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

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

IntroductionPhylogenetic 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.MethodsWe 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.ResultsWe 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.DiscussionOverall, 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

Economic costs of biological invasions in Asia

Invasive species have caused severe impacts on biodiversity and human society. Although the estimation of environmental impacts caused by invasive species has increased in recent years, economic losses associated with biological invasions are only sporadically estimated in space and time. In this study, we synthesized the losses incurred by invasions in Asia, based on the most comprehensive database of economic costs of invasive species worldwide, including 560 cost records for 88 invasive species in 22 countries. We also assessed the differences in economic costs across taxonomic groups, geographical regions and impacted sectors, and further identified the major gaps of current knowledge in Asia. Reported economic costs of biological invasions were estimated between 1965 and 2017, and reached a total of US$ 432.6 billion (2017 value), with dramatic increases in 2000–2002 and in 2004. The highest costs were recorded for terrestrial ectotherms, for species estimated in South Asia, and for species estimated at the country level, and were related to more than one impacted sector. Two taxonomic groups with the highest reported costs were insects and mammals, and two countries with the highest costs were India and China. Non-English data covered all of 12 taxonomic groups, whereas English data only covered six groups, highlighting the importance of considering data from non-English sources to have a more comprehensive estimation of economic costs associated with biological invasions. However, we found that the estimation of economic costs was lacking for most Asian countries and for more than 96% of introduced species in Asia. Further, the estimation is heavily biased towards insects and mammals and is very limited concerning expenditures on invasion management. To optimize the allocation of limited resources, there is an important need to better and more widely study the economic costs of invasive alien species. In this way, improved cost reporting and more collaborations between scientists and stakeholders are needed across Asia

Role of intraspecific trait plasticity in Mikania micrantha Kunth growth and impact of its abundance on community composition

Intraspecific trait variability, which plays an important role in community assembly, was studied in an invasive plant Mikania micrantha along with its impact on community composition. The abundance of M. micrantha and community composition were recorded in a quadrat-based study conducted on a spatial (littoral, terrestrial, and an intermediate habitat) and temporal (summer, monsoon, and winter) scale. Soil parameters were analyzed and some fitness-related traits of M. micrantha were estimated. Season and habitat had significant effects on M. micrantha abundance. Seasonal plasticity was evident in leaf-level traits. High laminar nitrogen and leaf dry matter content during the monsoons and a larger leaf area with high chlorophyll content during summer and winter months were responsible for maintenance of its yearlong growth. Multivariate regression analysis revealed that, after adjusting for season and habitat, none of the traits exhibited significant effect on M. micrantha abundance. Abundance of M. micrantha appeared to be the only factor responsible for decline in associated species richness. Continuous monitoring of the established population and early detection of new infestations of M. micrantha are recommended to keep a check on excessive growths to prevent it from becoming problematic in subtropical regions of the world

Genetic and epigenetic regulation of phenotypic variation in invasive plants – linking research trends towards a unified framework

Volume: 49Start Page: 77End Page: 10

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

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

Characterization of the complete chloroplast genome of Camellia renshanxiangiae (Theaceae)

Camellia renshanxiangiae is a vulnerable species distributed in China with unique hairy anthers and faint scent. Here, we report the characterization of its complete chloroplast (cp) genome using Illumina pair-end sequencing data. The total chloroplast genome size was 156,665 bp, including two inverted repeats (IRs) of 26,071 bp each, separated by a large single copy (LSC) and a small single copy (SSC) of 86,277 bp and 18,246 bp, respectively. A total of 131 genes, including 36 tRNA, 8 rRNA, and 87 protein-coding genes, were identified. Phylogenetic analysis showed that C. renshanxiangiae clustered with Camelia species (C. sinensis, C. crapnelliana)

Biological invasions in Singapore and Southeast Asia: data gaps fail to mask potentially massive economic costs

The impacts of invasive alien species are well-known and are categorised as a leading contributor to biodiversity loss globally. However, relatively little is known about the monetary costs incurred from invasions on national economies, hampering management responses. In this study, we used published data to describe the economic cost of invasions in Southeast Asia, with a focus on Singapore – a biodiversity-rich, tropical island city state with small size, high human density and high trade volume, three factors likely to increase invasions. In this country, as well as in others in Southeast Asia, cost data were scarce, with recorded costs available for only a small fraction of the species known to be invasive. Yet, the overall available economic costs to Singapore were estimated to be ~ US$1.72 billion in total since 1975 (after accounting for inflation), which is approximately one tenth of the total cost recorded in all of Southeast Asia (US$ 16.9 billion). These costs, in Singapore and Southeast Asia, were mostly linked to insects in the family Culicidae (principally Aedes spp.) and associated with damage, resource loss, healthcare and control-related spending. Projections for 11 additional species known to be invasive in Singapore, but with recorded costs only from abroad, amounted to an additional US$ 893.13 million, showing the potential huge gap between recorded and actual costs (cost records remain missing for over 90% of invasive species). No costs within the database for Singapore – or for other Southeast Asian countries – were exclusively associated with proactive management, highlighting that a shortage of reporting on the costs of invasions is mirrored by a lack of investment in management. Moreover, invasion cost entries in Singapore were under-reported relative to import levels, but total costs exceeded expectations, based on land area and population size, and to a greater extent than in other Southeast Asian countries. Therefore, the evaluation and reporting of economic costs of invasions need to be improved in this region to provide efficient data-based support for mitigation and management of their impacts