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YANG CHEN JAMES T. RANDERSON GUIDO R. VAN DER WERF DOUGLAS C. MORTON MINGQUAN MU PRASAD S. KASIBHATLA 《Global Change Biology》2010,16(7):2024-2038
We used satellite‐derived estimates of global fire emissions and a chemical transport model to estimate atmospheric nitrogen (N) fluxes from savanna and deforestation fires in tropical ecosystems. N emissions and reactive N deposition led to a net transport of N equatorward, from savannas and areas undergoing deforestation to tropical forests. Deposition of fire‐emitted N in savannas was only 26% of emissions – indicating a net export from this biome. On average, net N loss from fires (the sum of emissions and deposition) was equivalent to approximately 22% of biological N fixation (BNF) in savannas (4.0 kg N ha?1 yr?1) and 38% of BNF in ecosystems at the deforestation frontier (9.3 kg N ha?1 yr?1). Net N gains from fires occurred in interior tropical forests at a rate equivalent to 3% of their BNF (0.8 kg N ha?1 yr?1). This percentage was highest for African tropical forests in the Congo Basin (15%; 3.4 kg N ha?1 yr?1) owing to equatorward transport from frequently burning savannas north and south of the basin. These results provide evidence for cross‐biome atmospheric fluxes of N that may help to sustain productivity in some tropical forest ecosystems on millennial timescales. Anthropogenic fires associated with slash and burn agriculture and deforestation in the southern part of the Amazon Basin and across Southeast Asia have substantially increased N deposition in these regions in recent decades and may contribute to increased rates of carbon accumulation in secondary forests and other N‐limited ecosystems. 相似文献
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WOUTER HOLLEMAN SOPHIE VON DER HEYDEN GUIDO ZSILAVECZ 《Zoological Journal of the Linnean Society》2012,166(4):827-853
The Clinus superciliosus complex comprises six closely related species. Three of the species were originally recognized by Gilchrist and Thompson as two distinct species, Clinus superciliosus (Linnaeus, 1758) and Clinus ornatus Gilchrist & Thompson, 1908, and a variety, Clinus superciliosus var. arborescens Gilchrist & Thompson, 1908. A number of other authors described various similar species, which subsequently were all synonymized with Clinus superciliosus. A further species, Clinus spatulatus Bennett, 1983, an obligate estuarine dweller, is known only from the Bot, Kleinmond, and Klein river estuaries in the Western Cape, South Africa. Two further species, Clinus musaicus sp. nov. (discovered while searching for C. ornatus specimens) and Clinus exasperatus sp. nov. , are herein described: the first is currently known from False Bay and the west coast of the Cape Peninsula, whereas the second species is known from only two specimens just east of False Bay. Clinus ornatus and Clinus arborescens Gilchrist & Thompson, 1908 are recognized as a valid species, and can be distinguished from C. superciliosus and C. spatulatus on the basis of meristic values, form of the orbital cirrus, position of the dorsal‐fin crest, taste bud number and pattern, diet, and coloration. All extant types of C. superciliosus are examined as specimens, or photographs and radiographs, and their validity and identification are assessed. Genetic analysis of mitochondrial and nuclear DNA supports species differentiation. A key is provided for the species complex. Furthermore, the variable coloration of four of the species, probably related to the substrate the larvae settle upon, and the increase in the number of vertebrae, and fin‐ray and spine number, with decreasing water temperature is discussed. © 2012 The Linnean Society of London, Zoological Journal of the Linnean Society 2012, 166 , 827–853. 相似文献
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RALF AURAHS GUIDO W. GRIMM‡ VERA HEMLEBEN† CHRISTOPH HEMLEBEN MICHAL KUCERA 《Molecular ecology》2009,18(8):1692-1706
We present SSU rDNA data resolving the seasonal and geographical distribution of 'cryptic' genetic types of the planktonic foraminifer morphospecies Globigerinoides ruber in the eastern Atlantic Ocean and the Mediterranean Sea. Analysis of 262 sequences revealed the presence of five genetic types belonging to two distinct lineages. Although the morphospecies G. ruber occurs throughout the investigated region, its constituent 'cryptic' genetic types show a pattern of widespread exclusion, which is difficult to reconcile with the concept of ubiquitous dispersal. One of the newly discovered genetic types was exclusively found at stations in the Mediterranean Sea, possibly representing the smallest-scale example of endemism known in planktonic foraminifera. In general, our results suggest that the geographical scale of mutual exclusion between the genotypes is negatively correlated with their phylogenetic relatedness: the most similar and most recently diverged pair of siblings showed the strongest evidence for small-scale competitive exclusion. This pattern is consistent with the concept of niche partitioning, implying decreasing level of competition between genetic types with increasing degree of genetic divergence. 相似文献
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GWENNAN E. HUGHES EMILY OWEN GUIDO STERK JEFFREY S. BALE 《Physiological Entomology》2010,35(4):373-378
Adult parasitoids Lysiphlebus testaceipes Cresson (Hymenoptera: Aphidiidae) lose locomotory function and enter chill coma at significantly lower temperatures (?0.1 and ?8.0 °C, respectively) than their second‐instar hosts, the black bean aphid Aphis fabae Scop. (Hemiptera: Aphididae) (5.6 and 2.3 °C, respectively). Parasitoids are also more heat tolerant, stop walking at 41.4 °C, with heat coma at 44.1 °C, than the aphid (39.1 and 43.0 °C, respectively). Furthermore, across a range of temperatures (0–20 °C), L. testaceipes has considerably faster walking speeds than A. fabae. These data are discussed in relation to the climatic conditions under which L. testaceipes would be an effective control agent, and the likelihood of establishment and spread in northern European climates. 相似文献
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TAMAR KEASAR ALLY R. HARARI GUIDO SABATINELLI DENIS KEITH AMOTS DAFNI OFRIT SHAVIT ASAPH ZYLBERTAL AVI SHMIDA 《Biological journal of the Linnean Society. Linnean Society of London》2010,99(4):808-817
Several species of glaphyrid (Scarabaeoidea: Glaphyridae) beetles forage and mate on Mediterranean red bowl‐shaped flowers. In red anemones and poppies in Israel, female beetles occupy only a subset of the flowers, do not aggregate, and are hidden below the petals. This raises the question of how males find their mates. In the present study, we investigated the hypothesis that males and females orient to similar plant‐generated cues, thereby increasing their mate encounter prospects. Previous studies have demonstrated that beetle attraction to red models increases with display area. Choice tests with flowers and with models indicate that both male and female beetles prefer large displays. In anemones, beetles rest, feed, and mate mainly on male‐phase flowers, which are larger than female‐phase flowers. Poppies that contain beetles are larger than the population average. These findings support the hypothesis that males and females meet by orienting to large red displays. Corolla size correlates with pollen reward in both plant species, suggesting that visits to large flowers also yield foraging benefits. Male beetles often jump rapidly among adjacent flowers. By contrast to the preference for large flowers by stationary individuals, these jump sequences are random with respect to flower sex‐phase (in anemone) and size (in poppy). They may enable males to detect females at close range. We hypothesize that males employ a mixed mate‐searching strategy, combining orientation to floral signals and to female‐produced cues. The glaphyrids' preference for large flowers may have selected for extraordinarily large displays within the ‘red anemone’ pollination guild of the Levant. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 99 , 808–817. 相似文献
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GALASSO INCORONATA; SONNANTE GABRIELLA; TOTA DONATO GUIDO; PIGNONE DOMENICO 《Annals of botany》1997,79(3):311-317
InVicia benghalensis two different biotypes, named A and B,had been observed which differed for several cytological, geneticaland biochemical characters. In the present study 27 accessionsof this species belonging to the two biotypes were investigatedusing different molecular analyses, supported by an attemptto produce hybrids between selected accessions. RAPD fingerprintingof the 27 accessions demonstrated that accessions belongingto biotype A show a high degree of genetic similarity, whilethe opposite is true for the accessions of biotype B. The totalgenomic DNA from one reference accession was used as a probeto Southern blots of the DNA extracted from all the accessionsin use. This analysis demonstrated that cross hybridizationamong the DNA of the two biotypes occurs only to a limited extent.The chromosomal localization of 18S-5.8S-25S and 5S rRNA geneclusters was determined byin situ hybridization. The resultsindicate that the two biotypes differ in the position of oneof the 5S rRNA gene clusters. This indicates a major chromosomalrearrangement. Cell synchronization experiments on two referenceaccessions suggested that the two biotypes might differ in theduration of the single phases of the cell cycle. Finally, incrossing experiments three pods were obtained which developedfor only a few days and proved to bear no viable seeds. Theseresults confirm the existence of two divergent gene-pools anddemonstrate the reproductive barrier between the two biotypes,thus suggesting the possibility of a specific ranking. Vicia benghalensis L.; genetic differentiation; in situ hybridization; Southern hybridization; crosses; RAPDs; cell synchronization 相似文献
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This study reports the development and characterization of 20 microsatellite primer pairs in wild strawberry Fragaria vesca. One hundred primers were obtained from an AC‐enriched library developed in the cultivar ‘Ilaria’. A set of eight F. vesca genotypes was used to detect the polymorphism resulting in an average of 7.0 alleles, an average observed heterozygosity of 0.32 and an average expected heterozygosity of 0.73. Nineteen (95%) of the primers also amplified the cultivated octoploid strawberry Fragaria×ananassa. 相似文献
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Enzyme electrophoresis was used to study population geneticsand molecular differentiation of European Anodontmae. The existenceof two genera (Anodonta Lamarck 1799 and Pseudanodonta Bour-guignat1876) is supported by the number of diagnostic loa (4) and Net'sD > 0.463 in all cases. In western and central Europe thereare two species of Anodonta, A. anatina (Linnaeus 1758) andA cygnea (Linnaeus 1758) while two other taxa of still uncertainrank were identified in the Mediterranean area. An estimatedmedium level of gene flow and pronounced genetic differentiationbetween-the taxa support this view. Data on genetic distancessuggest that the diversification of European Anodontinae tookplace in the middle-late Pleistocene (Received 15 August 1995; accepted 5 February 1996) 相似文献