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1.
Franziska Eller Carla Lambertini Loc Xuan Nguyen Hans Brix 《Global Change Biology》2014,20(2):531-543
The prospective rise in atmospheric CO2 and temperature may change the distribution and invasive potential of a species; and intraspecific invasive lineages may respond differently to climate change. In this study, we simulated a future climate scenario with simultaneously elevated atmospheric CO2 and temperature, and investigated its interaction with soil salinity, to assess the effects of global change on the ecophysiology of two competing haplotypes of the wetland grass Phragmites australis, that are invasive in the coastal marshes of North America. The two haplotypes with the phenotypes ‘EU‐type’ (Eurasian haplotype) and ‘Delta‐type’ (Mediterranean haplotype), were grown at 0‰ and 20‰ soil salinity, and at ambient or elevated climatic conditions (700 ppm CO2, +5 °C) in a phytotron system. The aboveground growth of both phenotypes was highest at the elevated climatic conditions. Growth at 20‰ salinity resulted in declined aboveground growth, lower transpiration rates (E), stomata conductance (gs), specific leaf area, photosynthetic pigment concentrations, and a reduced photosynthetic performance. The negative effects of salinity were, however, significantly less severe at elevated CO2 and temperature than at the ambient climatic conditions. The Delta‐type P. australis had higher shoot elongation rates than the EU‐type P. australis, particularly at high salinity. The Delta‐type also had higher maximum light‐saturated rates of photosynthesis (Asat), maximum carboxylation rates of Rubisco (Vcmax), maximum electron transport rates (Jmax), triose phosphate utilization rates (Tp), stomata conductance (gs), as well as higher Rubisco carboxylation‐limited, RuBP regeneration‐limited and Tp‐regeneration limited CO2 assimilation rates than the EU‐type under all growth conditions. Our results suggest that the EU‐type will not become dominant over the Delta‐type, since the Delta‐type has superior ecophysiological traits. However, the projected rise in atmospheric CO2 and temperature will alleviate the effects of salinity on both phenotypes and facilitate their expansion into more saline areas. 相似文献
2.
- Heavy metal allocation and the mechanism(s) of metal sequestration in different clonal organs, micro‐domains and subcellular structures has not been systematically studied for rhizomatous perennial plants. It is thus pertinent to investigate knowledge of the speciation and distribution characteristics of Cu in Phragmites australis to elucidating the mobility of metals in wetland plants after their uptake via root systems so as to facilitate development of strategies to enhance Cu tolerance.
- This study investigated the distributions of Cu in P. australis root, stem and leaf using ICP‐MS, synchrotron‐based X‐ray micro‐fluorescence and X‐ray absorption spectroscopy, then evaluated the effects of Cu on cellular structure and ultrastructure via transmission electron microscopy.
- The results indicate a clear preferential localisation of Cu in the roots as compared with the shoots (stems and leaves). The intensity of Cu in the vascular bundles was higher than that in the surrounding epidermis and the endodermis and parenchyma outside the medullary cavity. The dominant chemical form of Cu in P. australis was similar to Cu citrate.
- The results suggest that although Cu can be easily transported into the vascular tissues in roots and stems via Cu citrate, most of the metal absorbed by plants is retained in the roots because if its high binding to the cell wall, thus preventing metal translocation to aerial parts of the plants. Therefore, P. australis showed a high capacity to accumulate Cu in roots, being therefore a suitable species for phytostabilisation interventions.
3.
Phragmites or Common Reed (Phragmites australis) is a tall rhizomatous cosmopolitan grass. While native to Australia, it can be invasive in wetlands, forming dense monocultures and reducing their ecological integrity. We assessed the potential for the cutting of Phragmites reeds prior to planting to promote the establishment of indigenous shrubs that might ultimately outcompete Phragmites. We established ten 5 m × 5 m quadrats in an area dominated by Phragmites, brush‐cut the reeds to ground level in five of them and left five uncut as controls. Within each quadrat, we planted 20 plants (~40 cm tall) of each of five indigenous shrub species, unguarded (4 plants/m2). We surveyed the plants one month after planting and annually for the following four years for survival, height and browsing damage. Browsing damage to plants was common (>50%) and unaffected by cutting. After four years, overall plant survival rates were ~25% and mean plant heights for the five shrub species ranged between 120 and 174 cm. Cutting of Phragmites had no positive effect on plant survival or height. In fact, two Melaleuca species grew taller in the uncut quadrats. Cutting of Phragmites reed beds prior to planting is unlikely to promote the establishment of woody plantings. However, planting within established Phragmites with or without prior brush‐cutting is worthy of further trialling as a potential tool for reinstating native diversity at Phragmites‐dominated sites. 相似文献
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5.
Lele Liu Cuiping Pei Shuna Liu Xiao Guo Ning Du Weihua Guo 《Ecology and evolution》2018,8(13):6615-6624
While many introduced invasive species can increase genetic diversity through multiple introductions and/or hybridization to colonize successfully in new environments, others with low genetic diversity have to persist by alternative mechanisms such as epigenetic variation. Given that Phragmites australis is a cosmopolitan reed growing in a wide range of habitats and its invasion history, especially in North America, has been relatively well studied, it provides an ideal system for studying the role and relationship of genetic and epigenetic variation in biological invasions. We used amplified fragment length polymorphism (AFLP) and methylation‐sensitive (MS) AFLP methods to evaluate genetic and epigenetic diversity and structure in groups of the common reed across its range in the world. Evidence from analysis of molecular variance (AMOVA) based on AFLP and MS‐AFLP data supported the previous conclusion that the invasive introduced populations of P. australis in North America were from European and Mediterranean regions. In the Gulf Coast region, the introduced group harbored a high level of genetic variation relative to originating group from its native location, and it showed epigenetic diversity equal to that of the native group, if not higher, while the introduced group held lower genetic diversity than the native. In the Great Lakes region, the native group displayed very low genetic and epigenetic variation, and the introduced one showed slightly lower genetic and epigenetic diversity than the original one. Unexpectedly, AMOVA and principal component analysis did not demonstrate any epigenetic convergence between native and introduced groups before genetic convergence. Our results suggested that intertwined changes in genetic and epigenetic variation were involved in the invasion success in North America. Although our study did not provide strong evidence proving the importance of epigenetic variation prior to genetic, it implied the similar role of stable epigenetic diversity to genetic diversity in the adaptation of P. australis to local environment. 相似文献
6.
Sarah S. Roley Jennifer L. Tank Michael R. Grace Perran L.M. Cook 《Freshwater Biology》2018,63(4):353-365
- Wetlands are often biogeochemical hotspots, and they can remove excess N via denitrification and assimilatory uptake. Wetlands are also susceptible to plant invasions, but the effect of invasive plants on denitrification in freshwater wetland sediments is not well‐studied.
- Two distinct mechanisms suggest the potential for invasive plants to alter denitrification. First, invasive plants often produce more biomass than non‐invasive species, thus potentially providing additional carbon (C) for denitrifiers. Second, some invasive wetland plants funnel more oxygen into the root zone than non‐invasive plants, potentially stimulating coupled nitrification–denitrification.
- Using the push–pull isotope pairing technique, we measured denitrification and coupled nitrification–denitrification in the sediments beneath monoculture plots of Phragmites australis and Typha domingensis, and beneath unvegetated sediments, in an urban wetland in Melbourne, Australia. We also measured pore water nutrient concentrations and calculated the diffusive flux of nutrients from the sediments into the overlying water column.
- We hypothesised that plots containing P. australis would have the highest denitrification and coupled nitrification–denitrification rates, followed by plots containing T. domingensis, with the lowest rates in the unvegetated plots, as a result of higher C and oxygen availability.
- Instead, we found that denitrification and coupled nitrification–denitrification rates were highly variable, with no difference among plot type. However, we did find that diffusive flux of ammonium from the sediments into the water column was lower in the vegetated plots than in the unvegetated plots, suggesting that vegetation enhances wetland N retention via plant assimilatory uptake.
7.
Christine B. Rohal Chad Cranney Eric L. G. Hazelton Karin M. Kettenring 《Ecology and evolution》2019,9(24):13835-13849
The outcomes of invasive plant removal efforts are influenced by management decisions, but are also contingent on the uncontrolled spatial and temporal context of management areas. Phragmites australis is an aggressive invader that is intensively managed in wetlands across North America. Treatment options have been understudied, and the ecological contingencies of management outcomes are poorly understood. We implemented a 5‐year, multi‐site experiment to evaluate six Phragmites management treatments that varied timing (summer or fall) and types of herbicide (glyphosate or imazapyr) along with mowing, plus a nonherbicide solarization treatment. We evaluated treatments for their influence on Phragmites and native plant cover and Phragmites inflorescence production. We assessed plant community trajectories and outcomes in the context of environmental factors. The summer mow, fall glyphosate spray treatment resulted in low Phragmites cover, high inflorescence reduction, and provided the best conditions for native plant recruitment. However, returning plant communities did not resemble reference sites, which were dominated by ecologically important perennial graminoids. Native plant recovery following initial Phragmites treatments was likely limited by the dense litter that resulted from mowing. After 5 years, Phragmites mortality and native plant recovery were highly variable across sites as driven by hydrology. Plots with higher soil moisture had greater reduction in Phragmites cover and more robust recruitment of natives compared with low moisture plots. This moisture effect may limit management options in semiarid regions vulnerable to water scarcity. We demonstrate the importance of replicating invasive species management experiments across sites so the contingencies of successes and failures can be better understood. 相似文献
8.
Phragmites or Common Reed (Phragmites australis) is a natural component of many wetlands but can be highly invasive. Phragmites is encroaching into important mudflat habitat areas of the Ramsar‐listed Seaford Wetlands (Melbourne, Victoria), which are critical for migratory birds. We assessed the efficacy of slashing as a means of controlling Phragmites by establishing twelve 5 m × 5 m quadrats within mature Phragmites reed beds and slashing half of them. The response of Phragmites to slashing was highly variable and dependent on the elevation (i.e. subsequent flooding) of the slashed quadrats. Phragmites regrowth was minimal in lower‐lying quadrats which were wholly inundated for several months each of the following two years (to a mean depth of ~22 cm). In contrast, in quadrats of higher elevation, which were mostly only partially or shallowly inundated, Phragmites recovered almost completely within 10 months. In quadrats that were not slashed there was no change in Phragmites cover (i.e. it remained ~100%) irrespective of flooding extent. It is suspected that prolonged flooding above the height of the remaining stubble is necessary to prevent recovery. Thus, slashing may be a successful means of controlling Phragmites when low‐lying areas are targeted and these are subsequently flooded to a sufficient depth (e.g. >20 cm) for at least several months. 相似文献
9.
In the oligohaline Alloway Creek watershed of the upper Delaware Bay, invasive Phragmites australis (Common reed; hereafter Phragmites) has been removed in an attempt to restore tidal marshes to pre‐invasion form and function. In order to determine the effects of Phragmites on nekton use of intertidal creeks and to evaluate the success of this restoration, intertidal creek nekton assemblages were sampled with weirs from May to November for 7 years (1999‐2005) in three marsh types: natural Spartina alterniflora (Smooth cordgrass; hereafter Spartina), sites treated for Phragmites removal (hereafter referred to as Treated), and invasive Phragmites marshes. Replicate intertidal creek collections in all three marsh types consisted primarily of resident nekton and were dominated by a relatively low number of ubiquitous intertidal species. The Treated marsh nekton assemblage was distinguished by greater abundances of most nekton, especially Fundulus heteroclitus (Mummichog). Phragmites had little impact on nekton use of intertidal creeks over this period as evidenced by similar nekton assemblages in the Spartina and Phragmites marshes for most years. Long‐term assemblage‐level analyses and nekton abundances indicated that the Treated marsh provided enhanced conditions for intertidal creek nekton. The response of intertidal creek nekton suggests that the stage of the restoration may influence the results of comparisons between the marsh types and should be considered when evaluating marsh restorations. 相似文献
10.
N. Zhang J. W. Zhang Y. H. Yang X. Y. Li J. X. Lin Z. L. Li L. Y. Cheng J. F. Wang C. S. Mu A. X. Wang 《Plant biology (Stuttgart, Germany)》2015,17(4):893-903
Clonal propagation is important for the survival and maintenance of the common reed Phragmites australis. Pot culture experiments were conducted to investigate the effects of lead (Pb) concentration (0, 500, 1500, 3000, 4500 mg·kg?1) and water stress on the clonal reproductive ability of this species. The Pb concentration found in plant organs, in decreasing order, was roots >shoots >rhizomes. There was a negative relationship between the growth of clonal propagative modules (excluding axillary shoot buds) and Pb concentrations, which caused a decrease in biomass, rhizome growth and number of axillary and apical rhizome buds. Daughter axillary shoots exhibited a tolerance strategy, with no significant change in their number; the axillary and apical rhizome buds, daughter apical rhizome shoots and rhizomes exhibited compensatory growth during the late stage of Pb (excluding 4500 mg·kg?1) treatment in a wet environment. Pb applications above 500 mg·kg?1 reduced these parameters significantly in the drought treatment, except for the number of axillary shoot buds, which did not change. Our results indicate that clonal propagative resistance to Pb contamination can occur via tolerance strategies, compensatory growth and a Pb allocation strategy, enabling these reeds to maintain population stability in wet environments. However, clonal modular growth and reproductive ability were inhibited significantly by the interaction between drought and Pb, which would cause a decline in P. australis populations in a dry environment. Lead concentrations of 4500 and 500 mg·kg?1 in soils might meet or exceed the Pb tolerance threshold of clonally propagated reeds in wet and dry environments, respectively. 相似文献
11.
Understanding the processes that control deep soil carbon (C) dynamics and accumulation is of key importance, given the relevance of soil organic matter (SOM) as a vast C pool and climate change buffer. Methodological constraints of measuring SOM decomposition in the field prevent the addressing of real‐time rhizosphere effects that regulate nutrient cycling and SOM decomposition. An invasive lineage of Phragmites australis roots deeper than native vegetation (Schoenoplectus americanus and Spartina patens) in coastal marshes of North America and has potential to dramatically alter C cycling and accumulation in these ecosystems. To evaluate the effect of deep rooting on SOM decomposition we designed a mesocosm experiment that differentiates between plant‐derived, surface SOM‐derived (0–40 cm, active root zone of native marsh vegetation), and deep SOM‐derived mineralization (40–80 cm, below active root zone of native vegetation). We found invasive P. australis allocated the highest proportion of roots in deeper soils, differing significantly from the native vegetation in root : shoot ratio and belowground biomass allocation. About half of the CO2 produced came from plant tissue mineralization in invasive and native communities; the rest of the CO2 was produced from SOM mineralization (priming). Under P. australis, 35% of the CO2 was produced from deep SOM priming and 9% from surface SOM. In the native community, 9% was produced from deep SOM priming and 44% from surface SOM. SOM priming in the native community was proportional to belowground biomass, while P. australis showed much higher priming with less belowground biomass. If P. australis deep rooting favors the decomposition of deep‐buried SOM accumulated under native vegetation, P. australis invasion into a wetland could fundamentally change SOM dynamics and lead to the loss of the C pool that was previously sequestered at depth under the native vegetation, thereby altering the function of a wetland as a long‐term C sink. 相似文献
12.
Iftekhar Alam Kyung‐Hee Kim Suk‐Yoon Kwon Jung‐Hoon Sohn Sun‐Hyung Kim Gongshe Liu Byung‐Hyun Lee 《Global Change Biology Bioenergy》2013,5(1):73-80
Reed (Phragmites communis) is a potential bioenergy plant. We report on its first Agrobacterium‐mediated transformation using mature seed‐derived calli. The Agrobacterium strains LBA4404, EHA105, and GV3101, each harboring the binary vector pIG121Hm, were used to optimize T‐DNA delivery into the reed genome. Bacterial strain, cocultivation period and acetosyringone concentration significantly influenced the T‐DNA transfer. About 48% transient expression and 3.5% stable transformation were achieved when calli were infected with strain EHA105 for 10 min under 800 mbar negative pressure and cocultivated for 3 days in 200 μm acetosyringone containing medium. Putative transformants were selected in 25 mg l?1 hygromycin B. PCR, and Southern blot analysis confirmed the presence of the transgenes and their stable integration. Independent transgenic lines contained one to three copies of the transgene. Transgene expression was validated by RT‐PCR and GUS staining of stems and leaves. 相似文献
13.
- Modification of aquatic habitats by human activity changes physical and genetic connections and poses a risk to the ecological stability of wetlands. Altered water regimes and land use can change dispersal patterns due to altered landscape permeability that will vary with the dispersal vector.
- We hypothesised that modifications to the Gippsland Lakes wetlands of south‐eastern Australia, affecting connectivity over many decades, would be reflected differently in the genetic structure of two widespread polyploid wetland plants, Phragmites australis and Triglochin procera due to different dispersal pathways.
- We found that genetic connectivity over the region, assessed with microsatellite markers, was high for both species. Phragmites australis consisted of a single genetic cluster, supporting the notion that wind is its primary dispersal vector. Contrary to expectations, Triglochin procera also showed high genetic connectivity, despite some differentiation between two wetland regions (Lake King and Lake Wellington). Spatial genetic autocorrelation revealed a high incidence of local‐scale gene flow in both species.
- We conclude that despite significant anthropogenic habitat modification, genetic connectivity remains high for both species. The current patterns may reflect historical connectivity, with plant longevity buffering the effect of disruptions to gene flow, or contemporary dispersal may be sufficient to overcome anthropogenic influences. Waterbirds are likely to be a more significant dispersal vector of T. procera than anticipated because water dispersal alone cannot explain connectivity across river systems. As wetland systems are put under increasing pressure, we need to ensure that natural dispersal mechanisms still operate to maintain connectivity.
14.
Trip Lamb Teresa C. Justice Michael S. Brewer Paul E. Moler Heidi Hopkins Jason E. Bond 《Ecology and evolution》2018,8(11):5254-5266
Florida scrub is a xeric ecosystem associated with the peninsula's sand ridges, whose intermittent Pliocene–Pleistocene isolation is considered key to scrub endemism. One scrub origin hypothesis posits endemics were sourced by the Pliocene dispersal of arid‐adapted taxa from southwestern North America; a second invokes Pleistocene migration within eastern North America. Only one study to date has explicitly tested these competing hypotheses, supporting an eastern origin for certain scrub angiosperms. For further perspective, we conducted a genetic analysis of an endemic arthropod, the Florida sand cockroach (Arenivaga floridensis), with two aims: (1) to reconstruct the peninsular colonization and residence history of A. floridensis and (2) determine whether its biogeographic profile favors either origin hypothesis. We sequenced the cox2 mitochondrial gene for 237 specimens (65 populations) as well as additional loci (cox1, nuclear H3) for a subset of Florida roaches and congeners. Using Network and Bayesian inference methods, we identified three major lineages whose genetic differentiation and phylogeographical structure correspond with late Pliocene peninsula insularization, indicating Arenivaga was present and broadly distributed in Florida at that time. Stem and crown divergence estimates (6.36 Ma; 2.78 Ma) between A. floridensis and western sister taxa span a period of extensive dispersal by western biota along an arid Gulf Coast corridor. These phylogeographical and phylogenetic results yield a biogeographic profile consistent with the western origin hypothesis. Moreover, age estimates for the roach's peninsular residence complement those of several other endemics, favoring a Pliocene (or earlier) inception of the scrub ecosystem. We argue that eastern versus western hypotheses are not mutually exclusive; rather, a composite history of colonization involving disparate biotas better explains the diverse endemism of Florida scrub. 相似文献
15.
- Arbuscular mycorrhizal fungi (AMF) is an effective way to remove heavy metals’ inhibition on plants, however, few relevant research attempts have been made to determine the contribution of AMF to the physiological and biochemical changes related to the enhanced copper tolerance of Phragmites australis under metal‐stressed conditions.
- In this study, the effects of AMF inoculation on P. australis under different concentrations of copper stress were investigated according to the changes in the parameters related to growth and development, and photosynthetic charateristics. Then, differentially expressed proteins (DEPs) were evaluated by the Isobaric Tag for Relative and Absolute Quantification (iTRAQ) system, which could accurately quantify the DEPs by measuring peak intensities of reporter ions in tandem mass spectrometry (MS/MS) spectra.
- It was found that AMF inoculation may relieve the photosynthesis inhibition caused by copper stress on P. australis and thus promote growth. Proteomic analysis results showed that under copper stress, the inoculation of R. irregularis resulted in a total of 459 differently‐expressed proteins (200 up‐regulated and 259 down‐regulated) in root buds. In addition, the photosynthetic changes caused by AMF inoculation mainly involve the up‐regulated expression of transmembrane protein–pigment complexes CP43 (photosystem II) and FNR (ferredoxin‐NADP+ oxidoreductase related to photosynthetic electron transport).
- These results indicate that AMF could effectively improve the growth and physiological activity of P. australis under copper stress, and thus provides a new direction and instructive evidence for determining the mechanisms by which AMF inoculation enhances the copper tolerance of plants.
16.
Christine K. Weldrick Rowan Trebilco Diana M. Davies Kerrie M. Swadling 《Ecology and evolution》2019,9(14):8119-8132
Pteropods are a group of small marine gastropods that are highly sensitive to multiple stressors associated with climate change. Their trophic ecology is not well studied, with most research having focused primarily on the effects of ocean acidification on their fragile, aragonite shells. Stable isotopes analysis coupled with isotope‐based Bayesian niche metrics is useful for characterizing the trophic structure of biological assemblages. These approaches have not been implemented for pteropod assemblages. We used isotope‐based Bayesian niche metrics to investigate the trophic relationships of three co‐occurring pteropod species, with distinct feeding behaviors, sampled from the Southern Kerguelen Plateau area in the Indian Sector of the Southern Ocean—a biologically and economically important but poorly studied region. Two of these species were gymnosomes (shell‐less pteropods), which are traditionally regarded as specialist predators on other pteropods, and the third species was a thecosome (shelled pteropod), which are typically generalist omnivores. For each species, we aimed to understand (a) variability and overlap among isotopic niches; and (b) whether there was a relationship between body size and trophic position. Observed isotopic niche areas were broadest for gymnosomes, especially Clione limacina antarctica, whose observed isotopic niche area was wider than expected on both δ13C and δ15N value axes. We also found that trophic position significantly increased with increasing body length for Spongiobranchaea australis. We found no indication of a dietary shift toward increased trophic position with increasing body size for Clio pyramidata f. sulcata. Trophic positions ranged from 2.8 to 3.5, revealing an assemblage composed of both primary and secondary consumer behaviors. This study provides a comprehensive comparative analysis on trophodynamics in Southern Ocean pteropod species, and supports previous studies using gut content, fatty acid and stable isotope analyses. Combined, our results illustrate differences in intraspecific trophic behavior that may be attributed to differential feeding strategies at species level. 相似文献
17.
Intraspecific variation in genotypically determined traits can influence ecosystem processes. Therefore, the impact of climate change on ecosystems may depend, in part, on the distribution of plant genotypes. Here we experimentally assess effects of climate warming and excess nitrogen supply on litter decomposition using 12 genotypes of a cosmopolitan foundation species collected across a 2100 km latitudinal gradient and grown in a common garden. Genotypically determined litter‐chemistry traits varied substantially within and among geographic regions, which strongly affected decomposition and the magnitude of warming effects, as warming accelerated litter mass loss of high‐nutrient, but not low‐nutrient, genotypes. Although increased nitrogen supply alone had no effect on decomposition, it strongly accelerated litter mass loss of all genotypes when combined with warming. Rates of microbial respiration associated with the leaf litter showed nearly identical responses as litter mass loss. These results highlight the importance of interactive effects of environmental factors and suggest that loss or gain of genetic variation associated with key phenotypic traits can buffer, or exacerbate, the impact of global change on ecosystem process rates in the future. 相似文献
18.
Igor Oliveira Braga de Morais Daniel Danilewicz Alexandre Novaes Zerbini William Edmundson Ian B. Hart Guilherme Augusto Bortolotto 《Mammal Review》2017,47(1):11-23
- Historical catch records from whaling activity are crucial for assessments of whale populations. However, several gaps in the exploitation history for many populations from before the twentieth century create limitations that may lead to overestimates of the recovery of these populations. The history of modern whaling along the Brazilian coast is relatively well known. However, several questions relating to the pre‐modern period, during and before the nineteenth century, remain unanswered. For example, the level of exploitation of humpback whales Megaptera novaeangliae and southern right whales Eubalaena australis in this period is unknown.
- Pre‐modern whaling in Brazil began in 1602 and lasted until the 1920s. Whales were captured using manual harpoons from either rowing boats or sailing boats, and processed at land stations called ‘armações’. A review of the history and oil production of these stations indicates that substantial catches occurred.
- Pre‐modern whaling records also indicate the collapse of the southern right whale population in the western South Atlantic Ocean. Increasingly rare reports of sightings for the nineteenth century and the closing of the last armação in the breeding grounds off southern Brazil indicate that this population collapsed by 1830.
- Armações operating in north‐eastern Brazil remained active through the 1800s, and targeted humpback whales until modern whaling techniques were introduced in the early 1900s. It is estimated that between approximately 11000 and 32000 individuals of this species were captured at these coastal whaling stations from 1830 to 1924.
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The southern coast of Australia is composed of three distinct biogeographic provinces distinguished primarily by intertidal community composition. Several ecological mechanisms have been proposed to explain their formation and persistence, but no consensus has been reached. The marine clam Lasaea australis is arguably the most common bivalve on southern Australian rocky shores and occurs in all three provinces. Here, we tested if this species exhibits cryptic genetic structuring corresponding to the provinces and if so, what mechanisms potentially drove its divergence. Variation in two mitochondrial genes (16S and COIII) and one nuclear gene (ITS2) was assayed to test for genetic structuring and to reconstruct the clam's phylogenetic history. Our results showed that L. australis is comprised of three cryptic mitochondrial clades, each corresponding almost perfectly to one of the three biogeographic provinces. Divergence time estimates place their cladogenesis in the Neogene. The trident‐like topology and Neogene time frame of L. australis cladogenesis are incongruent with Quaternary vicariance predictions: a two‐clade topology produced by Pleistocene Bass Strait land bridge formation. We hypothesize that the interaction of the Middle Miocene Climate Transition with the specific geography of the southern coastline of Australia was the primary cladogenic driver in this clam lineage. Additional in‐depth studies of the endemic southern Australian marine biota across all three provinces are needed to establish the generality of this proposed older framework for regional cladogenesis. 相似文献