Terrestrial Plants. Basic principles and techniques. By V. A. Krasilov. Plant Propagation, 3rd edn. By Hudson T. Hartmann and Dale E. Kester. The Lytic Compartment of Plant Cells. By PH. Matile. Plant Pathogenesis. By H. Wheeler. Phytotronics in Agricultural and Horticultural Research. Ed. by P. Chouard and N. de Bilderling. Phytoplankton. By A. D. Boney. Krankheiten und Schädlinge an Getreide und Mais. By C. Buhl.

Forests and wildlife

Woodlands quite quickly became the most extensively occurring vegetation after the last glacial period so it is not surprising that a large part of the British flora and fauna consists of woodland species or species which in some way are dependent on trees. The biological bases for sustaining the numbers and variety of woodland wildlife are described as are the habitats provided by woodlands. Examples are given of the numbers of species of different groups of organisms that occur in woodlands and the relationships between them. The wildlife of broadleaf and conifer woodland are discussed and examples given of the characteristic wildlife of these main woodland types. Finally, the effects of past and present forestry practices on forest wildlife are considered.

New and interesting marine algae from the Shetland Isles

Investigations in the Shetland Isles in the summer of 1973 have produced many new algal records for the area, including several of particular interest for the British flora in general. Those discussed here are Bolbocoleon piliferum N.Pringsh., Blastophysa rhizopus Reinke, Ochlochaete ferox Huber, Asparagopsis armata Harv. (the Falkenbergia-phase occurs in Shetland) (by I. Tittley); Audouinella spetsbergensis (Kjellm.) Woelk., Kallymenia reniformis (Turn.) J. Ag. (with impacted cystocarps and carpospores developing in situ) (by M. Guiry); Cladophora pygmaea Reinke (new to the British Isles) and Endodictyon infestans Gran (suggested to be a plethysmothallus of Ectocarpus) (by G. Russell).