Floral color change was studied in Lupinus pilosus L. to elucidate its ecological significance for both the plant and the pollinators. It was found that the change in the banner spot from white to purple was enhanced by artificial pollination. White phase flowers offered more pollen as reward to foraging pollinators than did purple phase flowers. The changes in color and reward were recognized by the pollinators and affected their foraging behavior. Pollinators preferred pre-change flowers and avoided post-change ones, thus increasing the chance that white phase flowers would be pollinated. It is suggested that the increase in outcrossing rate caused by pollinator activity could be the advantage and the driving force for the evolution of the color change mechanism in L. pilosus.
Gidi Ne'eman and Rakefet Nesher
Gidi Ne'eman and Amots Dafni
The typical Mediterranean phrygana has a very rich biodiversity of plants and of solitary bees. Fire may kill the brood of soil-nesting and other solitary bees and may affect pollen and nectar sources. Such changes would be expected to influence seed production in populations of post-fire obligate seeder species and thus also their population dynamics. We compared nectar standing crop, flower visitation rate of bumble bees and solitary bees, and consequent seed production in a typical Mediterranean shrub (Salvia fruticosa Miller) growing in unburned east Mediterranean phrygana vegetation and in an adjacent burned area. The volume of nectar standing crop in the burned area was higher than in the unburned area, while the nectar concentration showed the opposite trend. The mean frequency of Bombus' visits was higher in the burned area, while solitary bees visited flowers only in the unburned habitats. The seed production of S. fruticosa was significantly lower in the burned area. This reduction might have a long-term effect on post-fire species composition and abundance due to the fact that this species is an obligate post-fire seeder. The present evidence indicates that the bee-dependent pollination environment was not re-balanced even six years after fire. This situation has important implications concerning plant species and their bee pollinator diversity.
Gabriel Schiller, Gidi Ne'eman and Leonid Korol
Israel's largest natural Pinus halepensis Mill. forest is on the Mt. Carmel range and belongs to the distinct East Mediterranean genetic group. Most of this forest is the result of invasion of abandoned fields and grazing lands, resulting in a heterogeneous pine forest with an understory of broad-leaf shrubs and trees. Species composition, vegetation cover, pine-stand structure, and pine genetic diversity of plots in sites of known fire history, burned 5, 11, and 20 years ago, were studied with adjacent unburned sites forming a chronosequence.
Except for annual species, no species replacement took place during post-fire succession. The main observed changes were in the cover of species and of plant life forms. The ratio of tree/dwarf-shrub cover was found to be linearly related to the number of years elapsed since the last fire. Therefore, this ratio could serve as an index to determine the successional stage of Aleppo pine stands with unknown fire history. It is estimated that 30–40 years are needed for full recovery of Aleppo pine stands after fire, depending upon site quality. The stands of post-fire regeneration are of uniform age and are less variable in their structure than unburned stands. The genetic distance among the various Pinus halepensis subpopulations was found to be very small; most of the genetic variability was due to within-subpopulations variability, with almost no variability among subpopulations. Alleles that are typical of West Mediterranean P. halepensis populations or of P. brutia, were found in two post-fire subpopulations (stands), indicating pre-fire cross pollination between native Pinus halepensis trees and trees in adjacent pine plantations of foreign origin.
The conclusion is that fire has little effect on species composition and on vegetation structure, but that it alters the Aleppo pine stand structure.
Amots Dafni, Ido Izhaki and Gidi Ne’eman
Mediterranean type ecosystems are among the world's most fire-prone regions. Focusing on the Mediterranean basin, we review the literature and propose conceptual models to explain the direct and indirect effects of fire on plant-pollinator interactions, seed dispersers, and predators, as well as the temporal changes in these systems along post-fire succession and ecosystem recovery processes. Post-fire plant communities change in their composition, structure, floral resources, as well as seed and fruit resources. Fire directly affects communities of pollinators, seed dispersers, and seed predators mainly by mortality, and indirectly through changes in the quality and quantity of food and nesting resources. Pollinators, seed-dispersers, and seed predators depend on plant community composition and on the flower, seed, and fruit resources they produce. As a consequence, their community composition, structure, and function are expected to vary in response to post-fire temporal and spatial changes in plant communities, which in turn depend on fire severity, frequency, scale, and the distance from fire-edge, as well as their foraging range. In return, the changes resulting from fire in pollinator, seed-disperser and seed predator communities may affect plant fecundity and plant community composition.
Ofrit Shavit, Amots Dafni and Gidi Ne'eman
The hypothesis that honeybees (Apis mellifera) compete for floral resources with native bees was studied mainly in areas outside the original range of the honeybees, i.e., where they are introduced. We studied the effect of honeybees on the foraging behavior of native solitary bees in Israel, within the natural distribution range of the honeybee, by manipulating the presence and absence of beehives in the study sites: Ramat Hanadiv Park and Carmel National Park. We examined the possible degree of competition between honeybees and native solitary bees by observing their foraging on focal nectariferous plants. Temporal introduction of hives increased the visitation frequencies of honeybees to our focal plants and decreased the overall average visitation frequencies of native solitary bees. However, the effect of honeybees varied among native bee species, focal plants, and years. In some cases, honeybees had a negative effect on visitation rates of the other bees, while in other cases we did not find such an effect. The other bees also did not shift to forage on other flowering plants, and did not change their temporal activity pattern as a response to increased foraging by honeybees. The results provide partial evidence for behavioral competition between honeybees and native bees. For this reason, we recommend prohibiting introduction of beehives to all nature reserves in Israel, as a precaution aimed at protecting the native bee fauna. This may help conserve their contribution to biodiversity and pollination of common and rare native plants as well as crops.
Simcha Lev-Yadun and Gidi Ne'eman
Patterns of color changes of senescent colorful aposematic prickles, spines, and thorns are described. Color changes make the older prickles, spines, and thorns less conspicuous and they lose their aposematic character. The color changes and the aposematic character loss occur when the defended organs become less edible to large herbivores because of their increased size, mechanical rigidity, or chemical defense or when there is no need for defense. Reducing the cost of defense seems to be the reason for the ephemeral nature of conspicuousness of plant prickles, spines, and thorns.
Gidi Ne’eman, Avi Shmida and Avi Perevolotsky
Gidi Ne’eman, Ido Izhaki and Jon E Keeley
Gidi Ne’eman, Simcha Lev-Yadun and Margarita Arianoutsou
Fire is a frequent and severe disturbance that affects plants on large scales, especially in Mediterranean-type ecosystems (MTE). Plants have evolved traits that confer resilience to fire and other disturbances, ensuring their persistence in fire-prone systems, but MTE floras differ in fire-related traits and their frequencies. Using available literature, we compare fire-related plant traits and syndromes of the flora of the Mediterranean Basin with those of other MTEs, discuss the differences and their possible causes, and point to knowledge gaps. Plants with lignotubers are relatively rare in the Mediterranean, as is serotiny. Many Mediterranean species have physically dormant seeds that are cued to germinate after fire by heat shock, while the effect of smoke on seed germination in the Mediterranean flora is less common than in other MTEs. The geophytes in the MB that flower massively afterfire flowering are opportunistic and not obligate fire-stimulated flowering species. Based on this literature survey, we conclude that differences in current and historic fire regimes could account for differences among MTEs in plants' fire-related traits.
Sagi Nahum, Moshe Inbar, Gidi Ne'eman and Rachel Ben-Shlomo
Pistacia lentiscus L. (Anacardiaceae) is a common shrub in the Mediterranean vegetation. Throughout its distribution area, this species is the obligate host of the kidney-shaped gall-forming aphid Aploneura lentisci (Homoptera: Fordinae). Despite the wide distribution of Pistacia lentiscus in diverse habitats along a climatic gradient in Israel, our previous study did not reveal any pattern of ecologically related genetic differentiation. Here we examined changes in gall density and genetic diversity of the gall-forming aphid A. lentisci along its distribution gradient in Israel, in the neighboring island of Cyprus, and in Tunisia, North Africa. Gall density and mass differed significantly among the Israeli populations and were positively correlated with annual precipitation and plants' annual growth. Gene diversity of A. lentisci was very low in all populations and, as with its host plant, the genetic similarity was high within and among the Israeli populations and between the Israeli and Cyprian populations. To conclude, we found no evidence for any gene flow barrier and genetic differentiation among the aphid populations.