نتایج جستجو برای: latitude
تعداد نتایج: 16503 فیلتر نتایج به سال:
Latitudinal differences in life history traits driven by differences in seasonal time constraints have been widely documented. Yet, latitudinal patterns in (age-specific) mortality rates have been poorly studied. Here, we studied latitudinal differences in pre-adult age-specific mortality patterns in the strictly univoltine damselfly Lestes sponsa. We compared individuals from three latitudes r...
Evolutionary hypotheses to explain the greater numbers of species in the tropics than the temperate zone include greater age and area, higher temperature and metabolic rates, and greater ecological opportunity. These ideas make contrasting predictions about the relationship between speciation processes and latitude, which I elaborate and evaluate. Available data suggest that per capita speciati...
This paper considers how and why natural selection might promote or block the photoperiodic regulation of a mammal's reproduction. The factors most important in making this decision would seem to be the following: life expectancy, length of the female's cycle, feeding strategy, the presence or absence of survival mechanisms like hibernation, and the nature of the seasonal challenges offered by ...
Species-rich tropical communities are expected to be more specialized than their temperate counterparts. Several studies have reported increasing biotic specialization toward the tropics, whereas others have not found latitudinal trends once accounting for sampling bias or differences in plant diversity. Thus, the direction of the latitudinal specialization gradient remains contentious. With an...
[1] Precipitation in north-central (subtropical) Chile has been declining over the last 130 years. This is of concern in a region where precipitation is already low and which hosts considerable economic activity and a large population. Interannual variability of precipitation is primarily controlled by ENSO, but the reasons for the increasing aridity have remained elusive. Here we show that the...
Dark-eyed juncos (Junco hyemalis) from two elevations in the Rocky Mountains of Canada display different life histories. Birds breeding at high elevation face a later and compressed reproductive season during which they raise on average half the number of broods (young) than their low-elevation conspecifics. Fledglings at high elevation are heavier, fatter, and have an increased chance of survi...
BACKGROUND The space and time distribution of risk factors for allergic diseases may provide insights into disease mechanisms. Allergy is believed to vary by month of birth, but multinational studies taking into account latitude have not been conducted. METHODS AND FINDINGS A questionnaire was distributed in 54 centres to a representative sample of 20- to 44-y-old men and women mainly in Euro...
The traditional IBP formulation of the energy budget is unsuitable for many marine organisms, partly because it sets production and respiration as alternative sinks when in reallty they are linked but also because it fails to recognise the heterogeneous nature of respiratory demand. The vanous components of total respiration reflect separate demands for ATP which are hkely to differ in their re...
[1] All-sky imagers located at Tucumán, Argentina (26.9 S, 65 W, 14.2 S dip latitude), and Arequipa, Perú (16.5 S, 71.5 W, 2.7 S dip latitude), are used to track 630 nm airglow depletion motions in the first use of multisite airglow imagers for studies of low-latitude plasma dynamics. A new image analysis technique yields a consistent determination of nighttime zonal plasma drifts from all-sky ...
How evolution may mitigate the effects of global warming and pesticide exposure on predator-prey interactions is directly relevant for vector control. Using a space-for-time substitution approach, we addressed how 4°C warming and exposure to the pesticide endosulfan shape the predation on Culex pipiens mosquitoes by damselfly predators from replicated low- and high-latitude populations. Althoug...
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