Factors influencing the distribution of aquatic plant communities in Irish canals

Terrestrial tardigrades are often found in the lichens and mosses growing on trees and rocks. The assertion that tardigrades in these habitats are very patchy in their distribution has rarely been backed by quantitative sampling. This study assesses spatial variability in tardigrade populations inhabiting small patches (0.1 cm² to over 5 cm²) of moss and lichen on trees and rocks at three sites in the United States of America. Tardigrades were collected from four replicate rocks in the Ouachita Mountains of Arkansas, with 30 lichen patches collected on two adjacent boulders and 20 moss patches on a second pair of boulders. In Fort Myers and in Citrus Springs, Florida, 30 lichen patches per tree were collected from two pairs of trees. The tardigrades in each sample were extracted, mounted, identified, and counted. The variation in tardigrade abundance among lichen or moss patches within rocks or trees was very high; the only consistent pattern was that very small patches usually lacked tardigrades. Tardigrade diversity and abundance also varied greatly within sites when lichens and mosses of the same species from different rocks and trees were compared (in the most extreme case one tree had numerous individuals of two tardigrade species present while the other had almost no tardigrades). The results of this quantitative sampling support the assertion that tardigrades are very patchy in distribution. Given the considerable time investment required for the quantitative processing of tardigrade samples, this high spatial variability in tardigrade diversity and abundance requires that researches testing ecological hypotheses about tardigrade abundance check variability before deciding how many samples to take.     

Interspecific Association and Substrate Specificity in Tardigrades from Florida, Southeastern United States

The distribution of terrestrial tardigrades in the Gulf Coast states of the United States is poorly known. Only one species has been reported in Florida. In this study moss, liverwort, lichen and fern samples (47 identified species) from trees and shrubs were collected from all 67 Florida counties. These samples contained 20 species of tardigrade. All possible pairs of tardigrade species and tardigrade and substrate were tested for interspecific association. Only three significant negative and one positive interspecific association between tardigrades were detected. Evidence for substrate specificity was weak. Although some tardigrade species were significantly associated with mosses or foliose lichens in general, no significant association between a tardigrade species and a substrate species was detected.     

Two new species of tardigrades from Short Mountain, Tennessee, U.S.A.

Tardigrades were collected from three seepage spring sites at 549m on Short Mountain, Cannon County, Tennessee. Three terrestrial samples and three aquatic samples were taken monthly from each site. Terrestrial samples included mosses and lichens from rocks and fallen trees; one sample of leaf litter was also collected from two of the sites. Aquatic samples included sediment, decaying leaf litter, and aquatic plants. Specimens of tardigrades were mounted on individual slides in Hoyer's medium. Species were identified and photographed using phase and differential contrast microscopy. Twenty-eight species representing 13 genera were recorded: Pseudechiniscus, Echiniscus, Doryphoribius, Ramazzottius, Hypsibius, Isohypsibius, Dipliascon, Platicrista, Itaquascon, Murrayon, Macrobiotus, Minibiotus , and Milnesium. One of the Pseudechmiscus species and an Isohypsibius species were new to science and are described in this paper.     

Tardigrades of Louisiana and Arkansas, United States of America

The distribution of tardigrades in the states of the southern United States is poorly known. There are no published records from the state of Louisiana, while in Arkansas only one species has been reported. Samples of mosses and lichens from trees and rocks were collected from three sites in central and southern Louisiana and six sites in western Arkansas. Leaf litter samples were collected from one site in Louisiana. Nine species of tardigrade were found in Louisiana and 22 in Arkansas. The number of species per sample ranged from one to six.     

Ecological Distribution and Community Analysis of Tardigrada from Choccolocco Creek, Alabama

A seasonal survey of tardigrade populations in the riparian zone of the Choccolocco Creek, Alabama, was undertaken from August 1994 through December 1995. Six sites within the riparian zone were sampled in different portions of the creek. At each site, 3 trees with cryptogams were sampled six times during survey period. From a total of 108 samples, 1,588 tardigrades were extracted and individually mounted on slides in Hoyer's medium. The community was dominated (86%) by specimens in the genus Macrobiotus. One species of Echiniscus was new to science and will be described in a separate paper. No significant difference was found between tardigrade occurrence (total number of individuals) and season, moss genera, or tree species. However, there was a significant relationship between the number of tardigrades and site, indicating the need for additional replicate samples. Simpson's and Shannon-Wiener's species diversity indices indicated that species richness and evenness were low. Jaccard's and Standard's community similarity indices suggested that the communities within the riparian zone were dissimilar along Choccolocco Creek.     

Population density and species composition of moss-living tardigrades in a boreo-nemoral forest

This study investigates for the first time the tardigrade fauna in a variety of different mosses from a coniferous forest and an adjacent clear-cut area in southern Sweden. Tardigrades were found in a majority of the samples. Sixteen species were recorded, of which the cosmopolitan species Macrobiotus hufelandi was the far most common. Some mosses, particularly species with "wefts" growth form, contained more tardigrades than other mosses, indicating that growth form may have an impact on tardigrade abundance. Mosses of the same species collected from a forest and from a clear-cut, respectively, did not show a general trend in the overall abundance of tardigrades, but the forest tended to contain more species. Five species of tardigrades ( Murrayon dianae, Isohypsibius sattleri, Platicrista angustata, Diphascon belgicae and Diphascon pingue ) never previously reported from Sweden were recorded.     

The Ecological Distribution of Tardigrades in Newfoundland

The ecological distribution of tardigrades on the island of Newfoundland, Canada is greatly affected by both abiotic and biotic factors. Altitude and type of bedrock are major determining factors in tardigrade distribution while both moisture content of the environment and rate of dessication of the mosses and lichens in which they live appear to be other factors contributing to their distribution. A number of cases of apparent competitive exclusion and inter-specific competition have been noted which probably also affect tardigrade distribution.     

The Tardigrades of Emilia (Italy). III. Piane di Mocogno (Northern Apennines)

Samples of leaf litter, mosses and lichens were collected in a beech forest at Piane di Mocogno (Emilia, Italy), 1200 m asl. The tardigrade community of the leaf litter was similar to that found in this substrate in Italy and in the U.S.A. At Piane di Mocogno the species association within the leaf litter was different from that in mosses and lichens (which have similar fauna), confirming that very different communities characterise different substrates such as leaf litter and mosses. During this faunal analysis, six species of tardigrades were found for the first time in this area. The presence of Microhypsibius bertolanii (first record in leaf litter and in Italy) and Eohypsibius nadjae are note worthy. Ornamented eggs in an exuvium of Hypsibius cf.scabropygus were also recorded for the first time.     

Effects of river level fluctuation on plant species richness, diversity, and distribution in a floodplain forest in Central Amazonia

River levels in Central Amazonia fluctuate up to 14 m annually, with the flooding period ranging from 50 to 270 days between the rising and falling phases. Vast areas of forest along the rivers contain plant species that are well adapted to annual flooding. We studied the effect of flooding level on tree species richness, diversity, density, and composition in lake, river, and stream habitats in Jaú National Park, Brazil. 3051 trees >10 cm diameter (at 1.3 m diameter at breast height, dbh) were measured and identified in 25 10 m × 40 m randomly selected plots in each habitat. Ordination methods and analysis of variance results showed that forested areas near lakes had significantly lower species richness of trees than riverine and streamside habitats. Plot species richness and diversity were strongly negatively correlated with the water level and duration of flooding. The drier (stream) habitat had more total species (54 species of trees) and more unique species of trees (6 tree species) than the riverine (52 tree species; 3 unique species) and lake (33 tree species; 3 unique species) habitats. Species composition overlap among habitats was surprisingly high (42.6–60.6% overlap), almost one-third of the species were found in all three habitat types, and few species were unique to each habitat. We conclude that: (1) duration of flooding has a strong impact on species richness, diversity and plant distribution patterns; (2) most species are adapted to a wide range of habitats and flood durations; and (3) while flood duration may decrease local diversity, it also creates and maintains high landscape-scale diversity by increasing landscape heterogeneity. Received: 20 April 1997 / Accepted: 14 January 1999     

Tardigrades of the Australian Antarctic Territories: the Windmill Islands, East Antarctica

Six species of tardigrades, Pseudechiniscus suillus, Macrobiotus sp., Hypsibius antarcticus, Ramajendas frigidus, Diphascon chilenense and Diphascon pingue were extracted from mosses and lichens from the ice-free regions of the Windmill Islands near Casey Base, East Antarctica. Significant positive associations were found between the three common species ( Pseudechiniscus suillus, Hypsibius antarcticus, Diphascon chilenense ) and bryophytes, whereas strong negative associations were found between these species and algae and lichens. There were additional interspecific associations between the common species of tardigrades as well as between tardigrades, nematodes and rotifers.     

A survey of the terrestrial Tardigrada of the Vestfold Hills,Antarctica

A survey of the terrestrial tardigrades inhabiting growths of algae, lichens and mosses in the Vestfold Hills, Antarctica, was carried out at 11 and 35 sites during the austral summers of 1980 and 1982, respectively. In all, 24 species of plants were collected from which four genera and four species of Tardigrada were recovered. A key to the tardigrades of the area is presented. The distribution and associational patterns of the tardigrades are discussed in the context of other studies of antarctic Tardigrada.     

Survival of freezing by hydrated tardigrades inhabiting terrestrial and freshwater habitats

The seasonality and unpredictability of environmental conditions at high altitudes and latitudes govern the life cycle patterns of organisms, giving rise to stresses that cause death or development of specific adaptations. Ice formation is a major variable affecting the survival of both freshwater fauna and fauna inhabiting lichens, mosses and leaf litter. Tardigrades occupy a wide range of niches in marine, freshwater and terrestrial environments. The highest number of species is found in terrestrial habitats thanks to their ability to enter anhydrobiosis and cryobiosis. The cryobiotic ability of tardigrade species from polar regions is well known. Consequently, we focused our research on the ability to survive freezing in the active hydrated state using seven tardigrade species differing in phylogenetic position and collected at various altitudes and from different habitats in a temperate area. Specimens were cooled at different cooling rates (from 0.31 °C min⁻¹ to 3.26 °C min⁻¹). Even though the final survival and the time required by animals to recover to active life were both inversely related to the cooling rate, highly significant interspecific differences were found. Species survival ability ranged from excellent to none. Species living in xeric habitats withstood freezing better than those living in hygrophilous habitats, while true limnic species did not exhibit any cryobiotic ability. The ability to withstand freezing seems linked to the anhydrobiotic ability. The differences in cryptobiotic performance among tardigrade species seem more influenced by selective pressures linked to local adaptation to habitat characteristics than by phylogenetic relationships.     

Influence of tree age, tree size and crown structure on lichen communities in mature Alpine spruce forests

Testing the relations between tree parameters and the richness and composition of lichen communities in near-natural stands could be a first step to gather information for forest managers interested in conservation and in biodiversity assessment and monitoring. This work aims at evaluating the influence of tree age and age-related parameters on tree-level richness and community composition of lichens on spruce in an Alpine forest. The lichen survey was carried out in four sites used for long-term monitoring. In each site, tree age, diameter at breast height, tree height, the first branch height, and crown projection area were measured for each tree. Trees were stratified into three age classes: (1) <100 years old, immature trees usually not suitable for felling, (2) 100–200 years old, mature trees suitable for felling, and (3) >200 years old, over-mature trees normally rare or absent in managed stands. In each site, seven trees in each age class were selected randomly. Tree age and related parameters proved to influence both tree-level species richness and composition of lichen communities. Species richness increased with tree age and related parameters indicative of tree size. This relation could be interpreted as the result of different joint effects of age per se and tree size with its area-effect. Species turnover is also suspected to improve species richness on over-mature trees. Similarly to species richness, tree-level species composition can be partially explained by tree-related parameters. Species composition changed from young to old trees, several lichens being associated with over-mature trees. This pool of species, including nationally rare lichens, represents a community which is probably poorly developed in managed forests. In accordance to the general aims of near-to-nature forestry, the presence of over-mature trees should be enhanced in the future forest landscape of the Alps especially in protected areas and Natura 2,000 sites, where conservation purposes are explicitly included in the management guidelines.     

Tardigrades of South America: Machu Picchu and Ollantaytambo, Peru

During July 1999, a study group from the University of Kansas visited the ancient Inca ruins in and around Machu Picchu and Ollantaytambo, Peru. They collected lichens and mosses from the rock walls around the ruins. The samples contained four genera and six species of tardigrades. No associational patterns and relationships were detected. A new species, Echiniscus ollantaytamboensis nov. sp. is described.     

Causes of the large variation in bryophyte species richness and composition among boreal streamside forests

Questions: Boreal forests along small streams are bryophyte diversity hotspots because they are moist, productive and relatively high pH. Do these factors also explain the large differences in species richness and species composition found among streamside sites? Do the species of species‐poor sites represent nested subsets of the species of more species‐rich sites? How do the results apply to conservation? Location: Forests along small streams in mid‐boreal Sweden. Methods: Survey of the flora of liverworts and mosses and habitat properties, including calculation of a pH‐index based on species indicator values, in 37 sites (1000‐m² plots). Results: The number of bryophyte species per plot ranged from 34 to 125. Neither soil moisture nor basal area of trees (a proxy for productivity) correlated significantly with species richness and composition, whereas pH‐index and cover of boulders did. Species richness and composition were more strongly correlated with pH‐index for mosses than for liverworts. The richness and composition of bryophyte species most frequently found on moist ground, stream channel margins and, most unexpected, woody debris were all more strongly associated with the pH‐index than with other habitat properties. Although species composition was significantly nested, there was still some turnover of species along the first ordination axis. Conclusions To attain high numbers of species, streamside forests need to have boulders and at least pockets with higher soil and stream‐water pH. The number of Red list species was weakly correlated with total species richness and the most species‐rich sites contained many species found more in non‐forest habitats. Hence, bryophyte conservation in streamside forests should not focus on species‐rich sites but on the quality and quantity of substrate available for assemblages of forest species that are strongly disfavoured by forestry.     

Tardigrade Fauna of the Region between Oka and Volga Rivers (Russia) and Patterns of their Distribution in Substrates and Habitats

The region between the Oka and Volga rivers has been largely neglected with respect to tardigrade biodiversity. In the present study a total of 21 species from 7 genera, 3 families, 2 orders and only 1 class of tardigrades were present, and some of their ecological preferences were noted. The tardigrades in the studied region were mainly cosmopolitan. Eurytopic, hygrophilic and xerophilic species were common while obligate freshwater species were not found. There is a marked similarity in the tardigrade fauna within similar habitats from different locations within the region.     

Do protected areas in urban and rural landscapes differ in species diversity?

Previous studies from Central Europe and North America showed that species richness is higher in urban than in rural landscapes. Do protected areas, which can be found in both city and countryside, reflect this species richness pattern? The impact of urban land-use might reduce conservation success and necessitate special management strategies. We compared species richness and species spatial turnover of selected animal and plant taxa (carabids, butterflies, snails, birds, lichens, mosses, vascular plants) in 30 protected areas in the city of Halle and 56 protected areas in the adjacent rural district of Saalkreis (Central Germany). Species were mapped by experienced biologists within a systematic species inventory. We corrected species numbers for the effects of landscape structure (e.g. size, shape and distance of habitats) which might influence species diversity beyond urbanisation effects. Butterflies, birds and lichens had significantly higher species numbers in the rural protected areas. Species spatial turnover was higher among urban areas than among rural areas or pairs of urban and rural areas for most taxa. Diversity in all taxa depended on the size of a protected area. We discussed these patterns in the context of the general urban-rural species diversity patterns. Our results indicate an increasing isolation of species assemblages with urbanisation and highlight that space for protected areas is even more limited in urban than rural areas. An effective conservation of urban species diversity should include both typical urban and semi-natural habitats to cover the full range of species living in cities.     

Bryophyte and lichen diversity: A comparative study

Abstract We describe the regional species richness, variation in species richness and species turnover of bryophytes and lichens from 36 sites in lowland forests of southeastern Australia. The analyses subdivided the two major taxa into their constituent sub-groups: mosses, liverworts, and crustose, fruticose and foliose lichens. They also explored correlations between selected environmental variables and patterns of diversity. On a regional scale, there were 77 species of bryophytes and 69 species of lichens, giving a total of approximately one-third of the total number of vascular plant species in the region. Mean species richness was higher for lichens than bryophytes. Also, the two taxa were negatively correlated because lichens favoured dry sites and bryophytes favoured moist ones. Species turnover was greater for bryophytes than lichens, largely due to the distribution of liverwort species. Foliose lichens showed higher levels of turnover than crustose lichens. Multiple regression and canonical correspondence analysis showed that both taxa and all sub-groups responded to the same three variables: vascular plant cover, time since last fire and topographic position. Other variables, including time since logging and intensity of logging, explained little variation in bryophyte or lichen diversity. The data suggest that the strategies for the conservation of bryophyte and lichen biodiversity will be different, to reflect the different patterns of species richness and species turnover.