Historical biogeography and evolutionary diversification of Lilium (Liliaceae): New insights from plastome phylogenomics.

Here, we infer the historical biogeography and evolutionary diversification of the genus Lilium. For this purpose, we used the complete plastomes of 64 currently accepted species in the genus Lilium (14 plastomes were newly sequenced) to recover the phylogenetic backbone of the genus and a time-calibrated phylogenetic framework to estimate biogeographical history scenarios and evolutionary diversification rates of Lilium. Our results suggest that ancient climatic changes and geological tectonic activities jointly shaped the distribution range and drove evolutionary radiation of Lilium, including the Middle Miocene Climate Optimum (MMCO), the late Miocene global cooling, as well as the successive uplift of the Qinghai-Tibet Plateau (QTP) and the strengthening of the monsoon climate in East Asia during the late Miocene and the Pliocene. This case study suggests that the unique geological and climatic events in the Neogene of East Asia, in particular the uplift of QTP and the enhancement of monsoonal climate, may have played an essential role in formation of uneven distribution of plant diversity in the Northern Hemisphere.

Plastid phylogenomics and fossil evidence provide new insights into the evolutionary complexity of the 'woody clade' in Saxifragales.

BACKGROUND: The "woody clade" in Saxifragales (WCS), encompassing four woody families (Altingiaceae, Cercidiphyllaceae, Daphniphyllaceae, and Hamamelidaceae), is a phylogenetically recalcitrant node in the angiosperm tree of life, as the interfamilial relationships of the WCS remain contentious. Based on a comprehensive sampling of WCS genera, this study aims to recover a robust maternal backbone phylogeny of the WCS by analyzing plastid genome (plastome) sequence data using Bayesian inference (BI), maximum likelihood (ML), and maximum parsimony (MP) methods, and to explore the possible causes of the phylogenetic recalcitrance with respect to deep relationships within the WCS, in combination with molecular and fossil evidence. RESULTS: Although the four WCS families were identically resolved as monophyletic, the MP analysis recovered different tree topologies for the relationships among Altingiaceae, Cercidiphyllaceae, and Daphniphyllaceae from the ML and BI phylogenies. The fossil-calibrated plastome phylogeny showed that the WCS underwent a rapid divergence of crown groups in the early Cretaceous (between 104.79 and 100.23 Ma), leading to the origin of the stem lineage ancestors of Altingiaceae, Cercidiphyllaceae, Daphniphyllaceae, and Hamamelidaceae within a very short time span (∼4.56 Ma). Compared with the tree topology recovered in a previous study based on nuclear genome data, cytonuclear discordance regarding the interfamilial relationships of the WCS was detected. CONCLUSIONS: Molecular and fossil evidence imply that the early divergence of the WCS might have experienced radiative diversification of crown groups, extensive extinctions at the genus and species levels around the Cretaceous/Paleocene boundary, and ancient hybridization. Such evolutionarily complex events may introduce biases in topological estimations within the WCS due to incomplete lineage sorting, cytonuclear discordance, and long-branch attraction, potentially impacting the accurate reconstruction of deep relationships.

Miocene Dipteronia (Sapindaceae) samaras from South Korea and their biogeographical implications.

Dipteronia, now endemic to East Asia, was widely distributed in North America during the Paleogene; however, its fossil records in Asia are scarce and none are of the Neogene. Here, we report the first Neogene Dipteronia samaras from South Korea. The more complete fossil records suggest that Dipteronia possibly originated in either Asia or North America and that its two known lineages have different geographical histories. The Dipteronia sinensis lineage was established in Asia and North America in the Paleocene and reached its maximum range in the Eocene, followed by stepwise range contraction and extirpation in North America, South Korea, and southwestern China, finally becoming endemic to central China. In contrast, the Dipteronia dyeriana lineage might have been restricted to southwestern China, where it originated, indicating historical confinement. The current restricted distribution of Dipteronia possibly resulted from its evolutionary deceleration in a constantly changing environment.

Leaf fossils of Sabalites (Arecaceae) from the Oligocene of northern Vietnam and their paleoclimatic implications.

Recent paleobotanical investigations in Vietnam provide a good opportunity to improve our understanding of the biodiversity and paleoclimatic conditions in the geological past of Southeast Asia. Palms (Arecaceae) are a diverse family of typical thermophilous plants with a relatively low tolerance for freezing. In this study, we describe well-preserved fossil palm leaves from the Oligocene Dong Ho Formation of Hoanh Bo Basin, northern Vietnam. Characters of the fossil leaves, such as a fan-shaped costapalmate lamina, an unarmed petiole, a costa slightly enlarged at the base that then tapers distally into the blade, and well-preserved amphistomatic leaves with cuticles, suggest that they represent a new fossil species, which we herein designate Sabalites colaniae A. Song, T. Su, T. V. Do et Z.K. Zhou sp. nov. Together with other paleontological and palaeoclimatic evidence, we conclude that a warm climate prevailed in northern Vietnam and nearby areas during the Oligocene.

Fossil fruits of Firmiana and Tilia from the middle Miocene of South Korea and the efficacy of the Bering land bridge for the migration of mesothermal plants.

Determining whether the high-latitude Bering land bridge (BLB) was ecologically suitable for the migration of mesothermal plants is significant for Holarctic phytogeographic inferences. Paleobotanical studies provide a critical source of data on the latitudinal positions of different plant lineages at different times, permitting assessment of the efficacy of the BLB for migration. Here we report exceptionally preserved fossils of Firmiana and Tilia endochrysea from the middle Miocene of South Korea. This represents a new reliable record of Firmiana and the first discovery of the T. endochrysea lineage in the fossil record of Asia. The occurrence of these fossils in South Korea indicates that the two lineages had a distribution that extended much farther north during the middle Miocene, but they were still geographically remote from the BLB. In light of the broader fossil record of Asia, our study shows that, in the middle Miocene, some mesothermal plants apparently inhabited the territory adjacent to the BLB and thus they were possibly capable of utilizing the BLB as a migratory corridor. Some other mesothermal plants, such as Firmiana and the T. endochrysea lineages, however, are restricted to more southern regions relative to the BLB based on current fossil evidence. These lineages may have been ecologically unable to traverse the BLB, which raises questions about the efficacy of the BLB as a universal exchange route for mesothermal plants between Asia and North America during the middle Miocene.

A Middle Eocene lowland humid subtropical "Shangri-La" ecosystem in central Tibet.

Tibet's ancient topography and its role in climatic and biotic evolution remain speculative due to a paucity of quantitative surface-height measurements through time and space, and sparse fossil records. However, newly discovered fossils from a present elevation of ∼4,850 m in central Tibet improve substantially our knowledge of the ancient Tibetan environment. The 70 plant fossil taxa so far recovered include the first occurrences of several modern Asian lineages and represent a Middle Eocene (∼47 Mya) humid subtropical ecosystem. The fossils not only record the diverse composition of the ancient Tibetan biota, but also allow us to constrain the Middle Eocene land surface height in central Tibet to ∼1,500 ± 900 m, and quantify the prevailing thermal and hydrological regime. This "Shangri-La"-like ecosystem experienced monsoon seasonality with a mean annual temperature of ∼19 °C, and frosts were rare. It contained few Gondwanan taxa, yet was compositionally similar to contemporaneous floras in both North America and Europe. Our discovery quantifies a key part of Tibetan Paleogene topography and climate, and highlights the importance of Tibet in regard to the origin of modern Asian plant species and the evolution of global biodiversity.

Involucre fossils of Carpinus, a northern temperate element, from the Miocene of China and the evolution of its species diversity in East Asia.

East Asia has long been recognized as a major center for temperate woody plants diversity. Although several theories have been proposed to explain how the diversity of these temperate elements accumulated in the region, the specific process remains unclear. Here we describe six species of Carpinus, a typical northern hemisphere temperate woody plant, from the early Miocene of the Maguan Basin, southwestern China, southern East Asia. This constitutes the southernmost, and the earliest occurrence that shows a high species diversity of the genus. Together with other Carpinus fossil records from East Asia, we show that the genus had achieved a high diversity in East Asia at least by the middle Miocene. Of the six species here described, three have become extinct, indicating that the genus has experienced apparent species loss during its evolutionary history in East Asia. In contrast, the remaining three species closely resemble extant species, raising the possibility that these species may have persisted in East Asia at least since the early Miocene. These findings indicate that the accumulation of species diversity of Carpinus in East Asia is a complex process involving extinction, persistence, and possible subsequent speciation.

Uplift, climate and biotic changes at the Eocene-Oligocene transition in south-eastern Tibet.

The uplift history of south-eastern Tibet is crucial to understanding processes driving the tectonic evolution of the Tibetan Plateau and surrounding areas. Underpinning existing palaeoaltimetric studies has been regional mapping based in large part on biostratigraphy that assumes a Neogene modernization of the highly diverse, but threatened, Asian biota. Here, with new radiometric dating and newly collected plant-fossil archives, we quantify the surface height of part of the south-eastern margin of Tibet in the latest Eocene (∼34 Ma) to be ∼3 km and rising, possibly attaining its present elevation (3.9 km) in the early Oligocene. We also find that the Eocene-Oligocene transition in south-eastern Tibet witnessed leaf-size diminution and a floral composition change from sub-tropical/warm temperate to cool temperate, likely reflective of both uplift and secular climate change, and that, by the latest Eocene, floral modernization on Tibet had already taken place, implying modernization was deeply rooted in the Palaeogene.

A primitive honey bee from the Middle Miocene deposits of southeastern Yunnan, China (Hymenoptera, Apidae).

While fossils of honey bees (Apini: Apis Linnaeus) are comparatively abundant in European Oligocene and Miocene deposits, the available material from Asia is scant and represented by only a handful of localities. It is therefore significant to report a new deposit with a fossil honey bee from southern China. Apis (Synapis) dalica Engel & Wappler, sp. n., is described and figured from Middle Miocene sediments of Maguan County, southeastern Yunnan Province, China. This is the first fossil bee from the Cenozoic of southern China, and is distinguished from its close congeners present at the slightly older locality of Shanwang, Shandong in northeastern China. The species can be distinguished on the basis of wing venation differences from other Miocene Apis.

Cenozoic plant diversity of Yunnan: A review.

Yunnan in southwestern China is renowned for its high plant diversity. To understand how this modern botanical richness formed, it is critical to investigate the past biodiversity throughout the geological time. In this review, we present a summary on plant diversity, floristics and climates in the Cenozoic of Yunnan and document their changes, by compiling published palaeobotanical sources. Our review demonstrates that thus far a total of 386 fossil species of ferns, gymnosperms and angiosperms belonging to 170 genera within 66 families have been reported from the Cenozoic, particularly the Neogene, of Yunnan. Angiosperms display the highest richness represented by 353 species grouped into 155 genera within 60 families, with Fagaceae, Fabaceae, Lauraceae and Juglandaceae being the most diversified. Most of the families and genera recorded as fossils still occur in Yunnan, but seven genera have disappeared, including Berryophyllum, Cedrelospermum, Cedrus, Palaeocarya, Podocarpium, Sequoia and Wataria. The regional extinction of these genera is commonly referred to an aridification of the dry season associated with Asian monsoon development. Floristic analyses indicate that in the late Miocene, Yunnan had three floristic regions: a northern subtropical floristic region in the northeast, a subtropical floristic region in the east, and a tropical floristic region in the southwest. In the late Pliocene, Yunnan saw two kinds of floristic regions: a subalpine floristic region in the northwest, and two subtropical floristic regions separately in the southwest and the eastern center. These floristic concepts are verified by results from our areal type analyses which suggest that in the Miocene southwestern Yunnan supported the most Pantropic elements, while in the Pliocene southwestern Yunnan had abundant Tropical Asia (Indo-Malaysia) type and East Asia and North America disjunct type that were absent from northwestern Yunnan. From the late Miocene to late Pliocene through to the present, floristic composition and vegetation types changed markedly, presumably in response to altitude changes and coeval global cooling. An integration of palaeoclimate data suggests that during the Neogene Yunnan was warmer and wetter than today. Moreover, northern Yunnan witnessed a pronounced temperature decline, while southern Yunnan experienced only moderate temperature changes. Summer precipitation was consistently higher than winter precipitation, suggesting a rainfall seasonality. This summary on palaeoclimates helps us to understand under what conditions plant diversity occurred and evolved in Yunnan throughout the Cenozoic.

First occurrence of Cedrelospermum (Ulmaceae) in Asia and its biogeographic implications.

Cedrelospermum (Ulmaceae) is an extinct genus with extensive fossil records in Europe and North America. However, no fossil of the genus has been reported from Asia. Here we describe Cedrelospermum asiaticum L.B. Jia, Y.J. Huang et Z.K. Zhou sp. nov. based on compressed fruits from the late Miocene of Yunnan, southwestern China. The fossil fruits are characterized by an ovate fruit body adjoined by double wings, with the veins on the primary wing converging toward a stigmatic area. According to the historical geographic distribution of the genus, we hypothesize that Cedrelospermum originated in North America where both single-winged and double-winged fruits were reported. The single-winged form subsequently spread into Europe via the North Atlantic land bridge and the double-winged form dispersed into Asia via the Bering land bridge. From the Eocene to Oligocene, a southward retreat of the genus distribution probably took place, which coincided with the global surface cooling initiated during the Eocene-Oligocene transition. The extinction of Cedrelospermum from Asia may be related to the intensification of the East Asian monsoon.