SPATIAL FLOWER PARAMETERS AND INSECT SPATIAL VISION

The present article reviews recent and older literature on the spatial parameters that flowers display, as well as on the capacities of anthophilous insects to perceive and use these parameters for optimizing their foraging success. Although co-evolution of plants and pollinators has frequently been discussed with respect to floral colours and insect colour vision, it has rarely been assessed with respect to insect spatial vision and spatial floral cues, such as shape, pattern, size, contrast, symmetry, spatial frequency, contour density and orientation of contours. This review is an attempt to fill this gap. From experimental findings and observations on both flowers and insects, we arrive at the conclusion that all of the spatial and spatio-temporal parameters that flowers offer are relevant to the foraging task and are tuned to the insect's visual capacities and visually guided behaviour. We try, in addition, to indicate that temporal cues are closely related to spatial cues, and must therefore be included when flower–pollinator interactions are examined. We include results that show that colour vision and spatial vision have diverged over the course of evolution, particularly regarding the processing of spatio-temporal information, but that colour vision plays a role in the processing of spatial cues that are independent of temporal parameters. By presenting this review we hope to contribute to closer collaboration among scientists working in the vast fields of botany, ecology, evolution, ethology and sensory physiology.     

Floral symmetry and nectar guides: ontogenetic constraints from floral development, colour pattern rules and functional significance

The accord between symmetries of flower shape (external contours) and nectar guides (internal contours) was examined using the bulbous flora of South Africa, and in the general floras of Britain, Alpine Colorado, Canadian Arctic and Israel. It was found that radially symmetrical flowers have radially symmetrical nectar guides whereas bilaterally symmetrical flowers have bilaterally symmetrical nectar guides. It is suggested that the complementarity between the external and the internal contours of the flower increases the probability that, and efficiency with which, a bee moves into the flower's centre and towards the sporophylls and access to floral rewards, regardless of the flower's form and the bee's previous experience. Patterns of coloration of tepals against background and nectar guides against tepals also accord with behavioural and sensory characteristics of pollinators. It is suggested that the complementarity of contours is probably constrained by floral development, but patterns of coloration of tepals against background and nectar guides against tepals is constrained by pollinators' sensory physiology.     

Red anemone guild flowers as focal places for mating and feeding by Levant glaphyrid beetles

Several species of glaphyrid (Scarabaeoidea: Glaphyridae) beetles forage and mate on Mediterranean red bowl‐shaped flowers. In red anemones and poppies in Israel, female beetles occupy only a subset of the flowers, do not aggregate, and are hidden below the petals. This raises the question of how males find their mates. In the present study, we investigated the hypothesis that males and females orient to similar plant‐generated cues, thereby increasing their mate encounter prospects. Previous studies have demonstrated that beetle attraction to red models increases with display area. Choice tests with flowers and with models indicate that both male and female beetles prefer large displays. In anemones, beetles rest, feed, and mate mainly on male‐phase flowers, which are larger than female‐phase flowers. Poppies that contain beetles are larger than the population average. These findings support the hypothesis that males and females meet by orienting to large red displays. Corolla size correlates with pollen reward in both plant species, suggesting that visits to large flowers also yield foraging benefits. Male beetles often jump rapidly among adjacent flowers. By contrast to the preference for large flowers by stationary individuals, these jump sequences are random with respect to flower sex‐phase (in anemone) and size (in poppy). They may enable males to detect females at close range. We hypothesize that males employ a mixed mate‐searching strategy, combining orientation to floral signals and to female‐produced cues. The glaphyrids' preference for large flowers may have selected for extraordinarily large displays within the ‘red anemone’ pollination guild of the Levant. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 99 , 808–817.     

Variability in Prosopis farcata in Israel: anatomical features of the seed

Anatomical features of seeds of Prosopis farcata (Banks & Solander) Eig, collected at nine localities from various geographical regions and habitats in Israel, were studied. The seeds differ in size, shape and colour, and also in the cracking ability of the surface layer and whether the palisade layer peels off from the rest of the testa upon imbibition or not.
The gum extruded during imbibition is formed in gum cavities extending from the endosperm throughout the testa up to the palisades.
Water penetration is apparently barred by the outermost wall layers of the external cells of the testa (palisade caps).