Current temperatures limit the potential impact of a commonly traded predatory gastropod

The pet trade has facilitated the spread of invasive alien species (IAS) globally, with negative consequences for biodiversity. The prediction of impacts is a major goal for invasion ecologists, and is especially crucial in an industry often lacking knowledge about traded species. We focused on the predatory gastropod Anentome helena, a species originating in south-east Asia and traded around the world, but with taxonomic uncertainty. We first set out to determine where our study organism fell within the A. “helena” species complex, known to comprise at least four cryptic species, before assessing the effect of temperature on the number of prey, the pulmonate snail Physella acuta, killed per predator via functional response experiments at two temperatures. We used 22 °C as a recommended temperature for housing the species in captivity, and 18 °C as a representative summer lake temperature in temperate climates of Europe. We also assessed the role of predator group size (1×, 2×, 3×) on predation (total consumption and average per capita consumption) at the experimental temperatures with fixed densities of prey, as well as the effect of these temperatures on prey activity. Our organisms belonged to a cryptic species originating from Thailand (Anentome sp. A), matching the findings of aquarium trade samples in other continents. In the functional response experiments, we found maximum feeding rate to be significantly reduced at the lower temperature. A similar result ensued from group feeding, with total consumption significantly reduced and the reduction in average per capita consumption approaching significance at the lower temperature. There was no significant effect of group size on the average per capita consumption in the group trial, indicating neutral conspecific interactions. No significant effect of temperature on the activity of the prey species was found, suggesting decreased consumption was mainly driven by predator, rather than prey. These results suggest limited A. helena impacts in the short-term, but increasing temperatures with climate change may facilitate greater consequences from releases. We suggest future studies assess other potential predatory impacts and survival across relevant abiotic conditions, and encourage the use of similar methods to assess the impacts of other commonly traded species

The first records of Niphargus hrabei and N. potamophilus in Ukraine and Bulgaria significantly enlarge the ranges of these species

Niphargus comprises hundreds of narrowly-endemic West Palaearctic subterranean taxa. However, a few exceptional species inhabit surface waters and have remarkably large ranges. Herein, based on morphological and molecular analyses, we provide important new records for two of these species. N. potamophilus, previously known from the eastern Azov Sea lowlands, is reported for the first time from Ukraine and Bulgaria from localities adjacent to the Black Sea. These findings expand its range westward by more than 1000 km along the coastline. From Bulgaria, we also report for the first time N. hrabei, a species previously known to occur along the middle and lower Danube lowlands and in isolated populations at the foothills of the Northern Caucasus. Our new record thus extends its range southwards by more than 150 km. Both species contained unique haplotypes at all of the sampled localities. These were, nevertheless, not very divergent from more distant populations, emphasizing their good dispersal ability. Ecologically, the sampling localities were generally characterized by stagnant to low running water, dense vegetation, and muddy substrate. Overall, our results bring important insights, shedding more light on the biogeography and ecology of Niphargus

Seasonal changes in biodiversity of native and non-native amphipod taxa under diverse environmental contexts

Anthropogenic disturbances are having strong, negative effects on aquatic systems globally, altering ecological communities and potentially creating vacant niches for both native and non-native species (NNS). Globalization and new trade routes have amplified the spread and establishment of NNS by connecting disturbed areas worldwide. In this study, we conducted a comparative assessment of seasonal variations in amphipod communities at three southeastern Baltic Sea locations – two anthropogenically impacted and one protected habitat – to determine if native and NNS diversity differed among these habitats. Our study revealed nine amphipod species - of which two were NNS - across all three habitats. The impacted habitats had significantly higher native species richness and lower NNS abundance. Grandidierella japonica was the only NNS found at the impacted habitas. In the case of the protected habitat, NNS Gammarus tigrinus was dominant for most of the year. In autumn, dominance shifted in favour of the native Gammarus locusta and Microdeutopus cf. gryllotalpa. Grandidierella japonica was not detected there. Although anthropogenically impacted habitats may be under higher invasion risk, other environmental factors, such as salinity and temperature, may be driving the establishment pattern of NNS and the resulting community structures. Furthermore, undisturbed and/or protected habitats may be highly vulnerable to invasions due to more tolerable environmental conditions, robust NNS populations and naïve native species to newcomers. Seasonality is an important aspect of ecological studies and must be taken into account, as omissions could potentially distort our understanding of the dynamics of ecosystems and prevent the detection of NNS