Biology subjects

Humann-Guilleminot, S.

Publications and source records attributed to Humann-Guilleminot, S..

2 recordsLinked to original sources

bioRxiv2025

Field-based evidence of sperm quality impairment associated with conventional farming in two passerine birds.

The detrimental effects of conventional farming on bird biodiversity are increasingly documented. Despite this, the specific impacts of both organic and conventional farming practices on bird coloration and sperm quality in natural settings remain unexplored. This study aimed to determine whether these farming practices differentially affect body mass, coloration intensity, and sperm quality in passerine birds inhabiting agricultural landscapes. We captured seven passerine species in hedgerows adjacent to fields farmed organically or conventionally, within a 250-meter radius representative of their breeding home ranges. Body mass was measured across all species, and an index of coloration intensity, based on carotenoid (yellow/orange) and melanin (black) pigments, was assessed in four species. Additionally, we evaluated three sperm quality parameters (sperm density, percentage of abnormal sperm, and intra-individual variance of sperm morphology) using fresh sperm samples collected from four species in the field. We hypothesized that birds living near conventional fields would exhibit lower body mass due to reduced food availability. Additionally, we predicted that the more favourable conditions associated with organic farming, such as greater food abundance and lower exposure to pollutants, would benefit birds, leading to enhanced coloration and improved sperm quality. Our results did not reveal any difference in body mass or coloration. The absence of observable effects might be due to several factors: methodological limitations, cross-contamination between habitats or insufficient exposure to farming practices that may hide any potential difference between the two habitats, or the intrinsic adaptive strategies of the species. However, subgroup analysis of three and four species revealed a decrease in sperm density and a higher proportion of abnormal spermatozoa in the Common Whitethroat and Common Nightingale living in conventional farming, respectively. Although our sample size was limited, we believe these findings highlight the potential negative effects of conventional farming on birds.

ecology↗

bioRxiv2025

Off target: herbicides applied in cereal fields exclude non-competitive species, while replacing them by competitive weeds.

Weed diversity plays an important role in maintaining resilient agroecosystems, yet agricultural practices, such as pesticide applications, significantly shape weed communities. Previous studies have primarily focused on comparing organic and conventional farming, with a particular emphasis on land-use intensification, with less attention on the impact of pesticides. Our study examined the impact of herbicide, fungicide, and insecticide use - both in terms of Treatment Frequency Index (TFI), i.e. intensity of application, and quantity - on weed communities in 96 non-organic cereal fields over 4 years. Interestingly, our results indicate that fungicide application intensity decreased weed abundance by 11.6% and species richness by 14.6% for each one-standard-deviation (1-SD) increase in TFI, whereas the total quantity applied (QA) did not. In contrast, for herbicides, QA had a stronger negative impact on weed communities than TFI, with a 14.3% decrease in weed abundance and a 12.4% decrease in species richness for each 1-SD increase in QA. This suggests that TFI of fungicide, which may reflect low-dose but frequent applications, could exert indirect and long-term effects on weed suppression, potentially by altering symbiotic arbuscular mycorrhizal fungi in the soil. In comparison, QA of herbicide more directly reflects the toxic load delivered to weeds and is therefore a better predictor of their suppression. Based on a combination of multivariate and univariate analyses and the study of underlying mechanisms in community changes, our results reveal that herbicides are the main factor shaping weed communities by decreasing the abundance of non-target/non-competitive species while replacing them by problematic, competitive to crops, weed species. These findings point out the potential ineffectiveness of herbicides application on problematic weeds and emphasize the need to reconsider the use of herbicides to maintain weed diversity in agricultural landscapes.

ecology↗