Four Ambrosia species are currently identified in Israel: the invasive perennial species Ambrosia confertiflora DC., the naturalized perennial species Ambrosia tenuifolia Spreng. and Ambrosia psilostachya DC., and the casual annual species Ambrosia artemisiifolia L. In this study, we performed a comparative analysis of three species: A. confertiflora, A. tenuifolia, and A. artemisiifolia. We found differences in morphology, growth and flowering phenology and physiology that may explain, besides climatic constraints, the factors involved in the differing invasion status of these species in Israel. A. artemisiifolia and A. confertiflora use strategies typical of invasive species: rapid growth and regeneration, phenotypic plasticity and reproductive ability. These characteristics have enabled the spread of A. confertiflora in Israel. However, A. artemisiifolia has not become established in Israel due to the country's dry summers. The naturalized populations have survived in ecological niches in Israel for many years, but due to their slow growth and low numbers of viable achenes, they have not spread.
Coastal sand dunes are susceptible to invasive plants that significantly alter these endangered ecosystems. Acacia saligna is a small Australian tree that has become a significant invasive plant in Israel and in many other Mediterranean countries. The aim of this research was to study the impact of A. saligna on the indigenous vegetation of three coastal habitats (sand dunes, inter-dune depressions, and aeolianite [sandstone] ridges) in the Nizzanim Long Term Ecosystem Research Nature Reserve, Israel. Plant observations were conducted in the spring, in the following site types: (1) sites planted with A. saligna and sites invaded by A. saligna; and (2) reference sites not invaded by A. saligna. A simple index, the aggregate ecological value, was developed in order to evaluate the impact and the ecological value of each habitat and site for conservation purposes. The results indicate that planting A. saligna and invasion by A. saligna changed plant community composition, reduced psammophyte species richness, caused the disappearance of most endemic, rare, and protected species, and overall reduced the ecological value of the Nizzanim Nature Reserve.
The article provides an analysis of the current situation with lectotypification of the generic name Salsola L. (Chenopodiaceae/Amaranthaceae sensu APG) and recent nomenclatural “resurrection” of the generic name Kali Mill., following molecular phylogenetic findings. Here we present additional arguments in favor of our recent nomenclatural proposal on conservation of the generic name Salsola with S. kali L. as the conserved type. Another option is the typification of Salsola with S. soda L., in which case taxa of the S. kali clade are placed in the genus Kali Mill. (sensu Akhani & Roalson) in its new circumscription. Positive and negative taxonomic and nomenclatural outcomes of each solution are discussed. Our position regarding the typification of Salsola is reconfirmed. The final decision on the nomenclatural fate of Salsola will be adopted at the XIX International Botanical Congress in 2017, following decisions and recommendations of two committees of the IAPT, which will evaluate our Salsola conservation proposal and report if typifications done by Standley in the North American Flora are supersedable.
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.