Abstract: Although proximity to cover has been routinely considered as an explanatory variable in studies investigating prey behavioral adjustments to predation pressure, the way it shapes risk perception still remains equivocal. This paradox arises from both the ambivalent nature of cover as potentially both obstructive and protective, making its impact on risk perception complex and context-dependent, and from the choice of the proxy used to measure proximity to cover in the field, which leads to an incomplete picture of the landscape of fear experienced by the prey. Here, we study a simple predator-prey-habitat system, i.e., rabbits Oryctolagus cuniculus facing feral cat Felis catus predation on Kerguelen archipelago. We assess how cover shapes risk perception in prey and develop an easily implementable field method to improve the estimation of proximity to cover. In contrast to protocols considering the “distance to nearest cover”, we focus on the overall “area to cover”. We show that fine-scale habitat use by rabbits is clearly related to our measure, in accordance with our hypothesis of higher risk in patches with smaller area to cover in this predator-prey-habitat system. In contrast, classical measures of proximity to cover are not retained in the best predictive models of habitat use. The use of this new approach, together with a more in-depth consideration of contrasting properties of cover, could help to better understand the role of this complex yet decisive parameter for predator-prey ecology.

Abstract: Five species of the terrestrial diatom genus Luticola D.G.Mann were found during a taxonomic survey of two small volcanic islands, Ile Amsterdam and Ile Saint-Paul (Southern Indian Ocean). Apart from the two already known Luticola species L. beyensii Van de Vijver et al. and L. subcrozetensis Van de Vijver et al., two new species are described: L. ivetana Chattová & Van de Vijver sp. nov. and L. vancampiana Chattová & Van de Vijver sp. nov. Finally, one, up to now unknown, Luticola species is briefly discussed and illustrated. Detailed morphological descriptions of these taxa are provided based on both light and scanning electron microscopy observations. Morphological features of the new species are compared to morphologically similar taxa, and notes on their ecology and biogeography are added.

Abstract: During a survey of the freshwater diatom flora on the sub-Antarctic islands of the southern Indian Ocean, two new Planothidium species were observed, showing some resemblance to Planothidium delicatulum. Therefore, the type material of Achnanthidium delicatulum Kützing was analysed, a common species in northern hemisphere waterbodies that was later transferred to the genus Planothidium. Additionally the material of Types du Synopsis des Diatomées de Belgique n° 234, designated in 1980 as neotype for Achnanthes delicatula was investigated. This analysis showed that the population in Types n° 234 is not conspecific with Achnanthidium delicatulum but in fact is a population of Planothidium galaicum. Both Planothidium species in the investigated Antarctic material are described as new to science: P. lilianeanum Van de Vijver sp. nov. and P. australodelicatulum Van de Vijver, C.E.Wetzel et Ector sp. nov. The new species can be differentiated based on differences in valve outline, presence of ridges and silica outgrowths on the rapheless valve, the structure of the raphe and the shape and size of the central area. Notes on the ecology and distribution of the new Antarctic species are added. Achnanthidium delicatulum is formally lectotypified.