From clear lakes to murky waters - tracing the functional response of high-latitude lake communities to concurrent 'greening' and 'browning'.

Climate change and the intensification of land use practices are causing widespread eutrophication of subarctic lakes. The implications of this rapid change for lake ecosystem function remain poorly understood. To assess how freshwater communities respond to such profound changes in their habitat and resource availability, we conducted a space-for-time analysis of food-web structure in 30 lakes situated across a temperature-productivity gradient equivalent to the predicted future climate of subarctic Europe (temperature +3°C, precipitation +30% and nutrient +45 µg L-1 total phosphorus). Along this gradient, we observed an increase in the assimilation of pelagic-derived carbon from 25 to 75% throughout primary, secondary and tertiary consumers. This shift was overwhelmingly driven by the consumption of pelagic detritus by benthic primary consumers and was not accompanied by increased pelagic foraging by higher trophic level consumers. Our data also revealed a convergence of the carbon isotope ratios of pelagic and benthic food web endmembers in the warmest, most productive lakes indicating that the incorporation of terrestrial derived carbon into aquatic food webs increases as land use intensifies. These results, reflecting changes along a gradient characteristic of the predicted future environment throughout the subarctic, indicate that climate and land use driven eutrophication and browning are radically altering the function and fuelling of aquatic food webs in this biome.

Transcontinental migratory connectivity predicts parasite prevalence in breeding populations of the European barn swallow.

Parasites exert a major impact on the eco-evolutionary dynamics of their hosts and the associated biotic environment. Migration constitutes an effective means for long-distance invasions of vector-borne parasites and promotes their rapid spread. Yet, ecological and spatial information on population-specific host-parasite connectivity is essentially lacking. Here, we address this question in a system consisting of a transcontinental migrant species, the European barn swallow (Hirundo rustica) which serves as a vector for avian endoparasites in the genera Plasmodium, Haemoproteus and Leucocytozoon. Using feather stable isotope ratios as geographically informative markers, we first assessed migratory connectivity in the host: Northern European breeding populations predominantly overwintered in dry, savannah-like habitats in Southern Africa, whereas Southern European populations were associated with wetland habitats in Western Central Africa. Wintering areas of swallows breeding in Central Europe indicated a migratory divide with both migratory programmes occurring within the same breeding population. Subsequent genetic screens of parasites in the breeding populations revealed a link between the host's migratory programme and its parasitic repertoire: controlling for effects of local breeding location, prevalence of Africa-transmitted Plasmodium lineages was significantly higher in individuals overwintering in the moist habitats of Western Central Africa, even among sympatrically breeding individuals with different overwintering locations. For the rarer Haemoproteus parasites, prevalence was best explained by breeding location alone, whereas no clear pattern emerged for the least abundant parasite Leucocytozoon. These results have implications for our understanding of spatio-temporal host-parasite dynamics in migratory species and the spread of avian borne diseases.

Seeking the sun in deep, dark places: mesopelagic sightings of ocean sunfishes (Molidae).

Evidence is presented from publicly available remotely operated vehicle (ROV) footage that suggests deep-water ranging in ocean sunfishes (family Molidae) is more common than typically thought, including a new maximum depth recorded for the southern sunfish Mola ramsayi.

Trophic flexibility by roach Rutilus rutilus in novel habitats facilitates rapid growth and invasion success.

Stable isotope and gut content analyses, in conjunction with backcalculated length-at-age estimates of growth, were employed to examine the relationship between trophic ecology and growth rate of a successful invader, Rutilus rutilus, in eight lakes in Ireland. The data revealed that R. rutilus was a trophic generalist in Irish lakes. It utilized a greater proportion of pelagic resources in mesotrophic lakes than in eutrophic lakes, potentially due to a greater density of benthic macroinvertebrates in eutrophic systems. The species was characterized by a large dietary and isotopic niche width and high temporal and spatial variations in diet. Growth rates were typical of those found in the native range of the species and were unrelated to either lake productivity or fish's diet. A generalist trophic ecology confers significant advantages on an invasive species, allowing it to exploit a variety of novel resources and fluctuations in prey availability.

Parallel and nonparallel ecological, morphological and genetic divergence in lake-stream stickleback from a single catchment.

Parallel phenotypic evolution in similar environments has been well studied in evolutionary biology; however, comparatively little is known about the influence of determinism and historical contingency on the nature, extent and generality of this divergence. Taking advantage of a novel system containing multiple lake-stream stickleback populations, we examined the extent of ecological, morphological and genetic divergence between three-spined stickleback present in parapatric environments. Consistent with other lake-stream studies, we found a shift towards a deeper body and shorter gill rakers in stream fish. Morphological shifts were concurrent with changes in diet, indicated by both stable isotope and stomach contents analysis. Performing a multivariate test for shared and unique components of evolutionary response to the distance gradient from the lake, we found a strong signature of parallel adaptation. Nonparallel divergence was also present, attributable mainly to differences between river locations. We additionally found evidence of genetic substructuring across five lake-stream transitions, indicating that some level of reproductive isolation occurs between populations in these habitats. Strong correlations between pairwise measures of morphological, ecological and genetic distance between lake and stream populations supports the hypothesis that divergent natural selection between habitats drives adaptive divergence and reproductive isolation. Lake-stream stickleback divergence in Lough Neagh provides evidence for the deterministic role of selection and supports the hypothesis that parallel selection in similar environments may initiate parallel speciation.

Phylogenetic and phylogeographic analysis of the genus Orestias (Teleostei: Cyprinodontidae) in the southern Chilean Altiplano: the relevance of ancient and recent divergence processes in speciation.

This study presents phylogenetic molecular data of the Chilean species of Orestias to propose an allopatric divergence hypothesis and phylogeographic evidence that suggests the relevance of abiotic factors in promoting population divergence in this complex. The results reveal that diversification is still ongoing, e.g. in the Ascotán salt pan, where populations of Orestias ascotanensis restricted to individual freshwater springs exhibit strong genetic differentiation, reflecting putative independent evolutionary units. Diversification of Orestias in the southern Altiplano may be linked to historical vicariant events and contemporary variation in water level; these processes may have affected the populations from the Plio-Pleistocene until the present.

Stable isotopes challenge the perception of ocean sunfish Mola mola as obligate jellyfish predators.

Evidence is provided from stable isotope analysis that aggregations of small ocean sunfish Mola mola (total length <1 m) feed broadly within coastal food webs and their classification as obligate predators of gelatinous zooplankton requires revision.

Are phenotypic traits useful for differentiating among a priori Coregonus taxa?

A key for three putative species apparently found in three geographic areas, i.e. Coregonus clupeoides (in Scotland), Coregonus stigmaticus (in England), and Coregonus pennantii (in Wales) given in a recent review was tested quantitatively using 544 individuals from nine populations. The classification success of the key was very low (27%). It was concluded that there is currently no robust evidence for the recognition of the three putative species. Furthermore, the use of phenotypic characters alone to distinguish putative species in postglacial fish species such as those of the genus Coregonus that show homoplasy in many of these traits is questioned. In the absence of further evidence, it was concluded that a single highly variable species best describes the pattern of phenotypic variation in these U.K. populations. On this basis it is argued that taxonomic subdivision of U.K. European coregonids is inappropriate and that Coregonus lavaretus should prevail as the species name applicable to all populations.

Has habitat heterogeneity promoted phenotypic and ecological sub-structuring among a Coregonus lavaretus population in a large Scottish lake?

Differences in stable-isotope values, morphology and ecology in whitefish Coregonus lavaretus were investigated between the three basins of Loch Lomond. The results are discussed with reference to a genetic investigation to elucidate any substructuring or spawning site fidelity. Foraging fidelity between basins of Loch Lomond was indicated by δ¹³C and δ¹5N values of C. lavaretus muscle tissue. There was, however, no evidence of the existence of sympatric morphs in the C. lavaretus population. A previous report of two C. lavaretus'species' in Loch Lomond probably reflects natural variation between individuals within a single mixed population.

Implications of climate change for the fishes of the British Isles.

Recent climatic change has been recorded across the globe. Although environmental change is a characteristic feature of life on Earth and has played a major role in the evolution and global distribution of biodiversity, predicted future rates of climatic change, especially in temperature, are such that they will exceed any that has occurred over recent geological time. Climate change is considered as a key threat to biodiversity and to the structure and function of ecosystems that may already be subject to significant anthropogenic stress. The current understanding of climate change and its likely consequences for the fishes of Britain and Ireland and the surrounding seas are reviewed through a series of case studies detailing the likely response of several marine, diadromous and freshwater fishes to climate change. Changes in climate, and in particular, temperature have and will continue to affect fish at all levels of biological organization: cellular, individual, population, species, community and ecosystem, influencing physiological and ecological processes in a number of direct, indirect and complex ways. The response of fishes and of other aquatic taxa will vary according to their tolerances and life stage and are complex and difficult to predict. Fishes may respond directly to climate-change-related shifts in environmental processes or indirectly to other influences, such as community-level interactions with other taxa. However, the ability to adapt to the predicted changes in climate will vary between species and between habitats and there will be winners and losers. In marine habitats, recent changes in fish community structure will continue as fishes shift their distributions relative to their temperature preferences. This may lead to the loss of some economically important cold-adapted species such as Gadus morhua and Clupea harengus from some areas around Britain and Ireland, and the establishment of some new, warm-adapted species. Increased temperatures are likely to favour cool-adapted (e.g. Perca fluviatilis) and warm-adapted freshwater fishes (e.g. roach Rutilus rutilus and other cyprinids) whose distribution and reproductive success may currently be constrained by temperature rather than by cold-adapted species (e.g. salmonids). Species that occur in Britain and Ireland that are at the edge of their distribution will be most affected, both negatively and positively. Populations of conservation importance (e.g.Salvelinus alpinus and Coregonus spp.) may decline irreversibly. However, changes in food-web dynamics and physiological adaptation, for example because of climate change, may obscure or alter predicted responses. The residual inertia in climate systems is such that even a complete cessation in emissions would still leave fishes exposed to continued climate change for at least half a century. Hence, regardless of the success or failure of programmes aimed at curbing climate change, major changes in fish communities can be expected over the next 50 years with a concomitant need to adapt management strategies accordingly.

Behavioral and neurochemical effects of the serotonin (5-HT)1A receptor ligand spiroxatrine.

The effects of spiroxatrine, a putative antagonist with selectivity for the serotonin (5-HT)1A receptor, were compared with compounds believed to function as agonists at the 5-HT1A receptor. Schedule-controlled responding of pigeons was maintained under a multiple 30-response fixed-ratio (FR), 3-min fixed-interval (FI) schedule or under a schedule in which responding was suppressed by electric shock ("conflict" procedure). Under the multiple schedule, spiroxatrine (0.3-1.0 mg/kg) decreased FR responding but did not affect FI responding; responding was decreased in both schedule components at 3.0 mg/kg. When administered alone, buspirone, a compound believed to produce its anxiolytic effects through 5-HT1A agonist actions, produced effects similar to those of spiroxatrine; in combination, the two drugs produced greater effects than when either was administered alone. As with 5-HT1A agonists such as buspirone and 8-hydroxy-2(di-n-propylamino)tetralin (8-OH-DPAT) in the pigeon, spiroxatrine (0.01-1.0 mg/kg) increased punished responding. Spiroxatrine and buspirone were potent inhibitors of [3H]8-OH-DPAT binding to pigeon cerebral membranes with IC50 values in the nM range. Neurochemical analyses of metabolite changes produced by spiroxatrine in pigeon cerebrospinal fluid showed buspirone-like effects, with increases in MHPG, DOPAC and HVA at doses that decreased 5-HIAA levels. Spiroxatrine dose-dependently blocked the behavioral effects of the dopamine agonist piribedil indicating that, like buspirone, it also is a potent dopamine antagonist. Spiroxatrine most likely functions as an agonist at the 5-HT1A receptor. As with buspirone, however, spiroxatrine has a prominent dopamine antagonist component.

Quantitative analyses of GFRalpha-1 and GFRalpha-2 mRNAs and tyrosine hydroxylase protein in the nigrostriatal system reveal bilateral compensatory changes following unilateral 6-OHDA lesions in the rat.

Copy numbers of mRNAs for GFRalpha-1 and GFRalpha-2, the preferred receptors for glial cell line-derived neurotrophic factor (GDNF) and neurturin (NTN) were determined by real-time quantitative RT-PCR (QRT-PCR). Receptor expression was assessed in striatum (ST) and substantia nigra (SN) of normal rats and rats acutely or progressively lesioned by 6-OHDA injected into the medial forebrain bundle or ST, respectively. GFRalpha-1 mRNA was clearly detected in normal ST. In normal SN, significantly higher expression of both receptors was observed. At 4 weeks after acute lesion, GFRalpha-2 mRNA was markedly decreased in SN bilaterally, whereas GFRalpha-1 mRNA in SN and ST was not affected. A progressive lesion resulted in a progressive decrease of GFRalpha1 mRNA in ST bilaterally. In SN, levels of GFRalpha-1 mRNA were not significantly affected by a progressive lesion, whereas GFRalpha-2 mRNA was markedly decreased bilaterally. Quantitative western blotting standardized against tyrosine hydroxylase (TH) protein from PC12 cells revealed the expected decrease in TH protein in lesioned SN, but also significant increases in TH protein in contralateral, unlesioned SNs at 4 weeks after both acute and progressive lesions. These data suggest that previously unrecognized compensatory changes in the nigrostriatal system occur in response to unilateral dopamine depletion. Since the changes observed in receptor expression did not always parallel loss of dopamine neurons, cells in addition to the nigral dopamine neurons appear to be affected by a 6-OHDA insult and are potential targets for the neurotrophic factors, GDNF and NTN.

Ichthyocotylurus erraticus (Digenea: Strigeidae): factors affecting infection intensity and the effects of infection on pollan ( Coregonus autumnalis ), a glacial relict fish.

Lough Neagh pollan are heavily infected with the strigeid Ichthyocotylurus erraticus , with 100% prevalence and median infection intensities of 600+ metacercariae in the pericardial cavity of mature fish. Female fish were more heavily infected than males. Infection intensity, which rose in summer, varied with pollan size, year, sampling bay within the lough and water depth within bays. Heavily infected pollan were caught further offshore than lightly infected fish. Spatial variation in pollan infection intensity corresponded to variation in the abundance of the first intermediate host, Valvata snails. The data suggest that heavily infected fish had lower food intakes. Parasitism reduced condition and liver size in male fish but condition in heavily parasitized females increased. Infection intensity was greater in larger fish of a given age. These patterns are discussed in the context of risks and rewards. The data suggest that inshore waters in summer are the preferred habitat of pollan and that the greater infection intensity of offshore fish results from their reduced competitive ability as a consequence of parasitism and the increased risk of infection there.

Derepressed utilization of L-malic acid and succinic acid by mutants of Pachysolen tannophilus.

Utilization of the tricarboxylic acid (TCA) cycle intermediates, L-malic acid and succinic acid, by the yeast Pachysolen tannophilus is repressed in the presence of glucose. Strains of P. tannophilus containing mutations in two hexokinases and a glucokinase were characterized for growth on glucose plus L-malic acid or succinic acid. Increased specific utilization rates of malic acid and succinic acid in the presence of glucose were observed in mutants containing a lesion in hexokinase A, an enzyme associated with catabolite repression. Such derepressed mutants may have application in winemaking in which utilization of a major grape acid, L-malic acid, is often desirable for acidity reduction.

Immunohistochemical and biochemical analysis of serotonin and substance P colocalization in the nucleus tractus solitarii and associated afferent ganglia of the rat.

In a previous study of afferent projections to the nucleus tractus solitarii (NTS), it was shown that over half of the retrogradely-labelled neurons in the nucleus raphe pallidus contained serotonin-immunoreactivity and over half of these neurons contained substance P-immunoreactivity, suggesting that these two putative neurotransmitters are colocalized in NTS-afferent neurons. The objectives of the present study were to 1) directly determine if varicosities in the NTS, the area postrema (AP), and the dorsal motor nucleus of the vagus nerve (DMN) do contain both transmitters, 2) determine if primary afferent neurons in the nodose and pretrosal ganglia might also colocalize serotonin and substance P, and 3) quantify the amount of substance P that is contained in serotonergic varicosities in the NTS. Distributions and colocalization of substance P and serotonin in the NTS were studied using dual-color immunohistochemistry, while the quantity of substance P in serotonergic varicosities was assessed by radioimmunoassay (RIA) using micropunches from the NTS of 5,7-dihydroxytryptamine-(5,7 DHT-) and vehicle-treated rats. Varicosities that contained both serotonin- and substance P-immunoreactivity were found in the NTS, the DMN, and the AP. Double-labelled varicosities were common in the NTS and DMN (i.e., qualitatively similar to the density seen in the hypoglossal nucleus and in the ventral horn of the cervical spinal cord); however, the vast majority of the varicosities in these autonomic areas only displayed immunoreactivity for one or the other of these transmitters. This paucity of doubly-labelled varicosities, in comparison to the number of singly-labelled varicosities, was reflected in the lack of a significant decrease in substance P levels as determined by RIA of micropunches taken from caudal and intermediate levels of the NTS in 5,7 DHT- and vehicle-treated rats.(ABSTRACT TRUNCATED AT 250 WORDS)

Behavioral studies with anxiolytic drugs. V. Behavioral and in vivo neurochemical analyses in pigeons of drugs that increase punished responding.

Behavioral and neurochemical effects of several drugs that increase punished responding were studied in pigeons. Key pecking was established under a schedule of reinforcement in which periods of food-maintained responding alternated with periods in which behavior also was suppressed by the presentation of electric shock. Buspirone (0.1-10.0 mg/kg), gepirone (0.1-1.0 mg/kg), 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT; 0.1-3.0 mg/kg), chlordiazepoxide (3.0-30.0 mg/kg) and to a lesser extent clozapine (0.1-1.0 mg/kg) all produced increases in punished responding at doses having little effect on or decreasing the rate of unpunished responding. Neurochemical analyses on samples of cerebrospinal fluid after administration of several doses of each compound were performed for the dopamine metabolites homovanillic acid (HVA) and dihydroxyphenylacetic acid (DOPAC), the noradrenergic metabolite 3-methoxy-4-hydroxyphenylethylene glycol (MHPG) and the serotonin metabolite 5-hydroxyindoleacetic acid (5-HIAA). Gepirone, 8-OH-DPAT and the novel anxiolytic buspirone produced decreases in 5-HIAA at doses that increased punished responding in the behavioral studies. Buspirone increased levels of HVA and DOPAC, whereas its structural analog gepirone and the 5-hydroxytryptamine1A agonist 8-OH-DPAT had little effect on or decreased levels of these metabolites. Chlordiazepoxide, a prototypic benzodiazepine anxiolytic, produced only modest decreases in each of the metabolites studied. Clozapine, an atypical antipsychotic drug, produced increases in each of the metabolites studied, although only the 5-HIAA effect occurred at doses that were not behaviorally disruptive. Haloperidol (0.03-1.0 mg/kg) produced only decreases in punished and unpunished responding, whereas eliciting increases in the appearance of MHPG, DOPAC and HVA; levels of 5-HIAA were relatively unaffected.(ABSTRACT TRUNCATED AT 250 WORDS)