16 research outputs found
Empirical support for the biogeochemical niche hypothesis in forest trees
The possibility of using the elemental compositions of species as a tool to identify species/genotype niche remains to be tested at a global scale. We investigated relationships between the foliar elemental compositions (elementomes) of trees at a global scale with phylogeny, climate, N deposition and soil traits. We analysed foliar N, P, K, Ca, Mg and S concentrations in 23,962 trees of 227 species. Shared ancestry explained 60–94% of the total variance in foliar nutrient concentrations and ratios whereas current climate, atmospheric N deposition and soil type together explained 1–7%, consistent with the biogeochemical niche hypothesis which predicts that each species will have a specific need for and use of each bio-element. The remaining variance was explained by the avoidance of nutritional competition with other species and natural variability within species. The biogeochemical niche hypothesis is thus able to quantify species-specific tree niches and their shifts in response to environmental changes
Multimodal cues provide redundant information for bumblebees when the stimulus is visually salient, but facilitate red target detection in a naturalistic background
Our understanding of how floral visitors integrate visual and olfactory cues when seeking
food, and how background complexity affects flower detection is limited. Here, we aimed to
understand the use of visual and olfactory information for bumblebees (Bombus terrestris
terrestris L.) when seeking flowers in a visually complex background. To explore this issue,
we first evaluated the effect of flower colour (red and blue), size (8, 16 and 32 mm), scent
(presence or absence) and the amount of training on the foraging strategy of bumblebees
(accuracy, search time and flight behaviour), considering the visual complexity of our background,
to later explore whether experienced bumblebees, previously trained in the presence
of scent, can recall and make use of odour information when foraging in the presence
of novel visual stimuli carrying a familiar scent. Of all the variables analysed, flower colour
had the strongest effect on the foraging strategy. Bumblebees searching for blue flowers
were more accurate, flew faster, followed more direct paths between flowers and needed
less time to find them, than bumblebees searching for red flowers. In turn, training and the
presence of odour helped bees to find inconspicuous (red) flowers. When bees foraged on
red flowers, search time increased with flower size; but search time was independent of
flower size when bees foraged on blue flowers. Previous experience with floral scent
enhances the capacity of detection of a novel colour carrying a familiar scent, probably by
elemental association influencing attentionPeer reviewe