Irano-Turanian Floristic Region Research Articles

Evolutionary history of an Irano-Turanian cushion-forming legume (Onobrychis cornuta).

The Irano-Turanian region is one of the largest floristic regions in the world and harbors a high percentage of endemics, including cushion-like and dwarf-shrubby taxa. Onobrychis cornuta is an important cushion-forming element of the subalpine/alpine flora of the Irano-Turanian floristic region. To specify the genetic diversity among the populations of this species (including individuals of O. elymaitica), we employed nrDNA ITS and two noncoding regions of plastid DNA (rpl32-trnL(UAG) and trnT(UGU)-trnL(UAA)). The most striking feature of O. cornuta assemblages was the unexpectedly high nucleotide diversity in both the nDNA and cpDNA dataset. In the analyses of nuclear and plastid regions, 25 ribotypes and 42 haplotypes were found among 77 and 59 accessions, respectively, from Iran, Turkey, and Afghanistan. Network analysis of the datasets demonstrated geographic differentiation within the species. Phylogenetic analyses of all dataset retrieved O. cornuta as a non-monophyletic species due to the inclusion of O. elymaitica, comprising four distinct lineages. In addition, our analyses showed cytonuclear discordance between both nuclear and plastid topologies regarding the position of some O. cornuta individuals. The underlying causes of this inconsistency remain unclear. However, we speculate that chloroplast capture, incomplete lineage sorting, and introgression were the main reasons for this event. Furthermore, molecular dating analysis indicated that O. cornuta originated in the early Pliocene (around 4.8 Mya) and started to diversify throughout the Pliocene and in particular the Pleistocene. Moreover, O. elymaitica was reduced to a subspecific rank within the species.

Climatic stability and geological history shape global centers of neo- and paleoendemism in seed plants.

Assessing the distribution of geographically restricted and evolutionarily unique species and their underlying drivers is key to understanding biogeographical processes and critical for global conservation prioritization. Here, we quantified the geographic distribution and drivers of phylogenetic endemism for ~320,000 seed plants worldwide and identified centers and drivers of evolutionarily young (neoendemism) and evolutionarily old endemism (paleoendemism). Tropical and subtropical islands as well as tropical mountain regions displayed the world's highest phylogenetic endemism. Most tropical rainforest regions emerged as centers of paleoendemism, while most Mediterranean-climate regions showed high neoendemism. Centers where high neo- and paleoendemism coincide emerged on some oceanic and continental fragment islands, in Mediterranean-climate regions and parts of the Irano-Turanian floristic region. Global variation in phylogenetic endemism was well explained by a combination of past and present environmental factors (79.8 to 87.7% of variance explained) and most strongly related to environmental heterogeneity. Also, warm and wet climates, geographic isolation, and long-term climatic stability emerged as key drivers of phylogenetic endemism. Neo- and paleoendemism were jointly explained by climatic and geological history. Long-term climatic stability promoted the persistence of paleoendemics, while the isolation of oceanic islands and their unique geological histories promoted neoendemism. Mountainous regions promoted both neo- and paleoendemism, reflecting both diversification and persistence over time. Our study provides insights into the evolutionary underpinnings of biogeographical patterns in seed plants and identifies the areas on Earth with the highest evolutionary and biogeographical uniqueness-key information for setting global conservation priorities.

Dated Phylogeny of Astragalus Section Stereothrix (Fabaceae) and Allied Taxa in the Hypoglottis Clade.

The Astragalus subgenus Hypoglottis Bunge, which consists of several sections, is one of the taxonomically most complicated groups in the genus. The Astragalus section Stereothrix Bunge belongs to this subgenus and is a significant element of the Irano-Turanian floristic region. A molecular phylogenetic analysis of this section and its closely related taxa using nuclear ribosomal DNA internal transcribed spacers (ITS) and external transcribed spacer (ETS) regions as well as plastid matK sequences were conducted. Parsimony analyses and Bayesian phylogenetic inference revealed that the section is not monophyletic in its current form, as some taxa belonging to closely related sections such as Hypoglottidei DC. and the Malacothrix Bunge group within the sect. Stereothrix render it paraphyletic. Moreover, species groups belonging to sect. Stereothrix are placed in different clades within the phylogenetic tree of subgenus Hypoglottis, which indicates polyphyly, i.e., multiple independent origins of taxa placed in the sect. Stereothrix. Molecular dating of the group estimated an age of 3.62 (1.73-5.62) My for this assemblage with the major diversification events happening during the last 2 My. Many species groups separated only within the last 0.5 to 1 My. Based on morphological and molecular data, we discuss the phylogenetic relationships of the groups and synonymy of species. In addition, the included taxa of sect. Hypoglottidei are not monophyletic and include species belonging to sects. Hololeuce, Koelziana, Malacothrix, Onobrychoideae, and Ornithodpodium group within the sect. Stereothrix taxa. We conclude that only an analysis including all groups and nearly all species of the sections within the Hypoglottis clade can finally result in an new evolutionary-based system for these taxa.

Ecological Niche Modelling and Potential Distribution of Artemisia sieberi in the Iranian Steppe Vegetation

Artemisia sieberi Besser occurs in many parts of the Irano-Turanian floristic region, which is mostly distributed throughout the Iranian plateau, especially in Iran. This study aimed to identify the effect of the soil and topography variables on A. sieberi distribution. We used canopy cover data to fit models using generalized additive models (GAMs). The results showed that the response pattern of A. sieberi along with the gradient of soil clay, soil saturation moisture, soil nitrogen and soil acidity followed the monotonic increase model, and its canopy cover percentage augmented by increasing the values of the factors. Conversely, the A. sieberi canopy cover percentage decreased by increasing the amount of soil sand, bare soil and the geographic aspect. The A. sieberi responses are in contrast to the niche theory. The relationship between the species response pattern and the gradients of soil silt, soil salinity, lime percentage, organic carbon, altitude, land slope, litter, gravel percentage, stone percentage, mean annual precipitation and mean annual temperature followed a unimodal model (consistent with the niche theory). The optimal growth limits for these factors were 32%, 1.75 ds/m, 35%, 1.3%, 2000 m, 43%, 10%, 32%, 250 mm and 15 °C, respectively. Our results highlight that environmental factors, such as soil texture, amount of soil lime, mean annual precipitation, altitude and land slope, had quantifiable effects on the performance of A. sieberi. Our findings could provide useful information for improvement, restoration and conservation programs. However, a further comprehension of the species–environment relationship is needed to predict the effects of climate change on the species habitat.

A new classification of C4- Atriplex species in Russia, with the first alien record of Atriplexflabellum (Chenopodiaceae, Amaranthaceae) from North Siberia.

For a long time, the systematics of Atriplex was based solely on morphological characters and leaf anatomy. The latest worldwide phylogenetic study of Atriplex significantly improved our knowledge about the relationships within the genus, but a new classification has not been put forward thus far. Here we re-evaluate the taxonomy of C4-species of Atriplex that are native to Russia. Seven species are classified into two sections, A.sect.Obione (incl. A.sect.Sclerocalymma, syn. nov.) (A.altaica, A.centralasiatica, A.rosea, A.sibirica, and A.sphaeromorpha), and A.sect.Obionopsis (incl. A.sect.Psammophila, syn. nov.) (A.fominii and A.tatarica). Although the majority of Eurasian C4-species have similar morphology, leafy inflorescence is a typical character for A.sect.Obione. The members of A.sect.Obionopsis are characterised mostly by aphyllous inflorescences, but some species (A.laciniata, A.pratovii, and A.tornabenei) have leafy inflorescences. Geographically, almost all members of A.sect.Obione are confined to Central Asia, although A.rosea is a typical Mediterranean element and A.argentea occurs in North America. The representatives of A.sect.Obionopsis are distributed mostly in the Mediterranean and the Irano-Turanian floristic region. The alien status of A.rosea, A.sibirica and A.tatarica is discussed. Atriplexflabellum, a desert species from the Irano-Turanian region, is reported for the first time from Russia (Yamalo-Nenets Autonomous District, North Siberia) as a casual alien. This species occupies a phylogenetic position distant from both aforementioned sections. An identification key to all C4-species of the genus growing in Russia is given, and a sectional checklist with updated nomenclature and revised synonymy is provided.

From Western Asia to the Mediterranean Basin: Diversification of the Widespread Euphorbia nicaeensis Alliance (Euphorbiaceae).

The Mediterranean Basin is an important biodiversity hotspot and one of the richest areas in the world in terms of plant diversity. Its flora parallels in several aspects that of the Eurasian steppes and the adjacent Irano-Turanian floristic region. The Euphorbia nicaeensis alliance spans this immense area from the western Mediterranean to Central Asia. Using an array of complementary methods, ranging from phylogenomic and phylogenetic data through relative genome size (RGS) estimation to morphometry, we explored relationships and biogeographic connections among taxa of this group. We identified the main evolutionary lineages, which mostly correspond to described taxa. However, despite the use of highly resolving Restriction Site Associated DNA (RAD) sequencing data, relationships among the main lineages remain ambiguous. This is likely due to hybridisation, lineage sorting triggered by rapid range expansion, and polyploidisation. The phylogenomic data identified cryptic diversity in the Mediterranean, which is also correlated with RGS and, partly, also, morphological divergence, rendering the description of a new species necessary. Biogeographic analyses suggest that Western Asia is the source area for the colonisation of the Mediterranean by this plant group and highlight the important contribution of the Irano-Turanian region to the high diversity in the Mediterranean Basin. The diversification of the E. nicaeensis alliance in the Mediterranean was triggered by vicariance in isolated Pleistocene refugia, morphological adaptation to divergent ecological conditions, and, to a lesser extent, by polyploidisation.

Centrocoris volxemi (Puton) (Hemiptera: Heteroptera: Coreidae), First Records for North America and Second Species of the Genus in the United States

Centrocoris volxemi (Puton) is a Palearctic coreid native to the Irano-Turanian floristic region and is reported here for the first time in North America and the western US (Utah and Idaho). The species was collected during surveys in Utah in 2021. We also discuss online records and images from 2020–2021 in Utah and Idaho that appear consistent with C. volxemi. The number of records, broad distribution, and field observations suggest that the species is firmly established. Field observations indicate that the primary host in the US is prickly Russian thistle, Salsola tragus L. We provide diagnostic characters and illustrations of the species to facilitate its identification and separation from Centrocoris variegatus Kolenati, another Palearctic species established in the US and first reported from central to central-western California in 2009.

Genome Size and Chromosome Number Evaluation of Astragalus L. sect. Hymenostegis Bunge (Fabaceae).

Astragalus section Hymenostegis is one of the important characteristic elements of thorn-cushion formations in the Irano-Turanian floristic region. In this paper, we examined the chromosome number of 17 species (15 new reports) and provide estimates of genome size for 62 individuals belonging to 38 taxa of A. sect. Hymenostegis, some species outside this section, plus two Oxytropis species. Based on chromosome counts 11 species were found to be diploid (2n = 16), four species tetraploid (2n = 32) and two taxa hexaploid (2n = 48). From genome size measurements on silica-gel dried material, three ploidy levels (2x, 4x and 6x) were inferred, with a majority of species being diploid. The 2C values reach from 2.07 pg in diploid Astragalus zohrabi to 7.16 pg in hexaploid A. rubrostriatus. We found indications that species might occur with different cytotypes. A phylogenetic framework using nrDNA ITS sequences was constructed to understand the evolution of ploidy changes and genome sizes. It showed that genome size values among the studied taxa differ only slightly within ploidy levels and are nearly constant within most species and groups of closely related taxa within the genus Astragalus. The results of this study show that there is a rather strong correlation between genome sizes and chromosome numbers in sect. Hymenostegis. The resolution of the ITS-based phylogenetic tree is too low to infer evolutionary or environmental correlations of genome size differences. Polyploidization seems to contribute to the high species number in Astragalus, however, in sect. Hymenostegis it is not the main driver of speciation.

Phylogeographic and SNPs Analyses of Bemisia tabaci B Mitotype Populations Reveal Only Two of Eight Haplotypes Are Invasive.

Simple SummaryThe whitefly Bemisia tabaci taxon consists of an undefined number of morphologically identical genetic variants of which only a few, including the B, harbor invasive haplotypes. These haplotypes have potential to upsurge and become important pests and plant virus vectors in irrigated agroecosystems worldwide. In the 1980s, unprecedented outbreaks associated with the B variant were reported worldwide, however, the precise origin(s) of the invasive haplotypes has not been determined. In this study, available B. tabaci mitochondrial gene sequences were examined for patterns of conserved single nucleotide changes (SNPs). The whitefly sequence records represented North Africa-Middle Eastern habitats, the proposed B variant center of origin, and distant locales recently invaded by haplotype(s) of the B variant. Unexpectedly, the analysis revealed eight SNPs groups (haplotypes) demonstrating that the genetic architecture of the B mitoype is more complex than previously recognized. Also, the distribution patterns of the eight B haplotypes were tightly linked to well-defined eco-geographic regions, suggesting the different groups have diversified by geographic isolation. Contrary to claims that collectively, the B variant is invasive, only two of the eight haplotypic groups have established in geographical locations outside of their zone of endemism.The Bemisia tabaci cryptic species contains 39 known mitotypes of which the B and Q are best recognized for having established outside their extant endemic range. In the 1980s, previously uncharacterized haplotype(s) of the B mitotype rapidly established in tropical and subtropical locales distant from their presumed center of origin, leading to displacement of several native mitotypes and extreme damage to crops and other vegetation particularly in irrigated agroecosystems. To trace the natural and evolutionary history of the invasive B haplotypes, a phylo-biogeographic study was undertaken. Patterns of single nucleotide polymorphisms (SNPs) and signatures potentially indicative of geographic isolation were investigated using a globally representative mitochondrial cytochrome oxidase I gene (mtCOI) sequence database. Eight haplotype groups within the North Africa-Middle East (NAFME) region were differentiated, NAFME 1–8. The NAFME 1–3 haplotypes were members of the same population that is associated with warm desert climate niches of the Arabian Peninsula and east coastal Africa-Ethiopia. The NAFME 4 and 5 haplotypes are endemic to warm and cold semi-arid niches delimited by the Irano-Turanian floristic region, itself harboring extensive biodiversity. Haplotypes 6 and 7 co-occurred in the Middle East along eastern Mediterranean Sea landmasses, while NAFME 8 was found to be endemic to Cyprus, Turkey, and desert micro-niches throughout Egypt and Israel. Contrary to claims that collectively, the B mitotype is invasive, NAFME 6 and 8 are the only haplotypes to have established in geographical locations outside of their zone of endemism.

Changes in flora, life forms and geographical distribution of herbaceous plant species along an altitudinal gradient in oak forests, Iran

Intended to examine the effects of altitude on flora, life forms and geographical distribution of herbaceous species, this study was conducted in Kabirkouh forests of Darreshahr, located in Ilam Province, Iran, by selecting an area (circa 300 ha) in this forest. The study area was divided into three elevational classes and 63 systematic random plots were sampled (21 in each of the elevational classes). In order to record the herbaceous cover, the surface area of the plots was determined using the minimal area method. Then the herbaceous species and their percent coverage were recorded based on the Van der Marel criterion. A total of 109 herbaceous species belonging to 92 genera and 24 families were identified in the study area. The most frequent species were in the Asteraceae (23 species) and Poaceae (16 species) families. The results showed that in all three elevational classes, therophytes were the dominant life form of the area. The frequency of the therophytes in the first altitude class was higher than in the other classes. The second predominant life form was hemicryptophytes, whose frequency in the third class was higher than the other classes. Other life forms observed in the region were cryptophytes and chamaephytes, respectively which made up the least proportion of the area’s plant population. In addition, the results indicated that within all of the elevational classes, a high percentage of the existing plants of the study area belonged to the Irano-Turanian floristic region. Generally, the altitude had a significant effect on the distribution of the flora of the study area.

<p><strong><em>Satureja kermanica</em></strong><strong> (Lamiaceae) a new species from south-east of Iran, inferred from molecular and morphological evidence</strong></p>

Traditional morphometric and multivariate analyses on relevant traits were carried out on populations identified as S. bachtiarica throughout the distribution range in Iran. This was complemented by molecular phylogenetic analysis of nuclear rDNA sequences (ITS). Based on these results the SE populations are described as a new species, Satureja kermanica sp. nov. The new taxon is illustrated and compared to its close relatives. The new species is distinguished from S. bachtiarica by several qualitative and quantitative characters: the length of internodes, the state of stem indumentum, the color of corolla, the shape and the length of calyx, the ratio of the length of lower to the length of upper calyx teeth, the ratio of calyx length to the lower teeth length, the length of stamens and the style. The new species is geographically isolated and restricted to the Irano-Turanian floristic region of Kerman Province. It preferably grows on the gravelly sediments of seasonal streams. Due to its restricted occurrence, the species is considered endangered (EN) according to IUCN criteria.

Morphological Innovations and Vast Extensions of Mountain Habitats Triggered Rapid Diversification Within the Species-Rich Irano-Turanian Genus Acantholimon (Plumbaginaceae).

The Irano-Turanian floristic region spans a topographically complex and climatically continental territory, which has served as a source of xerophytic taxa for neighboring regions and is represented by a high percent of endemics. Yet, a comprehensive picture of the abiotic and biotic factors that have driven diversification within this biota remains to be established due to the scarcity of phylogenetic studies. Acantholimon is an important component of the subalpine steppe flora of the Irano-Turanian region, containing c. 200 cushion-forming sub-shrubby pungent-leaved species. Our recent molecular phylogenetic study has led to enlarging the circumscription of this genus to include eight mono- or oligospecific genera lacking the characteristic life-form and leaves. Using the same molecular phylogeny, here we investigate the tempo and mode of diversification as well as the biogeographic patterns in this genus, to test the hypothesis that a combination of key morphological innovations and abiotic factors is behind Acantholimon high species diversity. Molecular dating analysis indicates that Acantholimon s.l. started to diversify between the Late Miocene and the Pliocene and the biogeographic analysis points to an Eastern Iran–Afghanistan origin. Macroevolutionary models support the hypothesis that the high diversity of the genus is explained by accelerated diversification rates in two clades associated with the appearance of morphological key innovations such as a cushion life-form and pungent leaves; this would have favored the colonization of water-stressed, substrate-poor mountainous habitats along the newly uplifted IT mountains during the Mio-Pliocene. Given the apparent similarity of mountain habitats for most species of Acantholimon, we hypothesize that its current high species diversity responds to a scenario of non-adaptive radiation fueled by allopatric speciation rather than evolutionary radiation driven by ecological opportunity. Similar scenarios might underlie the high diversity of other speciose genera in the topographically complex Irano-Turanian landscape, though this remains to be tested with fine-grained distribution and climatic data.

Visions of the past and dreams of the future in the Orient: the Irano-Turanian region from classical botany to evolutionary studies.

Ever since the 19th century, the immense arid lands of the Orient, now called the Irano-Turanian (IT) floristic region, attracted the interest of European naturalists with their tremendous plant biodiversity. Covering approximately 30% of the surface of Eurasia (16000000 km2 ), the IT region is one of the largest floristic regions of the world. The IT region represents one of the hotspots of evolutionary and biological diversity in the Old World, and serves as a source of xerophytic taxa for neighbouring regions. Moreover, it is the cradle of the numerous species domesticated in the Fertile Crescent. Over the last 200 years, naturalists outlined different borders for the IT region. Yet, the delimitation and evolutionary history of this area remain one of the least well-understood fields of global biogeography, even though it is crucial to explaining the distribution of life in Eurasia. No comprehensive review of the biogeographical delimitations nor of the role of geological and climatic changes in the evolution of the IT region is currently available. After considering the key role of floristic regions in biogeography, we review the history of evolving concepts about the borders and composition of the IT region over the past 200 years and outline a tentative circumscription for it. We also summarise current knowledge on the geological and climatic history of the IT region. We then use this knowledge to generate specific evolutionary hypotheses to explain how different geological, palaeoclimatic, and ecological factors contributed to range expansion and contraction, thus shaping patterns of speciation in the IT region over time and space. Both historical and ecological biogeography should be applied to understand better the floristic diversification of the region. This will ultimately require evolutionary comparative analyses based on integrative phylogenetic, geological, climatic, ecological, and species distribution studies on the region. Furthermore, an understanding of evolutionary and ecological processes will play a major role in regional planning for protecting biodiversity of the IT region in facing climatic change. With this review, we aim to introduce the IT floristic region to a broader audience of evolutionary, ecological and systematic biologists, thus promoting cutting-edge research on this area and raising awareness of this vast and diverse, yet understudied, part of the world.

Coumarin compounds of Biebersteinia multifida roots show potential anxiolytic effects in mice

BackgroundTraditional preparations of the root of Biebersteinia multifida DC (Geraniaceae), a native medicinal plant of Irano-Turanian floristic region, have been used for the treatment of phobias as anxiolytic herbal preparation.MethodsWe utilized the phobic behavior of mice in an elevated plus-maze as a model to evaluate the anxiolytic effect of the plant extract and bio-guided fractionation was applied to isolate the active compounds. Total root extract, alkaline and ether fraction were administered to mice at different doses 30 and 90 min prior to the maze test. Saline and diazepam were administered as negative and positive controls, respectively. The time spent in open and closed arms, an index of anxiety behavior and entry time, was measured as an index of animal activity.ResultsThe total root extract exhibited anxiolytic effect which was comparable to diazepam but with longer duration. This sustained effect of the crude extract was sustained for 90 min and was even more after injection of 45 mg/kg while the effect of diazepam had been reduced by 90 min. The anxiolytic effect factor was only present in the alkaline fraction and displayed its effect at lower doses than diazepam while pure vasicinone as the previously known alkaloid did not shown anxiolytic effect. The effect of the alkaline fraction was in a dose dependent manner starting at 0.2 mg/kg with a maximum at 1.0 mg/kg. Bio-guided fractionation using a variety of chromatographic methods led to isolation and purification of three coumarin derivatives from the bioactive fraction, including umbelliferone, scopoletin, and ferulic acid.ConclusionFor the first time, bio-guided fractionation of the root extract of B. multifida indicates significant sustained anxiolytic effects which led to isolation of three coumarin derivatives with well-known potent MAO inhibitory and anti-anxiety effects. These data contribute to evidence-based traditional use of B. multifida root for anxiety disorders.

Vegetation Patterns of the Irano-Turanian Steppe along a 3,000 m Altitudinal Gradient in the Alborz Mountains of Northern Iran

The Irano-Turanian floristic region is a major center of endemism in the Holarctic of Eurasia. The Alborz Mountains of northern Iran are a complex and heterogeneous environmental system with rich water resources and great habitat diversity. We have investigated steppe plant communities along an altitudinal gradient ranging from approximately 1,000 m a.s.l. in the semi-desert steppes near Tehran to a height of 3,966 m a.s.l. at the summit of Mount Tochal. Our two-way indicator species analysis of 1,069 vegetation samples resulted in classification of five major vegetation zones: (1) a semi-desert Artemisia steppe near Tehran, (2) a Stipa grassland in the alluvial undulating hills north and west of Tehran, (3) a submontane and steppe zone, (4) a subalpine cushion formation zone and (5) an alpine meadow and subnival zone of Mount Tochal. Annuals and ephemerals in the semi-desert vegetation decline as altitude increases and almost disappear in the alpine zone. Past human impacts of ancient Persian civilization and a traditional pastoral economy have affected the physiognomy of plant communities; thorny dwarf shrubs now dominate the treeless vegetation of the region. Lower competition for space, different phenology and the presence of edaphic and hydrological layers associated with anthropogenic impacts are major reasons for entanglement of different plant communities in the arid- and semi-arid steppe. The phytogeography of the region changes from omni-Irano-Turanian and Saharo-Sindian transgressive species at lower altitudes to a more limited range of western Irano-Turanian species and local endemics at higher altitudes.

Climatic determinism in phytogeographic regionalization: A test from the Irano-Turanian region, SW and Central Asia

This study investigates the role of climate in determining phytogeographic regions, focusing particularly on the Irano-Turanian floristic region in SW and Central Asia. A set of simple climatic variables and bioclimatic indices were used to prepare climate-space scatter plots and climate diagrams. The climate data were also subjected to multivariate analyses (PCA and Regression tree) in order to develop a bioclimatic characterization of the Irano-Turanian region in comparison with the adjacent Mediterranean, Saharo-Sindian, Euro-Siberian, and Central-Asiatic regions. Phytogeographic regions of SW and Central Asia display distinct bioclimatic spaces with small overlaps. The Irano-Turanian region is differentiated from surrounding regions by continentality, winter temperature, and precipitation seasonality. Continentality is the most important bioclimatic factor in differentiating it from the Mediterranean and Saharo-Sindian regions and is responsible for floristic differences among sub-regions of the Irano-Turanian region. In our case study, the Irano-Turanian region is a nearly independent bioclimatic unit, distinct from its surrounding regions. Hence, it is suggested that the term “Irano-Turanian bioclimate” be used to describe the climate of most of the continental Middle East and Central Asia. Among different sub-regions, the west-central part of this floristic region (“IT2 sub-region”) is a major center of speciation and endemism. Our case study demonstrates that climate is a primary determinant of phytogeographic regionalization. Although modern climate and topography are strong control parameters on the floristic composition and geographical delimitation of the Irano-Turanian region, the complex paleogeographic and paleoclimatic history of SW Asia has also influenced the Tertiary and Quaternary evolution of the Irano-Turanian flora, with additional impacts by the long-lasting historic and present land-use in this region. Many Irano-Turanian montane species are threatened by global warming, and particular conservation measures are needed to protect the Irano-Turanian flora in all sub-regions.

Germination strategies of some Allium species of the subgenus Melanocrommuyum from arid zone of Central Asia

Seed germination of six Allium species of subgenus Melanocrommyum was tested. The plants occur in the Irano-Turanian floristic region of Central Asia, characterized by hot dry summers, after seed maturation, and cold and snowy winters, when seeds lie in the wet soil. Germination was low in seeds wetted at 15°C, but various periods at 4°C promoted germination. Scarification reduced dormancy at 15°C but not at 4°C. The differing germination between two accessions of A. suworowii, may be related to after-ripening. The ecological background of the natural habitat, and seed harvest time, seem to play predominant roles in seed germinability.

Notes on the distribution, climate and flora of the sand deserts of Iran and Afghanistan

SynopsisAn account is given of the distribution of the sand deserts in Iran, Afghanistan and Pakistan Baluchistan, where they cover large surfaces on the plains at low and medium altitudes. Climatologically they differ considerably from each other with respect to winter temperatures, but the latitudinal sequence is obscured by elevation effects. About one half to one third of the species are strict psammophytes; structurally they are the most important components of the different plant communities and in mobile sands usually no other plants occur. Their phytogeographical and taxonomic relationships are discussed in detail and attempts made to relate the distributional patterns to certain ecological factors. 66% of the species are truly Irano-Turanian, 23% are endemics, mostly derivatives of Irano-Turanian species, 10% are Saharo-Arabian and 7% are biregionals. Further aspects pointed out are the representations of life forms of families and genera. The results in the deserts studied give support to the concept of a coherent Irano-Turanian floristic region. The southern deserts form a sub-unit of their own, characterised by high numbers of endemics, some intruding Saharo-Arabian species and an absence of several otherwise common Irano-Turanian species.