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91.
CHRISTOPHER J. RAXWORTHY RICHARD G. PEARSON NIRHY RABIBISOA† RY M. RAKOTONDRAZAFY† JEAN-BAPTISTE RAMANAMANJATO† ACHILLE P. RASELIMANANA† SHENGHAI WU‡ RONALD A. NUSSBAUM§ DÁITHÍ A. STONE¶ 《Global Change Biology》2008,14(8):1703-1720
One of the predicted biological responses to climate warming is the upslope displacement of species distributions. In the tropics, because montane assemblages frequently include local endemics that are distributed close to summits, these species may be especially vulnerable to experiencing complete habitat loss from warming. However, there is currently a dearth of information available for tropical regions. Here, we present a preliminary appraisal of this extinction threat using the herpetological assemblage of the Tsaratanana Massif in northern Madagascar (the island's highest massif), which is rich with montane endemism. We present meteorological evidence (individual and combined regional weather station data and reanalysis forecast data) for recent warming in Madagascar, and show that this trend is consistent with recent climate model simulations. Using standard moist adiabatic lapse rates, these observed meteorological warming trends in northern Madagascar predict upslope species displacement of 17–74 m per decade between 1993 and 2003. Over this same period, we also report preliminary data supporting a trend for upslope distribution movements, based on two surveys we completed at Tsaratanana. For 30 species, representing five families of reptiles and amphibians, we found overall mean shifts in elevational midpoint of 19–51 m upslope (mean lower elevation limit 29–114 m; mean upper elevation limit ?8 to 53 m). We also found upslope trends in mean and median elevational observations in seven and six of nine species analysed. Phenological differences between these surveys do not appear to be substantial, but these upslope shifts are consistent with the predictions based on meteorological warming. An elevational range displacement analysis projects complete habitat loss for three species below the 2 °C ‘dangerous’ warming threshold. One of these species is not contracting its distribution, but the other two were not resampled in 2003. A preliminary review of the other massifs in Madagascar indicates potential similar vulnerability to habitat loss and upslope extinction. Consequently, we urgently recommend additional elevational surveys for these and other tropical montane assemblages, which should also include, when possible, the monitoring of local meteorological conditions and habitat change. 相似文献
92.
The grand game of metazoan phylogeny: rules and strategies 总被引:4,自引:0,他引:4
RONALD A. JENNER FREDERICK R. SGHRAM 《Biological reviews of the Cambridge Philosophical Society》1999,74(2):121-142
Many cladistic analyses of animal phylogeny have been published by authors arguing that their results are well supported. Comparison of these analyses indicates that there can be as yet no general consensus about the evolution of the animal phyla. We show that the various cladistic studies published to date differ significantly in methods of character selection, character coding, scoring and weighting, ground-pattern reconstructions, and taxa selection. These methodological differences are seldom made explicit, which hinders comparison of different studies and makes it impossible to assess a particular phylogeny outside its own scope. The effects of these methodological differences must be considered before we can hope to reach a morphological reference framework needed for effective comparison and combination with the evidence obtained from molecular and developmental genetic studies. 相似文献
93.
94.
A model developed by the authors ( Huang et al. 1998 ) was further validated against field measurements from various regions of the world and calibrated to estimate methane emission from irrigated rice cultivation of China. On the basis of available information on rice cultivated area, growth duration, grain yield, soil texture and temperature, methane emission from Chinese rice paddies was estimated for 28 rice cultivated provinces in mainland. The calculated daily methane emission rates, on a provincial scale, ranged from 0.15 to 0.86 g m–2 with an average of 0.32 g m–2. Five of the top six locations with higher daily methane emissions are located at a latitude between 28° and 31° N. A total amount of 9.66 Tg (1 Tg = 1012 g) CH4 per year, ranging from 7.19 to 13.62, was estimated to be released from Chinese rice paddy soils. Of the total, 45% is emitted from the single-rice growing season, and 19% and 36% are from the early-rice and the late-rice growing seasons, respectively. Approximately 70% of the total is emitted in the region located at latitude between 25° and 32° N. The emissions from rice fields in Sichuan and Hunan Province were calculated to be 2.85 Tg y–1, accounting for ≈ 30% of the total. Comparisons of the estimated and the observed emission rates show that the estimates were, in general, close to the measurements at most locations. 相似文献
95.
LARGE doses of 3,4-dihydroxyphenylalanine (dopa) cause increased locomotor activity in rats and mice pretreated with a peripherally acting decarboxylase inhibitor1–3. The effect of dopa is enhanced in animals pretreated with a mono-amine oxidase inhibitor4–7 and reduced when the decarboxylation of dopa in the brain is inhibited1. Consequently, the increase in motor activity is thought to be due to the formation of catecholamines in the brain. 相似文献
96.
RONALD E. HEINRICH CHRISTOPHER B. RUFF DAVID B. WEISHAMPEL 《Zoological Journal of the Linnean Society》1993,108(2):179-196
Ontogenetic changes in femoral morphology and locomotion were analysed in the iguanodontian dinosaur Dryosaurus lettowvorbecki using cross-sectional data and applying principles of beam theory. The results presented here suggest that locomotor ontogeny in D. lettowvorbecki was more complicated than has generally been recognized. The percentage cortical area (a measure of the relative amount of bone) increases abruptly over a relatively short period during early ontogeny and then remains uniform during subsequent increases in body size. Modifications in cross-sectional shape also occur with increasing size, as demonstrated by differences in second moment of area ratios. The patterns of change in these properties indicate that the orientation of mechanical loadings acting on the femur of D. lettowvorbecki differed at various stages of growth and development. It is suggested that the alterations in femoral architecture described here reflect a shift from quadrupedality to bipedality early in the ontogeny of this animal. 相似文献
97.
98.
BARRY J. FOX MARILYN D. FOX JENNIFER E. TAYLOR G. P. JACKSON JOHN SIMPSON PETER HIGGS LOUISA REBEC RONALD AVERY 《Austral ecology》1996,21(2):184-199
Abstract We have begun a long-term ecological research project to address questions about the impact of multiple disturbances on the species richness of communities and whether multiple disturbances are additive or interactive. A protected water catchment area was chosen, which is subjected to fires, sand mining and clearing, and for which detailed records are available. The study area, at Tomago (32°52′S, 151°45′E), has forest, woodland, shrubland and swamp on a sand substrate, with the vegetated dunes forming part of a coastal embayment. Forty-four sites were located in forested areas that had undergone disturbance by either fire, sand mining or clearing. Sites of each disturbance type were grouped into four age classes: less than 1 year since disturbance, nominally 1991; 5 years, nominally 1986; 11 years, nominally 1980; and 17 years, nominally 1974. A set of burned sites, with the time of the last fire matched to the times of the other disturbances, was used as the control response. In this paper we describe the study area and sites, then examine the effects of each single disturbance on vegetation structure. Canopy cover increased with time and type of disturbance, with 17 year old cleared or mined sites similar to the cover of 11 year old burned sites. In the first two years after disturbance, burned sites had significantly more understorey vegetation than cleared or mined sites, but by 5 years all three were similar. The data presented here show that regeneration of mined sites at Tomago is substantially slower than regeneration following disturbance by fire, with the regeneration of cleared sites intermediate but closer to mining than fire. After 17 years regeneration, cleared and sand mined sites had not returned to the vegetation structure of the pre-disturbance state. Understorey height and the amount of vegetation on cleared or mined sites have not achieved the levels in the original forest, although canopy cover did seem to have reached pre-disturbance levels. Current rehabilitation techniques are more sophisticated than those used 17 years ago and continued monitoring of sites currently being rehabilitated may show a faster return to pre-disturbance states. Having established the hierarchy and nature of the response to each single disturbance here, we are now in a position to investigate the impact of multiple disturbances. 相似文献
99.
THOMAS R. MASON IAN G. STANISTREET RONALD TAVENER-SMITH 《Lethaia: An International Journal of Palaeontology and Stratigraphy》1983,16(4):241-247
The presence of spiral trace fossils is reported for the first time from six localities in strata of the Vryheid Formation of the Ecca Group (Lower Permian) in South Africa. These localities are all in the northeast part of the main Karoo basin of sedimentation. The fossils arc assigned to the ichnospecies Spirodesmos archimedeus , representing the spiral trail or burrow of a deposit-feeding organism. In contrast to other reports of spiral trace fossils, the Spirodesmos traces described here were formed in a shallow-water environment. This is established on both sedimentary and ichnofacies evidence. Associated trace fossils include Skolithos, Corophioides and Siphonichnus , all of which arc members of the Skolithos ichnofacies of Scilacher. The occurrence of Spirodesmos in this ichnofacies suggests that these strata were deposited in a marine basin. 相似文献
100.