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Nichola A. Strandberg Mary Edwards Joanna C. Ellison Manuel J. Steinbauer Anna Walentowitz Patricia L. Fall David Sear Peter Langdon Shane Cronin Alvaro Castilla-Beltrán Ian W. Croudace Matiu Prebble William D. Gosling Sandra Nogué 《Biotropica》2023,55(4):816-827
Here, we investigate Mid- to Late-Holocene vegetation changes in low-lying coastal areas in Tonga and how changing sea levels and recurrent volcanic eruptions have influenced vegetation dynamics on four islands of the Tongan archipelago (South Pacific). To investigate past vegetation and environmental change at Ngofe Marsh (‘Uta Vava’u), we examined palynomorphs (pollen and spores), charcoal (fire), and sediment characteristics (volcanic activity) from a 6.7-m-long sediment core. Radiocarbon dating indicated the sediments were deposited over the last 7700 years. We integrated the Ngofe Marsh data with similar previously published data from Avai’o’vuna Swamp on Pangaimotu Island, Lotofoa Swamp on Foa Island, and Finemui Swamp on Ha’afeva Island. Plant taxa were categorized as littoral, mangrove, rainforest, successional/ disturbance, and wetland groups, and linear models were used to examine relationships between vegetation, relative sea level change, and volcanic eruptions (tephra). We found that relative sea level change has impacted vegetation on three of the four islands investigated. Volcanic eruptions were not identified as a driver of vegetation change. Rainforest decline does not appear to be driven by sea level changes or volcanic eruptions. From all sites analyzed, vegetation at Finemui Swamp was most sensitive to changes in relative sea level. While vegetation on low-lying Pacific islands is sensitive to changing sea levels, island characteristics, such as area and elevation, are also likely to be important factors that mediate specific island responses to drivers of change. 相似文献
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A wide-ranging examination of plastid (pt)DNA sequence homologies within
higher plant nuclear genomes (promiscuous DNA) was undertaken. Digestion
with methylation-sensitive restriction enzymes and Southern analysis was
used to distinguish plastid and nuclear DNA in order to assess the extent
of variability of promiscuous sequences within and between plant species.
Some species, such as Gossypium hirsutum (cotton), Nicotiana tabacum
(tobacco), and Chenopodium quinoa, showed homogenity of these sequences,
while intraspecific sequence variation was observed among different
cultivars of Pisum sativum (pea), Hordeum vulgare (barley), and Triticum
aestivum (wheat). Hypervariability of plastid sequence homologies was
identified in the nuclear genomes of Spinacea oleracea (spinach) and Beta
vulgaris (beet), in which individual plants were shown to possess a unique
spectrum of nuclear sequences with ptDNA homology. This hypervariability
apparently extended to somatic variation in B. vulgaris. No sequences with
ptDNA homology were identified by this method in the nuclear genome of
Arabidopsis thaliana.
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E. Fernando Cagua Jesse E. M. Cochran Christoph A. Rohner Clare E. M. Prebble Tane H. Sinclair-Taylor Simon J. Pierce Michael L. Berumen 《Biology letters》2015,11(4)
Although whale sharks (Rhincodon typus) have been documented to move thousands of kilometres, they are most frequently observed at a few predictable seasonal aggregation sites. The absence of sharks at the surface during visual surveys has led to the assumption that sharks disperse to places unknown during the long ‘off-seasons’ at most of these locations. Here we compare 2 years of R. typus visual sighting records from Mafia Island in Tanzania to concurrent acoustic telemetry of tagged individuals. Sightings revealed a clear seasonal pattern with a peak between October and February and no sharks observed at other times. By contrast, acoustic telemetry demonstrated year-round residency of R. typus. The sharks use a different habitat in the off-season, swimming deeper and further away from shore, presumably in response to prey distributions. This behavioural change reduces the sharks'' visibility, giving the false impression that they have left the area. We demonstrate, for the first time to our knowledge, year-round residency of unprovisioned, individual R. typus at an aggregation site, and highlight the importance of using multiple techniques to study the movement ecology of marine megafauna. 相似文献
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The effect of white light on the malate oxidase of Sarcina lutea (Micrococcus luteus) membranes has been examined using a carotenoid-containing and a carotenoidless mutant. At least three photosensitive sites have been detected. Two of these are associated with the malate dehydrogenase complex (malate-menaquinone reductase) and are unaffected by membrane carotenoid. A third site which has been detected beyond the dehydrogenase complex, is protected by carotenoid since it can only be demonstrated in carotenoidless systems. A repair mechanism has been found for one of the two sites in the dehydrogenase complex. 相似文献
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The phylogeny of Greya Busck (Lepidoptera: Prodoxidae) was inferred from
nucleotide sequence variation across a 765-bp region in the cytochrome
oxidase I and II genes of the mitochondrial genome. Most parsimonious
relationships of 25 haplotypes from 16 Greya species and two outgroup
genera (Tetragma and Prodoxus) showed substantial congruence with the
species relationships indicated by morphological variation. Differences
between mitochondrial and morphological trees were found primarily in the
positions of two species, G. variabilis and G. pectinifera, and in the
branching order of the three major species groups in the genus. Conflicts
between the data sets were examined by comparing levels of homoplasy in
characters supporting alternative hypotheses. The phylogeny of Greya
species suggests that host-plant association at the family level and larval
feeding mode are conservative characters. Transition/transversion ratios
estimated by reconstruction of nucleotide substitutions on the phylogeny
had a range of 2.0-9.3, when different subsets of the phylogeny were used.
The decline of this ratio with the increase in maximum sequence divergence
among taxa indicates that transitions are masked by transversions along
deeper internodes or long branches of the phylogeny. Among transitions,
substitutions of A-->G and T-->C outnumbered their reciprocal
substitutions by 2-6 times, presumably because of the approximately 4:1
(77%) A+T-bias in nucleotide base composition. Of all transversions,
73%-80% were A<-->T substitutions, 85% of which occurred at third
positions of codons; these estimates did not decrease with an increase in
maximum sequence divergence of taxa included in the analysis. The high
frequency of A<-->T substitutions is either a reflection or an
explanation of the 92% A+T bias at third codon positions.
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Prebble JN 《Studies in History and Philosophy of Science Part C: Studies in History and Philosophy of Biological and Biomedical Sciences》2010,41(3):253-262
The origins of oxidative phosphorylation, initially known as aerobic phosphorylation, grew out of three research areas of muscle metabolism, creatine phosphorylation, aerobic metabolism of lactic acid in muscle, and studies on the nature and role of adenosine triphosphate (ATP). Much of this work centred round the laboratory of Otto Meyerhof, and most of those contributing to the study of aerobic phosphorylation were influenced by that laboratory: particularly Lipmann and also Ochoa. The work of Engelhardt on ATP levels in blood also appears to have been influenced by the studies of Meyerhof's laboratory. However, with the work of Kalckar, influenced by Lipmann, biochemists began to realise the potential importance of the process. This was confirmed and extended by Belitzer and Ochoa and the theoretical contribution of Lipmann. Thus it is not easy to identify a single point that marked the initiation of studies in this field. The early work was based on the use of tissue homogenates and cells but ultimately this approach limited research possibilities. The development of techniques based on mitochondria opened up new possibilities and brought this first phase of the study of oxidative phorphorylation to a close. 相似文献
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Núria Cañellas-Boltà Valentí Rull Alberto Sáez Matthew Prebble Olga Margalef 《Vegetation History and Archaeobotany》2014,23(3):331-338
Easter Island, a remote island in the Pacific Ocean, is currently primarily covered by grasslands, but palaeoecological studies have shown the former presence of different vegetation. Much of its original biota has been removed during the last two millennia, most likely by human activities, and little is known about the native flora. Macrofossil and pollen analyses of a sediment core from the Raraku crater lake have revealed the occurrence of a plant that is currently extinct from the island: Dianella cf. intermedia/adenanthera (Xanthorrhoeaceae), which grew and disappeared at the Raraku site long before human arrival. The occurrence of Dianella within the Raraku sedimentary sequence (between 9.4 and 5.4 cal. kyr b.p.) could have been linked to the existence of favorable palaeoenvironmental conditions (peatland rather than the present-day lacustrine environment) during the early to mid Holocene. This finding contributes new knowledge about indigenous plant diversity on Easter Island and reinforces the usefulness of further macrofossil and pollen analyses to identify native species on Easter Island and elsewhere. 相似文献
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First phylogenetic and biogeographical study of the southern bluebells (Wahlenbergia, Campanulaceae)
Prebble JM Cupido CN Meudt HM Garnock-Jones PJ 《Molecular phylogenetics and evolution》2011,59(3):636-648
Wahlenbergia is a largely southern hemisphere genus of at least 260 species; within Campanulaceae only Campanula is larger. This first phylogeny of Wahlenbergia was reconstructed using about 20% of the 260 species in the genus based on the nuclear ribosomal ITS marker and the chloroplast trnL-F marker with samples from South Africa, Europe, Australia and New Zealand. Wahlenbergia was confirmed to be non-monophyletic, though most of the species form a clade. Our tree topology and date estimates indicate that Wahlenbergia diverged in South Africa about 29.6 mya, then dispersed to Australasia about 4.8 mya, thus indicating the radiation of Wahlenbergia occurred relatively recently. Radiations occurred in both of these main centres; there are currently about 170 species in South Africa and 45 species and subspecies in Australasia. New Zealand species comprise two clades, both rooted within the Australasian clade. We thus propose two dispersals from Australia to New Zealand, one leading to a radiation of species with the rhizomatous herbaceous growth form ca. 1.6 mya, and the other leading to a radiation of species with the radicate growth form 0.7 mya. Dispersals from Australia to New Zealand match the expected direction, following the west wind drift and ocean currents. The herbaceous growth form was shown to be ancestral for the genus as a whole, and polyploidy has been a mechanism of the evolution of the genus in Australasia. 相似文献