North Atlantic Land Bridge Research Articles

Species Diversity, Host Association, and Evolutionary History of Cronartium: An Important Global Fungal Pathogen to Trees.

Pine stem rust, the most damaging and widespread forest disease occurring in pine trees in the Northern Hemisphere, is primarily caused by Cronartium species (Pucciniales, Melampsorineae). While the phylogenetic relationships of major Cronartium species have been largely elucidated, there is limited understanding of their species diversity and the evolutionary processes shaping their distribution patterns. In this work, we performed broad sampling and sequencing of Cronartium taxa in China together with additional sequence data and other accessions in NCBI to investigate the diversification and to estimate the divergence time of major evolutionary events in this genus. Molecular dating analysis suggested that the divergence of the genus Cronartium probably was around 91.78 Ma during the Upper Cretaceous. It is believed that Cronartium species may have originated in Asia and North America, with intercontinental dispersals occurring primarily during the Middle Eocene, Middle Miocene, and Pliocene. These dispersal events likely took place through the North Atlantic Land Bridge, the De Geer Route, and the Bering Land Bridge, and subsequently diverged through sporadic dispersal and vicariance events. Furthermore, our analysis of host associations revealed that the diversification of Cronartium species was correlated with their telial-hosts, and some species may have experienced host jump events, indicating a complex interplay between host specificity and pathogen-host interaction during Cronartium evolution.

Phylogenomics of Tetraopes longhorn beetles unravels their evolutionary history and biogeographic origins

Tetraopes longhorn beetles are known for their resistance to milkweed plant toxins and their coevolutionary dynamics with milkweed plants (Asclepias). This association is considered a textbook example of coevolution, in which each species of Tetraopes is specialized to feed on one or a few species of Asclepias. A major challenge to investigating coevolutionary hypotheses and conducting molecular ecology studies lies in the limited understanding of the evolutionary history and biogeographical patterns of Tetraopes. By integrating genomic, morphological, paleontological, and geographical data, we present a robust phylogeny of Tetraopes and their relatives, using three inference methods with varying subsets of data, encompassing 2–12 thousand UCE loci. We elucidate the diversification patterns of Tetraopes species across major biogeographical regions and their colonization of the American continent. Our findings suggest that the genus originated in Central America approximately 21 million years ago during the Miocene and diversified from the Mid-Miocene to the Pleistocene. These events coincided with intense geological activity in Central America. Additionally, independent colonization events in North America occurred from the Late Miocene to the early Pleistocene, potentially contributing to the early diversification of the group. Our data suggest that a common ancestor of Tetraopini migrated into North America, likely facilitated by North Atlantic land bridges, while closely related tribes diverged in Asia and Europe during the Paleocene. Establishing a robust and densely sampled phylogeny of Tetraopes beetles provides a foundation for investigating micro- and macroevolutionary phenomena, including clinal variation, coevolution, and detoxification mechanisms in this ecologically important group.

Eurasian drylands are both evolutionary cradles and museums of Nitrariaceae diversity

AbstractAimDrylands cover about 41% of Earth's land surface and are home to fragile biota with high levels of endemism. Two hypothetical models, i.e., cradle and museum, have been proposed to account for present‐day species diversity in an ecoregion or biome. We investigated macroevolutionary patterns to test these two different models in Nitrariaceae, a characteristic component of the Eurasian dryland ecosystem. We also used this family to explore the intercontinental disjunct distribution pattern between the deserts of Eurasia and western North America, known as the Madrean–Tethyan disjunction.LocationDrylands in the Northern Hemisphere.TaxonNitrariaceae (Sapindales, Angiosperms).MethodWe sampled all 16 of the currently recognized extant species of Nitrariaceae and 59 species from the eight other families of Sapindales. A fossil‐calibrated phylogeny was generated using 12 fossil constraints. The ancestral range and climate niche of Nitrariaceae were reconstructed, and diversification rates were estimated.ResultsThe most recent common ancestor of Nitrariaceae likely inhabited arid habitats with low rainfall in the temperate zone in the Late Cretaceous, which geographically corresponds to present‐day Central Asia. The western North American Peganum mexicanum split from its Central Asian sister group at approximately 39 Ma. Net diversification rates of Nitrariaceae experienced a significant increase around 11 Ma. Within Sapindales, at least seven arid species originated markedly prior to the Miocene.Main ConclusionsThe North Atlantic land bridge and global cooling climate in the Late Eocene might have driven the formation of the present‐day disjunct distribution of Nitrariaceae between arid Central Asia and western North America. Nitrariaceae originated in the Late Cretaceous and exhibited long‐term climate niche conservatism, but experienced a rapid diversification in the late Miocene of Eurasia in response to orogenetic and climatic changes. These findings suggest that Eurasian drylands serve as both evolutionary cradles and museums for the diversity of Nitrariaceae and likely for other arid‐adapted lineages.

Evidence for the evolutionary history and diversity of fossil sweetgums: leaves and associated capitate reproductive structures of Liquidambar from the Eocene of Hainan Island, South China

AbstractExtant species of Liquidambar L. exhibit a disjunct distribution between western and eastern Asia and eastern North America to Central America, with the highest species diversity being in China. In this study, two new species of Liquidambar are described from the Eocene of Hainan Island, South China: L. hainanensis on basis of the leaf fossils, and L. ovoidea based on compressions of infructescences. The co‐occurrences of L. hainanensis leaves, associated infructescences of L. ovoidea and dispersed pantoporate pollen grains have the combination of morphological features peculiar to the genera Liquidambar and former Semiliquidambar and Altingia. This is considered further palaeobotanical justification for the placement of these three genera into a single genus, Liquidambar, proposed earlier based on molecular markers. Our data provide evidence for the occurrence of an ancestral polymorphic group of Liquidambar species (L. maomingensis with associated capitate infructescences, L. bella, L. hainanensis and L. ovoidea) during the Eocene in South China, and corroborate the view that South China could have been a centre of Liquidambar speciation during the Eocene. The morphological similarity of L. hainanensis leaves to those of the extant species L. orientalis from Western Asia and the North American L. styraciflua may support the importance of both the North Atlantic Land Bridge and the Bering Land Bridge for the dispersal of Liquidambar. Analysis of fossil species of Liquidambar from eastern Asia also contributes to further understanding of patterns in the taxonomic diversity and evolutionary history of this genus.

Target sequence capture data shed light on the deeper evolutionary relationships of subgenus Chamaecerasus in Lonicera (Caprifoliaceae)

The genus Lonicera L. is widely distributed in the north temperate zone and is well-known for its high species richness and morphological diversity. Previous studies have suggested that many sections of Lonicera are not monophyletic and phylogenetic relationships within the genus are still poorly resolved. In this study, we sampled 37 accessions of Lonicera, covering four sections of subgenus Chamaecerasus plus six outgroup taxa, to recover the main clades of Lonicera based on sequences of nuclear loci generated by target enrichment and cpDNA from genome skimming. We found extensive cytonuclear discordance across the subgenus. Both nuclear and plastid phylogenetic analyses supported subgenus Chamaecerasus sister to subgenus Lonicera. Within subgenus Chamaecerasus, sections Isika and Nintooa were each polyphyletic. Based on the nuclear and chloroplast phylogenies, we propose to merge Lonicera korolkowii into section Coeloxylosteum and Lonicera caerulea into section Nintooa. In addition, Lonicera is estimated to have originated in the mid Oligocene (26.45 Ma). The stem age of section Nintooa was estimated to be 17.09 Ma (95% HPD: 13.30–24.45). The stem age of subgenus Lonicera was estimated to be 16.35 Ma (95% HPD: 14.12–23.66). Ancestral area reconstruction analyses indicate that subgenus Chamaecerasus originated in East Asia and Central Asia. In addition, sections Coeloxylosteum and Nintooa originated in East Asia, with subsequent dispersals into other areas. The aridification of the Asian interior likely promoted the rapid radiation of sections Coeloxylosteum and Nintooa within this region. Moreover, our biogeographic analysis fully supports the Bering and the North Atlantic Land Bridge hypotheses for the intercontinental migrations in the Northern Hemisphere. Overall, this study provides new insights into the taxonomically complex lineages of subgenus Chamaecerasus and the process of speciation.

Cenozoic migration of a desert plant lineage across the North Atlantic.

Previous paleobotanical work concluded that Paleogene elements of the sclerophyllous subhumid vegetation of western Eurasia and western North America were endemic to these disjunct regions, suggesting that the southern areas of the Holarctic flora were isolated at that time. Consequently, molecular studies invoked either parallel adaptation to dry climates from related ancestors, or long-distance dispersal in explaining disjunctions between the two regions, dismissing the contemporaneous migration of dry-adapted lineages via land bridges as unlikely. We report Vauquelinia (Rosaceae), currently endemic to western North America, in Cenozoic strata of western Eurasia. Revision of North American fossils previously assigned to Vauquelinia confirmed a single fossil-species of Vauquelinia and one of its close relative Kageneckia. We established taxonomic relationships of fossil-taxa using diagnostic character combinations shared with modern species and constructed a time-calibrated phylogeny. The fossil record suggests that Vauquelinia, currently endemic to arid and subdesert environments, originated under seasonally arid climates in the Eocene of western North America and subsequently crossed the Paleogene North Atlantic land bridge (NALB) to Europe. This pattern is replicated by other sclerophyllous, dry-adapted and warmth-loving plants, suggesting that several of these taxa potentially crossed the North Atlantic via the NALB during Eocene times.

An updated phylogeny, biogeography, and PhyloCode-based classification of Cornaceae based on three sets of genomic data.

A major goal of systematic biology is to uncover the evolutionary history of organisms and translate that knowledge into stable classification systems. Here, we integrate three sets of genome-wide data to resolve phylogenetic relationships in Cornaceae (containing only Cornus s. l.), reconstruct the biogeographic history of the clade, and provide a revised classification using the PhyloCode to stabilize names for this taxonomically controversial group. We conducted phylogenetic analyses using 312 single-copy nuclear genes and 70 plastid genes from Angiosperms353 Hyb-Seq, plus numerous loci from RAD-Seq. We integrated fossils using morphological data and produced a dated phylogeny for biogeographical analysis. A well-resolved, strongly supported, comprehensive phylogeny was obtained. Biogeographic analyses support an origin and rapid diversification of Cornus into four morphologically distinct major clades in the Northern Hemisphere (with an eastern Asian ancestor) during the late Cretaceous. Dispersal into Africa from eastern Asia likely occurred along the Tethys Seaway during the Paleogene while dispersal into South America likely occurred during the Neogene. Diversification within the Northern Hemisphere likely involved repeated independent colonization of new areas during the Paleogene and Neogene along the Bering Land Bridge, the North Atlantic Land Bridge, and the Tethys Seaway. Thirteen strongly supported clades were named following the PhyloCode. Our study provides an example of integrating genomic and morphological data to produce a robust, explicit species phylogeny that includes fossil taxa, which we translate into an updated classification scheme using the PhyloCode to stabilize names. This article is protected by copyright. All rights reserved.

The Hoatzin

Joel Cracraft introduces the Hoatzin (Opisthocomus hoazin), an odd and enigmatic bird that defies classification.

The significance of recent diversification in the Northern Hemisphere in shaping the modern global flora revealed from the herbaceous tribe of Rubieae (Rubiaceae)

The global herbaceous flora is probably shaped by both ancient and/or recent diversification, companied with the impacts from geographic differences between the Northern and Southern Hemispheres. Therefore, its biogeographic pattern with respect to temporal and spatial divergence is far from full understanding. Tribe Rubieae, the largest herbaceous tribe in the woody-dominant Rubiaceae, provides an excellent opportunity for studying the macroevolution of worldwide colonization. Here, we aim to reconstruct the evolutionary history of Rubieae with regard to climate fluctuation and geological history in the Cenozoic. A total of 204 samples of Rubieae representing all the distribution areas of the tribe were used to infer its phylogenetic and biogeographic histories based on two nrDNA and six cpDNA regions. The ancestral area of Rubieae was reconstructed using a time-calibrated phylogeny in RASP and diversification rates were inferred using Bayesian analysis of macroevolutionary mixtures (BAMM). Our results show Rubieae probably originated in European region during the middle Oligocene, with the two subtribes separating at 26.8 million years ago (Ma). All the genera in Rubieae formed separate clades between 24.79 and 6.23 Ma. The ancestral area of the subtribe Rubiinae was the Madrean-Tethyan plant belt and the North Atlantic land bridge (NALB) provided passage between North America and Europe for Rubiinae. The subtribe Galiinae clade originated in Europe/central Asia during the late Oligocene. Two diversification shifts were detected within Rubieae in the late Neogene. Most extant Rubieae species diverged recently during the Neogene within clades that generally were established during the late Paleogene. The tribe shows complex migration/dispersal patterns within the North Hemisphere combined with multiple recent dispersals into Southern Hemisphere. Our results highlighted the important role of recent biogeographic diversification in the Northern Hemisphere in shaping the modern global herbaceous flora during the latest and rapid worldwide expansion in the Neogene.

Phylogenomics and biogeography of Catalpa (Bignoniaceae) reveal incomplete lineage sorting and three dispersal events

Catalpa Scop. (Bignoniaceae) is a small genus (8 spp.) of trees that is disjunctly distributed among eastern Asia, eastern United States, and the West Indies. Catalpa bears beautiful inflorescences and have been cultivated as important ornamental trees for landscaping, gardening, and timber. However, the phylogenetic relationships and biogeographic history of the genus have remained unresolved. In this study, we used a large genomic dataset that includes data from the chloroplast (plastomes), and nuclear genomes (ITS and 5,759 single-copy nuclear genes) to reconstruct phylogenetic relationship within Catalpa, test interspecific gene flow events within the genus, and infer its biogeographic history. Our phylogenetic results indicate that Catalpa is monophyletic containing two main clades, section Catalpa and section Macrocatalpa. Section Catalpa is further divided into three subclades. While most relationships are congruent between the chloroplast and nuclear datasets, the position of C. ovata differs, likely due to incomplete lineage sorting. Interspecific gene flow events include C. bungei s.s. with vectors of inheritance from C. duclouxii and C. fargesii, supporting a combination of these three species and recognizing a broadly circumscribed C. bungei s.l. Our biogeographic study suggests three main dispersal events, two of which occurred during the Oligocene. The first dispersal event occurred from southwestern North America and Mexico into the Greater Antilles giving rise to the ancestor of the section of Macrocatalpa. The second dispersal event also occurred from southwestern North America and Mexico, but led to central and northern North America, subsequently reaching China through the Bering land bridge, and also reaching Europe through the North Atlantic land bridge. The third dispersal event took place in the Miocene from China to North America and gave rise to a clade composed of C. bignonioides and C. speciosa. This study uses a phylogenomic approach and biogeographical methods to infer the evolutionary history of Catalpa, highlighting issues associated with gene tree discordance, and suggesting that incomplete lineage sorting likely played an important role in the evolutionary history of Catalpa.

Historical biogeography of the Southeast Asian and Malesian tribe Dissochaeteae (Melastomataceae)

AbstractThe region of Tropical Southeast Asia and the Malay Archipelago is a very appealing area for research due to its outstanding biodiversity, being one of the most species‐rich areas in the world with high levels of endemism, and due to its complex geological history. The high number of species in tribe Dissochaeteae (Melastomataceae) and their tendency to narrow endemism make the tribe an ideal group for examining biogeographic patterns. We sampled 58 accessions spread over 42 accepted and two undescribed species of the Dissochaeteae. Two nuclear (ETS, ITS) and four chloroplast regions (ndhF, psbK‐psbL, rbcL, rpl16) were used for divergence time estimation and ancestral area reconstruction. Results from the molecular dating analysis suggest that the diversity of Dissochaeteae in the Southeast Asian region resulted from a South American ancestor in the late Eocene. The ancestor of the Dissochaeteae might have migrated from South America to Southeast Asia via North America and then entered Eurasia over the North Atlantic land bridge during the Eocene. The origin and early diversification of the Dissochaeteae in Southeast Asia dates back to the middle Oligocene, and most of the genera originated during the Miocene. Indochina and Borneo are most likely the area of origin for the most recent common ancestor of the Dissochaeteae and for many of the early diverging clades of some genera within Southeast Asia.

Fossil-Informed Models Reveal a Boreotropical Origin and Divergent Evolutionary Trajectories in the Walnut Family (Juglandaceae).

Temperate woody plants in the Northern Hemisphere have long been known to exhibit high species richness in East Asia and North America and significantly lower diversity in Europe, but the causes of this pattern remain debated. Here, we quantify the roles of dispersal, niche evolution, and extinction in shaping the geographic diversity of the temperate woody plant family Juglandaceae (walnuts and their relatives). Integrating evidence from molecular, morphological, fossil, and (paleo)environmental data, we find strong support for a Boreotropical origin of the family with contrasting evolutionary trajectories between the temperate subfamily Juglandoideae and the tropical subfamily Engelhardioideae. Juglandoideae rapidly evolved frost tolerance when the global climate shifted to ice-house conditions from the Oligocene, with diversification at high latitudes especially in Europe and Asia during the Miocene. Subsequent range contraction at high latitudes and high levels of extinction in Europe driven by global cooling led to the current regional disparity in species diversity. Engelhardioideae showed temperature conservatism while adapting to increased humidity, tracking tropical climates to low latitudes since the middle Eocene with comparatively little diversification, perhaps due to high competition in the tropical zone. The biogeographic history of Juglandaceae shows that the North Atlantic land bridge and Europe played more critical roles than previously thought in linking the floras of East Asia and North America, and showcases the complex interplay among climate change, niche evolution, dispersal, and extinction that shaped the modern disjunct pattern of species richness in temperate woody plants. [Boreotropical origin; climatic niche evolution; disjunct distribution; dispersal; diversity anomaly; extinction; Juglandaceae.]

Western Tethys origin, tropical Asia and tropical America disjunction in Berchemia and reinstatement of Phyllogeiton (Rhamneae, Rhamnaceae)

AbstractDespite the well‐known biogeographic pattern in the Northern Hemisphere of disjunct distributions in plants between eastern Asia and North America, many details regarding the evolution of the disjunction between lineages of tropical Asia and tropical America remain poorly understood. Berchemia (Rhamnaceae), comprising ca. 32 species, is distributed predominantly in tropical regions of east to southeast Asia and North America. However, the phylogeny and biogeography of this genus are still not clear. Furthermore, fossils of the genus have been found in Europe, making it an ideal group to understand the biogeographical story of tropical disjunction in the Northern Hemisphere. With two nuclear (ETS, ITS) and three plastid (petA‐psbJ, psbA‐trnH, trnL‐F) DNA regions, we first reconstructed the phylogeny of Berchemia with Bayesian inference and maximum likelihood approaches. Our results indicated that Berchemia, excluding the African species B. discolor and B. zeyheri, which were placed into the reinstated Phyllogeiton, was well‐supported as monophyletic. Divergence times and ancestral areas were inferred using a Bayesian uncorrelated lognormal relaxed molecular clock model and Bayesian binary MCMC method, respectively. The core Berchemia likely originated in the Western Tethys during the middle Eocene, then formed the tropical Asia and tropical America disjunction during the Oligocene and further diversified in Asia from the early Miocene on. The formation and diversification of the core Berchemia likely resulted from a mixture of geologic events, such as the close of the Tethys Ocean, disappearance of the North Atlantic Land Bridges, uplift of the Qinghai‐Tibetan Plateau, and climatic events, such as the establishment and enhancement of Asian monsoons.

Historical biogeography of Acer L. (Sapindaceae): genetic evidence for Out-of-Asia hypothesis with multiple dispersals to North America and Europe

Biogeography is the study of where, when, and how modern species evolved and diversified. Acer L. (maple) is one of the most diverse and widespread genera in the Northern Hemisphere. It comprises 124–156 species in the world, approximately 80% species of Acer are native in Asia. The current diversity center of Acer is not congruent with the distribution of the oldest fossils of the genus. Therefore, we herein used 84 species and subspecies to reconstruct the phylogeny and investigate the biogeographic history of Acer using nuclear ITS and three cpDNA fragments (psbA-trnH spacer, rpl16 intron, and trnL-trnF spacer) with maximum likelihood, maximum parsimony, and Bayesian inference methods. The analyses showed that the current diversity center and the origin center of Acer is Asia. Additionally, the North American and Euro-Mediterranean species originated from multiple sources from Asia via the North Atlantic Land Bridge and the Bering Land Bridge, and intercontinental migration has mainly occurred since the Miocene. This study not only provides a novel insight of the origin and dispersal routes of Acer but also exemplifies how past climatic changes affect the diversification-rates of Northern Hemisphere forest trees.

Next generation DNA sequencing reveals allopolyploid origin of decaploid Isoëtes lacustris (Isoëtaceae)

Abstract Isoetes L. is a cosmopolitan genus comprising about 200 species, almost half of them being allo- or autopolyploids. We investigated the origin of decaploid I. lacustris using next generation sequencing (NGS). We sequenced the second intron of LEAFY (LFYint2) and analysed the morphology of seven samples of I. lacustris from five localities from East Europe and West Siberia. We have shown that I. lacustris is an allopolyploid having in its genome the subgenomes of the North American diploid I. prototypus, tetraploid I. tuckermanii (which contains subgenomes of diploid I. viridimontana and unknown species), and one more unknown diploid progenitor. NGS showed high reproducibility, demonstrating the same sets of LFYint2 copies in all the samples. The potential fifth subgenome has not been found, most likely due to a loss of the LEAFY gene as a result of subgenome reduction, as is characteristic of polyploids. These data imply that the ancestor of I. lacustris most likely originated in the north-east of North America (New England and Acadian region) where I. prototypus, I. tuckermanii and I. viridimontana co-occur, and that I. lacustris then spread to Eurasia via the North Atlantic Land Bridge. NGS-based amplicon sequencing has the potential to evaluate the ratio of frequency of different copies and to distinguish allopolyploidy and autopolyploidy (if the PCR efficiency of each of the copies is taken into account). This is especially useful, given that both play a prominent role in Isoetes evolution. We also demonstrate that widely adopted cloning of LFYint2 in Isoetes leads to biased results due to the amplification errors.

Phylogenomics, biogeography, and evolution of the blue‐ or white‐fruited dogwoods (Cornus)—Insights into morphological and ecological niche divergence following intercontinental geographic isolation

AbstractThe eastern Asian (EA)–eastern North American (ENA) floristic disjunction represents a major pattern of phytogeography of the Northern Hemisphere. Despite 20 years of studies dedicated to identification of taxa that display this disjunct pattern, its origin and evolution remain an open question, especially regarding post‐isolation evolution. The blue‐ or white‐fruited dogwoods (BW) are the most species‐rich among the four major clades of Cornus L., consisting of ~35 species divided into three subgenera (subg. Yinquania, subg. Mesomora, and subg. Kraniopsis). The BW group provides an excellent example of the EA–ENA floristic disjunction for biogeographic study due to its diversity distribution centered in eastern Asia and eastern North America, yet its species relationships and delineation have remained poorly understood. In this study, we combined genome‐wide markers from RAD‐seq, morphology, fossils, and climate data to understand species relationships, biogeographic history, and ecological niche and morphological evolution. Our phylogenomic analyses with RAxML and MrBayes recovered a strongly supported and well‐resolved phylogeny of the BW group with three intercontinental disjunct clades in EA and ENA or Eurasia and North America, of which two are newly identified within subg. Kraniopsis. These analyses also recovered a potential new species but failed to resolve relationships within the C. hemsleyi–C. schindleri complex. In an effort to develop an approach to reduce computation time, analysis of different nodal age settings in treePL suggests setting a node's minimum age constraint to the lower bound of a fossil's age range to obtain similar ages to that of BEAST. Divergence time analyses with BEAST and treePL dated the BW stem back to the very Late Cretaceous and the divergence of the three subgenera in the Paleogene. By integrating fossil ages and morphology, a total evidence‐based dating approach was used in conjunction with time‐slice probabilities of dispersal under a DEC model to resolve ancestral ranges of each disjunct in the Miocene: Eurasia and ENA (disjunct 1), EA and western North America (disjunct 2), and EA (disjunct 3). The dated biogeographic history supports dispersal via the North Atlantic Land Bridge in the late Paleogene in disjunct 1 and dispersal via the Bering Land Bridge in the Miocene for disjuncts 2 and 3. Character mapping with a stochastic model in phytools and comparison of ecological niche, morphospace, and rate of evolution indicated differential divergence patterns in morphology, ecological niche, and molecules between disjunct sisters. Although morphological stasis was observed in most of the characters, evolutionary changes in growth habit and some features of leaf, flower, and fruit morphology occurred in one or both sister clades. A significant differentiation of ecological habitats in temperature, precipitation, and elevation between disjunct sisters was observed, suggesting a role of niche divergence in morphological evolution post‐isolation. The patterns of evolutionary rate between morphology and molecules varied among disjunct clades and were not always congruent between morphology and molecules, suggesting cases of non‐neutral morphological evolution driven by ecological selection. Our phylogenetic evidence and comparisons of evolutionary rate among disjunct lineages lend new insights into the formation of the diversity anomaly between EA and ENA, with particular support of an early diversification in EA. These findings, in conjunction with previous studies, again suggest that the EA–ENA disjunct floras are an assembly of lineages descended from the Mesophytic Forests that evolved from the early Paleogene “boreotropical flora” through varied evolutionary pathways across lineages.

Dasycerine rove beetles: Cretaceous diversification, phylogeny and historical biogeography (Coleoptera: Staphylinidae: Dasycerinae).

Within the hyperdiverse beetle family Staphylinidae, Dasycerinae is one of the smallest and most cryptic subfamilies, comprising a sole extant genus characterized by a latridiid beetle-like body form. Little has been known about their early diversification, character evolution, phylogeny and historical biogeography because of limited fossil material and lack of a phylogeny integrating extant and extinct representatives. Here we report an unexpectedly diverse dasycerine fauna from the mid-Cretaceous of northern Myanmar, including a new genus and four new species. To reconstruct the early evolutionary history of Dasycerinae, we present a phylogenetic framework of the subfamily based on a dataset integrating all extant and extinct taxa using parsimony, maximum-likelihood and Bayesian methods. †Cedasyrus gen. n., characterized by distinct sexual dimorphism in antennal and elytral lengths, is recovered as the basal-most lineage, sister to the remaining two extinct genera and all living Dasycerus species. †Vetudasycerus is recovered as sister to †Protodasycerus+Dasycerus. Among all extinct taxa, †Protodasycerus bears distinctly longer elytra, and appears to represent a transitional form from †Vetudasycerus to Dasycerus. Phylogenetic inferences and ancestral distribution reconstruction support an "Out-of-Orient" model for Dasycerinae. Either the Bering- or North Atlantic Land Bridge may have served as a passageway for dasycerine dispersal between Eurasian and North American continents. An elevation-reconstruction analysis indicated that the ancestor of the extant Dasycerus probably lived at a high altitude and stayed at this elevation through the end of the Miocene. We propose that the extinction of dasycerine ancestors living on the Tethyan islands at low altitude was likely caused by sea-level rise and climatic warming during the Late Cretaceous. The high-altitude areas might have played the role of refugia that harboured subalpine derivatives which eventually gave rise to the extant Dasycerus.

Biogeographic diversification of Mahonia (Berberidaceae): Implications for the origin and evolution of East Asian subtropical evergreen broadleaved forests

The subtropical evergreen broadleaved forests (EBLFs) inhabit large areas of East Asia and harbor rich biodiversity and high endemism. However, the origin and evolution of biodiversity of East Asian subtropical EBLFs remain poorly understood. Here, we used Mahonia (Berberidaceae), an eastern Asian-western North American disjunct evergreen genus, to obtain new insights into the historical assembly of this biome. We present the most comprehensive phylogenetic analysis of Mahonia do date based on six nuclear and plastid loci. Using the phylogenetic framework, we estimated divergence times, reconstructed ancestral ranges, inferred evolutionary shift of habitats, and estimated diversification rates. Mahonia and each of its two groups (Orientales and Occidentales) are strongly supported as monophyletic. Mahonia originated in western North America during the late Eocene (c. 40.41 Ma) and subsequently dispersed into East Asia prior to the early Oligocene (c. 32.65 Ma). The North Atlantic Land Bridge might have played an important role in population exchanges of Mahonia between East Asia and western North America. The western North American Occidentales began to diversify in summer-dry climates and open landscapes in the early Miocene, whereas the eastern Asian Orientales began to diversify in subtropical EBLFs in the early Miocene and furthermore had a rapid lineage accumulation since the late Miocene. The net diversification rate of Mahonia in eastern Asia appeared to be higher than that in western North America, which is ascribed to lower extinction rates and ecological opportunity. Our findings suggest that western North America is a source of biodiversity of East Asian subtropical EBLFs. This biome in eastern Asia began to rise in the early Miocene and further diversified in the late Miocene, driven by the intensifying East Asian summer monsoon during these two periods.

Phylogenomics, biogeography, and evolution of morphology and ecological niche of the eastern Asian–eastern North AmericanNyssa(Nyssaceae)

AbstractNyssa(Nyssaceae, Cornales) represents a classical example of the well‐known eastern Asian–eastern North American floristic disjunction. The genus consists of three species in eastern Asia, four species in eastern North America, and one species in Central America. Species of the genus are ecologically important trees in eastern North American and eastern Asian forests. The distribution of living species and a rich fossil record of the genus make it an excellent model for understanding the origin and evolution of the eastern Asian–eastern North American floristic disjunction. However, despite the small number of species, relationships within the genus have remained unclear and have not been elucidated using a molecular approach. Here, we integrate data from 48 nuclear genes, fossils, morphology, and ecological niche to resolve species relationships, elucidate its biogeographical history, and investigate the evolution of morphology and ecological niches, aiming at a better understanding of the well‐known EA–ENA floristic disjunction. Results showed that the Central American (CAM)Nyssa talamancanawas sister to the remaining species, which were divided among three, rapidly diversified subclades. Estimated divergence times and biogeographical history suggested thatNyssahad an ancestral range in Eurasia and western North America in the late Paleocene. The rapid diversification occurred in the early Eocene, followed by multiple dispersals between and within the Erasian and North American continents. The genus experienced two major episodes of extinction in the early Oligocene and end of Neogene, respectively. The Central AmericanN. talamancanarepresents a relic lineage of the boreotropical flora in the Paleocene/Eocene boundary that once diversified in western North America. The results supported the importance of both the North Atlantic land bridge and the Bering land bridge (BLB) for the Paleogene dispersals ofNyssaand the Neogene dispersals, respectively, as well as the role of Central America as refugia of the Paleogene flora. The total‐evidence‐based dated phylogeny suggested that the pattern of macroevolution ofNyssacoincided with paleoclimatic changes. We found a number of evolutionary changes in morphology (including wood anatomy and leaf traits) and ecological niches (precipitation and temperature) between the EA–ENA disjunct, supporting the ecological selection driving trait evolutions after geographic isolation. We also demonstrated challenges in phylogenomic studies of lineages with rapid diversification histories. The concatenation of gene data can lead to inference of strongly supported relationships incongruent with the species tree. However, conflicts in gene genealogies did not seem to impose a strong effect on divergence time dating in our case. Furthermore, we demonstrated that rapid diversification events may not be recovered in the divergence time dating analysis using BEAST if critical fossil constraints of the relevant nodes are not available. Our study provides an example of complex bidirectional exchanges of plants between Eurasia and North America in the Paleogene, but “out of Asia” migrations in the Neogene, to explain the present disjunct distribution ofNyssain EA and ENA.

The saprotrophic Pleurotus ostreatus species complex: late Eocene origin in East Asia, multiple dispersal, and complex speciation

The Pleurotus ostreatus species complex is saprotrophic and of significant economic and ecological importance. However, species delimitation has long been problematic because of phenotypic plasticity and morphological stasis. In addition, the evolutionary history is poorly understood due to limited sampling and insufficient gene fragments employed for phylogenetic analyses. Comprehensive sampling from Asia, Europe, North and South America and Africa was used to run phylogenetic analyses of the P. ostreatus species complex based on 40 nuclear single-copy orthologous genes using maximum likelihood and Bayesian inference analyses. Here, we present a robust phylogeny of the P. ostreatus species complex, fully resolved from the deepest nodes to species level. The P. ostreatus species complex was strongly supported as monophyletic, and 20 phylogenetic species were recognized, with seven putatively new species. Data from our molecular clock analyses suggested that divergence of the genus Pleurotus probably occurred in the late Jurassic, while the most recent common ancestor of the P. ostreatus species complex diversified about 39 Ma in East Asia. Species of the P. ostreatus complex might migrate from the East Asia into North America across the North Atlantic Land Bridge or the Bering Land Bridge at different times during the late Oligocene, late Miocene and late Pliocene, and then diversified in the Old and New Worlds simultaneously through multiple dispersal and vicariance events. The dispersal from East Asia to South America in the middle Oligocene was probably achieved by a long-distance dispersal event. Intensification of aridity and climate cooling events in the late Miocene and Quaternary glacial cycling probably had a significant influence on diversification patterns of the complex. The disjunctions among East Asia, Europe, North America and Africa within Clade IIc are hypothesized to be a result of allopatric speciation. Substrate transitions to Apiaceae probably occurred no earlier than 6 Ma. Biogeographic analyses suggested that the global cooling of the late Eocene, intensification of aridity caused by rapid uplift of the QTP and retreat of the Tethys Sea in the late Miocene, climate cooling events in Quaternary glacial cycling, and substrate transitions have contributed jointly to diversification of the species complex.