High‐quality genomes reveal significant genetic divergence and cryptic speciation in the model organism Folsomia candida (Collembola)

The collembolan Folsomia candida Willem, 1902, is an important representative soil arthropod that is widely distributed throughout the world and has been frequently used as a test organism in soil ecology and ecotoxicology studies. However, it is questioned as an ideal “standard” because of differences in reproductive modes and cryptic genetic diversity between strains from various geographical origins. In this study, we present two high-quality chromosome-level genomes of F. candida, for the parthenogenetic Danish strain (FCDK, 219.08 Mb, N50 of 38.47 Mb, 25,139 protein-coding genes) and the sexual Shanghai strain (FCSH, 153.09 Mb, N50 of 25.75 Mb, 21,609 protein-coding genes). The seven chromosomes of FCDK are each 25–54% larger than the corresponding chromosomes of FCSH, showing obvious repetitive element expansions and large-scale inversions and translocations but no whole-genome duplication. The strain-specific genes, expanded gene families and genes in nonsyntenic chromosomal regions identified in FCDK are highly related to its broader environmental adaptation. In addition, the overall sequence identity of the two mitogenomes is only 78.2%, and FCDK has fewer strain-specific microRNAs than FCSH. In conclusion, FCDK and FCSH have accumulated independent genetic changes and evolved into distinct species since diverging 10 Mya. Our work shows that F. candida represents a good model of rapidly cryptic speciation. Moreover, it provides important genomic resources for studying the mechanisms of species differentiation, soil arthropod adaptation to soil ecosystems, and Wolbachia-induced parthenogenesis as well as the evolution of Collembola, a pivotal phylogenetic clade between Crustacea and Insecta.

Determining the Sustainability of Land-Applying Biosolids to Agricultural Lands Using Environmentally-Relevant Terrestrial Biota

Biosolids, the treated solid by-product of a WWPT, have been land-applied for decades as a means of disposal of an inexpensive form of fertilizer. However, research has shown that many chemicals such as pharmaceuticals, herbicides, pesticides, plasticizers, detergents, or heavy metals pass through the WWTP, often unaltered, and potentially end up in the biosolids. Therefore, a need to determine if the land-application of biosolids has an impact on terrestrial biota exists. In this work, six different organisms were used including Folsomia candida, Lumbricus terrestris, Zea mays, Glycine max, Phaseolus vulgaris, and Brassca rap. It was determined that government protocols were inadequate since they either prescribed organisms not environmentally-relevant or only looked at initial growth stages such as germination and emergence and not at effect, if any, on subsequent generations. Thus, new protocols were developed. Additionally, it was concluded that very little impact was seen on any of the terrestrial biota examined.

Determining the Sustainability of Land-Applying Biosolids to Agricultural Lands Using Environmentally-Relevant Terrestrial Biota

Biosolids, the treated solid by-product of a WWPT, have been land-applied for decades as a means of disposal of an inexpensive form of fertilizer. However, research has shown that many chemicals such as pharmaceuticals, herbicides, pesticides, plasticizers, detergents, or heavy metals pass through the WWTP, often unaltered, and potentially end up in the biosolids. Therefore, a need to determine if the land-application of biosolids has an impact on terrestrial biota exists. In this work, six different organisms were used including Folsomia candida, Lumbricus terrestris, Zea mays, Glycine max, Phaseolus vulgaris, and Brassca rap. It was determined that government protocols were inadequate since they either prescribed organisms not environmentally-relevant or only looked at initial growth stages such as germination and emergence and not at effect, if any, on subsequent generations. Thus, new protocols were developed. Additionally, it was concluded that very little impact was seen on any of the terrestrial biota examined.