Phylogeography of the natterjack toad Bufo calamita in Britain: genetic differentiation of native and translocated populations

The natterjack toad Bufo calamita is rare in Britain, which is at the northwestern edge of its biogeographical range. We investigated the level of genetic differentiation amongst almost all (34 out of 38) of the surviving British populations of this species, and among six new populations established by translocations during the 1980s. For eight microsatellite loci, allele sizes and frequencies were analysed using samples from each of these populations. The populations clustered into three robustly differentiated groups, each of which corresponded with a geographical region (east/southeast England, Merseyside and Cumbria). The Cumbrian populations showed a further weak geographical substructuring into northern and southern clades. The populations in south Cumbria were genetically more diverse than those in any of the other regions, as judged by the mean numbers of alleles per locus and the mean heterozygosity estimates. The translocated populations clustered close to their founders and, with one exception, did not differ significantly with respect to mean allele numbers, heterozygosity or polymorphism level. However, significant genetic differentiation (as measured by unbiased R _ST) was found between all but one of the founder-translocation pairs. The implications of this phylogeographic study for the future conservation of B. calamita in Britain are discussed.     

The use of habitat mosaics by terrestrial vertebrate fauna: implications for conservation and management

Many species of vertebrates require multiple habitats to obtain different resources at different stages of their life-cycles. Use of habitat mosaics takes place on a variety of spatial and temporal scales, from a daily requirement for adjacent habitats to seasonal use of geographically separated environments. Mosaics of habitats are also required in some species to allow ontogenetic habitat shifts, while in others each sex may have specific requirements that are met by different habitats. The extent and nature of animal movements are key (but generally poorly known) factors affecting the vulnerability of species to landscape change. The requirement by many species for multiple habitats suggests that their conservation will be most effective in a mosaic environment and that protection of certain high profile habitats alone, such as rainforest, will be insufficient to achieve conservation goals. Management regimes that result in homogenization of habitats should be avoided. Priority should be given to research that identifies the extent to which species can locate habitat mosaics, at different spatial scales and arrangements, in modified environments.     

Seasonal changes in the habitat use and movements of adult European grayling in a large subarctic river

In late summer (13 August–13 September 1998), at water temperatures of 12·0–15·7° C, grayling ( n =14) stayed mainly in the riffle-section where they were captured in a large regulated river in northern Finland, moving little between consecutive days. In autumn (2–30 October 1998), at 1·7–6·7° C, the fish ( n =16) migrated to potential overwintering sites 0–14 km up- or downstream by mid October, moving mainly short distances thereafter. The daily movement rates, and the total ranges covered by the fish in late summer and autumn were 54±32 m (mean± s.d ) and 1053±1636 m, and 190±168 m and 3135±1850 m, respectively. In autumn the fish used deeper habitats (most suitable range 150–400 cm) with lower current velocities (20–80 cm s⁻¹) and finer bottom substrata (mainly sand) than in late summer (depth 100–325 cm, velocity 30–110 cm s⁻¹, and cobble-boulder substrata).     

Geographic variation in the habitat preference of a scarce predatory insect: evolutionary and conservation perspectives

1. While there has been considerable focus on prey occurrence as a factor determining the habitat preference of predators, the roles of other factors related to the habitat are less well characterised. 2. In aphidophagous ladybird beetles (Coleoptera: Coccinellidae), a number of species are more restricted in the habitats in which they live than are their prey. A number of such ladybirds appear to show geographic variation in habitat preference. 3. To better understand these phenomena, this study considered geographic variation in habitat preference in one such species, the 5-spot ladybird Coccinella quinquepunctata. Because of this ladybird's scarcity, a combination of over 20 years' observations, habitat surveys and online data was used to reach the study's conclusions. 4. The data collected indicate that the ladybird is specialised in pioneer habitats close to water, but broadens its range to non-riverine pioneer habitats in north-west continental Europe, where it is likely that a damper (micro)climate allows it to do so. Thus, microclimatic factors appear to be important in determining the habitat of this and probably other predators that are not constrained by prey occurrence. 5. Although threatened by river management elsewhere, in north-western Europe, this species clearly benefits from human activity, which creates many of the disturbed habitats it colonises there. This finding provides further support for the contention that many ladybirds are net beneficiaries of human influence, although they are often characterised as threatened.     

Isolation and characterization of granules of the toad bladder

Summary The electron-dense granules that lie just below the apical plasma membrane of granular epithelial cells of toad urinary bladder contribute glycoproteins to that apical membrane. Also, exocytosis of granules (and tubules) elicited by antidiuretic hormone potentially doubles that apical surface, during the same period the transport changes characteristic of the hormonal response occur.Granules separated from other membrane systems of the cells provide the material to assess the importance of the granules as glycocalyx precursors and in hormone action. We used isosmotic media to effect preliminary separations by differential centrifugation. Then granules were isolated by centrifugation on self-forming gradients of Percoll of decreasing hypertonicity.We find qualitative and quantitative changes in protein composition and enzymic activities in the isolated fractions. The primary criterion for granule purification was electron microscopic morphology. In addition, polypeptide species found in the granule fraction are limited in number and quantity. The granules are enzymically and morphologically not lysosomal in nature. Granules may provide the glycoproteins of the apical glycocalyx but they differ from the isolated plasma membrane fraction enzymically, in protein composition and in proportion of esterified cholesterol.We conclude that the granules are not average plasma membrane precursors. Their role in the membrane properties of the toad urinary bladder may now be evaluated by characterizing permeability and other properties of the isolated organelles.     

Stimulation of ammonium ion excretion in the toad urinary bladder by an extract of human urine

It is well known that ammonium ion excretion is increased during metabolic acidosis in mammals. The purpose of this study was to determine whether we could isolate from human urine during metabolic acidosis a factor that would stimulate NH₄⁺ and/or H⁺ excretion in toad urinary bladder. Extracts of urine from six human subjects collected during NH₄Cl-induced acidosis were prepared. These extracts were tested for their effect on NH₄⁺ excretion in hemibladders mounted between plastic chambers. The extracts significantly increased NH₄⁺ excretion in the toad urinary bladder. We found no effect on H⁺ excretion by these extracts. This ammoniuretic activity was not present in the urine when the same individuals were in metabolic alkalosis. We conclude that during metabolic acidosis a humoral factor is present which stimulates the excretion of NH₄⁺. The factor could act as a permease in the bladder cell or as a stimulator of an NH₄⁺ transport system.     

Seasonal changes in the migratory behaviour of the toad Bufo bufo: direction and magnitude of movements

Summary The migratory behaviour of the toad Bufo bufo was studied from February 1985 to April 1986 in the submontane region of Bavaria, West Germany. Toads were fitted with a mechanical tracking device to record individual paths of migration. Three aspects of migratory behaviour were quantified: orientation in relation to the breeding site, straightness of path, and locomotory activity. The annual activity period began with migration from the hibernation sites to the breeding pond in April. The paths went straight towards the breeding pond independent of the distance (70–420 m). During the period of oviposition the preference for the breeding site direction vanished and toads moved away from the breeding pond, but in less straight paths than before. In summer migratory activity decreased considerably and was restricted to small areas, the home ranges, at distances of 55–1600 m from the natal breeding pond. The straightness of path was rather low, because toads often returned to their starting points. During rainy nights toads occasionally left their home ranges for extensive excursions. In autumn most toads again migrated towards the breeding pond, but paths were significantly less straight and direct than in spring. However, toads stopped before reaching the breeding pond and hibernated in holes or under the leaf layer. The mortality rate of tracked toads was about 45%. The relative influence of 17 environmental variables on locomotory activity was evaluated by principal component analysis and stepwise multiple regression. Temperature at night and rainfall variables accounted for significant amounts of variance, whereas temperature by day, air humidity, and atmospheric pressure showed no correlation. Activity decreased if temperature approached 0° C or after long periods without rainfall. Within a certain range of tolerance, however, the locomotory activity of the toads was widely independent of environmental factors, indicating that endogeneous factors are more important sources of variation in the migratory behaviour of these toads than commonly assumed.     

The ecological genetics of introduced populations of the giant toad, Bufo marinus (Amphibia: Anura): dispersal and neighbourhood size

The pattern of colonization of the Moreton Bay region in southeast Queensland, Australia, by the giant toad, Bufo marinus , is described. Estimates are made of the rates of colonization in this and other regions. The mean values obtained range from 2.5 km/year in the south to 15.1 km/year in the north. The analysis suggests that colonization has been discontinuous in many areas, probably as a result of occasional, long-distance transportation of toads by humans. The variation in colonization rate is related in a predictable way to variation in environmental factors such as temperature and topography. In areas where discontinuities are least likely, colonization rates are used to estimate rates of continuous dispersal. These are combined with estimates of population density, sex ratios and offspring number variance to obtain estimates of genetic neighbourhood size. These are much greater than estimates of the effective size of B. marinus populations determined from gene frequency variances. The reasons for and implications of this discrepancy are discussed.     

Wetland use by brood‐rearing female ducks in a boreal forest landscape: the importance of food and habitat

Habitat use by birds may be related to single or interacting effects of habitat characteristics, food resources and predators, but little is known about factors affecting habitat use by wetland species in boreal ecosystems. We surveyed brood‐rearing females and ducklings of four common boreal duck species to assess the effects of habitat structure and food resources on the use of wetlands by brood‐rearing ducks. Although wetland use by duck broods was related to habitat structure and food abundance, their relative importance varied among duck species. For the Common Goldeneye Bucephala clangula, a diving duck, aquatic invertebrates and large emerging insects were the most important factors associated with wetland use. Common Teal Anas crecca broods were observed more often on wetlands with greater Dipteran emergence, whereas in Mallard Anas platyrhynchos both habitat structure and large emerging insects were important. The occurrence of Eurasian Wigeon Anas penelope broods was related to emerging Diptera and habitat structure but the associations were not strong. The varying habitat and food requirements of common duck species could influence the success of wetland management programmes, and consideration of these factors may be particularly important for initiatives aimed at harvested species or species of conservation concern.     

Oviposition habitat selection by the mosquito, Culiseta longiareolata: effects of conspecifics, food and green toad tadpoles

Abstract. 1. Ovipositing females should choose egg-laying sites which maximize the growth and survivorship of their offspring. Accordingly, they should avoid habitats with high densities of competitors and predators and should choose sites with adequate food. We tested experimentally the oviposition response of the mosquito, Culiseta longiareolata Macquart, to extra food and two species which are both potential competitors and predators of its offspring: conspecific larvae and green toad ( Bufo viridis ) tadpoles.
2. We conducted the experiment in outdoor artificial pools where wild C. longiareolata females were presented with choices of all combinations of the presence or absence of: (1) C.longiareolata larvae, (2) B.viridis tadpoles, and (3) extra food (a mixture of ground fish food and mouse chow).
3. Oviposition rates averaged approximately 4 times greater in response to extra food.
4. The presence of the tadpoles, particularly later in the experiment when they were larger, caused a significant reduction (approximately 50%) in oviposition rate.
5. We did not detect a statistically significant effect of conspecific larvae on oviposition habitat selection.
6. Our results indicate that Culiseta females choose habitats for oviposition based on food availability. They also tend to avoid habitats containing Bufo tadpoles, presumably to avoid predation and/or competition.     

Bidder's organ in the toad Bufo marinus: effects of orchidectomy on the morphology and expression of lamina-associated polypeptide 2

The Bidder's organ is an undeveloped ovary located anterior to the testis in male true toads (Bufonidae). The presence of sperm and oocytes, derived from the primordial germ cells of the male toad, provides an exceptional condition for the study of germ cell differentiation in vertebrates. In this study, the effects of orchidectomy on morphology and on lamina-associated polypeptide 2 (LAP2) expression were investigated in the Bidder's organ of Bufo marinus. To characterize bidderian oocytes, oogenesis in the ovary was divided into six stages. It was found that ovarian and bidderian oocytes were morphologically identical. To determine the expression of LAP2 isoforms, oocytes from the ovary and the Bidder's organ were examined by sodium dodecylsulfate-polyacrylamide gel electrophoresis and immunoblotting. In amphibians, LAP2beta is expressed in somatic cells, whereas LAP2omega is expressed in oocytes. The Bidder's organ normally contained previtellogenic oocytes of less than 150 micro m in diameter that expressed LAP2beta. However, the organ in some male toads contained a few larger oocytes, resulting in the faint detection of LAP2omega. After orchidectomy, bidderian oocytes grew and strongly expressed LAP2omega. Moreover, as in the ovary, LAP2omega was upregulated in bidderian oocytes of 240 microm in diameter. This work represents the first demonstration of the molecular similarity between ovarian and bidderian oocytes.     

Stand structure and regeneration in a Kamchatka mixed boreal forest

Abstract. A 1‐ha plot was established in a Betula platyphylla‐Picea ajanensis mixed boreal forest in the central Kamchatka peninsula in Russia to investigate stand structure and regeneration. This forest was relatively sparse; total density and stand basal area were 1071/ha and 25.8 m²/ha, respectively, for trees > 2.0 cm in trunk diameter at breast height (DBH). 25% of Betula regenerated by sprouting, and its frequency distribution of DBH had a reverse J‐shaped pattern. In contrast, Picea had a bimodal distribution. The growth rates of both species were high, reaching 20 m in ca. 120 yr. The two species had clumped distributions, especially for saplings. Betula saplings were not distributed in canopy gaps. Small Picea saplings were distributed irrespective of the presence/absence of gaps, while larger saplings aggregated in gaps. At the examined spatial scales (6.25–400 m²) the spatial distribution of Betula saplings was positively correlated with living Betula canopy trees and negatively with dead Picea canopy trees. This suggests that Betula saplings regenerated under the crowns of Betula canopy trees and did not invade the gaps created by Picea canopy trees. The spatial distribution of Picea saplings was negatively correlated with living and dead Betula canopy trees and positively with dead Picea canopy trees. Most small Picea seedlings were distributed under the crowns of Picea trees but not under the crowns of Betula trees or in gaps. This suggests that Picea seedlings establish under the crowns of Picea canopy trees and can grow to large sizes after the death of overhead Picea canopy trees. Evidence of competitive exclusion between the two species was not found. At a 20 m × 20 m scale both skewness and the coefficient of variation of DBH frequency distribution of Picea decreased with an increase in total basal area of Picea while those of Betula were unchanged irrespective of the increase in total basal area of Betula. This indicates that the size structure of Picea is more variable with stand development than that of Betula on a small scale. This study suggests that Betula regenerates continuously by sprouting and Picea regenerates discontinuously after gap formation and that the species do not exclude each other.     

The distribution and colocalization of neuropeptides and catecholamines in nerves supplying the gall bladder of the toad,Bufo marinus

The indirect immunofluorescence technique was used to determine the distribution of peptide-containing axons in the gall bladder of the cane toad, Bufo marinus. In addition, the adrenergic innervation of the gall bladder was examined by use of immunoreactivity to the catecholamine-synthesizing enzyme, tyrosine hydroxylase, and glyoxylic acid-induced fluorescence. On the basis of peptide coexistence, two intrinsic populations of neurones and their projecting fibres could be distinguished substance P neurones and vasoactive intestine peptide neurones. Neither of these two types of neurones contained any other colocalized neuropeptides. Four populations of nerve fibres arising from cell bodies outside the gall bladder were identified: nerves containing colocalized galanin, somatostatin and vasoactive intestinal peptide; nerves containing colocalized calcitonin gene-related peptide and substance P; adrenergic nerves containing neuropeptide Y; and nerves containing only adrenaline.     

High diversity of arbuscular mycorrhizal fungi in a boreal herb-rich coniferous forest

* Here, the diversity of arbuscular mycorrhizal (AM) fungi was determined in a boreal herb-rich coniferous forest in relation to environmental variables. * Root samples of five plant species (Fragaria vesca, Galeobdolon luteum, Hepatica nobilis, Oxalis acetosella and Trifolium pratense) were analysed from stands differing in age and forest management intensity. * Thirty-four Glomeromycota taxa (small-subunit ribosomal RNA gene (SSU rDNA) sequence groups) were detected from 90 root samples (911 clones), including eight new taxa. Sequence groups related to Glomus intraradices were most common (MO-G3 and MO-G13). Samples of H. nobilis were colonized by more AM fungal taxa (3.68 +/- 0.31) than those of O. acetosella (2.69 +/- 0.34), but did not differ significantly in this respect from those of F. vesca (3.15 +/- 0.38). Effects of forest management, host plant species (except above) or season on the number or composition of fungal taxa in root samples were not detected, and neither were they explained by environmental variables (vegetation, soil and light conditions). * This is the most taxon-rich habitat described to date in terms of root-colonizing Glomeromycota. The data demonstrate the importance of temperate coniferous forests as habitats for AM fungi and plants. Lack of obvious fungal community patterns suggests more complex effects of biotic and abiotic factors, and possibly no adverse effect of common forest management practices on AM fungal diversity.     

亚热带中山常绿阔叶林木本植物幼苗数量动态及其与生境的相关性

以百山祖自然保护区5 hm2永久样地150个幼苗监测站木本植物幼苗为研究对象,2008—2011年定期调查样方中幼苗的种类、数量、萌发、死亡等,探究亚热带中山常绿阔叶林幼苗种类组成、数量动态及其与生境的相关性。结果表明:1)百山祖样地在2008年至2011年出现的幼苗属于26科,40属,共53个物种,不同物种萌发时段有异;2)2009年样地幼苗存活比率为7.7%,2010年为-20.8%,2011年则是-0.3%,幼苗存活比率不高,种类和数量呈减少趋势;3)存活幼苗中有明显的优势物种,分别为光亮山矾(Symplocos lucida)、尖连蕊茶(Camellia cuspidata)、浙闽新木姜子(Neolitsea aurata var.undulatula)、尖叶菝葜(Smilax arisanensis)和短尾柯(Lithocarpus brevicaudatus),5个物种之和占幼苗总数比例50%;4)种子的萌发与生境有极显著的相关性,且与生境因子中水分关联最大;5)存活幼苗数与样站坡位、水分、落叶层厚度呈现显著相关性,水和光照是影响幼苗存活的主要因素。     

Current distribution,breeding population and habitat use of the globally threatened Grey-necked Picathartes Picathartes oreas in south-eastern Nigeria: a call for conservation action

The Grey-necked Picathartes Picathartes oreas is a globally threatened bird species in Africa with a wild population of less than 10,000 individuals. The Nigerian population, which has been poorly studied, is restricted to the forest of Cross River. This study re-assessed the distribution, breeding population, habitat use and current threats of the Grey-necked Picathartes by revisiting the 91 breeding sites identified during the first and only survey of the species in 1987. We estimated a breeding population of 164 individuals across 82 breeding sites. Only 72 breeding sites were found in the localities where 91 had been registered in 1987. Thirteen (18%) of these 72 sites were no longer active and showed evidence of human disturbance. The occurrence of Grey-necked Picathartes’ nest sites was positively predicted by higher number of emergent trees, larger rocks and negatively related to disturbance matrices. Similarly, larger colony sizes were associated with high canopy cover and rock height. Also, the probability of finding an active nest within a breeding colony was significantly predicted by increased canopy, tree density and ground cover. Human threats included farming, wire snares, egg and juvenile removal, bush burning, and hunter’s camps. These threats, though specific to the Grey-necked Picathartes, threaten the integrity of the Cross River forest habitats.     

Conifer seedling recruitment in a southeastern Canadian boreal forest: the importance of substrate

Abstract. In order to explain conifer species recruitment in Canada's southeastern boreal forest, we characterized conifer regeneration microsites and determined how these microsites vary in abundance during succession. Microsite abundance was evaluated in deciduous, mixed and coniferous stands along a 234-yr postfire chronosequence. Conifers were most often found in relatively well-illuminated microsites, devoid of litter, especially broad-leaf litter, and with a reduced cover of lower vegetation (< 50 cm tall). Although associated with moss-rich forest floor substrates, Abies balsamea was the most ubiquitously distributed species. Picea glauca and especially Thuja occidentalis seedlings were frequently found on rotten logs. Light measurements did not show differences among seedling species nor between stand types. The percentage cover of broad-leaf litter decreased significantly during succession. Also, rotten logs covered with moss occupied a significantly larger area in the mid-successionnal stands than in early successional deciduous or late successional coniferous stands. The results suggest that the presence of specific forest floor substrate types is a factor explaining low conifer recruitment under deciduous stands, conifer codominance in the mid-successional stage, and delayed Thuja recolonization after fire. Results also suggest that some facilitation mechanism is responsible for the observed directional succession.