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La Trobe University Faculty of Science, Technology and Engineering Murray Darling Freshwater Research CentreMDFRC item.We assessed the extent of temporal variation and autocorrelation in fish habitatuse based on an experimental study of individual 0+ juvenile barbel, Barbus barbus, in anartificial flume. Five treated and five control fish were individually subjected to an increasein discharge (intervention) halfway through each experiment and kept at baseline dischargethroughout, respectively. Preference curves for velocity were generated for each of 60 trials perexperiment and for each combination of treated/control (fish) × before/after-intervention. Therewere large between- and within-individual differences in velocity preference, both in treated andin control fish. Most barbel explored the entire range of velocities, whereas some individualsused a more limited range. Temporal variation in behavioural responses was assessed by a PCAbasedmethodology. Autocorrelation (i.e. correlation between sequential trials) was diagnosedin most response profiles, supporting recent findings that individuals may have a ‘memory’of their past velocity usage. The relevance of the results for numerical habitat models of fishhabitat assessment is discussed, as well as the importance of incorporating temporal variabilityinto fish habitat use models (e.g. PHABSIM), not only as ontogenetic intervals but also aslongitudinal data of individual behaviours. A warning is also re-issued about the erroneous beliefof ‘pseudoreplication’ simply arising from repeated measurements in time.

International audience; As one of the foremost global forcings, tidal circulation exerts a pervasive influence on biological and physical processes occurring in the world's oceans on hourly to decadal time scales. This research identified the 18.6-year periodic variation in the lunar orbital plane within an annually resolved 140-year (1875 to 2015) shell growth master chronology measured from 21 live collected Arctica islandica, a bivalve known to be one of the longest lived non-colonial animals. The potential ecological implications of this result warranted detailed inventory of underlying physical processes. The absence of long-term in situ hydrological data for the bivalve's habitat was circumvented by the use of satellite data and numerical modeling which show that coastal regions of the Northwest Atlantic shelf clearly record diurnal tidal currents influenced by the 18.6-year nodal lunar cycle. The approach described here demonstrates that combining physical and biological data can help to identify subtle ecological processes over long time-scales for accurately disentangling the latter from variation introduced by anthropogenic climate change.

Highlights: • Invasive Corbicula clam shells significantly influenced predation by fish. • Invader-driven benthic habitat complexity can stabilise fish feeding rates. • Invasive goby, N. melanostomus, better tolerated shell-driven habitat complexity. • Higher shell densities exacerbated the invader impact relative to native C. gobio. • Invader-driven abiotic factors can underpin facilitative interactions. Interactions between multiple invasive alien species (IAS) might increase their ecological impacts, yet relatively few studies have attempted to quantify the effects of facilitative interactions on the success and impact of aquatic IAS. Further, the effect of abiotic factors, such as habitat structure, have lacked consideration in ecological impact prediction for many high-profile IAS, with most data acquired through simplified assessments that do not account for real environmental complexities. In the present study, we assessed a potential facilitative interaction between a predatory invasive fish, the PontoCaspian round goby (Neogobius melanostomus), and an invasive bivalve, the Asian clam (Corbicula fluminea). We compared N. melanostomus functional responses (feeding-rates under different prey densities) to a co-occurring endangered European native analogue fish, the bullhead (Cottus gobio), in the presence of increased levels of habitat complexity driven by the accumulation of dead C. fluminea biomass that persists within the environment (i.e. 0, 10, 20 empty bivalve shells). Habitat complexity significantly influenced predation, with consumption in the absence of shells being greater than where 10 or 20 shells were present. However, at the highest shell density, invasive N. melanostomus maximum feeding-rates and functional response ratios were substantially higher than those of native C. gobio. Further, the Relative Impact Potential metric, by combining per capita effects and population abundances, indicated that higher shell densities exacerbate the relative impact of the invader. It therefore appears that N. melanostomus can better tolerate higher IAS shell abundances when foraging at high prey densities, suggesting the occurrence of an important facilitative interaction. Our data are thus fully congruent with field data that link establishment success of N. melanostomus with the presence of C. fluminea. Overall, we show that invader-driven benthic habitat complexity can alter the feeding-rates and thus impacts of predatory fishes, and highlight the importance of inclusion of abiotic factors in impact prediction assessments for IAS.

Aging is the price to pay for acquiring and processing energy through cellular activity and life history productivity. Climate warming can exacerbate the inherent pace of aging, as illustrated by a faster erosion of protective telomere DNA sequences. This biomarker integrates individual pace of life and parental effects through the germline, but whether intra- and intergenerational telomere dynamics underlies population trends remains an open question. Here, we investigated the covariation between life history, telomere length (TL), and extinction risk among three age classes in a cold-adapted ectotherm ( Zootoca vivipara ) facing warming-induced extirpations in its distribution limits. TL followed the same threshold relationships with population extinction risk at birth, maturity, and adulthood, suggesting intergenerational accumulation of accelerated aging rate in declining populations. In dwindling populations, most neonates inherited already short telomeres, suggesting they were born physiologically old and unlikely to reach recruitment. At adulthood, TL further explained females’ reproductive performance, switching from an index of individual quality in stable populations to a biomarker of reproductive costs in those close to extirpation. We compiled these results to propose the aging loop hypothesis and conceptualize how climate-driven telomere shortening in ectotherms may accumulate across generations and generate tipping points before local extirpation. International audience

Stress hormones and their impacts on whole organism metabolic rates are usually considered as appropriate proxies for animal energy budget that is the foundation of numerous concepts and models aiming at predicting individual and population responses to environmental stress. However, the dynamics of energy re-allocation under stress make the link between metabolism and corticosterone complex and still unclear. Using ectopic application of corticosterone for 3, 11 and 21 days, we estimated a time effect of stress in a lizard (Zootoca vivipara). We then investigated whole organism metabolism, muscle cellular O-2 consumption and liver mitochondrial oxidative phosphorylation processes (O-2 consumption and ATP production) and ROS production. The data showed that while skeletal muscle is not impacted, stress regulates the liver mitochondrial functionality in a time-dependent manner with opposing pictures between the different time expositions to corticosterone. While 3 days exposition is characterized by lower ATP synthesis rate and high H2O2 release with no change in the rate of oxygen consumption, the 11 days exposition reduced all three fluxes of about 50%. Oxidative phosphorylation capacities in liver mitochondria of lizard treated with corticosterone for 21 days was similar to the hepatic mitochondrial capacities in lizards that received no corticosterone treatment but with 40% decrease in H2O2 production. This new mitochondrial functioning allows a better capacity to respond to the energetic demands imposed by the environment but do not influence whole organism metabolism. In conclusion, global mitochondrial functioning has to be considered to better understand the proximal causes of the energy budget under stressful periods. International audience

Male lizards often display multiple pigment-based and structural colour signals which may reflect various quality traits (e.g. performance, parasitism), with testosterone (T) often mediating these relationships. Furthermore, environmental conditions can explain colour signal variation by affecting processes such as signal efficacy, thermoregulation and camouflage. The relationships between colour signals, male quality traits and environmental factors have often been analysed in isolation, but simultaneous analyses are rare. Thus, the response of multiple colour signals to variation in all these factors in an integrative analysis remains to be investigated.Here, we investigated how multiple colour signals relate to their information content, examined the role of T as a potential mediator of these relationships and how environmental factors explain colour signal variation.We performed an integrative study to examine the covariation between three colour signals (melanin-based black, carotenoid-based yellow–orange and structural UV), physiological performance, parasitism, T levels and environmental factors (microclimate, forest cover) in male common lizards Zootoca vivipara from 13 populations.We found that the three colour signals conveyed information on different aspects of male condition, supporting a multiple message hypothesis. T influenced only parasitism, suggesting that T does not directly mediate the relationships between colour signals and their information content. Moreover, colour signals became more saturated in forested habitats, suggesting an adaptation to degraded light conditions, and became generally brighter in mesic conditions, in contradiction with the thermal melanism hypothesis.We show that distinct individual quality traits and environmental factors simultaneously explain variations of multiple colour signals with different production modes. Our study therefore highlights the complexity of colour signal evolution, involving various sets of selective pressures acting at the same time, but in different ways depending on colour production mechanism. International audience

Cosmogenic nuclide dating of glacial landforms on the Kerguelen Archipelago (49°S, 69°E) gives the opportunity to study multi-millennial glacier fluctuations within the sub-Antarctic sector of the Indian Ocean. We here dated such geomorphic features to provide time constraints over the last 17,000 years using in situ-produced 36Cl in three glacial valleys: Val Travers valley, Ampere Glacier valley and Arago Glacier valley. For the first time, a combination of in situ-produced 36Cl and 10Be dating and 26Al/10Be ratios analysis was performed in the quartz-bearing syenite boulders of the Arago Glacier site. In addition, a Bayesian approach was computed to obtain a better constraint on moraine dating. Glacial advances occurred during the Late Glacial at 16.0 ± 1.9 ka and at 12.9 ± 1.7 ka in Val Travers, and at 13.6 ± 1.8 ka in Arago Glacier valley, probably linked to the Heinrich Stadial 1 and/or Antarctic Cold Reversal events, respectively. This suggests that all glaciers at this latitude were broadly sensitive to the large-scale climatic signal of the Antarctic Cold Reversal. So far, no Early nor Mid-Holocene moraines have been found in the glacial valleys on Kerguelen, indicating that the glaciers had probably receded significantly during these periods. This is in agreement with previously determined 14C ages from peat bogs, which suggest extensive deglaciation during several millennia of the Holocene period. Samples from glacially-polished bedrock surfaces (ranging from ~4.4 ka to ~14 ka) at Ampere Glacier site also suggest that this valley was ice free for several millennia during the Holocene. Finally, glaciers seem to have re-advanced only during the Late Holocene, especially within the last millennium, at ~1 ka, ~430 yr and ~300 yr. A comparison of this new dataset with the available 10Be ages from other southern mid latitude regions during the Holocene allows the identification of three different glacier evolution patterns. We suspect that variations of Kerguelen glaciers, which are located in the Southern Indian Ocean, were controlled by the combined effects of sea surface temperature related to the variations of the Antarctic Polar Front and fluctuations of precipitation related to long-term variations of the Southern Annular Mode. International audience