Specialization directs habitat selection responses to a top predator in semiaquatic but not aquatic taxa

Habitat selection ecology of the aquatic beetle community using explainable machine learning

The aim of our work is to determine the importance of habitat features for the selection of the aquatic beetle community. Insects are represented by their general ecological traits such as body size, ecological element and trophic type, which are categorised into four body size ranges, four ecological groups and four trophic types. To determine the importance of habitat selection of the studied insects, we analysed the relationships between the above categories and the set of habitat features of the lake and its surroundings. Ensemble machine learning modelling (XGBoost-SHAP) revealed the mechanism of habitat feature selection in relation to the general ecological traits. We found strong interactions between the body size, ecological element and trophic type of beetles, suggesting that these general traits control the structure and functioning of the beetle community studied. The area of the lake and the features of beetle occurrence in the aquatic environment play an important but secondary role, and the importance of the characteristics of the lake's riparian zone was minimised. We found several categories of beetles as they select the number of the same habitat features. The study can provide valuable information for the practical conservation and management of lake ecosystems.

Easternmost distribution of Bufo bufo (Linnaeus, 1758) in Türkiye: implications for the putative contact zone between B. bufo and B. verrucosissimus

The geographic range of a species is crucial for obtaining information on the exact distribution of the species. The geographic data are important for delimiting distinct species or exploring the degree of differentiation among different populations of a species. The local details of species boundaries facilitate the study of the importance of phylogeographic background, secondary contacts, and hybrid zones, along with the relations between the species and its extrinsic environmental factors. In the present study, the range boundaries of Bufo bufo and Bufo verrucosissimus in the north-eastern region of Türkiye were delineated using an integrative taxonomic approach that utilized a combination of molecular and morphological data. According to the mtDNA results of the present study, B. bufo inhabits a single distribution from İyidere town to Çayeli town in Rize, while B. verrucosissimus is distributed from Şavşat town of Artvin to Ardeşen town in Rize. In addition, the two species coexist in Pazar, Hemşin, and Çamlıhemşin towns in Rize. The demographic analyses indicated a distinct population expansion for the B. verrucosissimus species after the Last Glacial Maximum, while the same did not occur for B. bufo. The univariate and multivariate statistical analyses conducted for the morphological data of the two species corroborated the presence of a putative contact zone between B. bufo and B. verrucosissimus. In summary, the present study resolved the non-distinct geographic boundaries between B. bufo and B. verrucosissimus species and also revealed the easternmost distribution of B. bufo in Türkiye. In addition, important evidence on the putative contact zone between the two species was indicated using an integrative taxonomic approach.

Individual variability in habitat selection by aquatic insects is driven by taxonomy rather than specialisation

Habitat selection, the choice of a habitat based on its perceived quality, is a key mechanism structuring freshwater communities. To date, individual variability in habitat selection has been neglected, and specialisation has never been considered in this type of studies. We examined the individual differences in the habitat selection of backswimmers (Notonectidae) and diving beetles (Dytiscidae). From each family, we selected one habitat generalist able to coexist with fish (Notonecta glauca, Dytiscus marginalis), and one species specialised to fishless habitats (Notonecta obliqua, Acilius sulcatus). We performed a mesocosm experiment quantifying the consistency in individuals' decisions in response to fish and vegetation structure, in relation to sex and specialisation. Neither the overall pattern of preferences nor consistency in individuals' decisions differed between specialists and generalists or between the sexes, but both were consistent within families. At the population level, backswimmers preferred fishless pools with submersed and floating macrophytes, while diving beetles showed no clear preferences. Individual decisions of backswimmers were consistent and likely driven by conspecific/heterospecific attraction. In diving beetles, individual decisions were primarily density-dependent. Our results reinforce the significance of habitat selectivity for aquatic community assembly, while suggesting a range of mechanisms driving variability in individual behaviour.

Highway stormwater ponds as islands of Odonata diversity in an agricultural landscape

Stormwater management ponds, which are constructed to retain excess runoff and pollutants from traffic, play an important role in the freshwater biodiversity in highly modified areas. However, their roles in agricultural and semi-natural landscapes remain largely unexplored. In this study, we used Odonata as a bioindicator to compare a set of highway stormwater ponds and surrounding ponds within an agricultural and semi-natural landscape to examine the extent to which stormwater ponds act as biodiversity refuges. We analyzed the differences in environmental parameters and the richness, compositions, and conservation values of the odonate communities of stormwater and surrounding ponds. We also examined the factors controlling the differences in the communities of both pond types. The stormwater ponds were smaller, less eutrophicated, less shaded by trees, less stocked with fish, and less connected with other waterbodies than the surrounding ponds. However, they had a higher plant diversity and pH values and were more densely overgrown with vegetation. Compared with surrounding ponds, stormwater ponds had a higher Odonata richness and β-diversity, but their taxonomic distinctness was significantly lower. Therefore, stormwater ponds hosted more variable communities but their assemblages were taxonomically similar. Indicator species were only identified in stormwater ponds. Furthermore, stormwater ponds harbored more species with higher conservation values. The most important factors affecting the differences between stormwater and surrounding ponds were the trophic state, relative tree shading, and fish stocking intensity. With their increase, the richness and rarity decreased. Our results highlight the potential of stormwater ponds to enhance the biodiversity outside urban areas by providing specific habitat conditions that are unique to the surrounding agricultural landscape. In addition, we suggest management practices that can be used to enhance their biodiversity conservation function.

Strong Behavioral Effects of Omnivorous Fish on Amphibian Oviposition Habitat Selection: Potential Consequences for Ecosystem Shifts

Perceived predation risk to offspring may have similar ultimate community-level impacts to those of consumptive trophic interactions. The present study investigated the behavioral effects of common carp Cyprinus carpio–an omnivorous fish capable of triggering an ecosystem shift to an algae-dominated state–on anurans, using a natural experiment conducted in a system of fish-stocked ponds. We compared oviposition patterns and larval densities of anurans and abundance of zooplankton and phytoplankton in ponds where fish were virtually absent and ponds where common carp was dominant. All studied anuran species bred in fish-poor ponds, while in ponds with high fish densities most of them oviposited infrequently or virtually did not breed. Oviposition habitat selection coupled with fish trophic pressure resulted in diametrically different tadpole densities between fish-poor and fish-dominated ponds. The alimentary tract contents of tadpoles of three locally common anurans, Pelobates fuscus, Hyla orientalis, and Rana temporaria, contained large numbers of unicellular algae, but also significant numbers of zooplanktonic grazers. According to stable nitrogen isotope analyses, tadpoles occupied a trophic level similar to a primary consumer, snail Lymnaea stagnalis, indicating that they fed mainly on algae. While total biomass of crustacean zooplankton did not differ between pond types, chlorophyll a concentrations were low in fish-poor ponds compared to fish-dominated ponds and negatively related to total tadpole biomass. Our findings indicate that scarcity of anuran larvae, resulting mainly from the behavioral responses of breeding anurans to fish predation risk, may facilitate algal production, although ecosystem shifts in the presence of fish occur along more pathways than a top-down cascade.