Evolutionary History of Lagomorphs in Response to Global Environmental Change

Although species within Lagomorpha are derived from a common ancestor, the distribution range and body size of its two extant groups, ochotonids and leporids, are quite differentiated. It is unclear what has driven their disparate evolutionary history. In this study, we compile and update all fossil records of Lagomorpha for the first time, to trace the evolutionary processes and infer their evolutionary history using mitochondrial genes, body length and distribution of extant species. We also compare the forage selection of extant species, which offers an insight into their future prospects. The earliest lagomorphs originated in Asia and later diversified in different continents. Within ochotonids, more than 20 genera occupied the period from the early Miocene to middle Miocene, whereas most of them became extinct during the transition from the Miocene to Pliocene. The peak diversity of the leporids occurred during the Miocene to Pliocene transition, while their diversity dramatically decreased in the late Quaternary. Mantel tests identified a positive correlation between body length and phylogenetic distance of lagomorphs. The body length of extant ochotonids shows a normal distribution, while the body length of extant leporids displays a non-normal pattern. We also find that the forage selection of extant pikas features a strong preference for C₃ plants, while for the diet of leporids, more than 16% of plant species are identified as C₄ (31% species are from Poaceae). The ability of several leporid species to consume C₄ plants is likely to result in their size increase and range expansion, most notably in Lepus. Expansion of C₄ plants in the late Miocene, the so-called ‘nature’s green revolution’, induced by global environmental change, is suggested to be one of the major ‘ecological opportunities’, which probably drove large-scale extinction and range contraction of ochotonids, but inversely promoted diversification and range expansion of leporids.     

First fossil fruits of Elaeocarpus (Elaeocarpaceae) in East Asia: Implications for phytogeography and paleoecology

The genus Elaeocarpus contains approximately 360 species and occurs in mesic forest communities from India, through to China, Southeast Asia, New Guinea, Australia, and New Caledonia. Elaeocarpus fossils are best known from the Eocene to the Miocene of Australia and the late Pliocene–early Pleistocene of India, but have not been documented from East Asia before. Here we describe six new species of Elaeocarpus, E. nanningensis sp. nov. from the late Oligocene Yongning Formation of the Nanning Basin, E. presikkimensis sp. nov. from the Miocene Erzitang Formation of the Guiping Basin, E. prerugosus sp. nov., E. prelacunosus sp. nov., E. preserratus sp. nov., and E. preprunifolioides sp. nov. from the late Miocene Foluo Formation of the Nankang Basin in Guangxi, South China. This is the first reliable report for the genus occurring in East Asia, and the fossils indicate that Elaeocarpus had colonized this region by the late Oligocene and represented by a morphologically diverse group of species by the late Miocene. This sheds new insights into the timing and migration patterns of the genus in East Asia. Elaeocarpus is typically a rainforest genus occurring in mesic forests. Based on the habitat of their morphologically similar modern relatives we propose that these three sedimentary basins were warm and wet adjacent to mountainous regions with the evergreen or rain forests during the late Oligocene to Miocene.     

A new Middle Miocene tarsier from Thailand and the reconstruction of its orbital morphology using a geometric-morphometric method

Tarsius is an extant genus of primates endemic to the islands of Southeast Asia that is characterized by enormously enlarged orbits reflecting its nocturnal activity pattern. Tarsiers play a pivotal role in reconstructing primate phylogeny, because they appear to comprise, along with Anthropoidea, one of only two extant haplorhine clades. Their fossils are extremely rare. Here, we describe a new species of Tarsius from the Middle Miocene of Thailand. We reconstructed aspects of its orbital morphology using a geometric-morphometric method. The result shows that the new species of Tarsius had a very large orbit (falling within the range of variation of modern Tarsius) with a high degree of frontation and a low degree of convergence. Its relatively divergent lower premolar roots suggest a longer mesial tooth row and therefore a longer muzzle than in extant species. The new species documents a previous unknown Miocene group of Tarsius, indicating greater taxonomic diversity and morphological complexity during tarsier evolution. The current restriction of tarsiers to offshore islands in Southeast Asia appears to be a relatively recent phenomenon.     

Biogeography of cedrela (meliaceae, sapindales) in central and South america

Dated phylogenies have helped clarify the complex history of many plant families that today are restricted to the world's tropical forests, but that have Eocene, Oligocene, and Miocene fossils from the northern hemisphere. One such family is the Meliaceae. Here we infer the history of the neotropical Meliaceae genus Cedrela (17 species), the sister clade of which today is restricted to tropical Asia. Sequences from the nuclear ribosomal spacer region and five plastid loci obtained for all ingroup species and relevant outgroups were used to infer species relationships and for molecular-clock dating under two Bayesian relaxed clock models. The clock models differed in their handling of rate autocorrelation and sets of fossil constraints. Results suggest that (1) crown group diversification in Cedrela started in the Oligocene/Early Miocene and intensified in the Late Miocene and Early Pliocene, and (2) Central American Cedrela species do not form a clade, implying reentry into Central America after the closure of the Panamanian Isthmus. At present, Cedrela is distributed in both dry and humid habitats, but morphological features suggest an origin in dry forest under seasonal climates, fitting with Miocene and Pliocene Cedrela fossils from deciduous forests.     

云南禄丰古猿地点的松鼠类化石

记述了云南禄丰晚中新世石灰坝古猿地点发现的松鼠科化石。禄丰石灰坝动物群的松鼠动物共有 7属 7种 :地松鼠Sciurotamiaswangisp .nov .,树松鼠Tamiopssp .、Callosciurussp .、Dremomysprimitivussp .nov .和飞松鼠Miopetauristaasiaticasp .nov .、Hylopetodondianensegen .etsp.nov.、Pteromyinaegen.etsp .indet.。该动物群松鼠类动物的组成以树松鼠和飞松鼠为主 ,反映了较为湿润的热带—亚热带森林环境。在动物地理上 ,其成员几乎局限于东南亚分布 ,具有浓厚的现代东洋界色彩     

Systematics and evolutionary significance of the small Abrocomidae from the early Miocene of southern South America

Octodontoidea is the most species-rich clade among hystricomorph rodents, and has a fossil record going back to at least the late Oligocene. Affinities of fossils previous to the late Miocene differentiation of the extant families Abrocomidae, Echimyidae and Octodontidae are controversial, essentially because these fossils may share few apomorphies with modern species. In fact, pre-late Miocene representatives of Abrocomidae had not been recognised until very recently. Here we revise the early Miocene genus Acarechimys, originally assigned to Echimyidae, and alternatively to stem Octodontoidea or to Octodontidae. A systematic and parsimony-based phylogenetic analysis of the species traditionally included in Acarechimys showed that this genus is part of stem Abrocomidae. These results are primarily supported by morphology of the mandible and lower molars. Acarechimys is here restricted to three species, A. minutus, A. pulchellus and Acarechimys pascuali sp. nov., while another species, A. constans, is here transferred to a new abrocomid genus. The remaining species were nested within Octodontidae. According to these results, Abrocomidae might have been as diverse as its sister clade Octodontidae-Echimyidae during the late Oligocene–early Miocene. Extinction of this diversity would have resulted in marked loss of evolutionary history, with extant abrocomids being currently restricted to late-diverged euhypsodont representatives.     

Flightless scaly‐tailed squirrels never learned how to fly: A reappraisal of Anomaluridae phylogeny

Anomaluroidea, commonly known as the “scaly‐tailed squirrels,” are an emblematic group of tropical African mammals that includes gliding forms. The family Anomaluridae was until recently represented by three genera: the flying scaly‐tailed squirrels (Anomalurus), the flying mouse (Idiurus) and the flightless scaly‐tailed squirrels (Zenkerella). Idiurus and Zenkerella have long been grouped into the Zenkerellinae subfamily, and Zenkerella was interpreted as a rare case of evolutionary reversal to non‐gliding lifestyle. Recent studies have demonstrated that Zenkerella is sister to all other modern anomalurids, and represents in fact the monogeneric family Zenkerellidae. The Anomalurus genus was split into Anomalurus and Anomalurops, but no study has ever considered all Anomalurus species together in a phylogeny to test the status of Anomalurops. Here, we used mitogenomic next‐generation sequencing to infer the phylogenetic relationships among all extant anomalurids and to estimate their divergence ages. We found that the arboreal Zenkerella is the sister group of all extant gliding anomalurids (Idiurus and Anomalurus). We confirmed that Anomaluroidea only evolved the gliding adaptation once. A comparison based on morphological traits indicates that Zenkerella harbours several unique morphological features. We propose new morphological characters for the novel classification of modern Anomaluroidea, which includes the families Zenkerellidae and Anomaluridae. Using different calibration schemes, we demonstrated that classical dating methods relying only on mitogenomes provide rather young Miocene estimates between Zenkerellidae and the Anomaluridae. The use of published nuclear genes, internal calibrations and tip dating converged towards an Eocene split between gliding and non‐gliding scaly‐tailed squirrels, which is in agreement with the African fossil record. Finally, we provide the first exhaustive species‐level molecular phylogenetic inference for the genus Anomalurus. We found that Anomalurus beecrofti is the sister group of all other species of Anomalurus and branched off during the Miocene.     

New fossil leaves and fruits of Lauraceae from the Middle Miocene of Fujian,southeastern China differentiated using a cluster analysis

The fossil record of Lauraceae can be traced back to the Early Cretaceous of eastern Asia based on fossil flowers. Here, we refer a number of new occurrences of leaf and fruit fossils of Lauraceae from the Middle Miocene of Zhangpu, Fujian, China, to seven species. These data provide evidence supporting the fact that a diverse subtropical, or tropical, Lauraceae-dominated evergreen forest surrounded this region 15 million years ago (Mya). The Lauraceae fossils presented in this paper provide evidence for the evolution of this group as well as new materials that enable the study of the Fujian Province Neogene flora. The fossils described in this paper fill in the gaps in studies about Lauraceae pollen in the Middle Miocene from Fotan, Fujian, China. In addition, these fossils also enrich the Middle Miocene fossil records of Lauraceae in eastern Asia, especially improving the study of the macrostructures and reproductive organs of fossil Lauraceae from southern China. The similarity between fossil and modern fruits shows that during the Middle Miocene the fruit morphological of Lauraceae have changed very little. We also identify families where the fossils we report belong to their closest relatives and can be used to reconstruct the paleoenvironment of Fujian in the Middle Miocene.     

Northern Hemisphere megafossil of Dacrycarpus (Podocarpaceae) from the Miocene of South China and its evolutionary and paleoecological implications

The modern genus Dacrycarpus (Endl.) de Laub. of the family Podocarpaceae, containing nine species, is mainly distributed in tropical mountain rainforests of the southwestern Pacific region, ranging from New Zealand to low‐latitude Asia. This genus has abundant fossil records in both hemispheres, but all the known megafossils were limited to Australasia and South America. Here we report on Dacrycarpus guipingensis sp. nov. from the Miocene Erzitang Formation of Guangxi, South China. This is the first megafossil of Dacrycarpus in the Northern Hemisphere. The new species is represented by mummified dimorphic foliage, ovuliferous shoots, and a male cone with in situ pollen. It resembles the extant Dacrycarpus imbricatus (Blume) de Laub., which is common in rainforests from southern China and northern Myanmar to Fiji. This paper presents the first data on the anatomical structure of seed cone and exine ultrastructure of Dacrycarpus in situ pollen grains from a fossil material by using computed tomography scanning and ultrathin sectioning. For comparative purpose, data on the pollen morphology and ultrastructure were obtained for modern D. imbricatus for the first time. The D. guipingensis fossils strongly suggest the Miocene arrival of Dacrycarpus in Asia from the Southern Hemisphere. Based on the modern ecological niche and related fossil elements, this fossil locality was probably covered by conifer–broad‐leaved mountain rainforests during the Miocene.     

First record of non‐flying mammalian contributors to pollination in a tropical montane forest in Asia

This study aims to identify the flower visitors of Mucuna thailandica (Fabaceae), endemic plant species in montane forests in Thailand, to determine their potential pollinators. The genus Mucuna produces papilionaceous flowers and has an explosive flower‐opening step. Explosive opening rapidly exposes stamens and pistil from keel petals and releases pollen. The flower of this species depends completely on animals to perform this step, essential for pollination success. Using a camera trap survey, we revealed that non‐flying mammals, such as squirrels (Callosciurus sp.) and masked palm civets (Paguma larvata), opened flowers explosively. Thus, these mammals contribute to the pollination of M. thailandica. This is the first report of non‐flying mammals contributing to pollination in montane forests in tropical Asia.     

Cynocephalid dermopterans from the Palaeogene of South Asia (Thailand, Myanmar and Pakistan): systematic, evolutionary and palaeobiogeographic implications

Cynocephalid dermopterans (flying lemurs) are represented by only two living genera (Cynocephalus and Galeopterus), which inhabit tropical rainforests of South‐East Asia. Despite their very poor diversity and their limited distribution, dermopterans play a critical role in higher‐level eutherian phylogeny inasmuch as they represent together with Scandentia (tree‐shrew) the sister group of the Primates clade (Plesiadapiformes + Euprimates). However, unlike primates, for which the fossil record extends back to the early Palaeogene on all Holarctic continents and in Africa, the evolutionary history of the order Dermoptera sensu stricto (Cynocephalidae) has so far remained undocumented, with the exception of a badly preserved fragment of mandible from the late Eocene of Thailand (Dermotherium major). In this paper, we described newly discovered fossil dermopterans (essentially dental remains) from different regions of South Asia (Thailand, Myanmar, and Pakistan) ranging from the late middle Eocene to the late Oligocene. We performed microtomographic examinations at the European Synchrotron Radiation Facility (ESRF, Grenoble, France) to analyse different morphological aspects of the fossilized jaws. The abundant material from the late Oligocene of Thailand (Nong Ya Plong coal mine) allows us to emend the diagnosis of the genus Dermotherium and to describe a new species: Dermotherium chimaera sp. n. This species exhibits an interesting mosaic of plesiomorphic cynocephalid characters shared with Cynocephalus and Galeopterus, and as such, it probably documents a form close to the ancestral morphotype from which the two extant forms are derived (supported by cladistic assessment of the dental evidence). The discovery of Palaeogene cynocephalids is particularly significant since it attests to the great antiquity of the order Dermoptera in Asia, and besides, it provides the first spatio‐temporal glimpse into the evolutionary history of that enigmatic mammal group. In that respect, these fossils testify to a long history of endemism in South Asia for dermopterans, and demonstrate that their modern geographic restriction in south‐eastern Asia is clearly a relictual distribution. Cynocephalids had a more widespread distribution during the Palaeogene, which extended from the Indian subcontinent (the rafting Greater India) to South‐East Asia. Their subsequent extinction on the Indian subcontinent was probably mediated by the major palaeogeographic and geomorphologic events related to the India‐Eurasia collision (retreat of the Paratethys Sea, formation of orogenic highlands) that have strongly affected the climate of South Asia at the end of the Oligocene.     

Historical Biogeography and Body Form Evolution of Ground Squirrels (Sciuridae: Xerinae)

Xerinae is the most species-rich subfamily of the Sciuridae (Rodentia). This group of animals has a long complex evolutionary history, which witnessed severe environmental changes. In this paper, a comprehensive approach integrating information from fossil records, morphological, molecular and geographical data of extant species, and events of paleoclimate and paleogeography, were used to explore the evolutionary processes in the Xerinae. Xerinae probably originated in Eurasia around the early Oligocene, and dispersed to Africa via the Africa-Eurasia Land Bridge on two occasions during the Miocene, and subsequently evolved into the Protoxerini and African Xerini. The tribe Marmotini derived from a Eurasian ancestor and thrived in North America. Tamias re-occupied Eurasia in the early Miocene, while the distributions of Marmota and ‘Spermophilus’ genus-groups were restricted to North America at least until the late Miocene. Global cooling and the emergence of grass-dominated ecosystems from 15 Ma are likely to be the main causes for the radiation of Marmotini. The body form of Xerinae displays an allometric mode of evolution, with ground-living taxa, such as Marmota, Cynomys and Xerus notably enlarged, while Tamias has remained slim in body form. To cope with the global environmental changes, particularly the global cooling induced forest degradation and grassland expansion in the late Miocene, most Marmotini developed into true ground squirrels with short tails. The slim body adaptation in Tamias may be related to competition from tree squirrels, or their hoarding behavior, the latter helping them to cope with cold winter.     

A Review of the Fossil Record of the Genus Itea (Iteaceae, Saxifragales) with Comments on its Historical Biogeography

Itea is a genus of about 20 species of trees and shrubs that are today native to southeastern North America, eastern Asia, and eastern Africa. In this paper, I review the fossil record of Itea, which is based on four types of fossils: diporate, psilate pollen attributed to Itea or the dispersed pollen genus Iteapollis; carpofossils representing fruits and seeds attributed to Itea europaea; flowers preserved in amber and assigned to Adenanthemum iteoides; and leaf impressions attributed to Itea. The distributions of these fossils indicate that Itea was present in western North America from the early Eocene to Miocene, in eastern North America beginning no later than the early Miocene, and in western Eurasia from the late Eocene to Pliocene. Only one datapoint is known from eastern Asia; it is early Miocene in age. Based on the fossil record, it can be inferred that Itea crossed between continents over both the Bering Land Bridge and North American Land Bridge, and that it reached Africa from Europe via Anatolia. Thus, it is predicted that the sole extant North American species, I. virginica, may be most closely related to the sole extant African species, I. rhamnoides. The potential application of Itea fossils to calibrating phylogenetic trees generated from molecular sequence data is also discussed.     

Role of the Siberian flying squirrel as an umbrella species for biodiversity in northern boreal forests

One of the potentially useful indirect shortcut methods in biodiversity conservation is the umbrella species concept. An umbrella species can be seen relatively demanding for the size of the area and probably also for certain habitat types: conservation management for the umbrella species would thus encompass other species preferring similar habitats but with smaller area requirements. As such, it has a comprehensive spatial aspect for landscape planning. We tested the role of the Siberian flying squirrel (Pteromys volans) as an umbrella species for wood dependent species among red-listed and old-growth forest associated polypores, epiphytic lichens and beetles. Flying squirrels inhabit home ranges of several to tens of hectares, and prefer mature spruce-dominated (Picea abies) mixed forests, which often have high amounts of dead wood. We carried out species surveys and trappings during 1 year from 20 mature spruce-dominated forest stands (altogether 162 ha), of which 12 were occupied by the flying squirrel. The amount of dead wood was higher in occupied stands than in unoccupied stands. We also found a tendency for a higher number of species and number of records in occupied stands, a relationship mostly due to the polypore species. The presence of the flying squirrel may reflect the habitat availability for species depending on dead and living wood, and assist in site selection of conservation areas. We suggest that the flying squirrel has potential as an umbrella species to partly enhance maintenance of biodiversity in northern boreal forests in Finland.     

Fossil mushrooms from Miocene and Cretaceous ambers and the evolution of Homobasidiomycetes

Two species of fossil mushrooms that are similar to extant Tricholomataceae are described from Cretaceous and Miocene ambers. Archaeomarasmius leggetti gen. et sp. nov., from mid-Cretaceous amber of New Jersey, resembles the extant genera Marasmius and Marasmiellus. Two fruiting bodies of Archaeomarasmius were found. One consists of a complete pileus with stipe, and the other consists of a fragment of a pileus. The latter was accidentally exposed, and zxsubsequently was used for molecular systematics studies (attempts to amplify ribosomal DNA were unsuccessful) and electron microscopy. The spores are smooth and broadly elliptic with a distinct hilar appendage. Protomycena electra gen. et sp. nov., which is represented by a single complete fruiting body from Miocene amber of the Dominican Republic, is similar to the extant genus Mycena. Based on comparison to extant Marasmieae and Myceneae, Archaeomarasmius and Protomycena were probably saprophytes of leaf litter or wood debris. The poor phylogenetic resolution for extant homobasidiomycetes limits the inferences about divergence times of homobasidiomycete clades that can be drawn from Archaeomarasmius and Protomycena. The ages of these fossils lend support to hypotheses that the cosmopolitan distributions of certain mushroom taxa could be due to fragmentation of ancestral ranges via continental drift. Anatomical and molecular studies have suggested that there has been extensive convergence and parallelism in the evolution of homobasidiomycete fruiting body form. Nevertheless, the striking similarity of these fossils to extant forms suggests that in certain lineages homobasidiomycete macroevolution has also involved long periods during which there has been little morphological change.     

Strongyloides robustus and the northern sympatric populations of northern (Glaucomys sabrinus) and southern (G. volans) flying squirrels

Within North America, northern (Glaucomys sabrinus) and southern (Glaucomys volans) flying squirrels occupy distinct ranges with limited overlap. Sympatry in northern latitudes coincides with northern hardwood vegetation from Minnesota to New England. Strongyloides robustus is an intestinal parasite that infects both species but appears to be deleterious only to northern flying squirrels. As a result, S. robustus could be a critical determinant of flying squirrel population characteristics in at least some areas of sympatry. However, cold weather could potentially limit the distribution of S. robustus in northern climates. Therefore, we assessed fecal samples from both flying squirrel species to determine the presence of the nematode in Wisconsin. Strongyloides robustus was found in 12 flying squirrel scat samples and infected 52% of southern flying squirrels and 11% of northern flying squirrels. Prevalence of S. robustus infection for northern flying squirrels was substantially lower than previously reported from more southern regions. This is the northernmost documentation of S. robustus in flying squirrels and the first documentation of S. robustus parasitizing flying squirrels in Wisconsin.     

Chaneya, a New Genus of Winged Fruit from the Tertiary of North America and Eastern Asia

A new genus is recognized on the basis of wind-dispersed fruits from the Eocene of western North America and Miocene of eastern Asia. The fruits consist of an accrescent hypogynous calyx of five obovate sepals and one or more globose fruit bodies. Although the fossils were formerly placed in the extant genera Porana (Convolvulaceae) and Astronium (Anacardiaceae), our investigation of numerous specimens from several floras in the western United States (e.g., Florissant, Green River, Clarno) and Canada (Whipsaw Creek, British Columbia) and the Yilan and Shanwang floras of China reveals unique characters that indicate that the fossils are a distinct genus, which we name Chaneya. Unlike Porana and Astronium, the fossil calyces have stomata that are longitudinally aligned, and early stages of fruit development show a gynoecium of five apocarpous carpels, of which only one or two usually enlarge at maturity. Precise systematic placement of the fossil genus is uncertain, but similarities to the extant Picrasma of the Simaroubaceae are suggestive of possible affinities. Two species are recognized: Chaneya tenuis (Lesq.) comb. nov., from the Eocene of western North America and northeastern China, and Chaneya kokangensis (Endo) comb. nov., from the Miocene of eastern Asia.     

A dated phylogeny of Lardizabalaceae reveals an unusual long-distance dispersal across the Pacific Ocean and the rapid rise of East Asian subtropical evergreen broadleaved forests in the late Miocene

Temperate South American–Asian disjunct distributions are the most unusual in organisms, and challenging to explain. Here, we address the origin of this unusual disjunction in Lardizabalaceae using explicit models and molecular data. The family (c.40 species distributed in ten genera) also provides an opportunity to explore the historical assembly of East Asian subtropical evergreen broadleaved forests, a typical and luxuriant vegetation in East Asia. DNA sequences of five plastid loci of 42 accessions representing 23 species of Lardizabalaceae (c. 57.5% of estimated species diversity), and 19 species from the six other families of Ranunculales, were used to perform phylogenetic analyses. By dating the branching events and reconstructing ancestral ranges, we infer that extant Lardizabalaceae dated to the Upper Cretaceous of East Asia and that the temperate South American lineage might have split from its East Asian sister group at c. 24.4 Ma. A trans-Pacific dispersal possibly by birds from East Asia to South America is plausible to explain the establishment of the temperate South American–East Asian disjunction in Lardizabalaceae. Diversification rate analyses indicate that net diversification rates of Lardizabalaceae experienced a significant increase around c. 7.5 Ma. Our findings suggest that the rapid rise of East Asian subtropical evergreen broadleaved forests occurred in the late Miocene, associated with the uplift of the Tibetan Plateau and the intensified East Asian monsoon, as well as the higher winter temperature and atmospheric CO₂ levels.     

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.     

Molecular evidence for an Asian origin and a unique westward migration of species in the genus Castanea via Europe to North America

The genus Castanea (Fagaceae) is widely distributed in the deciduous forests of the Northern Hemisphere. The striking similarity between the floras of eastern Asia and those of eastern North America and the difference in chestnut blight resistance among species has been of interest to botanists for a century. To infer the biogeographical history of the genus, the phylogeny of Castanea was estimated using DNA sequence data from different regions of the chloroplast genome. Sequencing results support the genus Castanea as a monophyletic group with Castanea crenata as basal. The three Chinese species form a strongly supported sister clade to the North American and European clade. A unique westward expansion of extant Castanea species is hypothesized with Castanea originating in eastern Asia, an initial diversification within Asia during the Eocene followed by intercontinental dispersion and divergence between the Chinese and the European/North American species during the middle Eocene and a split between the European and the North American species in the late Eocene. The differentiation within North America and China might have occurred in early or late Miocene. The North America species are supported as a clade with C. pumila var. ozarkensis, the Ozark chinkapin, as the basal lineage, sister to the group comprising C. pumila var. pumila, the Allegheny chinkapin, and Castanea dentata, the American chestnut. Morphological evolution of one nut per bur in the genus may have occurred independently on two continents.