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Transfers of organic material from one aquatic environment to another (for example, through flood pulses or animal migrations) allow productive donor ecosystems to subsidise less productive habitats. However, there are big variations in the extent to which different animal species depend on production subsidies. To explore such differences, Australian researchers collected a wide array of […]
March 26, 2018
Comments Off on Freshwater fish surveys: direct observation works well
Although surveys of freshwater fish populations often rely on electrofishing, it’s difficult to use this technique in some habitats. An alternative sampling method is direct observation by snorkelling, an approach often applied in marine environments. While comparisons of the sampling efficiency of electrofishing and snorkelling have been carried out, most of them have been based […]
September 25, 2017
Comments Off on Predatory fish control prey populations – but not when the prey are other fish
Many lake studies have shown that predatory fish feeding on plankton or bottom-living invertebrates have a strong influence on the density, species composition and size structure of prey populations. Typically, there’s an inverse relationship between predator and prey populations, both in terms of density and in mean body size. However, there have been few reports […]
June 19, 2017
Comments Off on How the terrestrial landscape affects aquatic dispersal
How does the surrounding terrestrial landscape affect the dispersal of pond-dwelling organisms? Although some studies suggest that small aquatic crustaceans can disperse efficiently across a range of intervening environments, other work has pointed to dispersal limitation, especially over large distances. Czech researchers examined the passive dispersal of microcrustaceans (cladocerans, copepods, and ostracods) by comparing communities […]
December 13, 2016
Comments Off on Factoring history into threat assessments
Genetic variation allows populations to adapt to environmental changes, and it’s often the case that threatened species exhibit low genetic diversity. Human-produced habitat fragmentation is a well-recognised cause of genetic bottlenecks, but the additional effects of larger-scale biogeographic factors are rarely considered. As an example of such biogeographic impacts, populations that have managed to survive […]
December 13, 2016
Comments Off on Deciding on sites for conservation
Biodiversity conservation is hampered by the fact that many species haven’t been described and most species ranges haven’t been mapped. As a result, in selecting sites for protection, natural resource managers often resort to the use of surrogate indicators for the species that they wish to conserve. Surrogates may be other, more common, species, or […]
December 13, 2016
Comments Off on Top predator boosts species richness – but not in alien ecosystems
The spiny water flea Bythotrephes longimanus is a large cladoceran, a specialised carnivore and a top predator. Invasions of North American lakes by Bythotrephes have been linked to dramatic changes in food web structure and reductions in species diversity, which seems to contradict the expectation that top predators increase the evenness and diversity of aquatic […]
March 26, 2018
Comments Off on Why are there so many crocodiles in tropical waterholes?