The first Gondwanan Euphorbiaceae fossils reset the biogeographic history of the Macaranga-Mallotus clade.

PREMISE: The spurge family Euphorbiaceae is prominent in tropical rainforests worldwide, particularly in Asia. There is little consensus on the biogeographic origins of the family or its principal lineages. No confirmed spurge macrofossils have come from Gondwana. METHODS: We describe the first Gondwanan macrofossils of Euphorbiaceae, represented by two infructescences and associated peltate leaves from the early Eocene (52 Myr ago [Ma]) Laguna del Hunco site in Chubut, Argentina. RESULTS: The infructescences are panicles bearing tiny, pedicellate, spineless capsular fruits with two locules, two axile lenticular seeds, and two unbranched, plumose stigmas. The fossils' character combination only occurs today in some species of the Macaranga-Mallotus clade (MMC; Euphorbiaceae), a widespread Old-World understory group often thought to have tropical Asian origins. The associated leaves are consistent with extant Macaranga. CONCLUSIONS: The new fossils are the oldest known for the MMC, demonstrating its Gondwanan history and marking its divergence by at least 52 Ma. This discovery makes an Asian origin of the MMC unlikely because immense oceanic distances separated Asia and South America 52 Ma. The only other MMC reproductive fossils so far known are also from the southern hemisphere (early Miocene, southern New Zealand), far from the Asian tropics. The MMC, along with many other Gondwanan survivors, most likely entered Asia during the Neogene Sahul-Sunda collision. Our discovery adds to a substantial series of well-dated, well-preserved fossils from one undersampled region, Patagonia, that have changed our understanding of plant biogeographic history.

A new fossil Acmopyle with accessory transfusion tissue and potential reproductive buds: Direct evidence for ever-wet rainforests in Eocene Patagonia.

PREMISE: Acmopyle (Podocarpaceae) comprises two extant species from Oceania that are physiologically restricted to ever-wet rainforests, a confirmed fossil record based on leaf adpressions and cuticles in Australia since the Paleocene, and a few uncertain reports from New Zealand, Antarctica, and South America. We investigated fossil specimens with Acmopyle affinities from the early Eocene Laguna del Hunco site in Patagonia, Argentina. METHODS: We studied 42 adpression leafy-shoot fossils and included them in a total evidence phylogenetic analysis. RESULTS: Acmopyle grayae sp. nov. is based on heterophyllous leafy shoots with three distinct leaf types. Among these, bilaterally flattened leaves uniquely preserve subparallel, linear features that we interpret as accessory transfusion tissue (ATT, an extra-venous water-conducting tissue). Some apical morphologies of A. grayae shoots are compatible with the early stages of ovuliferous cone development. Our phylogenetic analysis recovers the new species in a polytomy with the two extant Acmopyle species. We report several types of insect-herbivory damage. We also transfer Acmopyle engelhardti from the middle Eocene Río Pichileufú flora to Dacrycarpus engelhardti comb. nov. CONCLUSIONS: We confirm the biogeographically significant presence of the endangered West Pacific genus Acmopyle in Eocene Patagonia. Acmopyle is one of the most drought-intolerant genera in Podocarpaceae, possibly due to the high collapse risk of the ATT, and thus the new fossil species provides physiological evidence for the presence of an ever-wet rainforest environment at Laguna del Hunco during the Early Eocene Climatic Optimum.

Cunoniaceae infructescences from the early Eocene Laguna del Hunco flora, Patagonia, Argentina.

PREMISE: Two distinct types of fossil infructescences from the early Eocene Laguna del Hunco flora, Chubut Province, Patagonia, Argentina, preserve features of the family Cunoniaceae. The goal of the study was to assess their affinities within Cunoniaceae and to interpret their evolutionary and biogeographical significance. METHODS: Specimens were collected from the Tufolitas Laguna del Hunco, Huitrera Formation. They were prepared, photographed, and compared morphologically with similar extant and fossil fruits and infructescences using published literature and herbarium material. RESULTS: The fruit and infructescence morphology place the fossil taxa within Cunoniaceae. They do not conform to any extant genus, supporting the erection of two new fossil genera. Racemofructus gen. nov. shares diagnostic features of the tribe Cunonieae, especially Weinmannia s.l., and exhibits two tribal morphological synapomorphies: a racemose inflorescence and a replum composed of a single column. Cunoniocarpa gen. nov. specimens are paniculate inflorescences with basipetally dehiscent, bicarpellate capsules that have persistent styles and calyces. Its replum morphology suggests an affinity to the tribe Caldcluvieae, particularly to the genus Ackama. CONCLUSIONS: The new Patagonian fossils described herein constitute the oldest record of cunoniaceous capsules globally, supplementing a significant body of fossil evidence from pollen, wood, and reproductive structures from southern South America and Antarctica that suggests that the Cunoniaceae were diversified and widely distributed in the southern hemisphere by the early Eocene. Racemofructus and Cunoniocarpa are, respectively, the first fossil records from South America of reproductive structures with affinity to tribes Cunonieae and Caldcluvieae.

Fossil evidence from South America for the diversification of Cunoniaceae by the earliest Palaeocene.

BACKGROUND AND AIMS: Cunoniaceae are woody plants with a distribution that suggests a complex history of Gondwanan vicariance, long-distance dispersal, diversification and extinction. Only four out of ~27 genera in Cunoniaceae are native to South America today, but the discovery of extinct species from Argentine Patagonia is providing new information about the history of this family in South America. METHODS: We describe fossil flowers collected from early Danian (early Palaeocene, ~64 Mya) deposits of the Salamanca Formation. We compare them with similar flowers from extant and extinct species using published literature and herbarium specimens. We used simultaneous analysis of morphology and available chloroplast DNA sequences (trnL-F, rbcL, matK, trnH-psbA) to determine the probable relationship of these fossils to living Cunoniaceae and the co-occurring fossil species Lacinipetalum spectabilum. KEY RESULTS: Cunoniantha bicarpellata gen. et sp. nov. is the second species of Cunoniaceae to be recognized among the flowers preserved in the Salamanca Formation. Cunoniantha flowers are pentamerous and complete, the anthers contain in situ pollen, and the gynoecium is bicarpellate and syncarpous with two free styles. Phylogenetic analysis indicates that Cunoniantha belongs to crown-group Cunoniaceae among the core Cunoniaceae clade, although it does not have obvious affinity with any tribe. Lacinipetalum spectabilum, also from the Salamanca Formation, belongs to the Cunoniaceae crown group as well, but close to tribe Schizomerieae. CONCLUSIONS: Our findings highlight the importance of West Gondwana in the evolution of Cunoniaceae during the early Palaeogene. The co-occurrence of C. bicarpellata and L. spectabilum, belonging to different clades within Cunoniaceae, indicates that the diversification of crown-group Cunoniaceae was under way by 64 Mya.

Paleoaltingia gen. nov., a new genus of Altingiaceae from the Late Cretaceous of New Jersey.

PREMISE: Altingiaceae is a small family with a bimodal Northern Hemisphere distribution in eastern North America and eastern Asia, and a rich Cenozoic fossil record. The charcoalified fossil infructescence Paleoaltingia gen. nov. from Turonian (Late Cretaceous) deposits of New Jersey, provides new evidence of early Altingiaceae reproductive structures and has biogeographical implications in understanding modern distribution. METHODS: Fossils were prepared using standard methods for obtaining and processing mesofossils. The fossils were examined with light microscopy, and scanning electron microscopy for observing structural and anatomical details. Phylogenetic analyses were performed using a combined matrix of molecular and morphological data. RESULTS: Based on morphological features of the fossil and the phylogenetic analyses, the new genus, Paleoaltingia, with two species (Paleoaltingia ovum-dinosauri and P. polyodonta) is erected. The phylogenetic position of Paleoaltingia confirms affinities with living Altingiaceae. CONCLUSIONS: The combination of characters-simple capitate infructescence, syncarpous bicarpellate, and bilocular ovary, unique sterile phyllome structures-indicates that the fossil taxa have close affinities to modern Altingiaceae. The unique characters of the phyllomes provide new information on the floral diversity of Altingiaceae. The emergence of Paleoaltingia in Late Cretaceous sediments of Northeastern North America represents the earliest fossil record of Altingiaceae and provides new insights into its biogeography.

New physaloid fruit-fossil species from early Eocene South America.

PREMISE: Solanaceae is a scientifically and economically important angiosperm family with a minimal fossil record and an intriguing early evolutionary history. Here, we report a newly discovered fossil lantern fruit with a suite of features characteristic of Physalideae within Solanaceae. The fossil comes from the early Eocene Laguna del Hunco site (ca. 52 Ma) in Chubut, Argentina, which previously yielded the only other physaloid fruit fossil, Physalis infinemundi. METHODS: The fruit morphology and calyx venation pattern of the new fossil were compared with P. infinemundi and extant species of Solanaceae. RESULTS: Physalis hunickenii sp. nov. is clearly distinct from P. infinemundi in its fruiting calyx with wider primary veins, longer and thinner lobes, and especially in its venation pattern with high density, transverse tertiary veins; these features support its placement in a new species. In comparison with extant physaloid genera, the calyx venation pattern and other diagnostic traits reinforce placement of the new fossil, like P. infinemundi, within the tribe Physalideae of Solanaceae. CONCLUSIONS: Both species of fossil nightshades from Laguna del Hunco represent crown-group Solanaceae but are older than all prior age estimates of the family. Although at least 20 transoceanic dispersals have been proposed as the driver of range expansion of Solanaceae, the Patagonian fossils push back the diversification of the family to Gondwanan times. Thus, overland dispersal across Gondwana is now a likely scenario for at least some biogeographic patterns, in light of the ancient trans-Antarctic land connections between South America and Australia.

52 million years old Eucalyptus flower sheds more than pollen grains.

PREMISE: Fossils provide fundamental evidence of the evolutionary processes that crafted today's biodiversity and consequently for understanding life on Earth. We report the finding of Myrtaceidites eucalyptoides pollen grains preserved within the anthers of a 52-million-year-old Eucalyptus flower collected at Laguna del Hunco locality of Argentinean Patagonia and discuss its implications in understanding the evolutionary history of the iconic Australian genus Eucalyptus. METHODS: Pollen grains were extracted from the flower's anthers and were then observed under light microscopy and scanning electron microscopy. The phylogenetic position of the fossil was investigated by adding pollen data to a previously published total-evidence matrix and analyzing it using parsimony. RESULTS: We erect the species Eucalyptus xoshemium for the fossil flower. Pollen extracted from E. xoshemium belongs to the species Myrtaceidites eucalyptoides, which, until now, was only known as dispersed pollen. The numerous pollen grains recovered from the single flower allowed estimation of M. eucalyptoides' variability. Results of the phylogenetic analysis reinforce the position of this fossil within crown group Eucalyptus. CONCLUSIONS: The discovery of these pollen grains within a Patagonian Eucalyptus fossil flower confirms the hypothesis that Myrtaceidites eucalyptoides represents fossil pollen in the Eucalyptus lineage, extends the geographic and stratigraphic fossil pollen record, and supports an earlier age for crown-group eucalypts.

Reinterpretation of Paleoazolla: a heterosporous water fern from the Late Cretaceous of Patagonia, Argentina.

PREMISE: Undoubtedly, fossils are critical for understanding evolutionary transformations in deep time. Here, we reinvestigate the microspores and megaspores of Paleoazolla patagonica, a water fern found in Late Cretaceous sediments of the Chubut Province, Patagonia, Argentina, which provides novel evidence on the past history of the water fern clade. The study was based on recently collected specimens and additional observations of the original material. METHODS: Most specimens analyzed herein were obtained from new palynological samples collected at the Cerro Bosta and Cañadón del Irupé localities, La Colonia Formation. Samples were mechanically disaggregated and treated with hydrofluoric and hydrochloric acid. Spores were studied using standard light microscopy and scanning electron microscopy. We also reexamined the original materials. RESULTS: The newly described characters of Paleoazolla include the presence of heterosporangiate sori composed of one ellipsoidal megasporangium surrounded by three to four oval microsporangia, megasporangium containing one hairy massula that encloses two trilete megaspores (rarely one or three), and microsporangia containing numerous microspore massulae with non-septate multibarbed glochidia and one trilete microspore per massula. CONCLUSIONS: The reinterpretation has revealed a novel set of characters for understanding the evolution of heterosporous water ferns. The presence of two megaspores in the megasporangium of Paleoazolla exposes serious gaps in the current knowledge on the evolution of monomegaspory in heterosporous water ferns, a fact that emphasizes the need of including fossils within phylogenies to elucidate patterns of character acquisition among water ferns.

Fossil flowers from the early Palaeocene of Patagonia, Argentina, with affinity to Schizomerieae (Cunoniaceae).

Background and Aims: Early Palaeocene (Danian) plant fossils from Patagonia provide information on the recovery from the end-Cretaceous extinction and Cenozoic floristic change in South America. Actinomorphic flowers with eight to ten perianth parts are described and evaluated in a phylogenetic framework. The goal of this study is to determine the identity of these fossil flowers and to discuss their evolutionary, palaeoecological and biogeographical significance. Methods: More than 100 fossilized flowers were collected from three localities in the Danian Salamanca and Peñas Coloradas Formations in southern Chubut. They were prepared, photographed and compared with similar extant and fossil flowers using published literature and herbarium specimens. Phylogenetic analysis was performed using morphological and molecular data. Key results: The fossil flowers share some but not all the synapomorphies that characterize the Schizomerieae, a tribe within Cunoniaceae. These features include the shallow floral cup, variable number of perianth parts arranged in two whorls, laciniate petals, anthers with a connective extension, and a superior ovary with free styles. The number of perianth parts is doubled and the in situ pollen is tricolporate, with a surface more like that of other Cunoniaceae outside Schizomerieae, such as Davidsonia or Weinmannia. Conclusions: An extinct genus of crown-group Cunoniaceae is recognized and placed along the stem lineage leading to Schizomerieae. Extant relatives are typical of tropical to southern-temperate rainforests, and these fossils likely indicate a similarly warm and wet temperate palaeoclimate. The oldest reliable occurrences of the family are fossil pollen and wood from the Upper Cretaceous of the Antarctica and Argentina, whereas in Australia the family first occurs in upper Palaeocene deposits. This discovery demonstrates that the family survived the Cretaceous-Palaeogene boundary event in Patagonia and that diversification of extant lineages in the family was under way by the earliest Cenozoic.

Fossil moonseeds from the Paleogene of West Gondwana (Patagonia, Argentina).

PREMISE OF THE STUDY: The fossil record is critical for testing biogeographic hypotheses. Menispermaceae (moonseeds) are a widespread family with a rich fossil record and alternative hypotheses related to their origin and diversification. The family is well-represented in Cenozoic deposits of the northern hemisphere, but the record in the southern hemisphere is sparse. Filling in the southern record of moonseeds will improve our ability to evaluate alternative biogeographic hypotheses. METHODS: Fossils were collected from the Salamanca (early Paleocene, Danian) and the Huitrera (early Eocene, Ypresian) formations in Chubut Province, Argentina. We photographed them using light microscopy, epifluorescence, and scanning electron microscopy and compared the fossils with similar extant and fossil Menispermaceae using herbarium specimens and published literature. KEY RESULTS: We describe fossil leaves and endocarps attributed to Menispermaceae from Argentinean Patagonia. The leaves are identified to the family, and the endocarps are further identified to the tribe Cissampelideae. The Salamancan endocarp is assigned to the extant genus Stephania. These fossils significantly expand the known range of Menispermaceae in South America, and they include the oldest (ca. 64 Ma) unequivocal evidence of the family worldwide. CONCLUSIONS: Our findings highlight the importance of West Gondwana in the evolution of Menispermaceae during the Paleogene. Currently, the fossil record does not discern between a Laurasian or Gondwanan origin; however, it does demonstrate that Menispermaceae grew well outside the tropics by the early Paleocene. The endocarps' affinity with Cissampelideae suggests that diversification of the family was well underway by the earliest Paleocene.

Araucaria lefipanensis (Araucariaceae), a new species with dimorphic leaves from the Late Cretaceous of Patagonia, Argentina.

PREMISE OF THE STUDY: We describe a new araucarian species, Araucaria lefipanensis, from the Late Cretaceous flora of the Lefipán Formation, in Patagonia (Argentina) based on reproductive and vegetative remains, with a combination of characters that suggest mosaic evolution in the Araucaria lineage. METHODS: The studied fossils were found at the Cañadón del Loro locality. Specimens were separated into two leaf morphotypes, and their morphological differences were tested with MANOVA. KEY RESULTS: The new species Araucaria lefipanensis is erected based on the association of dimorphic leaves with cuticle remains and isolated cone scale complexes. The reproductive morphology is characteristic of the extant section Eutacta, whereas the vegetative organs resemble those of the sections Intermedia, Bunya, and Araucaria (the broad-leaved clade). CONCLUSIONS: The leaf dimorphism of A. lefipanensis is similar to that of extant A. bidwillii, where dimorphism is considered to be related to seasonal growth. The leaf dimorphism in A. lefipanensis is consistent with the paleoclimatic and paleoenvironmental reconstructions previously suggested for the Lefipán Formation, which is thought to have been a seasonal subtropical forest. The new species shows evidence of mosaic evolution, with cone scale complexes morphologically similar to section Eutacta and leaves similar to the sections of the broad-leaved clade, constituting a possible transitional form between these two well-defined lineages. More complete plant concepts, especially those including both reproductive and vegetative remains are necessary to understand the evolution of ancient plant lineages. This work contributes to this aim by documenting a new species that may add to the understanding of the early evolution of the sections of Araucaria.

A late Cretaceous fagalean inflorescence preserved in amber from New Jersey.

PREMISE OF THE STUDY: An inflorescence with three pistillate flowers in amber from the early Upper Cretaceous (Turonian, ~90-94 million years ago) of central New Jersey represents the oldest known flowers with features present in an early stem complex of the Fagales. The inflorescence has characteristics of Nothofagaceae, but also has strikingly distinct characters that suggest it is intermediate between Nothofagus and other Fagales. This intermediacy is consistent with its northern hemisphere distribution. METHODS: We investigated this new fossil by comparing it with extant and fossil members of the Fagales using light microscopy and nano-computed tomography. In addition, for exploring its relationships, we mapped the morphological characters onto a widely accepted molecular-based tree of modern basal Fagales using standard methods of character optimization. KEY RESULTS: The phylogenetic position of the fossil inflorescence can be unequivocally determined by the presence of unique features, singly and in combination, that are found only in "basal" members of Fagales. The fossil adds critical information on the features of the early stem Fagales, evolution of the cupule in Nothofagaceae and Fagaceae, and a reasonable biogeographic hypothesis for the differentiation of southern (e.g., Nothofagaceae) and northern hemisphere Fagales. CONCLUSIONS: This new fossil provides insight into the early evolution of Fagales and suggests that early stem Fagales that had not yet differentiated into modern families were present in the Late Cretaceous of North America. Based on available evidence, the fossil is best interpreted as an early stem member of the Fagales, with features that suggest a transition from a more generalized Nothofagus-like fagalean ancestor with some unique presumably plesiomorphic features. The presence of an enlarged perianth and flexuous styles also suggests the possibility of insect pollination, which has been lost in all Fagales with the exception of some members of subfamily Castaneoideae in Fagaceae sensu stricto (which otherwise are very different from this fossil). The poorly developed, bract-like cupule valves of the fossil can be interpreted as primitive (i.e., incipient) or as reduced from more developed cupules that are found in most modern Fagaceae and Nothofagaceae.

Monocot plastid phylogenomics, timeline, net rates of species diversification, the power of multi-gene analyses, and a functional model for the origin of monocots.

PREMISE OF THE STUDY: We present the first plastome phylogeny encompassing all 77 monocot families, estimate branch support, and infer monocot-wide divergence times and rates of species diversification. METHODS: We conducted maximum likelihood analyses of phylogeny and BAMM studies of diversification rates based on 77 plastid genes across 545 monocots and 22 outgroups. We quantified how branch support and ascertainment vary with gene number, branch length, and branch depth. KEY RESULTS: Phylogenomic analyses shift the placement of 16 families in relation to earlier studies based on four plastid genes, add seven families, date the divergence between monocots and eudicots+Ceratophyllum at 136 Mya, successfully place all mycoheterotrophic taxa examined, and support recognizing Taccaceae and Thismiaceae as separate families and Arecales and Dasypogonales as separate orders. Only 45% of interfamilial divergences occurred after the Cretaceous. Net species diversification underwent four large-scale accelerations in PACMAD-BOP Poaceae, Asparagales sister to Doryanthaceae, Orchidoideae-Epidendroideae, and Araceae sister to Lemnoideae, each associated with specific ecological/morphological shifts. Branch ascertainment and support across monocots increase with gene number and branch length, and decrease with relative branch depth. Analysis of entire plastomes in Zingiberales quantifies the importance of non-coding regions in identifying and supporting short, deep branches. CONCLUSIONS: We provide the first resolved, well-supported monocot phylogeny and timeline spanning all families, and quantify the significant contribution of plastome-scale data to resolving short, deep branches. We outline a new functional model for the evolution of monocots and their diagnostic morphological traits from submersed aquatic ancestors, supported by convergent evolution of many of these traits in aquatic Hydatellaceae (Nymphaeales).

Ceratopetalum (Cunoniaceae) fruits of Australasian affinity from the early Eocene Laguna del Hunco flora, Patagonia, Argentina.

Background and Aims: Radially symmetrical, five-winged fossil fruits from the highly diverse early Eocene Laguna del Hunco flora of Chubut Province, Patagonia, Argentina, are named, described and illustrated. The main goals are to assess the affinities of the fossils and to place them in an evolutionary, palaeoecological and biogeographic context. Methods: Specimens of fossil fruits were collected from the Tufolitas Laguna del Hunco. They were prepared, photographed and compared with similar extant and fossil fruits using published literature. Their structure was also evaluated by comparing them with that of modern Ceratopetalum (Cunoniaceae) fruits through examination of herbarium specimens. Key Results: The Laguna del Hunco fossil fruits share the diagnostic features that characterize modern and fossil Ceratopetalum (symmetry, number of fruit wings, presence of a conspicuous floral nectary and overall venation pattern). The pattern of the minor wing (sepal) veins observed in the Patagonian fossil fruits is different from that of modern and previously described fossil Ceratopetalum fruits; therefore, a new fossil species is recognized. An apomorphy (absence of petals) suggests that the fossils belong within crown-group Ceratopetalum . Conclusions: The Patagonian fossil fruits are the oldest known record for Ceratopetalum . Because the affinities, provenance and age of the fossils are so well established, this new Ceratopetalum fossil species is an excellent candidate for use as a calibration point in divergence dating studies of the family Cunoniaceae. It represents the only record of Ceratopetalum outside Australasia, and further corroborates the biogeographic connection between the Laguna del Hunco flora and ancient and modern floras of the Australasian region.

The fossil flip-leaves (Retrophyllum, Podocarpaceae) of southern South America.

PREMISE OF THE STUDY: The flip-leaved podocarp Retrophyllum has a disjunct extant distribution in South American and Australasian tropical rainforests and a Gondwanic fossil record since the Eocene. Evolutionary, biogeographic, and paleoecological insights from previously described fossils are limited because they preserve little foliar variation and no reproductive structures. METHODS: We investigated new Retrophyllum material from the terminal Cretaceous Lefipán, the early Eocene Laguna del Hunco, and the early/middle Eocene Río Pichileufú floras of Patagonian Argentina. We also reviewed type material of historical Eocene fossils from southern Chile. KEY RESULTS: Cretaceous Retrophyllum superstes sp. nov. is described from a leafy twig, while Eocene R. spiralifolium sp. nov. includes several foliage forms and a peduncle with 13 pollen cones. Both species preserve extensive damage from sap-feeding insects associated with foliar transfusion tissue. The Eocene species exhibits a suite of characters linking it to both Neotropical and West Pacific Retrophyllum, along with several novel features. Retrophyllum araucoensis (Berry) comb. nov. stabilizes the nomenclature for the Chilean fossils. CONCLUSIONS: Retrophyllum is considerably older than previously thought and is a survivor of the end-Cretaceous extinction. Much of the characteristic foliar variation and pollen-cone morphology of the genus evolved by the early Eocene. The mixed biogeographic signal of R. spiralifolium supports vicariance and represents a rare Neotropical connection for terminal-Gondwanan Patagonia, which is predominantly linked to extant Australasian floras due to South American extinctions. The leaf morphology of the fossils suggests significant drought vulnerability as in living Retrophyllum, indicating humid paleoenvironments.

Phylogenetic biome conservatism on a global scale.

How and why organisms are distributed as they are has long intrigued evolutionary biologists. The tendency for species to retain their ancestral ecology has been demonstrated in distributions on local and regional scales, but the extent of ecological conservatism over tens of millions of years and across continents has not been assessed. Here we show that biome stasis at speciation has outweighed biome shifts by a ratio of more than 25:1, by inferring ancestral biomes for an ecologically diverse sample of more than 11,000 plant species from around the Southern Hemisphere. Stasis was also prevalent in transocean colonizations. Availability of a suitable biome could have substantially influenced which lineages establish on more than one landmass, in addition to the influence of the rarity of the dispersal events themselves. Conversely, the taxonomic composition of biomes has probably been strongly influenced by the rarity of species' transitions between biomes. This study has implications for the future because if clades have inherently limited capacity to shift biomes, then their evolutionary potential could be strongly compromised by biome contraction as climate changes.

The plant ontology as a tool for comparative plant anatomy and genomic analyses.

The Plant Ontology (PO; http://www.plantontology.org/) is a publicly available, collaborative effort to develop and maintain a controlled, structured vocabulary ('ontology') of terms to describe plant anatomy, morphology and the stages of plant development. The goals of the PO are to link (annotate) gene expression and phenotype data to plant structures and stages of plant development, using the data model adopted by the Gene Ontology. From its original design covering only rice, maize and Arabidopsis, the scope of the PO has been expanded to include all green plants. The PO was the first multispecies anatomy ontology developed for the annotation of genes and phenotypes. Also, to our knowledge, it was one of the first biological ontologies that provides translations (via synonyms) in non-English languages such as Japanese and Spanish. As of Release #18 (July 2012), there are about 2.2 million annotations linking PO terms to >110,000 unique data objects representing genes or gene models, proteins, RNAs, germplasm and quantitative trait loci (QTLs) from 22 plant species. In this paper, we focus on the plant anatomical entity branch of the PO, describing the organizing principles, resources available to users and examples of how the PO is integrated into other plant genomics databases and web portals. We also provide two examples of comparative analyses, demonstrating how the ontology structure and PO-annotated data can be used to discover the patterns of expression of the LEAFY (LFY) and terpene synthase (TPS) gene homologs.

Testing the impact of calibration on molecular divergence times using a fossil-rich group: the case of Nothofagus (Fagales).

Although temporal calibration is widely recognized as critical for obtaining accurate divergence-time estimates using molecular dating methods, few studies have evaluated the variation resulting from different calibration strategies. Depending on the information available, researchers have often used primary calibrations from the fossil record or secondary calibrations from previous molecular dating studies. In analyses of flowering plants, primary calibration data can be obtained from macro- and mesofossils (e.g., leaves, flowers, and fruits) or microfossils (e.g., pollen). Fossil data can vary substantially in accuracy and precision, presenting a difficult choice when selecting appropriate calibrations. Here, we test the impact of eight plausible calibration scenarios for Nothofagus (Nothofagaceae, Fagales), a plant genus with a particularly rich and well-studied fossil record. To do so, we reviewed the phylogenetic placement and geochronology of 38 fossil taxa of Nothofagus and other Fagales, and we identified minimum age constraints for up to 18 nodes of the phylogeny of Fagales. Molecular dating analyses were conducted for each scenario using maximum likelihood (RAxML + r8s) and Bayesian (BEAST) approaches on sequence data from six regions of the chloroplast and nuclear genomes. Using either ingroup or outgroup constraints, or both, led to similar age estimates, except near strongly influential calibration nodes. Using "early but risky" fossil constraints in addition to "safe but late" constraints, or using assumptions of vicariance instead of fossil constraints, led to older age estimates. In contrast, using secondary calibration points yielded drastically younger age estimates. This empirical study highlights the critical influence of calibration on molecular dating analyses. Even in a best-case situation, with many thoroughly vetted fossils available, substantial uncertainties can remain in the estimates of divergence times. For example, our estimates for the crown group age of Nothofagus varied from 13 to 113 Ma across our full range of calibration scenarios. We suggest that increased background research should be made at all stages of the calibration process to reduce errors wherever possible, from verifying the geochronological data on the fossils to critical reassessment of their phylogenetic position.

First record of Todea (Osmundaceae) in South America, from the early Eocene paleorainforests of Laguna del Hunco (Patagonia, Argentina).

PREMISE OF THE STUDY: The early Eocene Laguna del Hunco caldera-lake paleoflora (ca. 52 Ma) from Chubut Province, Argentina, is notably diverse and includes many conifer and angiosperm lineages that are extinct in South America but extant in Australasian rainforests. No ferns have been previously described from Laguna del Hunco. We describe and interpret a new species of fossil Osmundaceae based on fertile and sterile pinnae. • METHODS: The fossil specimens were compared with other extant and fossil Osmundaceae based on living and herbarium material and published descriptions. A morphological matrix based on 29 characters was constructed for 17 living species in Osmundaceae, four species assigned to the fossil genus Todites, and the new fossil species. Phylogenetic analyses were conducted under parsimony using morphology and total evidence matrices. • KEY RESULTS: Both the new fossil and the Todites species were consistently resolved within the leptopteroid clade of Osmundaceae, and the new species resolved in a clade with the two living Todea species, which are now restricted to Australia, New Guinea, New Zealand, and southern Africa. • CONCLUSIONS: Todea amissa sp. nov. is the first record of Todea, living or fossil, in South America and only the second fossil record worldwide. The distribution of extant Todea on Gondwanan continents other than South America is broadly shared with other taxa from Laguna del Hunco, further indicating that a large component of this flora represents a Gondwanic biome that is no longer found on the South American continent.

The fossil record of Eucalyptus in Patagonia.

PREMISE OF THE STUDY: Herein, we name, describe, and illustrate new macrofossil material representing Eucalyptus (Myrtaceae: Myrtoideae, Eucalypteae) from the diverse early Eocene Laguna del Hunco (LH) flora of Chubut Province, Patagonia, Argentina. We explore the significance of these fossils in light of understanding the fossil record of eucalypts and the biogeography of the Eucalypteae. METHODS: Fossils representing vegetative and reproductive organs were collected from multiple LH localities over several field seasons. These specimens were prepared, photographed, and compared to extant Eucalyptus. Additional historical collections of Patagonian fossil Eucalyptus were also examined. KEY RESULTS: Vegetative and reproductive organs representing five different Eucalyptus taxa were identified in the LH paleoflora. One new taxon each representing leaves, flower buds, and infructescences with co-occurring, isolated capsules are described and named as new Eucalyptus species. Additionally, two flower types cf. Eucalyptus, represented by one specimen each, are illustrated and briefly described. The fossil species have unique characteristics that independently suggest each belongs within the Eucalypteae. The reproductive material is most similar morphologically to extant Eucalyptus, although it also shares many similarities to the closely related genus Corymbia. CONCLUSIONS: The LH fossil Eucalyptus material is among the few eucalypt macrofossils that have recently been named and described and are the oldest macrofossils that can presently be definitively ascribed to the Eucalypteae. They also represent the only credible description of Eucalyptus fossils occurring outside of Australasia and suggest a once broader geographic distribution for this group.