Biology subjects

Normand, S.

Publications and source records attributed to Normand, S..

3 recordsLinked to original sources

bioRxiv2023

Megafauna diversity and functional declines in Europe from the Last Interglacial (LIG) to the present

Aim: to estimate European megafauna diversity and functional declines in the present compared to the nearest in time modern-analogue climate period prior to the worldwide diffusion of Homo sapiens. Location: Europe. Time period: Last Interglacial (LIG; ca. 127,000 years ago) to present. Major taxa studied: wild, large ([≥]10 kg) terrestrial mammals. Methods: we assessed the distribution of 48 European megafauna species during the LIG using hindcasting modelling and fossil records. Then, we estimated the decline in megafauna community diversity and potential trait-based functional effects from the LIG to the present, accounting for climate differences between the two periods. Results: from the LIG to the present, species richness and community biomass across Europe dropped by 74.3% ({+/-} 9.9% SD) and 96.7% ({+/-} 4.1% SD), respectively. Functional diversity dropped by 59.1% ({+/-} 11.8% SD) for herbivores and by 48.2% ({+/-} 25.0% SD) for carnivores, while trait-informed potential vegetation and meat consumptions dropped by 91.1% ({+/-} 7.4% SD) and 61.2% ({+/-} 17.2% SD), respectively. The loss in megafauna diversity and associated ecological processes were high everywhere, but particularly in western Europe for carnivores and in the East European Plain for herbivores. We found that potential megafauna richness and functional patterns in the two periods were near identical if only climate-driven differences were considered. Main conclusions: severe, size-biased defaunation has degraded megafauna assemblages and megafauna-mediated ecological processes across Europe from the LIG to the present. These patterns cannot be explained by climate differences between the two periods, thus were likely driven by the impact of prehistoric Homo sapiens. The results suggest that the structure of wild ecosystems of the present strongly deviates from the evolutionary norm, notably with decreased functional heterogeneity and decreased fluxes of biogeochemical compounds across the trophic networks, highlighting the importance of ambitious policies of megafauna community restoration to support ecosystems functioning.

ecology↗

bioRxiv2019

Recent global changes have decoupled species richness from specialization patterns in North American birds

AimTheory suggests that increasing productivity and climate stability toward the tropics can explain the latitudinal richness gradient by favouring specialization. A positive relationship between species richness and specialization should thus emerge as a fundamental biogeographic pattern. However, land use and climate change disproportionally increase the local extirpation risk for specialists, potentially impacting this pattern. Here, we empirically quantify the richness-specialization prediction and test how 50 years of climate and land use change has affected the richness-specialization relationship.\n\nLocation\n\nUSA\n\nTime period\n\n1966-2015\n\nMajor taxa studied\n\nBirds\n\nMethodsWe used the North American breeding bird survey to quantify bird community richness and specialization to habitat and climate. We assess i) temporal change in the slope of the richness-specialization relationship, using a Generalized Mixed Model; ii) temporal change in spatial covariation of richness and specialization as driven by local environmental conditions, using Generalized Additive Models; and iii) land use, climate and topographic drivers of the spatio-temporal changes in the relationship, using a multivariate method.\n\nResultsWe found evidence for a positive richness-specialization relationship in bird communities. However, the slope of the relationship declined strongly over time. Richness spatially covaried with specialization following a unimodal pattern. The peak of the unimodal pattern shifted toward less specialized communities over time. These temporal changes were associated with precipitation change, decreasing temperature stability and land use.\n\nMain conclusionsRecent climate and land use changes induced two antagonist types of community responses. In human-dominated areas, the decoupling of richness and specialization drove a general biotic homogenization trend. In human-preserved areas under increasing climate harshness, specialization increased while richness decreased in a \"specialization\" trend. Our results offer new support for specialization as a key driver of macroecological diversity patterns, and show that global changes are erasing this fundamental macroecological pattern.\n\nBiosketchAnne Mimet is a postdoctoral researcher interested in the understanding of human impacts on biodiversity through land use and climate changes, at various spatio-temporal scales. She is interested in embracing the complexity of socio-ecological systems, and in the understanding of biodiversity trends in a human-dominated world in the context of the general theories of ecology.

ecology↗

bioRxiv2019

LIDAR explains diversity of plants, fungi, lichens and bryophytes across multiple habitats and large geographic extent

Effective planning and nature management require spatially accurate and comprehensive measures of the factors important for biodiversity. Light detection and ranging (LIDAR also known as light radar) can provide exactly this, and is hereby a promising technology to support future nature management and related applications. However, until now studies evaluating the potential of LIDAR for this field have been highly limited in scope. Here, we assess the potential of LIDAR to estimate the local diversity of four species groups in multiple habitat types, from open grasslands and meadows over shrubland to forests and across a large area (approximately 43.000 km2), providing a crucial step towards enabling the application of LIDAR in practice, planning and policy-making. We assessed the relationships between the species richness of macrofungi, lichens, bryophytes and plants, respectively, and 25 LIDAR-based measures related to potential abiotic and biotic diversity drivers. We used negative binomial Generalized Linear Modelling to construct 19 different relevant models for each species group, and leave-one-region-out cross validation to select the best models. These best models explained 49, 31, 32 and 28 % of the variation in species richness (R2) for macrofungi, lichens, bryophytes and plants respectively. Three LIDAR measures were important and positively related to the richness in three of the four species groups: variation in local heat load, terrain slope and shrub layer height. Four other LIDAR measures were ranked among the three most important for at least one of the species groups: point amplitude entropy, shrub layer density (1.5 - 5 m), medium-tree layer density (10 - 15 m) and variation in biomass. Generally, LIDAR measures exhibited strong associations to the biotic environment, and to some abiotic factors, but was not suitable for representing spatiotemporal continuity. In conclusion, we showed how well LIDAR alone can predict the local biodiversity across habitats. We also showed that several LIDAR measures are highly correlated to important biodiversity drivers, which are notoriously hard to measure in the field. This opens up hitherto unseen possibilities for using LIDAR for cost-effective monitoring and management of local biodiversity across species groups and habitat types even over large areas.

ecology↗