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Malika L Ainouche - One of the best experts on this subject based on the ideXlab platform.
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Supporting Spartina: Interdisciplinary perspective shows Spartina as a distinct solid genus
Ecology, 2019Co-Authors: Alejandro Bortolus, Malika L Ainouche, Debra R Ayres, Paul Adam, Janine B. Adams, Mark D. Bertness, Tjeerd J. Bouma, John F. Bruno, Isabel Caçador, James T. CarltonAbstract:In 2014 a DNA-based phylogenetic study confirming the paraphyly of the grass subtribe Sporobolinae proposed the creation of a large monophyletic genus Sporobolus, including (among others) species previously included in the genera Spartina, Calamovilfa, and Sporobolus. Spartina species have contributed substantially (and continue contributing) to our knowledge in multiple disciplines, including ecology, evolutionary biology, molecular biology, biogeography, experimental ecology, environmental management, restoration ecology, history, economics, and sociology. There is no rationale so compelling to subsume the name Spartina as a subgenus that could rival the striking, global iconic history and use of the name Spartina for over 200 years. We do not agree with the arguments underlying the proposal to change Spartina to Sporobolus. We understand the importance of taxonomy and of formalized nomenclature and hope that by opening this debate we will encourage positive feedback that will strengthen taxonomic decisions with an interdisciplinary perspective. We consider the strongly distinct, monophyletic clade Spartina should simply and efficiently be treated as the genus Spartina.
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Transcriptome de novo assembly from next-generation sequencing and comparative analyses in the hexaploid salt marsh species Spartina maritima and Spartina alterniflora (Poaceae)
Heredity, 2012Co-Authors: J. Ferreira De Carvalho, Armel Salmon, Julie Poulain, C.a. Da Silva, Patrick Wincker, Sophie Michon-coudouel, Alexandra Dheilly, Delphine Naquin, Julien Boutte, Malika L AinoucheAbstract:Spartina species have a critical ecological role in salt marshes and represent an excellent system to investigate recurrent polyploid speciation. Using the 454 GS-FLX pyrosequencer, we assembled and annotated the first reference transcriptome (from roots and leaves) for two related hexaploid Spartina species that hybridize in Western Europe, the East American invasive Spartina alterniflora and the Euro-African S. maritima. The de novo read assembly generated 38 478 consensus sequences and 99% found an annotation using Poaceae databases, representing a total of 16 753 non-redundant genes. Spartina expressed sequence tags were mapped onto the Sorghum bicolor genome, where they were distributed among the subtelomeric arms of the 10 S. bicolor chromosomes, with high gene density correlation. Normalization of the complementary DNA library improved the number of annotated genes. Ecologically relevant genes were identified among GO biological function categories in salt and heavy metal stress response, C4 photosynthesis and in lignin and cellulose metabolism. Expression of some of these genes had been found to be altered by hybridization and genome duplication in a previous microarray-based study in Spartina. As these species are hexaploid, up to three duplicated homoeologs may be expected per locus. When analyzing sequence polymorphism at four different loci in S. maritima and S. alterniflora, we found up to four haplotypes per locus, suggesting the presence of two expressed homoeologous sequences with one or two allelic variants each. This reference transcriptome will allow analysis of specific Spartina genes of ecological or evolutionary interest, estimation of homoeologous gene expression variation using RNA-seq and further gene expression evolution analyses in natural populations.
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Transcriptome divergence between the hexaploid salt‐marsh sister species Spartina maritima and Spartina alterniflora (Poaceae)
Molecular Ecology, 2010Co-Authors: Houda Chelaifa, F. Mahé, Malika L AinoucheAbstract:Invasive species are ideal model systems to investigate the evolutionary processes associated with their ecological success by comparison with closely related species. In this article, we explore transcriptome evolution following divergence between two closely related salt-marsh species, the invasive Spartina alterniflora (native to the EastAmerican Atlantic coast, introduced in several continents) and the declining Spartina maritima (native to the Euro-African Atlantic coast). We have explored the utility of cross-species hybridization microarrays using rice (Oryza sativa) oligo-microarrays to compare leaf expression patterns between these species. Coding sequence comparisons from 10 nuclear genes (2256 bp) revealed that nucleotide divergence between Spartina and Oryza range from 8% to 14%. More than 70% of the 60-mer oligonucleotide sequences spotted on the rice microarray exhibited stable and repeatable patterns when hybridized against Spartina RNA. In total, 9353 (44.5%) genes on the array hybridized with both species S. maritima and S. alterniflora. Among these genes, 1247 genes were found to be differentially expressed between the two Spartina species, most of them (957) being up-regulated in S. alterniflora. In particular, developmental and cellular growth genes (gene ontology, biological process) were highly up-regulated in S. alterniflora and down-regulated in S. maritima, whereas genes involved in stress response were upregulated in S. maritima. Our findings indicate the suitability of cross-species microarray hybridization between Spartina and O. sativa and reveal the extent of leaf transcriptome evolution that took place during the divergence between S. alterniflora and S. maritima. Expression patterns are consistent with the morphological differentiation and differential expansion of the two species.
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hybridization polyploidy and invasion lessons from Spartina poaceae
Biological Invasions, 2009Co-Authors: Malika L Ainouche, Armel Salmon, P M Fortune, Christian Parisod, Marieangele Grandbastien, K Fukunaga, M Ricou, Marietherese MissetAbstract:In this paper, we examine how the Spartina system has helped our understanding of the genomic aspects of allopolyploid speciation in the context of biological invasion. More specifically the respective roles of hybridization and genome duplication in the success of newly formed allopolyploid species are explored. Hybridization appears to have triggered genetic and epigenetic changes in the two recently formed European homoploid hybrids S. × towsendii and S. × neyrautii. Deviation from parental structural additivity is observed in both hybrids, with different patterns when considering transposable element insertions or AFLP and methylation alteration. No important changes are observed in the invasive allopolyploid Spartina anglica that inherited the identical genome to S. × townsendii. The repeated rRNA genes are not homogenized in the allopolyploid, and both parental repeats are expressed in the populations examined. Transcriptomic changes suggest possible gene silencing in both hybrids and allopolyploid. In the long-term of evolutionary time, older hexaploid Spartina species (Spartina alterniflora, Spartina maritima and Spartina foliosa) appear to have selectively retained differential homeologous copies of nuclear genes. Waxy gene genealogies suggest a hybrid (allopolyploid) origin of this hexaploid lineage of Spartina. Finally, nuclear and chloroplast DNA data indicate a reticulate origin (alloheptaploid) of the invasive Spartina densiflora. All together these studies stress hybridization as a primary stimulus in the invasive success of polyploid Spartina species.
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evolutionary dynamics of waxy and the origin of hexaploid Spartina species poaceae
Molecular Phylogenetics and Evolution, 2007Co-Authors: Philippe Fortune, Jonathan F Wendel, Abdelkader Ainouche, Kristina A Schierenbeck, Julie Jacquemin, Malika L AinoucheAbstract:We investigated the evolutionary dynamics of duplicated copies of the granule-bound starch synthase I gene (GBSSI or Waxy) within polyploid Spartina species. Molecular cloning, sequencing, and phylogenetic analyses revealed incongruences between the expected species phylogeny and the inferred gene trees. Some genes within species were more divergent than expected from ploidy level alone, suggesting the existence of paralogous sets of Waxy loci in Spartina. Phylogenetic analyses indicate that this paralogy originated from a duplication that occurred prior to the divergence of Spartina from other Chloridoideae. Gene tree topologies revealed three divergent homoeologous sequences in the hexaploid S. alterniXora that are consistent with the proposal of an allopolyploid origin of the hexaploid clade. Waxy sequences diVer in insertion–deletion events in introns, which may be used to diagnose gene copies. Both paralogous and homoeologous coding regions appear to evolving under selective constraints.
Bo Li - One of the best experts on this subject based on the ideXlab platform.
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potential impacts of invasive Spartina alterniflora on spring bird communities at chongming dongtan a chinese wetland of international importance
Estuarine Coastal and Shelf Science, 2009Co-Authors: Chi Yeung Choi, Jiakuan Chen, Bo LiAbstract:Invasive smooth cordgrass (Spartina alterniflora, hereafter Spartina) has been expanding rapidly in the estuarine wetlands at Chongming Dongtan (East China) at the expense of native sea-bulrush (Scirpus mariqueter, hereafter Scirpus) and common reed (Phragmites australis, hereafter Phragmites). To examine the potential impacts of the Spartina invasion on bird diversity, we compared the abundance and species richness of birds in habitats created by Spartina, Phragmites, Spartina mixed with Phragmites, Scirpus, and the bare intertidal zone at Chongming Dongtan in spring 2008. Most birds were recorded in the native habitats, with songbirds and breeding birds being most abundant in the Phragmites habitats, and waterbirds and migrants being most abundant in the Scirpus habitats and bare intertidal zone. Both species number and population densities of birds were lower in the exotic Spartina habitats than in the other four habitats. Although some songbirds and breeding birds used the Spartina-invaded habitats, and even preferred Spartina-invaded habitats to Scirpus habitats and bare intertidal zone, their densities were lower in the Spartina-invaded habitats than in the native Phragmites habitats. This might have resulted from the dense Spartina stands restricting bird movement and providing insufficient useable food for most birds. We conclude that the spread of exotic Spartina has negative impacts on local bird communities. Because Chongming Dongtan is an important stopover site for energy replenishment of shorebirds in the East Asian-Australasian Flyway, urgent measures are needed to control further spread of Spartina and to restore the native habitats for birds.
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Effects of saltmarsh invasion by Spartina alterniflora on arthropod community structure and diets
Biological Invasions, 2008Co-Authors: Yu-tong Wu, Jiakuan Chen, Cheng-huan Wang, Xiao-dong Zhang, Bin Zhao, Lifen Jiang, Bo LiAbstract:Invasive plants strongly affect physical and biotic environments of native ecosystems. Insects and other arthropods as one of the major components of many ecosystems are very sensitive to subtle changes in abiotic and biotic environments. We examined the effects of exotic Spartina alterniflora invasion on community structure and diets of arthropods in a saltmarsh previously dominated by native Phragmites australis in Yangtze River estuary through net sweeping and plant harvesting methods and stable isotope analysis. Our results showed that diversity indices were not significantly different between exotic and native plant communities, but the total abundance of insects estimated through plant harvesting method was found to be lower in Spartina monoculture than that in Phragmites monoculture. Community structure of insects in Spartina monoculture was dissimilar to that in Phragmites monoculture and Phragmites–Spartina mixture. Moreover, stable carbon isotope patterns of arthropods were significantly different between Phragmites and Spartina monocultures. Although some native arthropods (perhaps generalists) shifted their diets, many native taxa did prefer Phragmites to Spartina even in Spartina monoculture. Spartina invasions resulted in reduced abundances of some arthropds, and increased dominance of others feeding preferably on Spartina. This study provides evidence that invasive plants can change the community structure and diets of native arthropods, which will eventually alter the arthropod food web, and affect the integrity and functioning of native ecosystems within a nature reserve that has been set aside for conserving the native biodiversity and maintaining the ecosystem integrity. In this sense, Spartina invasions in the Yangtze River estuary need to be managed appropriately.
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litter pool sizes decomposition and nitrogen dynamics in Spartina alterniflora invaded and native coastal marshlands of the yangtze estuary
Oecologia, 2008Co-Authors: Jiakuan Chen, Chengzhang Liao, Changming Fang, Bo LiAbstract:Past studies have focused primarily on the effects of invasive plants on litter decomposition at soil surfaces. In natural ecosystems, however, considerable amounts of litter may be at aerial and belowground positions. This study was designed to examine the effects of Spartina alterniflora invasion on the pool sizes and decomposition of aerial, surficial, and belowground litter in coastal marsh- lands, the Yangtze Estuary, which were originally occupied by two native species, Scirpus mariqueter and Phragmites australis. We collected aerial and surficial litter of the three species once a month and belowground litter once every 2 months. We used the litterbag method to quantify litter decomposition at the aerial, surficial and belowground positions for the three species. Yearly averaged litter mass in the Spartina stands was 1.99 kg m -2 ; this was 250 and 22.8% higher than that in the Scirpus (0.57 kg m -2 ) and Phragmites (1.62 kg m -2 ) stands, respectively. The litter in the Spartina stands was primarily distributed in the air (45%) and belowground (48%), while Scirpus and Phragmites litter was mainly allocated to belowground positions (85 and 59%, respectively). The averaged decomposition rates of aerial, surficial, and belowground litter were 0.82, 1.83, and 1.27 year -1 for Spartina, respectively; these were 52, 62 and 69% of those for Scirpus litter at corresponding positions and 158, 144 and 78% of those for Phragmites litter, respec- tively. The differences in decomposition rates between Spartina and the two native species were largely due to differences in litter quality among the three species, partic- ularly for the belowground litter. The absolute amount of nitrogen increased during the decomposition of Spartina stem, sheath and root litter, while the amount of nitrogen in Scirpus and Phragmites litter declined during decomposition for all tissue types. Our results suggest that Spartina invasion altered the carbon and nitrogen cycling in the coastal marshlands of China.
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invasion of Spartina alterniflora enhanced ecosystem carbon and nitrogen stocks in the yangtze estuary china
Ecosystems, 2007Co-Authors: Chengzhang Liao, Jiakuan Chen, Lifen Jiang, Xuhui Zhou, Xiaowen Wu, Changming Fang, Bo LiAbstract:Whether plant invasion increases ecosystem carbon (C) stocks is controversial largely due to the lack of knowledge about differences in ecophysiological properties between invasive and native species. We conducted a field experiment in which we measured ecophysiological properties to explore the response of the ecosystem C stocks to the invasion of Spartina alterniflora (Spartina) in wetlands dominated by native Scirpus mariqueter (Scirpus) and Phragmites australis (Phragmites) in the Yangtze Estuary, China. We measured growing season length, leaf area index (LAI), net photosynthetic rate (Pn), root biomass, net primary production (NPP), litter quality and litter decomposition, plant and soil C and nitrogen (N) stocks in ecosystems dominated by the three species. Our results showed that Spartina had a longer growing season, higher LAI, higher Pn, and greater root biomass than Scirpus and Phragmites. Net primary production (NPP) was 2.16 kg C m−2 y−1 in Spartina ecosystems, which was, on average, 1.44 and 0.47 kg C m−2 y−1 greater than that in Scirpus and Phragmites ecosystems, respectively. The litter decomposition rate, particularly the belowground decomposition rate, was lower for Spartina than Scirpus and Phragmites due to the lower litter quality of Spartina. The ecosystem C stock (20.94 kg m−2) for Spartina was greater than that for Scirpus (17.07 kg m−2), Phragmites (19.51 kg m−2) and the mudflats (15.12 kg m−2). Additionally, Spartina ecosystems had a significantly greater N stock (698.8 g m−2) than Scirpus (597.1 g m−2), Phragmites ecosystems (578.2 g m−2) and the mudflats (375.1 g m−2). Our results suggest that Spartina invasion altered ecophysiological processes, resulted in changes in NPP and litter decomposition, and ultimately led to enhanced ecosystem C and N stocks in the invaded ecosystems in comparison to the ecosystems with native species.
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short term c4 plant Spartina alterniflora invasions change the soil carbon in c3 plant dominated tidal wetlands on a growing estuarine island
Soil Biology & Biochemistry, 2006Co-Authors: Jiakuan Chen, Xiaoli Cheng, Jiquan Chen, Bo LiAbstract:Spartina alterniflora is an invasive C4 perennial grass, native to North America, and has spread rapidly along the east coast of China since its introduction in 1979. Since its intentional introduction to the Jiuduansha Island in the Yangtze River estuary, Spartina alterniflora community has become one of the dominant vegetation types. We investigated the soil carbon in the Spartina alterniflora community and compared it with that of the native C3 Scirpus mariqueter community by measuring total soil carbon (TC), soil organic carbon (SOC), total soil nitrogen (TN), and the stable carbon isotope composition (d 13 C) of various fractions. TC and SOC were significantly higher in Spartina alterniflora in the top 60 cm of soil. However, there was no significant difference in soil inorganic carbon (IC) between the two communities. Stable carbon isotopic analysis suggests that the fraction of SOC pool contributed by Spartina alterniflora varied from 0.90% to 10.64% at a soil depth of 0–100 cm with a greater percentage between 20 and 40 cm deep soils. The d 13 C decreased with increasing soil depth in both communities, but the difference in d 13 C among layers of the top 60 cm soil was significant (po0:05), while that for the deeper soil layers (460 cm) was not detected statistically. The changes in d 13 C with depth appeared to be associated with the small contribution of residues from Spartina alterniflora at greater soil depth that was directly related to the vertical root distribution of the species. r 2006 Elsevier Ltd. All rights reserved.
Donald R Strong - One of the best experts on this subject based on the ideXlab platform.
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ecological and evolutionary misadventures of Spartina
Annual Review of Ecology Evolution and Systematics, 2013Co-Authors: Donald R Strong, Debra R AyresAbstract:Spartina species of the mid-low intertidal areas are powerful ecological engineers that are highly valued where they are native. Elsewhere, they overgrow native salt marsh and open intertidal mudflats, diminish biota, increase costs of managing wildlife, and interfere with human uses of estuaries. Huge efforts have been mounted to kill some populations of invading Spartina. All large Spartina invasions are by S. densiflora (2n = 7x = 70) or S. alterniflora (2n = 6x = 62) or hybrids between the hexaploid species (2n = 6x). Hybridization is a recurrent theme in Spartina; the allododecaploid S. anglica (2n = 12x = 120) and the hybrid swarm in San Francisco Bay arose through the introductions of S. alterniflora into the range of native Spartina species. The ancient hybrid S. densiflora also hybridized with native Spartina species. Hybridization promotes the evolution of highly invasive populations and hampers control efforts. Whether Spartina, native and not, would protect the shore as sea levels rise depends...
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spread of exotic cordgrasses and hybrids Spartina sp in the tidal marshes of san francisco bay california usa
Biological Invasions, 2004Co-Authors: Debra R Ayres, Debra L Smith, Katy Zaremba, Shannon Klohr, Donald R StrongAbstract:Four species of exotic cordgrass (Spartina sp.) occur in the San Francisco estuary in addition to the California native Spartina foliosa. Our goal was to map the location and extent of all non-native Spartina in the estuary. Hybrids of S. alterniflora and S. foliosa are by far the most numerous exotic and are spreading rapidly. Radiating from sites of deliberate introduction, S. alterniflora and hybrids now cover ca. 190 ha, mainly in the South and Central Bay. Estimates of rate of aerial increase range from a constant value to an accelerating rate of increase. This could be due to the proliferation of hybrid clones capable of rapid expansion and having superior seed set and siring abilities. The total coverage of 195 ha by hybrids and other exotic cordgrass species is slightly less than 1% of the Bay's tidal mudflats and marshes. Spartina anglica has not spread beyond its original 1970s introduction site. Spartina densiflora has spread to cover over 5 ha at 3 sites in the Central Bay. Spartina patens has expanded from 2 plants in 1970 to 42 plants at one site in Suisun Bay. Spartina seed floats on the tide, giving it the potential to export this invasion throughout the San Francisco estuary, and to estuaries outside of the Golden Gate. We found isolated plants of S. alterniflora and S. densiflora in outer coast estuaries north of the Bay suggesting the likelihood for the San Francisco Bay populations to found others on the Pacific coast.
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Characterization of microsatellite loci in Spartina species (Poaceae)
Molecular Ecology Notes, 2003Co-Authors: Michael J. Blum, Debra R Ayres, Christina M. Sloop, Donald R StrongAbstract:The cordgrasses in the genus Spartina have become model organisms for studying biological invasions from both ecological and genetic perspectives. Here we characterize 11 disomic loci in Spartina alterniflora that show promise for population studies and for studying hybridization events between S. alterniflora and S. foliosa . Comparisons among invasive and native S. alterniflora populations showed that levels of allelic variation are lower in invasive populations. In addition, nearly all loci that amplified in S. foliosa populations and in a swarm of S. alterniflora × foliosa hybrids were polymorphic. We also found that several loci amplified successfully in other Spartina species.
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status prediction and prevention of introduced cordgrass Spartina spp invasions in pacific estuaries usa
Biological Conservation, 1996Co-Authors: Curtis C Daehler, Donald R StrongAbstract:Abstract Along the Pacific coast of North America, four introduced cordgrass species ( Spartina alterniflora, S. anglica, S. patens and S. densiflora ) have thus far invaded five isolated estuaries. Dense growth of introduced Spartina spp. reduces open mud feeding habitats of shorebirds, while in the upper intertidal, introduced Spartina spp. compete with native salt marsh vegetation. Prediction of Spartina invasions is facilitated by the remarkable restriction of these species to distinct estuarine habitats which generally lack interspecific competitors and herbivores. We used physical characteristics to identify 31 specific sites along the US Pacific coast that are vulnerable to future Spartina invasions and then used species characteristics, like native latitudinal range and past invasion success, to predict which Spartina species will be likely to invade these sites in the future. All 31 sites were predicted to be vulnerable to S. alterniflora , while the other invasive Spartina spp. may be restricted to a subset of the vulnerable sites. At a finer scale, within a vulnerable site, the mean tidal range can be used to predict the extent of spatial spread of a Spartina sp. after colonization. These prediction techniques might be used to identify and prioritize sites for protection against future invasions. We suggest that a cost-effective way to prevent the transformation of unique North American Pacific mudflat and saltmarsh communities into introduced Spartina -dominated marshes is to survey the vulnerable sites frequently and eliminate introduced Spartina spp. propagules before they spread.
Xiaohui Wu - One of the best experts on this subject based on the ideXlab platform.
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the full length transcriptome of Spartina alterniflora reveals the complexity of high salt tolerance in monocotyledonous halophyte
Plant and Cell Physiology, 2020Co-Authors: Wenbin Ye, Taotao Wang, Qinzhen Li, Guoli Ji, Xiaohui WuAbstract:Spartina alterniflora (Spartina) is the only halophyte in the salt marsh. However, the molecular basis of its high salt tolerance remains elusive. In this study, we used PacBio full-length single molecule long-read sequencing and RNA-seq to elucidate the transcriptome dynamics of high salt tolerance in Spartina by salt-gradient experiments. High quality unigenes, transcription factors, non-coding RNA and Spartina specific transcripts were identified. Co-expression network analysis found that protein kinases-encoding genes (SaOST1, SaCIPK10 and SaLRRs) are hub genes in the salt tolerance regulatory network. High salt stress induced expression of transcription factors but repressed expression of long non-coding RNAs. The Spartina transcriptome is closer to rice than Arabidopsis, and a higher proportion of transporter and transcription factor-encoding transcripts have been found in Spartina. Transcriptome analysis showed that high salt stress induced the expression of carbohydrate metabolism, especially cell wall biosynthesis-related genes in Spartina, while repressed its expression in rice. Compared with rice, high salt stress highly induced the expression of stress response, protein modification and redox-related gene expression, and greatly inhibited translation in Spartina. High salt stress also induced alternative splicing in Spartina, while differentially expressed alternative splicing events associated with photosynthesis were over-represented in Spartina but not in rice. Finally, we built the SAPacBio website for visualizing full-length transcriptome sequences, transcription factors, ncRNAs, salt-tolerant genes, and alternative splicing events in Spartina. Overall, this study suggests that salt tolerance mechanism in Spartina is different from rice from many aspects and is far more complex than expected.
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the full length transcriptome of Spartina alterniflora reveals the complexity of high salt tolerance in monocotyledonous halophyte
bioRxiv, 2019Co-Authors: Wenbin Ye, Taotao Wang, Qinzhen Li, Guoli Ji, Xiaohui WuAbstract:Spartina alterniflora (Spartina) is the only halophyte in the salt marsh. However, the molecular basis of its high salt tolerance remains elusive. In this study, we used PacBio full-length single molecule long-read sequencing and RNA-seq to elucidate the transcriptome dynamics of high salt tolerance in Spartina by salt-gradient experiments (0, 350, 500 and 800 mM NaCl). We systematically analyzed the gene expression diversity and deciphered possible roles of ion transporters, protein kinases and photosynthesis in salt tolerance. Moreover, the co-expression network analysis revealed several hub genes in salt stress regulatory networks, including protein kinases such as SaOST1, SaCIPK10 and three SaLRRs. Furthermore, high salt stress affected the gene expression of photosynthesis through down-regulation at the transcription level and alternative splicing at the post-transcriptional level. In addition, overexpression of two Spartina salt-tolerant genes SaHSP70-I and SaAF2 in Arabidopsis significantly promoted the salt tolerance of transgenic lines. Finally, we built the SAPacBio website for visualizing the full-length transcriptome sequences, transcription factors, ncRNAs, salt-tolerant genes, and alternative splicing events in Spartina. Overall, this study sheds light on the high salt tolerance mechanisms of monocotyledonous-halophyte and demonstrates the potential of Spartina genes for engineering salt-tolerant plants.
Jiakuan Chen - One of the best experts on this subject based on the ideXlab platform.
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potential impacts of invasive Spartina alterniflora on spring bird communities at chongming dongtan a chinese wetland of international importance
Estuarine Coastal and Shelf Science, 2009Co-Authors: Chi Yeung Choi, Jiakuan Chen, Bo LiAbstract:Invasive smooth cordgrass (Spartina alterniflora, hereafter Spartina) has been expanding rapidly in the estuarine wetlands at Chongming Dongtan (East China) at the expense of native sea-bulrush (Scirpus mariqueter, hereafter Scirpus) and common reed (Phragmites australis, hereafter Phragmites). To examine the potential impacts of the Spartina invasion on bird diversity, we compared the abundance and species richness of birds in habitats created by Spartina, Phragmites, Spartina mixed with Phragmites, Scirpus, and the bare intertidal zone at Chongming Dongtan in spring 2008. Most birds were recorded in the native habitats, with songbirds and breeding birds being most abundant in the Phragmites habitats, and waterbirds and migrants being most abundant in the Scirpus habitats and bare intertidal zone. Both species number and population densities of birds were lower in the exotic Spartina habitats than in the other four habitats. Although some songbirds and breeding birds used the Spartina-invaded habitats, and even preferred Spartina-invaded habitats to Scirpus habitats and bare intertidal zone, their densities were lower in the Spartina-invaded habitats than in the native Phragmites habitats. This might have resulted from the dense Spartina stands restricting bird movement and providing insufficient useable food for most birds. We conclude that the spread of exotic Spartina has negative impacts on local bird communities. Because Chongming Dongtan is an important stopover site for energy replenishment of shorebirds in the East Asian-Australasian Flyway, urgent measures are needed to control further spread of Spartina and to restore the native habitats for birds.
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Effects of saltmarsh invasion by Spartina alterniflora on arthropod community structure and diets
Biological Invasions, 2008Co-Authors: Yu-tong Wu, Jiakuan Chen, Cheng-huan Wang, Xiao-dong Zhang, Bin Zhao, Lifen Jiang, Bo LiAbstract:Invasive plants strongly affect physical and biotic environments of native ecosystems. Insects and other arthropods as one of the major components of many ecosystems are very sensitive to subtle changes in abiotic and biotic environments. We examined the effects of exotic Spartina alterniflora invasion on community structure and diets of arthropods in a saltmarsh previously dominated by native Phragmites australis in Yangtze River estuary through net sweeping and plant harvesting methods and stable isotope analysis. Our results showed that diversity indices were not significantly different between exotic and native plant communities, but the total abundance of insects estimated through plant harvesting method was found to be lower in Spartina monoculture than that in Phragmites monoculture. Community structure of insects in Spartina monoculture was dissimilar to that in Phragmites monoculture and Phragmites–Spartina mixture. Moreover, stable carbon isotope patterns of arthropods were significantly different between Phragmites and Spartina monocultures. Although some native arthropods (perhaps generalists) shifted their diets, many native taxa did prefer Phragmites to Spartina even in Spartina monoculture. Spartina invasions resulted in reduced abundances of some arthropds, and increased dominance of others feeding preferably on Spartina. This study provides evidence that invasive plants can change the community structure and diets of native arthropods, which will eventually alter the arthropod food web, and affect the integrity and functioning of native ecosystems within a nature reserve that has been set aside for conserving the native biodiversity and maintaining the ecosystem integrity. In this sense, Spartina invasions in the Yangtze River estuary need to be managed appropriately.
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litter pool sizes decomposition and nitrogen dynamics in Spartina alterniflora invaded and native coastal marshlands of the yangtze estuary
Oecologia, 2008Co-Authors: Jiakuan Chen, Chengzhang Liao, Changming Fang, Bo LiAbstract:Past studies have focused primarily on the effects of invasive plants on litter decomposition at soil surfaces. In natural ecosystems, however, considerable amounts of litter may be at aerial and belowground positions. This study was designed to examine the effects of Spartina alterniflora invasion on the pool sizes and decomposition of aerial, surficial, and belowground litter in coastal marsh- lands, the Yangtze Estuary, which were originally occupied by two native species, Scirpus mariqueter and Phragmites australis. We collected aerial and surficial litter of the three species once a month and belowground litter once every 2 months. We used the litterbag method to quantify litter decomposition at the aerial, surficial and belowground positions for the three species. Yearly averaged litter mass in the Spartina stands was 1.99 kg m -2 ; this was 250 and 22.8% higher than that in the Scirpus (0.57 kg m -2 ) and Phragmites (1.62 kg m -2 ) stands, respectively. The litter in the Spartina stands was primarily distributed in the air (45%) and belowground (48%), while Scirpus and Phragmites litter was mainly allocated to belowground positions (85 and 59%, respectively). The averaged decomposition rates of aerial, surficial, and belowground litter were 0.82, 1.83, and 1.27 year -1 for Spartina, respectively; these were 52, 62 and 69% of those for Scirpus litter at corresponding positions and 158, 144 and 78% of those for Phragmites litter, respec- tively. The differences in decomposition rates between Spartina and the two native species were largely due to differences in litter quality among the three species, partic- ularly for the belowground litter. The absolute amount of nitrogen increased during the decomposition of Spartina stem, sheath and root litter, while the amount of nitrogen in Scirpus and Phragmites litter declined during decomposition for all tissue types. Our results suggest that Spartina invasion altered the carbon and nitrogen cycling in the coastal marshlands of China.
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invasion of Spartina alterniflora enhanced ecosystem carbon and nitrogen stocks in the yangtze estuary china
Ecosystems, 2007Co-Authors: Chengzhang Liao, Jiakuan Chen, Lifen Jiang, Xuhui Zhou, Xiaowen Wu, Changming Fang, Bo LiAbstract:Whether plant invasion increases ecosystem carbon (C) stocks is controversial largely due to the lack of knowledge about differences in ecophysiological properties between invasive and native species. We conducted a field experiment in which we measured ecophysiological properties to explore the response of the ecosystem C stocks to the invasion of Spartina alterniflora (Spartina) in wetlands dominated by native Scirpus mariqueter (Scirpus) and Phragmites australis (Phragmites) in the Yangtze Estuary, China. We measured growing season length, leaf area index (LAI), net photosynthetic rate (Pn), root biomass, net primary production (NPP), litter quality and litter decomposition, plant and soil C and nitrogen (N) stocks in ecosystems dominated by the three species. Our results showed that Spartina had a longer growing season, higher LAI, higher Pn, and greater root biomass than Scirpus and Phragmites. Net primary production (NPP) was 2.16 kg C m−2 y−1 in Spartina ecosystems, which was, on average, 1.44 and 0.47 kg C m−2 y−1 greater than that in Scirpus and Phragmites ecosystems, respectively. The litter decomposition rate, particularly the belowground decomposition rate, was lower for Spartina than Scirpus and Phragmites due to the lower litter quality of Spartina. The ecosystem C stock (20.94 kg m−2) for Spartina was greater than that for Scirpus (17.07 kg m−2), Phragmites (19.51 kg m−2) and the mudflats (15.12 kg m−2). Additionally, Spartina ecosystems had a significantly greater N stock (698.8 g m−2) than Scirpus (597.1 g m−2), Phragmites ecosystems (578.2 g m−2) and the mudflats (375.1 g m−2). Our results suggest that Spartina invasion altered ecophysiological processes, resulted in changes in NPP and litter decomposition, and ultimately led to enhanced ecosystem C and N stocks in the invaded ecosystems in comparison to the ecosystems with native species.
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short term c4 plant Spartina alterniflora invasions change the soil carbon in c3 plant dominated tidal wetlands on a growing estuarine island
Soil Biology & Biochemistry, 2006Co-Authors: Jiakuan Chen, Xiaoli Cheng, Jiquan Chen, Bo LiAbstract:Spartina alterniflora is an invasive C4 perennial grass, native to North America, and has spread rapidly along the east coast of China since its introduction in 1979. Since its intentional introduction to the Jiuduansha Island in the Yangtze River estuary, Spartina alterniflora community has become one of the dominant vegetation types. We investigated the soil carbon in the Spartina alterniflora community and compared it with that of the native C3 Scirpus mariqueter community by measuring total soil carbon (TC), soil organic carbon (SOC), total soil nitrogen (TN), and the stable carbon isotope composition (d 13 C) of various fractions. TC and SOC were significantly higher in Spartina alterniflora in the top 60 cm of soil. However, there was no significant difference in soil inorganic carbon (IC) between the two communities. Stable carbon isotopic analysis suggests that the fraction of SOC pool contributed by Spartina alterniflora varied from 0.90% to 10.64% at a soil depth of 0–100 cm with a greater percentage between 20 and 40 cm deep soils. The d 13 C decreased with increasing soil depth in both communities, but the difference in d 13 C among layers of the top 60 cm soil was significant (po0:05), while that for the deeper soil layers (460 cm) was not detected statistically. The changes in d 13 C with depth appeared to be associated with the small contribution of residues from Spartina alterniflora at greater soil depth that was directly related to the vertical root distribution of the species. r 2006 Elsevier Ltd. All rights reserved.
