Development of a multi-primer metabarcoding approach to understand trophic interactions in agroecosystems

Knowing which arthropod and plant resources are used by generalist predators in agroecosystems is important to understand trophic interactions and the precise ecological role of each predatory species. To achieve this objective, molecular approaches, such as the use of high-throughput sequencing (HTS) platforms are key. This study develops a multi-primer metabarcoding approach and explores its suitability for the screening of the most common trophic interactions of two predatory species of arthropod with contrasted morphology, Rhagonycha fulva (Coleoptera: Cantharidae) and Anthocoris nemoralis (Hemiptera: Anthocoridae) collected in an organic peach crop. To save time and cost in this metabarcoding approach, we first evaluated the effect of two different predator-pool sizes (10 and 23 individuals of the same species), as well as the performance of using one or two primer pairs in the same library. Our results show that the analysis of 23 individuals together with the use of two primer pairs in the same library optimizes the HTS analysis. With these best-performing conditions, we analyzed whole bodies of field-collected predators as well as the washing solutions used to clean the insect bodies. Results showed that we were able to identify both, gut content (i.e. diet) as well as external pollen load (i.e. on the insects body), respectively. This study also demonstrates the need of washing predatory insects prior to HTS analysis when the target species have a considerable size and hairy structures. This metabarcoding approach has a high potential for the study of trophic links in agriculture, revealing both expected and unexpected trophic relationships.

PREDATORY INTERACTION BETWEEN TWO ANURAN SPECIES WITH Thamnodynastes chaquensis (COLUBRIDAE) IN THE BRAZILIAN CERRADO

Although predatory events are uncommon to be recorded in nature, these data are important tools for understanding prey-predator interaction of the involved species. Snakes of genus Thamnodynastes are known for having an anuran diet, including some species of hylid frogs in their diet. Despite this, this pattern does not include T. chaquensis since there are no records on predation or trophic interaction with hylid frogs.Here, we report the first predatory interaction between T. chaquensis and two hylid frogs in Brazilian Cerrado. The first predation event with treefrog Boana caiapo occurred with success but, the second with B. albopunctatadid not. Connecting trophic links within an ecosystem requires in-depth knowledge of its species and their intraspecific interactions. In this context, records of the predation and predation attempts such as these may help to connect unknown trophic links, which helps to understand aspects of the natural history of the species involved.

Trophic Links of the Blackbird (Turdus merula Linnaeus, 1758) in Transformed Forest Ecosystems of North-Eastern Ukraine

The blackbird (Turdus merula Linnaeus, 1758; Passeriformes, Turdidae) diet was studied to contribute to the conservation of the species population in transformed forests of the north-eastern part of Ukraine. Four forest ecosystems were studied: 3 model sites in the oak forests, transformed under intensive recreation pressure, and 1 model site in a pine-oak forest. A total of 44 invertebrate taxa, dominated by Insecta (78.1%, n = 1075), were found. The order Lepidoptera (63.5%) prevailed. In the diet of blackbird nestlings, the highest number of taxa (37.1–52.2%) was represented by phytophages. The phytophagous species also constituted the majority of the consumed prey items (58.8–72.0%). Environmental conditions provided an important effect on the diet structure. The most favourable foraging conditions for the species were found in protected natural areas. According to the analysis, the blackbird foraging efficiency was similar in all the studied sites. The highest biodiversity indices were found in a protected area of Homilshanski Forests National Nature Park. Results of the research have indicated a crucial role of T. merula in the population management of potentially dangerous agricultural pests.

Acarocomplex of grape plantations of the South of Ukraine

Goal. To determine the species composition, dominant species, and territorial distribution of predatory and herbivorous ticks (phytophages) in the vineyards of southern Ukraine. Methods. Field — route surveys of vineyards to study the fauna, trophic links and colonization of vineyards with ticks. Laboratory — determination of the species composition of representatives of the acarofauna of vineyards. Results. During the study period, 17 species of ticks belonging to different trophic groups were identified, among which ticks dominate — phytophages of the Tetranychidae and Eriophyidae families. The most common among them were mites — phytophages, namely spider mites (Shhizotetranychus Oud., Tetranychus turkestanicus Ug.et Nich). Pests during the growing season go through four phases: prodromal, eruptive, gradation maximum and crisis. The graduation maximum phase, which is characterized by their greatest number, was noted during the period of intensive growth of berries and falls at the end of June — beginning of August (BBCH 71—79). The dynamics of the number of ticks by varieties is shown. The varieties most susceptible to spider mites were identified, the period of technical ripeness of which is medium, late or very late. Conclusions. Identified 17 species of ticks belonging to different trophic groups: phytophages, acariphages and mycophages. Based on observations of changes in the number of pests on vineyards during the growing season, four phases are distinguished. The graduation maximum phase occurs at the end of June — beginning of August (VVSN 71—79). It was established that all the studied grape varieties were populated by mites to varying degrees, the most susceptible were varieties of medium and late ripening.

Community Dynamics

Ecological theory indicates that increasing the number of species, the number of interactions, and the strength of these interactions all tend to make communities less stable. Conversely, stability is enhanced by strong intraspecific density dependence, low connectivity, or weak trophic links. These theoretical predictions are borne out in many fish communities. Species diversity is an important metric for ecological communities. Organizing species into groups according to size, function, or diet composition can reduce the dimensionality of fish community models. Analyses of fish communities from around the world lend support to the prediction of strong compensation within functional groups, with weaker predator–prey links among groups. Size spectra describe the distribution of individuals across size classes irrespective of their species. Qualitative models can be used to assess the indirect effects of species on each other and the overall stability of the community.

Trophic links of the chaffinch (Fringilla coelebs) in transformed forest ecosystems of North-Eastern Ukraine

The сhaffinch (Fringilla coelebs Linnaeus, 1758; Passeriformes, Fringillidae) is one of the most colourful forest species of birds living in Europe, West Asia and North Africa. The diet of this species was studied as a contribution to the conservation of the population of this species in transformed forests of the north-eastern part of Ukraine. Four forest ecosystems were studied: three model sites in oak forests, transformed under intensive recreation pressure, and one model site in a pine-oak forest. A total of 39 invertebrate taxa, dominated by Insecta (93.0%) were found. The orders Coleoptera (32.6%) and Lepidoptera (63.5%) prevailed in the diet of finch nestlings, the highest number of taxa (52.3–76.2%) was represented by phytophages. The phytophagous species also constituted the majority of the consumed prey items (44.0–55.6%). Environmental conditions provided an important effect on the diet structure. The most favourable foraging conditions for the species were found in protected natural areas. According to the analysis, the finch foraging efficiency was similar in all the studied sites. The highest biodiversity indices were found in a protected area of Homilshanski Forests National Nature Park. Results of the research have indicated the crucial role of Fringilla coelebs in the population management of potentially dangerous agricultural pests.

Large daphniids are keystone species that link fish predation and phytoplankton in trophic cascades

Daphniids act as keystone species in lake ecosystems by controlling phytoplankton biomass and experiencingintense fish predation. However, the importance of single daphniid species as trophic links betweenphytoplankton and fish remains unclear, especially compared with other zooplankton taxa. To disentangle the roleof individual zooplankton taxa in the food web of a large lake, we performed an in-situ mesocosm experiment withnatural phytoplankton and zooplankton communities in three treatments with native, invasive or no fish predators,respectively. A large daphniid, Daphnia longispina, was the zooplankter most strongly predated by both fish species,and also had the highest top-down effects on phytoplankton. All other zooplankton taxa, including a smalldaphniid species, had minor roles in terms of both predation by fish and grazing on phytoplankton. We suggest thatdaphniid species with large body sizes can strongly link higher and lower trophic