Dataset Information

Pontoscolex corethrurus: A homeless invasive tropical earthworm?

ABSTRACT: The presence of earthworm species in crop fields is as old as agriculture itself. The earthworms Pontoscolex corethrurus (invasive) and Balanteodrilus pearsei (native) are associated with the emergence of agriculture and sedentism in the region Amazon and Maya, respectively. Both species have shifted their preference from their natural habitat to the cropland niche. They contrast in terms of intensification of agricultural land use (anthropic impact to the symbiotic soil microbiome). P. corethrurus inhabits conventional agroecosystems, while B. pearsei thrives in traditional agroecosystems, i.e., P. corethrurus has not yet been recorded in soils where B. pearsei dwells. The demographic behavior of these two earthworm species was assessed in the laboratory over 100 days, according to their origin (OE; P. corethrurus and B. pearsei) food quality (FQ; soil only, maize stubble, Mucuna pruriens), and soil moisture (SM; 25, 33, 42%). The results showed that OE, FQ, SM, and the OE x FQ interaction were highly significant for the survival, growth, and reproduction of earthworms. P. corethrurus showed a lower survival rate (> mortality). P. corethrurus survivors fed a diet of low-to-intermediate nutritional quality (soil and stubble maize, respectively) showed a greater capacity to grow and reproduce; however, it was surpassed by the native earthworm when fed a high-quality diet (M. pruriens). Besides, P. corethrurus displayed a low cocoon hatching (emergence of juveniles). These results suggest that the presence of the invasive species was associated with a negative interaction with the soil microbiota where the native species dwells, and with the absence of natural mutualistic bacteria (gut, nephridia, and cocoons). These results are consistent with the absence of P. corethrurus in milpa and pasture-type agricultural niches managed by peasants (agroecologists) to grow food regularly through biological soil management. Results reported here suggest that P. corethrurus is an invasive species that is neither wild nor domesticated, that is, its eco-evolutionary phylogeny needs to be derived based on its symbionts.

SUBMITTER: Ortiz-Ceballos AI

PROVIDER: S-EPMC6754163 | biostudies-literature | 2019

REPOSITORIES: biostudies-literature

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Pontoscolex corethrurus: A homeless invasive tropical earthworm?

Ortíz-Ceballos Angel I AI Ortiz-Gamino Diana D Andrade-Torres Antonio A Pérez-Rodríguez Paulino P López-Ortega Maurilio M

PloS one 20190920 9

The presence of earthworm species in crop fields is as old as agriculture itself. The earthworms Pontoscolex corethrurus (invasive) and Balanteodrilus pearsei (native) are associated with the emergence of agriculture and sedentism in the region Amazon and Maya, respectively. Both species have shifted their preference from their natural habitat to the cropland niche. They contrast in terms of intensification of agricultural land use (anthropic impact to the symbiotic soil microbiome). P. corethru ...[more]

PMID: 31539381

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Project description:Nest construction is a common form of parental care in soil organisms. However, it is unknown whether the tropical earthworm Pontoscolex corethrurus produces nests in soils with low nutritional quality habitats. Here we studied the reproductive behaviour and nest site selection of P. corethrurus, and tested the hypothesis whether P. corethrurus produces more cocoons in habitats with low nutritional quality. In bidimensional terrariums we evaluated the combined effect of the nutritional quality of habitat: (Poor Quality Habitat = PQH, Medium Quality Habitat = MQH, High Quality Habitat = HQH) and soil depth (Shallow, Intermediate, Deep) in a factorial 3(2) design. The number and biomass of cocoons, progeny and the production of internal and external excreta were evaluated. The quality habitat and depth of soil and their interaction had a significant effect on nest site construction and the deposition of internal excreta. Pontoscolex corethrurus built a higher amount of nests in the PQH-Intermediate and MQH-Intermediate treatments while more internal excreta were found in the HQH-Intermediate treatment. Offspring biomass was positively associated with internal excreta in the PQH (soil only) and MQH (soil + grass) treatments, suggesting that this could be a form of parental care. Since P. corethrurus produces more cocoons in low and medium quality habitats, while produces more internal excreta at high quality habitats, there does not seem to be an association between number of offspring and parental care. We suggest P. corethrurus could have two reproductive strategies that act as diversified bet-hedging (do not put all cocoons in one basket) behavior in unpredictable environment, and thus build a higher amount of nests in low and medium quality habitats; and another where they produce more internal excreta as a form of parental care in high quality habitats. Parental care in the form of internal excreta may be particularly important in poor and medium quality habitats where offspring biomass increased with internal excreta. Further research is needed on the ecological conditions that favour the evolution of parental care in earthworms according to their ecological category (epigeic, endogeic and anecic).

Project description:Recent studies have shown that invasive earthworms can dramatically reduce native biodiversity, both above and below the ground. However, we still lack a synthetic understanding of the underlying mechanisms behind these changes, such as whether earthworm effects on soil chemical properties drive such relationships. Here, we investigated the effects of invasive earthworms on soil chemical properties (pH, water content, and the stocks and fluxes of carbon, nitrogen, and phosphorus) by conducting a meta-analysis. Invasive earthworms generally increased soil pH, indicating that the removal of organic layers and the upward transport of more base-rich mineral soil caused a shift in soil pH. Moreover, earthworms significantly decreased soil water content, suggesting that the burrowing activities of earthworms may have increased water infiltration of and/or increased evapotranspiration from soil. Notably, invasive earthworms had opposing effects on organic and mineral soil for carbon and nitrogen stocks, with decreases in organic, and increases in mineral soil. Nitrogen fluxes were higher in mineral soil, whereas fluxes in organic soil were not significantly affected by the presence of invasive earthworms, indicating that earthworms mobilize and redistribute nutrients among soil layers and increase overall nitrogen loss from the soil. Invasive earthworm effects on element stocks increased with ecological group richness only in organic soil. Earthworms further decreased ammonium stocks with negligible effects on nitrate stocks in organic soil, whereas they increased nitrate stocks but not ammonium stocks in mineral soil. Notably, all of these results were consistent across forest and grassland ecosystems underlining the generality of our findings. However, we found some significant differences between studies that were conducted in the field (observational and experimental settings) and in the lab, such as that the effects on soil pH decreased from field to lab settings, calling for a careful interpretation of lab findings. Our meta-analysis provides strong empirical evidence that earthworm invasion may lead to substantial changes in soil chemical properties and element cycling in soil. Furthermore, our results can help explain the dramatic effects of invasive earthworms on native biodiversity, for example, shifts towards the dominance of grass species over herbaceous ones, as shown by recent meta-analyses.

Dataset Information

Pontoscolex corethrurus: A homeless invasive tropical earthworm?

Publications

Pontoscolex corethrurus: A homeless invasive tropical earthworm?

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