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12 avril 2018

Big floods, big knowledge gap : Food web dynamics in a variable river system [Ecology of Freshwater Fish]

Keywords : diet switching, niche breadth, seasonal overlap, trophic guilds

While flow regime is widely recognised as an over‐arching feature structuring aquatic ecosystems, the influence of flood events on feeding habits in fish assemblages inhabiting variable environments remains largely unknown. In this study, we investigated how diets of a fish assemblage changed in response to fluctuations in hydrology in a highly variable, wet‐dry tropical Australian river. We compared dietary habits, trophic guilds and intra‐ and interspecific dietary overlap and diet breadth across different seasons.(...)

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12 avril 2018

Synergistic selection regimens drive the evolution of display complexity in birds of paradise [Journal of Animal Ecology]

Keywords : animal communication, behavioural ecology, display habitat, evolutionary ecology, lek, sexual selection, signal design

1.Integrated visual displays that combine gesture with colour are nearly ubiquitous in the animal world, where they are shaped by sexual selection for their role in courtship and competition. However, few studies assess how multiple selection regimens operate on different components of these complex phenotypes on a macroevolutionary scale.
2.Here, we study this issue by assessing how both sexual and ecological selection work together to influence visual display complexity in the birds of paradise.(...)

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12 avril 2018

The importance of stream interstitial conditions for the early‐life‐stage development of the European nase (Chondrostoma nasus L.) [Ecology of Freshwater Fish]

Keywords : colmation, fish conservation, freshwater fish ecology, spawning ground, stream bed quality

Rheophilic cyprinid populations are in decline in many European rivers and have become target species of conservation and river restoration. This is especially true for the European nase (Chondrostoma nasus), a lithophilic species for which the early life stages pose the first bottlenecks in successful population development. In this study, egg dispersal at the substrate surface as well as within the stream interstitial was evaluated and the development of nase eggs was tested at three spawning grounds in the German Alpine Foreland. New incubation systems for cyprinid eggs as well as reference incubation boxes were developed.(...)

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12 avril 2018

Trophic overlap between non‐native brown bullhead (Ameiurus nebulosus) and native shortfin eel (Anguilla australis) in shallow lakes [Ecology of Freshwater Fish]

Keywords : δ13C, δ15N, diet, gut content, invasive species, isotope, trophic niche

We quantified trophic overlap between the invasive, non‐native catfish brown bullhead (Ameiurus nebulosus) and the New Zealand native shortfin eel (Anguilla australis) in four peat and riverine lakes using stable isotope (δ13C and δ15N) and gut content analyses. Across all lakes and fish sizes over the austral spring–summer period, shortfin eel guts were dominated numerically by fish prey (57% occurrence cf 42% in brown bullhead), while Diptera larvae were most commonly encountered in guts of brown bullhead (45% cf 14% in eels). Significant differences in % composition of animal contents in guts were detected between fish species and sampling occasions (n = 4) but not between lakes. In contrast, stable isotope signatures of brown bullhead and shortfin eel did differ significantly between lakes but not between sampling occasions, indicating enduring sources of nutrition despite apparently differing ingestion patterns over time.(...)

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11 avril 2018

The evolution of immunity in relation to colonization and migration [Nature Ecology & Evolution]

Keywords : evolutionary biology, evolutionary ecology, molecular evolution

Colonization and migration have a crucial effect on patterns of biodiversity, with disease predicted to play an important role in these processes. However, evidence of the effect of pathogens on broad patterns of colonization and migration is limited. Here, using phylogenetic analyses of 1,311 species of Afro-Palaearctic songbirds, we show that colonization events from regions of high (sub-Saharan Africa) to low (the Palaearctic) pathogen diversity were up to 20 times more frequent than the reverse, and that migration has evolved 3 times more frequently from African- as opposed to Palaearctic-resident species.(...)

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