Xerophytic Taxa Research Articles

Population Genomics of Domesticated Cucurbita ficifolia Reveals a Recent Bottleneck and Low Gene Flow with Wild Relatives

Cucurbita ficifolia is a squash grown from Mexico to Bolivia. Its ancestor is unknown, but it has limited compatibility with wild xerophytic Cucurbita from Mexico’s highlands. We assembled the reference genome of C. ficifolia and assessed the genetic diversity and historical demography of the crop in Mexico with 2524 nuclear single nucleotide polymorphisms (SNPs). We also evaluated the gene flow between C. ficifolia and xerophytic taxa with 6292 nuclear and 440 plastome SNPs from 142 individuals sampled in 58 sites across their area of sympatry. Demographic modelling of C. ficifolia supports an eight-fold decrease in effective population size at about 2409 generations ago (95% CI = 464–12,393), whereas plastome SNPs support the expansion of maternal lineages ca. 1906–3635 years ago. Our results suggest a recent spread of C. ficifolia in Mexico, with high genetic diversity (π = 0.225, FST = 0.074) and inbreeding (FIS = 0.233). Coalescent models suggest low rates of gene flow with C. radicans and C. pedatifolia, whereas ABBA-BABA tests did not detect significant gene flow with wild taxa. Despite the ecogeographic proximity of C. ficifolia and its relatives, this crop persists as a highly isolated lineage of puzzling origin.

Diploid chastity vs. polyploid promiscuity – Extensive gene flow among polyploid cytotypes blurs genetic, morphological and taxonomic boundaries among Dinaric taxa of Knautia (Caprifoliaceae)

Heteroploid Knautia sect. Trichera constitutes a taxonomically intricate assemblage of taxa with highly complex genetic architecture, which is mirrored in high morphological variability and blurred boundaries among the species. Here, we aim to disentangle the relationships among the xerophytic taxa from the Dinaric Mountains on the western Balkan Peninsula, which, based on relative genome size estimations, comprise di-, tetra- and hexaploid populations. Our analyses of amplified fragment length polymorphisms (AFLP) revealed a clear genetic differentiation among the diploid members, which are also morphologically clearly divergent. On the other hand, the phylogenetic structure among tetraploid and hexaploid populations as well as the ties with their diploid progenitors are complex, conferring unclear boundaries among species. Tetraploids were intermingled among the divergent diploid lineages, suggesting recurrent polyploidisation and/or extensive gene flow across sympatric lineages, whereas hexaploids clustered in two groups, pointing to two separate origins. In line with the genetic pattern, there is a high overlap in morphological characters across and within different ploidies. Nevertheless, comparisons of environmental niches showed differentiation among the ploidy levels, with the niche of hexaploids being most divergent. It is thus obvious that dynamic polyploid evolution, virtual lack of crossing barriers among polyploid cytotypes pertaining to different species, and exceedingly variable morphology along with the uniformity of reproductive characters preclude establishing a clear-cut taxonomic structure. Still, albeit generally corroborating previous observations for K. sect. Trichera as a whole, our study restricted to a limited geographic and taxonomic assemblage yielded constructive insights towards a workable taxonomic framework in this complex system. As a result, we propose a revised taxonomic treatment, including description of a new species, Knautia ehrendorferi, but we are aware that species identifications will remain challenging also in the future. Data availabilityData will be made available on request.

Reconstruction of early Paleogene landscapes and climate in the Jianghan Basin, central China: Evidence from evaporites and palynology

The early Paleogene environment and climate of East Asia are poorly understood. To improve knowledge, we investigated the palynological record of well ZK0303 in the southwest Jianghan Basin, Hubei Province (central China). The well lithology comprises three intervals whose lithofacies represent the deposits of a saline lake: anhydrite/silty mudstone, halite/mudstone, and dolomite/siltstone. Based on a study of 37 palynological samples, three assemblages were recognized. Assemblage A, which correlates with Paleocene, is dominated by Ephedripites and contains a high proportion of thermophilic and xerophytic taxa. Assemblage B, which correlates with the early Eocene, is dominated by Taxodiaceaepollenites and hygrophilous taxa while the proportion of xerophytes is generally low. Assemblage C, probably early Eocene too, is dominated by Ephedripites and contains higher numbers of xerophytic species while hygrophilous species decrease to nearly half of their earlier abundances. These palynological data show that the early Paleogene climate of the Jianghan Basin experienced a transition from hot and arid to warm and humid conditions, with the latter period interrupted by short arid intervals. Afterwards, hot-arid conditions prevailed again. The reconstructed desert shrub and mountain forest vegetation suggests that the regional Paleocene landscape resulted from basin and range tectonics. Under the influence of a hot and arid climate controlled by global circulation patterns and rain-shadow effects, desert landscape and evaporites were formed in central China during the early Paleogene, whilst humid climate and forest vegetation prevailed in central China under the influence of the Paleocene-Eocene Thermal Maximum (PETM).

Macroflora of the Krkonoše-Piedmont Basin (Pennsylvanian–early Permian); Bohemian Massif, Czech Republic

The Krkonoše-Piedmont Basin is one of several land-locked post-collisional Variscan basins of the Bohemian Massif. The fossil record of the basin is evaluated, based on published data and unpublished lists of floras collected in borehole cores and during mapping. The occurrence ranges of plant taxa are plotted against radioisotopically calibrated lithostratigraphic units. The compiled dataset is used to evaluate species richness and vegetation patterns throughout Late Pennsylvanian and Asselian times. The species richness of particular intervals has been affected by taphonomic and sampling biases of varying intensities. Coal-bearing strata and grey lacustrine intervals represent well-documented fossil-rich taphonomic windows with 20–45 species. In contrast, red beds are fossil-poor and under-sampled, typically providing only a few species. It is assumed that coal-bearing and grey lacustrine intervals represent periods of increased climatic humidity, during which wetlands covered extensive areas of basinal lowlands or shallows and coastal areas of meromictic lakes. Most habitats were colonised by hygrophytes and mesophytes. However, sparse conifer shoots found in association with wetland taxa indicate seasonality to a sufficient degree that xerophytic taxa were able to get close to sites of deposition and wetland habitats. During the deposition of red beds, wetlands may have almost completely disappeared, resulting in the basinal landscape being colonised by gymnosperm-dominated forests of walchian conifers with co-dominant cordaitaleans. Wetland assemblages of low diversity and small populations may have survived in the basin, although many species may have disappeared from the basin, having dispersed elsewhere to habitats where their survival was possible. In the late Middle Pennsylvanian and early Upper Pennsylvanian, such habitats existed in the Intra-Sudetic Basin farther east, and in other basins located in western and central parts of the Bohemian Massif. These climatically-driven oscillations in vegetation patterns, which occurred on scales of hundreds of thousands to a million years, were superimposed on a long-term drying trend marked by an increase in gymnosperms in the species pool, as well as an abundance of their remains in the fossil record, at the expense of free-sporing plants. Among the gymnosperms, there was a gradual drop in the diversity and abundance of medullosalean pteridosperms and a concomitant rise of peltasperms and conifers.

Astronomical forcing of vegetation and climate change during the Late Pliocene–Early Pleistocene of the Nihewan Basin, North China

The Late Pliocene–Early Pleistocene is an important transitional period in the Cenozoic evolution of global climate and environment. Previously, we demonstrated the occurrence of distinct cycles in vegetation and climate in the Nihewan Basin, during 2.89–1.78 Ma. However, the specific cycles and their forcing mechanisms were not studied more in-depth. Here we present the results of wavelet and spectral analyses of pollen percentages (Picea, Pinus, xerophytic taxa and broadleaved trees), macro-charcoal concentration, clay % and sand %, and magnetic susceptibility of 340 samples from the NHA drill core in the Nihewan Basin, during 2.89–1.78 Ma. The results reveal dominant ~20-kyr and ~40-kyr cyclicities: the pollen percentages of Pinus and broadleaved trees, magnetic susceptibility, and clay %, indicating a warm and humid climate, are more significantly influenced by ~20-kyr; in contrast, the percentages of Picea and xerophytic taxa, macro-charcoal concentration, and sand %, associated with a cold and dry climate, are mainly influenced by ~40-kyr. The ~20-kyr and ~40-kyr cycles corresponding to the dominant cycles of the East Asian summer monsoon and winter monsoon, which are respectively driven by Earth orbital precession and tilt, indicating that vegetation and climate change in the Nihewan Basin during 2.89–1.78 Ma was forced by a combination of low- and high-latitude processes. Otherwise, most of the proxy indexes also show a pronounced ~100-kyr cycle, which may be a response to changes in Northern Hemisphere ice sheets, emphasizing the importance of high-latitude forcing of vegetation and climate change in the Nihewan Basin.

Centennial-scale vegetation and North Atlantic Oscillation changes during the Late Holocene in the southern Iberia

High-reso CE to lution pollen analysis, charcoal, non-pollen palynomorphs and magnetic susceptibility have been analyzed in the sediment record of a peat bog in Sierra Nevada in southern Iberia. The study of these proxies provided the reconstruction of vegetation, climate, fire and human activity of the last ∼4500 cal yr BP. A progressive trend towards aridification during the late Holocene is observed in this record. This trend is interrupted by millennial- and centennial-scale variability of relatively more humid and arid periods. Arid conditions are recorded between ∼4000 and 3100 cal yr BP, being characterized by a decline in arboreal pollen and with a spike in magnetic susceptibility. This is followed by a relatively humid period from ∼3100 to 1600 cal yr BP, coinciding partially with the Iberian-Roman Humid Period, and is indicated by the increase of Pinus and the decrease in xerophytic taxa. The last 1500 cal yr BP are characterized by several centennial-scale climatic oscillations. Generally arid conditions from ∼450 to 1300 CE, depicted by a decrease in Pinus and an increase in Artemisia, comprise the Dark Ages and the Medieval Climate Anomaly. Since ∼ 1300 to 1850 CE pronounced oscillations occur between relatively humid and arid conditions. Four periods depicted by relatively higher Pinus coinciding with the beginning and end of the Little Ice Age are interrupted by three arid events characterized by an increase in Artemisia. These alternating arid and humid shifts could be explained by centennial-scale changes in the North Atlantic Oscillation and solar activity.

A small Remarkable Bryophyte Collection from the Ibb Province (Yemen), with Eleven New Records for the Bryoflora of Yemen

Based on a recent small bryophyte collection from the western escarpment mountains of Yemen in the vicinity of Ibb (Ibb Governorate), 36 mosses are reported, among them 11 new to the bryoflora of the country. Gemmabryum nanoapiculatum (Ochi & Kürschner) Kürschner comb. nov. is collected for the first time since the type collection. Beside some hygrophytic taxa, growing in the vicinty of water pools and runnels, most of the recorded species belong to drought adapted, xerophytic taxa and fit into the expected bryophyte spectrum for the Arabian Peninsula. Together with pantropical and Afromontane species they indicate a common floral history and past and present migration routes.

Modern vegetation–pollen–climate relationships for the Pampa grasslands of Argentina

AbstractAim To analyse the relationships between potential natural vegetation, pollen and climate in order to improve the interpretation of fossil pollen records and provide the background for future quantitative palaeoclimatic reconstructions.Location Pampa grasslands of Argentina, between 33–41° S and 56–67° W.Methods Modern pollen data were obtained from a pollen data base developed by the Grupo de Investigación de Paleoecología y Palinología, Universidad Nacional de Mar del Plata, Argentina (143 surface samples and 17 pollen types). Analysis of pollen and climate data involved multivariate statistics (cluster analysis and principal components analysis), scatter diagrams, Pearson’s correlation and isopoll mapping.Results Vegetation patterns at regional scales (grasslands and xerophytic woodlands) and local scales (edaphic communities) were identified by cluster analysis of pollen surface samples. The main climatic variables that appear to constrain the vegetation distribution and abundance of taxa are mean annual precipitation, annual effective precipitation and summer temperature. Individual pollen types such as Chenopodiaceae, Apiaceae, Cyperaceae, Prosopis, Schinus, Condalia microphylla and other xerophytic taxa are good indicators of moisture regime. Many pollen types are significantly correlated with summer temperature. The modern vegetation–pollen–climate relationships vary in a broadly predictable manner, supporting the contention that fossil pollen assemblages can be related to particular climatic characteristics.Main conclusions An expanded suite of modern analogues facilitated new insights into vegetation–pollen–climate relationships at the regional scale in Pampa grasslands. Relationships between individual pollen types and climate are appraised at a regional scale and new modern analogues are presented. The results provide the basis for improved vegetation and climate reconstruction from fossil records of the study area.

Systematic analysis of Dendrobium Swartz section Dendrocoryne in the Australian region

Dendrobium sect. Dendrocoryne is a difficult taxonomic group of allied species and species complexes, occurring on the eastern Australian coastline, Lord Howe Island and New Caledonia. Significant morphological characters were assessed from all key areas of the distribution range. Patterns of variation between species, varieties and hybrids were investigated by principal coordinate analysis. The analyses affirm 12 species in the sect. Dendrocoryne described by Schlechter (1912, 1982) and Dockrill (1969, 1992), including a cluster of small statured D. gracilicaule, D. adae, D. fleckeri, and D. finniganense, and three variable species complexes – D. speciosum, D. kingianum and D. tetragonum. Recently described D. finniganense and D. callitrophilum are interpreted as members of the section. Phylogenetic relationships are presented based on parsimony analysis of 31 morphological characters. Analyses do not support proposals to recognize new genera for D. tetragonum, D. callitrophilum and D. aemulum, or to create new species within D. tetragonum, D. jonesii, D. speciosum and D. kingianum. The phylogeny indicates that rainforest taxa are earlier lineages and xerophytic taxa are more derived.

A modern pollen rain study from the central Andes region of South America

AbstractAim To provide a greater understanding of the modern pollen rain for the central Andes region of South America, thus laying the groundwork for future pollen studies and the derivation of pollen‐climate transfer functions and response surfaces.Location Peru, Bolivia and Chile.Methods Standard palynological techniques for surface soil sampling and discriminant analysis.Results Statistical analysis of the 40 surface samples revealed four palynologically distinct assemblages: (1) the Yungas on the eastern slopes of the Andes; (2) the puna grasslands of the Altiplano; (3) the Coastal Deserts to the west of the Andes; and (4) the Southern Bolivian Highlands.Main conclusions The Yungas group is characterized by high percentages of Urticaceae/Moraceae pollen and fern spores along with trace amounts of pollen from common zoophilous lowland taxa such as Piperaceae, Bignoniaceae and Malpighiaceae. The puna assemblage of the Altiplano is characterized by the dominance of grass (Poaceae) in combination with moderate frequencies of Asteraceae pollen, which tend to increase slightly towards the southern (drier) locations of the Altiplano. Lower percentages of grass pollen and the greater prevalence of Asteraceae, Solanaceae, and the Chenopodiaceae/Amaranthaceae families define the coastal deserts to the west of the Andes. Samples taken from the Southern Bolivian Highlands are characterized by the dominance of Solanaceae in the area, in combination with the pollen of other xerophytic taxa.

Leaf surface and anatomy in Boraginaceae tribe Boragineae with respect to ecology and taxonomy

Summary The main anatomical and surface characters of the leaves of 54 specific and subspecific taxa belonging to 14 Boraginaceae genera of tribe Boragineae were analysed and compared by means of light and scanning electron microscopy. Characters concerning the vascular system appeared essentially uniform, while stomata size and density, structure of individual trichomes, type of indumentum, leaf and epidermis thickness and palisade arrangement were variable in the examined taxa. This variation was discussed in relation to the morphological and ecological diversification exhibited by the members of the tribe. Most species had typical dorsiventral leaves, but some showed an incipient isobilateral symmetry with a layer of abaxial palisade tissue. Thickness of the lamina and of the outer wall of the adaxial epidermal cells were higher in the xerophytic taxa, especially in the psammophytic species of Anchusa . The mesophytic genera Brunnera, Pentaglottis, Trachystemon and, partly, Symphytum had typical hypostomatous leaves, while the xerophytic and psammophytic species were characterized by increased stomatal density on the adaxial surface. This was higher in the taxa with thicker leaves. Abaxial stomatal density and size were inversely correlated. Mesophytic species had more densely spaced and smaller stomata than the xerophytic species. Finally, size of the abaxial stomata was higher in the taxa showing a thicker outer wall of the adaxial epidermal cells. Seven types of trichomes were recognized, five of which were eglandular and two glandular. Some of these types were systematically useful (exclusive to one or two genera) e.g., the hooked hairs of Symphytum and the lithocysts of Trachystemon and Brunnera . Energy dispersive X-ray microanalysis (EDX) showed that silica and calcium are the most abundant elements in the mineral deposits of the trichome cells. No strict correlation occurred between surface elements, trichome structure, edaphic requirements and systematic position of the 14 examined taxa, although the presence of small amounts of sulphur and phosphorus in Nonea and a remarkable abundance of Potassium in Nonea pulla and Pulmonaria picta could have systematic relevance.

Late Quaternary diatom response to vegetation and climate change in a subalpine lake in Banff National Park, Alberta

The late Quaternary diatom record from subalpine Crowfoot Lake, Banff National Park, Alberta (lat. 51° 61′N; long. 116° 31′W) has been analyzed. Results are related to independently inferred vegetation and climate changes. No diatoms were found in the basal diamict that predates 11330 14C yr BP. Very few occur until ca. 10 10014 C yr BP probably due to the short time between de-glaciation and an advance of the Crowfoot Glacier during the ‘Younger Dryas Chron’. Initial pioneering species were characteristic of alkaline water and calcareous organic sediments. They appeared as sediments became organic and laminated suggesting increasing water clarity, and as the Pinus-dominated forest expanded and the climate warmed. After ca. 9060 14C yr BP diatom numbers increased rapidly, reaching a maximum prior to the Mazama tephra; they remained high until ca. 3500 14C yr BP. The period between ca. 9060 and 3500 14C yr saw timberline elevation increase and the dominance of xerophytic taxa. These are consistent with early to mid-Holocene warmth and aridity. Diatom productivity reflects the warm climate and presumably longer ice-free season, a stable catchment and transparent water. Decreases in diatom productivity coincide with a vegetation change with reduction of xerophytic taxa and the appearance of a closed Picea-Abies forest, hence a cooler, wetter climate at ca. 4100 to 3500 14C yr BP. The diatom numbers during the Neoglacial were of the same magnitude as prior to ca. 9060 14C yr BP. Small species of Fragilaria (overwhelmingly Fragilaria construens v. venter) became extremely dominant during the period of high diatom productivity, and remained so thereafter. Recovery of the lake appears to have been rapid after deposition of the Mazama tephra. Maximum occurrence of Cyclotella radiosa occurred ca. 8000 14C yr BP during the warm early Holocene and may reflect this warmer climate, a longer ice-free season than presently, perhaps less turbid water, or it may reflect a subtly higher nutrient status of the lake water. The diatom record of Crowfoot Lake has responded with sensitivity, particularly in terms of productivity, to the Holocene vegetation and climate changes.

A New Species of Thalictrum (Ranunculaceae) from Western Colorado

A new species,Thalictrum heliophilum, from exposed, shale talus of the Green River Formation in western Colorado where it is associated with a number of xerophytic taxa, is described. It differs from the commonT. fendleri by its shorter stature, relatively small, coriaceous, glaucous leaves, and pistillate flowers with 4 or 5 (6) pistils.

Bryophytes New to New Mexico

Eighteen bryophytes, including Bryum pyriferum Crundw. & Whiteh. new to North America, are added to the flora of New Mexico. Recent collecting in the southern and central parts of the state adds 15 mosses and one liverwort to the bryoflora, while herbarium studies and an overlooked literature report account for the other two additions. Recent studies on the bryoflora of New Mexico have revealed 18 taxa new to the state, including one species new to North America. Collecting in the central (Torrance County) and the southern (Dona Ana and Sierra counties) parts of the state in 1979-80 by Talbot and Todsen resulted in 15 additions to the list of mosses by Mahler (1978) and one addition to the liverworts reported by Shields (1954) and Bird (1960). Much of the collecting was done in the White Sands Missile Range in eastern Dona Ana and Sierra counties, where few botanists have collected since the range was established. While the moss collections were being identified, a specimen of Grimmia rauii that is new to New Mexico was discovered in CANM. It also was found that a New Mexico collection of Plagiothecium denticulatum reported by Ireland (1969) had been omitted from Mahler's (1978) list. All specimens from the 1979-80 season were collected in calcareous habitats except Neckera pennata var. tenera (granitic), Phascum cuspidatum (granitic), Tortella humilis (epiphytic, T8003-44), and Tortula obtusissima (epiphytic, T8005-25; granitic, T8002-3, T8003-26, T8004-4). Collections were made within a variety of plant communities and included: ponderosa pine forest of Manzano Mountains; oak-pine woodland of Salinas Peak; juniper-pinyon woodland of Salinas Peak; Fraxinus velutina canyon, Ash Canyon, and creosote bush-grassland in the Shalam Hills. The bryoflora of New Mexico is thus far known to be similar to that of adjacent Arizona (Haring 1961) as one might suspect. The aridity of both states is reflected by the occurrence of a high number of xerophytic taxa, which are characteristic of the American Southwest. However, much more collecting needs to be done in New Mexico. The list of mosses known from the state now contains 189 taxa, including those reported here, compared to almost twice that number reported for Arizona. The mosses were identified by the senior author, and the liverwort by Linda Ley. The nomenclature of the Hepaticae is basically that of Stotler and Crandall-Stotler (1977) and the Musci is that of Crum et al. (1973). Voucher specimens are deposited in duplicate in CANM and the private herbarium of Talbot.