In honeybees, foragers use the waggle dance to communicate the direction and 'a distance' to a food source from the hive to other members of the colony. Behavioral studies indicate that dancing foragers estimate this 'distance' during outward flights (from the hive to the food source) based on visual cues, in particular optic flow, even over mountain slopes. While optic flow-based biologically plausible models for the honeybee visual odometer were previously presented, their robustness with respect to uneven terrain has not yet been investigated. In this study, we present a new model for the honeybee visual odometer, calledSuRf(forSurface-Reference Leveling model), which combines vertical oscillations with the constant reorientation of the honeybee's compound eye with respect to the slope overflown. As the simulated honeybee's compound eye is typically kept level with the surface below, the direction of perception of ventral and divergent optic flow tends to remain perpendicular to the surface, enhancing the robustness of their detection across terrain irregularities. Tested in open field simulations across uneven terrain and varied wind conditions, theSuRfmodel demonstrated greater accuracy compared to previous models evaluated under the same conditions, while keeping precision. The reliability of theSuRfmodel accounts for the observed 'mountain slopes' (uphill and downhill) behaviors in honeybees and offers promising applications for minimalistic aerial robots navigating uneven terrain and indoor spaces.
Habitat complexity (HC) promotes species richness and abundance. Aquatic environments are faced with intense pressures that threaten the 3D structure of the seafloor, with cascading effects on ecosystem functioning and biodiversity. Maerl or rhodolith beds are marine biogenic habitats created by few species of free-living non-geniculate coralline algae that aggregate and form complex structures. Although their high biodiversity has been attributed to the HC provided by coralline algal nodules, the mechanisms through which HC modification affect associated communities remains uncertain in face of numerous confounding factors. Hence, we tested how changes in the extent and nature of maerl complexity drive changes in biodiversity. Using long-term monitoring data from ten maerl beds in Brittany (France) over 12 years, we investigated the links between structural complexity, environmental conditions and benthic macrofaunal communities. HC was quantified at the coralline algal nodule and bed level, through morphometrics and density, and its effects on local diversity and on communities spatial and temporal variability were evaluated. HC promoted species richness and density of most taxa regardless of other environmental factors. These relationships were linear and no limiting threshold of complexity was found at a regional scale. HC played a more important role in driving regional diversity patterns than other measured environmental constraints individually, and beds with relatively lower HC were the most distinct in terms of community composition and structure. Species replacement was the main component of temporal variability and HC promoted community stability. While overall facilitative, the effects of HC might be taxa and trait-dependent, justifying comprehensive trait-based approaches. Our results reiterate the need to protect complex biogenic habitats.
