Alien flora are accumulating steadily in China over the last 80 years.

New alien species are increasingly introduced and established outside their native range. The knowledge of the spatiotemporal dynamics of their accumulation and the factors determining their residence time in the introduced range is critical for proactive management, especially in emerging economies. Based on a comprehensive time series dataset of 721 alien angiosperms in China, we show that new alien flora has been accumulating steadily in China, particularly in the coastal regions, for the last 80 years without saturation. The ability to occupy a large number of habitats facilitates the early introduction of alien flora, whereas a large naturalized range, greater number of uses, and multiple introduction pathways directly contribute to their naturalization and invasion. The temporal pattern is predicted to remain consistent in the foreseeable future. We propose upgrading the country's biosecurity infrastructure based on a standardized risk assessment framework to safeguard the country from ongoing and future invasions.

Invasive alien plants are phylogenetically distinct from other alien species across spatial and taxonomic scales in China.

Introduction: Phylogenetic relatedness is one of the important factors in the community assembly process. Here, we aimed to understand the large-scale phylogenetic relationship between alien plant species at different stages of the invasion process and how these relationships change in response to the environmental filtering process at multiple spatial scales and different phylogenetic extents. Methods: We identified the alien species in three invasion stages, namely invasive, naturalized, and introduced, in China. The occurrence records of the species were used to quantify two abundance-based phylogenetic metrics [the net relatedness index (NRI) and the nearest taxon index (NTI)] from a highly resolved phylogenetic tree. The metrics were compared between the three categories of alien species. Generalized linear models were used to test the effect of climate on the phylogenetic pattern. All analyses were conducted at four spatial scales and for three major angiosperm families. Results: We observed significantly higher NRI and NTI values at finer spatial scales, indicating the formation of more clustered assemblages of phylogenetically closely related species in response to the environmental filtering process. Positive NTI values for the invasive and naturalized aliens suggested that the presence of a close relative in the community may help the successful naturalization and invasion of the introduced alien species. In the two-dimensional phylogenetic space, the invasive species communities significantly differed from the naturalized and introduced species, indicating that established alien species need to be phylogenetically different to become invasive. Positive phylogenetic measures for the invasive aliens across the spatial scales suggested that the presence of invasive aliens could facilitate the establishment of other invasive species. Phylogenetic relatedness was more influenced by temperature than precipitation, especially at a finer spatial scale. With decreased temperature, the invasive species showed a more clustered assemblage, indicating conservatism of their phylogenetic niche. The phylogenetic pattern was different at the family level, although there was a consistent tendency across families to form more clustered assemblages. Discussion: Overall, our study showed that the community assemblage became more clustered with the progression of the invasion process. The phylogenetic measures varied at spatial and taxonomic scales, thereby highlighting the importance of assessing phylogenetic patterns at different gradients of the community assembly process.

Interspecific variation and phylogenetic relationship between mangrove and non-mangrove species of a same family (Meliaceae)-insights from comparative analysis of complete chloroplast genome.

The mahogany family, Meliaceae, contains 58 genera with only one mangrove genus: Xylocarpus. Two of the three species of the genus Xylocarpus are true mangroves (X. granatum and X. moluccensis), and one is a non-mangrove (X. rumphii). In order to resolve the phylogenetic relationship between the mangrove and non-mangrove species, we sequenced chloroplast genomes of these Xylocarpus species along with two non-mangrove species of the Meliaceae family (Carapa guianensis and Swietenia macrophylla) and compared the genome features and variations across the five species. The five Meliaceae species shared 130 genes (85 protein-coding genes, 37 tRNA, and eight rRNA) with identical direction and order, with a few variations in genes and intergenic spacers. The repetitive sequences identified in the rpl22 gene region only occurred in Xylocarpus, while the repetitive sequences in accD were found in X. moluccensis and X. rumphii. The TrnH-GUG and rpl32 gene regions and four non-coding gene regions showed high variabilities between X. granatum and the two non-mangrove species (S. macrophylla and C. guianensis). In addition, among the Xylocarpus species, only two genes (accD and clpP) showed positive selection. Carapa guianensis and S. macrophylla owned unique RNA editing sites. The above genes played an important role in acclimation to different stress factors like heat, low temperature, high UV light, and high salinity. Phylogenetic analysis with 22 species in the order Sapindales supported previous studies, which revealed that the non-mangrove species X. rumphii is closer to X. moluccensis than X. granatum. Overall, our results provided important insights into the variation of genetic structure and adaptation mechanism at interspecific (three Xylocarpus species) and intergeneric (mangrove and non-mangrove genera) levels.

Implications for biological invasion of non-native plants for sale in the world's largest online market.

Internet trade is increasingly recognized as a dispersal pathway of non-native plant species that is difficult to monitor. We sought to identify non-native flora present in the Chinese online market, the largest e-commerce market globally, and to decipher the effect of existing trade regulations, among other variables, on e-trading patterns and to inform policy. We used a comprehensive list of 811 non-native plant species in China present in 1 of the 3 phases of the invasion continuum (i.e., introduced, naturalized, and invasive). The price, propagule types, and quantities of the species offered for sale were retrieved from 9 online stores, including 2 of the largest platforms. Over 30% of the non-native species were offered for sale in the online marketplaces; invasive non-native species dominated the list (45.53%). No significant price difference was observed across the non-native species of the 3 invasion categories. Among the 5 propagule types, a significantly higher number of non-native species were offered for sale as seeds. The regression models and path analyses consistently revealed a direct positive effect of the number of uses and species' minimum residence time and an indirect effect of biogeography on the pattern of trade in non-native plant species when minimal phylogenetic signal was detected. A review of the existing phytosanitary regulations in China revealed their inadequacy in managing e-trading of non-native plant species. To address the problem, we propose integration of a standardized risk assessment framework that considers perceptions of stakeholders and is adaptable based on continuous surveillance of the trade network. If implemented successfully, the measures could provide a template for other countries to strengthen trading regulations for non-native plant species and take proactive management measures.

La venta de plantas no nativas en el mercado virtual más grande y sus implicaciones para la invasión biológica Resumen El mercado virtual en internet se reconoce cada vez más como una vía de dispersión de especies vegetales no nativas difícil de controlar. Intentamos identificar la flora no nativa presente en el mercado virtual chino, el mayor mercado de comercio electrónico del mundo, para descifrar el efecto de las regulaciones comerciales vigentes, entre otras variables, en los patrones de comercio electrónico e informar a las políticas. Utilizamos una lista integral de 811 especies de plantas no nativas de China presentes en una de las tres fases de invasión (es decir, introducidas, naturalizadas o invasoras). El precio, los tipos de propágulos y las cantidades de las especies puestas a la venta se recuperaron de nueve tiendas en línea, incluidas dos de las mayores plataformas. Más del 30% de las especies no nativas se pusieron a la venta en los mercados en línea; las especies no nativas invasoras dominaron esta lista (45,53%). No se observaron diferencias significativas de precio entre las especies no nativas en las tres categorías de invasión. Entre los cinco tipos de propágulos, se puso a la venta un número significativamente mayor de especies no nativas en forma de semillas. Los modelos de regresión y los análisis de trayectoria revelaron un efecto positivo directo y constante del número de usos y del tiempo mínimo de residencia de las especies y un efecto indirecto de la biogeografía sobre el patrón de comercio de especies vegetales no nativas cuando se detectó una señal filogenética mínima. Una revisión de la normativa fitosanitaria vigente en China reveló su insuficiencia para gestionar el comercio electrónico de las especies vegetales no nativas. Para abordar el problema, proponemos la integración de un marco normalizado de evaluación de riesgos que tenga en cuenta las percepciones de los actores y sea adaptable en función de la vigilancia continua de la red comercial. Si se aplican con éxito, las medidas podrían servir de modelo para que otros países refuercen la normativa sobre comercio de especies vegetales no nativas y adopten medidas proactivas de gestión.

Characterization of the complete chloroplast genome of Firmiana hainanensis (Malvaceae), an endemic and vulnerable tree species of China.

Firmiana hainanensis Kosterm. is a commercially valuable endemic tree species in China and has long been considered a globally vulnerable species. We assembled and characterized the complete chloroplast genome of this species by using Illumina pair-end sequencing data. The total chloroplast genome size was 161,559 bp, including two inverted repeats (IRs) of 25,612 bp, separated by a large single copy (LSC) and a small single copy (SSC) regions of 90,057 and 20,277 bp, respectively. A total of 130 genes were identified, including 85 protein-coding genes, 37 tRNA, and eight rRNA genes. Phylogenetic analysis showed that F. hainanensis was the most basal species in the genus Firmiana. The chloroplast genome of this species will provide a theoretical basis to understand the taxa's evolution further and is expected to contribute to its conservation efforts.

An occurrence data set for invasive and naturalized alien plants in India.

India has numerous invasive alien plant species (IAPSs), which seriously impact biodiversity, ecosystem services, and economic development. The availability of reliable occurrence records of IAPSs is of great importance for their successful management, prediction of distribution across time and space, and other research and development efforts. Global databases of occurrence data, like the Global Biodiversity Information Facility (GBIF), are often not exhaustive, especially for India, and poorly represent the actual distribution of IAPSs in the country. Our objective in creating this data set was threefold: (1) to compile occurrence data for the invasive and naturalized alien plant species of India, (2) to collect spatial and temporal information associated with occurrence records, and (3) to share the data in an accessible format so every record is traceable to its sources and allow users to submit data to increase the resolution of the data set. To achieve these objectives, we extracted data from 3137 literature records and 357 herbarium sheets. For each occurrence record, we curated information for 20 variables, which were arranged in a table with the Darwin Core (DwC) terms as column names. All data were subjected to technical validation before being included in the database. A total of 12,347 occurrence records were obtained for 362 species (195 invasive aliens and 167 naturalized aliens). The number of collected occurrence records was much higher for the invasive aliens (73.7%) than for the naturalized alien species (26.3%). Our data set will supplement the GBIF data by 60.39%, and occurrence records will be added for 64 invasive and naturalized alien plant species. The data set, as a part of the larger database of the Indian Alien Flora Information (ILORA) database, is made available without any restrictions on use as long as this data paper is properly cited. We have also made provisions for users to submit occurrence-related data following a data standard. The users are encouraged to cite the original reference when using a specific data record. The data set is expected to assist a wide range of stakeholders involved in India's scientific research, policy formulation, and decision-making related to IAPSs.

Glacial vicariance and oceanic circulation shape population structure of the coastal legume Derris trifoliata in the Indo-West Pacific.

PREMISE: The phylogeography of coastal plant species is shaped by contemporary and historical biogeographic processes. In this study, we aim to decipher the phylogeography of Derris trifoliata, a woody legume of relatively recent origin and wide distribution, in coastal areas in the Indo-West Pacific (IWP) region. METHODS: Genetic diversity and population structure were assessed by analyzing six nuclear and three chloroplast DNA sequences from 30 populations across the species' range. Phylogeography was inferred by estimating gene flow, divergence time, historical population size changes, and historical habitat suitability using paleoclimatic niche modeling. RESULTS: High genetic diversity was observed at the species level. The populations of three oceanic regions included in this study (i.e., Indian Ocean, South China Sea, and Pacific Ocean) formed distinct clades and likely diverged during the late Pleistocene. Potential barriers to gene flow were identified, including the Sunda and Sahul shelves, geographic distance, and current patterns of oceanic circulation. Analysis of changes in population size supported the bottleneck model, which was strengthened by estimates of habitat suitability across paleoclimatic conditions. CONCLUSIONS: The once widespread distribution of D. trifoliata was fragmented by changes in climatic suitability and biogeographic barriers that arose following sea-level changes during the Pleistocene. In addition, contemporary patterns of oceanic circulation and geographic distance between populations appear to maintain genetic differentiation across its distribution in the IWP.

Setting the priorities straight - Species distribution models assist to prioritize conservation targets for the mangroves.

Mangrove forests provide a wide range of ecosystem services, yet they are declining rapidly due to climate change and human activities. Identification of conservation priority targets across spatial and temporal scales may assist in planning and decision making, especially in areas having rich mangrove diversity but with limited response capacity. In this study, we aimed to identify the species and areas which should be prioritized for conservation in the Indo-West Pacific (IWP) region, one of the two global hotspots of mangroves. We used an ensemble species distribution modelling framework to map the potential distribution of ten species, including true mangroves and mangrove associates, in current, past, and future environmental conditions. The priority targets were then identified through a weighted-scoring approach with the current distribution and the modelled outputs. Our study revealed that precipitation and surface elevation could influence the distribution of the true mangroves, while the temperature was the important variable for the mangrove associates. Although suitable habitat for the mangroves is predicted to increase in future, primarily due to the northward range expansion of six species, areas with high species richness would decrease. We found 7.09% and 4.16% areas of the IWP should be prioritized for conservation of the true mangroves and mangrove associates, respectively. The characteristics of these priority sites indicated that the inclusion of the anthropogenic component in the conservation framework and species-targeted management plans in the protected areas are required for the effective implementation of conservation actions. Five of the studied species, namely Acanthus ilicifolius, Dolichandrone spathacea, Heritiera littoralis, Pemphis acidula and Xylocarpus granatum, were found to have the highest priority score for conservation. The glacial refugia of the species, mostly distributed in the Philippines, New Guinea, southern India and Madagascar, should be explored further for species-specific conservation actions.

Phylogeographic pattern of a cryptoviviparous mangrove, Aegiceras corniculatum, in the Indo-West Pacific, provides insights for conservation actions.

MAIN CONCLUSION: This study identified the historical geoclimatic factors which caused low genetic diversity and strong phylogeographic structure in a cryptoviviparous mangrove. The phylogeographic pattern was used to suggest conservation actions. Phylogeographic studies are used to understand the spatial distribution and evolution of genetic diversity, and have major conservation implications, especially for threatened taxa like the mangroves. This study aimed to assess the phylogeographic pattern of Aegiceras corniculatum, a cryptoviviparous mangrove, across its distribution range in the Indo-West Pacific (IWP) region. We genotyped 398 samples, collected from 37 populations, at four chloroplast DNA (cpDNA) loci, and identified the influence of historical processes on the contemporary population structure of the species. Low genetic diversity at the population level was observed. The evolutionary relationship between 12 cpDNA haplotypes suggested a strong phylogeographic structure, which was further validated by the clustering algorithms and proportioning of maximum variation among hierarchical population groups. The magnitude and direction of historical gene flow indicated that the species attained its wide distribution from its likely ancestral area of the Malay Archipelago. The divergence time estimates of the haplotypes indicated that the geoclimatic changes during the Pleistocene, especially the glacial sea-level changes and emergence of landmasses, hindered genetic exchange and created genetic differentiation between the phylogenetic groups. The species overwintered the last glacial maxima in multiple refugia in the IWP, as identified by the environmental niche modelling. Overall, our findings indicated that ancient glacial vicariance had influenced the present genetic composition of A. corniculatum, which was maintained by the current demographic features of this region. We discussed how these findings can be used to prioritize areas for conservation actions, restore disturbed habitats and prevent further genetic erosion.

Contrasting Phylogeographic Patterns in Lumnitzera Mangroves Across the Indo-West Pacific.

Mangroves are ecologically important forest communities in tropical and subtropical coasts, the effective management of which requires understanding of their phylogeographic patterns. However, these patterns often vary among different species, even among ecologically similar taxa or congeneric species. Here, we investigated the levels and patterns of genetic variation within Lumnitzera consisting of two species (L. racemosa and L. littorea) with nearly sympatric ranges across the Indo-West Pacific (IWP) region by sequencing three chloroplast DNA regions (for both species) and genotyping 11 nuclear microsatellite loci (for L. littorea). Consistent with findings in studies on other mangrove species, we found that both L. racemosa and L. littorea showed relatively high genetic variation among populations but low genetic variation within populations. Haplotype network and genetic clustering analyses indicated two well-differentiated clades in both L. racemosa and L. littorea. The relationship between geographic and genetic distances and divergence time estimates of the haplotypes indicated that limited dispersal ability of the propagules, emergence of land barriers during ancient sea-level changes, and contemporary oceanic circulation pattern in the IWP influenced the current population structure of the two species. However, the position of genetic break was found to vary between the two species: in L. racemosa, strong divergence was observed between populations from the Indian Ocean and the Pacific Ocean possibly due to land barrier effect of the Malay Peninsula; in L. littorea, the phylogeographic pattern was created by a more eastward genetic break along the biogeographic barrier identified as the Huxley's line. Overall, our findings strongly supported previous hypothesis of mangrove species divergence and revealed that the two Lumnitzera species have different phylogeographic patterns despite their close genetic relationship and similar current geographic distribution. The findings also provided references for the management of Lumnitzera mangroves, especially for the threatened L. littorea.

Different factors influence naturalization and invasion processes - A case study of Indian alien flora provides management insights.

Why do some alien plants become naturalized, and some naturalized become invasive? Do different factors determine successful naturalization and invasion? Most, if not all, studies addressing these questions have focused either on the part of the invasion continuum or a specific group of alien species. In this study, we aimed to answer these questions for alien plant invasion in India by considering 13 variables related to biogeography, introduction pathways, uses, functional traits, and distribution for 715 species belonging to three invasion categories. We deciphered the variables' influence on successful naturalization and invasion through a structural equation modeling framework implemented as path analyses and translated the findings to management implications. Our study revealed that the invasive aliens had significantly higher naturalized range size, a greater number of uses, and higher specific leaf area than the naturalized and casual aliens. Path analyses revealed that the native and naturalized range sizes, number of uses, and growth form had a direct influence on naturalization success, whereas longer minimum residence time (MRT) facilitated overcoming of the dispersal barrier for naturalized species. Invasion success was directly influenced by the MRT and number of uses, which were further influenced by the number of native congeners and the naturalized range size, respectively. Plant growth forms indirectly influenced invasion success, whereas the native range sizes had indirect effects on successful naturalization and invasion by strongly influencing the size of the naturalized range. Our findings suggested considering species biogeography in the formulation of quarantine measures, imposing policies to discourage the uses and spread of alien plants within the country, and implementing early control measures, especially for the naturalized aliens. The curated dataset used in this study would also provide a ready reference for future research and decision-making towards the management of alien plant invasion in the country.

Land masses and oceanic currents drive population structure of Heritiera littoralis, a widespread mangrove in the Indo-West Pacific.

Phylogeographic forces driving evolution of sea-dispersed plants are often influenced by regional and species characteristics, although not yet deciphered at a large spatial scale for many taxa like the mangrove species Heritiera littoralis. This study aimed to assess geographic distribution of genetic variation of this widespread mangrove in the Indo-West Pacific region and identify the phylogeographic factors influencing its present-day distribution. Analysis of five chloroplast DNA fragments' sequences from 37 populations revealed low genetic diversity at the population level and strong genetic structure of H. littoralis in this region. The estimated divergence times between the major genetic lineages indicated that glacial level changes during the Pleistocene epoch induced strong genetic differentiation across the Indian and Pacific Oceans. In comparison to the strong genetic break imposed by the Sunda Shelf toward splitting the lineages of the Indian and Pacific Oceans, the genetic differentiation between Indo-Malesia and Australasia was not so prominent. Long-distance dispersal ability of H. littoralis propagules helped the species to attain transoceanic distribution not only across South East Asia and Australia, but also across the Indian Ocean to East Africa. However, oceanic circulation pattern in the South China Sea was found to act as a barrier creating further intraoceanic genetic differentiation. Overall, phylogeographic analysis in this study revealed that glacial vicariance had profound influence on population differentiation in H. littoralis and caused low genetic diversity except for the refugia populations near the equator which might have persisted through glacial maxima. With increasing loss of suitable habitats due to anthropogenic activities, these findings therefore emphasize the urgent need for conservation actions for all populations throughout the distribution range of H. littoralis.

Going with the flow: analysis of population structure reveals high gene flow shaping invasion pattern and inducing range expansion of Mikania micrantha in Asia.

BACKGROUND AND AIMS: Mikania micrantha, a climbing perennial weed of the family Asteraceae, is native to Latin America and is highly invasive in the tropical belt of Asia, Oceania and Australia. This study was framed to investigate the population structure of M. micrantha at a large spatial scale in Asia and to identify how introduction history, evolutionary forces and landscape features influenced the genetic pattern of the species in this region. METHODS: We assessed the genetic diversity and structure of 1052 individuals from 46 populations for 12 microsatellite loci. The spatial pattern of genetic variation was investigated by estimating the relationship between genetic distance and geographical, climatic and landscape resistances hypothesized to influence gene flow between populations. KEY RESULTS: We found high genetic diversity of M. micrantha in this region, as compared with the genetic diversity parameters of other invasive species. Spatial and non-spatial clustering algorithms identified the presence of multiple genetic clusters and admixture between populations. Most of the populations showed heterozygote deficiency, primarily due to inbreeding, and the founder populations showed evidence of a genetic bottleneck. Persistent gene flow throughout the invasive range caused low genetic differentiation among populations and provided beneficial genetic variation to the marginal populations in a heterogeneous environment. Environmental suitability was found to buffer the detrimental effects of inbreeding at the leading edge of range expansion. Both linear and non-linear regression models demonstrated a weak relationship between genetic distance and geographical distance, as well as bioclimatic variables and environmental resistance surfaces. CONCLUSIONS: These findings provide evidence that extensive gene flow and admixture between populations have influenced the current genetic pattern of M. micrantha in this region. High gene flow across the invaded landscape may facilitate adaptation, establishment and long-term persistence of the population, thereby indicating the range expansion ability of the species.

Characterization of the complete chloroplast genome of Camellia granthamiana (Theaceae), a Vulnerable species endemic to China.

Camellia granthamiana is a wild camellia resource endemic to China and is listed as a Vulnerable species globally. Here, we reported and characterized its complete chloroplast (cp) genome by using Illumina pair-end sequencing data. The total chloroplast genome size was 157,001 bp, including inverted repeats (IRs) of 26,042 bp, separated by a large single copy (LSC) and a small single copy (SSC) of 86,622 and 18,295 bp, respectively. A total of 131 genes, including 36 tRNA, 8 Rrna, and 87 protein-coding genes were identified. Phylogenetic analysis showed that C. granthamiana is sister to C. sinensis with 100% value support.