The question of the spread of an aposematic or of an otherwise visually defended plant type within a non-aposematic or a visually non-defended population is a long-standing enigma that has received considerable theoretical attention. However, the spreading of aposematic or otherwise visually defended plant genotypes within a non-aposematic or a non-visually-defended population has never, as far as is known, been shown or studied in nature in wild plant populations. This study investigates the loss of the various simultaneous types of defensive coloration in the spiny thistle Silybum marianum by a mutation that occurred independently and found in 13 wild populations in Israel. Mutant plants have plain leaves rather than leaves of the zebra-like wild-type, which has a white network of stripes on the upper leaf surface. The mutants never spread beyond several dozen meters and usually only over several meters. The mutation has a simple developmental origin, since the white variegation is the result of small air spaces formed between the epidermis and the photosynthetic parenchyma (causing no loss of photosynthetic capacity in white areas), and the mutants have no such subepidermal air spaces. In order to examine the possibility of establishing a pure population lacking this type of defensive coloration, seeds of mutant plants were collected from two wild populations where they grew mixed with the wild-type and a pure mutant population was selected and maintained for 4 years. Thus, 13 cases of very restricted spread of the visually defenseless mutant demonstrate the probable contribution of the variegation to plant fitness, supporting the hypothesis that conspicuous leaf variegation functions as defensive coloration.
A fully bibliographed thesaurus of the contributions by the late Avinoam Danin to the series “Med-Checklist Notulae”, “Euro+Med Notulae”, and “Euro+Med-Checklist Notulae” is presented. The contributions of Avinoam Danin to the Med-Checklist and the Euro+Med PlantBase projects over 35 years is evaluated with respect to taxonomic and floristic content, co-authors, and new area and status records. This part of Danin's work, only fragmentarily given in customary bibliographies, is documented in quotable detail. Cross-reference helps to commemorate the invaluable contributions by Avinoam to the inventorying of plant diversity in Europe and the Mediterranean.
The phylogenetic structure of communities (PSC) reveals how evolutionary history affects community assembly processes. However, there are important knowledge gaps on PSC patterns for annual communities and there is a need for studies along environmental gradients in dry ecosystems where several processes shape PSC.
Here, we investigated the PSC of annual plants along an aridity gradient in Israel, including eight years, two spatial scales, the effects of shrubs on understory, and the phylogenetic signal of important traits. Increasing drought stress led to overdispersed PSC at the drier end of the gradient, indicating that species were less related than expected by chance. This was supported at a smaller spatial scale, where within the drier sites, communities in open – more arid – habitats were more overdispersed than those under nurse shrubs. Interestingly, some key traits related to drought resistance were not conserved in the phylogeny. Together, our findings suggested that while habitat filtering selected for drought resistance strategies, these strategies evolved independently along multiple contrasting evolutionary lineages. Our comprehensive PSC study provides strong evidence for the interacting effects of habitat filtering and plant–plant interactions, particularly highlighting that the conservative evolution of traits should not be assumed in future interpretations of PSC patterns.
Quercus cerris L. and Q. suber L. are sympatric for a small portion of their distribution area, where they occasionally hybridize. The hybrid's fitness is low in the wild and there is no significant record of backcrossing; due to occasional reproduction and to the long life span, however, rare individuals of hybrid origin occur scattered in southeastern Europe, even outside of the current range of one or other of the parent species, and can be assigned to the corresponding nothospecies. Several names have been published for this taxon, and others have been variously misapplied to it for more than two centuries, resulting in a true nomenclatural jumble. A thorough examination of the types and protologues of all relevant names leads to the conclusion that Q. ×crenata Lam., a name often overlooked, is the correct name for this nothospecies; Q. ×hispanica Lam., the name adopted by most authors, is a name of unresolved application, which definitely refers to a different hybrid; all other competing names are junior heterotypic synonyms.
The ability to cope with combinations of stresses is crucial for the establishment and development of young plants and determines processes of population dynamics. Seedlings and saplings of Mediterranean woody species in woody ecosystems often experience both drought and shade stresses. Our study aims at understanding the effect of the combined stresses of drought and shade on young sapling survival and development. We tested three alternative hypotheses: (1) Drought decreases plant performance in shade. (2) The impact of drought is lessened in shade or shade may even ameliorate plant performance under drought. (3) Plant response to shade is independent of plant response to water availability. The first and second hypotheses imply an interaction between drought and shade, while the third implies an orthogonal impact of drought and shade. We also ask what are the functional morphological traits that are involved in tolerating shade and drought stresses. We tested the hypotheses and questions focusing on Sarcopoterium spinosum as a model species in a fully factorial container experiment with three shading levels and two levels of water availability. The results demonstrate that moderate shading (50%) ameliorates seedling performance (measured by final biomass) under dry conditions. In contrast, when water was available, shading had a monotonic negative effect on seedling performance. Conversely, shade and drought had an independent effect on biomass partitioning and under drought – allocation to roots increased, while under shade allocation to leaves increased. The dry conditions did not cause a reduction in shade tolerance, and both shade avoidance and tolerance morphology were evidenced under moderate (50%) and deep (70%) shading (stem elongation, increased leaf area). Deep rooting – a drought-avoidance trait – was similar in high and low water availability. Our overall results support the hypothesis that shade ameliorates drought stress. Moreover, S. spinosum demonstrates that woody species inhabiting water-limited ecosystems may have a repertoire of traits that allows simultaneous tolerance to both drought and shade.
The Levant's biogeographic setting also makes it a palaeobiologically significant location, as will be demonstrated here for the past 135 million years of plant evolution. Some of the earliest evidence for angiosperm diversification and dominance come from the Levant, and are possibly related to the environmental conditions in the region at the time. Later mammal migrations from Eurasia to Africa through the Levant resulted in the evolution of African savannas and the rise of grasses and humankind. Humankind left Africa through the Levant, in which it also settled. Agriculture and crop evolution began in the Levant and were to a large part an outcome of previous events. Thus, the geographic and climatic position of the Levant played significant direct and indirect roles in shaping plant life as we know it today. A temporally broad view of the Levant's role in plant evolution offers us insights into the relations between abiotic and biotic evolutionary drivers. This review corroborates that biotic evolutionary drivers are stronger and more apparent at small spatial, temporal and taxonomic scales, whereas abiotic evolutionary drivers are stronger and more apparent at larger scales.
The results of a statistical biometric study of the Centaurea busambarensis complex, which represents the C. cineraria aggregate in Sicily and its offshore islets, are presented. Seventeen populations, representing all seven previously recognized taxa (four species and three additional subspecies) plus a presumed undescribed one were studied. The statistical analysis (PCA and DA) of 26 morphological characters confirmed these eight taxa as distinct, geographically or ecologically vicarious units of equal weight, not supporting their treatment at different ranks. Consequently, they are recognized here as species, resulting in the description (with illustration) of one of them as new (C. aegusae, endemic to Favignana island, Egadi Archipelago, W Sicily) and in a new combination at species rank (C. seguenzae). A key for identifying the eight species of the complex is provided.
The genus Mollugo L. comprises ca. 35 species distributed throughout the tropics, and it is clearly polyphyletic. The seed morphology and ornamentation of 27 Mollugo representatives is studied with regard to their significance for systematics and taxon delimitation. The species belonging to the “M. cerviana” and “M. fragilis” groups, as well as M. tenella, are characterized by D-shaped or roundish seeds, whereas other taxa have reniform seeds. The seed ornamentation can be considered to be one of the most valuable characters for disentangling the taxonomic diversity in the genus. Mollugo cerviana shares the same reticulate ornamentation with M. namaquensis, M. pusilla, M. tenella and M. tenuissima, while the smooth surface is peculiar to M. fragilis, M. spathulata and M. walteri. The close relationship of M. fragilis and relatives to Hypertelis spergulacea is carpologically supported. Some taxa share a papillate ornamentation (M. decandra, M. floriana, M. molluginis, M. nudicaulis, M. pentaphylla, M. pentaphylla var. rupestris), but this character appears to be a homoplasy in the light of existing molecular phylogeny. The “Mollugo nudicaulis” group (M. angustifolia, M. cuneifolia, M. decandra, M. nudicaulis s.str., M. nudicaulis var. navassensis) as well as M. molluginis from the “M. pentaphylla” group have foveolate cell boundaries. Seed ornamentation can be an additional character supporting reinstatement at species rank of the forgotten New Caledonian taxon M. digyna, as well as Caribbean M. nudicaulis var. navassensis. Mollugo pentaphylla and M. verticillata are found not to be uniform in seed characters. The endemics of the Galapagos archipelago that have been studied (M. flavescens, M. floriana, M. gracillima, M. snodgrassii) differ in their ornamentation from M. verticillata. Mollugo tenella is distinguished from all other species in having short, trichome-like depositions of epicuticular wax on the seed surface. The discovered carpological characters can be important for the delimitation and taxonomy of different Mollugo groups.
In recent decades, recreational activities in natural open areas have increased substantially. At the same time, stresses imposed upon these areas have increased considerably as a result of a significant reduction in their dimension. These activities strongly affect ecosystem attributes and processes.
This paper intends to review several studies that were conducted in one of the protected areas in Israel, Ramat Hanadiv Park, aiming to (a) quantify the rate of pedestrian trail development and (b) examine the impact of high and low trampling intensities on soil and vegetation properties at different trail sections (center, edge and control – a natural area adjacent to the trail).
The following properties were examined: soil compaction, bulk density, aggregate size distribution, organic matter, moisture, electrical conductivity, pH, sodium and potassium concentrations, vegetation cover, species richness, and composition.
The results indicated that: (a) the number of pedestrian trails increased slightly between the years 1944 and 1990; (b) soil properties, except for soil compaction and aggregate size, were not affected by low trampling intensity. A slight decrease in the soil measured properties was recorded at trail centers. However, under high trampling intensity, a reduction in most soil measured properties was detected on all trail sections; (c) vegetation cover, height and species richness were lower at the trail center under high and low trampling intensities. Herbaceous plant species that are common in compacted soils were found under intense trampling impacts.
The conclusions from the studies conducted at Ramat Hanadiv Park were: (a) there is a positive correlation between trampling intensities and soil and vegetation properties; (b) an increase in trampling intensity is followed by spatial degradation of soil properties beyond the trail's visible boundaries (what we referred as the “control”); and (c) most of the trails in Ramat Hanadiv Park experience low trampling intensities.