Ocnerodrilidae, Demetrio & Fonseca & Dudas & Zagatto & Feijoo & Brown, 2023

Demetrio, Wilian Carlo, Fonseca, Priscila Mouro Da, Dudas, Rafaela, Zagatto, Mauricio G. R., Feijoo, Alexander & Brown, George Gardner, 2023, Earthworm species in native and planted forests in Brazil, Zootaxa 5255 (1), pp. 304-323 : 318-320

Ocnerodrilidae sp.

BRSP0445 , 2 juveniles in Araucaria angustifolia plantation, hand sorting, topsoil (0-20 cm), Cap„o Bonito National Forest, Cap„o Bonito-SP (-23.88169, -48.50773); March, 2012; P. Fonseca, M. Zagatto, colls .

A total of 1209 earthworms were collected: 158, 111, 201 and 739 individuals (ind.) in Três Barras, Irati, Pirarí do Sul and Cap„o Bonito National forests, respectively. Overall, nine genera and 13 species (four of them new, as of yet undescribed), belonging to five families ( Rhinodrilidae , Glossoscolecidae , Ocnerodrilidae , Benhamiidae and Megascolecidae ) were identified ( Table 2 , 3). Eight are native species, including Andiorrhinus duseni (Michaelsen) , a “ minhocuçu ”, i.e., a large earthworm species with> 25 cm length, Urobenus brasiliensis (Benham) , Ocnerodrilidae sp., Fimoscolex n.sp., Glossoscolex araucariaensis Feijoo & Brown , Glossoscolex n.sp. 1, Glossoscolex n.sp. 2 and Glossoscolex n.sp. 3. The other five species are exotic and/or cosmopolitan anthropochore (widespread and transported by humans) species: Amynthas corticis (Kinberg) , Amynthas gracilis (Kinberg) , Metaphire californica (Kinberg) , Dichogaster saliens (Beddard) and Pontoscolex corethrurus (M̧ller).

Although most of species collected are native, exotic earthworms represented 88% (1076 ind.) of the individuals sampled. The two most common families found were Megascolecidae representing 39% of the exotic earthworms collected, and Rhinodrilidae with 55% (being 86% P. corethrurus ) of all individuals sampled. Both families occurred in all sites evaluated ( Table 2 ). Megascolecidae comprises several genera of Asian earthworms, and the two most frequent species sampled from this family were A. corticis and A. gracilis , commonly known in Brazil as “jumping worms”, both of which are widespread in Brazil ( Brown & James 2007). Both species had already been documented in Brazilian Atlantic Forests, including Araucaria forests and Pinus spp. plantations ( Baretta et al. 2007; Bartz et al. 2013, 2014b; Demetrio et al. 2018; Ferreira et al. 2018; Krabbe et al. 1993; Ortiz 2016; Pereira 2012; da Silva et al. 2019; Brown & Gabriac, 2021; Demetrio et al. 2022). The presence of Megascolecidae earthworms in all sites indicate that even native forests sampled here are not pristine environments, since these species are usually found living in human-disturbed environments inhabiting the surface soil layer and feeding on organic matter ( Steffen et al. 2018).

The species P. corethrurus represented most of the individuals sampled (about 48%), but it was found only in Araucaria plantations at Irati and at all sites sampled in Cap„o Bonito, where they dominated the earthworm fauna ( Table 2 , 3). This earthworm can be found in basically all tropical regions, also associated with anthropic disturbance ( Taheri et al. 2018). In Brazil, P. corethrurus was already sampled in almost all Brazilian States ( Brown & James 2007).

The highest local species richness, considering both sampling methods, was observed in Irati which had eight species ( Glossoscolex n.sp. 1, Glossoscolex n.sp. 2, A. corticis , A. gracilis , M. californica , A. duseni , U. brasiliensis , P. corethrurus ), followed by Cap„o Bonito with six species ( D. saliens , Glossoscolex n.sp. 3, A. corticis , A. gracilis , Ocnerodrilidae sp., P. corethrurus ), Três Barras with five species ( G. araucariaensis , Glossoscolex sp. , A. corticis , A. gracilis , U. brasiliensis ) and Piraí do Sul with four species ( A. corticis , A. gracilis , A. duseni , U. brasiliensis ). Considering the vegetation type, in general, native forests and Araucaria plantations had higher species richness compared to pine plantations, except in Piraí do Sul where both plantations had two species. Similar to slightly higher species richness in native forest plots (6 sp. overall) and tree plantations (6 to 7 spp.) had been observed previously by Da Silva et al. (2019) at Embrapa Forestry in Colombo, state of Paraná, where exotic species also dominated in the pine plots. However, although a considerable number Atlantic Forest fragments have been sampled in Brazil ( Demetrio et al. 2022), relatively few of them have had sufficient sampling effort to adequately assess species richness ( Brown & James 2007).

Although the number of exotic and native species were quite similar between the vegetation types (except for Cap„o Bonito, dominated by P. corethrurus ), we observed low species evenness and high dominance of exotic earthworms is almost all sites evaluated. The relative abundance of exotic earthworms ranged from 33 to 100% using hand sorting in Três Barras and Cap„o Bonito pine plantations, and in formalin from 50% to 100% in Irati pine plantations and all Cap„o Bonito sites. Low dominance of exotic earthworms (<50% of individuals collected, hand sorting) was observed in Araucaria (42%) and pine plantations (33%, but only three earthworms were found under Pinus ) at Três Barras, and pine plantations at Irati (41%) and Piraí do Sul (33%, only 6 earthworms collected).

In general, formalin expulsion collected a lower number of earthworms than hand sorting, as observed previously by Da Silva et al. (2019). The efficiency of formalin compared to hand sorting ranged from 0% (no earthworms sampled) in pine plantations up to 82% in the native forest at Três Barras. Only at two sites (native forests at Irati and Piraí do Sul) did formalin expulsion collect more earthworms than hand sorting (192% and 147%, respectively); however, in both cases formalin basically collected only half of the local earthworm species present ( Tables 2 and 3). The differences observed in the sampling methods were expected. In tropical regions the use of hand sorting is recommended combined with chemical extraction, aiming to sample large earthworms (R̂mbke et al. 2006). But, the efficiency of formalin on earthworm sampling depends on several factors, such as soil moisture during sampling and also the local earthworm assemblage ( Pelosi et al. 2009). Gutiérrez-López et al. (2016) also showed that chemical extraction is less efficient at sampling endogeic earthworms due their low mobility and lack of burrows connected with the soil surface. In our study, 70% of the earthworms collected using formalin were epiendogeic species ( Amynthas species and U. brasiliensis ), which live in the soil-litter interface, confirming previous results of Da Silva et al. (2019).

Both extraction methods collected more juveniles than adult animals (data not shown), however, some species were found using only a specific method, and/or occurred in a single location, while others did not show any preference: A. corticis dominated at almost all sites evaluated, except Cap„o Bonito where P. corethrurus was more abundant. In general, hand sorting recovered a higher number of species compared to formalin, and several species were only found using this method at particular site, such as A. duseni in Três Barras, Irati and Piraí do Sul; G. araucariaensis and Glossoscolex sp. in Três Barras; Glossoscolex n.sp. 1, Glossoscolex n.sp. 2, Glossoscolex n.sp. 3 and P. corethrurus in Irati; Fimoscolex n.sp., D. saliens and Ocnerodrilidae sp. in Cap„o Bonito. M. californica was found in native forest and pine plantations in Irati, and was collected only using formalin. This species is known from some South American countries ( Argentina, Peru, Venezuela), and in Brazil previous studies found this species in the states of Santa Catarina, Paraná, S„o Paulo, Rio de Janeiro, Minas Gerais and Bahia ( De Assis et al. 2017).

All earthworm species observed in this study (except the new ones) had already been documented from the Atlantic Forest region, especially in Araucaria forests. Recently, Brown & Gabriac (2021) compiled the data regarding earthworm diversity in Araucaria forests (native and plantations) from which they reported 39 species (30 native and 9 exotic).Although the four National Forest sites studied here hosted a good number of earthworm species, the high occurrence of exotic individuals indicates a relatively high level of anthropic disturbance in all vegetation types sampled, including the native forest. The consequences of exotic earthworm invasion in Atlantic forest sites are still unknown, but similar effects as those found in North American forests may occur in this biome ( Chang et al. 2021; Ferlian et al. 2018), particularly where the native earthworms have already disappeared ( Demetrio et al. 2022). Nonetheless, where native earthworms are still present, competition may be an important phenomenon also limiting native earthworm species, as can be predicted from these empirical observations on the high abundance of exotic vs. native earthworm species at the national forests studied.