Prey choice by a freshwater copepod on larval Aedes mosquitoes in the presence of alternative prey

Predator-prey interactions can have a significant impact on the abundance and distribution of species, but the outcome of these interactions is often context-dependent. In small freshwater habitats, predacious copepods are potential biological control agents for mosquito larvae. Through laboratory experiments, we tested if the presence of a non-mosquito prey (neonate Daphnia pulex) influenced prey selection of the predaceous copepod (Acanthocyclops vernalis) on 1^st instar Aedes mosquitoes (Aedes aegypti and Aedes albopictus). Copepods were starved for 12 h prior to being exposed to the two prey types (larval mosquitoes and Daphnia) at three densities: 25 mosquitoes:75 Daphnia, 50 mosquitoes:50 Daphnia, 75 mosquitoes:25 Daphnia. Single prey choice trials for each species as well as no-predator trials were also established for controls. Copepods were effective predators, with a single copepod consuming up to 37 1^st instar mosquito larvae during the 24-h trials. The number of mosquitoes consumed increased with their relative density, but the proportion of mosquitoes consumed was highest when Aedes made up only 25% of the population. Results from our study show that in a simple predator/two-prey system, two species of larval mosquitoes (Ae. aegypti and Ae. albopictus) are preferentially consumed over an alternative zooplankton by the copepod predator Acanthocyclops vernalis.

Comprehensive analysis of population genetics of Phoxinus phoxinus ujmonensis in the Irtysh River: Abiotic and biotic factors

As a widely distributed species along the Irtysh River, Phoxinus phoxinus ujmonensis (Kaschtschenko, 1899) was used as a model to investigate genetic diversity and population structure as well as the influence of environmental factors on population genetics. In this study, we specifically developed 12 polymorphic microsatellite loci. The analysis of microsatellite and mtDNA markers revealed a high and a moderate genetic diversity across seven populations, respectively. Moderate differentiation was also detected among several populations, indicating the impact of habitat fragmentation and divergence. The absence of isolation by distance implied an extensive gene flow, while the presence of isolation by adaptation implied that these populations might be in the process of adapting to divergent habitats. Correlation analysis showed that abiotic factors like dissolved oxygen, pH, total dissolved solids, and conductivity in water as well as biotic factors like plankton diversity and fish species diversity had impact on genetic diversity and divergence in P. phoxinus ujmonensis populations. The results of this study will provide an insight into the effect of environmental factors on genetic diversity and contribute to the study of population genetics of sympatric species.

Environmental Drivers of Ranavirus in Free-Living Amphibians in Constructed Ponds

Amphibian ranaviruses occur globally, but we are only beginning to understand mechanisms for emergence. Ranaviruses are aquatic pathogens which can cause > 90% mortality in larvae of many aquatic-breeding amphibians, making them important focal host taxa. Host susceptibilities and virulence of ranaviruses have been studied extensively in controlled laboratory settings, but research is needed to identify drivers of infection in natural environments. Constructed ponds, essential components of wetland restoration, have been associated with higher ranavirus prevalence than natural ponds, posing a conundrum for conservation efforts, and emphasizing the need to understand potential drivers. In this study, we analyzed 4 years of Frog virus 3 prevalence and associated environmental parameters in populations of wood frogs (Lithobates sylvaticus) and green frogs (Lithobates clamitans) in a constructed pond system. High prevalence was best predicted by low temperature, high host density, low zooplankton concentrations, and Gosner stages approaching metamorphosis. This study identified important variables to measure in assessments of ranaviral infection risk in newly constructed ponds, including effects of zooplankton, which have not been previously quantified in natural settings. Examining factors mediating diseases in natural environments, particularly in managed conservation settings, is important to both validate laboratory findings in situ, and to inform future conservation planning, particularly in the context of adaptive management.