Community assembly and metaphylogeography of soil biodiversity: insights from haplotype-level community DNA metabarcoding within an oceanic island

Most of our understanding of island diversity comes from the study of aboveground systems, while the patterns and processes of diversification and community assembly for belowground biotas remain poorly understood. Here we take advantage of a relatively young and dynamic oceanic island to advance our understanding of eco-evolutionary processes driving community assembly within soil mesofauna. Using whole organism community DNA (wocDNA) metabarcoding and the recently developed metaMATE pipeline, we have generated spatially explicit and reliable haplotype-level DNA sequence data for soil mesofaunal assemblages sampled across the four main habitats within the island of Tenerife. Community ecological and metaphylogeographic analyses have been performed at multiple levels of genetic similarity, from haplotypes to species and supraspecific groupings. Broadly consistent patterns of local-scale species richness across different insular habitats have been found, whereas local insular richness is lower than in continental settings. Our results reveal an important role for niche conservatism as a driver of insular community assembly of soil mesofauna, with only limited evidence for habitat shifts promoting diversification. Furthermore, support is found for a fundamental role of habitat in the assembly of soil mesofauna, where habitat specialism is mainly due to colonisation and the establishment of preadapted species. Hierarchical patterns of distance decay at the community level and metaphylogeographical analyses support a pattern of geographic structuring over limited spatial scales, from the level of haplotypes through to species and lineages, as expected for taxa with strong dispersal limitations. Our results demonstrate the potential for wocDNA metabarcoding to advance our understanding of biodiversity.

Soil Mesofauna Responses to Fire Severity in a Sclerophyllous Forest in Central Chile

Forest fires may have severe impacts on the aboveground biodiversity and soil chemical and biological properties. Edaphic organisms are highly sensitive to disturbances and are typically used to measure the magnitude of these events. Overall, little is known about the responses of these organisms to fires differing in their severity levels. This study aimed to assess the effect of fire severity on the soil mesofauna community diversity and structure in a site located in a Mediterranean zone of central Chile. In postfire conditions, we use spectral indexes from satellite images to map fire severity at four levels (non-damage (ND), low damage (L), medium damage (M), high damage (H)). Soil samples were collected at each severity level, and the mesofauna abundance was quantified. Although the metrics describing species diversity and dominance were similar among fire severity levels, the abundance and composition of the mesofauna were specifically altered at the high severity level. The edaphic mesofauna can be considered suitable bioindicators to evaluate the postfire ecosystem recovery, especially in the areas highly damaged by fire.

Long-Term Giant Hogweed Invasion Contributes to the Structural Changes of Soil Nematofauna

Heracleum mantegazzianum (giant hogweed) is the largest central European forb, naturalized or invasive in many European countries. The impacts of its colonization of native habitats on soil mesofauna groups are unfortunately obscure. This study assessed the effect of giant hogweed invasion on the communities of plants and soil nematodes in the riparian habitat. We found that invasion by H. mantegazzianum increased soil pH, decreased carbon and nitrogen content, reduced the number and coverage of the native plant species, and influenced nematode communities and their structures. Nematode species number was significantly lower in invaded than uninvaded plots, but nematode species diversity was not affected by invasion throughout the whole study. Total nematode abundance slightly increased under giant hogweed, while total nematode biomass did not differ between the invaded and uninvaded plots. The higher abundance of bacterivores and fungivores but lower number of omnivorous nematodes well represented the negative impact of giant hogweed invasion on soil food webs, supported by low values of all maturity indices or channel index. The hogweed invaded plots contained higher abundance of plant parasitic nematodes, mainly Paratylenchus microdorus. Our results thus indicate that invasion by H. mantegazzianum influences several nematode communities’ parameters while others remain unaffected by invasion.

ECOLOGICAL AND HYGIENIC ASSESSMENT OF NEW PESTICIDES FOR GRAIN CEREALS CHEMICAL PROTECTION

Relevance. The use of pesticides in the national economy is to destroy or inhibit the growth of harmful plants and to protect crops from pathogens requires a mandatory assessment of their environmental hygienic hazard. Objective of our study is to assess the hazards of three new pesticides for cereal grains protection: amicarbazone from the chemical class of triazolinone compounds, bicyclopyrone from the class of tricetones and pydiflumetofen from the class of carboxamides, in terms of ecotoxicity and environmental behavior. Materials and methods. Hazard assessment of amicarbazone, bicyclopyrone and pydiflumetofen was performed on the basis of data sources on their physico-chemical characteristics, toxicometry parameters for different species of living things and indicators of environmental behavior. For potential hazards integral assess for terrestrial ecosystems an ecotox was calculated taking into account mammalian toxicity, persistence and maximum rate consumption. To identify the limiting section of migration, the mathematical modeling was performed in the systems "soil-water", "soil-plants" and "soil-atmospheric air". Results. Amicarbazone has been shown to be extremely toxic to algae and highly toxic to higher aquatic plants (HAP) (hazard class I), moderately toxic (class IV) to mammals, mildly toxic (class III) to birds, soil mesofauna and invertebrates, virtually non-toxic to bees and fish; bicyclopyrone - extremely toxic to HAP (class I) and moderately toxic (class II) to the most sensitive algae, mildly toxic (class III) to birds, fish and invertebrates and virtually non-toxic to other terrestrial fauna; pydiflumetofen is highly toxic (class I) to fish and invertebrates, moderately toxic (class II) to algae and HAP, virtually non-toxic to all terrestrial biota. Pydiflumetofen has been shown to be a highly resistant and poorly mobile in soil; amicarbazone is stable and mobile; bicyclopyrone is highly resistant in laboratory experiments and moderately stable in field experiments, its mobility varies in a wide range: from very mobile to less mobile in some soils. The danger for terrestrial biocenoses of all studied pesticides under different soil and climatic conditions is lower by (1–5) orders of magnitude in comparison with DDT; the lowest is the ecotoxicity of bicyclopyrone, the highest – pydiflumetofen. All test substances are highly stable in water. The leading section of their migration in environment is the system "soil – water of ponds" and in case of pydiflumetofen – "soil – plants" as well.

Mesofauna assemblages on the extraradical mycelium of Pinus greggii roots with three ectomycorrhizal fungi

Background: The extraradical mycelium (ERM) of ectomycorrhizal fungi is a network inhabited by soil mesofauna, mainly collembolans and mites, forming interactions during the fungal life-cycle, from grazing on hyphae to spore dispersal. However, it is still unknown if ERM of ectomycorrhizal fungi could influence the structure of mesofauna assemblages. Objective: To evaluate the abundance and community composition of the mesofauna inhabiting the ERM of Hebeloma mesophaeum, Laccaria laccata and Wilcoxina sp. in Pinus greggii roots. Methods: Mesofauna was collected from the root balls of P. greggii with 80 % of colonization using a washing method. Results and conclusions: An effect was observed due to ERM differences on species richness and species dominance, but not an effect on the abundance and community composition of the mesofauna. However, Wilcoxina sp. presented the lowest species richness and diversity. Fungus-feeding collembolans shaped species-rich assemblages, being isotomid-tullbergid forms the soil-dwelling taxa. Entomobryidae and Hypogastruridae were the most common families on the soil surface, not being found in Wilcoxina sp., and only a few predatory mites of the Mesostigmata and Endeostigmata were found. The ectomycorrhizal mycelium constitutes a trophic niche of the mesofauna and it might be an evolutionary force in structuring species composition and diversity.