River conservation in a changing world: invertebrate diversity and spatial prioritisation in south-eastern coastal Australia

Concentration of human populations with likely impacts of climate change present major challenges for river conservation in the south-eastern coastal region of Australia. Quantitative methods for spatial prioritisation of conservation actions can play a major role in meeting these challenges. We examined how these methods may be applied to help plan for potential impacts of climate change in the region, using macroinvertebrate assemblages as surrogates of river biodiversity. Environmental gradients explaining broad-scale patterns in the composition of macroinvertebrate assemblages are well represented in protected areas; however, their effectiveness for conserving river biodiversity with climate change depends on linking management inside and outside protected areas. Projected increases in temperature and sea level may be used to prioritise conservation to counter likely major impacts in high-altitude zones and the coastal fringes, whereas elsewhere, considerable uncertainty remains in the absence of better downscaled projections of rainfall. Applying such spatial prioritisations using biodiversity surrogates could help river-focussed conservation around the world. </jats:p

Rapid gain and loss of predator recognition by an evolutionarily naïve lizard

The introduction of mammalian predators often results in loss of native biodiversity due to naiveté of native prey to novel predators. In New Zealand, an island system with virtually no native mammalian predators, introduced mammalian predators threaten a large proportion of the native fauna. A critical step in adapting to introduced predators is the ability to recognize and respond to a novel predation threat. Whether New Zealand's lizards can do this has received little attention. We compared the basking behaviour of native McCann's skinks (Oligosoma maccanni) when exposed to a live cat (Felis catus), cat body odour, a model raptor (representing a coevolved predator) or procedural controls. We inferred predator recognition from reductions in individual basking and higher selection for basking sites with greater refuge availability. We tested these behavioural responses for two skink populations: one from an area with high abundance of mammalian predators including feral cats and the other from a fenced conservation reserve where predators have been excluded for over 10 years (3–4 skink generations). Skinks from the high-predator population reduced basking when exposed to cat and raptor cues, whereas skinks from the predator-free population did not. These results suggest that within approximately 150 years of exposure to novel predators, McCann's skinks might be able to recognize the threat posed by invasive mammals. However, they also demonstrate that predator recognition and antipredator behaviours may not necessarily be retained once gained. The rapid loss of basking-related antipredator behaviours might reflect the high fitness costs of reduced basking for this species. Our results indicate that the behavioural response of skinks is flexible and that skinks may maximize individual fitness by balancing the risk of predation with the costs of antipredator behaviours

Interaction between non-native predatory fishes and native galaxiids (Pisces: Galaxiidae) shapes food web structure in Tasmanian lakes

Este artículo contiene 16 páginas, 6 figuras, 5 tablas.Non-native fish invasions threaten native fauna and ecosystem functioning, not least in isolated island lakes. In Tasmania, where the native fish are mostly galaxiids, 9 non-native freshwater fish species have been introduced over the past 150 years, with uncertain ecological outcomes. We evaluated the effects of non-native predatory fishes (NNPF) and various environmental and biological variables on the trophic niche of native fish (galaxiids) and potential cascading effects. We analysed Layman’s food web metrics based on both stable isotope (δ15N and δ13C) values and fish stomach contents in 14 shallow Tasmanian lakes along a NNPF abundance gradient. The food web metrics calculated were (1) range of δ13C (CR) and δ15N (NR) centroid distance (CD) and (2) standard ellipse area. Our results showed that NNPF relative abundance in the fish catch per unit effort was negatively related to the galaxiids’ trophic niche metrics (e.g., CRG, NR G, and CDG), trophic position, and the pelagic contribution to the diet. Moreover, the proportion of galaxiids in the diet of NNPF was higher in turbid lakes. The zooplankton standard ellipse area was negatively correlated with the pelagic contribution to the NNPF diet, and NNPF relative abundance was positively correlated with the maximum body size of calanoid copepods. While our results suggest a negative effect of NNPF on the trophic niche of galaxiids, the cascading effect on phytoplankton biomass was weak. Non-native predatory fish affect native fish prey, and the outcome of these interactions should be considered for conservation purposes, particularly for island lakes, such as those in Tasmania.The project was funded by Galathea 3, Carlsberg, Research Council of Nature and Universe (272-08-0406), the TK Foundation, Dronning Margrethes og Prins Henriks Fond, Torben og AliceFrimodts Fond, Christian og Ottila Brorsons Rejselegat, University of Copenhagen and Aarhus University. MM and NV were funded by SNI-ANII and the L’Oréal UNESCO Women for Science national award with support of DICYT, Uruguay. MV was supported by a Marie Curie post-doctoral grant (MEIF-CT-2005-010554) and TB by a Beatriu de Pinós post-doctoral grant (2005 BP-A 1004). EJ was supported by the MARS project (Managing Aquatic Ecosystems and Water Resources Under Multiple Stress) funded under the EU 7th Framework Programme, Theme 6 (Environment including Climate Change), Contract No.: 603378 (http://www.mars-project.eu), CIRCE and CRES. LAB was supported by the Australian Research Council (LP130100756). CT is a CONICET (Argentinean Council of Science) researcher; Fondation L’Oréal; Sistema Nacional de Investigadores (UY).Peer reviewe

Latitude dictates plant diversity effects on instream decomposition

Abstract Running waters contribute substantially to global carbon fluxes through decomposition of terrestrial plant litter by aquatic microorganisms and detritivores. Diversity of this litter may influence instream decomposition globally in ways that are not yet understood. We investigated latitudinal differences in decomposition of litter mixtures of low and high functional diversity in 40 streams on 6 continents and spanning 113° of latitude. Despite important variability in our dataset, we found latitudinal differences in the effect of litter functional diversity on decomposition, which we explained as evolutionary adaptations of litter-consuming detritivores to resource availability. Specifically, a balanced diet effect appears to operate at lower latitudes versus a resource concentration effect at higher latitudes. The latitudinal pattern indicates that loss of plant functional diversity will have different consequences on carbon fluxes across the globe, with greater repercussions likely at low latitudes

Global patterns and drivers of ecosystem functioning in rivers and riparian zones

Abstract River ecosystems receive and process vast quantities of terrestrial organic carbon, the fate of which depends strongly on microbial activity. Variation in and controls of processing rates, however, are poorly characterized at the global scale. In response, we used a peer-sourced research network and a highly standardized carbon processing assay to conduct a global-scale field experiment in greater than 1000 river and riparian sites. We found that Earth’s biomes have distinct carbon processing signatures. Slow processing is evident across latitudes, whereas rapid rates are restricted to lower latitudes. Both the mean rate and variability decline with latitude, suggesting temperature constraints toward the poles and greater roles for other environmental drivers (e.g., nutrient loading) toward the equator. These results and data set the stage for unprecedented “next-generation biomonitoring” by establishing baselines to help quantify environmental impacts to the functioning of ecosystems at a global scale