Biology subjects

Gerard, S.

Publications and source records attributed to Gerard, S..

3 recordsLinked to original sources

bioRxiv2026

Systematic evidence map of research on life-history traits in native and introduced earthworms

Invasive species constitute one of the most significant threats to biodiversity worldwide, and are responsible for more than $400 billion in losses each year. An organism's life-history strategy, defined by how it allocates resources among growth, survival, and reproduction, plays a central role in determining whether it becomes invasive. While the life-history profiles of aboveground invaders are increasingly well characterised, those of invasive species below ground remain poorly understood. Earthworms are a diverse group of soil invertebrates that can help fill this knowledge gap. Of the ~5,800 earthworm species described to date, nearly 2% are cosmopolitan, meaning they have achieved wide geographic distributions despite limited ability for active dispersal. While life-history traits are likely to contribute to their worldwide distribution, the existing research on earthworm trait variation has not been systematically reviewed. To address this gap, we assessed the taxonomic scope, geographic coverage, and methodologies of studies on earthworm life history traits for species occurring in the US and Brazil, spanning a broad latitudinal range. Our literature search yielded over 8,000 articles across 180 species and revealed that introduced species have received considerably more research attention than native species. Research was concentrated on a few model species, most studies were experimental, and variation in life history traits was most commonly assessed in response to chemical compounds, vermicompost feed type, and environmental factors such as temperature, moisture and soil composition. Variation in adult survival was reported most frequently, followed by adult growth and cocoon production, with the bulk of life history research conducted in India (20%) and China (9%). To better understand the effect invasive earthworm species might have on native fauna, future research on life histories should address taxonomic biases and prioritise detailed study of the life cycles of native species in their natural habitat.

ecology↗

bioRxiv2026

Resurvey of boreal earthworm communities in southern and northern Finland

In northern boreal Europe, the Last Glaciation Maximum resulted in a tabula rasa of earthworm species, post-glacial recolonisation of few peregrine species. Boreal forests represent 11.5% of the Earth's land area, and their cold winters represent the harshest season for earthworms. These biotopes are subject to substantial global changes, notably climate change and land use intensification, which might impact earthworm populations. Yet, no study measuring temporal changes in earthworm population or diversity is known in this biotope. Here, we sampled earthworm communities in two northern and two southern areas in Finland forests. In total, 21 sites were surveyed in 2015 and resurveyed 10 years later in 2025-2026. We aimed at understanding how earthworm diversity and populations changed in the last 10 years, comparing community and species-specific diversity metrics. In ten years, although not significant, earthworm abundance declined (-20%), whereas richness increased (+13%). The cold-tolerant Dendrobaena octaedra decreased, being the only one with a significant change. Temporal community and species dynamics followed a south-north gradient. Southern sites showed a decrease in abundance and D. octaedra populations, with an increase in abundance and occupancy of more heat-tolerant species. Northern sites showed an increase in abundance uniquely due to an increase in D. octaedra populations, but no other species were found there. These changes can be linked to climate changes leading to less rigorous winters in both south and north of Finland, and more rigorous summers in the south, potentially interacting with intense forest management, but could also be attributed to a still ongoing post-glacial recolonisation. These results call for more long-term sampling of earthworm communities in these fragile and rapidly changing environments.

ecology↗

bioRxiv2024

A can of worms: estimating the global number of earthworm species

Estimating the overall species number for a given taxon is a central issue in ecology and conservation biology. This is especially topical for soil organisms, which comprise most known species but whose taxonomy remains largely understudied. Here, we estimated the global number of earthworm species based on the Joppa approach, which models taxonomic effort over time to estimate the total number of known and as yet unknown species in a given taxa. Our Bayesian estimation of the Joppa model suggests a global diversity of the order of 30,000 species, suggesting that the 5,679 earthworm taxa already described only represent around 20% of the actual global species diversity. However, the uncertainty around this estimate is considerable due to severe undersampling and as the model cannot unambiguously decide whether we are describing few species because of a small pool of as yet unknown species, or because of a lack of taxonomic efficiency. Considering the current rate of new species description, we calculate that it would take at least 120 years to describe all the earthworm species existing on Earth, and we discuss thedifferent strategies that should be developed to facilitate and accelerate the discovery and naming of species new to science.

ecology↗