Floristic Exchange Research Articles

Bayesian tip-dated phylogeny and biogeography of Cissampelideae (Menispermaceae): Mitigating the effects of homoplastic morphological characters.

The integration of morphological and molecular data is essential to understand the affinities of fossil taxa and spatio-temporal evolutionary processes of organisms. However, homoplastic morphological characters can mislead the placement of fossil taxa and impact downstream analyses. Here, we provide an example of how to mitigate effectively the effect of morphological homoplasy on the placement of fossil taxa and biogeographic inferences of Cissampelideae. We assembled three data types, morphological data only, morphological data with a molecular scaffold and combined morphological and molecular data. By removing high-level homoplastic morphological data or reweighting the morphological characters, we conducted 15 parsimony, 12 undated Bayesian and four dated Bayesian analyses. Our results show that the 14 selected Cissampelideae fossil taxa are placed poorly when based only on morphological data, but the addition of molecular scaffold and combination of morphological and molecular data greatly improve the resolution of fossil nodes. We raise the monotypic Stephania subg. Botryodiscia to generic status and discover that three fossils previously assigned to Stephania should be members of Diploclisia. The Bayesian tip-dated tree recovered by removing homoplastic morphological characters with a Rescaled Consistency Index <0.25 has the highest stratigraphic fit and consequently generates more reasonable biogeographic reconstruction for Cissampelideae. Cissampelideae began to diversify in Asia in the latest Cretaceous and subsequently dispersed to South America around the Cretaceous-Palaeogene boundary. Two dispersal events from Asia to Africa occurred in the Early Eocene and the Late Eocene-Late Oligocene, respectively. These findings provide guidelines and practical methods for mitigating the effects of homoplastic morphological characters on fossil placements and Bayesian tip-dating, as well as insights into the past tropical floristic exchanges among different continents.

Niche unfilling dominates the naturalization of species from intercontinentally disjunct genera

AbstractAimQuantifying niche shifts of non‐native species and their interactions with natives is vital in evaluating invasion risk yet remains difficult. Climate filtering and competition with native congeners are two important processes impacting niche changes and yielding contradictory predictions for the coexistence of non‐native and native species. Closely related species representing the Eastern Asia (EA)–Eastern North America (ENA) floristic disjunction provide a powerful yet unexplored system for assessing the relative roles of these two processes. Here, we tested three niche change scenarios (unfilling, expansion and stable) using EA species naturalized in ENA. We aim to answer: (1) which scenario is observed for naturalized species? and (2) how has niche overlap between EA and ENA congeners changed after naturalization?LocationENA and EA.Time PeriodPresent.Major Taxa StudiedAngiosperms.MethodsNiches were estimated using both occurrences and predictions generated by ecological niche models. Niche changes of naturalized species and their niche overlap with natives were measured using Schoener's D. Contributions of niche expansion and unfilling on niche changes of naturalized niches were evaluated using hierarchical partitioning and linear regressions. We further measured pairwise phylogenetic distances among EA and ENA congeners and evaluated the association with niche overlap.ResultsUnfilling‐dominated postintroduction niche changes of the naturalized species. EA species naturalized in ENA exhibited lower niche overlap with ENA native congeners compared with native range populations in EA. These results remain when considering time since introduction and potential physical dispersal limitations interpreted by projecting suitable niche space between EA and ENA. However, dispersal limitation may contribute to the degree of niche unfilling.Main ConclusionsUsing intercontinental disjunct species as a study system, we found that naturalization is shaped jointly by climate filtering and competition with native congeners, providing valuable insights for evaluating invasion risk underlying global floristic exchanges.

Sunda–Sahul floristic exchange and pathways into the Southwest Pacific: New insights from wet tropical forest trees

AbstractAimRecent investigations on the floristic exchange between Southeast Asia and Australia have shown a clear dispersal directionality bias (West to East) of wet‐adapted plant taxa. However, dispersal routes and directions of wet forest taxa into the South Pacific remain insufficiently known. We here aimed to establish the most likely routes and directions of plant dispersal into the Southwest Pacific islands.LocationSoutheast Asia, East Asia, Australia, Southwest Pacific.TaxonDysoxylum s.l. (Meliaceae). This includes Dysoxylum s.s., Didymocheton, Epicharis, Goniocheton, Pseudocarapa, and Prasoxylon.MethodWe sampled 75% of the species diversity in Dysoxylum s.l., covering the entire distribution range, all genera and major lineages. Phylogenetic relationships of 149 accessions were reconstructed using Bayesian Evolutionary Analysis and two internal constraints. The dispersal–extinction–cladogenesis variant, founder‐event speciation (DEC+J), was used for reconstructing the biogeographic history, and 100 Biogeographical Stochastic Mappings were simulated.ResultsDysoxylum s.l. originated and firstly diversified in the western part of its current distribution range (including Indochina) during the Miocene to Pliocene, followed by an overall eastern range expansion towards Malesia, Australia and the Southwest Pacific in the Pliocene.Main ConclusionsThe south‐eastward expansion of lineages into Wallacea and Australia is in temporal agreement with the convergence of the Asian and Australian tectonic plates since the Miocene. Long‐distance dispersal is the main mechanism that led to the current distribution. Two dispersal pathways into the Southwest Pacific are identified, (1) through New Guinea and the Solomon Islands to Fiji, and (2) from New Zealand to Fiji. For both routes, Fiji was an important secondary source area for dispersal into the Southwest Pacific.

Megafossils of Betulaceae from the Oligocene of Qaidam Basin and their paleoenvironmental and phytogeographic implications

Understanding the paleoenvironment and phytogeographical history of the Tibetan Plateau, China relies on discovering new plant fossils. The Qaidam Basin has long been regarded as an ideal ‘field laboratory’ to investigate the paleoclimate and paleobiological evolution of the northern Tibetan Plateau. However, fossil angiosperms from the Qaidam Basin are rare, and our knowledge of its paleovegetation is poor. Here, we report fossil leaves and fruits of Betulaceae found from the Oligocene Shangganchaigou Formation of northwestern Qaidam Basin (Huatugou area). Comparative morphological analysis led us to assign the fruits to the Betula subgenus Betula and the leaves to Carpinus grandis. These findings, together with other reported fossil plants from the same locality, reveal a close floristic linkage between the Qaidam Basin and Europe during the Oligocene. The northern pathway of this floristic exchange may have crossed through the Qaidam Basin during the late Paleogene. This floristic linkage may have been facilitated by the continuous narrowing of the Turgai Strait and stronger westerlies, which transported moisture and provided favorable climatic conditions. Indeed, fossil plants collected from the Qaidam Basin suggest that during the Oligocene this region had warm and humid deciduous broad-leaf forest, which differs from the region’s modern vegetation and indicates that the Qaidam Basin may have been a suitable region for these plants to flourish and spread during the Oligocene.

The early Eocene flora of Horsefly, British Columbia, Canada and its phytogeographic significance

About forty species, including a bryophyte, ferns, conifers, Ginkgo, and over 35 angiosperms, are recognized based on compression-impression remains from the early Eocene of Horsefly, British Colombia, Canada. This flora is in the north central part of a chain of late early Eocene fossil assemblages known as floras of the “Okanagan Highlands” (= “Okanogan Highlands” in the US). These floras extend from north central British Columbia, Canada southeast to Republic, Washington, USA. The Horsefly flora shows similarities to other Eocene Okanagan Highlands floras, such as McAbee, Falkland, Thomas Ranch and Republic, but with some additional rare taxa. In the broader sense, the Horsefly flora can be compared with early and middle Eocene floras of eastern Asia and midcontinental North America, but shares fewer elements with Europe. Ginkgo, Metasequoia, Pinus, Palaeocarpinus, ulmaceous leaves and Deviacer are shared with northeastern China as well as western North American sites. Fagopsis, Macginitiea, Dipteronia, Florissantia, Sassafras and Lagokarpos also occur in other western North American Eocene floras and Koelreuteria and Jenkinsella with Eocene paleofloras of China. These comparisons demonstrate probable floristic exchange between northwestern North America and northeastern China via a Beringian route during the late early Eocene.

Tempo and Mode of Floristic Exchanges between Hainan Island and Mainland Asia: A Case Study of the Persea Group (Lauraceae)

The origin of island biodiversity has been a topic of interest in biogeography. Two main hypotheses were suggested to explain the floristic origin of Hainan Island: ancient vicariance vs. recent dispersal. The Persea group of Lauraceae was used to examine their origin on Hainan Island. A data matrix including five genera and 49 species was assembled, phylogenetic trees of the Persea group were reconstructed using both maximum likelihood and Bayesian inference methods, and a relaxed molecular clock in BEAST was used to estimate the divergence time of the Persea group. The results showed that the Persea group diverged from its sister clade in the Eocene, and that the endemic and common species of Hainan Island and mainland Asia originated relatively late during the Miocene–Pleistocene. Species of the Persea group on Hainan may have arrived from mainland Asia via dispersal or originated via dispersal–isolation–divergence during the Miocene and Pleistocene. The results favor the dispersal hypothesis for the origin of the flora of Hainan Island and negate the vicariance hypothesis.

Phylotranscriptomics reveal the spatio-temporal distribution and morphological evolution of Macrozamia, an Australian endemic genus of Cycadales.

Cycads are regarded as an ancient lineage of living seed plants, and hold important clues to understand the early evolutionary trends of seed plants. The molecular phylogeny and spatio-temporal diversification of one of the species-rich genera of cycads, Macrozamia, have not been well reconstructed. We analysed a transcriptome dataset of 4740 single-copy nuclear genes (SCGs) of 39 Macrozamia species and two outgroup taxa. Based on concatenated (maximum parsimony, maximum likelihood) and multispecies coalescent analyses, we first establish a well-resolved phylogenetic tree of Macrozamia. To identify cyto-nuclear incongruence, the plastid protein coding genes (PCGs) from transcriptome data are extracted using the software HybPiper. Furthermore, we explore the biogeographical history of the genus and shed light on the pattern of floristic exchange between three distinct areas of Australia. Six key diagnostic characters are traced on the phylogenetic framework using two comparative methods, and infra-generic classification is investigated. The tree topologies of concatenated and multi-species coalescent analyses of SCGs are mostly congruent with a few conflicting nodes, while those from plastid PCGs show poorly supported relationships. The genus contains three major clades that correspond to their distinct distributional areas in Australia. The crown group of Macrozamia is estimated to around 11.80 Ma, with a major expansion in the last 5-6 Myr. Six morphological characters show homoplasy, and the traditional phenetic sectional division of the genus is inconsistent with this current phylogeny. This first detailed phylogenetic investigation of Macrozamia demonstrates promising prospects of SCGs in resolving phylogenetic relationships within cycads. Our study suggests that Macrozamia, once widely distributed in Australia, underwent major extinctions because of fluctuating climatic conditions such as cooling and mesic biome disappearance in the past. The current close placement of morphologically distinct species in the phylogenetic tree may be related to neotenic events that occurred in the genus.

Podocarpium (Fabaceae) from the late Eocene of central Tibetan Plateau and its biogeographic implication

Podocarpium is an extinct genus in Fabaceae with rich fossil records in Eurasia dating back to the Eocene. However, the diversification and biogeographic histories of Podocarpium are poorly known due to a lack of fossils in some key regions, such as the Tibetan Plateau, an area recently shown to be crucial for floristic exchanges worldwide in the geological past. Here, we describe well-preserved fossil pods of Podocarpium from the late Eocene (~35 Ma) of the Lunpola Basin, central Tibetan Plateau, China. Together with detailed morphological observation and geometric morphology analysis, these fossil pods are named Podocarpium tibeticum W.-C. Li, J. Huang et T. Su sp. nov., characterized by asymmetrical elliptical valves, olecranon fruit beak, and a clearly oblique base. This material comprises the oldest fossil record of Podocarpium from the Tibetan Plateau and adjacent regions. The discovery of P. tibeticum shows Podocarpium was present in central Tibet by the late Eocene. Together with previous fossil records, it indicates that Podocarpium may have originated in East Asia, migrated into the central valley of Tibet in the late Eocene, and then spread westward to Europe through a low-latitude path of island chains along the Neotethys. Results of paleoecological niche modeling demonstrate that Podocarpium had an almost worldwide potential distribution range in the Eocene, but this sharply contracted thereafter until by the Pliocene it was restricted to a small area of East Asia. Generally, this finding further supports the idea that what is now the central Tibetan Plateau was a globally significant hub for Paleogene floristic exchange.

Mummified Seed Cones of Pinus prehwangshanensis sp. nov. (Subgenus Pinus, Pinaceae) From the Upper Pleistocene of Guangdong, South China: Taxonomical Significance and Implication for Phytogeography and Ecology

Anatomical characters of Cenozoic pine seed cones are known mainly from North American fossils, while data on cone anatomy of Cenozoic species from Asia remain scarce. To date, only one seed cone of Pinus from the Miocene of eastern China has been studied using micro-computed tomography (micro-CT). A new fossil-species, Pinus prehwangshanensis sp. nov., of mummified seed cones from the upper Pleistocene of South China is described using a combination of scanning electron microscopy (SEM) and micro-CT. The new fossil-species combines a mosaic of seed cone morphological and anatomical characters observed in the group of closely related East Asian extant species of subgenus Pinus, section Pinus, subsection Pinus, comprising Pinus taiwanensis, Pinus hwangshanensis, Pinus luchuensis, Pinus thunbergii, and Pinus densiflora. The data obtained indicate that the characteristic anatomical features of this group were formed no later than the end of the Pleistocene. Based on the external seed cone morphology, the East Asian pine fossils confirm the existence of floristic exchange between continental Asia and the Japan archipelago prior to the formation of the Sea of Japan and later, in the middle Miocene to the late Pliocene, when the connection between the Japanese islands and Eurasian continent became re-established. Pollen grains associated with the new fossil-species are similar to those of some extant pine species related to P. thunbergii. A taxonomic and ecological analysis of the Pleistocene plant taxa from the Maoming Basin suggests that the regional climate was a humid subtropical monsoon with hot wet summers and cool dry winters, similar to the present-day climate of northeastern Vietnam.

The Origins and Historical Assembly of the Brazilian Caatinga Seasonally Dry Tropical Forests

The Brazilian Caatinga is considered the richest nucleus of the Seasonally Dry Tropical Forests (SDTF) in the Neotropics, also exhibiting high levels of endemism, but the timing of origin and the evolutionary causes of its plant diversification are still poorly understood. In this study, we integrate comprehensive sampled dated molecular phylogenies of multiple flowering plant groups and estimations of ancestral areas to elucidate the forces driving diversification and historical assembly in the Caatinga flowering plants. Our results show a pervasive floristic exchange between Caatinga and other neotropical regions, particularly those adjacent. While some Caatinga lineages arose in the Eocene/Oligocene, most dry-adapted endemic plant lineages found in region emerged from the middle to late Miocene until the Pleistocene, indicating that only during this period the Caatinga started to coalesce into a SDTF like we see today. Our findings are temporally congruent with global and regional aridification events and extensive denudation of thick layers of sediments in Northeast (NE) Brazil. We hypothesize that global aridification processes have played important role in the ancient plant assembly and long-term Caatinga SDTF biome stability, whereas climate-induced vegetation shifts, as well as the newly opened habitats have largely contributed as drivers of in situ diversification in the region. Patterns of phylogenetic relatedness of Caatinga endemic clades revealed that much modern species diversity has originated in situ and likely evolved via recent (Pliocene/Pleistocene) ecological specialization triggered by increased environmental heterogeneity and the exhumation of edaphically disparate substrates. The continuous assembly of dry-adapted flora of the Caatinga has been complex, adding to growing evidence that the origins and historical assembly of the distinct SDTF patches are idiosyncratic across the Neotropics, driven not just by continental-scale processes but also by unique features of regional-scale geological history.

The global loss of floristic uniqueness

Regional species assemblages have been shaped by colonization, speciation and extinction over millions of years. Humans have altered biogeography by introducing species to new ranges. However, an analysis of how strongly naturalized plant species (i.e. alien plants that have established self-sustaining populations) affect the taxonomic and phylogenetic uniqueness of regional floras globally is still missing. Here, we present such an analysis with data from native and naturalized alien floras in 658 regions around the world. We find strong taxonomic and phylogenetic floristic homogenization overall, and that the natural decline in floristic similarity with increasing geographic distance is weakened by naturalized species. Floristic homogenization increases with climatic similarity, which emphasizes the importance of climate matching in plant naturalization. Moreover, floristic homogenization is greater between regions with current or past administrative relationships, indicating that being part of the same country as well as historical colonial ties facilitate floristic exchange, most likely due to more intensive trade and transport between such regions. Our findings show that naturalization of alien plants threatens taxonomic and phylogenetic uniqueness of regional floras globally. Unless more effective biosecurity measures are implemented, it is likely that with ongoing globalization, even the most distant regions will lose their floristic uniqueness.

Megaporoxylon sinensis sp. nov., a new coniferous trunk from the Upper Triassic of northern Bogda Mountains, northwestern China

A coniferous trunk, Megaporoxylon sinensis sp. nov., is described from the Carnian–Norian (Triassic) Huangshanjie Formation in the Dalongkou section, Jimsar County, Xinjiang, northwestern China. The trunk is composed of pith, primary and secondary xylem. The pith is solid, circular, heterocellular, with pitted parenchyma and secretory cells and canals. The primary xylem is endarch, with spiral and scalariform thickenings on tracheidal walls. The secondary xylem is pycnoxylic, consisting of tracheids and rays. Radial tracheidal pitting is araucarian. Tangential pitting and axial parenchyma are absent. Uniseriate pits with oval apertures are commonly present on radial tracheid walls. Biseriate pitting occurs only on radial walls of the first to fifth tracheids outward the primary xylem. Rays are parenchymatous, uniseriate, and 1–7 cells high. Cross-field pitting is window-like or phyllocladoid. Previous records of species of Megaporoxylon Kräusel were limited to the Southern Hemisphere during the Carboniferous to Triassic. Its occurrence from the Upper Triassic of northern Xinjiang is the first report in the Northern Hemisphere and suggests a floristic exchange between Gondwana and Laurasia. The new trunk and two previously described fossil stems, including Medulloprotaxodioxylon triassicum Wan et al. and Xenoxylon junggarensis Wan et al., demonstrate that conifers were important elements of Carnian–Norian terrestrial ecosystems and had a higher diversity in northern China than previous thought. The growth ring pattern of the trunk and palaeogeographic reconstruction of the research area at high latitudes suggest that the growth of the trees was limited by the seasonality of the light regime.

Historical biogeography of Tetrastigma (Vitaceae): Insights into floristic exchange patterns between Asia and Australia.

Biodiversity exchanges across the Malesian region, linking the distinct biotas of Asia and Australia, have long attracted the curiosity of biologists. Tetrastigma (Vitaceae) has a wide distribution in Asia through the Sunda archipelago to Australia and provides a good case to elucidate floristic exchange between Asia and Australia. Tetrastigma species have fleshy fruits that are consumed by birds, representing a lineage with a predictable dispersal across island chains. We herein estimate the divergence times and reconstruct the biogeographic history of Tetrastigma with intensive taxon sampling (96 of approximately 120 species; >80%) using 10 chloroplast loci. The biogeographic history of Tetrastigma was reconstructed with 4-area and 6-area divisions by delineating the Sunda region into one or three areas of endemism based on a phylogenetic bioregionalization analysis and the geological history of Malesia. The 4-area division shows that Tetrastigma originated in continental Asia and diverged from the recently segregated genus Pseudocayratia in the early Eocene (49.43 Ma). Dispersal from continental Asia might have started in the late Eocene but mainly occurred in the last 10 Myr. Continental Asia is indicated to be the most important source area while Sunda is the biggest sink, with 16 of the 27 dispersal events inferred from continental Asia to Sunda. Only seven dispersal events are inferred arriving in the Sahul plate and one reverse dispersal from Sahul back to Asia. The 6-area division suggests that the Philippines have been an active junction between Asia and Australia. The biogeographic history of Tetrastigma illustrates an asymmetric floristic exchange between Asia and Australia in this genus, which has been facilitated by the formation of terrestrial connections in the late Miocene and the expansion of wet tropical forests across Wallace's Line and beyond.

Environmental variables and dispersal barriers explain broad‐scale variation in tree species composition across Neotropical non‐flooded evergreen forests

AbstractQuestionsWe examined the drivers of tree species variation across Neotropical non‐flooded evergreen forests (NNFEFs) to answer the following questions: can floristic groups be differentiated based on environmental predictors? How do bioclimatic, topographic, edaphic predictors and dispersal barriers contribute to explain the floristic variation throughout NNFEFs?LocationNeotropical region.MethodsBased on 1,843 sites (circular areas with a diameter of 10 km), 15,072 species and 509,793 occurrence records of trees, as well as on environmental variables (42 bioclimatic, 13 edaphic and four topographic variables) and dispersal barriers (based on ecological and geographical dispersal suitability), we tested whether environmental predictive variables can discriminate NNFEF floristic groups, and built canonical models and variation partitioning to assess which variables contributed most to the floristic variation.ResultsDespite extensive overlap in predictive variables, Amazon and Atlantic Forest were the most differentiated among the nine NNFEF groups. Floristic variation along NNFEFs was mainly determined by environmental factors (54.1%), with topographic and edaphic variables, mainly topographic wetness index and pH respectively, representing the most important predictors followed by a combination of environmental factors and dispersal barriers (22.7%). The fraction of pure dispersal barriers also contributed significantly to our model (3.7%), especially considering the second canonical axis.ConclusionsThe high importance of soil and topographic variables indicates that the species have a relatively narrow niche driven by such factors, suggesting that conservation strategies should not be generalized for NNFEFs. In addition, dispersal barriers do not seem to have prevented floristic exchanges between most NNFEF groups, except in the Atlantic Forest.

At a crossroads: The late Eocene flora of central Myanmar owes its composition to plate collision and tropical climate

Myanmar was shaped by the India-Asia collision, fusion of the Burma Terrane (BT) with Asia, and mountain building. Throughout this process new elevational gradients and habitats were formed, which affected the regional climate, but also forged new dispersal routes into Asia and India. In spite of its importance, the vegetation history of Myanmar is poorly known, and this hinders our understanding on the origins and evolution of SE Asian biodiversity. In this study we reconstruct the late Eocene flora in central Myanmar, based on samples from a sedimentary succession in Kalewa, and extend on the Sapotaceae fossil record with additional early Eocene–early Oligocene samples. We then study the morphology, botanical affinity, source ecology and biogeography of selected sporomorphs, and assess the Gondwanan and Laurasian components. Our results show that this late Eocene palynoflora is representative for evergreen forests, typical in a seasonal wet climate, with dryer vegetation away from the area of sedimentation. The abundance of Sapotaceae further suggests that this family became an important component of the SE Asian flora shortly after the India-Asia collision. We conclude that the late Eocene geographic position and Gondwanan origin of Myanmar facilitated floristic exchange between the Indian Plate, BT, mainland and SE Asia, making the BT a crossroads for plant dispersals between Gondwana and Laurasia. The shift from late Eocene seasonal evergreen to present-day moist deciduous forests was likely due to the northward drift of Myanmar, the subsequent two-stage uplift of the Indo-Burman Ranges and posterior Neogene global cooling and drying.

Molecular phylogeography reveals two geographically and temporally separated floristic exchange tracks between Southeast Asia and northern Australia

AbstractAimExchange of plant lineages between Australia and Southeast Asia has had a substantial impact on the evolution of Australia's northern, tropical flora, with important ramifications for its conservation and biosecurity. Despite this, floristic exchange tracks between northern Australia and Southeast Asia remain poorly understood. To address this, we conducted a molecular phylogeographic case study to identify exchange tracks between Australia and Southeast Asia.LocationIndia, Southeast Asia, Australia and Pacific islands.TaxonThe widespread tropical monsoonal tree species Aglaia elaeagnoidea (Meliaceae).MethodsWe conducted a DArTseq phylogeographic study of 141 herbarium and silica‐dried samples sourced from across the range of A. elaeagnoidea. We analysed 176,331 single nucleotide polymorphisms (SNPs) across 90,456 loci using multivariate, admixture, genetic differentiation and coalescent methods to characterise phylogeographic and phylogenetic patterns. These analyses were considered in the context of an environmental niche model for the last glacial maximum.ResultsTwo exchange tracks were identified: one from New Guinea to Cape York Peninsula in north‐east Australia, and a second from Timor‐Leste to the Kimberley Plateau of north‐west Australia. The Cape York Peninsula track is contemporary, characterised by ongoing genetic exchange, whereas the Kimberley Plateau track is historic, facilitated by multiple past exposures of the Arafura Shelf during the Pleistocene. Overall, we suggest that phylogeographic patterns of A. elaeagnoidea have resulted from a combination of repeated range expansion and contraction cycles concurrent with Quaternary climate fluctuations and stochastic dispersal events.Main conclusionsThis study provides the first molecular phylogeographic evidence for two floristic exchange tracks between northern Australia and Southeast Asia. It also highlights the influence of Quaternary climate fluctuations on the complex biogeography of the region, and supports the idea that the Kimberley Plateau and Cape York Peninsula in northern Australia have separate biogeographic histories.

Plants will cross the lines: climate and available land mass are the major determinants of phytogeographical patterns in the Sunda–Sahul Convergence Zone

AbstractThe Miocene convergence of the Sunda shelf, Sahul shelf and Wallacea facilitated the exchange of previously isolated floras across the Sunda–Sahul Convergence Zone (SSCZ). The SSCZ is a hotspot of biogeographical research; however, phytogeographical patterns across the region remain poorly understood. We conducted multivariate analysis on a comprehensive species checklist of SSCZ vascular plants to quantify the extent of exchange, characterize phytogeographical patterns and investigate their abiotic drivers. We found that Lydekker’s and Wallace’s Lines are not reflected in floristic composition at any taxonomic level, with 46% of genera distributed across these biogeographical lines. In contrast, environment is significantly correlated with floristic composition, with annual rainfall and seasonality being the strongest correlates. Mainland Asia, Borneo, the Philippines, New Guinea and Australia were major routes of exchange throughout the Cenozoic, possibly because these areas have been persistent landmasses throughout the entire period of convergence. We conclude that Sunda–Sahul floristic exchange has substantially influenced the assembly of the regional flora and that modern phytogeographical patterns have been influenced more by environmental variables and available landmass (i.e. establishment conditions) than by putative barriers to movement such as Wallace’s and Lydekker’s Lines (i.e. vagility).

Out of the Mediterranean Region: Worldwide biogeography of snapdragons and relatives (tribe Antirrhineae, Plantaginaceae)

AbstractAimThe tribe Antirrhineae, including snapdragons, toadflaxes and relatives, is widely distributed across the Northern Hemisphere and the Neotropics. It displays an uneven distribution of diversity, with more than 50% of species and subspecies in the Mediterranean Region. Here we conducted the first detailed, worldwide biogeographic analysis of the Antirrhineae and tested two alternative hypotheses (time‐for‐speciation versus diversification rate differences) to explain the uneven distribution of diversity.LocationWorldwide, with a focus on the Mediterranean Region.TaxonTribe Antirrhineae (Plantaginaceae).MethodsA phylogenetic biogeographic approach was taken, accounting for area connections through time. Ancestral ranges, dispersal events, speciation and lineage accumulation within areas were estimated. Diversification rates for taxa present and absent in the Mediterranean Region were compared, accounting for the effect of a floral key innovation (nectar spur).ResultsA proto‐Mediterranean origin in the Late Eocene was estimated, and the Mediterranean Region stood out as the main centre for speciation and dispersal. Congruent patterns of long‐distance dispersal from the Mediterranean Region to North America were recovered for at least two amphiatlantic clades. A significant floristic exchange between the Mediterranean and south‐western Asia was detected. We found no evidence of different diversification rates between lineages inside and outside the Mediterranean Region.Main conclusionsThe Mediterranean Region played a key role in the origin of the current distribution of the Antirrhineae. However, the higher species richness found in this region appears to be the result of a time‐for‐speciation effect rather than that of increased diversification rates. The establishment of current Mediterranean climates in the Northern Hemisphere appears to have contributed to the recent diversification of the group, in combination with colonization of adjacent regions with arid and semi‐arid climates.

Museomics for reconstructing historical floristic exchanges: Divergence of stone oaks across Wallacea.

Natural history collections and tropical tree diversity are both treasure troves of biological and evolutionary information, but their accessibility for scientific study is impeded by a number of properties. DNA in historical specimens is generally highly fragmented, complicating the recovery of high-grade genetic material. Furthermore, our understanding of hyperdiverse, wide-spread tree assemblages is obstructed by extensive species ranges, fragmented knowledge of tropical tree diversity and phenology, and a widespread lack of species-level diagnostic characters, prohibiting the collecting of readily identifiable specimens which can be used to build, revise or strengthen taxonomic frameworks. This, in turn, delays the application of downstream conservation action. A sizable component of botanical collections are sterile—thus eluding identification and are slowing down progress in systematic treatments of tropical biodiversity. With rapid advances in genomics and bioinformatic approaches to biodiversity research, museomics is emerging as a new field breathing life into natural collections that have been built up over centuries. Using MIGseq (multiplexed ISSR genotyping by sequencing), we generated 10,000s of short loci, for both freshly collected materials and museum specimens (aged >100 years) of Lithocarpus—a widespread tropical tree genus endemic to the Asian tropics. Loci recovery from historical and recently collected samples was not affected by sample age and preservation history of the study material, underscoring the reliability and flexibility of the MIGseq approach. Phylogenomic inference and biogeographic reconstruction across insular Asia, highlights repeated migration and diversification patterns between continental regions and islands. Results indicate that co-occurring insular species at the extremity of the distribution range are not monophyletic, raising the possibility of multiple independent dispersals along the outer edge of Wallacea. This suggests that dispersal of large seeded tree genera throughout Malesia and across Wallacea may have been less affected by large geographic distances and the presence of marine barriers than generally assumed. We demonstrate the utility of MIGseq in museomic studies using non-model taxa, presenting the first range-wide genomic assessment of Lithocarpus and tropical Fagaceae as a proof-of-concept. Our study shows the potential for developing innovative genomic approaches to improve the capture of novel evolutionary signals using valuable natural history collections of hyperdiverse taxa.

A molecular phylogeny of Southeast Asian Cyrtandra (Gesneriaceae) supports an emerging paradigm for Malesian plant biogeography

The islands of Southeast Asia comprise one of the most geologically and biogeographically complex areas in the world and are a centre of exceptional floristic diversity, harbouring 45,000 species of flowering plants. Cyrtandra, with over 800 species of herbs and shrubs, is the largest genus in the family Gesneriaceae and is one of the most emblematic and species-rich genera of the Malesian rainforest understorey. The high number of species and tendency to narrow endemism make Cyrtandra an ideal genus for examining biogeographic patterns. We sampled 128 Cyrtandra taxa from key localities across Southeast Asia to evaluate the geo-temporal patterns and evolutionary dynamics of this clade. One nuclear and four chloroplast regions were used for phylogenetic reconstruction, molecular dating, and ancestral range estimation. Results from the dating analysis suggest that the great diversity of Cyrtandra seen in the Malesian region results from a recent radiation, with most speciation taking place in the last five million years. Borneo was recovered as the most likely ancestral range of the genus, with the current distribution of species resulting from a west to east migration across Malesia that corresponds with island emergence and mountain building. Lastly, our investigation into the biogeographic history of the genus indicates high levels of floristic exchange between the islands on the Sunda shelf and the important role of the Philippines as a stepping stone to Wallacea and New Guinea. These patterns underlie much of the plant diversity in the region and form an emerging paradigm in Southeast Asian plant biogeography.