Location Of Refugia Research Articles

Restricted gene flow between Holothuria scabra (Echinodermata: Holothuroidea) populations along the north-east coast of Australia and the Solomon Islands

To describe patterns of gene flow for the fished holothurian species Holothuria scabra 17 to 141 individuals were collected from 8 populations from north-east Australia, the Torres Strait, and the Solomon Islands. Samples were investigated by allozyme electrophoresis of 7 polymorphic loci. Cluster analyses using Rogers' genetic distance identified 3 distinct groups of populations from the north-east coast of Australia, representing samples from the 3 regions Hervey Bay, Upstart Bay and Torres Strait. Populations in the latter region were closely connected to those from the Solomon Islands. F-statistics indicated restrictions in gene flow (average genetic variation between popula- tions, FST = 0.088). Hierarchical analyses revealed that 94.7% of the variation was within sampling locations. Approximately 77% of the variance among populations was due to differences between regions, and 23% within regions (most of the latter caused by differences between the 2 Solomon Island populations). Mantel's tests indicated that a high proportion of the variation in genetic dis- tances along the north-east coast of Australia was explained by isolation by distance (Mantel's nor- malised Z = 0.88). This proportion reduced when the Solomon Islands were included (Z = 0.65). The detection of separate stocks along the north-east coast of Australia is an important finding that has significant consequences for the development of sustainable management plans for this species. Low dispersal may significantly reduce recovery of overfished areas if no local refugia are provided.

Comment on D. M. Wilkinson (1997). ‘Plant colonization: are wind dispersed seeds really dispersed by birds at larger spatial and temporal scales?’

(it was probably rightly excluded, owing number of pollen grains counted in each (1997). ‘Plant colonization: are to ‘its water dispersal strategy’ (Wilkinson, spectrum), and so is inherently as inwind dispersed seeds really 1997: 62; but see Chambers & Elliott, 1989)); consistent measure; whereas the ‘rational dispersed by birds at larger spatial whereas had Corylus been excluded (on the limit’ (the rise to higher percentage values) and temporal scales?’ grounds of incomplete separation from Myis still a relative, rather than an absolute,

Holes and the sums of parts in Ghanaian forest: regeneration, scale and sustainable use

SynopsisThe current state of Ghana's forest is summarised. Considerable changes have occurred in the last decade, since Hall & Swaine's account and classification, due mainly to fire and logging. The requirements and potential for sustainable forest use are explored through a summary of patterns of regeneration, and of local and national distribution of individual species.Incisive indices of forest quality and condition are vital to good forest management. Various forest quality indices, summarising different properties of the plant community, are examined. These indices gloss over the statistically noisy behaviour of single species in small forest areas. The indices are: Forest Type – Hall & Swaine's forest ordination and classification; a Pioneer Index (PI) revealing the balance of ‘regeneration guilds’; a Genetic Heat Index (GHI), based mainly on the rarity value (Star rating) of all forest species, highlighting ‘hotspots’; and an Economic Index (EI) based on the concentration of common species (‘reddish Stars’) threatened by exploitation. Guild and Star are defined for all species and encapsulate trends of local and of global distribution and ecology. The national and local patterns and response to disturbance of the indices derived from the representation of these various guilds and stars are discussed.Scale is crucial to all discussions. A strictly hierarchical model of forest ecology/biogeography is less suitable than a continuum-of-significant-scale, and non-hierarchical model. For instance, refugia are usually perceived as discrete biogeographical units. However, major biological ‘hotspots’, which are often described as refugia and attributed to Pleistocene climatic variation, differ only in position along a continuum of scale from mini-refugia as small as individual plants. The biogeographic Dahomey gap has much in common with a canopy gap, with scale as the main distinction.There are conspicuous trends across Ghana's forests in the abundance of pioneer, rare or economic species. These differ in detail, but ‘hysteresis’ – the forest memory – and other factors related to the concept of refugia apply to all these aspects of forest quality. Major hotspot refugia are crucial to the national framework of biodiversity, but local refugia, between the size of individual plants and single forest blocks, are crucial to local regeneration and sustainable use, as they shape the probability cloud which defines the anatomy of and processes within each species' range. Short-term sustainable use depends on local refugia; longer-term sustainability requires maintenance of refugia on a wider range of scale.The implications of these phenomena to forest management are discussed in conclusion. Forest health is a multi-scale, but particularly a broad-scale, phenomenon. Local processes like the regeneration of forest under canopy gaps, are subordinate to larger-scale patterns and not determined simply by a match between species physiology and gap dynamics or patterns in the physical environment. Success of a species in a certain landscape does not automatically imply the species can be successful in similar conditions in a different landscape elsewhere: the context of the landscape in terms of the broader mosaic is also important. Managers, whether of plantations or natural forest, need to monitor, plan, and protect indigenous species on all scales. Forest managers need also to be aware of and work with the ‘forest memory’ factor. Protective measures for rare or economically threatened species should be based on current refugia and, like them, be arranged on all scales from single trees to large forest blocks.Researchers need to pay more attention to processes between the ecological and biogeographical, if they are to provide information for managers which has a useful synergy with existing types of data. Exploration is needed of the anatomy of the ‘probability clouds’ defining the statistics of dispersal and regeneration of rare or threatened species with respect to parent populations. What are the chances of a mahogany establishing at a point 500 metres from a mother tree? How is this statistic influenced by soil type? There is much to be learnt on scales between the canopy and the Dahomey Gap.

A Report on the 1991 Sino-American Bryological Expedition to Guizhou Province, China: New and Noteworthy Additions of Chinese Moss Taxa

The preliminary study of some 500 moss specimens collected in 1991 fromfive localities in Guizhou Province, China, has yielded 16 genera and 61 species representing new additions to this little known provincial moss flora. Of these, 12 are new records for southwestern China and four are new to mainland China. Neckera undulatifolia (Tix.) Enroth is new to China (including Taiwan). Symblepharis guizhouensis Tan et al. is a new name proposed to replace S. breviseta Bartr., an illegitimate homonym, and Orthothecium hyalopiliferum Redfearn & Allen is reduced to the synonymy of 0. intricatum (Hartm.) B.S. G. Bryologically, Guizhou is one of the least known provinces in China (Wu 1984). Situated roughly between 104-1090E and 25-290N, the province has a total land area of about 176,128 km2, slightly larger than the American state of Colorado. The topography is mountainous and dissected by deep gorges and narrow valleys. The result is a broad altitudinal range from 137 to 2,900 m (Xiong 1992). Equally diverse are the geology and soil types of the province, with more than two thirds of the land consisting of limestone substrates (Hou 1956). The climate of Guizhou province is basically subtropical, becoming temperate near its northern border and summits of high mountains. Annual precipitation is between 900 and 1,500 cc, with the western part drier than the eastern and southern parts. The vegetational history ofGuizhou province was reviewed by Yang (1985). Its plant fossil records reveal a long history of succession from the Paleozoic pteridospermous flora to modern angiospermous plant communities. The complex geomorphology of the province and relatively warm Quaternary climate produced local refugia for the survival of several relictual or monotypic plant taxa such as Gingko biloba, Cathaya argyrophylla, Fokienia hodginsii, and Davidia involucrata. Although the province is very rich in vascular plant resources, little is known about its bryophytes. Based on the knowledge of modern Guizhou seed plants, the province occupies a transitional position between the Sino-Himalayan flora of southwestern China and Sino-Japanese flora of central and eastern China (Ying et al. 1991). Our bryological investigation supports this observation. Remarkably, the province can harbor tropical, temperate, and boreal moss taxa, such as Homaliodendron exiguum, Hookeriopsis utacamundiana, Aulacomnium heterostichum, Pleurozium schreberi, and Hylocomium splendens, all within a single mountain system. Its flora also has a significant mix of widespread eastern Asiatic elements and endemic southwestern Chinese species. Early collectors of Guizhou mosses were mostly French missionaries (Koponen 1984; Wang 1935). Not surprisingly, the first report of Guizhou bryophytes was published by two French bryologists, J. Cardot and I. Theriot, in 1904. This was followed by Theriot (1907, 1908, 1909, 1911). Other important publications on Guizhou bryophytes are by Brotherus (1929), Reimers (1931), and Bartram (1935). In recent years reports of Guizhou bryo' Contribution to the bryoflora of China no. 6. 0007-2745/94/127-137$1.35/0 This content downloaded from 207.46.13.51 on Sun, 19 Jun 2016 06:10:08 UTC All use subject to http://about.jstor.org/terms 128 THE BRYOLOGIST [VOL. 97 phytes were published by Zhong and Xiong (1985, 1990a,b), Xiong (1992), Lin (1985, 1987, 1989), and Lin and Zhou (1990, 1991). An incomplete checklist of Guizhou mosses prepared by Zhong and Xiong (1989, 1990a) listed 389 species in 157 gen-

Ordovician-Silurian mass extinction and recovery: coral faunas in the east-central United States

Three successive coral faunas that are involved in the Ordovician-Silurian mass extinction and recovery occur in latest Ordovician (Richmondian-Gamachian) to earliest Silurian (early Llandovery; Rhuddanian) strata of the east-central United States. The Richmondian fauna comprises typical cratonic North American Late Ordovician corals. In the Cincinnati Arch region, these belong to the Richmond Province and include massive stauriids (e.g., Favistina), sarcinulids (e.g., Foerstephyllum, Calapoecia), and common tetradiids. In the upper Mississippi Valley region, corals belong to the Red River-Stony Mountain Province and include the streptelasmatid Salvadorea. The disappearance of typical Ordovician-type coral faunas from the interior of eastern North America was related to habitat loss resulting from progradation of the Queenston delta and regression of the epeiric sea during a major glacio-eustatic drop in the late Richmondian.The succeeding fauna of Gamachian to early Rhuddanian age represents the Edgewood Province. The solitary rugosan Streptelasma is dominant; colonial rugosans are rare and are all fasciculate. The principal tabulates are Paleofavosites, Propora, and Halysites; sarcinulids are absent. Rare tetradiids (Rhabdotetradium) are among the youngest representatives worldwide of an important Ordovician order. The Edgewood fauna includes first occurrences of typical Silurian taxa: the earliest North American halysitine (Halysites), the oldest definite plasmoporid (Plasmopora), and the earliest known pycnostylid (Pycnostylus). The striking difference between Richmondian and Edgewood faunas in the east-central United States reflects, at least in part, a hiatus between Richmondian and Gamachian deposition. Corals were introduced to the Edgewood Province from the continental margin, or were derived from forms previously restricted to the continental margin. This occurred during minor transgressions from the south, as sea level fluctuated during a regressive phase corresponding to the Gamachian glacial maximum. Immigration was evidently related to shifts of suitable habitat areas during a time of depressed temperatures. Edgewood corals dispersed farther northward during the early phase of the major latest Gamachian to Early Llandovery transgression associated with deglaciation.Corals are uncommon in late Rhuddanian strata immediately above those containing the Edgewood fauna. This Silurian fauna includes the solitary rugosans Rhegmaphyllum, Dinophyllum, Dalmanophyllum, and Cyathactis?, which were not derived from Edgewood taxa. Colonial rugosans are absent. The tabulates belong to Paleofavosites, Propora, and Halysites, the dominant colonial genera in the Edgewood fauna. At least some of the species were likely derived from Edgewood forms; others may have been introduced from elsewhere, or perhaps were derived from species in other areas. A slight stratigraphic overlap of several Edgewood and Silurian species is known at one locality, but the faunal change is otherwise abrupt. The changeover from Edgewood to Silurian faunas took place as water depth and temperature were generally increasing during the Rhuddanian. However, corals of the Silurian fauna appear above intraformational channels in one area and above unconformities or formational boundaries elsewhere, suggesting that the change occurred during an intervening regressive event. It is inferred that as areas in the east-central United States became inhospitable, geographic ranges of Edgewood corals were reduced. Most species became extinct; some colonial corals apparently underwent rapid evolution, probably in small populations. The descendants dispersed and new immigrants arrived as suitable habitat areas expanded when the Early Llandovery transgression resumed. A few Edgewood colonial species survived for a short time, evidently in local refugia. Unlike the colonial corals, all solitary forms known from the Silurian assemblage were immigrants. Corals of the Silurian assemblage probably favored somewhat deeper water than those of the Edgewood Assemblage.

Cytogeographic races of Arctagrostis latifolia (Poaceae) in Alaska

Chromosome counts were obtained on 117 plants of the circumpolar grass Arctagrostis latifolia (R. Br.) Griseb. collected across mainland Alaska. Three chromosome races were found in the state. A widespread distribution was indicated for the tetraploids (2n = 28) and octoploids (2n = 56) and a limited distribution for the hexaploids (2n = 42), heretofore unreported for North America. Both tetraploids and octoploids appeared to be well represented through the boreal interior and arctic, unglaciated refugia of Alaska. Only tetraploids were found on the heavily glaciated terrain of southcentral Alaska. Six hexaploid counts were obtained on plants collected from two locales at the ecotone of glaciated and unglaciated areas. Cytotype distribution was interpreted as indicating a greater mobility for the tetraploid race, better enabling it to occupy deglaciated terrain and other disturbances, and the possibility of survival of the tetraploid in local refugia within the extensively glaciated southcentral region. The data provided support for the inclusion of different chromosome races within a single taxon. Key words: refugia, cytotype, polyploidy, recolonization.

Effects of pollution on marine gastrotricha in the northwestern Adriatic Sea

The barrier islands and coast south and east of Venice, Italy, were sampled in parallel to the work of Schrom two decades ago. Where he found 49 site records for 24 species of gastrotrichs at 8 sites, 5 littoral and 3 shallow sublittoral, we found 5 site records for 2 species at 9 sites, 5 littoral and 4 shallow sublittoral. We had no site records from littoral sites; one species, Dolichodasys elongatus, occurred at all sublittoral sites. From other locations (n=15) in our present survey of the Italian coastline, where we have paired littoral: sublittoral sites, we have found 6.7 (±0.9) species in the former and 8.0 (±0.9) in the latter. The absence of gastrotrichs in samples from all five littoral sites and the dominance of D. elongatus in sublittoral sites is clear evidence as to the severity of pollution in this area. However, five species were found in a sample from the top of a longshore bar at one location, indicating that a type of local refugium exists from which future recolonization of the remaining habitat could proceed, if the input of pollutants can be reversed.

Terrestrial Mollusks of Attu, Aleutian Islands, Alaska

Seven species of land mollusk (2 slugs, 5 snails) were collected on Attu in July 1979. Three are circumboreal species, two are amphi-arctic (Palearctic and Nearctic but not circumboreal), and two are Nearctic. Barring chance survival of mollusks in local refugia, the fauna was assembled overwater since deglaciation, perhaps within the last 10 000 years. Mollusk faunas from Kamchatka to southeastern Alaska all have a Holarctic component. A Palearctic component present on Kamchatka and the Commander Islands is absent from the Aleutians, which have a Nearctic component that diminishes westward. This pattern is similar to that of other soil-dwelling invertebrate groups.

THE LOCATION OF REFUGIA OF CORYLUS AVELLANA L. DURING THE WEICHSELIAN GLACIATION

SummaryA survey was made of all existing radiocarbon dates relating to the Corylus rise in Europe in order to find the possible areas of refugia of Corylus during the Weichselian glaciation. Using the radiocarbon dates an isochron map was drawn which indicated areas of refugia off the west coast of the British Isles, south‐west Scandinavia and in south‐western Europe. The possible routes of migration of Corylus are indicated on this. On the basis of the radiocarbon dates the rates of migration of Corylus along the possible routes have been calculated and show that migration from northern refugia was faster than that from southern refugia.The climatic and edaphic conditions in the suggested refugia during the Weichselian glaciation and their importance in relation to the survival of Corylus are discussed. The number of radiocarbon dates is inadequate for definite conclusions to be drawn on the location of refugia and so the need for an extensive programme of radiocarbon dating of important pollen strati‐graphic events in Europe is stressed.