Biology subjects

Arlettaz, R.

Publications and source records attributed to Arlettaz, R..

4 recordsLinked to original sources

bioRxiv2026

Dark diversity reveals assembly constraints across trophic levels in large-scale grassland restoration

1. Grassland biodiversity restoration efforts have largely focused on re-establishing diverse plant communities, with less attention paid to higher trophic levels such as invertebrates. 2. We established a controlled, field-scale restoration experiment across twelve lowland grassland sites in Switzerland in close collaboration with farmers. We manipulated seed addition (hay transfer, directly harvested seeds, or multiplied seed mixtures) and soil disturbance (shallow or deep tillage), with treatments applied to meadows covering, on average, 0.5 ha. Four to six years after restoration, we quantified the components of species richness change (lost, persisting, gained from site surroundings, and gained from donors), and estimated dark diversity (species that are absent from a location but could potentially occur there) for plants, Auchenorrhyncha and Orthoptera. 3. Compared to plants, invertebrates exhibited greater species turnover, with higher proportions of species lost and gained from the surroundings, but much lower contributions from the donor meadows. However, species persistence was high across taxa. Restoration operations strongly influenced components of species richness change in plants but had weaker effects on invertebrates. In particular, multiplied seed mixtures + deep tillage had the highest proportion of plant species not transferred, suggesting that many species in the seed mixture were poorly suited to local conditions. In both plants and Auchenorrhyncha, components of species richness change were strongly mediated by site characteristics, with initial species richness in both receiver and donor emerging as the strongest predictors. 4. Within each taxonomic group, 41% of species not transferred from the donor belonged to the dark diversity, suggesting substantial unrealized restoration potential. Restoration operations impacted dark diversity for plants and Auchenorrhyncha but not for Orthoptera. In plants, dark diversity was substantially lower under multiplied seed mixtures + deep tillage than under other treatments. The probability of a species belonging to dark diversity was associated with specific leaf area in plants and initial relative abundance in Auchenorrhyncha. 5. Synthesis and applications. Components of species richness change were influenced by both restoration operations and site characteristics, with their relative importance varying among taxa, underscoring the need for multi-taxon restoration strategies.

ecology↗

bioRxiv2026

Matching lynx population estimates to management scale: conservation science vs politics in the western Swiss Alps

Reliable population estimates are essential for wildlife management, yet monitoring schemes often do not match the administrative scale at which decisions are made. We illustrate this challenge using the Eurasian lynx in the canton of Valais, Switzerland, where official state monitoring is fragmented across three reference areas surveyed in different years. We analyzed three winters (2023-2026) of independent, canton-wide camera trap data, recording 899 independent lynx captures (27, 31 and 34 adults per winter). Lynx distribution and reproduction concentrated in the Northwest and connected to the thriving Pre-alpine populations. Density modelling for 2025/2026 estimated 37 independent lynx (95% CI: 26-52) on the whole cantonal territory, corresponding to a density of 1.09 (0.77-1.56) individuals per 100 km2. These estimates are substantially below the figures improperly extrapolated from a cross-cantonal reference area and conveyed by political authorities. Future lynx management decisions should be rooted in scientifically sound, scale-relevant information.

ecology↗

bioRxiv2020

Illegal hunting threatens the establishment of a lynx population and highlights the need of a centralized judiciary approach

O_LIIllegal hunting (poaching) represents a major threat to the conservation of large predators. Yet, its impact remains difficult to quantify as there are strong incentives to conceal this criminal activity. Attributing changes in the population status of large carnivores in part to poaching is therefore an important conservation challenge. C_LIO_LIWe present a case study of lynx (Lynx lynx) in southwestern Switzerland (canton of Valais) where the current distribution range is much smaller than it was in the recent past and population density is now >80% lower than in other lynx populations in the Swiss Alps, particularly in the adjacent Pre-Alps. We tested four hypotheses to explain this far lower density: 1) a too low density of trail camera-traps deployed for lynx surveys in Valais compared to the Pre-Alps (i.e. a methodological artefact); 2) less favourable environmental conditions around the camera-trap sites; 3) lower densities of the main prey; and 4) poaching. C_LIO_LIWe estimated lynx and ungulate densities and environmental conditions at trail camera sites, and were able to clearly reject the first three hypotheses: 1) the monitoring protocol was similarly effective; 2) environmental conditions around the trapping sites in Valais were even more favourable to lynx detection than in the Pre-Alps; and 3) prey supply was even larger. Concerning hypothesis 4, we discovered a local, but dense network of 17 illegal lynx traps in the narrow main immigration corridor into Valais from the thriving adjacent lynx population in the Pre-Alps, suggesting intense local poaching. C_LIO_LIOur findings substantiate the suspicions of long-lasting lynx poaching as a threat to the establishment and survival of the Valais population. The fact that instances of poaching were publicly known since 1995 but remained unabated for at least two decades, until a first conviction occurred, questions the commitment of local authorities to address this case of wildlife crime. Our study shows that inquiries about wildlife crime such as top predator poaching may need to be carried out at the highest levels of jurisdiction to avoid any risk of collusion between law enforcement agents and poachers. C_LI

ecology↗

bioRxiv2020

Grassland irrigation and fertilisation alter vegetation height and vegetation within temperature and negatively affect orthopteran populations

European mountain meadows are hosting an exceptionally rich biodiversity. While they have long been exposed to land abandonment, they are nowadays additionally threatened by agriculture intensification through aerial irrigation and slurry application. The consequences of this intensification on arthropods are not well documented and studies are needed to fulfil this knowledge gap. Six experimental management treatments combining a full factorial design and a gradual level of fertilisation and irrigation were implemented in 2010 in twelve different montane and subalpine Swiss meadows. In 2013, orthopterans were sampled to assess the influence of the management practices on their population. In addition changes in vegetation height and temperature induced by intensification were recorded in order to better appraise underlying mechanisms. Intensification had a negative impact on Caelifera (grasshoppers); with decreases of up to 70% in densities and 50% in species richness in the most intensively managed treatment plots. In parallel intensification induced an increase in mean vegetation height and a cooling of up to 4.2 {degrees}C (10 cm aboveground) within most intensively managed plots. These microhabitat and microclimate changes are likely to have affected Caelifera development, in particular thermophilous species. In contrast, Ensifera (bush crickets) densities and species richness did not respond to the management treatments. The use of irrigation (without fertilisation) had limited impacts on orthopterans and microclimate. In conclusion, orthopterans, in particular Caelifera, are relatively sensitive to grassland intensification and to conserve the full community, mountain agricultural systems need to maintain extensively managed meadows.

ecology↗