The second wave of earthworm invasions in North America: biology, environmental impacts, management and control of invasive jumping worms

Earthworms in grass lawns and native Atlantic Forest fragments at Embrapa Forestry, Colombo, Paraná state, Brazil

Earthworms are important soil biological indicators, but there is relatively little information on their communities in peri-urban soils and land uses in the subtropics. In the present paper, we describe earthworm occurrence and relationships with soil biological, chemical and physical attributes in grass lawns and native Atlantic Forest fragments in the Curitiba metropolitan area, using different sampling methods: quantitative handsorting, formalin extraction and qualitative sampling. Overall, 785 individuals, of six families and 12 species were found, four of which were native (Glossoscolex embrapaensis, Fimoscolex nivae, Urobenus brasiliensis and Ocnerodrilidae sp.), and eight exotic (Dichogaster bolaui, Dichogaster sp., Murchieona minuscula, Aporrectodea rosea, Amynthas gracilis, Amynthas morrisi, Metaphire californica and Pontoscolex corethrurus). Grass lawns had higher abundance (509 individuals) and diversity (Shannon-Wienner, Simpson and Pielou). Handsorting was the most effective sampling method (70% of all individuals). Exotic species predominanted in most areas (≥50% of individuals), indicating a higher degree of human disturbance. Biomass followed the same pattern as abundance, being higher in grass lawns. Multivariate analysis showed that chemical and biological soil attributes did not have a direct correlation with earthworm abundance, and that native forest fragments had higher acidity and C contents.

The unseen diversity of the semi-aquatic earthworms of the genus Sparganophilus (Oligochaeta: Sparganophilidae) from the Southeastern Appalachian Piedmont

After one year of surveying semiaquatic earthworms (Oligochaeta, Sparganophilidae), we describe Sparganophilus jenkinsi sp. nov., S. carveri sp. nov., S. oconeeae sp. nov., S. williamsae sp. nov., S. muskogee sp. nov., S. youngae sp. nov., and S. borgesae sp. nov. based on extensive differences in morphological characters and molecular data. Three additional species are described morphologically but not formally named due to limited material. The species of Sparganophilus described here can be organized into three species groups: (1) S. jenkinsi, S. oconeeae, S. muskogee, S. carveri, S. williamsae, S. youngae, S. borgesae, and Sparganophilus sp02 have continuous tubercula pubertatis in the region of xvii-xxii, and tubular nephridial bladder; (2) Sparganophilus sp09 have three discrete pairs of tubercula pubertatis and sack-like nephridial bladder; and (3) Sparganophilus sp10 have the tubercula pubertatis posteriorly displaced and reduced to two segments, and have a nephridial "caecum." These new species contribute to our knowledge of the endemism and biodiversity of earthworms in the Appalachian Piedmont.

Chaetophilosciasicula Verhoeff, 1908 (Isopoda, Oniscidea), an invasive isopod currently spreading in North America

Chaetophilosciasicula Verhoeff, 1908 (Philosciidae) is a small terrestrial isopod of Mediterranean origin which was first reported in North America in 2000 in an urban forest in Baltimore, Maryland, and it was thought to be a recent introduction, with a restricted range. Here we report the current state of knowledge of C.sicula distribution in North America. Since the original observation, the species has been reported by citizen scientists from eight additional states. Standardized field surveys in Maryland and Washington D.C. revealed a strong habitat preference towards anthropogenic and coastal areas. The affinity of C.sicula to urban environments, including residential areas and urban parks, is reinforced by citizen-science data and is most likely key to its fast spread throughout North America. Keeping isopods as pets and trading them among hobbyists may also play a role especially in establishing core populations in urban centers. The species is likely to expand in the USA in the coming decade. This study highlights that thorough, systematic surveys, using a variety of collecting techniques, are essential to address existing knowledge gaps on terrestrial isopod distribution and spread in North America and elsewhere.

When plastisphere and drilosphere meet: Earthworms facilitate microbiome and nutrient turnover to accelerate biodegradation of agricultural plastic films

Agricultural plastic mulching films have been an environmental concern for decades. The effects of the interactions between the anthropogenic plastisphere and other soil biospheres, particularly that of earthworms, on the fate of plastics remain poorly understood. Here, we investigated the decomposition of buried nonbiodegradable low-density polyethylene (LDPE) versus biodegradable PBTA/PLA copolymers in the presence of earthworms (Amynthas cortices) in dynamic microcosms. Earthworms significantly enhanced the biodegradation of plastic films in situ, as confirmed by mass reduction, surface modification, and changes in the molecular weights of films. Notably, the PBTA/PLA films exhibited a 1.41-fold increase in mass loss and a 5.69% reduction in the number-average molecular weight when incubated with earthworms. Earthworms influenced the microbial assembly within the plastisphere by increasing both bacterial and fungal biodiversity, as well as their network complexity. The time-decay patterns in the abundance of keystone degrader taxa, including the genera Noviherbaspirillum, Rhizobacter, and Mortierella, were mitigated by earthworms over the 60-day period. Additionally, earthworms preferentially consumed recalcitrant dissolved organic matter in LDPE and PBAT/PLA plastisphere soils, thereby increasing the bioavailability of components that serve as nutrient supplies for plastisphere microbiomes. Our findings demonstrate that earthworms enhance the decomposition of plastics in soils via cross-species interplay within the plastisphere and drilosphere, contributing not only to soil conditioning and biodiversity but also to plastic biodegradation in natural agroecosystems.

A review of the earthworm Amynthasmasatakae (Beddard, 1892) (Clitellata, Megascolecidae), with designation of two new synonyms

Correct and timely identification of an invasive species during quarantine or at an early stage of invasion before establishment or spread is critical for preventing biological invasions. However, taxonomic confusion of potential invasive earthworm species caused by incorrect taxonomic treatment or reckless taxonomic work has made it difficult to properly recognize potential invasion threats. Through analyzing publicly available DNA sequences of the mitochondrial cytochrome c oxidase subunit I (COI) gene, we confirmed the validity of the specific status of Amynthasmasatakae (Beddard, 1892), a peregrine earthworm species in East Asia with the potential to spread to other regions of the world, and designated two new synonyms of A.masatakae: Amynthastralfamadore Blakemore, 2012 syn. nov. and Amynthasscaberulus Sun and Jiang, 2021 syn. nov. Additionally, the name A.triastriatususualis Dong, Jiang, Yuan, Zhao and Qiu, 2020 is nomenclaturally unavailable since it was published in an electronic journal without ZooBank registration and an explicit statement establishing a new nominal taxon. Specimens described under this unavailable name actually belong to A.masatakae. Inadequate literature review and erroneous species identities associated with sequences in GenBank have caused even more problems in the already confusing earthworm taxonomy.

New records of earthworms (Clitellata: Oligochaeta) from Georgia, USA, including eight new state records

We present here new county records for 13 counties within Georgia, USA from the collections of the Georgia Museum of Natural History and the authors. These include four families, eight genera, and 23 species. Of these, eight species are new state records: Amynthas carnosus (Goto & Hatai, 1899); Aporrectodea longa (Ude, 1885); Bimastos parvus (Eisen, 1874); Diplocardia deborahae Damoff & Reynolds, 2017; Diplocardia gatesi Murchie, 1965; Diplocardia michaelseni Eisen, 1899; Metaphire hilgendorfi (Michaelsen, 1892); and Murchieona minuscula (Rosa, 1906). These findings are presented alongside an updated checklist for Middle Georgia building on data compiled by Reynolds (2015) to create a practical record for the region.

Land use change and forest management effects on soil carbon stocks in the Northeast U.S

BACKGROUND

In most regions and ecosystems, soils are the largest terrestrial carbon pool. Their potential vulnerability to climate and land use change, management, and other drivers, along with soils' ability to mitigate climate change through carbon sequestration, makes them important to carbon balance and management. To date, most studies of soil carbon management have been based at either large or site-specific scales, resulting in either broad generalizations or narrow conclusions, respectively. Advancing the science and practice of soil carbon management requires scientific progress at intermediate scales. Here, we conducted the fifth in a series of ecoregional assessments of the effects of land use change and forest management on soil carbon stocks, this time addressing the Northeast U.S. We used synthesis approaches including (1) meta-analysis of published literature, (2) soil survey and (3) national forest inventory databases to examine overall effects and underlying drivers of deforestation, reforestation, and forest harvesting on soil carbon stocks. The three complementary data sources allowed us to quantify direction, magnitude, and uncertainty in trends.

RESULTS

Our meta-analysis findings revealed regionally consistent declines in soil carbon stocks due to deforestation, whether for agriculture or urban development. Conversely, reforestation led to significant increases in soil C stocks, with variation based on specific geographic factors. Forest harvesting showed no significant effect on soil carbon stocks, regardless of place-based or practice-specific factors. Observational soil survey and national forest inventory data generally supported meta-analytic harvest trends, and provided broader context by revealing the factors that act as baseline controls on soil carbon stocks in this ecoregion of carbon-dense soils. These factors include a range of soil physical, parent material, and topographic controls, with land use and climate factors also playing a role.

CONCLUSIONS

Forest harvesting has limited potential to alter forest soil C stocks in either direction, in contrast to the significant changes driven by land use shifts. These findings underscore the importance of understanding soil C changes at intermediate scales, and the need for an all-lands approach to managing soil carbon for climate change mitigation in the Northeast U.S.

Genetic population structure and reproductive system of two invasive Asian earthworms, Amynthas tokioensis and Amynthas agrestis

The invasive Asian earthworms, Amynthas tokioensis and A. agrestis, have been successful in entering North American forests in recent decades, with significant damage to both soils and above-ground environments. This success could be driven in part by a polyploid genetic system and parthenogenetic reproduction, often suggested as benefits for invasive species. Therefore, we assessed the genetic population structure, genetic diversity, and reproductive system of both species using morphological traits and panels of microsatellite markers. A total of 216 A. tokioensis and 196 A. agrestis from six sites in Vermont USA were analyzed. Although all worms were morphologically hermaphroditic, all the A. agrestis lacked the male pore (the structure allowing pass of sperm between individuals), and only 19% of the A. tokioensis possessed the male pore. All A. tokioensis earthworms were triploid (scored for three alleles for at least 1 locus, and usually several), and A. agrestis was a mix of triploid and diploid individuals. Notable was the high proportion (80%) of A. agrestis earthworms that were diploid at one site. There was clearly clonal reproduction, with identical seven- locus genotypes observed for earthworms from each site, with as many as 45 individuals with the identical genotype at one site. However, the earthworms were also genetically diverse, with 14 genotypes observed for A. tokioensis and 54 for A. agrestis, and with many singleton genotypes (a single individual). Most genotypes (71% for A. tokioensis and 92% for A. agrestis) were found at a single site. The greatest number of genotypes was found at a commercial nursery where fully 23/26 A. agrestis earthworms were singleton genotypes. As expected for the pattern of private clone alleles at sites, several measures of geographic genetic differentiation were positive, and as expected for triploid systems, an AMOVA analysis showed high within-individual genetic diversity. The paradox of clear clonal reproduction, but with a great number of genotypes for each species, and the mix of triploid and diploid individuals could be explained if the worms have been sexually reproductive, with the switch to the uniparental system only recently (or even if sexual reproduction is episodic). Last, a large number of microsatellite loci were recovered for each species and there sequence and suggested PCR primers are provided for free use by other researchers.

Aboveground impacts of a belowground invader: how invasive earthworms alter aboveground arthropod communities in a northern North American forest

Declining arthropod communities have recently gained a lot of attention, with climate and land-use change among the most frequently discussed drivers. Here, we focus on a seemingly underrepresented driver of arthropod community decline: biological invasions. For approximately 12 000 years, earthworms have been absent from wide parts of northern North America, but they have been re-introduced with dramatic consequences. Most studies investigating earthworm-invasion impacts focus on the belowground world, resulting in limited knowledge on aboveground-community changes. We present observational data on earthworm, plant and aboveground arthropod communities in 60 plots, distributed across areas with increasing invasion status (low, medium and high) in a Canadian forest. We analysed how earthworm-invasion status and biomass impact aboveground arthropod community abundance, biomass and species richness, and how earthworm impacts cascade across trophic levels. We sampled approximately 13 000 arthropods, dominated by Hemiptera, Diptera, Araneae, Thysanoptera and Hymenoptera. Total arthropod abundance, biomass and species richness declined significantly from areas of low to those with high invasion status, with reductions of 61, 27 and 18%, respectively. Structural equation models suggest that earthworms directly and indirectly impact arthropods across trophic levels. We show that earthworm invasion can alter aboveground multi-trophic arthropod communities and suggest that belowground invasions might be underappreciated drivers of aboveground arthropod decline.