Jan Perret

Centre d'Ecologie Fonctionnelle et Evolutive, French National Centre for Scientific Research | CEFE · Biodiversity & Conservation

Population monitoring programmes typically rely on sampling because it is impossible to survey all the sites within the study area. In such a situation, the general recommendation to obtain unbiased estimates of population trends is to select monitoring sites using probability sampling. However, site selection not based on probability sampling, suc...

Three decades ago, worldwide biodiversity hotspots were founded on the distributions of continental plants and vertebrates. Here, we question the timeliness of refining the geography of hotspots by basing their definition on more taxa, thanks to the molecular data available for hyper-diverse organisms such as insects, fungi and marine biota. To do...

The estimation of population size and its variation across space and time largely relies on counts of individuals, generally carried out within spatial units such as quadrats or sites. Missing individuals during counting (i.e. imperfect detection) results in biased estimates of population size and trends. Imperfect detection has been shown to be th...

Les suivis de population jouent un rôle central dans la conservation de la biodiversité. Ils permettent d’estimer les tailles et les tendances des populations, deux informations cruciales pour identifier les populations menacées d’extinction, comprendre les causes de leur déclin, puis tester et valider des moyens pour enrayer ce phénomène. Cependan...

We present results on the detection of individuals in plant counts from an extensive field experiment in which we sampled multiple species and habitats, and in which several observers with different levels of experience in botany participated. We found that detection probability was always imperfect, and varied with multiple observational and ecolo...

1. Population size is a crucial parameter for both ecological research and conservation planning. When individuals are aggregated, estimating the size of a population through sampling raises methodological challenges, as the high variance between sampling units leads to imprecise estimates. Choosing the right sample design depending on the populati...

1. The estimation of population size and its variation largely relies on counts of individuals, generally carried out within spatial units such as quadrats or sites. Missing individuals during counting (i.e. imperfect detection) results in biased estimates of population size and trends. Imperfect detection has been shown to be the rule in animal st...

We present results on the relative precision of sampling methods for both virtual populations and natural plant populations mapped in the field, depending on the level of spatial aggregation of individuals. We found that spatially balanced sampling methods yield substantially more precise estimates than random ones, and explain the underlying mecha...