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11.
Unusual growth pattern in the Frasnian alveolitids (Tabulata) from the Holy Cross Mountains (Poland)
Abstract: Growth periodicity is a phenomenon occurring in fossil and modern corals. The most apparent feature is growth banding, and environmental changes are broadly accepted as controls on this phenomenon. If environment controls the growth, then all corallites within a colony should repeat the same growth pattern, as individuals are clones and must have shared the same environment. A study on several species of Alveolitidae (Anthozoa, Tabulata) from the Late Devonian (Early Frasnian) of the Holy Cross Mountains (Poland) shows that the growth pattern varies between neighbouring individuals within the same corallum. This contradicts observations of closely related Favositida as demonstrated on Pachyfavosites sp. from the Givetian of Avesnois, France, where neighbouring individuals repeat the same pattern. Therefore, environmental control on growth rhythm in Alveolitidae can be excluded; the causes of differences between individuals remain unknown. 相似文献
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SILVIA GARDIN LEOPOLD KRYSTYN SYLVAIN RICHOZ ANNACHIARA BARTOLINI BRUNO GALBRUN 《Lethaia: An International Journal of Palaeontology and Stratigraphy》2012,45(4):507-523
Gardin, S., Krystyn, L., Richoz, S., Bartolini, A. & Galbrun, B. 2012: Where and when the earliest coccolithophores? Lethaia, Vol. 45, pp. 507–523. New calcareous nannofossil analyses from the Northern Calcareous Alps of Austria are herein used to update and improve the state of knowledge about the oldest occurrence of coccolithophores reported in the literature. Previously reported Norian occurrences of coccoliths were based on an obsolete Triassic chronostratigraphy, in which the Rhaetian stage was subsumed into the Norian (‘Sevatian 2’). The oldest stratigraphical record of coccoliths spp. lies just below the Norian‐Rhaetian boundary and the first coccolith species, Crucirhabdus minutus, is recorded from the base of Rhaetian stage. The latter bio‐event is located just above the First Occurrence of the conodont Misikella posthersteni and the first occurrence of the ammonoid Paracochloceras suessi in the Steinbergkogel section (Austria), Global Stratotype Section and Point (GSSP) candidate for the Norian–Rhaetian boundary. The appearance of the coccolith Crucirhabdus minutus is seen as a robust biochronological datum that will provide useful constraints for Triassic biostratigraphy, palaeoclimatic modelling and phylogenetic reconstructions. The new calcareous nannofossil biochronology of Steinbergkogel that we present herein completes the existing biostratigraphic characterization of the Norian‐Rhaetian transition based on conodonts and ammonoids and strengthens the position of Steinbergkogel as the best GSSP proposed section for the base of the Rhaetian. The record of coccolithophores across the Norian–Rhaetian boundary at Steinbergkogel takes place along with a discernible increase in abundance of Prinsiosphaera triassica, as well as the appearance of Euconusphaera zlambachensis, which are the two most important Rhaetian pelagic carbonate producers. This succession of bio‐events is interpreted as the initiation of the pelagic carbonate production driven by the successful spreading of calcareous nannofossils in the Western Tethys during the Rhaetian. □Austria, Calcareous Alps, coccolithophores, Triassic. 相似文献
13.
Plant diversity in a managed temperate deciduous forest: understorey response to two silvicultural systems 总被引:6,自引:0,他引:6
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HEIKO SCHMALJOHANN† FELIX LIECHTI ERICH BÄCHLER THOMAS STEURI & BRUNO BRUDERER 《Ibis》2008,150(2):342-355
Besides the scientific interest in the quantification of bird migration, there is an increasing need to quantify bird movements for the assessment of bird collision risk with artificial structures. In many environmental impact studies, the radar method is used in an inappropriate manner. The processing of echoes consists often of counting blips within defined screen fields, and the surveyed volume is estimated without reference to the detection probabilities of different 'target sizes' (radar cross-sections). The aim of this paper is to present a procedure to quantify bird migration reliably using radar by stating the theoretical requirements of every single step of this procedure and presenting methodological solutions using our own radar data from extensive field studies. Our methodological solutions can be applied to various radar systems, including widely used ship radar. The procedure presented involves discriminating the echoes of birds and insects and estimating the different detection probabilities of differently 'sized' birds (radar cross-sections). By ignoring the different detection probabilities, density estimations may be wrong by as much as 400%. We fear that quantification of bird migration and predicted bird numbers affected by collisions with artificial structures are in many cases based on unreliable estimates. 相似文献
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ALAIN DEJEAN JACQUES H. C. DELABIE PHILIPPE CERDAN MARC GIBERNAU BRUNO CORBARA 《Biological journal of the Linnean Society. Linnean Society of London》2006,89(1):91-98
The present field study compared the degree of defoliation of three Guianian melastome, two myrmecophytes (i.e. plants sheltering ants in hollow structures) and Clidemia sp., a nonmyrmecophytic plant serving as a control. Maieta guianensis Aubl. hosted mostly Pheidole minutula Mayr whatever the area, whereas Tococa guianensis Aubl. hosted mostly Azteca bequaerti Wheeler along streams and Crematogaster laevis Mayr or Azteca sp. 1 in the understory where it never blossomed. Only Tococa , when sheltering A. bequaerti in what can be considered as a truly mutualistic relationship, showed significantly less defoliation than control plants. In the other associations, the difference was not significant, but P. minutula is mutualistic with Maieta because it furnishes some protection (exclusion experiments) plus nutrients (previous studies). When devoid of ants, Tococa showed significantly greater defoliation than control plants; therefore, it was deduced that Tococa probably lacks certain antidefoliator metabolites that control plants possess (both Tococa and control plants are protected by ground-nesting, plant-foraging ants, which is termed 'general myrmecological protection'). Consequently, plant-ants other than A. bequaerti probably also protect Tococa slightly, thus compensating for this deficiency and permitting it to live in the understory until treefall gaps provide the conditions necessary for seed production. © 2006 The Linnean Society of London, Biological Journal of the Linnean Society , 2006, 89 , 91–98. 相似文献
18.
MARTIJN VAN DE POL KEES OOSTERBEEK ANNE L. RUTTEN BRUNO J. ENS JOOST M. TINBERGEN & SIMON VERHULST 《Ibis》2009,151(1):171-180
Molecular sexing of birds has been possible for over a decade, but for practical reasons many studies still use biometric data for sex discrimination. In some species, the sexes are easy to distinguish but sexual dimorphism is often more subtle, requiring the use of statistical analyses of biometric measurements to discriminate sexes. These models are usually parameterized and validated using data from a limited number of sites and years. However, the resulting discriminant functions are often applied to other populations and periods. A crucial, but usually untested, assumption is that sexual dimorphism does not vary in time and space. Here we illustrate the consequences of violation of this assumption in Eurasian Oystercatchers Haematopus ostralegus , a species for which most studies have relied on biometric sexing. Using biometric data from captures of known-sex birds, we show that sexual dimorphism varied substantially in time and even reversed in some months and years. Furthermore, some biometric traits used in sexing changed gradually over time, causing a reduction in sexual dimorphism. We show that the consequences of this variation on sex discrimination in Oystercatchers are subtle and easily overlooked, but can result in inaccurate and strongly male- or female-biased sex-ratio estimates. We recommend that biometric sexing should be avoided in Oystercatchers unless specific calibration for each month, year and area is carried out. This recommendation also applies to other species where biometric traits may depend on environmental conditions. We argue that this condition might apply to many bird species and therefore advise caution when interpreting results based on biometric sex discrimination. 相似文献
19.
ERIC PARMENTIER DAVID LECCHINI BRUNO FREDERICH CHRISTOPHE BRIE DAVID MANN 《Biological journal of the Linnean Society. Linnean Society of London》2009,97(4):928-940
Most studies of fish sounds show that the sounds are species-specific, with unique spectral and timing characteristics. This raises the question as to whether these sounds can be used to understand phyletic relationships between species and which acoustic parameters are subject to variation between species. In the present study, 597 sounds (and 2540 pulses) related to signal jumps of four Dascyllus species ( Dascyllus aruanus , Dascyllus trimaculatus , Dascyllus albisella , and Dascyllus flavicaudus ) from different geographic regions (Madagascar, Moorea, Rangiroa, and Hawaii) were analysed. It was possible to discern species-specific sounds, but also variation in sounds between populations. Large variations in sound length were found between Dascyllus species, whereas differences in interpulse duration were found to be variable between populations. In the regions where species live in sympatry, it appears that they restrict the variability in their sounds. This could comprise evidence of adaptation with character displacement of sonic characteristics where different species co-occur. However, sonic characteristics still overlapped substantially between species, suggesting that females would need to sample more than one sound and potentially use other cues to discriminate between species. © 2009 The Linnean Society of London, Biological Journal of the Linnean Society , 2009, 97 , 928–940. 相似文献
20.
PASCAL MOYAL AHMET BAYRAM MATILDA SAVOPOULOU‐SOULTANI ERIC CONTI MATILDE EIZAGUIRRE BRUNO LE RÜ ARMAN AVAND‐FAGHIH BRIGITTE FRÉROT STEFANOS ANDREADIS 《Biological journal of the Linnean Society. Linnean Society of London》2011,103(4):904-922
The major pest of maize in Mediterranean Europe, the stem borer Sesamia nonagrioides (Lefèbvre) (Lepidoptera: Noctuidae), has a fragmented distribution, north and south of the Sahara. The present study aimed: (1) to clarify the uncertain taxonomic status of the Palearctic and sub‐Saharan populations which were first considered as different species and later on as subspecies (Sesamia nonagrioides nonagrioides and Sesamia nonagrioides botanephaga) and (2) to investigate the origin of the Palearctic population which extends from Spain to Iran, outside what is considered typical for this mainly tropical genus. We reconstructed the evolutionary history of both populations using one nuclear and two mitochondrial genes. The sub‐Saharan taxon was fragmented in two isolated populations (West and East) whose mitochondrial genes were distant by 2.3%. The Palearctic population was included in the East African clade and its genes were close or identical to those of a population from Central Ethiopia, where the species was discovered for the first time. Similarly, in Africa, the alleles of the nuclear gene were distributed mainly in two West and East clades, whereas some Palearctic alleles belonged to the West clade. The Palearctic population originated therefore from East and West Africa and is the progeny of the cross between these two African populations. The main species concepts were in agreement, leading to the conclusion that the three populations are still conspecific. In the surveyed regions, the species therefore does not include two subspecies but three isolated populations. The Palearctic population suffered from severe bottlenecks that resulted in the fixation of one East African mitochondrial genome and the large reduction in its genetic diversity compared to the African populations. The data suggest that natural colonization of the Palearctic region was more plausible than human introduction. The allelic distribution of the Palearctic population was similar to that of species that survived the last glaciation. It is concluded that the African populations expanded during the last interglacial, crossed the Sahara and mixed in North Africa where fixation of the East mitochondrial genome occurred. The species then colonized Europe westward through only one eastern entrance. The coalescent‐based estimate of the time to the ancestor of the Palearctic population was 108 000 years, which is consistent with this scenario. © 2011 The Linnean Society of London, Biological Journal of the Linnean Society, 2011, 103 , 904–922. 相似文献