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Leaf morphology and anatomy of Schlechtendalia luzulifolia, abasal member of subfamily Barnadesioideae (Asteraceae)
Abstract
Based on molecular phylogenetic studies, Barnadesioideae have been proposed to be the basal subfamily of Asteraceae. This is a complex of
10 genera and 87 species distributed primarily along the Andean mountains, Patagonia, and into southern Brazil and Uruguay. Phylogenetic
analyses have recovered all genera as monophyletic groups and have provided insights to their inter-relationships. Four generic clades have
been substantiated: (1) Chuquiraga, Doniophyton, and Duseniella; (2) Dasyphyllum; (3) Barnadesia and Huarpea; and (4) Archidasyphyllum,
Arnaldoa, and Fulcaldea. The remaining genus, the monospecific Schlechtendalia, has been an outlier in the subfamily, with some previous
analyses recovering it as basal for the entire subfamily, and others showing it as sister to Barnadesia and Huarpea (with weak support) as
well as to other genera. Recent massive sampling of loci has confirmed Schlechtendalia as the sister genus for the subfamily. Schlechtendalia
luzulifolia has morphology atypical for Asteraceae. The capitula are loose aggregations of florets, and the leaves are long and strap shaped,
more reminiscent of monocots. Morphological and anatomical investigations of the leaves reveal long, laminar blades with parallelodromous
vascularization. The vesture is often with ‘barnadesioid trichomes’, especially towards the base of the plant, plus additional uniseriate trichomes consisting of 3 to many cells, newly reported for the subfamily. Some glandular trichomes with 2-4 short cells also occur. The transverse
anatomy of the leaves reveals a single epidermal layer on both surfaces, which also contain the stomata (the leaf being amphistomatic). The
mesophyll is undifferentiated; the vascular traces are surrounded by sclerenchyma that not only encircles the traces but also extends towards
the epidermis and connects with it. The morphology and anatomy of the leaves of Schlechtendalia are divergent in comparison with other
genera of the subfamily. Chuquiraga, Doniophyton, and Huarpea have leaf adaptations for survival in xeric habitats, such as dense pubescence,
grey surfaces, and revolute margins. Schlechtendalia, in contrast, is adapted to a more mesic environment, especially near the Atlantic Ocean
and along the Uruguay and La Plata rivers. The leaves are oriented upright, which correlates with undifferentiated mesophyll and stomata
on both epidermal layers. The stem is an underground rhizome, an adaptation that permits survival during seasonal drought in the austral
summer in Uruguay and adjacent regions. It is hypothesized that Schlechtendalia may have become adapted to more mesic environments in
the Miocene prior to the rise of the Andes and development of the modern arid environments, into which many of the other genera of the
subfamily subsequently radiated.
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With c. 24 700 species (10% of all flowering plants), Asteraceae are one of the largest and most phenotypically diverse angiosperm families, with considerable economic and ecological importance. Asteraceae are distributed worldwide, from nearly polar latitudes all the way to the tropics, and occur across a diverse range of habitats from extreme deserts to swamps and from lowland rainforests to alpine tundra. Altogether, these characteristics make this family an outstanding model system to address a broad range of eco-evolutionary questions. In this review, we summarize recent progress in our understanding of Asteraceae on the basis of joint efforts by specialists in the fields of palaeobotany, cytogenetics, comparative genomics and phylogenomics. We will highlight how these developments are opening up new possibilities for integrating fields and better comprehending evolution beyond Asteraceae.
Target sequence capture has emerged as a powerful method to sequence hundreds or thousands of genomic regions in a cost- and time-efficient approach. In most cases, however, targeted regions lack full sequence information for certain samples, due to taxonomic, laboratory, or stochastic factors. Loci lacking molecular data for a large number of samples are commonly excluded from downstream analyses, even though they may still contain valuable information. On the other hand, including data-poor loci may bias phylogenetic analyses. Here we use a target sequence capture dataset of an ecologically and taxonomically diverse group of spiny sunflowers (Asteraceae, or Compositae: Barnadesioideae) to test how the inclusion or exclusion of such data-poor loci affects phylogenetic inference. We investigate the sensitivity of concatenation and coalescent approaches to missing data with matrices of varying taxonomic completeness by filtering loci with different proportions of missing samples prior to data analysis. We find that missing data affect both the topology and branch support of the resulting phylogenies. The matrix containing all loci yielded the overall highest node support values, independently of the amount of missing nucleotides. These results provide empirical support to earlier suggestions based on single genes and data simulations that taxa with high amounts of missing data should not be readily dismissed as they can provide essential information for phylogenomic reconstruction.
The subfamily Barnadesioideae (Compositae) is endemic to South America, comprising 10 genera and 80 species of mostly spiny herbs, subshrubs, shrubs, trees, or woody vines distributed from Venezuela to Argentina. Three genera, Dasyphyllum(27 species), Chuquiraga (22 spp.) and Barnadesia (19 spp.) contain 85% of the species, while the other seven genera (Archidasyphyllum, Arnaldoa, Doniophyton, Duseniella, Fulcaldea, Huarpea, and Schlechtendalia) are represented by up to three species each. Most species are found in xeric areas in the Andean and Patagonian regions—as in the Páramos, Puna and Patagonian steppe vegetation—with a secondary center of diversity in eastern South America. Previous phylogenetic hypotheses have clarified the relationships within the subfamily, showing that there are many non-monophyletic groups in different taxonomic ranks. As a result, taxonomic changes have been proposed over recent decades in order to reflect classifications comprising only monophyletic groups. In the present study, we provide a generic synopsis of the subfamily Barnadesioideae based on the most recent generic circumscriptions, including a key, expanded morphological descriptions, information on geographical distribution and habitat, photographs and taxonomic notes for all genera.
Calyceraceae is a small South American family sister to Asteraceae. Previous phylogenetic analyses revealed that Calyceraceae genera are para‐ or polyphyletic. Fruit and inflorescence characters used historically as diagnostic in Calyceraceae taxonomy have proven unreliable in defining natural groups. Surprisingly, flower morphology does not appear in diagnoses of Calyceraceae genera, and its diversity and evolution has remained unstudied before now. Based on phylogenetic analyses using six molecular markers and an almost complete sampling of the family (43 of 46 species), we propose a taxonomic re‐arrangement of Calyceraceae. In the search for diagnostic morphological characters, we studied flower structure diversity and optimized 12 discrete characters by maximum parsimony and maximum likelihood to reconstruct floral evolution in the family. Calyceraceae species are arranged in eight genera (three monotypic, five with 6 to 13 species). Two genera are new (Anachoretes, Asynthema), one is reinstated (Leucocera), with the remaining five emended (Acicarpha, Boopis, Calycera, Gamocarpha, Moschopsis). Flower morphology is notably diverse but provides only a few diagnostic features. Many floral attributes likely reflect selection for pollination or fruit dispersal rather than phylogenetic affinity. In the context of this taxonomic revision, we include a key to genera, new and emended diagnoses, and new combinations.
Biodiversity is not evenly distributed among related groups, raising questions about the factors contributing to such disparities. The sunflower family (Asteraceae, >26,000 species) is among the largest and most diverse plant families, but its species diversity is concentrated in a few subfamilies, providing an opportunity to study the factors affecting biodiversity. Phylotranscriptomic analyses here of 244 transcriptomes and genomes produced a phylogeny with strong support for the monophyly of Asteraceae and the monophyly of most subfamilies and tribes. This phylogeny provides a reference for detecting changes in diversification rates and possible factors affecting Asteraceae diversity, which include global climate shifts, whole‐genome duplications (WGDs), and morphological evolution. The origin of Asteraceae was estimated at ~83 Mya, with most subfamilies having diverged before the Cretaceous–Paleocene boundary. Phylotranscriptomic analyses supported the existence of 41 WGDs in Asteraceae. Changes to herbaceousness and capitulescence with multiple flower‐like capitula, often with distinct florets and scaly pappus/receptacular bracts, are associated with multiple upshifts in diversification rate. WGDs might have contributed to the survival of early Asteraceae by providing new genetic materials to support morphological transitions. The resulting competitive advantage for adapting to different niches would have increased biodiversity in Asteraceae.
The sunflower family, Asteraceae, comprises 10% of all flowering plant species and displays an incredible diversity of form. Asteraceae are clearly monophyletic, yet resolving phylogenetic relationships within the family has proven difficult, hindering our ability to understand its origin and diversification. Recent molecular clock dating has suggested a Cretaceous origin, but the lack of deep sampling of many genes and representative taxa from across the family has impeded the resolution of migration routes and diversifications that led to its global distribution and tremendous diversity. Here we use genomic data from 256 terminals to estimate evolutionary relationships, timing of diversification(s), and biogeographic patterns. Our study places the origin of Asteraceae at ∼83 MYA in the late Cretaceous and reveals that the family underwent a series of explosive radiations during the Eocene which were accompanied by accelerations in diversification rates. The lineages that gave rise to nearly 95% of extant species originated and began diversifying during the middle Eocene, coincident with the ensuing marked cooling during this period. Phylogenetic and biogeographic analyses support a South American origin of the family with subsequent dispersals into North America and then to Asia and Africa, later followed by multiple worldwide dispersals in many directions. The rapid mid-Eocene diversification is aligned with the biogeographic range shift to Africa where many of the modern-day tribes appear to have originated. Our robust phylogeny provides a framework for future studies aimed at understanding the role of the macroevolutionary patterns and processes that generated the enormous species diversity of Asteraceae.
Dasyphyllum Kunth is the most diverse genus of the South American subfamily Barnadesioideae (Asteraceae), comprising 33 species that occur in tropical Andes, Atlantic Forest, Caatinga, Cerrado, and Chaco. Based on distribution, variation in anther apical appendages, and leaf venation pattern, it has traditionally been divided into two subgenera, namely, Archidasyphyllum and Dasyphyllum. Further, based on involucre size and capitula arrangement, two sections have been recognized within subgenus Dasyphyllum: Macrocephala and Microcephala (=Dasyphyllum). Here, we report a phylogenetic analysis performed to test the monophyly of Dasyphyllum and its infrageneric classification based on molecular data from three non-coding regions (trnL-trnF, psbA-trnH, and ITS), using a broad taxonomic sampling of Dasyphyllum and representatives of all nine genera of Barnadesioideae. Moreover, we used a phylogenetic framework to investigate the evolution of the morphological characters traditionally used to recognize its infrageneric groups. Our results show that neither Dasyphyllum nor its infrageneric classification are currently monophyletic. Based on phylogenetic, morphological, and biogeographical evidence, we propose a new circumscription for Dasyphyllum, elevating subgenus Archidasyphyllum to generic rank and doing away with the infrageneric classification. Ancestral states reconstruction shows that the ancestor of Dasyphyllum probably had acrodromous leaf venation, bifid anther apical appendages, involucres up to 18 mm in length, and capitula arranged in synflorescence.
Palaeoclimate reconstructions of periods with warm climates and high atmospheric CO2 concentrations are crucial for developing better projections of future climate change. Deep-ocean1,2 and high-latitude³ palaeotemperature proxies demonstrate that the Eocene epoch (56 to 34 million years ago) encompasses the warmest interval of the past 66 million years, followed by cooling towards the eventual establishment of ice caps on Antarctica. Eocene polar warmth is well established, so the main obstacle in quantifying the evolution of key climate parameters, such as global average temperature change and its polar amplification, is the lack of continuous high-quality tropical temperature reconstructions. Here we present a continuous Eocene equatorial sea surface temperature record, based on biomarker palaeothermometry applied on Atlantic Ocean sediments. We combine this record with the sparse existing data4, 5–6 to construct a 26-million-year multi-proxy, multi-site stack of Eocene tropical climate evolution. We find that tropical and deep-ocean temperatures changed in parallel, under the influence of both long-term climate trends and short-lived events. This is consistent with the hypothesis that greenhouse gas forcing7,8, rather than changes in ocean circulation9,10, was the main driver of Eocene climate. Moreover, we observe a strong linear relationship between tropical and deep-ocean temperatures, which implies a constant polar amplification factor throughout the generally ice-free Eocene. Quantitative comparison with fully coupled climate model simulations indicates that global average temperatures were about 29, 26, 23 and 19 degrees Celsius in the early, early middle, late middle and late Eocene, respectively, compared to the preindustrial temperature of 14.4 degrees Celsius. Finally, combining proxy- and model-based temperature estimates with available CO2 reconstructions⁸ yields estimates of an Eocene Earth system sensitivity of 0.9 to 2.3 kelvin per watt per square metre at 68 per cent probability, consistent with the high end of previous estimates¹¹.
Premise of the study:
Leaves of monocots are typically linear with parallel venation, though a few taxa have broad leaves. Studies of stomatal patterning and development in monocots required updating in the context of rapidly improving knowledge of both the phylogenetic and development-genetic context of monocots that facilitate studies of character evolution.
Methods:
We used an existing microscope-slide collection to obtain data on stomatal structure across all the major monocot clades, including some species with relatively broad leaves. In addition, we used both light and electron microscopy to study stomatal development in 16 selected species. We evaluated these data in a phylogenetic context to assess stomatal character evolution.
Key results:
Mature stomatal patterning in monocots can be broadly categorized as anomocytic, paracytic-nonoblique, and paracytic/tetracytic oblique, depending on the presence, development, and arrangement of lateral subsidiary cells. Stomatal meristemoids invariably result from an asymmetric mitosis in monocots. In species where lateral subsidiary cells are present, they are perigene cells. Among monocots with relatively broad leaves, stomatal orientation is linear-axial in most taxa, but transverse in Lapageria and Stemona, and random in Dioscorea and some Araceae. Amplifying divisions are apparently absent in monocots.
Conclusions:
Anomocytic stomata represent the likely ancestral (plesiomorphic) condition in monocots, though multiple evolutionary transitions and reversals have occurred. Paracytic-nonoblique stomata with highly modified perigene lateral neighbor cells characterize grasses and other Poales. The presence of anomocytic stomata in Japonolirion and Tofieldia reinforces the concept that these two genera have retained many ancestral monocot features and are critical in understanding character evolution in monocots.
Calyceraceae is a small family with six traditionally recognized genera and 47 species from southern South America. Most species grow along the Andes (of both Argentina and Chile) and in arid regions of the Patagonian steppe. This family belongs to the well-supported MGCA clade within Asterales, which includes Menyanthaceae + Goodeniaceae + Calyceraceae + Asteraceae. Calyceraceae is monophyletic and sister to Asteraceae, one of the five largest families of angiosperms. Although Calyceraceae is clearly distinct as a family, its genera are not, and taxonomic revisionary effort has confirmed the lack of sharp boundaries among genera. We performed a phylogenetic analysis of Calyceraceae with a broad taxon sampling (41 of 47 species), and with sequence data from multiple regions from the nuclear (ITS) and plastid genomes (ycg6-psbM, psbM-trnD, trnS-trnG, trnH-psbA, trnD-trnT) using maximum parsimony and Bayesian approaches. We aimed at identifying monophylectic groups, their putative morphological synapomorphies and their geographical distribution; we also estimated divergence times and examined chromosomes numbers in an evolutionary context. We obtained well-resolved and strongly supported phylogenies that show Calyceraceae to be divided into two major clades with geographically structured subclades within each. Our results indicate that an early split within Calyceraceae occurred about 27.4 Ma, probably related to differential changes in chromosome numbers, which allowed the two lineages to evolve in sympatry. We found that major natural subgroups diverged 15–12 Ma, following the Early-Miocene South Andes construction stage. Finally, the diversification of the extant species is probably associated to Andean orogeny and climate changes in the last 5–4 Myr. We recovered Acicarpha as monophyletic, while the remaining traditionally recognized genera of Calyceraceae are para- or polyphyletic. Most species of Moschopis are included in the Glutinose group, but M. monocephala is more closely related to some Calycera species. Calycera is divided into two clades: the Calycera group and the Pilose group. All species of Nastanthus are placed in a well-supported main group with species of Gamocarpha and Boopis. Gamocarpha could be monophyletic after exclusion of G. dentata and G. angustifolia, but is nested within Nastanthus and Boopis species. Boopis is clearly polyphyletic with its species distributed in all main groups.
Chromosome number changes during the evolution of angiosperms are likely to have played a major role in speciation. Their study is of utmost importance, especially now, as a probabilistic model is available to study chromosome evolution within a phylogenetic framework. In the present study, likelihood models of chromosome number evolution were fitted to the largest family of flowering plants, the Asteraceae. Specifically, a phylogenetic supertree of this family was used to reconstruct the ancestral chromosome number and infer genomic events. Our approach inferred that the ancestral chromosome number of the family is n = 9. Also, according to the model that best explained our data, the evolution of haploid chromosome numbers in Asteraceae was a very dynamic process, with genome duplications and descending dysploidy being the most frequent genomic events in the evolution of this family. This model inferred more than one hundred whole genome duplication events, however it did not find evidence for a paleopolyploidization at the base of this family, which has previously been hypothesized on the basis of sequence data from a limited number of species. The obtained results and potential causes of these discrepancies are discussed.
Biodiversity results from multiple evolutionary mechanisms, including genetic variation and natural selection. Whole genome duplications (WGDs), or polyploidizations, provide opportunities for large-scale genetic modifications. Many evolutionarily successful lineages, including angiosperms and vertebrates, are ancient polyploids, suggesting that WGDs are a driving force in evolution. However, this hypothesis is challenged by the observed lower speciation and higher extinction rates of recently formed polyploids than diploids. Asteraceae includes about ten percent of angiosperm species, is thus undoubtedly one of the most successful lineages and paleopolyploidization was suggested early in this family using a small number of datasets. Here, we used genes from 64 new transcriptome datasets and others to reconstruct a robust Asteraceae phylogeny, covering 73 species from 18 tribes in six subfamilies. We estimated their divergence times and further identified multiple potential ancient WGDs within several tribes and shared by the Heliantheae alliance, core Asteraceae (Asteroideae-Mutisioideae), and also with the sister family Calyceraceae. For two of the WGD events, there were subsequent great increases in biodiversity; the older one proceeded the divergence of at least 10 subfamilies within 10 My, with great variation in morphology and physiology, while the other was followed by extremely high species richness in the Heliantheae alliance clade. Our results provide different evidence for several WGDs in Asteraceae, and reveal distinct association among WGD events, dramatic changes in environment and species radiations, providing a possible scenario for polyploids to overcome the disadvantages of WGDs and to evolve into lineages with high biodiversity.
A revision of the genus Chuquiraga (Compositae-Mutisieae). The genus Chuqui- raga as here treated comprises 19 species of xerophyllous bushes of South America; the history and systematic relationships within the genus and with other genera,and the morphology, geographical distribution and economic importance of the species are discussed. The taxonon)ic treatment includes a description of the genus, keys to the sections, series and species, and a list of excluded names. All the taxa are described and illustrated and distribution maps are given. In many cases, nomenclatural problems, intraspecific variability and affinities between the species are also analyzed.In this revision a new infrageneric classification is proposed, the genus being divided into two sections: Acanthophylla nov. sect., and Sect. Chuquiraga with two series-Parviflorae nov. ser. and Ser. Chuquiraga. Other taxonomical novelties are:Two new subspecies are describéd {Ch. spinosa Less, subsp. australis and subsp. huamanpinta) and three changes of status are proposed {Ch. spinosa subsp. rotundifolia (Weddell) nov. stat., Ch. ulicina subsp. acicularis (Don) nov. stat. and Ch. erinacea subsp. hystrix (Don) nov. stat.). The name Ch. parviflora (Gris.) Hieron., which had been reduced to synonymy of Ch. opppsi- tifolia Don, is rehabilitated, and the morphological and geographical differences between both species are discussed. A new epithet is proposed {Ch. morenonis (O. Ktze) nov. stat.) for Ch. argentea (Speg.) Speg., name invalidated by an earlier homonym. The name Ch. spinosa (Ruiz et Pav.) Don, erroneously used to designate the taxon here described as Ch. spinosa Less, subsp. huamanpinta, is excluded form the genus. The following names are reduced to synonymy for the first time: Ch. erinacea f. pulvinata Cabrera; Ch. incana Phil.; Ch. insignis var. armata Weddell; Ch. johnstonii Tovar; var. lancifolia (H. et B.) Koster; Ch. kingii Ball; Ch. oppositifolia var. macrantha Gay; Ch. oppositi- folia valr. macrocephala Weddell; Ch. pseudoruscifolia Muschler; Ch. revoluta Field et Gardn; Ch. ulicina var. incana (Phil.) Johnston.
Significance
The flowering plant family Asteraceae (e.g. sunflowers, daisies, chrysanthemums), with about 23,000 species, is found almost everywhere in the world except in Antarctica. Asteraceae (or Compositae) are regarded as one of the most influential families in the diversification and evolution of a large number of animals that heavily depends on their inflorescences to survive (e.g. bees, hummingbirds, wasps). Here we report the discovery of pollen grains unambiguously assigned to Asteraceae that remained buried in Antarctic deposits for more than 65 million years along with other extinct groups (e.g. Dinosaurs, Ammonites). Our discovery drastically pushes back the assumed origin of Asteraceae, because these pollen grains are the oldest fossils ever found for the family.
Chuquiraga is a genus of evergreen shrubs endemic to the arid and semiarid regions of the Andes and southern South America. It is the most variable morphologically of the subfamily Barnadesioideae and presents a great diversity of leaf types. The genus has been classified into two sections based on this morphological variation: Chuquiraga and Acanthophylla. Within section Chuquiraga, two series, Chuquiraga and Parviflorae, have been recognized taking into account variation in size of capitula. The objetive of this study was to conduct a comparative study of the morphology and anatomy of leaves of 19 of the 22 species of Chuquiraga, and four species of some of its related genera (Dasyphyllum, Doniophyton, and Duseniella). Our results indicate that four morpho-anatomical leaf types can be distinguished within Chuquiraga: 1) flat, dorsiventral and hypostomatic, 2) flat, isolateral and amphistomatic, 3) boat-shaped, isolateral and epiestomatic and, 4) acicular, dorsiventral inverted and epistomatic. These leaf types can be correlated with sections Chuquiraga (Types 1 and 2) and Acanthophylla (Types 3 and 4), supporting the traditional classification of the genus. In contrast, series Chuquiraga and Parviflorae cannot be distinguished on the basis of the observed leaf characteristics. Finally, leaf morphology and anatomy were useful to distinguish Chuquiraga from related genera of Barnadesioideae. The four genera studied present different xeromorphic characteristics in their leaf morphology and anatomy.
Abstract—
Chuquiraga is a genus of evergreen shrubs endemic to the arid and semiarid regions of the Andes and southern South America. The genus has been classified into two sections based on its variation in leaf morphology: Chuquiraga and Acanthophylla.
Within section Chuquiraga, two series, Chuquiraga and Parviflorae, have been recognized based on variation in size of flower heads. The objectives of this study were to test this classification and to assess the monophyly of Chuquiraga and its intergeneric relationships
with the closely related genera Doniophyton and Duseniella. The phylogenetic relationships of 24 of the 27 species and/or subspecies of Chuquiraga (19 of its 22 recognized species), plus 14 species representing seven of the remaining eight genera of Barnadesioideae, and
two species of non-barnadesioid Asteraceae were inferred using sequence data from the chloroplast DNA psbA-trnH, rps16-trnK, trnL-rpl32, and/or nuclear ribosomal DNA ITS regions. The plastid and nuclear data sets were analyzed individually and combined, using maximum parsimony,
maximum likelihood, and Bayesian inference methods. The phylogenetic results show that Chuquiraga, Duseniella, and Doniophyton form a well-supported monophyletic group, but the relationships among these genera and the monophyly of Chuquiraga are still uncertain.
The phylogenies obtained support the monophyly of the sections and reject the monophyly of the series. Section Chuquiraga is divided into two subclades: one includes all species of Chuquiraga series Parviflorae, plus Chuquiraga calchaquina and C. longiflora
(of Chuquiraga series Chuquiraga), and the other subclade includes all remaining species of Chuquiraga series Chuquiraga.
Phylogenetic relationships among the 11 species and subspecies of the Andean-Patagonian Chuquiraga sect. Acanthophyllae were resolved by parsimony cladistic analysis using 22 morphological characters. The comparative method was used to test whether a reduction in leaf width occurred in species due to an adaptation to warmer desert climates. Mean values of annual precipitation, January (summer) temperature and July (winter) temperature were estimated for each taxon. Independent comparisons for leaf width and climatic variables were calculated at each node of the cladogram and a regression analysis of leaf variation versus climatic variation was performed. The probable ancestral geographic area for the group was determined using Bremer's method. Results of these analyses suggest that marked involution and reduction in leaf width occurred twice independently in the evolution of the group. Reduction of leaf width was correlated with an increase in temperature. The Puna, Patagonia and the High Andes have the highest probability of having been part of the ancestral area of this section, which currently also extends to the Monte Prepuna and Chilean Desert. This study suggests a relatively recent climatic effect on the evolution of leaf morphology.
Previous molecular sequence and restriction site data have confirmed subfamily Barnadesioideae as basal within Asteraceae. The subfamily consists of 88 species in nine genera: Arnaldoa, Barnadesia, Chuquiraga, Dasyphyllum, Doniophyton, Duseniella, Fulcaldea, Huarpea, and Schlechtendalia. Two morphological cladistic analyses among genera or subgeneric groups within this subfamily have been completed previously, with contrasting results. Because of the importance of understanding relationships in this group of early Asteraceae, especially for insights on character evolution within the family, comprehensive morphological cladistic analyses were conducted at the specific level. Initial investigations utilising 31 characters with all 88 species led eventually to curtailed studies with 52 species. Five different outgroup hypotheses were employed: Acicarpha laxa, A. spathulata, Calycera leucanthema, C. spinulosa (all Calyceraceae), and Schlechtendalia luzulaefolia (Barnadesioideae; as functional outgroup). The results confirm Schlechtendalia as basal within Barnadesioideae. Monophyly is also confirmed for all genera, sections Chuquiraga and Acanthophyllae of Chuquiraga, and subgenus Archidasyphyllum of Dasyphyllum. All cladograms show two major groups (although statistical support values are low): (1) Chuquiraga, Doniophyton and Duseniella; and (2) Arnaldoa, Dasphyllum, Fulcaldea, Huarpea and Barnadesia. Although bilabiate (4 + 1) corollas occur in Schlechtendalia, tubular corollas are believed plesiomorphic for the subfamily because they are pervasive in Calyceraceae as well as in all other basal Barnadesioideae. Pollen with no shallow depressions also are hypothesised as plesiomorphic for Barnadesioideae, even though one depression occurs in Schlechtendalia. A southern South American origin of Barnadesioideae (and the entire family) is re-emphasised. The previously hypothesised ancient lineage of Dasyphyllum subg. Archidasyphyllum, consisting of large trees, appears more derived in the new analyses.
In this chapter, based on the available geological information, a model for the genesis and evolution of the Uruguayan landscape is proposed. A structural framework of the landscape evolution is provided and the record of such evolution in the most representative geological units is considered. A brief summary of the Uruguayan geology and its location in the regional context is performed, from Precambrian to Cenozoic times.
From the analysis of the geological record, it may be observed that the climate was very arid during part of the Jurassic and the Early Cretaceous. Together with the lava flows of the Arapey Formation, the climate became less arid as the Gondwana continents were becoming apart from each other. However, the geological record suggests that semiarid climates were still prevailing. In the Middle Cretaceous, semiarid and wetter climates progressively alternated, until the Early Tertiary, when very wet and warm conditions were established, in coincidence with the “Paleocene Eocene Thermal Maximum (PETM)”, followed by semiarid climates in the Oligocene, wetter conditions in the Miocene and semiarid again in the Pliocene, with alternating semiarid and humid conditions during the entire Quaternary.
On the basis of the paleoclimatic evolution, the development of relief is discussed, considering as bases for the analysis the different morphostructural units in which the country is divided. Due to their size, shape and location (passive margin) of Uruguay, climate uniformity is assumed for each period throughout the entire territory. It is also assumed that the surfaces around elevations of 500 meters correspond to relicts of probably pre-Cretaceous etchplains, strongly denudated, which are observed only in the surroundings of Aiguá.
The landforms situated below the oldest surfaces, for instance those below 320 m a.s.l. in the Easthern Hills Regions (Sierra del Este), correspond to a new generation of geomorphological surfaces that may be considered of Cretaceous age, according to the information presently available. This surface may be correlated with the oldest surface developed on top of the lava flows of the Arapey Formation.
The extremely warm and wet climate of the Eocene prepared the conditions for the planation processes that covered most of the Uruguayan territory during the Oligocene, generating pediplains which were later reworked during the Late Cenozoic, up to the Quaternary, generating a landscape of smooth hills.
The morphogenetic potential of each morphostructural region determined the available energy of the resulting landscape, being this at a minimum in the Santa Lucía Basin, which continued to be under subsidence condition until the Tertiary, and almost non-existant in the Laguna Merín Basin, where subsidence remains active until the Holocene.
Four new species of Asteraceae are described from Peru:Dasyphyllum brevispinum andOnoseries chrysactinioides (Mutisieae), andGynoxys congestiflora andSenecio miniauritus (Senecioneae). These species are described, illustrated, and their relationships discussed.
The pollen morphology of 59 species of the genera Arnaldoa, Barnadesia, Chuquiraga, Dasyphyllum, Doniophyton, Duseniella, Fulcaldea, Huarpea and Schlechtendalia belonging to the Barnadesioideae has been studied with light and scanning electron microscopy. Three main pollen types were recognized: (1) lophate pollen found in Barnadesia and Huarpea; (2) pollen with intercolpal depressions in Arnaldoa and some species of Dasyphyllum (subtypes I, II and III) and Schlechtendalia; and (3) pollen without depressions found in Chuquiraga, Dasyphyllum p.p., Doniophyton, Duseniella and Fulcaldea. In Dasyphyllum cryptocephalum and D. tricophyllum, we recognized a new type with 21–23 depressions. A key for the identification of pollen types is presented. Phylogenetic significance of the three palynological characters (morphology, sculpture and structure) is interpreted through phylogenies of Barnadesioideae proposed by earlier workers. Cladograms show the monophyletic group Barnadesia–Huarpea supported by a smooth exine and lophate pollen. Our results show that the 1-layered exine represents a synapomorphy for Dasyphyllum, Arnaldoa, Fulcaldea, Barnadesia and the Huarpea group.
The family Compositae has ca. 25,000 species and is estimated to have diverged approximately 45 Ma. Within the family, the small subfamily Barnadesioideae (91 spp.) is the sister group of the rest of Compositae. Four of its nine genera have only one species; one of these, Fulcaldea, is restricted to northern Peru and Ecuador as is its sister group, Arnaldoa (3 spp.). A new species, Fulcaldea stuessyi, is described from the Chapada Diamantina of Bahia, Brazil, a remarkable 4000 km disjunction. The new species is clearly a member of Fulcaldea sharing a number of important characters with the type, F. laurifolia, including a single-flowered capitulum, "plumose" pappus, shrubby habit, and style with a unique swelling. It is distinguished from that species by its red corolla and pappus, greater number of series of phyllaries, and much greater length of the corolla, style, and pappus. The location of the new taxon may be the result of vicariance or long-distance dispersal; it is named in honor of Professor Tod Stuessy.
We obtained two most parsimonious cladograms using a data set of 100 characters derived from morphology, anatomy, embryology, chemistry, and karyology, combined with three nucleotide sequence data sets (the chlo-roplast genes atpB, ndhF, and rbcL) in a phylogenetic analysis of all 12 currently recognized families in the angiosperm order Asterales, represented by 40 genera. Most clades were supported by a jackknife value of at least 50% and a Bremer support of 5 or more. Rousseaceae sensu lato (including Carpodetaceae), together with Pentaphragmataceae and Campanulaceae s.l., is the sister group to the rest of the Asterales. A sister group relationship between Donatia and Stylidiaceae is well supported both morphologically and by molecular data, and we suggest that Donatia should again be treated as a subfamily in Stylidiaceae. The sister group relationship between Calyceraceae and Asteraceae is well supported.
Premise of the study:
Phylogenies based on molecular data are revealing that generalizations about complex morphological structures often obscure variation and developmental patterns important for understanding the evolution of forms, as is the case for inflorescence morphology within the well-supported MGCA clade (Menyanthaceae + Goodeniaceae + Calyceraceae + Asteraceae). While the basal families share a basic thyrsic/thyrsoid structure of their inflorescences, Asteraceae possesses a capitulum that is widely interpreted as a racemose, condensed inflorescence. Elucidating the poorly known inflorescence structure of Calyceraceae, sister to Asteraceae, should help clarify how the Asteraceae capitulum evolved from thyrsic/thyrsoid inflorescences.
Methods:
The early development and structure of the inflorescence of eight species (five genera) of Calyceraceae were studied by SEM, and patterns of evolutionary change were interpreted via phylogenetic character mapping.
Key results:
The basic inflorescence structure of Calyceraceae is a cephalioid (a very condensed botryoid/thyrsoid). Optimization of inflorescence characters on a DNA sequence-derived tree suggests that the Asteraceae capitulum derives from a simple cephalioid through two morphological changes: loss of the terminal flower and suppression of the cymose branching pattern in the peripheral branches.
Conclusions:
Widely understood as a condensed raceme, the Asteraceae capitulum is the evolutionary result of a very reduced, condensed thyrsoid. Starting from that point, evolution worked separately only on the racemose developmental control/pattern within Asteraceae and mainly on the cymose developmental control/pattern within Calyceraceae, producing head-like inflorescences in both groups but with very different diversification potential. We also discuss possible remnants of the ancestral cephalioid structure in some Asteraceae.
Asteraceae subfamily Barnadesioideae (ten genera, c. 90 species), confined to South America, are sister to the remainder of the family. The relative antiquity of the barnadesioids might lead one to expect that they contain more wood features plesiomorphic for the family, but only one character clearly falls in that category. Pits on imperforate tracheary elements are bordered (except for annuals), whereas simple pits occur in two related families, Calyceraceae (part) and Stylidiaceae (all that have been examined); in Goodeniaceae bordered pits only occur. By attaining fully bordered pits in Chuquiraga, the imperforate tracheary elements qualify as an apomorphy, ‘neotracheids’, valuable for resisting embolism formation in dry and cold South American habitats. Neotracheids are found also in Loricaria (Asteraceae: Inuleae), also from these habitats. Neotracheids, like plesiomorphic tracheids, are conductive, unlike fibre tracheids and libriform fibres. Other barnadesioid wood characters adapted to cold and drought include grouping of vessels, high vessel density, shorter vessel elements and helical sculpture (including helical thickenings on lumen-facing walls) of secondary xylem vessels. In Chuquiraga and Dasyphyllum, these helical thickenings are bordered in some species (new report for angiosperms). Some of the barnadesioid adaptations to cold and drought can be found in North American Artemisia spp. (Asteraceae: Anthemideae), especially in montane and desert areas. Wood features of barnadesioids match their respective habits and habitats: a few trees; shrubs of humid, dry or desert areas; a distinctive rhizomatous succulent in the pampas (Schlechtendalia); a scree/gravel perennial (Huarpea) and two genera of annuals, one with succulent leaves (Duseniella) and one with rayless (at least at first) stems in arid and open soils (Doniophyton). Diversity is unusual considering the small size of the subfamily. Examples of endodermal crystals (Arnaldoa only), pith sclereids and primary xylem fibres are cited.
Dasyphyllum Kunth is the most diverse genus of the South American subfamily Barnadesioideae (Asteraceae), comprising 31 species most of which are distributed along the Brazilian Atlantic Forest, Cerrado and Caatinga domains. The genus has traditionally been divided into two subgenera, namely Archidasyphyllum and Dasy-phyllum. However, recent phylogenetic, morphological, and biogeographical evidence led to a new circum-scription of Dasyphyllum by elevating the subgenus Archidasyphyllum to the generic rank. The present work aimed to explore a chemophenetic characterization of Dasyphyllum for further supporting its new circumscription by a metabolomic approach using liquid chromatography coupled to high resolution mass spectrometry and multi-variate statistical analyses. A total of 44 mass features were identified based on their UV spectra, high resolution MS data and MS2 fragmentation patterns as well as comparisons with standard compounds. Dasyphyllum samples exhibited a diversity of phenylpropanoids: 3-O-caffeoylquinic acid, 4-O-caffeoylquinic acid, 5-O-caffeoylquinic acid, 5-O-feruloylquinic acid, 5-O-caffeoylshikimic acid, 1,3-O-dicaffeoylquinic acid, 3,4-O-dicaffeoylquinic acid, 3,5-O-dicaffeoylquinic acid and 4,5-O-dicaffeoylquinic acid. On the other hand, Archidasyphyllum displayed the 2-O-caffeoyltartaric acid, 2,3-O-dicaffeoyltartaric acid and caffeoyl-feruloyltartaric acid as distinctive constituents. The occurrence of tartaric acid ester derivatives in Archidasyphyllum and its absence in Dasyphyllum may constitute a diagnostic chemical characteristic for further supporting the segregation of Archidasyphyllum from Dasyphyllum. The occurrence of phenylpropanoids in Archidasyphyllum and Dasyphyllum is here reported for the first time.
We performed an integrated phylogeographical and palaeoclimatic study of an early-diverging member of Asteraceae, Duseniella patagonica, endemic to Argentina. Chloroplast and nuclear markers were sequenced from 106 individuals belonging to 20 populations throughout the species range. We analysed genetic spatial distribution, diversity and structure, tested for range expansion, estimated divergence times, reconstructed ancestral areas and modelled present and past species distributions based on climatic data. Duseniella diverged from its sister genera during the Late/Middle Miocene. Its ancestral area included southern Monte plus eastern and central Patagonia. A vicariant event separated Monte and Patagonian clades during the Plio-Pleistocene. This would have involved unfavourable climate, soil, elevation, volcanism and/or other geomorphological processes between 40 and 43.5°S, in the sourroundings of the Somuncura plateau. Each clade possesses its own haplotypes and nucleotypes. Two populations, one in southern Monte and the other in eastern Patagonia, contain the highest diversity and exclusive haplotypes, representing hypothetical ancestral refugia. Northern Monte and southern Patagonian populations show low to null genetic diversity, being the most recently colonized areas. Climatic models indicate that winter temperature influenced the distribution of Duseniella, with an increase in probability of occurrence during colder periods, thus enabling diversification during glacial episodes.
Morphological features of the heads (capitula) of Asteraceae have been used extensively in classification of the family at different levels of the taxonomic hierarchy. Among the various characters, features of stamens have been employed to determine relationships from specific to tribal levels, including size, shape, colour, cell size and shape of the
thecae, downwards extensions from the thecae (spurs or tails), the apex and base of the connective between the thecae, the antheropodium that joins the connective to the filament and the filament itself. We investigate variation in these staminal features in 88 species of ten genera of Asteraceae subfamily Barnadesioideae, the sister group of
the rest of the family. A new morphological categorization of antheropodia and anther bases is presented, features that show the widest ranges of variation in the subfamily. Other characters, such as apices of the connectives and fusion of filaments, are less variable. Six staminal characters are optimized on a molecular phylogenetic tree for
Barnadesioideae. Putative plesiomorphies for the ancestor of the subfamily are hypothesized to be entire apices of the connectives, antheropodia shorter than the basal appendages and filaments free and glabrous. The ancestral conditions for pollen sac extension and for attachment of anthers on the corolla tube are equivocal. Hypotheses are offered on the possible adaptive function of staminal features, such that antheropodia seem significant in structural support of the thecal tube and that spurs and tails may function in protecting the basal portion of the thecae from insect probing.
A thorough morphological circumscription of the tribe Mutisieae (Asteraceae) was established in 1977 by Angel L. Cabrera (1908–1999), who made fundamental worldwide contributions to the taxonomy of the family Asteraceae. The advance of molecular phylogenetic studies resulted in portrayals of relationships that have impacted the classification of the whole family and particularly of the Mutisieae. The publication of the book Systematics, Evolution and Biogeography of the Compositae in 2009, with the collaboration of the main worldwide specialists in the family, represented another fundamental milestone in the classification of the tribe. Mutisieae, which was previously thought to be nested far up in the phylogenetic tree of the family, is now known to be a basal grade, becoming a focus of attention for synantherologists. Traditional Mutisieae, or Mutisieae sensu Cabrera, is now split into numerous new subfamilies, tribes and subtribes. As a result of these changes, genera within the tribe have been reduced from 89 to 48 through new synonymisations, transfers to other tribes, and partly offset by description of 23 new genera. The remaining genera of Mutisieae sensu Cabrera have been placed in tribes of different subfamilies. A synthesis of these changes is presented in tables, in an illustrated key, and in a synopsis of the subfamilies with keys to tribes within the subfamilies.
The phytochemical composition of Arnaldoa species is barely known. In this work, the occurrence of caffeic acid ester derivatives and flavonoids in A. argentea, A. macbrideana and A. weberbaueri was established by liquid chromatography associated to high-resolution mass spectrometry analyses and comparison with data from isolated compounds. The distribution of chlorogenic acids in the genus Arnaldoa is herein described for the first time. The metabolite profile of Arnaldoa species was compared to that of Tithonia diversifolia, a known and rich source of chlorogenic acids and sesquiterpene lactones. In addition to the mono-and dicaffeoyl quinic acids present in T. diversifolia, Arnaldoa species exhibited the mono-and dicaffeoyl tartaric acids. Furthermore, mass features correspondent to that of sesquiterpene lactones present in T. diversifolia were not observed in Arnaldoa species. The chemotaxonomic implications of caffeic acid ester derivatives and flavonoid glycosides, as well as the potential absence of sesquiterpene lactones in the genus Arnaldoa and subfamily Barnadesioideae are discussed .
Comprising more than 25 000 species, the Sunflower Family (Compositae or Asteraceae) is the largest family of flowering plants. Many of its lineages have experienced recent and rapid radiations, and the family has a deep and widespread history of large-scale gene duplications and polyploidy. Many of the most important evolutionary questions about the family's diversity remain unanswered due to poor resolution and lack of support for major nodes of the phylogeny. Our group has employed a phylogenomics approach using Hyb-Seq that includes sequencing ∼1000 low-copy number nuclear markers, plus partial plastomes for large numbers of species. Here we discuss our progress to date and present two phylogenies comprising nine subfamilies and 25 tribes using concatenated and coalescence-based analyses. We discuss future plans for incorporating high-quality reference genomes and transcriptomes to advance systematic and evolutionary studies in the Compositae. While we have made great strides toward developing tools for employing phylogenomics and resolving relationships within Compositae, much work remains. Recently formed global partnerships will work to solve the unanswered evolutionary questions for this megafamily.
Premise of the study:
Like many other flowering plants, members of the Compositae (Asteraceae) have a polyploid ancestry. Previous analyses found evidence for an ancient duplication or possibly triplication in the early evolutionary history of the family. We sought to better place this paleopolyploidy in the phylogeny and assess its nature.
Methods:
We sequenced new transcriptomes for Barnadesia, the lineage sister to all other Compositae, and four representatives of closely related families. Using a recently developed algorithm, MAPS, we analyzed nuclear gene family phylogenies for evidence of paleopolyploidy.
Key results:
We found that the previously recognized Compositae paleopolyploidy is also in the ancestry of the Calyceraceae. Our phylogenomic analyses uncovered evidence for a successive second round of genome duplication among all sampled Compositae except Barnadesia.
Conclusions:
Our analyses of new samples with new tools provide a revised view of paleopolyploidy in the Compositae. Together with results from a high density Lactuca linkage map, our results suggest that the Compositae and Calyceraceae have a common paleotetraploid ancestor and that most Compositae are descendants of a paleohexaploid. Although paleohexaploids have been previously identified, this is the first example where the paleotetraploid and paleohexaploid lineages have survived over tens of millions of years. The complex polyploidy in the ancestry of the Compositae and Calyceraceae represents a unique opportunity to study the long-term evolutionary fates and consequences of different ploidal levels.
Spatial and temporal differences in ecological opportunity can result in disparity of net species diversification rates and consequently uneven distribution of taxon richness across the tree of life. The largest eudicotyledonous plant family Asteraceae has a global distribution and at least 460 times more species than its South American endemic sister family Calyceraceae. In this study, diversification rate dynamics across Asteraceae are examined in light of the several hypothesized causes for the family’s evolutionary success that could be responsible for rate change. The innovations of racemose capitulum and pappus, and a whole genome duplication event occurred near the origin of the family, yet we found the basal lineages of Asteraceae that evolved in South America share background diversification rates with Calyceraceae and their Australasian sister Goodeniaceae. Instead we found diversification rates increased gradually from the origin of Asteraceae approximately 69.5 Ma in the late Cretaceous through the Early Eocene Climatic Optimum at least. In contrast to earlier studies, significant rate shifts were not strongly correlated with intercontinental dispersals or polyploidization. The difference is due primarily to sampling more backbone nodes, as well as calibrations placed internally in Asteraceae that resulted in earlier divergence times than those found in most previous relaxed clock studies. Two clades identified as having transformed rate processes are the Vernonioid Clade and a clade within the Heliantheae alliance characterized by phytomelanic fruit (PF Clade) that represents an American radiation. In Africa, subfamilies Carduoideae, Pertyoideae, Gymnarrhenoideae, Cichorioideae, Corymbioideae, and Asteroideae diverged in a relatively short span of only 6.5 million years during the Middle Eocene.
Dasyphyllum diamantinense is a new species endemic to the Chapada Diamantina Mountains in the northern section of the Espinhaço Range, in Bahia State, Brazil, which grows in rocky fields, forests and savannas, and on inselbergs. The new taxon is morphologically similar to Dasyphyllum leptacanthum. Affinities and diagnostic characters are discussed, and illustrations and a map are provided.
A fourth species of Dasyphyllum sect. Dasyphyllum with a floral tube that is pilose on the outside is described here; the other three species are Dasyphyllum inerme, D. lanceolatum, and D. vepreculatum. This new species, which we name Dasyphyllum maria-lianae, is distinguished from the others by the broadly ovate leaves that are loosely villous above and densely villous below, a longer pedicel, a wider involucre, densely tomentose phyllaries, and a greater number of flowers.
Barnadesia is a South American genus with 18 species of trees and shrubs, mainly distributed in the Andes. This work represents a modem revision, which comprises taxonomic and phylogenetic aspects. The taxonomic aspect includes a description and history of the genus, keys for identification of the genera of the subfamily Barnadesioideae and the species of Barnadesia, descriptions, an account of morphological and anatomical characters (spines, leaves, hairs, corollas, anthers, achenes, pappi, and pollen), synonyms, illustrations, and distribution maps for each species, as well as a list of doubtful and excluded taxa. Two new subgenera, subg. Bacasia (Ruiz & Pav.) Urtubey and Barnadesia, and a new combination, Barnadesia lehmannii Hieron. var. villosa (I. C. Chung) Urtubey, are proposed. The following new synonymies are established: Barnadesia media D. Don = B. arborea Kunth; B. wurdackii Ferreyra = B. arborea Kunth; B. caryophylla (Vell.) S. F. Blake var. macrospinosa (Loefgr.) T. C. Chung = B. caryophylla (Vell.) S. F. Blake; B. hutchisoniana Ferreyra = B. lehmannii Hieron. var. lehmannii; B. polyacantha Wedd. var. velutina I. C. Chung = B. polyacantha Wedd. The phylogenetic analysis of Barnadesia was proposed using morphological characters. Polarity of characters was based on outgroup comparison with the genus Fulcaldea. The genus Huarpea was included to test the monophyly of Barnadesia. Two monophyletic groups were resolved: (1) B. corymbosa and B. parviflora, and (2) B. lehmannii, B. reticulata, B. caryophylla, B. polyacantha, B. glomerata, B. odorata, B. macbridei, B. jelskii, B. aculeata, B. horrida, B. macrocephala, B. pycnophylla, B. spinosa, B. arborea, B. dbmbeyana, and B. blakeana.
The Asteraceae are generally divided into two large subfamilies, the Cichorioideae (syn. Lactucoideae; tribes Mutisieae, Cardueae, Lactuceae, Vernonieae, Liabeae, Arctoteae) and the Asteroideae (Inuleae, Astereae, Anthemideae, Senecioneae, Calenduleae, Heliantheae, Eupatorieae). Recent phylogenetic analyses based on morphological and chloroplast DNA data show that the Mutisieae-Barnadesiinae are the sister group to the rest of the family. The Mutisieae-Barnadesiinae are here excluded from the Mutisieae and elevated to the new subfamily Barnadesioidae.
New fossil pollen grains were recovered from marine Miocene deposits from eastern Patagonia (southern South America). Sculpture and structure exine features indicate a close relationship with modern Barnadesioideae, a basal lineage within Asteraceae. Barnadesioideae is confined to South America and is represented mainly by shrubs, herbs and some trees occurring in different habitats under a wide range of climatic conditions. It has recently attracted a great deal of attention as it was considered the sister-group to the remaining members of the family based on molecular data. Barnadesioideae has not previously been described in the fossil record. One new genus and three species are erected in Quillembaypollis gamerroi, Q.tayuoides and Q.stuessyi to assemble distinct pollen types clearly similar to those produced today by extant Chuquiraga, Dasyphyllum and Schlechtendalia, respectively. These are the first fossil records of these genera, taking them back 23–20 Ma (Dasyphyllum and Chuquiraga types) and 11–9 Ma (Schlechtendalia type). The new morphotaxon is clearly distinguishable by being microechinate, and by having a thick sexine formed by one (Q. tayuoides), two (Q. gamerroi) or three (Q. stuessyi) layers, as the most prominent features. Their closest living relatives today grow far from the studied site (eastern Patagonia), with the exception of Chuquiraga type which is the sole surviving group in the region. Pollen and spore assemblages of Early Miocene age (23–20 Ma) from southern South America indicate that the climate was sub-humid and temperate to warm–temperate. This climatic trend may have allowed Dasyphyllum species to radiate in eastern Patagonian forests, while Chuquiraga probably occupied more open areas along the coast. Late Miocene (11–9 Ma) palynological assemblages suggest warm but seasonally dry conditions, in which Schlechtendalia developed probably in the hinterland vegetation joined with low trees, and halophytic/xerophytic shrubs and herbs.
Recent molecular studies in Asteraceae have divided tribe Mutisieae (sensu Cabrera) into 13 tribes and eight subfamilies. Each of the major clades is well supported but the relationships among them are not always clear. Some of the new taxa are easily characterized by morphological data but others are not, chief among the latter being three subfamilies (Stifftioideae, Wunderlichioideae and Gochnatioideae) and the tribe Hyalideae. To under-stand evolution in the family it is critical to investigate potential morphological characters that can help to evaluate the basal lineages of the Asteraceae. The data for this study were taken from 52 species in 24 genera representing the basal groups in the family. Many characters were examined but most of the useful ones were from reproductive structures. Several apomorphies supported a few of the clades. For instance, members of subfamily Wunderlichioideae (Hyalideae and Wunderlichieae) share predominantly ten-ribbed achenes and members of Wunderlichioideae + Stifftioideae share two synapomorphies: 100–150 (200) pappus elements, arranged in (three) four or five series. These apomorphies can be viewed as an indication of a sister-group relationship between the two subfamilies as the placement of Stifftieae was not well resolved by the molecular data. Members of Wunderlichieae are characterized by having a paleaceous receptacle, style branches that are strongly papillose above and below the bifurcation, and a pappus of scales. Hyalis and Ianthopappus (Hyalideae) share venation type and an apiculate anther appendage but these are also found in Gochnatieae. Other clades have fewer supporting characters. These characters are just a beginning. Cladograms with morphology characters plotted, illustrations and a key to the basal grade of Asteraceae are provided.
The vegetation and climate of the Pampa grassland, Argentina, during the late Quaternary are reconstructed from pollen recovered from dated stratigraphic sections from arroyo walls and from archaelogical excavations. Prior to 10,500 yr B.P., herbaceous psammophytic steppe existed in the central part of the Pampa grassland while xerophytic woodland associated with psammophytic and halophytic steppe occurred in the southwestern part of the Pampa. These types of vegetation and the continental conditions that prevailed in the area of the present-day coast (38°S), indicate subhumid-dry climate and annual precipitation 100 mm lower than present. A subsequent change toward a vegetation characteristic of ponds, swamps, and foodplains, or toward environments with locally more effective moisture, occurred ca. 10,500 yr B.P. suggesting annual precipitation close to modern levels or a higher availability of water in the central part of the Pampa grassland, this type of vegetation existed until 8000 yr B.P., when it was replaced by grassland communities that lasted until 7000 yr B.P. In the southwestern part of the Pampa grassland, this vegetation developed before 7000 yr B.P. and persisted until ca. 5000 yr B.P. Sea level higher than the present ca. 6200 yr B.P. is consistent with sharp modification of the vegetation and development of local halophytic communities dominant at 38°S. A return to subhumid-dry conditions occurred after 5000 yr B.P. The late Holocene vegetation is characterized by pollen assemblages similar to the psammophytic and halophytic communities of the Southern pampa grassland, associated with communities with more edaphic conditions. At the same time, at 38°S a sea level regression is suggested by the dominance of fresh-water pollen assemblages and micropaleontological remains. The trend toward humid, temperate conditions ca. 1000 yr B.P. suggested by vertebrate remains characteristic of temperate and humid conditions, as well as a very short but dry episode during the 18th century suggested by the geology, are not clearly evidenced in the pollen sequences. Vegetational and climatic changes are explained by the latitudinal shifts and changes in intensity of the southern atmospheric circulation and changes in sea level.
The small but morphologically diverse subfamily Barnadesioideae of the sunflower family, Asteraceae, is of special interest as it constitutes the sister-group to the rest of the family. Therefore it is of critical importance for elucidating the origin and early evolution of Asteraceae. Cladistic analyses of DNA sequence variation in the trnL intron and nuclear ribosomal ITS regions strongly support five major clades in the subfamily: Schlechtendalia, Chuquiraga-Doniophyton, Barnadesia-Huarpea, Dasyphyllum subgenus Dasyphyllutn and a clade comprising Dasyphyllum subgenus Archidasyphyllum, Arnaldoa and Fulcaldea. Within Dasyphyllum subgenus Dasyphyllum, D. hystrix has a basal position, and sect. Macrocephala is supported as monophyletic, while sect. Microcephala lacks jackknife support. Within Barnadesia, B. parviflora has a very divergent ITS sequence and a basal position in the genus. The phylogenetic trees make some sense of the great morphological variation within the subfamily, although some clades identified here lack obvious defining morphological characteristics. Optimisation of geographical distributions onto the molecular phylogenies shows that the Barnadesioideae most likely originated in southern South America.