# Using DNA from digestive contents to highlight the dietary diversity of an invasive alien species feeding on soil macrofauna

Mathis Ventura, Shanèze Noël, Yoan Fourcade, Jean-Lou Justine, Thomas Lerch, Agnès Gigon, Lise Dupont, Virginie Roy

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## To cite this version:

Mathis Ventura, Shanèze Noël, Yoan Fourcade, Jean-Lou Justine, Thomas Lerch, et al.. Using DNA from digestive contents to highlight the dietary diversity of an invasive alien species feeding on soil macrofauna. Environmental and Agronomical Genomics Symposium, Feb 2024, Toulouse, France. hal-04955142

HAL Id: hal-04955142

https://hal.science/hal-04955142v1

Submitted on 18 Feb 2025

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Distributed under a Creative Commons Attribution 4.0 International License
# Using DNA from digestive contents to highlight the dietary diversity of an invasive alien species feeding on soil macrofauna

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**Mathis VENTURA<fnref n="1" />, Shanèze NOËL<fnref n="1" />, Yoan FOURCADE<fnref n="1" />, Jean-Lou JUSTINE<fnref n="2" />, Thomas LERCH<fnref n="1" />, Agnès GIGON<fnref n="1" />, Lise DUPONT<fnref n="1" />, Virginie ROY<fnref n="1" />**

## Introduction

Invasive terrestrial flatworms, through their **predatory behavior**, can be responsible for major **ecological disturbances** to consumed prey population and soil fauna community structure.

Due to the cryptic behavior of some predators, it is not always possible to observe predation directly. **Diet identification** can then be carried out through **metagenomic approaches**, using high-throughput sequencing of DNA from **digestive contents**.

Our study model is *Obama nungara*, a flatworm from South America, which has invaded more than 70 departments of metropolitan France, and is mostly found in anthropized environments [1]. Experimental data showed that it feeds on **earthworms**,enchytreids and terrestrial gastropods [2], but **field data are still missing**.

## Results

### First study:

* ✓ 20 earthworm species detected

* ✓ 1 to 5 species per sample

* ✓ Metabarcoding approach validated

### Ongoing study (Fig.2):

* ✓ 26 earthworm species detected

* ✓ 1 to 5 species per sample

* ✓ Most frequently detected ecotypes: anecic (1 species), epigeic (3 species) and endogeic (2 species)

<figure><img src="image_4.png" /><figcaption>Fig.1. *O. nungara* attacking an earthworm</figcaption></figure>

© Pierre Gros

<figure><img src="image_5.png" /><figcaption>Fig.2. Percentage of occurrence of each earthworm species detected in gut contents of 86 samples of *O. nungara*. « Ecotypes » of earthworms refer to the classification based on their physiological habits and functions in soil ecosystems. Three main ecotypes: endogeic, anecic and epigeic.</figcaption></figure>

## Aims & Methods

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© Pierre Gros

### Characterize the diversity of earthworms consumed by *O. nungara* and potential diet preferences

How did we obtain flatworms in **metropolitan France**?

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### First study

Citizen science program, **35 samples** from 20 sampling sites (10 French regions)

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### Ongoing study

Collecting twice a year for three years, **86 samples** from 10 sampling sites (4 French regions)

### Method

1. Extracting the gut contents of flatworms

2. Amplifying a 70bp earthworm-specific fragment of the 16S RNA gene

3. High-throughput sequencing of the amplicons (Illumina Mi-Seq, paired-end 2x150bp)

4. Identifying species consumed and potential predation bias between ecotypes

## Conclusions

The metabarcoding approach applied to gut contents was validated and revaled the **dietary diversity** of the terrestrial flatworm *O. nungara*.

We show that *O. nungara* predates on a **large spectrum** of potential prey. All ecotypes seem to be predated with various intensities (Fig.2), which implies **various potential effects on soil ecosystem functions**.

We provide here the **first field data** regarding predation by *O. nungara* on native soil fauna, suggesting its **potential threat** on soil ecosystem functioning.

### What's next?

Two more years of sampling will be analyzed, and results will be compared with prey diversity to account for its presence/abundance in situ!

### See our published article for the first study

Roy, V., Ventura, M., Fourcade, Y., Justine, J. L., Gigon, A., & Dupont, L. (2022). Gut content metabarcoding and citizen science reveal the earthworm prey of the exotic terrestrial flatworm, *Obama nungara*. *European Journal of Soil Biology*, **113**, 103449.

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<footnote n="1">¹ Université Paris-Est Créteil, Sorbonne Université, CNRS, INRAE, IRD, iEES Paris, 94010 Créteil Cedex, France</footnote>

<footnote n="2">² ISYEB, Muséum national d'Histoire naturelle, 75005 Paris, France</footnote>

<footnote n="1">1. Justine, J. L., Winsor, L., Gey, D., Gros, P., & Thévenot, J. (2020). *Obama* chez moi! The invasion of metropolitan France by the land planarian *Obama nungara* (Platyhelminthes, Geoplanidae). *PeerJ*, **8**, e8385.</footnote>

<footnote n="2">2. Boll, P. K., & Leal-Zanchet, A. M. (2016). Preference for different prey allows the coexistence of several land planarians in areas of the Atlantic Forest. *Zoology*, **119**(3), 162-168.</footnote>