The sinking ark: pollution and the worldwide loss of biodiversity

Humans are making increasing demands on natural ecosystems. One recent study has concluded that our species is consuming or diverting some 40% of the net photosynthetic productivity of our planet. Many habitats are being converted to simpler systems which provide more harvestable goods to people. As a result, genetic diversity, species and whole ecosystems are disappearing; some scientists suggest that as many as 25% of the world's species could be lost in the next several decades.The sinking ark is usually characterized in terms of pollution, habitat loss, poaching, introduced species and illegal trade in wildlife products, but these are symptoms rather than causes. At a more fundamental level, many of the same factors which have enabled pollution to become such a problem have also been responsible for the loss in biodiversity; the most important factor is that the effects of pollutants on biodiversity have been considered an externality, an unintended side effect of industrial activity which brought measurable benefits to people. Development activities which have depleted biodiversity have proven profitable only because the real costs have been hidden.Keeping the ark afloat will require the Five-I Approach: investigation (learning how natural systems function); information (ensuring that the facts are available to inform decisions); incentives (using economic tools to help conserve biodiversity); integration (promoting a cross-sectoral approach to conserving biodiversity); and international support (building productive collaboration for conserving biodiversity).     

Habitat alteration and its effects on native fishes in the upper Tennessee River system, east-central U.S.A.

The upper Tennessee River drainage, which includes portions of the States of Virginia, North Carolina, and Tennessee, supports an exceptionally diverse fish fauna. Recent reductions in abundance and geographic ranges of several freshwater fishes have promulgated the imposition of protective measures for about 115 species among the three states, with nearly half of those species occurring in the upper Tennessee River. Most protected species are darters (Percidae: Etheostomatinae) or minnows (Cyprinidae), and are typically small, benthic invertivores. Major impacts on the fish fauna have resulted from dams, introduced species, toxic spills, mining and agriculture. An important cumulative effect of these impacts is fragmentation of the watershed; nearly 40% of the riverine habitat in major tributaries is either impounded or altered by tailwater discharges. The isolation and stress imposed on tributaries of the river have caused and will continue to cause extirpations of fishes, mussels and other aquatic fauna. Numerous federal, state, and private organizations are co-operating in efforts to protect rare species and habitats, improve agricultural and coal-producing practices, and enforce regulations for industrial and municipal effluents.     

Flower heliotropism in an alpine population of Ranunculus acris (Ranunculaceae): effects on flower temperature,insect visitation,and seed production

Some plants in arctic and alpine habitats have heliotropic flowers that track the sun. This results in a heating of the flower's interior, which may improve the possibilities for insect pollination and seed production. Here, I examine whether flower heliotropism in an alpine population of the self-incompatible Ranunculus acris L. (Ranunculaceae) enhances pollinator visitation and seed production. Flowers of Ranunculus acris tracked the sun during the day. Tracking accuracy was greatest during the middle of the day. The temperature elevation in flowers was negatively correlated with the flower's angle of deviation from the sun. Despite the increased temperature, insects did not discriminate among flowers on the basis of their angle of deviation from the sun, or tend to stay longer in the flowers aligned closest towards the sun. A tethering experiment was conducted on three groups of plants flowering at different times in the 1993 season and on one group the following season. Manipulation plants were constrained not to track the sun, whereas control plants tracked the sun naturally. Solar tracking had no effect on seed:ovule ratio, seed mass, or abortion rate in any of the groups. There is probably a very narrow range of weather conditions (cold, sunny, and calm) where flower heliotropism may enhance visitation rate to flowers and their seed production.     

Habitat utilization patterns of sympatric populations of Pseudomys gracilicaudatus and Rattus lutreolus in coastal heathland: A multivariate analysis

Abstract Habitat usage characteristics of two species of native murid rodents, Pseudomys gracilicaudatus and Rattus lutreolus were investigated on an area of coastal heathland at Myall Lakes National Park. A grid of 151 trap stations comprising 17 traplines was positioned across a mosaic of habitats. At each trap station 19 structural vegetation and physical variables known to affect the microdistribution of small mammals were measured. Multivariate statistical procedures identified those microhabitat variables that contribute to individual species' habitat use and habitat partitioning, and reduce potential competition for space. Cluster analysis classified trap stations into one of six habitat types that were mapped on the study area, identifying a heterogeneous assemblage of interlocking habitats. The pattern is a consequence of topographic variation on the site and, to a lesser extent, its fire history. Trapping results show P. gracilicaudatus and R. lutreolus exhibit similar macrohabitat selection, preferring topographically low habitats, with both species predominantly occupying short dense heath with dense sedge cover. The high overlap in macrohabitat use is greatly reduced when considered trap station by trap station, so that discriminant function and multiple regression analyses demonstrate marked microhabitat selection. Elevation was a highly significant variable, accounting for 41% and 27% of the variance in the habitat used by P. gracilicaudatus and R. lutreolus, respectively. This variable represents a soil moisture gradient that determines changes in the floristic and structural components of the biotic environment. Two other structural vegetation variables and vegetation height contributed 30% of the variance in P. gracilicaudatus distribution. Sedge cover was found to be significant and explained 13% of the variance in R. lutreolus distribution. Within-habitat separation was explained best with a linear combination of variables in a discriminant function, rather than by any single variable. Differential microhabitat selection, interference competition and diet separation appear to be the major factors facilitating coexistence of these two species.     

芦毒蛾越冬场所及越冬习性的研究

芦毒蛾是洞庭湖区重要的芦苇害虫,1年发生3代,以1龄幼虫在芦苇或杂草的枯叶中越冬。对于幼虫在其寄主植物之间的转移行为亦进行了观察。     

Natal philopatry in passerine birds: genetic or ecological influences?

The degree of natal philopatry (the likelihood that individualsbreed at or near their place of origin) can influence the extentof inbreeding in animal populations. Passerine birds have beencited as typically showing high natal philopatry, and natalphilopatry has been proposed as an adaptation to promote optimalinbreeding. A review of published and unpublished studies ofpasserines showed that natal philopatry was typically low, somaintaining a high level of inbreeding appears relatively unimportantfor such birds. Rather, natal philopatry appeared to be morestrongly influenced by ecological factors. Migratory passerineexhibited low natal philopatry compared to resident passerines,as predicted if dispersal costs for young birds are an importantdeterminant of natal philopatry. The erroneous view that natalphilopatry for passerines is generally high has resulted froma reporting bias toward resident species that have sufficientnatal philopatry to study. Natal philopatry was found to beevolutionarily labile; populations of the same species and pairsof closely related species that differed in their degree ofisolation differed considerably in their degree of philopatry.Future studies of natal philopatry should consider both theecological factors that could affect dispersal costs and thereporting biases that influence which data on philopatry tendto be reported.     

On the ecology of Colurellidae (Rotifera)

A material consisting of 45 colurellid rotifers from diverse waters in south and central Sweden was analyzed to reveal their relationships to their substrate. Periphytic substrates were generally preferred. Most species are obviously mobile and more or less euryecious, but a few show a predilection for bog environments. Some colurellids are euryhaline, but when inhabiting fresh water they prefer rivers and other environments with a high oxygen concentration, probably because of problems with osmoregulation.     

The consequences of habitat occupation and habitat overlap of the introduced tilapia Oreochromis mossambicus and indigenous fish species for fishery management in a Sri Lankan reservoir

Habitat occupation and habitat overlap of the introduced tilapia Oreochromis mossambicus and co-occurring indigenous fish species were studied in a shallow lowland reservoir in Sri Lanka. Results were used to discuss the possible existence of empty habitats in reservoirs and the position of the introduced O. mossambicus in the fish community. Predictions were made of the effects of a subsidiary small-meshed gillnet fishery for indigenous minor cyprinids on the yield of tilapia. The zooplanktivorous halfbeak Hyporamphus gaimardi, an indigenous invader from brackish water estuaries and lagoons, has successfully colonized the pelagic habitat in this reservoir. The habitat of the introduced O. mossambicus overlapped significantly with those of the indigenous minor cyprinids. Only the smallest size classes of O. mossambicus (below 45 mm) arc spatially segregated from these cyprinids. Spatial distribution patterns are influenced by the rainy seasons which trigger an inshore movement of O. mossambicus and several other species around November and May. Barbus spp, (Cyprinidae) need riverine habitats for spawning, but for all other species the available habitats within the reservoir are suitable to complete their full life cycle. Exploitation of Barbus spp. with gillnets with a mesh size of 30-mm stretched mesh is predicted to have considerable detrimental effects on the existing fishery for O. mossambicus. However, a gillnet fishery with 15-mm stretched mesh to exploit Amblypharyngodon melettinus, Rasbora daniconius and H. gaimardi in the open water zone is expected to be successful without harming the existing fishery for O, mossambicus or the populations of Barbus spp.     

PROROCENTRUM BELIZEANUM,PROROCENTRUM ELEGANS,AND PROROCENTRUM CARIBBAEUM,THREE NEW BENTHIC SPECIES (DINOPHYCEAE) FROM A MANGROVE ISLAND,TWIN CAYS,BELIZE1

Three new benthic dinoflagellate species, Prorocentrum belizeanum, Prorocentrum elegans, and Prorocentrum caribbaeum, from mangrove floating detritus are described from scanning electron micrographs. Species were identified based on shape, size, surface micromorphology, ornamentation of thecal plates, and architecture of the periflagellar area and intercalary band. Cells of P. belizeanum are round to slightly oval with a cell size of 55–60 μm long and 50–55 μm wide. Areolae are round and numerous (853–1024 per valve) and range from 0.66 to 0.83 μm in size. The periflagellar area of P. belizeanum is a broad V-shaped depression; it accommodates a flagellar and an auxiliary pore and a flared, curved apical collar. The intercalary band of P. belizeanum is horizontally striated. Prorocentrum elegans is a small species 15–20 μm long and 10–14 μm wide, with an ovate cell shape. The thecal surface is smooth. Two sizes of valve pores were recognized: large, round pores (20–22 per valve) arranged in a distinct pattern and smaller pores situated in an array along the intercalary band. The periflagellar area is V-shaped; it accommodates an uneven sized flagellar pore, an auxiliary pore, and an angled protuberant flagellar plate. The intercalary band is transversely striated. It is a bloom-forming species. Prorocentrum caribbaeum cells are heart-shaped with a rounded anterior end and a pointed posterior end. Cells range from 40 to 45 μm long and 30 to 35 μm wide. Thecal surface has two different-sized pores: large, round pores (145–203 per valve) arranged perpendicularly from the posterior margins, and small, round pores unevenly distributed on the thecal surface. The periflagellar area is ornate. It is V-shaped with a curved apical collar located next to the auxiliary pore; a smaller protuberant apical plate is adjacent to the flagellar pore. The intercalary band is transversely striated and sinuous. Cells are active swimmers.     

On choice of substrate and habitat in bdelzoid rotifers

Information on the distributions of 77 bdelloid rotifers from diverse waters in south and central Sweden was analyzed to reveal their relationships to substrate and habitat. Only two species were reported from plankton, both in low frequency. An artificial substrate, white cotton, was utilized only by few bdelloids, mainly by species with eyes. Only one species occurred at higher frequency on the saprobic substrate Sphaerotilus. Most bdelloids prefer environments rich in oxygen, but some species may be found in soft-bottom sediments. Several species dwell preferentially in diverse habitats of bogs. Some bdelloids have an exceptionally broad ecological range, but even for these is it possible to distinguish a pattern of preference and avoidance.