Open AccessArticle
Species Richness, Taxonomic Distinctness and Environmental Influences on Euphausiid Zoogeography in the Indian Ocean
Diversity 2017, 9(2), 23; doi:10.3390/d9020023 -
Abstract
Although two thirds of the world’s euphausiid species occur in the Indian Ocean, environmental factors influencing patterns in their diversity across this atypical ocean basin are poorly known. Distribution data for 56 species of euphausiids were extracted from existing literature and, using a
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Although two thirds of the world’s euphausiid species occur in the Indian Ocean, environmental factors influencing patterns in their diversity across this atypical ocean basin are poorly known. Distribution data for 56 species of euphausiids were extracted from existing literature and, using a geographic information system, spatially-explicit layers of species richness and average taxonomic distinctness (AveTD) were produced for the Indian Ocean. Species richness was high in tropical areas of the southern Indian Ocean (0–20° S), and this high richness extended southwards via the Agulhas and Leeuwin boundary currents. In contrast, the land-locked northern Indian Ocean exhibited lower species richness but higher AveTD, with the presence of the monotypic family Bentheuphausiidae strongly influencing the latter result. Generalised additive modelling incorporating environmental variables averaged over 0–300 m depth indicated that low oxygen concentrations and reduced salinity in the northern Indian Ocean correlated with low species richness. Depth-averaged temperature and surface chlorophyll a concentration were also significant in explaining some of the variation in species richness of euphausiids. Overall, this study has indicated that the patterns in species richness in the Indian Ocean are reflective of its many unusual oceanographic features, and that patterns in AveTD were not particularly informative because of the dominance by the family Euphausiidae. Full article
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Open AccessArticle
The Significance of New Records of Benthic Red Algae (Rhodophyta) for Hainan Island (and China) between 1990 and 2016
Diversity 2017, 9(2), 24; doi:10.3390/d9020024 -
Abstract
We present an annotated list of new finds of red algae from Hainan Island, Southern China, including those found in 1990 and 1992 during the German-Chinese expeditions to Hainan Island and in 2008–2016 by Titlyanova, Titlyanov, and Li. Between 1990 and 1992, a
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We present an annotated list of new finds of red algae from Hainan Island, Southern China, including those found in 1990 and 1992 during the German-Chinese expeditions to Hainan Island and in 2008–2016 by Titlyanova, Titlyanov, and Li. Between 1990 and 1992, a total of 64 taxa of red algae were newly recorded for Hainan Island. Of these 15 species were new records for China. During the period 2008–2016, a further 54 taxa were newly recorded for Hainan Island, of which 20 were new records for China. The full list of new taxa includes taxonomic forms, dates, and locales, together with known biogeographical distributions. During both periods, the apparent enrichment of red algal marine flora has occurred in a similar way—mainly at the expense of epiphytes with filamentous, thin-filamentous, and finely branched forms. We believe that the changes in the flora of Hainan Island have been influenced by both anthropogenic and natural factors including in particular exploitation of herbivores, nutrient pollution, and coral bleaching. Full article
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Open AccessOpinion
Persistent Gaps of Knowledge for Naming and Distinguishing Multiple Species of Crown-of-Thorns-Seastar in the Acanthaster planci Species Complex
Diversity 2017, 9(2), 22; doi:10.3390/d9020022 -
Abstract
Nearly a decade ago, DNA barcoding (partial mitochondrial COI gene sequences) showed that there are at least four species in the Indo-Pacific within what was previously conceived to be a single Crown-of-Thorns-Seastar (COTS) species, Acanthaster planci. Two of these species—A. planci
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Nearly a decade ago, DNA barcoding (partial mitochondrial COI gene sequences) showed that there are at least four species in the Indo-Pacific within what was previously conceived to be a single Crown-of-Thorns-Seastar (COTS) species, Acanthaster planci. Two of these species—A. planci Linnaeus, 1758, distributed in the North Indian Ocean, and A. mauritiensis de Loriol, 1885, distributed in the South Indian Ocean—have been already unequivocally named. In contrast, the Pacific COTS (proposed name: A. solaris (Schreber, 1795) and the COTS from the Red Sea (still to be named) require further taxonomic work. COI barcoding sequences and Barcode Identification Numbers (BINs) are available for all four COTS species in the global Barcode of Life Database (BOLD). We recommend depositing voucher specimens or tissue samples suitable for DNA analyses when studying any aspect of COTS, and use BINs to identify species, to ensure that no information is lost on species allocation until unequivocal Linnean names are available for the Pacific and Red Sea species as well. We also review the differences between COTS species with respect to morphology, ecology, and toxicity. Future studies should widen the current biogeographic coverage of the different COTS species by strategically sampling neglected areas, especially at the geographic distribution limits of each species, to enhance our understanding of the diversity of this reef coral predator. Full article
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Open AccessReview
Barley Developmental Mutants: The High Road to Understand the Cereal Spike Morphology
Diversity 2017, 9(2), 21; doi:10.3390/d9020021 -
Abstract
A better understanding of the developmental plan of a cereal spike is of relevance when designing the plant for the future, in which innovative traits can be implemented through pre-breeding strategies. Barley developmental mutants can be a Mendelian solution for identifying genes controlling
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A better understanding of the developmental plan of a cereal spike is of relevance when designing the plant for the future, in which innovative traits can be implemented through pre-breeding strategies. Barley developmental mutants can be a Mendelian solution for identifying genes controlling key steps in the establishment of the spike morphology. Among cereals, barley (Hordeum vulgare L.) is one of the best investigated crop plants and is a model species for the Triticeae tribe, thanks to several characteristics, including, among others, its adaptability to a wide range of environments, its diploid genome, and its self-pollinating mating system, as well as the availability of its genome sequence and a wide array of genomic resources. Among them, large collections of natural and induced mutants have been developed since the 1920s, with the aim of understanding developmental and physiological processes and exploiting mutation breeding in crop improvement. The collections are not only comprehensive in terms of single Mendelian spike mutants, but with regards to double and triple mutants derived from crosses between simple mutants, as well as near isogenic lines (NILs) that are useful for genetic studies. In recent years the integration of the most advanced omic technologies with historical mutation-genetics research has helped in the isolation and validation of some of the genes involved in spike development. New interrogatives have raised the question about how the behavior of a single developmental gene in different genetic backgrounds can help in understanding phenomena like expressivity, penetrance, phenotypic plasticity, and instability. In this paper, some genetic and epigenetic studies on this topic are reviewed. Full article
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Open AccessArticle
The Phylogeny and Biogeography of Phyla nodiflora (Verbenaceae) Reveals Native and Invasive Lineages throughout the World
Diversity 2017, 9(2), 20; doi:10.3390/d9020020 -
Abstract
Phyla nodiflora is an herbaceous perennial and an enigmatic species. It is indigenous to the Americas but is considered a natural component of the flora in many areas and a weed in others. Our aim was to circumscribe the native range of P.
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Phyla nodiflora is an herbaceous perennial and an enigmatic species. It is indigenous to the Americas but is considered a natural component of the flora in many areas and a weed in others. Our aim was to circumscribe the native range of P. nodiflora, to explore dispersal mechanisms and routes and to test the hypothesis that P. nodiflora is native outside of the Americas. Determining whether distributions are natural or human-induced has implications for decisions regarding weed control or conservation. We undertook phylogenetic analyses using sequence variation in nuclear DNA marker ITS (Internal Transcribed Spacer) for a global sample of 160 populations of P. nodiflora sourced from Asia, Australia, central America, the Mediterranean, southern North America, South America and Africa. Analyses included maximum likelihood, maximum parsimony, a Bayesian estimation of phylogeny and a parsimony network analysis which provided a genealogical reconstruction of ribotypes. We evaluated phylogenies against extensive historical and biogeographical data. Based on the sequences, 64 ribotypes were identified worldwide within P. nodiflora and considerable geographic structure was evident with five clades: one unsupported and the remaining weakly supported (bootstrap support ranging from 52% to 71%). Populations from central and southern North America formed the core area in the indigenous range and we have detected at least three native lineages outside of this range. Within Australia P. nodiflora is represented by at least one native lineage and several post-European introductions. Phyla nodiflora is one of the few species in the family Verbenaceae to have a pan-tropical native distribution, probably resulting from natural dispersal from America to Africa then to Australasia. However, it has also undergone human-mediated dispersal, which has obscured the native-origin of some ribotypes. These introductions present a risk of diluting the pan-tropical structure evident in this species and therefore they have important conservation implications. Full article
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Open AccessArticle
Molecular Assisted Identification Reveals Hidden Red Algae Diversity from the Burica Peninsula, Pacific Panama
Diversity 2017, 9(2), 19; doi:10.3390/d9020019 -
Abstract
The marine flora of Panama harbors a rich diversity of green, red and brown algae, and despite chronic understudy, it is reported as the second most diverse marine flora along the Pacific Central American coast, with 174 macroalgal species. Extensive new collections and
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The marine flora of Panama harbors a rich diversity of green, red and brown algae, and despite chronic understudy, it is reported as the second most diverse marine flora along the Pacific Central American coast, with 174 macroalgal species. Extensive new collections and molecular assisted identification (MAI) by an international team of researchers has revealed an even greater diversity for this country. Here, the intertidal and shallow subtidal marine flora of the remote Burica Peninsula is introduced. This area is characterized by an uplifted extensive intertidal flat composed of firm, sedimentary benthos known as mudrock, on which abundant algal communities thrive, even during extended periods of exposure. A collection of nearly 200 brown, green and red macroalgae specimens representing the first marine floristic inventory of this region was made in January 2011, and results of analyses of 45 foliose red algae specimens are presented. DNA sequence data for several loci (rbcL-3P; COI-5P; UPA) have been generated for molecular assisted identification and to guide morphological assessments. Twenty-six species were identified among the specimens including 21 new Pacific Panama records, as well as previously unrealized transisthmian distributions, and two new species, Neorubra parvolacertoides sp. nov. and Grateloupia irregularis sp. nov. Full article
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Open AccessFeature PaperArticle
Age and Growth of An Outbreaking Acanthaster cf. solaris Population within the Great Barrier Reef
Diversity 2017, 9(1), 18; doi:10.3390/d9010018 -
Abstract
Despite having been studied for more than 40 years, much about the basic life history of crown-of-thorns starfish (CoTS; Acanthaster spp.) remains poorly understood. Size at age—a key metric of productivity for any animal population—has yet to be clearly defined, primarily due to
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Despite having been studied for more than 40 years, much about the basic life history of crown-of-thorns starfish (CoTS; Acanthaster spp.) remains poorly understood. Size at age—a key metric of productivity for any animal population—has yet to be clearly defined, primarily due to difficulties in obtaining validated ages and potentially indeterminate growth due to factors such as starvation; within-population variability is entirely unknown. Here we develop age and growth estimates for an outbreaking CoTS population in Australian waters by integrating prior information with data from CoTS collected from multiple outbreaking reefs. Age estimates were made from un-validated band counts of 2038 individual starfish. Results from our three-parameter von Bertalanffy Bayesian hierarchical model show that, under 2013–2014 outbreak conditions, CoTS on the GBR grew to a 349 (326, 380) mm (posterior median (95% uncertainty interval)) total diameter at a 0.54 (0.43, 0.66) intrinsic rate of increase. However, we also found substantial evidence (ΔDIC > 200) for inter-reef variability in both maximum size (SD 38 (19, 76)) and intrinsic rate of increase (SD 0.32 (0.20, 0.49)) within the CoTS outbreak initiation area. These results suggest that CoTS demography can vary widely with reef-scale environmental conditions, supporting location-based mechanisms for CoTS outbreaks generally. These findings should help improve population and metapopulation models of CoTS dynamics and better predict the potential damage they may cause in the future. Full article
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Open AccessReview
Potential Enhanced Survivorship of Crown of Thorns Starfish Larvae due to Near-Annual Nutrient Enrichment during Secondary Outbreaks on the Central Mid-Shelf of the Great Barrier Reef, Australia
Diversity 2017, 9(1), 17; doi:10.3390/d9010017 -
Abstract
The Great Barrier Reef (GBR) is currently experiencing widespread crown of thorns starfish (CoTS) outbreaks, as part of the fourth wave of outbreaks since 1962. It is believed that these outbreaks have become more frequent on the GBR and elsewhere in the Indo-Pacific
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The Great Barrier Reef (GBR) is currently experiencing widespread crown of thorns starfish (CoTS) outbreaks, as part of the fourth wave of outbreaks since 1962. It is believed that these outbreaks have become more frequent on the GBR and elsewhere in the Indo-Pacific and are associated with anthropogenic causes. The two widely accepted potential causes are (1) anthropogenic nutrient enrichment leading to the increased biomass of phytoplankton, the food of the planktonic stage of larval CoTS; and (2) the overfishing of predators in the juvenile to adult stages of CoTS, for example, commercially fished species such as coral trout. In this study, we show that the evidence for the nutrient enrichment causation hypothesis is strongly based on a large number of recent studies in the GBR. We also hypothesise that secondary outbreaks in the region between Cairns and Townsville can also be enhanced by nutrient enriched conditions associated with the annual nutrient discharge from Wet Tropics rivers. Full article
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Open AccessArticle
Microsatellites Reveal Genetic Homogeneity among Outbreak Populations of Crown-of-Thorns Starfish (Acanthaster cf. solaris) on Australia’s Great Barrier Reef
Diversity 2017, 9(1), 16; doi:10.3390/d9010016 -
Abstract
Specific patterns in the initiation and spread of reef-wide outbreaks of crown-of-thorns starfish are important, both to understand potential causes (or triggers) of outbreaks and to develop more effective and highly targeted management and containment responses. Using analyses of genetic diversity and structure
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Specific patterns in the initiation and spread of reef-wide outbreaks of crown-of-thorns starfish are important, both to understand potential causes (or triggers) of outbreaks and to develop more effective and highly targeted management and containment responses. Using analyses of genetic diversity and structure (based on 17 microsatellite loci), this study attempted to resolve the specific origin for recent outbreaks of crown-of-thorns on Australia’s Great Barrier Reef (GBR). We assessed the genetic structure amongst 2705 starfish collected from 13 coral reefs in four regions that spanned ~1000 km of the GBR. Our results indicate that populations sampled across the full length of the GBR are genetically homogeneous (G’ST = −0.001; p = 0.948) with no apparent genetic structure between regions. Approximate Bayesian computational analyses suggest that all sampled populations had a common origin and that current outbreaking populations of crown-of-thorns starfish (CoTS) in the Swains are not independent of outbreak populations in the northern GBR. Despite hierarchical sampling and large numbers of CoTS genotyped from individual reefs and regions, limited genetic structure meant we were unable to determine a putative source population for the current outbreak of CoTS on the GBR. The very high genetic homogeneity of sampled populations and limited evidence of inbreeding indicate rapid expansion in population size from multiple, undifferentiated latent populations. Full article
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Open AccessArticle
Interactive Effects of Endogenous and Exogenous Nutrition on Larval Development for Crown-Of-Thorns Starfish
Diversity 2017, 9(1), 15; doi:10.3390/d9010015 -
Abstract
Outbreaks of crown-of-thorns starfish are often attributed to step-changes in larval survivorship following anomalous increases in nutrients and food availability. However, larval growth and development is also influenced by the nutritional condition of spawning females, such that maternal provisioning may offset limitations imposed
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Outbreaks of crown-of-thorns starfish are often attributed to step-changes in larval survivorship following anomalous increases in nutrients and food availability. However, larval growth and development is also influenced by the nutritional condition of spawning females, such that maternal provisioning may offset limitations imposed by limited access to exogenous sources of nutrients during the formative stages of larval development. This study examined the individual, additive, and interactive effects of endogenous (maternal diet: Acropora, Porites, mixed, and starved) and exogenous (larval diet: high concentration at 104 cells·mL−1, low concentration at 103 algal cells·mL−1, and starved) nutrition on the survival, growth, morphology, and development of larvae of the crown-of-thorns starfish. Female starfish on Acropora and mixed diet produced bigger oocytes compared to Porites-fed and starved treatments. Using oocyte size as a proxy for maternal provisioning, endogenous reserves in the oocyte had a strong influence on initial larval survival and development. This suggests that maternal reserves can delay the onset of obligate exogenous food acquisition and allow larvae to endure prolonged periods of poor environmental nutritive conditions or starvation. The influence of exogenous nutrition became more prominent in later stages, whereby none of the starved larvae reached the mid-to-late brachiolaria stage 16 days after the onset of the ability to feed. There was no significant difference in the survival, development, and competency of larvae between high and low food treatments. Under low algal food conditions, larvae compensate by increasing the length of ciliated feeding bands in relation to the maximum length and width, which improve food capture and feeding efficiency. However, the effects of endogenous nutrition persisted in the later developmental stages, as larvae from starved females were unable to develop larger feeding structures in response to food-limiting conditions. Phenotypic plasticity influenced by endogenous provisions and in response to exogenous food availability may be an important strategy in boosting the reproductive success of crown-of-thorns starfish, leading to population outbreaks. Full article
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Open AccessArticle
Phenotyping, Genotyping, and Selections within Italian Local Landraces of Romanesco Globe Artichoke
Diversity 2017, 9(1), 14; doi:10.3390/d9010014 -
Abstract
Ten Italian globe artichoke clones belonging to the Romanesco typology were characterized in the western coastal area of Italy (Cerveteri, Rome), using a combination of morphological (UPOV descriptors), biochemical (HPLC analysis), and molecular (AFLP, ISSR, and SSR markers) traits. Significant differences among clones
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Ten Italian globe artichoke clones belonging to the Romanesco typology were characterized in the western coastal area of Italy (Cerveteri, Rome), using a combination of morphological (UPOV descriptors), biochemical (HPLC analysis), and molecular (AFLP, ISSR, and SSR markers) traits. Significant differences among clones were found for many of the quantitative and qualitative morphological traits. Multivariate analyses (Principal Component Analysis) showed that, of the 47 morphological descriptors assessed, four (i.e., plant height, central flower-head weight, earliness, and total flower-head weight) presented a clear grouping of the clones. Biochemical analyses showed that the clones significantly differed in the polyphenolic profiles of the flower-head, with the suggestion that some of these, such as S2, S3, S5, and S18, are more suitable for the fresh market. The clones, clustered by a UPGMA dendrogram based on 393 polymorphic AFLP and ISSR loci, showed that the clones were genetically separated from each other. This highlights the importance of characterizing, evaluating, and conserving autochthonous germplasm for future plant breeding activities. Overall, these studies resulted in the identification of two new clones, selected on the basis of flower-head morphology and earliness. These clones, named Michelangelo and Raffaello, are registered on the Italian National Register of Varieties (DM n. 6135, 3/29/2013 G.U. 91, 18 April 2013). Full article
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Open AccessArticle
The Effects of Salinity and pH on Fertilization, Early Development, and Hatching in the Crown-of-Thorns Seastar
Diversity 2017, 9(1), 13; doi:10.3390/d9010013 -
Abstract
Understanding the influence of environmental factors on the development and dispersal of crown-of-thorns seastars is critical to predicting when and where outbreaks of these coral-eating seastars will occur. Outbreaks of crown-of-thorns seastars are hypothesized to be driven by terrestrial runoff events that increase
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Understanding the influence of environmental factors on the development and dispersal of crown-of-thorns seastars is critical to predicting when and where outbreaks of these coral-eating seastars will occur. Outbreaks of crown-of-thorns seastars are hypothesized to be driven by terrestrial runoff events that increase nutrients and the phytoplankton food for the larvae. In addition to increasing larval food supply, terrestrial runoff may also reduce salinity in the waters where seastars develop. We investigated the effects of reduced salinity on the fertilization and early development of seastars. We also tested the interactive effects of reduced salinity and reduced pH on the hatching of crown-of-thorns seastars. Overall, we found that reduced salinity has strong negative effects on fertilization and early development, as shown in other echinoderm species. We also found that reduced salinity delays hatching, but that reduced pH, in isolation or in combination with lower salinity, had no detectable effects on this developmental milestone. Models that assess the positive effects of terrestrial runoff on the development of crown-of-thorns seastars should also consider the strong negative effects of lower salinity on early development including lower levels of fertilization, increased frequency of abnormal development, and delayed time to hatching. Full article
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Open AccessArticle
Variation in Incidence and Severity of Injuries among Crown-of-Thorns Starfish (Acanthaster cf. solaris) on Australia’s Great Barrier Reef
Diversity 2017, 9(1), 12; doi:10.3390/d9010012 -
Abstract
Despite the presence of numerous sharp poisonous spines, adult crown-of-thorns starfish (CoTS) are vulnerable to predation, though the importance and rates of predation are generally unknown. This study explores variation in the incidence and severity of injuries for Acanthaster cf. solaris from Australia’s
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Despite the presence of numerous sharp poisonous spines, adult crown-of-thorns starfish (CoTS) are vulnerable to predation, though the importance and rates of predation are generally unknown. This study explores variation in the incidence and severity of injuries for Acanthaster cf. solaris from Australia’s Great Barrier Reef. The major cause of such injuries is presumed to be sub-lethal predation such that the incidence of injuries may provide a proxy for overall predation and mortality rates. A total of 3846 Acanthaster cf. solaris were sampled across 19 reefs, of which 1955 (50.83%) were injured. Both the incidence and severity of injuries decreased with increasing body size. For small CoTS (<125 mm total diameter) >60% of individuals had injuries, and a mean 20.7% of arms (±2.9 SE) were affected. By comparison, <30% of large (>450 mm total diameter) CoTS had injuries, and, among those, only 8.3% of arms (±1.7 SE) were injured. The incidence of injuries varied greatly among reefs but was unaffected by the regulations of local fisheries. Full article
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Open AccessReview
Diversity of the Mountain Flora of Central Asia with Emphasis on Alkaloid-Producing Plants
Diversity 2017, 9(1), 11; doi:10.3390/d9010011 -
Abstract
The mountains of Central Asia with 70 large and small mountain ranges represent species-rich plant biodiversity hotspots. Major mountains include Saur, Tarbagatai, Dzungarian Alatau, Tien Shan, Pamir-Alai and Kopet Dag. Because a range of altitudinal belts exists, the region is characterized by high
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The mountains of Central Asia with 70 large and small mountain ranges represent species-rich plant biodiversity hotspots. Major mountains include Saur, Tarbagatai, Dzungarian Alatau, Tien Shan, Pamir-Alai and Kopet Dag. Because a range of altitudinal belts exists, the region is characterized by high biological diversity at ecosystem, species and population levels. In addition, the contact between Asian and Mediterranean flora in Central Asia has created unique plant communities. More than 8100 plant species have been recorded for the territory of Central Asia; about 5000–6000 of them grow in the mountains. The aim of this review is to summarize all the available data from 1930 to date on alkaloid-containing plants of the Central Asian mountains. In Saur 301 of a total of 661 species, in Tarbagatai 487 out of 1195, in Dzungarian Alatau 699 out of 1080, in Tien Shan 1177 out of 3251, in Pamir-Alai 1165 out of 3422 and in Kopet Dag 438 out of 1942 species produce alkaloids. The review also tabulates the individual alkaloids which were detected in the plants from the Central Asian mountains. Quite a large number of the mountain plants produce neurotoxic and cytotoxic alkaloids, indicating that a strong chemical defense is needed under the adverse environmental conditions of these mountains with presumably high pressure from herbivores. Full article
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Open AccessArticle
Environmental Tipping Points for Sperm Motility, Fertilization, and Embryonic Development in the Crown-of-Thorns Starfish
Diversity 2017, 9(1), 10; doi:10.3390/d9010010 -
Abstract
For broadcast spawning invertebrates such as the crown-of-thorns starfish, early life history stages (from spawning to settlement) may be exposed to a wide range of environmental conditions, and could have a major bearing on reproductive success and population replenishment. Arrested development in response
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For broadcast spawning invertebrates such as the crown-of-thorns starfish, early life history stages (from spawning to settlement) may be exposed to a wide range of environmental conditions, and could have a major bearing on reproductive success and population replenishment. Arrested development in response to multiple environmental stressors at the earliest stages can be used to define lower and upper limits for normal development. Here, we compared sperm swimming speeds and proportion of motile sperm and rates of fertilization and early development under a range of environmental variables (temperature: 20–36 °C, salinity: 20–34 psu, and pH: 7.4–8.2) to identify environmental tipping points and thresholds for reproductive success. We also tested the effects of water-soluble compounds, derived from eggs, on sperm activity. Our results demonstrate that gametes, fertilization, and embryonic development are robust to a wide range of temperature, salinity, and pH levels that are outside the range found at the geographical limits of adult distribution and can tolerate environmental conditions that exceed expected anomalies as a result of climate change. Water-soluble compounds derived from eggs also enhanced sperm activity, particularly in environmental conditions where sperm motility was initially limited. These findings suggest that fertilization and embryonic development of crown-of-thorns starfish are tolerant to a wide range of environmental conditions, though environmental constraints on recruitment success may occur at later ontogenic stages. Full article
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Open AccessReview
Potential Population Genetic Consequences of Habitat Fragmentation in Central European Forest Trees and Associated Understorey Species—An Introductory Survey
Diversity 2017, 9(1), 9; doi:10.3390/d9010009 -
Abstract
Habitat fragmentation threatens the maintenance of genetic diversity of affected populations. Assessment of the risks associated with habitat fragmentation is a big challenge as the change in population genetic diversity is a dynamic process, often acting over long time periods and depending on
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Habitat fragmentation threatens the maintenance of genetic diversity of affected populations. Assessment of the risks associated with habitat fragmentation is a big challenge as the change in population genetic diversity is a dynamic process, often acting over long time periods and depending on various characteristics pertaining to both species (life history traits) and their populations (extrinsic characteristics). With this survey, we provide an introductory overview for persons who have to make or are interested in making predictions about the fate of forest-dwelling plant populations which have recently become fragmented and isolated from their main occurrences. We provide a concise introduction to the field of population genetics focusing on terms, processes and phenomena relevant to the maintenance of genetic diversity and vitality of plant populations. In particular the antagonistic effects of gene flow and random genetic drift are covered. A special chapter is devoted to Central European tree species (including the Carpathians) which we treat in detail with reference to an extensive literature survey on population genetic studies assembled from the whole of Europe. We further provide an overview of the population biology of associated understorey species. We conclude with recommended steps to be taken for the evaluation of potential perils of habitat fragmentation or population thinning for the genetics of tree populations. The complexity of effects exerted by life history traits and extrinsic characteristics of populations suggest population genetic development is strongly situation dependent. Therefore, we recommend following a case-by-case approach ideally supported by computer simulations to predict future population genetic development of both trees and associated understorey species. Full article
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Open AccessArticle
Selective Feeding and Microalgal Consumption Rates by Crown-Of-Thorns Seastar (Acanthaster cf. solaris) Larvae
Diversity 2017, 9(1), 8; doi:10.3390/d9010008 -
Abstract
Outbreaks of the crown-of-thorns seastar (CoTS) represent a major cause of coral loss on the Great Barrier Reef. Outbreaks can be explained by enhanced larval survival supported by higher phytoplankton availability after flood events, yet little is known about CoTS larvae feeding behaviour,
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Outbreaks of the crown-of-thorns seastar (CoTS) represent a major cause of coral loss on the Great Barrier Reef. Outbreaks can be explained by enhanced larval survival supported by higher phytoplankton availability after flood events, yet little is known about CoTS larvae feeding behaviour, in particular their potential for selective feeding. Here, single- and mixed-species feeding experiment were conducted on CoTS larvae using five algae (Phaeodactylum tricornutum, Pavlova lutheri, Tisochrysis lutea, Dunaliella sp. and Chaetoceros sp.) and two algal concentrations (1000 and 2500 algae·mL−1). Cell counts using flow-cytometry at the beginning and end of each incubation experiment allowed us to calculate the filtration and ingestion rates of each species by CoTS larvae. In line with previous studies, CoTS larvae ingested more algae when the initial algal concentration was higher. We found evidence for the selective ingestion of some species (Chaetoceros sp., Dunaliella sp.) over others (P. lutheri, P. tricornutum). The preferred algal species had the highest energy content, suggesting that CoTS selectively ingested the most energetic algae. Ultimately, combining these results with spatio-temporal patterns in phytoplankton communities will help elucidate the role of larval feeding behaviour in determining the frequency and magnitude of CoTS outbreaks. Full article
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Open AccessReview
Known Predators of Crown-of-Thorns Starfish (Acanthaster spp.) and Their Role in Mitigating, If Not Preventing, Population Outbreaks
Diversity 2017, 9(1), 7; doi:10.3390/d9010007 -
Abstract
Predatory release has long been considered a potential contributor to population outbreaks of crown-of-thorns starfish (CoTS; Acanthaster spp.). This has initiated extensive searches for potentially important predators that can consume large numbers of CoTS at high rates, which are also vulnerable to over-fishing
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Predatory release has long been considered a potential contributor to population outbreaks of crown-of-thorns starfish (CoTS; Acanthaster spp.). This has initiated extensive searches for potentially important predators that can consume large numbers of CoTS at high rates, which are also vulnerable to over-fishing or reef degradation. Herein, we review reported predators of CoTS and assess the potential for these organisms to exert significant mortality, and thereby prevent and/or moderate CoTS outbreaks. In all, 80 species of coral reef organisms (including fishes, and motile and sessile invertebrates) are reported to predate on CoTS gametes (three species), larvae (17 species), juveniles (15 species), adults (18 species) and/or opportunistically feed on injured (10 species) or moribund (42 species) individuals within reef habitats. It is clear however, that predation on early life-history stages has been understudied, and there are likely to be many more species of reef fishes and/or sessile invertebrates that readily consume CoTS gametes and/or larvae. Given the number and diversity of coral reef species that consume Acanthaster spp., most of which (e.g., Arothron pufferfishes) are not explicitly targeted by reef-based fisheries, links between overfishing and CoTS outbreaks remain equivocal. There is also no single species that appears to have a disproportionate role in regulating CoTS populations. Rather, the collective consumption of CoTS by multiple different species and at different life-history stages is likely to suppress the local abundance of CoTS, and thereby mediate the severity of outbreaks. It is possible therefore, that general degradation of reef ecosystems and corresponding declines in biodiversity and productivity, may contribute to increasing incidence or severity of outbreaks of Acanthaster spp. However, it seems unlikely that predatory release in and of itself could account for initial onset of CoTS outbreaks. In conclusion, reducing anthropogenic stressors that reduce the abundance and/or diversity of potential predatory species represents a “no regrets” management strategy, but will need to be used in conjunction with other management strategies to prevent, or reduce the occurrence, of CoTS outbreaks. Full article
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Open AccessArticle
Estimating Invasion Success by Non-Native Trees in a National Park Combining WorldView-2 Very High Resolution Satellite Data and Species Distribution Models
Diversity 2017, 9(1), 6; doi:10.3390/d9010006 -
Abstract
Invasion by non-native tree species is an environmental and societal challenge requiring predictive tools to assess invasion dynamics. The frequent scale mismatch between such tools and on-ground conservation is currently limiting invasion management. This study aimed to reduce these scale mismatches, assess the
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Invasion by non-native tree species is an environmental and societal challenge requiring predictive tools to assess invasion dynamics. The frequent scale mismatch between such tools and on-ground conservation is currently limiting invasion management. This study aimed to reduce these scale mismatches, assess the success of non-native tree invasion and determine the environmental factors associated to it. A hierarchical scaling approach combining species distribution models (SDMs) and satellite mapping at very high resolution (VHR) was developed to assess invasion by Acacia dealbata in Peneda-Gerês National Park, the only national park in Portugal. SDMs were first used to predict the climatically suitable areas for A. dealdata and satellite mapping with the random-forests classifier was then applied to WorldView-2 very-high resolution imagery to determine whether A. dealdata had actually colonized the predicted areas (invasion success). Environmental attributes (topographic, disturbance and canopy-related) differing between invaded and non-invaded vegetated areas were then analyzed. The SDM results indicated that most (67%) of the study area was climatically suitable for A. dealbata invasion. The onset of invasion was documented to 1905 and satellite mapping highlighted that 12.6% of study area was colonized. However, this species had only colonized 62.5% of the maximum potential range, although was registered within 55.6% of grid cells that were considerable unsuitable. Across these areas, the specific success rate of invasion was mostly below 40%, indicating that A. dealbata invasion was not dominant and effective management may still be possible. Environmental attributes related to topography (slope), canopy (normalized difference vegetation index (ndvi), land surface albedo) and disturbance (historical burnt area) differed between invaded and non-invaded vegetated area, suggesting that landscape attributes may alter at specific locations with Acacia invasion. Fine-scale spatial-explicit estimation of invasion success combining SDM predictions with VHR invasion mapping allowed the scale mismatch between predictions of invasion dynamics and on-ground conservation decision making for invasion management to be reduced. Locations with greater potential to suppress invasions could also be defined. Uncertainty in the invasion mapping needs to be accounted for in the interpretation of the results. Full article
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Open AccessArticle
Tracking the Recovery of Freshwater Mussel Diversity in Ontario Rivers: Evaluation of a Quadrat-Based Monitoring Protocol
Diversity 2017, 9(1), 5; doi:10.3390/d9010005 -
Abstract
Watershed inventories and population monitoring are essential components of efforts to conserve and recover freshwater mussel diversity in Canada. We used two datasets to assess the efficacy of a quadrat-based sampling protocol for: (1) detecting mussel species at risk; (2) characterizing species composition;
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Watershed inventories and population monitoring are essential components of efforts to conserve and recover freshwater mussel diversity in Canada. We used two datasets to assess the efficacy of a quadrat-based sampling protocol for: (1) detecting mussel species at risk; (2) characterizing species composition; (3) providing accurate estimates of abundance; and (4) detecting changes in density. The protocol is based on a systematic design (with random starts) that samples 20% of monitoring sites with visual-tactile surface searches and excavation of 1 m2 quadrats. The first dataset included 40 sampling sites in five Ontario rivers, and the second dataset consisted of complete census sampling at two 375 m2 sites that represented contrasting mussel assemblages. Our results show that the protocol can be expected to detect the majority of species present at a site and provide accurate and precise estimates of total mussel density. Excavation was essential for detection of small individuals and to accurately estimate abundance. However, the protocol was of limited usefulness for reliable detection of most species at risk. Furthermore, imprecise density estimates precluded detection of all but the most extreme changes in density of most individual species. Meeting monitoring objectives will require either substantially greater sampling effort under the current protocol, or a fundamental revision of the sampling approach. Full article
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