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Maps showing the distribution of fossil and living Thuja. (A—D)▲: Fossil record of Thuja, projections of Lambert Equal-Area Azimuthal (North Pole); (E) Potential migration route of Thuja: Pink part shows the present distributional range of this genus in the world. The dark gray arrows show the possible migration route of Thuja. The data of palaeolatitude and palaeolongitude were converted from those of latitude and longitude of fossil sites using “PointTracker for Windows” software, and plotted on 4 individual palaeogeographical maps and 1 modern geographical map on Projections of Lambert Equal-Area Azimuthal (North Pole) by using ArcView GIS 3.2 software.
Source publication
Thuja, a genus of Cupressaceae comprising five extant species, presently occurs in both East Asia (3 species) and North America (2 species) and has a long fossil record from Paleocene to Pleistocene in the Northern Hemisphere. Two distinct hypotheses have been proposed to account for the origin and present distribution of this genus. Here we recogn...
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Thuja occidentalis (family: Cupressaceae) has been used as antiseptic, expectorant, diuretic and in the treatment of cancer and removal of kidney stones in different systems of medicine. The present studies were carried out on T. occidentalis leaves extract to evaluate the hematological and biochemical effects on rabbits. The animals were divided i...
(Linnaeus, 1767), previously considered a very rare and localised (accidental) species in Eastern Europe (Hungary, Romania), is recorded as a real pest for Cupressaceae in the Romanian Plain − the Easternmost site, out of the species’ previously known range. In comparison with the annual life cycle of the species in the Mediterranean region, in Rom...
Citations
... Biotic disjunction, the occurrence of related organisms in disconnected areas of Earth, has attracted scientific attention since the time of Linnaeus (Gray, 1859;Boufford and Spongberg, 1983;Wen, 1999;Xiang et al., 2015;Lopes et al., 2023;Stull, 2023). Disjunct patterns can occur within relatively small geographic areas, such as populations separated by a river or over neighboring mountains; or across larger areas such as continents (Raven, 1972;Thorne, 1972;Wen, 1999;Donoghue et al., 2001;Wen et al., 2010;Cui et al., 2015). The study of disjunct distributional patterns has a long history of providing important insights into the assembly of today's flora and fauna, including providing some of the first evidence for plate tectonics, land bridges, and historical climate change (Raven, 1972;Wen, 1999;Deng et al., 2015). ...
... The Arcto-Tertiary flora hypothesis, one of the main hypotheses put forward to explain this ENA-EA disjunction, invokes that an ancient circumpolar temperate flora existed in the Northern Hemisphere during the late Cretaceous and Palaeogene and was fragmented and driven south at the end of the Miocene, approximately 15-5 million years ago (mya) (Wen, 1999;Milne and Abbott, 2002;Milne, 2006;Deng et al., 2015). The hypothesis of fragmentation of an ancient circumpolar flora has substantial explanatory power for understanding the origin of today's temperate floras, but the contemporary disjunction pattern is thought to be the product of multiple historical events at different geologic times in different groups, rather than proceeding from a single timeline or one simplistic mechanism (Boufford and Spongberg, 1983;White, 1983;Wen, 1999;Donoghue and Smith, 2004;Nie et al., 2006;Wen et al., 2010;Lu et al., 2011;Cui et al., 2015;Xiang et al., 2015;Rose et al., 2018;Stull, 2023). ...
Premise
Biotic disjunctions have attracted scientific attention for the past 200 years. Despite being represented in many familiar plants (such as bald cypress, flowering dogwood, sweetgum, partridgeberry, etc.), the eastern North American (ENA)–Mexican (M) disjunction remains poorly understood. Major outstanding questions include the divergence times of taxa exhibiting the disjunction and environmental/geological processes that may underlie the disjunction. Symphyotrichum Nees (Asteraceae), one of the most diverse genera in the eastern USA, displays several examples of disjunct ENA–M taxa.
Methods
We generated target capture data using the Angiosperms353 baitset and generated the first well‐sampled phylogenomic hypothesis for Symphyotrichum and its close relatives. Focusing on S . subgenus Virgulus , we used MCMC TREE to perform divergence time estimation and the R package BioGeoBEARS to infer ancestral regions and biogeographic transitions between North America and Mexico. Finally, we used the ancestral niche reconstruction method Utremi to test for a role of historical aridification in generating the disjunction.
Results
Our molecular data suggest a recent radiation of Symphyotrichum at the Plio‐Pleistocene boundary (~2.5 mya), with early connections to Mexico in ancestral lineages that closed off shortly after and were followed by vicariance across this region. Except for some present‐day broadly distributed species, there is a complete lack of movement between ENA and M after ~0.5 mya.
Conclusions
A reconstructed disjunct distribution of suitable habitat in Pleistocene climatic models corroborates results from biogeographic modeling and confirms glacial cycles are more likely to be associated with the breakup of ENA–M biogeographic connections.
... Thuja umfasst heute fünf Arten, die in den gemischt-mesophytischen Wäldern Asiens und Nordamerikas vorkommen (Wang 1961;Eckenwalder 1976;Flora of North America Editorial Committee 1993;Farjon 2005;Cui et al. 2015). Thuja sutchenensis tritt an begrenzten Standorten in Chongking und Chengkau, China, auf; T. koraiensis Nakai 1919 ist ebenfalls selten und ist in isolierten Populationen in Nord-und Südkorea zu finden. ...
Ein Thuja-ähnliches Holz, cf. Taxodioxylon (aff. Thuja L.), aus dem Nördlinger Ries und Szenarien der paläobiogeografischen Evolution Kurzfassung Es wird ein fossiles Holz, cf. Taxodioxylon (aff. Thuja L.), aus der Bunten Brekzie des Nördlinger Ries-Impaktes in Bay-ern vorgestellt. Die Beschreibung basiert auf zwei xylitischen Hölzern, die mittels Datierung des Ries-Asteroiden von 14,9 Millionen Jahren in das Klimaoptimum des Mittelmiozäns gestellt werden. Das Holz ist durch taxodioide und cupressoide Kreuzungsfeldtüpfel, niedrige Strahlen, uniseriate Hoftüpfel, dünne und glatte horizontale so-wie tangentiale Strahlzellwände, dem Vorkommen von Axialparenchym mit getüpfelten horizontalen Wänden und Warzen auf den Tracheiden charakterisiert. Das fossile Holz ist in seinen anatomischen Merkmalen dem Holz der heutigen Thuja L. 1753 am ähnlichsten. Des Weiteren wurde ein taxonomischer Vergleich mit Arten der fossi-len Gattung Thujoxylon Ung. 1842 durchgeführt. Die Bunte Brekzie wurde in zwei Ausgrabungen in Nattheim, 31 km vom Zentrum des Ries-Einschlags, dokumentiert und beprobt. Gefunden wurden unter anderem ballistisch ausgeworfene, stark beanspruchte Kristallingesteine und Deckgesteinsbestandteile des primären Kraterrandes. Weiterhin ist lokales Material als Klasten bzw. Tonmatrix vertreten. Für Thuja, eine disjunkte Gattung zwischen Ost-asien und Nordamerika und für Thuja-ähnliche rezente sowie ausgestorbene Gattungen wurden zwei mögliche paläobiogeographische Szenarien unter Berücksichtigung der verschiedenen, regelmäßig für den floralen bioti-schen Austausch verfügbaren Landbrücken wie der Bering-Brücke und der nordatlantischen Brücken, aufgestellt. Das erste Migrationsmuster basiert auf der Interpretation fossiler Samenzapfen von Thuja, die in der Oberkreide Alaskas auftauchten. Die zweite Interpretation, wiederum ausgehend von den Alaska-Funden in der Oberkreide, umfasst alle Thuja-und Thuja-ähnlichen Fossilien. Gut unterscheidbare Jahresringe der Hölzer unterstreichen die Saisonalität des Paläoklimas. Enge und unregelmäßig dicke Jahresringe weisen auf ein langsames Dickenwachs-tum und auf generell ungünstige individuelle Wachstumsbedingungen hin. Abstract A fossil wood, cf. Taxodioxylon (aff. Thuja L.), is introduced from the Bunte Breccia deposits of the Nördlinger Ries impact in Bavaria. This taxon is based on two xylitic pieces of wood that were present during the Middle Miocene Climate Optimum of 14.9 million years based on the date of the Ries asteroid. The fossil wood is characterized by possessing taxodioid and cupressoid cross-field pits, short rays, uniseriate bordered pits, thin and smooth horizontal and tangential ray cell walls, axial parenchyma with pitted transverse horizontal walls, and warts on the tracheids. These features are anatomically most similar to the wood of extant Thuja L. 1753. Furthermore, we provide a taxonomic comparison with species of the fossil genus Thujoxylon Ung. 1842. The Bunte Breccia has been documented and sampled in two excavations in Nattheim, 31 km from the centre of the Ries impact. Ballistically ejected, strongly shocked crystalline rocks and overburden components of the presumed primary crater rim are present. Locally, the substrate is widely represented by clasts in a clay matrix. For Thuja, a disjunct genus between East Asia and North America and for Thuja-like extant and extinct genera, two possible palaeo-biogeographical scenarios are proposed. The different land bridges that regularly were available for floral biotic
... Thuja umfasst heute fünf Arten, die in den gemischt-mesophytischen Wäldern Asiens und Nordamerikas vorkommen (Wang 1961;Eckenwalder 1976;Flora of North America Editorial Committee 1993;Farjon 2005;Cui et al. 2015). Thuja sutchenensis tritt an begrenzten Standorten in Chongking und Chengkau, China, auf; T. koraiensis Nakai 1919 ist ebenfalls selten und ist in isolierten Populationen in Nord-und Südkorea zu finden. ...
Ein Thuja-ähnliches Holz, cf. Taxodioxylon (aff. Thuja L.), aus dem Nördlinger Ries und Szenarien der paläobiogeografischen Evolution Kurzfassung Es wird ein fossiles Holz, cf. Taxodioxylon (aff. Thuja L.), aus der Bunten Brekzie des Nördlinger Ries-Impaktes in Bay-ern vorgestellt. Die Beschreibung basiert auf zwei xylitischen Hölzern, die mittels Datierung des Ries-Asteroiden von 14,9 Millionen Jahren in das Klimaoptimum des Mittelmiozäns gestellt werden. Das Holz ist durch taxodioide und cupressoide Kreuzungsfeldtüpfel, niedrige Strahlen, uniseriate Hoftüpfel, dünne und glatte horizontale so-wie tangentiale Strahlzellwände, dem Vorkommen von Axialparenchym mit getüpfelten horizontalen Wänden und Warzen auf den Tracheiden charakterisiert. Das fossile Holz ist in seinen anatomischen Merkmalen dem Holz der heutigen Thuja L. 1753 am ähnlichsten. Des Weiteren wurde ein taxonomischer Vergleich mit Arten der fossi-len Gattung Thujoxylon Ung. 1842 durchgeführt. Die Bunte Brekzie wurde in zwei Ausgrabungen in Nattheim, 31 km vom Zentrum des Ries-Einschlags, dokumentiert und beprobt. Gefunden wurden unter anderem ballistisch ausgeworfene, stark beanspruchte Kristallingesteine und Deckgesteinsbestandteile des primären Kraterrandes. Weiterhin ist lokales Material als Klasten bzw. Tonmatrix vertreten. Für Thuja, eine disjunkte Gattung zwischen Ost-asien und Nordamerika und für Thuja-ähnliche rezente sowie ausgestorbene Gattungen wurden zwei mögliche paläobiogeographische Szenarien unter Berücksichtigung der verschiedenen, regelmäßig für den floralen bioti-schen Austausch verfügbaren Landbrücken wie der Bering-Brücke und der nordatlantischen Brücken, aufgestellt. Das erste Migrationsmuster basiert auf der Interpretation fossiler Samenzapfen von Thuja, die in der Oberkreide Alaskas auftauchten. Die zweite Interpretation, wiederum ausgehend von den Alaska-Funden in der Oberkreide, umfasst alle Thuja-und Thuja-ähnlichen Fossilien. Gut unterscheidbare Jahresringe der Hölzer unterstreichen die Saisonalität des Paläoklimas. Enge und unregelmäßig dicke Jahresringe weisen auf ein langsames Dickenwachs-tum und auf generell ungünstige individuelle Wachstumsbedingungen hin. Abstract A fossil wood, cf. Taxodioxylon (aff. Thuja L.), is introduced from the Bunte Breccia deposits of the Nördlinger Ries impact in Bavaria. This taxon is based on two xylitic pieces of wood that were present during the Middle Miocene Climate Optimum of 14.9 million years based on the date of the Ries asteroid. The fossil wood is characterized by possessing taxodioid and cupressoid cross-field pits, short rays, uniseriate bordered pits, thin and smooth horizontal and tangential ray cell walls, axial parenchyma with pitted transverse horizontal walls, and warts on the tracheids. These features are anatomically most similar to the wood of extant Thuja L. 1753. Furthermore, we provide a taxonomic comparison with species of the fossil genus Thujoxylon Ung. 1842. The Bunte Breccia has been documented and sampled in two excavations in Nattheim, 31 km from the centre of the Ries impact. Ballistically ejected, strongly shocked crystalline rocks and overburden components of the presumed primary crater rim are present. Locally, the substrate is widely represented by clasts in a clay matrix. For Thuja, a disjunct genus between East Asia and North America and for Thuja-like extant and extinct genera, two possible palaeo-biogeographical scenarios are proposed. The different land bridges that regularly were available for floral biotic
... The Sichuan Arborvitae, Thuja sutchuenensis Franch., is an endangered conifer endemic to limestone cliffs, ridges, or steep slopes at 800e2100 m above sea level in northwestern Chongqing and the Daba Mountains in the eastern Sichuan Basin (Xiang et al., 2002;Cui et al., 2015;Tang et al., 2015). It is a tertiary relict species with a complex evolutionary history, and was once listed as extinct in the wild by IUCN but was rediscovered in 1999 (Xiang et al., 2002). ...
... Because MUs are based on the demographic independence of populations (Palsbøll et al., 2007), we argue that our demographic reconstruction provides further support for the division of the T. sutchuenensis population into three separate MUs. Fossil evidence from the late Pliocene in Shanxi Province, northern China (Cui et al., 2015), ca. 700 km to the northeast of the current distribution of T. sutchuenensis in the Daba Mountains, southwestern China, indicates that this species once had a wider distribution in China. ...
Endangered species generally have small populations with low genetic diversity and a high genetic load. Thuja sutchuenensis is an endangered conifer endemic to southwestern China. It was once considered extinct in the wild, but in 1999 was rediscovered. However, little is known about its genetic load. We collected 67 individuals from five wild, isolated T. sutchuenensis populations, and used 636,151 SNPs to analyze the level of genetic diversity and genetic load in T. sutchuenensis to delineate the conservation units of T. sutchuenensis, based on whole transcriptome sequencing data, as well as target capture sequencing data. We found that populations of T. sutchuenensis could be divided into three groups. These groups had low levels genetic diversity and were moderately genetically differentiated. Our findings also indicate that T. sutchuenensis suffered two severe bottlenecks around the Last Glaciation Period and Last Glacial Maximum. Among Thuja species, T. sutchuenensis presented the lowest genetic load and hence might have purged deleterious mutations efficiently through purifying selection. However, distribution of fitness effects analysis indicated a high extinction risk for T. sutchuenensis. Multiple lines of evidence identified three management units for T. sutchuenensis. Although T. sutchuenensis possesses a low genetic load, low genetic diversity, suboptimal fitness, and anthropogenic pressures all present an extinction risk for this rare conifer. This might also hold true for many endangered plant species in the mountains all over the world.
... Fossils of Torreya occur widely across the Northern Hemisphere and date to as early as the Jurassic (Florin, 1963;Kimura, 1987) (Table S1). Thus, inclusion of fossils, which may reveal more complex biogeographic histories than preserved among extant species, is particularly important for the biogeographic analysis of the genus and conifers in general, which often have old, robust fossil records (Klymiuk & Stockey, 2012;Ryberg et al., 2012;Cui et al., 2015). In this study, we used nuclear data from RAD-seq (Peterson et al., 2012) as well as chloroplast and mitochondrial data from Hyb-Seq to reconstruct the phylogeny of the genus, adding fossils to the phylogeny through phylogenetic analysis of combined molecular and morphological data, and elucidated the biogeographic history of Torreya using a likelihood method for modeling range evolution. ...
Restriction site‐associated DNA sequencing (RAD‐seq) enables obtaining thousands of genetic markers for phylogenomic studies. However, RAD‐seq data are subject to allele dropout (ADO) due to polymorphisms at enzyme cutting sites. We developed a new pipeline, RADADOR, to mitigate the ADO in outgroups by recovering missing loci from previously published transcriptomes in our study of a gymnosperm genus Torreya. Using the supplemented RAD‐seq data in combination with plastome and mitochondrial gene sequences, morphology, and fossil records, we reconstructed the phylogenetic and biogeographic histories of the genus and test hypotheses on diversity anomaly in eastern Asian‐North American floristic disjunction. Our results showed that our pipeline recovered many loci missing from the outgroup, and the improved data yielded a more robust phylogeny for Torreya. Using the fossilized‐birth‐death model and divergence‐extinction‐cladogenesis method we resolved detailed biogeographic history of Torreya that suggested a Jurassic origin in the Laurasia and differential speciation and extinction among continents accounting for the modern diversity anomaly biased toward Eastern Asia (EA). The history also supported a vicariance origin of the modern Torreya from a widespread ancestor in EA and NA in the mid‐Eocene, cross‐Beringia exchange in the early Paleogene before the vicariant isolation, in contrast to the “Out of NA” pattern common to gymnosperms and in contrast to the “Out of EA” hypothesis previously proposed for the genus. Furthermore, we observed phylogenetic discordance between the nuclear and plastid phylogenies on T. jackii, suggesting differential lineage sorting of plastid genomes among Torreya species or plastid genome capture in T. jackii. This article is protected by copyright. All rights reserved.
... Here, we study the genetic diversity and structure of Thuja sutchuenensis Franch, an endangered species endemic to the Daba Mountains in northwestern Chongqing Municipality and eastern Sichuan Province, China (Xiang et al., 2002;Tang et al., 2015). Cooling and drying climate in the Quaternary forced T. sutchuenensis southward and restricted in the Daba mountains (Cui et al., 2015). When did T. sutchuenensis arrive at the Daba mountains, and can it survive only in this restricted region? ...
... Thuja sutchuenensis, a monoecious and evergreen coniferous tree, distributed in the Chongqing Municipality and Sichuan Province, Southwest China (Xiang et al., 2002;Cui et al., 2015) (Figure 1). We sampled 375 plants from six wild and three cultivated T. sutchuenensis populations, and recorded longitude, latitude, and altitude of the T. sutchuenensis plants ( Table 1). ...
... T. sutchuenensis was widely distributed in China in the late Pliocene based on its fossil in the Shanxi province ( Figure 1C) (Cui et al., 2015), and its distributed area and population size decreased from the Last Interglacial (LIG, ∼120-140 ka) to the Last Glacial Maximum (LGM, ∼22 ka) . Our results found that T. sutchuenensis wild populations were from a common ancestral population at 203 ka, which means that T. sutchuenensis southward-migrated and reached the Daba mountains before the population concentration of T. sutchuenensis. ...
Narrow-ranged species face challenges from natural disasters and human activities, and to address why species distributes only in a limited region is of great significance. Here we investigated the genetic diversity, gene flow, and genetic differentiation in six wild and three cultivated populations of Thuja sutchuenensis, a species that survive only in the Daba mountain chain, using chloroplast simple sequence repeats (cpSSR) and nuclear restriction site-associated DNA sequencing (nRAD-seq). Wild T. sutchuenensis populations were from a common ancestral population at 203 ka, indicating they reached the Daba mountain chain before the start of population contraction at the Last Interglacial (LIG, ∼120–140 ka). T. sutchuenensis populations showed relatively high chloroplast but low nuclear genetic diversity. The genetic differentiation of nRAD-seq in any pairwise comparisons were low, while the cpSSR genetic differentiation values varied with pairwise comparisons of populations. High gene flow and low genetic differentiation resulted in a weak isolation-by-distance effect. The genetic diversity and differentiation of T. sutchuenensis explained its survival in the Daba mountain chain, while its narrow ecological niche from the relatively isolated and unique environment in the “refugia” limited its distribution.
... evolucionario/fossilgraft; Claramunt & Cracraft, 2015) to add the fossil species to the time-calibrated tree, as terminal tips. The relationships between fossil and extant species were based on the phylogenetic relationships and morphological similarities reconstructed in previous studies (Cui et al., 2015;LePage, 2003;McIver & Basinger, 1989). ...
... The ancestral populations of Thuja probably dispersed to large parts of East Asia and North America during this time period. The rich fossil record of Thuja from the late Cretaceous to the Pleistocene in the Northern Hemisphere further supports the hypothesis that this genus once had a wider distribution (Cui et al., 2015;LePage, 2003;Taberlet & Luikart, 2008). ...
The Eastern Asia (EA) – North America (NA) disjunction is a well-known biogeographic pattern of the Tertiary relict flora; however, few studies have investigated the evolutionary history of this disjunction using a phylogenomic approach. Here, we used 2369 single copy nuclear genes and nearly full plastomes to reconstruct the evolutionary history of the small Tertiary relict genus Thuja, which consists of five disjunctly distributed species. The nuclear species tree strongly supported an EA clade Thuja standishii–Thuja sutchuenensis and a “disjunct clade”, where western NA species T. plicata is sister to an EA-eastern NA disjunct Thuja occidentalis–Thuja koraiensis group. Our results suggested that the observed topological discordance among the gene trees as well as the cytonuclear discordance is mainly due to incomplete lineage sorting, probably facilitated by the fast diversification of Thuja around the Early Miocene and the large effective population sizes of ancestral lineages. Furthermore, approximately 20% of the T. sutchuenensis nuclear genome is derived from an unknown ancestral lineage of Thuja, which might explain the close resemblance of its cone morphology to that of an ancient fossil species. Overall, our study demonstrates that single genes may not resolve interspecific relationships for disjunct taxa, and that more reliable results will come from hundreds or thousands of loci, revealing a more complex evolutionary history. This will steadily improve our understanding of their origin and evolution.
... Biogeographic analysis based on the 4CL tree indicated that the most recent common ancestor (MRCA) of Thuja likely had a wide distribution in East Asia and North America [24]. Additionally, comparisons of extant species and species known only in the fossil record showed that Thuja likely first appeared at high latitudes of North America before the Paleocene and spread to eastern Asia in the Miocene [26]. Owing to the relatively incompatible phylogenetic hypotheses proposed previously, the evolutionary history of Thuja still needs further investigation. ...
... In the Late Pliocene, the fossil record of T. sutchuenensis was discovered in Shanxi Province, in northwest China. The northern Greenland cone-bearing material of T. occidentalis has been dated to the Late Pliocene to Pleistocene [26]. From paleobotanical and our phylogenomic evidence, we hypothesize that the ancestor of T. occidentalis and T. sutchuenensis Prior to this study, two relatively incompatible standpoints have been proposed to explain the biogeographic process of Thuja. ...
... While the multiple gene evidence provided by Peng and Wang [24] indicated reticulate evolution occurring in Thuja, and they inferred that Thuja could have originated from the high-latitude areas of North America, although only the 4CL gene was used. Comparative analyses using fossils suggest that Thuja likely first appeared at high latitudes of North America in or before the Paleocene and arrived in eastern Asia in the Miocene [24,26]. According to the present study, the diversification of Thuja was dated to approximately the Middle Miocene and the ancestral area was located in northern East Asia, indicating a second diversification center of Thuja in northern East Asia. ...
Investigating the biogeographical disjunction of East Asian and North American flora is key to understanding the formation and dynamics of biodiversity in the Northern Hemisphere. The small Cupressaceae genus Thuja, comprising five species, exhibits a typical disjunct distribution in East Asia and North America. Owing to obscure relationships, the biogeographical history of the genus remains controversial. Here, complete plastomes were employed to investigate the plastome evolution, phylogenetic relationships, and biogeographic history of Thuja. All plastomes of Thuja share the same gene content arranged in the same order. The loss of an IR was evident in all Thuja plastomes, and the B-arrangement as previously recognized was detected. Phylogenomic analyses resolved two sister pairs, T. standishii-T. koraiensis and T. occidentalis-T. sutchuenensis, with T. plicata sister to T. occidentalis-T. sutchuenensis. Molecular dating and biogeographic results suggest the diversification of Thuja occurred in the Middle Miocene, and the ancestral area of extant species was located in northern East Asia. Incorporating the fossil record, we inferred that Thuja likely originated from the high-latitude areas of North America in the Paleocene with a second diversification center in northern East Asia. The current geographical distribution of Thuja was likely shaped by dispersal events attributed to the Bering Land Bridge in the Miocene and subsequent vicariance events accompanying climate cooling. The potential effect of extinction may have profound influence on the biogeographical history of Thuja.
... A diagnostic value of some cone features was appreciated just as important as leaf characteristics only in a few latest studies (Cui et al., 2015;Sun et al., 2019). Our conclusions concerning the structure of the arborvitae cones are congruent with the opinion of Sun et al. (l.c.) that significant differences between the cones of Thuja occidentalis and T. plicata can be detected in the shape of the pair of the largest fertile scales, i.e. usually the second pair from the Fig. 10. ...
Thuja occidentalis and T. plicata belong to alien trees most frequently cultivated in Europe. Morphologically they differ significantly from each other and their natural ranges are geographically isolated, hence the taxonomic status of both taxa has never been questioned. In cultivation, however, these species are often very difficult to distinguish so speculations appeared that they can hybridize with each other. Reports about their hybrids growing in the Kórnik Arboretum, Poland, have been delivered several times; for the first time in 1933, then in 1957 and in 1981. In the latter publication, based on those hybrids, a new nothospecies Thuja ×plicatoides was described. That name, however, was not validly published, because its Latin diagnosis was limited only to a few words and no mention was made of how the hybrid differed from its parental species. The analysis of numerous arborvitae specimens growing in the Kórnik Arboretum, and in many other places in Poland, have shown that the earlier reports about the occurrence of Thuja hybrids in cultivation were fully justified. The results of this study were documented by numerous photographs showing the main diagnostic features of T. occidentalis, T. plicata and their hybrids. Special attention was paid to the characteristics of cones, which are rarely used in the Thuja taxonomy. The shape of cone scales, the length of the scale mucro and the structure of small ‘lips’ on the scale apices turned out to be significant cone features; the latter was used for the first time when distinguishing between both Thuja species. The cone and leaf features made it possible to recognize not only ‘pure’ species, but also their hybrids. The name Thuja ×plicatoides Seneta, for formal reasons has been rejected, so for the hybrids a new name Thuja ×senetiana has been proposed, which commemorates Włodzimierz Seneta, an outstanding Polish dendrologist.
... The fossil record of Cupressaceae is rich (Stockey et al., 2005;Taylor et al., 2009) and also extends back at least to the Jurassic with the extinct genus Austrohamia (Early Jurassic of Patagonia, Escapa et al., 2008;and Middle Jurassic of China, Zhang et al., 2012;Dong et al., 2018). Unambiguous fossils of Thuja extend back to the Arctic Paleocene (McIver and Basinger, 1989;Cui et al., 2015). Metasequoia and Sequoia are both placed in Subfamily Sequoioideae, which has extinct members that extend back to the Cretaceous (Taylor et al., 2009). ...
Plants are direct recorders of the environmental conditions in which they were growing through their carbon assimilation. Both δ13Cleaf (measured C isotopic composition of the leaf) and Δleaf (isotopic discrimination from δ13Catm by the leaf) values have been proposed to reflect a variety of environmental conditions including MAT, MAP, latitude, elevation, [CO2], and δ13Catm. Herein, we examine three sets of data from gymnosperms with long fossil records as well as selected co-occurring angiosperms to compare responses to potential environmental controls. The first dataset comprises species growing across a wide array of climatic and environmental conditions to examine MAT, MAP, latitude, and elevation. Among those potential environmental factors, none exhibits a strong control on either δ13Cleaf or Δleaf at the family, genus, or species level for either the focal gymnosperms or most of the co-occurring angiosperms. This result holds whether temperature or precipitation are considered annually or seasonally. Plant meta-analyses that have suggested a strong relationship between MAP and δ13Cleaf or Δleaf can instead be interpreted as reflecting constant Δleaf for individual species over their environmental occurrence ranges where individual ecosystems are made up of various species at different points along their individual MAP tolerance. The second dataset comes from an array of species all growing under the same environmental conditions. While differences in δ13Cleaf or Δleaf are small at the family level, at the genus and species level variation is much larger. This suggests that for any paleo-proxy reconstruction, accurate plant identification is critical to selecting the appropriate Δleaf. It also may indicate that there is an evolutionary component to measured Δleaf values, with large differences potentially between early-divergent and derived lineages. The third dataset is derived from herbarium collections of species that span the period of Industrialization (1850-present). During this time period CO2 levels have increased by ~50% and δ13Catm has shifted by >2‰ due to the burning of isotopically more negative fossil fuels. All of the historical records show that plants shifted their δ13Cleaf value, tracking the δ13Catm changes, but they did not change their Δleaf values. This contrasts strongly with some experimental results based on fast-growing herbaceous angiosperms and suggests either that there are fundamental differences between woody and herbaceous plants and/or that gymnosperms respond differently to increased CO2 than angiosperms. Finally, a brief case study is presented that examines how water use efficiency (represented by ci/ca) changed in response to elevated atmospheric CO2 levels in the Eocene to Miocene. Both Thuja and Metasequoia substantially increase their ci/ca ratios during the highest CO2 levels in the Eocene and decreased them in response to falling atmospheric CO2 during the Miocene. This suggests that the compiled Δleaf values described herein can be used to improve a variety of paleo-proxies for atmospheric CO2 levels and for plant responses to changing atmospheric stressors.
