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21.
JEANNE M. ROBERTSON KNUT HOVERSTEN MICHAEL GRÜNDLER THOMAS J. POORTEN DIANA K. HEWS ERICA BREE ROSENBLUM 《Biological journal of the Linnean Society. Linnean Society of London》2011,103(3):657-667
Colonization of novel habitats is often associated with differences in ecological community composition. For small diurnal animals, differences in predator diversity and abundance can lead to behavioural shifts in the novel habitat. The eastern fence lizard Sceloporus undulatus (Bosc and Daudin, 1801) recently colonized the gypsum dunes of White Sands, a predator‐poor community relative to the predator‐rich community of the surrounding Chihuahuan dark‐soil habitat. We used field experiments to assess S. undulatus anti‐predator behaviour in white‐sand versus dark‐soil habitats, and used laboratory assays to determine whether behavioural differences could be mediated by hormonal regulation. Overall, we found that white‐sand lizards were less vigilant but more wary than their dark‐soil counterparts; it took them longer to detect a simulated predator, but once detected they were more likely to retreat from their perches than dark‐soil lizards. At the proximate level, differences in anti‐predator behaviour could not be explained by differences in plasma hormone levels (corticosterone and testosterone); we detected elevated corticosterone for lizards in our stress treatment relative to control treatment, but found no differences between habitats in baseline or acute corticosterone levels. At the evolutionary level, we suggest that differences in anti‐predator behaviour may be explained by differences across habitats in predation environment, habituation, and/or the cost of retreating. Our study implicates changes in predator community composition in mediating ecological divergence in behaviour. © 2011 The Linnean Society of London, Biological Journal of the Linnean Society, 2011, 103 , 657–667. 相似文献
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Decline in a dominant invertebrate species contributes to altered carbon cycling in a low-diversity soil ecosystem 总被引:1,自引:0,他引:1
J. E. BARRETT ROSS A. VIRGINIA† DIANA H. WALL‡ BYRON J. ADAMS§ 《Global Change Biology》2008,14(8):1734-1744
Low-diversity ecosystems cover large portions of the Earth's land surface, yet studies of climate change on ecosystem functioning typically focus on temperate ecosystems, where diversity is high and the effects of individual species on ecosystem functioning are difficult to determine. We show that a climate-induced decline of an invertebrate species in a low-diversity ecosystem could contribute to significant changes in carbon (C) cycling. Recent climate variability in the McMurdo Dry Valleys of Antarctica is associated with changes in hydrology, biological productivity, and community composition of terrestrial and aquatic ecosystems. One of the greatest changes documented in the dry valleys is a 65% decrease in the abundance of the dominant soil invertebrate ( Scottnema lindsayae , Nematoda) between 1993 and 2005, illustrating sensitivity of biota in this ecosystem to small changes in temperature. Globally, such declines are expected to have significant influences over ecosystem processes such as C cycling. To determine the implications of this climate-induced decline in nematode abundance on soil C cycling we followed the fate of a 13 C tracer added to soils in Taylor Valley, Antarctica. Carbon assimilation by the dry valley nematode community contributed significantly to soil C cycling (2–7% of the heterotrophic C flux). Thus, the influence of a climate-induced decline in abundance of a dominant species may have a significant effect on ecosystem functioning in a low-diversity ecosystem. 相似文献
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DIANA H. WALL MARK A. BRADFORD MARK G. ST. JOHN JOHN A. TROFYMOW VALERIE BEHAN‐PELLETIER DAVID E. BIGNELL J. MARK DANGERFIELD WILLIAM J. PARTON JOSEF RUSEK WINFRIED VOIGT VOLKMAR WOLTERS HOLLEY ZADEH GARDEL FRED O. AYUKE RICHARD BASHFORD OLGA I. BELJAKOVA PATRICK J. BOHLEN ALAIN BRAUMAN STEPHEN FLEMMING JOH R. HENSCHEL DAN L. JOHNSON T. HEFIN JONES MARCELA KOVAROVA J. MARTY KRANABETTER LES KUTNY KUO‐CHUAN LIN MOHAMED MARYATI DOMINIQUE MASSE ANDREI POKARZHEVSKII HOMATHEVI RAHMAN MILLOR G. SABARÁ JOERG‐ALFRED SALAMON MICHAEL J. SWIFT AMANDA VARELA HERALDO L. VASCONCELOS DON WHITE XIAOMING ZOU 《Global Change Biology》2008,14(11):2661-2677
Climate and litter quality are primary drivers of terrestrial decomposition and, based on evidence from multisite experiments at regional and global scales, are universally factored into global decomposition models. In contrast, soil animals are considered key regulators of decomposition at local scales but their role at larger scales is unresolved. Soil animals are consequently excluded from global models of organic mineralization processes. Incomplete assessment of the roles of soil animals stems from the difficulties of manipulating invertebrate animals experimentally across large geographic gradients. This is compounded by deficient or inconsistent taxonomy. We report a global decomposition experiment to assess the importance of soil animals in C mineralization, in which a common grass litter substrate was exposed to natural decomposition in either control or reduced animal treatments across 30 sites distributed from 43°S to 68°N on six continents. Animals in the mesofaunal size range were recovered from the litter by Tullgren extraction and identified to common specifications, mostly at the ordinal level. The design of the trials enabled faunal contribution to be evaluated against abiotic parameters between sites. Soil animals increase decomposition rates in temperate and wet tropical climates, but have neutral effects where temperature or moisture constrain biological activity. Our findings highlight that faunal influences on decomposition are dependent on prevailing climatic conditions. We conclude that (1) inclusion of soil animals will improve the predictive capabilities of region‐ or biome‐scale decomposition models, (2) soil animal influences on decomposition are important at the regional scale when attempting to predict global change scenarios, and (3) the statistical relationship between decomposition rates and climate, at the global scale, is robust against changes in soil faunal abundance and diversity. 相似文献
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CHRISTOPHER M. HARDY EVELYN S. KRULL DIANA M. HARTLEY RODERICK L. OLIVER 《Molecular ecology》2010,19(1):197-212
Determining the source and flow of carbon, energy and nutrients through food webs is essential for understanding ecological connectivity and thus determining the impact of management practices on biodiversity. We combined DNA sequencing, microarrays and stable isotope analyses to test whether this approach would allow us to resolve the carbon flows through food webs in a weir pool on the lower Murray River, a highly impacted, complex and regulated ecosystem in southern Australia. We demonstrate that small fish in the Murray River consume a wide range of food items, but that a significant component of carbon and nitrogen entering the food web during dry periods in summer, but not spring, is derived from nonconventional sources other than in-channel primary producers. This study also showed that isotopic analyses alone cannot distinguish food sources and that a combined approach is better able to elucidate food-consumer dynamics. Our results highlight that a major river ecosystem, stressed by reduced environmental flows, can rapidly undergo significant and previously undetected changes that impact on the ecology of the system as a whole. 相似文献
26.
Internal Potassium and Chloride Activities and the Effects of Acetylcholine on Identifiable <Emphasis Type="Italic">Aplysia</Emphasis> Neurones 总被引:2,自引:0,他引:2
It has been suggested that some inhibitory postsynaptic potentials in the abdominal ganglion cells of Aplysia may reflect activation of the sodium pump by acetylcholine. Measurement of electrolyte activity, however, shows that the effect probably arises from changes in membrane permeability to potassium. 相似文献
27.
CARLOS D. CAMP DIANA L. HUESTIS JEREMY L. MARSHALL 《Biological journal of the Linnean Society. Linnean Society of London》2007,91(2):227-238
Terrestrial adaptations by small, desmognathine salamanders in Appalachian stream communities have been viewed as evolved responses to large, aquatic, predatory congeners. We tested the role of moisture in the development of adaptive phenotypes in the small, semiterrestrial Desmognathus ocoee . We measured indicators of relative terrestrial vs. aquatic phenotypes (i.e. tolerance of desiccation, anatomical depression of body/tail) using individuals from stream habitats having different flow regimes within each of three geographical locations. Salamanders from intermittent, first-order streams exhibited greater desiccation tolerance, took longer to reach tolerance limits, and had more anatomically depressed bodies/tails than those from second-order, perennial streams, regardless of location. Phenotypes of salamanders from second-order streams showed aquatic tendencies. Phenotypic variation was consistent with relative habitat stability and not with relative abundance of large congeners. MtDNA analysis revealed that individuals grouped together based on geographical location and not habitat type, implying that the observed phenotypic differences arose in situ at each geographical location. Recent phylogenetic reconstructions of the Desmognathus indicate that large, aquatic forms are derived, and their appearance corresponds with the late Cenozoic development of modern Appalachian topography. We propose that radiation of desmognathine lifestyles and associated phenotypes tracked the formation of moisture-stability gradients associated with the creation of cool, wet, montane habitats. © 2007 The Linnean Society of London, Biological Journal of the Linnean Society , 2007, 91 , 227–238. 相似文献
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- 1 This review highlights the status of the European wild rabbit Oryctolagus cuniculus, which is threatened within its native range and yet is a highly successful colonizer across its worldwide, introduced range.
- 2 The European wild rabbit is a keystone species in Iberia, and the survival of a range of threatened predator species, including the Iberian lynx Lynx pardinus and Spanish imperial eagle Aquila aldabertii, is dependent upon the restoration of rabbit populations. Although not native to the UK, the rabbit also performs significant ecosystem services for nationally rare UK species, by maintaining short sward heights in heathland and grassland ecosystems, and serving as a prey item for populations of predators.
- 3 We identify the European wild rabbit as an excellent model to demonstrate the wide range of complex effects that an introduced mammalian species may exert on ecosystems to which it has been introduced. These effects include habitat degradation following overgrazing, competition with native mammals and facilitating meso‐predator release and hyperpredation.
- 4 We also show that rabbit eradication from some sites may generate more problems than are solved because of the impacts of trophic cascades stemming from dependence on rabbits by native predator assemblages.
30.
DIANA PUSHKINA 《Mammal Review》2007,37(3):224-245
- 1 The Palaeoloxodon antiquus large‐mammal assemblage was typical of the late middle and late Pleistocene interglacials in Europe. This review examines the assemblage's origins, dispersal and cohesiveness in Eurasia.
- 2 During the more climatically equable middle‐Pleistocene periods, the Palaeoloxodon assemblage (or closely related) species occurred across central Eurasia almost simultaneously. In Central and Western Europe, these species responded to climatic changes together as an unvarying interglacial assemblage, whereas in Eastern Europe and Siberia, they occurred in diverging assemblages. The boundary of the Palaeoloxodon assemblage can be drawn roughly from Poland to Romania.
- 3 In Central and Western Europe this interglacial assemblage last occurred during the Eemian. During this period many of the Palaeoloxodon assemblage species may also have co‐occurred in south‐eastern Europe and, except for Bubalus murrensis and Hippopotamus amphibius, further eastwards. The extinct species of the Palaeoloxodon assemblage disappeared in Siberia and Central Asia prior to Europe and the Caucasus whereas the extant species were already present in their modern distribution areas.
- 4 A quantitative study of faunal associations across Eurasia, following much‐needed comprehensive systematic reviews, would further elucidate the patterns of faunal change associated with local and global climatic changes during the middle to late Pleistocene.