Search

Darwin proposed two alternate hypotheses on the invasion success of alien plant species based on their close or distant phylogenetic relationship with the natives. Here we tested these hypotheses along the invasion process at large spatio-temporal scale. Using two abundance-based phylogenetic metrics for the native and alien flora of China, our study showed that invasion success of alien plant species is influenced by the phylogenetic relationship with native and alien species of different invasion stages. Phylogenetic similarity with the native species helps the alien ones to introduce and naturalize, but phylogenetic dissimilarity with the natives facilitates invasion success. The co-occurrence of invasive and naturalized aliens also formed more clustered assemblages, showed specialized responses to environmental stress, and provided temporal stability to the phylogenetic measures. The native-alien phylogenetic relationship is dynamic across spatial, environmental, and taxonomic scales. Therefore, assessing Darwin’s naturalization conundrum at different gradients of community assembly process is important.

AimsPluchea indica is a mangrove-associate species, known for its medicinal properties in its native range and being invasive in part of its introduced range. This study aimed to assess geographic distribution of genetic variation of this species across its distribution range, identify the factors influencing its genetic structure and use this information to suggest conservation and management strategies in its native and introduced ranges, respectively.MethodsWe assessed the genetic diversity and population structure of 348 individuals from 31 populations across its native (Asia) and introduced (USA) ranges for 15 nuclear microsatellite loci. The spatial pattern of genetic variation was investigated at both large and regional spatial scales with the hypothesis that geographic distance and natural geographic barriers would influence the population structure with varying levels of differentiation across spatial scales.Important FindingsWe found relatively high genetic diversity at the population level and pronounced genetic differentiation in P. indica, as compared with the genetic diversity parameters of mangroves and mangrove associates in this region. Most of the populations showed heterozygote deficiency, primarily due to inbreeding and impediment of gene flow. Analysis of population structures at large spatial scale revealed the presence of two major clusters across the species’ natural range separating populations in China from those in Indonesia, Malaysia, Singapore, Thailand, Cambodia and Philippines, and that the USA population might have been introduced from the population cluster in China. Genetic differentiation between populations was also observed at the regional scale. A large number of populations showed evidence of genetic bottleneck, thereby emphasizing the risk of local extinction. Based on these findings, our study recommends in situ conservation strategies, such as to prioritize populations for conservation actions and to maintain genetic diversity.

We executed a pot experiment to examine the differences of absorption, chemical forms, subcellular distribution, and toxicity of Cd between two cultivars of Chinese flowering cabbage Brassica campestris [Lvbao701 (low-Cd cultivar) and Chicaixin No.4 (high-Cd cultivar)]. Compared to Chicaixin No.4, the presence of Lvbao701 enhanced the proportion of insoluble Cd forms in soil, Lvbao701 roots and leaves had higher proportion of Cd converted into insoluble phosphate precipitates and pectate-or protein-bound forms and lower proportion of inorganic Cd, which result in low accumulation and toxicity of Cd to Lvbao701 and cutworm Spodoptera litura fed on Lvbao701 leaves. Instead of total Cd, Cd transfer and toxicity in B. campestris-S. litura system depend on chemical Cd forms in soil and cabbages and subcellular Cd distributions in cabbages and insects, and the proportions of them were not the highest among all chemical forms and subcellular distributions of Cd. Although exchangeable Cd was major Cd chemical form in cabbage planted soil, Cd bound to iron and manganese oxides and to organic matter were significantly correlated with growth indices and photosynthesis parameters of cabbages. Despite major part of Cd was precipitated in cell wall of roots, Cd in organelle fraction was closely associated with the fitness of cabbages. Metal-rich granules, not cytosolic fraction (the major subcellular Cd distribution), affected the food utilization of S. litura. Therefore, cabbage cultivars significantly affected Cd transfer and toxicity in B. campestris-S. litura system, and the use of Lvbao701 in Cd polluted soil could reduce potential risks for Cd entering food chains.

Background and AimsMikania 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.MethodsWe 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 ResultsWe 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.ConclusionsThese 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.

Global climate change and decreases in available land are significant challenges that humans are currently facing. Alternative management approaches for sugarcane fields have great potential to help mitigate these problems in China. We hypothesized that soybean intercropping with reduced nitrogen input could increase crop productivity and reduce the carbon footprint (CF) of sugarcane fields in China. Therefore, a long-term field experiment from 2009 to 2017 in the Pearl River Delta of China was chosen to test this hypothesis. The results showed that the energy yields of sugarcane/soybean intercropping systems were 17.8%–39.4% higher than those of sugarcane monocropping systems. The energy yields of the same cropping systems using conventional and reduced N inputs (525 kg ha−1 and 300 kg ha−1) did not show a significant difference. Additionally, the CF values of the unit yield (CFY) for sugarcane/soybean intercropping were 3.2%–30.4% lower than those of the monocropping systems, showing the higher CF efficiency of the intercropping pattern, although the difference was not significant. The CF of the unit area (CFA) and the CFY of all the cropping patterns at the conventional N level were 19.5%–62.0% higher than that at the reduced N level, demonstrating that reducing the nitrogen input could significantly lower the CF of the sugarcane fields. In addition, the high N level cased negative effects in terms of increasing the crop productivity and reducing the CF of the soybean/sugarcane intercropping pattern. In conclusion, sugarcane/soybean intercropping with reduced N input improved crop productivity while lowering the CF of sugarcane fields in China. The sugarcane/soybean (1:2) intercropping with 300 kg N ha−1 system showed the best benefits in the Pearl River Delta of China. These advanced agricultural practices contributed to improved farmland use efficiency and clean production in an agricultural system.

Canavalia rosea, a perennial vine of the legume (Fabaceae) family, is commonly found in the tropical and subtropical coasts of the world. The long-distance dispersal ability of its sea-drifted seeds has aided the species to attain a pantropical distribution. While there has been some progress on its global phylogeography, the influence of evolutionary mechanisms on the genetic composition of C. rosea at a regional scale is still unknown. In this study, we used 13 nuclear microsatellite markers and 376 samples of C. rosea from 29 sampling sites to estimate the genetic diversity and assessed the influence of gene flow and demographic features on the population structure of the species in the Indo-West Pacific (IWP) region. We found high genetic diversity and moderate genetic differentiation of C. rosea in this region. Both spatial and non-spatial clustering algorithms revealed a subtle genetic structure created by the oceanic circulation pattern of the South China Sea (SCS), thereby differentiating the sampling sites of northern SCS from the rest and even creating a genetic break within the north of SCS. However, the Bayesian analysis of migration rate and direction revealed that propagules of C. rosea could move around the cryptic barriers of ocean currents and the land barrier of the Malay Peninsula, thereby weakening the genetic differentiation between these population clusters. Although a significant relationship between geographic distance and genetic differentiation was found, our findings suggested that a continuous distribution model of gene flow could have influenced the population structure of C. rosea in this region.

Premise of the Study Expressed sequence tag–simple sequence repeat (EST‐SSR) markers were developed for Pluchea indica, a traditional medicinal species widespread along the tropical coastlines of Asia and northern Australia. Methods and Results Based on transcriptome data for P. indica, a total of 40 primer pairs were initially designed and tested, of which 17 were successfully amplified and showed clear polymorphism. For these SSR loci, one to nine alleles per locus were identified. The levels of observed and expected heterozygosity ranged from 0 to 0.9 and 0 to 0.831, respectively. Furthermore, 16, 17, and 12 loci were successfully amplified in three congeneric species, P. eupatorioides, P. pteropoda, and P. sagittalis, respectively. Conclusions The SSR markers described here may be useful for further investigation of the population genetics of P. indica and related species.

Spartina alterniflora Losiel. is a highly invasive species found on the Chinese coast. To characterize the evolutionary mechanisms underlying the success of S. alterniflora in China, we examined the distribution and structure of genetic variation among three native populations at their source locations and five non-native populations in China, at both the chloroplast and nuclear microsatellite loci. Both cpDNA and microsatellite data revealed comparable genetic diversity and population differentiation between the native and introduced regions, which is consistent with the deliberate historical planting of heterogeneous founding groups in China. Bayesian clustering analysis showed that the best two clusters in the introduced region correspond to populations from the Atlantic coast and Gulf coast, respectively, instead of the three ecotypes proposed by a previous study. Investigating genetic composition of individuals suggested that most of the non-native plants might be of Atlantic origin, while some individuals in the Hong Kong population could be genetic admixtures of Atlantic and Gulf origin. This study indicated varied genetic components among populations in China, which imply different sources for the present Chinese populations.

Cultivation of genetically modified maize (Zea mays L.) expressing the Cry1Ab protein from Bacillus thuringiensis (Bt) has increased worldwide since Bt maize was first commercialised. However, the cultivation and return of Bt maize has been shown to affect nontarget symbiotic soil-borne microbes such as arbuscular mycorrhizal fungi (AMF). In this study, we compared the diversity and composition of the AMF communities between two Bt maize plants (5422Bt1 [event Bt 11] and 5422CBCL [event MON 810]) and their conventional (non-Bt) isoline (5422) after cultivation for five seasons and return of straws by using molecular approaches, including terminal restriction fragment length polymorphism and DNA sequencing. Our data revealed that the diversities of AMF communities did not consistently differ significantly in soils and roots of subsequently planted conventional maize (SCM 5422) grown with Bt maize straw at three sampling stages (seedling, large bell, and maturity stages). DNA sequencing showed that typical AMF communities included Glomus, Paraglomus, Diversispora, Acaulospora, and Rhizophagus, of which Glomus was the most abundant. Funneliformis was detected only in bulk and rhizospheric soils and in roots of maize at the seedling stage. Rhizophagus was detected only in rhizospheric soils and only at the maturity stage. No significant effects related to the presence of Bt maize straw (5422Bt1 or 5422CBCL) were found by general linear analysis. However, plant growth stage had a greater influence on AMF diversity than Bt traits. In conclusion, cultivation of non-Bt maize on soils previously cultivated with Bt maize for five seasons had minor effects on AMF communities.

Ceriops tagal is a long-lived, woody perennial mangrove species, which is expected to maintain high levels of genetic diversity. We used two kinds of molecular markers, including maternally inherited chloroplast intergenic spacers (total ∼2550 bp) and bi-parentally inherited nuclear genes (total ∼69,308 bp) to examine the genetic variation of C. tagal across East India Ocean (EIO), West Pacific Ocean (WPO) and North Australia (NA), representing the largest range ever investigated. For nuclear genes survey, we adopted deep sequencing technologies to sequence 90 nuclear loci from pooled DNA samples of 100 individuals from each of three populations of C. tagal . Our data showed an extremely low level of polymorphism both at the chloroplast regions (nucleotide diversity: π = 3.2 × 10 −4 ) and nuclear loci ( π = 3.0 × 10 −4 ) across the species range investigated. This species appeared to have passed through severe and prolonged demographic bottlenecks in the Pleistocene glaciation. However, a highly differentiated population structure among geographical regions was revealed by both molecular markers. Chlorotype analysis identified three major geographical groups in correspond to the EIO, WPO and NA. The high genetic identities within any local populations of C. tagal and shallow distinct genetic differences between geographical groups suggested recent historical isolation among the populations. Genetic information obtained from this study should help provide a framework for the development of conservation program for this species.

Polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) in combination with sequencing of amplified partial 18S ribosomal DNA was used to assess the effects of transgenic Bt corn 5422Bt1 (event Bt 11) and 5422CBCL (event MON810) on the community structure of a non-target microorganism, namely the arbuscular mycorrhizal fungi (AMF) Glomus in corn roots and rhizosphere soils, relative to their non-Bt isolines 5422 (conventional parent) and 5422wx (conventional hybrid). AMF colonization in roots of different corn genotypes was also assessed using microscopic visualization. No adverse effect was detected on the indigenous AMF colonization of the roots of Bt hybrids 5422Bt1 and 5422CBCL. Two-way indicator species analysis (TWINSPAN®) and detrended correspondence analysis (DCA) of the DGGE data from corn roots presented differences between Bt and non-Bt corn isolines (5422Bt1 vs. 5422wx, and 5422CBCL vs. 5422wx). However, differences were also recognized between the two non-Bt corn cultivars (5422 vs. 5422wx), and between the two Bt corn lines (5422Bt1 vs. 5422CBCL) in roots. Our results suggest that corn genotypes may have a greater influence on the AMF community structure of plant roots and rhizosphere soils than other factors, such as the age of the growing plants.

We investigated the effects of soil temperature (15 °C, 25 °C, 35 °C), water content (20%, 33%, 50%) and pH (4.5, 7.0, 9.0) on the degradation of Cry1Ab protein released from the straw of Bt corn varieties 34B24 and 1246 × 1482 both expressing Cry1Ab protein. Our results showed that Cry1Ab protein released from both 34B24 and 1246 × 1482 straw was degraded in a similar way in all treatments, which demonstrated a rapid decline in the early stage but a slow decline in the middle and late stages. In the late stage (180 days after the experiment commenced) 0.03%–1.51% and 0.02%–0.91% of initial Cry1Ab protein released from 34B24 and 1246 × 1482 straw was detected in soil. In addition, degradation dynamics of Cry1Ab protein under different environmental conditions was well described by the shift-log model. DT 50 of Cry1Ab protein released from 34B24 and 1246 × 1482 straw was 0.97–9.97 d and 0.75–10.89 d, respectively, and DT 90 was 4.66–162.45 d and 6.44–57.46 d, respectively. The results suggested that soil temperature had significant effects on the degradation of Cry1Ab protein, with a higher degradation rate at higher temperature, but soil water content and pH had no obvious effects on the degradation of Cry1Ab protein.

Premise of the study Expressed sequence tag-simple sequence repeat (EST-SSR) markers were developed for Pluchea indica, a traditional medicinal species widespread along the tropical coastlines of Asia and northern Australia. Methods and results Based on transcriptome data for P. indica, a total of 40 primer pairs were initially designed and tested, of which 17 were successfully amplified and showed clear polymorphism. For these SSR loci, one to nine alleles per locus were identified. The levels of observed and expected heterozygosity ranged from 0 to 0.9 and 0 to 0.831, respectively. Furthermore, 16, 17, and 12 loci were successfully amplified in three congeneric species, P. eupatorioides, P. pteropoda, and P. sagittalis, respectively. Conclusions The SSR markers described here may be useful for further investigation of the population genetics of P. indica and related species.

Polymerase chain reaction–denaturing gradient gel electrophoresis (PCR–DGGE) and sequences of the 16S and 18S rRNA genes were used to access the effects of actively growing Bacillus thuringiensis (Bt) corn Pioneer 34B24 and Nongda 1246*1482, and plant straw (leaves plus stalks) of Bt hybrid Pioneer 34B24 and Nongda 61 on soil bacterial and fungal communities. Two-way indicator species analysis (TWINSPAN®), and detrended correspondence analysis (DCA) of the DGGE data indicated that neither the actively growing Bt corn nor its straw had any constant apparent effect on the soil bacteria and fungi community structure. The age of the growing plants, or the timing of plant straw decomposition may have more effect on the microbial community than other factors, i.e., the presence of Cry protein, plant hybrid and variety.

Aegiceras corniculatum is a cryptoviviparous mangrove tree distributed in the Indo-West Pacific. The genetic structure of 13 populations of A. corniculatum from South China, Malay Peninsula, Sri Lanka, and North Australia, was assessed by amplified fragment length polymorphism (AFLP) markers. Our results showed a relatively high level of genetic variation at the species level (P = 92%, HE = 0.294 and Hs = 0.331 ± 0.001). The value of GST was 0.698, suggesting significant genetic differentiation among populations. At the population level, however, genetic diversity was low (P = 24%, HE = 0.086 and Hs = 0.127 ± 0.001). When populations were grouped according to geographic regions, i.e., South China, Malay Peninsula and Sri Lanka, it was inferred from analysis of molecular variance (AMOVA) that about half the total variation (49%) was accounted for differentiation between regions. A UPGMA dendrogram based on genetic distance also revealed five major clades corresponding to geographical regions within the distribution of A. corniculatum, although the precise relationships among the clades were not fully concordant with expected geographical delineations and need further study.

Ceriops is a viviparous mangrove with widespread species Ceriops decandra and C. tagal, and an endemic species C. australis. Genetic diversity of the three species was screened in 30 populations collected from 23 locations in the Indo West Pacific (IWP) using Inter-simple sequence repeats (ISSR) and sequences of partial nuclear gene (G3pdh) and chloroplast DNA (trnV-trnM). At the species level, the total gene diversity (Ht) revealed by ISSRs was 0.270, 0.118, and 0.089 in C. decandra, C. tagal, and C. australis, respectively. A total of six haplotypes of G3pdh and five haplotypes of trnV-trnM were recognized among the three species. Only C. decandra was detected containing more than one haplotype from each sequence data set (four G3pdh haplotypes and three trnV-trnM haplotypes). At the population level, genetic diversity of Ceriops was relatively low inferred from ISSRs (He = 0.028, 0.023, and 0.053 in C. decandra, C. tagal, and C. australis, respectively). No haplotype diversity within population was detected from any of the three species. Cluster analysis based on ISSRs identified three major geographical groups in correspond to the East Indian Ocean (EIO), South China Sea (SCS), and North Australia (NA) in both C. decandra and C. tagal. The cladogram from DNA sequences also detected the same three geographical groups in C. decandra. Analysis of molecular variance (AMOVA) revealed that most of the total variation was accounted for by differentiation between the three major geographical regions of both C. decandra and C. tagal. The significant genetic structure may result from the geological events in these regions during the recent Pleistocene glaciations. This study also provided insights into the phylogenetics of Ceriops.

Mangrove forests, with their ecological significance and economic benefits, are vital inter-tidal wetland ecosystems. Lumnitzera littorea (Combreataceae) is a non-viviparous mangrove distributed in tropical Asia and North Australia. Due to natural and human impacts, populations of this species have been isolated, fragmented, and highly disturbed. In China, L. littorea is an endangered species, restricted to small regions of Hainan Island. The genetic composition of five populations of this species from the Indo-West Pacific (South China, Malay Peninsula, Sri Lanka, North Australia) was assessed using inter simple sequence repeat (ISSR) makers. At the species level, expected mean heterozygosity (He) was 0.240 with 75.6% of loci polymorphic (P). However, genetic variation was much lower at the population level (P = 37.1%, He = 0.118). A high coefficient of gene differentiation (Gst = 0.515) and low level of gene flow (Nm = 0.470) indicated significant genetic differentiation among populations. AMOVA also indicated that more than half the total variation (58.4%) was partitioned among populations. The high degree of differentiation observed among populations emphasizes the need for appropriate conservation measures that incorporate additional populations into protected areas, and achieve the restoration of separate, degraded populations.

The genetic structure of 18 populations of Lumnitzera racemosa from the Indo-West Pacific, including South China, Malay Peninsula, Sri Lanka, and North Australia, was assessed by inter simple sequence repeat (ISSR) markers. Our results showed a relatively high level of genetic variation at the species level ( P = 87.04%, H e = 0.260). The value of G st was 0.642, suggesting significant genetic differentiation among populations. At the population level, however, genetic diversity was low ( P = 32.17%, H e = 0.097). When populations were grouped according to geographic regions, i.e., South China Sea, the East Indian Ocean, and North Australia, it was inferred from AMOVA that more than half the total variation (55.37%) was accounted for by differentiation between regions. A UPGMA dendrogram based on genetic distance also revealed a deep split between populations from these regions, indicating that Malay Peninsula and the Indonesia archipelago may play an important part on the genetic differentiation in L. racemosa . The high degree of population differentiation between regions and low genetic variation within populations recorded here highlights the need for appropriate conservation measures for this species, both in terms of incorporating further populations into protected areas, and the restoration strategies for separate regions.

Comprehensive information of mangrove genetic resources is requisite for developing strategies for their effective conservation and sustainable use. Genetic diversity within and among populations of a widespread viviparous mangrove Ceriops decandra was determined using inter-simple sequence repeat (ISSR). Ten natural populations were collected from Malay Peninsula and North Australia. At the species level, high genetic variation was detected (P = 72%, HE = 0.253, and I = 0.379). The estimate of GST was 0.882, indicating a high level of genetic differentiation among populations. When populations were grouped according to geographic regions, i.e., East Malaya, West Malaya, Southmost Malaya, and North Australia, AMOVA suggested that most of the total variation (87%) was accounted for by differentiation between regions, with only 4% accounting for variation among populations within regions, and a further 9% partitioned among individuals within a population. A UPGMA dendrogram based on genetic distance revealed a deep split between populations from the eastern Indian Ocean and all others from the western Pacific Ocean, which may result from the historical lowering of sea level at these regions during the recent Pleistocene glaciations. An understanding of the genetic structure of C. decandra provides insight for the conservation and management of this species.

Premise of the study: Chloroplast and mitochondrial microsatellites were identified to study the population genetics of Millettia pinnata (Fabaceae). Methods and Results: Based on publicly available plastid genome sequence data of M. pinnata, 42 primer pairs were developed, of which 17 displayed polymorphisms across 89 individuals from four populations. For chloroplast loci, two to six alleles were recovered and the unbiased haploid diversity per locus ranged from 0.391 to 0.857. For mitochondrial loci, two to four alleles were recovered and the unbiased haploid diversity ranged from 0.264 to 0.740. Sixteen of the 17 screened markers could be successfully amplified in the related species M. pulchra. Conclusions: The 17 microsatellite markers developed here exhibited variation in M. pinnata and 16 presented transferability in the related species M. pulchra, suggesting that these markers will be valuable for genetic studies across M. pinnata and its related species.

Premise of the study: Microsatellite markers were developed for Carallia brachiata to assess the genetic diversity and structure of this terrestrial species of the Rhizophoraceae. Methods and Results: Based on transcriptome data for C. brachiata, 40 primer pairs were initially designed and tested, of which 18 were successfully amplified and 11 were polymorphic. For these microsatellites, one to three alleles per locus were identified. The observed and expected heterozygosities ranged from 0 to 0.727 and 0 to 0.520, respectively. In addition, all primers were successfully amplified in two congeners: C. pectinifolia and C. garciniifolia. Conclusions: The microsatellite markers described here will be useful in population genetic studies of C. brachiata and related species, suggesting that developing microsatellite markers from next-generation sequencing data can be efficient for genetic studies across this genus.

nested within the Sonneratiaceae. The Sonneratiaceae occurred within the Lythraceae with high bootstrap value support (96%). The two traditional genera constituting Sonneratiaceae were in different well-supported clades. Duabanga (Sonneratiaceae) is sister to the clade of Lagerstroemia (Lythraceae) (82%). The mangrove genus Sonneratia (100%) formed the other monophyletic group. It was located terminally within the Lythraceae clade and comprised two clades: one consisting of S. apetala, S. alba, S. ovata, and S. hainanensis; the other including S. caseolaris and S. paracaseolaris. The results indicated that species previously placed in two different sections (Sect. Sonneratia and Sect. Pseudosonneratia) of Sonneratia occurred within the same clade, and the taxonomic classification was not supported by the molecular analysis of the ITS region sequences. Based on the phylogenetic analyses of the ITS regions, the Sonneratiaceae were shown to be nested within the family Lythraceae. Therefore, the sequence data presented here do not support the recognition of the Sonneratiaceae as a distinct family, but instead support the inclusion of Sonneratiaceae in the Lythraceae proposed by other authors.

The molecular phylogenetic trees of 10 species representing 6 genera of the family Rhizophoraceae have been constructed using the sequences of chloroplast genesmatK andrbcL as well as the ITS regions of nuclear ribosomal DNA. Relative-rate tests between lineages in these phylogenetic trees have been performed. On the basis of the results of the relative-rate tests and related molecular evolutionary rate data, the divergence times between the lineages are estimated as follows: (i) the first divergence time in these genera is 132.25 million years ago (mya); (ii) the average divergence time between two tribes, i.e. inland Legnotideae (exceptCarallia brachiata) and mangrove Rhizophoreae, is 64.13 mya; and (iii) the average divergence time between two inland species,C. garciniaefolia andC. pectinifolia, is 19.92 mya.

Premise of the study: Microsatellite markers were identified and characterized to study the genetic diversity and structure of Barringtonia racemosa (Lecythidaceae). Methods and Results: Based on the transcriptome data of B. racemosa, 30 primer pairs were initially designed and tested, of which 15 were successfully amplified and displayed clear polymorphisms across the 43 individuals from three distant populations tested in the study. The results showed that the number of alleles per locus ranged from two to seven and the expected heterozygosity and observed heterozygosity per locus varied from 0 to 0.772 and from 0 to 0.933, respectively. Conclusions: The expressed sequence tag–simple sequence repeat (EST-SSR) markers described here will be useful for studying genetic diversity and structure of B. racemosa. Furthermore, all loci were successfully cross-amplified in B. asiatica and B. acutangula and will be of great value for genetic studies across this genus.

The most remarkable morphological specializations of mangroves are vivipary, salt secretion, and aerial roots. There has been a long debate on whether the complex traits vivipary and secreters have a single origin, the answer to which has profound implications for the mechanism of evolution in mangroves. We took a large and representative sample across mangroves and sequenced the 18S rRNA, rbcL, and matR genes. Together with the outgroups, our data yielded a high resolution phylogeny which allowed us to gain much needed insight into the distributions of the two characters and address their evolutionary origins. For each character, its ancestral state in the phylogeny was estimated by the maximum likelihood method. Overall evidence is in favor of a multiple origin for both vivipary and salt secretion in mangroves.

Phylogenetic relationships of the subfamily Combretoideae (Combretaceae) were studied based on DNA sequences of nuclear ribosomal internal transcribed spacer (ITS) regions, the plastid rbcL gene and the intergenic spacer between the psaA and ycf3 genes (PY-IGS), including 16 species of eight genera within two traditional tribes of Combretoideae, and two species of the subfamily Strephonematoideae of Combretaceae as outgroups. Phylogenetic trees based on the three data sets (ITS, rbcL, and PY-IGS) were generated by using maximum parsimony (MP) and maximum likelihood (ML) analyses. Partition-homogeneity tests indicated that the three data sets and the combined data set are homogeneous. In the combined phylogenetic trees, all ingroup taxa are divided into two main clades, which correspond to the two tribes Laguncularieae and Combreteae. In the Laguncularieae clade, two mangrove genera, Lumnitzera and Laguncularia, are shown to be sister taxa. In the tribe Combreteae, two major clades can be classified: one includes three genera Quisqualis, Combretum and Calycopteris, within which the monophyly of the tribe Combreteae sensu Engler and Diels including Quisqualis and Combretum is strongly supported, and this monophyly is then sister to the monotypic genus Calycopteris; another major clade includes three genera Anogeissus, Terminalia and Conocarpus. There is no support for the monophyly of Terminalia as it forms a polytomy with Anogeissus. This clade is sister to Conocarpus.

Interferon-gamma (IFN-γ) inhibits intracellular replication of Francisella tularensis in human monocyte-derived macrophages (HMDM) and in mice, but the mechanisms of this protective effect are poorly characterized. We used genome-wide RNA interference (RNAi) screening in the human macrophage cell line THP-1 to identify genes that mediate the beneficial effects of IFN-γ on F. tularensis infection. A primary screen identified ∼200 replicated candidate genes. These were prioritized according to mRNA expression in IFN-γ-primed and F. tularensis-challenged macrophages. A panel of 20 top hits was further assessed by re-testing using individual shRNAs or siRNAs in THP-1 cells, HMDMs and primary human lung macrophages. Six of eight validated genes tested were also found to confer resistance to Listeria monocytogenes infection, suggesting a broadly shared host gene program for intracellular pathogens. The F. tularensis-validated hits included 'druggable' targets such as TNFRSF9, which encodes CD137. Treating HMDM with a blocking antibody to CD137 confirmed a beneficial role of CD137 in macrophage clearance of F. tularensis. These studies reveal a number of important mediators of IFN-γ activated host defense against intracellular pathogens, and implicate CD137 as a potential therapeutic target and regulator of macrophage interactions with Francisella tularensis.