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81.
Abstract In a restinga habitat of southeastern Brazil, we studied some aspects of the thermal biology of two sympatric skinks (Mabuya macrorhyncha and Mabuya agilis) with distinct microhabitat preferences. The two species did not differ significantly in their mean body temperature. Sex and body size did not explain body temperature variation within either species. The body temperature of both species is significantly affected by air temperature, but only that of M. agilis is significantly influenced by sand surface temperature, presumably due to its more terrestrial habit compared to M. macrorhyncha. We found no significant seasonal variation in body temperature for either species, although environmental temperatures varied seasonally, indicating that both species may be selecting an optimal range of body temperatures, possibly through behavioural thermoregulation.  相似文献   
82.
We analysed statistically the influence of density-dependent regulation, seasonality and precipitation on the realized population rate of change of the Neotropical rodent Phyllotis darwini (Waterhouse 1837) at an intra-annual time scale. We used four years of continuous live trapping at a semiarid locality of north central Chile. Results showed that density-dependence, seasonal effects and precipitation were important factors influencing population growth rates in this species. An empirical population model including a sine function for seasonal effects, a linear form for density-dependence, and precipitation was fitted to the full data set and to the data set with the first year removed (after an outbreak). The empirical model explained 33% and 48% of the variance in population growth. The natural rate of population increase, estimated from the empirical model, was rmax = 2.51 or 5.06 years?1. These estimates indicate a great potential for population increase and may explain the capability of this species to undergo large irruptions. We propose that merging empirical and theoretical modelling with field research is the most promising avenue to understand the outbreaks experienced by some rodent species in western South America.  相似文献   
83.
84.
Abstract ‘Ratadas’ are rodent irruptions or outbreaks that have been recorded in South America since the Spanish conquest in the 16th century. The notion that ratadas are associated with bamboo flowering and subsequent mast seeding at cycles of 30 years has appeared in the literature since the late 1800s. Based on 63 well‐documented cases, we show that not only are ratadas associated with bamboo blooming, but also many are associated with rainfall peaks, and that these two outbreak types are geographically interspersed over South America. In addition, we dispel the notion that South American bamboo blooms occur every 30 years, which may only be the case for Merostachys fistulosa. For other species the modal cycles occur every 14 (Merostachys spp.), 12 (Chusquea quila and/or valdiviensis) or 14 years (Chusquea coleou). We also propose the hypothesis that rainfall‐associated ratadas are ultimately caused by the occurrence of El Niño, and discuss the possible population dynamic mechanisms underlying rodent outbreaks in South America. Aiming at setting a standardized framework for spatial and temporal comparisons, we propose a trapping protocol and a threshold density for assigning the ‘ratada’ label. Several of the mice implicated in ratadas are reservoirs of emerging diseases, thus emphasizing the need for predictive power to forecast disease epidemics that affect human populations. Further, ratadas may be viewed as pulsed resources, thus enabling us to learn more of the ways communities respond to such intermittent inputs.  相似文献   
85.
The present study uses published phylogeographical studies to test the Carnaval–Moritz (CM) model of forest dynamics in the Atlantic forest of Brazil. The model predicts that a large forested area in the north–central region of this biome has remained stable during the last glacial maximum, and only relicts in its current southernmost distributions. All available sequences for phylogeographical studies on vertebrates on the Atlantic forest were obtained from GenBank. All datasets consisted of mitochondrial sequences and were submitted to the same analyses, including time of divergence and migration rates between phylogeographical lineages, as well as historical demography analyses, including neutrality tests and Ne estimates. The species studied showed different degrees of phylogeographical structure. Two contact zones are defined: one very heterogeneous in south‐east Brazil that was largely congruent with the CM model and one around the Doce river further north. Population genetics analyses showed a smaller effective number on southern population, and most of these southern populations showed evidence for recent demographic expansion. These features are also in agreement with the CM model. Additionally, divergence/expansion events dated back to the Pleistocene epoch in all but one organism. According to hierarchical approximate Bayesian computation analysis, most of the data can be attributed to a single event. The results highlight the need for more finescale studies in the Atlantic forest. © 2011 The Linnean Society of London, Biological Journal of the Linnean Society, 2011, 104 , 499–509.  相似文献   
86.
In the last two decades, the relationship between diversity and stability/ecosystem functioning has been widely discussed and has become a central issue in ecology. Here, we assessed the relationship between wetland plant diversity and community resilience after a disturbance. Our study area was located in the Upper Paraná River floodplain (Brazil). An experiment was carried out in situ (18 1 m × 1 m plots with richness varying from 1 to 18 species). In each plot, we recorded the number of species, total per cent vegetation cover and per cent age cover of each species. The above‐ground biomass of wetland plants was removed, simulating a disturbance by animal trampling or an extreme flood. The recovery of vegetation was monitored over 3 months. According to a linear regression, the recovery of wetland plants was positively correlated with diversity. Comparisons with plots containing monocultures of one of the dominant species (Polygonum stelligerum) suggested that this species did not overyield in mixed cultures. Thus, our experiments indicate that the higher resilience in richer plots after a disturbance is mainly due to the fact that species have different resource use requirements (complementarity effect) and not due to the presence of a single, more productive species. Our experiment carried out in a more real condition (in situ) showed that biodiversity is important to wetland functioning and stability, paralleling the results obtained in laboratory and mesocosms experiments. These results also suggest that the loss of plant diversity in our study area could compromise community recovery following strong disturbances.  相似文献   
87.
Niche conservatism has been proposed as a mechanism influencing large‐scale patterns of taxonomic richness. We document the species richness patterns of five monophyletic squamate reptile groups (gekkonids, cordylids‐scincids, lacertids, chameleons and alethinophidian snakes) in eastern and southern Africa, and explore if observed patterns reflect niche conservatism processes. We quantified richness and its relationships with current climatic conditions by gridding species' range maps at 110 × 110 km. Also, dated phylogenies and palaeoclimatic reconstructions, coupled with evidence from the fossil record, were used to approximate the areas and climate characteristics in which each group originated and/or radiated. Mean species richness and geographically corrected confidence intervals in current climate types were calculated for each group in order to establish their climatic preferences. On average, the species richness of older groups (gekkonids, cordylids‐scincids and lacertids) was lower in equatorial climates and higher in arid and temperate conditions, whereas more recent groups (chameleons and alethinophidian snakes) were richer in equatorial and temperate climates and less rich in arid conditions. Across all groups, higher richness was associated with climatic characteristics similar to those prevailing at the time in which each group originated/radiated. The congruence of the current climates where reptile groups are richer and the past climates amidst which those groups originated is consistent with an explanation for their diversity gradients based on niche conservatism.  相似文献   
88.
Members of a new genus and species of harpacticoid copepod crustacean appeared in samples from semi-terrestrial (moist arboreal mosses, wet soil) and aquatic (bromeliad tanks, Sphagnum moss, rock pools, stream) habitats in a remnant of the Atlantic Forest in south-eastern Brazil. The new taxon, for which we propose the name Pindamoraria boraceiae sp. nov. , is distinguished by a unique combination of characters, in particular the segmentation and setation pattern of legs 1–4 in both sexes, the structure of leg 5 in the female, and the strongly modified claw of the maxilliped in the male. It most resembles the canthocamptid genera Moraria , Pseudomoraria , Morariopsis and Paramorariopsis . Both previous records of species of Moraria from South America refer to members of Antarctobiotus , which is not considered a member of the Moraria group: Moraria (Kuehneltiella) neotropica Löffler has previously been transferred to Antarctobiotus ; and we propose herein the transfer of Moraria kummeroworum Ebert & Noodt to Antarctobiotus as well. In the New World, the genus Moraria extends only as far south as Honduras; and Pseudomoraria , Morariopsis and Paramorariopsis are Old World genera. The new species from Brazil is therefore the only member of the Moraria group known from South America.  © 2003 The Linnean Society of London, Zoological Journal of the Linnean Society , 2003, 139, 81–92.  相似文献   
89.
90.
Abstract In a ‘restinga’ habitat of southeastern Brazil, we studied the food habits and the microhabitat use of two lizards with distinct foraging modes: the tropidurid Tropidurus torquatus, a sit-and-wait predator, and the teiid Cnemidophorus ocellifer, a wide forager. The diet of the two species differed strongly, indicating a low level of similarity in their trophic niche. The sit-and-wait predator fed mainly on mobile prey, whereas the wide forager fed mainly on sedentary prey (larvae). The spatial niche breadth of T. torquatus was larger than that of C. ocellifer. Despite interspecific differences, the two species overlapped greatly in micro-habitat use. The data indicate that at Linhares the two lizard species differed more in food resources than in microhabitat, and that most of the food differences reflect the foraging patterns of the species.  相似文献   
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