AimsSpecies richnesses show marked spatial trends, but the contribution of speciation rates (SpecRates) to these trends is less clear. The roles of environmental heterogeneity (topography and climate), glaciation, dispersal ability, times to colonise, and to speciate to large-scale variation in SpecRates of freshwater fish faunas are assessed.LocationAtlantic and Pacific coast drainages in North, Central, and South America.TaxonFish.MethodsPublished information was compiled on SpecRates, phylogenies, colonisation times, species geographic distributions, and migratory behaviour of fishes in 582 catchments. The effects of topographic and climatic factors, including glaciation and vagility, on three speciation rate metrics were examined using boosted regression tree models.ResultsMean SpecRates differ five-fold across drainage regions and with glaciation. Pacific coast drainage SpecRates are highest in the Nearctic and decline southwards, but in Atlantic drainages, rate trends differ between Nearctic and Neotropical basins. Assemblage SpecRates vary with the percentage of migratory species, glaciation, environmental heterogeneity, colonisation time, and species age. High Nearctic rates are associated with postglacial recolonisation by rapidly speciating diadromous species, but rates in the Neotropics for resident and potamodromous species are higher than for diadromous species. Species dispersing into an area are more migratory, occur further north, and have wider distributions than species diversifying in situ. Endemicity in the more recently colonised Nearctic increases with colonisation time to Neotropical levels.Main ConclusionsSpatial and temporal variation in topography and climate generate differences in connectivity which, coupled with differences in species abilities to overcome these barriers, result in differences in speciation rates in different areas.

The roles of physical barriers to dispersal and species' abilities to cross barriers have in shaping freshwater fish distributions has been little explored at the macroscale. This study investigates how topography and species migratory behaviours and salinity tolerances (vagility) affect catchment isolation, species richness, large‐scale distribution patterns and turnover across latitudes and coasts.

Predator-prey size (PPS) relationships are determined by predator behaviour, with the likelihood of prey being eaten dependent on their size relative to that of the consumer. Published PPS relationships for 30 pelagic or benthic marine fish species were analysed using quantile regression to determine how median, lower and upper prey sizes varied with predator size and habitat. Habitat effects on predator foraging activity/mode, morphology, growth and natural mortality are quantified and the effects on PPS relationships explored. Pelagic species are more active, more likely to move by caudal fin propulsion and grow more rapidly but have higher mortality rates than benthic species, where the need for greater manoeuvrability when foraging in more physically complex habitats favours ambush predators using pectoral fin propulsion. Prey size increased with predator size in most species, but pelagic species ate relatively smaller prey than benthic predators. As pelagic predators grew, lower prey size limits changed little, and prey size range increased but median relative prey size declined, whereas the lower limit increased and median relative prey size was constant or increased in benthic species.

The Water Framework Directive was widely welcomed because it sought to integrate chemical and biological elements of aquatic ecosystems to achieve 'good ecological status', reflecting at most slight anthropogenic impact. However, implementation has been criticised because of the failure to adequately integrate these elements and assess status of the whole ecosystem. In this study, a suite of environmental and biotic variables was measured to assess their relative importance as predictors of lake status for 50 lakes in the north of the island of Ireland. Total Phosphorus (TP) had a strong effect on taxon biomasses and ecological quality ratios (EQR) for most taxa, as expected, but other environmental variables, such as pH, water colour and spatial location, were also important. Most variance in mean EQR, the average of the taxon values, was predicted by five environmental variables (chlorophyll a, TP, population density, water colour and elevation) and whether (alien) cyprinid fish were present. Oligotrophic lakes with cyprinid fish had lower mean EQRs than cyprinid-free lakes, indicating the importance of recording species introductions when assessing lake status. Strong evidence for bottom-up effects was also detected, and cyprinids probably influenced trophic structure by increasing nutrient release from the sediment rather than by top-down effects. Phytoplankton biomass, fish biomasses, and the percentage of predatory fish, increased with TP. Our results further emphasize the need to adopt a more integrated approach when assessing lake status.

Aim: To identify the contributions of geomorphological and hydrological/climatic factors to differences in total and endemic freshwater fish species richness between Atlantic and Pacific drainages. Location: Glaciated and unglaciated catchments draining to the Atlantic and Pacific Oceans in North (NA) and South America (SA). Taxon: Fish. Methods: A database of native freshwater fish species richnesses in drainage basins was compiled from published information, and the contributions of temperature, rainfall, catchment area, river length, channel gradient, discharge and geographic location in accounting for variation in total and endemic species richness were assessed using boosted regression trees. Results: Atlantic drainages have larger catchments, with longer rivers, lower channel gradients, greater discharges and lower flow variability than Pacific ones of the same size. Unglaciated Atlantic drainages in both NA and SA have more species than Pacific drainages, but glaciated Pacific NA had significantly more species than the other Pacific areas. Geographic location had the greatest influence on total richness, but catchment area, river length and temperature were more important for endemic species. Pacific drainages had proportionally more endemics than Atlantic drainages. Main conclusions: Tectonically driven topographic change, by altering relief, affects catchment size, slopes and connectivity, with the latter also affected by climatic changes in ice cover and aridity. These geomorphic and long-term climatic changes, by influencing speciation, extinction and dispersal, govern freshwater fish species richness in Atlantic and Pacific catchments.

Aim This study assesses the extent to which biogeographic patterns in freshwater fish beta diversity and nestedness are due to dispersal limitation, from differences in dispersal opportunity across geographic areas and in dispersal ability across species.Location Europe and the Atlantic and Pacific realms of North America (NA), east and west of the Continental Divide.Methods The effects of glaciation, realm shape, connectivity, current climate and vagility on regional-level beta diversity and nestedness were investigated. Turnover and nestedness-resultant dissimilarity components of beta diversity and the nestedness metric based on overlap and decreasing fill (NODF) were calculated from regional species lists and the contributions of turnover and segregation to nestedness structure quantified.Results Geographic distance was a stronger predictor of beta diversity than climatic and environmental heterogeneity distances. Species range shapes varied with postglacial colonization direction, being more extensive in an east-west direction in Europe than in Atlantic NA. Turnover increased with declining connectivity, in unglaciated areas, and in non-migratory species. Species were significantly less nested than expected because of high turnover and within-realm heterogeneity in regional faunas. Deviations from nestedness were greater in unglaciated areas and in migratory species. Non-migrants, but not migrants, exhibited coincident range boundaries.Main conclusions Spatial trends in beta diversity and nestedness in freshwater fish in NA and Europe result primarily from differences in postglacial recolonization opportunity across realms and in dispersal ability across species. Multiple metrics are necessary to identify the processes determining the spatial structure of species assemblages.

We report three new occurrences of Mysis salemaai, a conservationally important glacial relict at the southern limit of its range, in Castlewellan Lake, Lough Scolban and Lough Macnean Upper, in the north of Ireland. This increases the number of lakes in Ireland where the species has been recorded to fourteen.We consider lake area and maximum lake depth as factors that might determine the long-term survival of M. salemaai populations and show that these populations tend to occur in relatively large, deep lakes. We also show that population densities in Lough Neagh and Lough Erne are declining.

The latitudinal species richness gradient (LRG) has been the subject of intense interest and many hypotheses but much less consideration has been given to longitudinal richness differences. The effect of postglacial dispersal, determined by connectivity and vagility, on richness was evaluated for the species-poor European and North American Pacific and species-rich Atlantic regional freshwater fish faunas. The numbers of species, by habitat, migration and distributional range categories, were determined from regional species lists for these three realms. The current orientation and past connections of drainage channels indicate that connectivity is greatest in the Atlantic and least in the Pacific. With increasing connectivity across realms, endemism decreased and postglacial recolonization increased, as did the LRG slope, with the greatest richness difference occurring between southern Atlantic and Pacific regions. Recolonizing species tended to be migratory, habitat generalists and from families of marine origin. Diversification, as indicated by species/genus ratios, probability of diversification, taxonomic distinctness and endemicity, declined with increasing latitude in all realms and was least in Europe. Richness patterns are consistent with an LRG driven by the time available for postglacial recolonization and by differences in dispersal ability, with richness differences across realms reflecting differences in dispersal and diversification.

The density and composition of stream bed metal deposits are affected by physical, chemical and biological processes. In this paper we investigate the importance of these processes and their relation to algal and non-photosynthetic detrital (NPD) biomass in a set of upland streams in Northern Ireland. Deposit density and Fe, Mn, Al and P concentrations varied with stream pH across sites but not seasonally. No effects of stream bed erosion or photoreduction were detected on deposit densities. Seasonal variation in stream water metal concentrations was correlated with rainfall. NPD biomass was a significant predictor of both spatial and seasonal variation in deposit concentrations. There were strong, non-linear, relations between NPD biomass and deposit metal concentrations, with Fe and Mn becoming relatively more important and algal biomass declining above threshold deposit/NPD densities. The results suggest that NPD biomass influences deposit density and reduces the biomass of photosynthetic autotrophs above a threshold deposit density.

ABSTRACTAimTo investigate the effect of climatic, historical and spatial variables on species richness patterns in freshwater fish.LocationNorthAmerica andEurope.MethodsRegional species lists were used to document the spatial richness patterns. Three realms,Europe andPacific andAtlanticNorthAmerica, were identified. The numbers of species, by habitat, migration and distributional range categories, were calculated and the contributions of regional mean and seasonal temperature and rainfall, historical (realm, glaciation), and spatial (area, elevational range) variables to predicting richness were assessed using boosted regression trees, model‐averaging and spatially explicit models.ResultsThe latitudinal temperature gradient is stronger than that for rainfall in theAtlantic realm whereas the rainfall gradient inEurope is independent of the temperature gradient. Species richness is more strongly correlated with temperature than rainfall, and the effects are stronger in theAtlantic realm than inEurope. The influence of environmental variables differs between habitat specialist and generalist species. Climate, particularly maximum monthly temperature, is the best predictor of richness in rivers whereas climate variables are less important than historical/spatial variables for diadromous species.Main conclusionsFreshwater fish richness differences between realms follow differences in spatial climatic trends. The contributions of climatic, historical and spatial predictor variables vary with ecology: temperature is a better predictor than rainfall in river‐dwellers. The richness gradient is driven more by physiological than by energetic constraints on species. The importance of history is probably underestimated because of correlations with climate variables.

Metal concentrations from stream waters in two geological blocks in Northern Ireland were compared to determine the contributions of catchment characteristics and in-stream conditions. One block is composed of metamorphosed schist and unconsolidated glacial drift with peat or peaty podzol (mainly humic) soils, while the other block consists of tertiary basalt with brown earth and gley soils. Water samples were collected from 52 stream sites and analysed for iron (Fe), manganese (Mn) and aluminium (Al) as well as a range of other chemical determinands known to affect metal solubility. Densities of metal-rich ochre deposit were determined for stream bed stone samples. Higher conductivities and concentrations of bicarbonate, alkalinity, calcium and magnesium occurred on basalt than on schist. Despite higher Fe and Mn oxide concentrations in basalt-derived non-humic soils, stream water concentrations were much lower and ochre deposit densities only one-third of those on schist overlain by humic soils. Neither rock nor soil type predicted Al concentrations, but pH and dissolved oxygen did. Peat-generated acidity and the limited acid neutralising capacity of base-poor metamorphosed schist have resulted in elevated concentrations of metals and ochre deposit in surface waters.

The ecosystem size/trophic structure hypothesis predicts that the shape of body size distributions will change with ecosystem size because of increases in the relative importance of large, predatory, species. I test the hypothesis by examining the statistical moments, as measures of shape, of species body size distributions of North American freshwater fish assemblages in lakes. Species lists, coupled with dietary and body size information, are used to document the patterns. Body size distributions in small lakes are unimodal and right-skewed, but distributions become more symmetrical and bimodal in large ecosystems. In small lakes, body sizes are generally small and fish trophic levels low, but size and trophic level increase up to lake volumes of about 0.001km3, and change little in larger lakes. Adding trophic level to the analysis greatly improves the variance explained by the body sizelake size relation. The conclusions of Griffiths (2012, Global Ecology & Biogeography 21: 383-392), that postglacial recolonisation and evolutionary change are important determinants of body size distributions at regional and larger scales, are combined with those of this study. Mean body size in local assemblages of lake-dwelling species is larger than in regional and continental ones. Overall, body size distributions are affected by processes operating at a variety of spatial and temporal scales, with the type, size and duration of the ecosystem probably playing a central role by influencing the proportions of vagile and predatory species, the species which dominate the large size mode.

Summary 1. Managing populations of predators and their prey to achieve conservation or resource management goals is usually technically challenging and frequently socially controversial. This is true even in the simplest ecosystems but can be made much worse when predator–prey relationships are influenced by complex interactions, such as biological invasions, population trends or animal movements. 2. Lough Neagh in Northern Ireland is a European stronghold for pollan Coregonus autumnalis, a coregonine fish and for river lamprey Lampetra fluviatilis, which feeds parasitically as an adult. Both species are of high conservation importance. Lampreys are known to consume pollan but detailed knowledge of their interactions is scant. While pollan is well known to be a landlocked species in Ireland, the life cycle of normally anadromous river lamprey in Lough Neagh has been unclear. The Lough is also a highly perturbed ecosystem, supporting several invasive, non‐native fish species that have the potential to influence lamprey–pollan interactions. 3. We applied stable isotope techniques to resolve both the movement patterns of lamprey and trophic interactions in this complex community. Recognizing that stable isotope studies are often hampered by high‐levels of variability and uncertainty in the systems of interest, we employed novel Bayesian mixing models, which incorporate variability and uncertainty. 4. Stable isotope analyses identified trout Salmo trutta and non‐native bream Abramis brama as the main items in lamprey diet. Pollan only represented a major food source for lamprey between May and July. 5. Stable isotope ratios of carbon in tissues from 71 adult lamprey showed no evidence of marine carbon sources, strongly suggesting that Lough Neagh is host to a highly unusual, nonanadromous freshwater population. This finding marks out the Lough’s lamprey population as of particular scientific interest and enhances the conservation significance of this feature of the Lough. 6. Synthesis and applications. Our Bayesian isotopic mixing models illustrate an unusual pattern of animal movement, enhancing conservation interest in an already threatened population. We have also revealed a complex relationship between lamprey and their food species that is suggestive of hyperpredation, whereby non‐native species may sustain high lamprey populations that may in turn be detrimental to native pollan. Long‐term conservation of lamprey and pollan in this system is likely to require management intervention, but in light of this exceptional complexity, no simple management options are currently supported. Conservation plans will require better characterization of population‐level interactions and simulation modelling of interventions. More generally, our study demonstrates the importance of considering a full range of possible trophic interactions, particularly in complex ecosystems, and highlights Bayesian isotopic mixing models as powerful tools in resolving trophic relationships.

Haplotype networks are commonly used for representing associations between sequences, yet there is currently no straightforward way to create optimal layouts. Automated optimal layouts are particularly useful not only because of the time-saving element but also because they avoid both human error and human-induced biases in the presentation of figures. HapStar directly uses the network connection output data generated from Arlequin (or a simple user-generated input file) and uses a force-directed algorithm to automatically lay out the network for easy visualization. In addition, this program is able to use the alternative connections generated by Arlequin to create a minimum spanning tree. HapStar provides a straightforward user-friendly interface, and publication-ready figures can be exported simply. HapStar is freely available (under a GPLv3 licence) for download for MacOSX, UNIX and Windows, at http://fo.am/hapstar.

Published species lists were analysed to determine the contributions of dispersal, habitat preference, river channel size, body size, and glacial history to large-scale patterns in freshwater fish species richness in North America, north of central Mexico. Total species richness declines to the north and west but the pattern for endemics differs from that of widespread species. Mississippi Basin regions are more species rich than more isolated, coastal, regions. Richness declines more rapidly with increasing latitude in riverine specialist than in habitat generalist species. Levels of endemism are greatest in species found in small- to medium-sized river channels. The strong Rapoport effect, more marked in migratory than resident species, is correlated with habitat preference, channel size, and glacial history. Body size increases with latitude, largely as a result of a trend from small resident to large migrant species. In unglaciated regions, ancestral species survived in large habitats because these are longer-lived, more extensive, less isolated and more stable than headwaters, permitting larger populations and lower extinction levels. Reduced levels of gene flow in small, peripheral, channels isolated by larger downstream habitats have resulted in the production of many, small range, small-bodied species. The latitudinal richness gradient is a consequence of speciation and extinction events in unglaciated faunas and an increasing domination of faunas by generalist, large bodied, large channel, recolonizing species in more northern regions. (C) 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 100, 46-61.

Two models to predict the food of predators are proposed. They assume that prey size and prey abundance are the only availability factors of importance to predators. One model assumes that the predator consumes prey as they are encountered, and the other that predators feed to maximize their energy intake. Previous work, principally from aquatic situations, is examined to test the models. It is concluded that many invertebrates and larval vertebrates eat prey as they are encountered while adult vertebrates feed as energy maximizers. The limitations of the models are discussed and their relation to models of optimal diet examined.

Summary1. The glacial relict, Mysis relicta, which occurs mainly in unproductive cold water habitats, shows increased mortality rates in temperatures above 16–18 °C. Using a 12‐year data set the growth, mortality and fat stores of Mysis in Lough Neagh, an increasingly hypertrophic lake which lacks a thermal refuge and which is subject to warming, were investigated.2. Mysis showed a significant reduction in fat stores on reaching sexual maturity, contrary to studies elsewhere.3. The contributions of temperature and eutrophication (total phosphorus, chlorophyll‐a concentrations) to growth, mortality and the timing and duration of developmental events were investigated by regression.4. Water temperatures rose between 1994 and 2005 and the time when temperatures exceeded 16 °C doubled over this period. Juvenile and adult growth rates declined and the duration of the juvenile stage increased in warmer years. Eutrophication also affected these variables but, in general, to a lesser extent than temperature.5. Year class strength (YCS) declined by a factor of 10 over the study period. YCS was independent of temperature up to 2000 °C degree days (>4 °C) but declined steeply above that point. Temperature was more important than eutrophication in predicting mortality and YCS. YCS was positively correlated with the length of time water temperature was below 7 °C, the upper temperature for Mysis breeding.6. An established bioenergetic model predicted that water temperature and the timing of embryo release would have appreciable effects on Mysis viability. It also indicated that Mysis would lose mass at summer temperatures, consistent with the observed fat decline.