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941.
Shifts in the spatio-temporal growth dynamics of shortleaf pine 总被引:2,自引:0,他引:2
Previous studies focusing on the growth history of Pinus echinata at the edge of its geographical range have suggested that changes in growth correspond to climatic and non-climatic (e.g.,
anthropogenic) factors. We employ a regime-dependent state-space model that allows us to detect and characterize the changes
in tree growth dynamics over space and time using readily available dendrochronological and climatic data in the presence
of various sources of uncertainty. We utilize methods common in atmospheric sciences but relatively unknown in ecology and
forestry to develop a hierarchical model for tree growth and describe the growth dynamics. The utility of such methods for
addressing ecological problems will grow as more high dimensional spatio-temporal processes are considered and datasets become
more readily available. 相似文献
942.
Algal turfs are the major primary producing component on many coral reefs and this production supports higher levels in the
complex reef trophic web. Rates of metabolism of algal turfs are related positively to water motion, consistent with limitation
by the diffusion of a substance through a boundary layer. Based on engineering mass transfer theory, we hypothesized that
photosynthesis of algal turfs is controlled by rates of mass transfer and responses of photosynthesis to increasing flow speed
should be predicted by engineering correlations. This hypothesis was tested in ten experiments where photosynthesis was estimated
in a flume/respirometer from changes in dissolved oxygen at eight flow speeds between 0.08 and 0.52 m/s. Flow in the flume
and over the reef at Kaneohe Bay, Oahu, Hawaii was estimated using hot-film thermistor and electromagnetic current meters.
Rates of photosynthesis were related positively to flow in all experiments and plots of the log of the average Sherwood number
(Sh
meas) versus log Reynolds number (Re
D) for each experiment are lower than predicted for mass transfer through a turbulent boundary layer. Algal turf-covered plates
are characterized as hydrodynamically transitional to fully rough surfaces and the lower than predicted slopes suggest that
roughness reduces rates of mass transfer. A negative correlation between algal turf biomass and slopes of the log Sh
meas−log Re
D plots suggests that mass transfer to algal turfs is affected significantly by the physical structure of the algal community.
Patterns of photosynthesis based on changes in dissolved oxygen and dissolved inorganic carbon concentrations (DIC) indicate
that the flow speed effect is not the result of increased flux of oxygen from the algal turfs, and combined with the short
response time to flow speed, suggest that DIC may limit rates of photosynthesis. Although there are differences between flow
in the flume and flow over algal turfs on the reef, these results suggest that photosynthesis is controlled, at least in part,
by mass transfer. The chemical engineering approach provides a framework to pose further testable hypotheses about how algal
canopy height, flow oscillation, turbulence, and substratum roughness may modulate rates of metabolism of coral reef algal
turfs. 相似文献
943.
Raphaël Jeanson Jennifer H. Fewell Root Gorelick Susan M. Bertram 《Behavioral ecology and sociobiology》2007,62(2):289-298
Empirical evidence suggests that division of labor in insect societies is positively related to group size both within and
across taxa. Response threshold models (RTM) have been commonly used to analyze patterns of division of labor. However, these
models have been explored empirically and theoretically for only a limited number of tasks, and few studies have examined
predictions of the model as colony size and work availability change. We theoretically examine how group size influences division
of labor using a fixed response-threshold model. We simultaneously explore how expected by-products of increased colony size,
including demand (total work need relative to total work force available) and task number, affect this relationship. Our results
indicate that both low demand and high task number positively influence division of labor. We suggest that these changes parallel
what is observed within social groups as their size increases, and that, in part, the commonly observed increased division
of labor with increasing group size is emergent. 相似文献
944.
Jesús M. Avilés Bård G. Stokke Arne Moksnes Eivin Røskaft Anders P. Møller 《Behavioral ecology and sociobiology》2007,61(3):475-485
The outer layer of the eggshell in birds is in many cases covered by pigments that are assumed to be genetically determined traits with a negligible environmental component. To test the hypothesis that spring environmental conditions (i.e., temperature and rainfall) may affect bird egg pigmentation, we measured by spectrophotometry and photography egg coloration and spottiness on reed warbler (Acrocephalus scirpaceus L.) clutches parasitized by the common cuckoo (Cuculus canorus L.) collected over a period of 24 years and preserved in the Zoological Museum, Copenhagen, Denmark. In addition, we investigated whether spring environmental conditions may influence the coevolutionary relationship between the cuckoo and its host via changes in cuckoo–host egg matching. Generalized mixed models revealed that reed warbler eggs were more brilliant in those springs with a higher rainfall and tended to be bluer and greener in springs with a lower relative temperature. On the other hand, cuckoo eggs were bluer and greener in springs with a higher rainfall. Cuckoo–host egg matching in blue-greenness and spottiness was better in springs with a higher rainfall. These results provide support for the existence of an environmental component on bird egg coloration and suggest that environmental factors may potentially affect the outcome of important features of the arms race between cuckoos and reed warblers. 相似文献
945.
Adam R. Smith William T. Wcislo Sean O’Donnell 《Behavioral ecology and sociobiology》2007,61(7):1111-1120
Facultatively solitary and eusocial species allow for direct tests of the benefits of group living. We used the facultatively
social sweat bee Megalopta genalis to test several benefits of group living. We surveyed natural nests modified for observation in the field weekly for 5 weeks
in 2003. First, we demonstrate that social and solitary nesting are alternative behaviors, rather than different points on
one developmental trajectory. Next, we show that solitary nests suffered significantly higher rates of nest failure than did
social nests. Nest failure apparently resulted from solitary foundress mortality and subsequent brood orphanage. Social nests
had significantly higher productivity, measured as new brood cells provisioned during the study, than did solitary nests.
After accounting for nest failures, per capita productivity did not change with group size. Our results support key predictions
of Assured Fitness Return models, suggesting such indirect fitness benefits favor eusocial nesting in M. genalis. We compared field collections of natural nests to our observation nest data to show that without accounting for nest failures,
M. genalis appear to suffer a per capita productivity decrease with increasing group size. Calculating per capita productivity from
collected nests without accounting for the differential probabilities of survival across group sizes leads to an overestimate
of solitary nest productivity. 相似文献
946.
Nadine C. Chapman Benjamin P. Oldroyd William O. H. Hughes 《Behavioral ecology and sociobiology》2007,61(8):1185-1194
Which task a social insect worker engages in is influenced by the worker’s age, genotype and the colony’s needs. In the honeybee,
Apis mellifera, genotype influences both the age a worker switches tasks and its propensity of engaging in specialist tasks, such as water
collecting, which only some workers will perform. In this study, we used colonies with natural levels of genetic diversity
and manipulated colony age demography to drastically increase the stimuli for the generalist tasks of foraging and nursing,
which all workers are thought to engage in at some point in their lives. We examined the representation of worker patrilines
engaged in nursing and foraging before and after the perturbation. The representation of patrilines among foragers and nurses
differed from that of their overall colony’s population. In the case of foraging, over- and underrepresentation of some patrilines
was not simply due to differences in rates of development among patrilines. We show that replacement foragers tend to be drawn
from patrilines that were overrepresented among foragers before the perturbation, suggesting that there is a genetic component
to the tendency to engage in foraging. In contrast, the representation of patrilines in replacement nurses differed from that
in the unperturbed nursing population. Our results show that there is a genetic influence on even the generalist tasks of
foraging and nursing, and that the way patrilines in genetically diverse colonies respond to increases in task stimuli depends
upon the task. The possible significance of this genetic influence on task allocation is discussed.
Electronic supplementary material Supplementary material is available in the online version of this article at doi: and is accessible to authorized users. 相似文献
947.
Summary. We report field and laboratory evidence indicating that the defensive compounds secreted by the millipedes Amplinus bitumidus (Diplopoda: Polydesmida) and Anadenobolus putealis (Diplopoda: Spirobolida) attract the carrion scarab Canthon morsei (Scarabaeidae: Scarabaeinae). In a Mexican tropical rain forest, C. morsei was mostly caught in pitfall traps baited with the carcasses of both millipede species. Only a few beetles were attracted
to fish carrion. Experimental evidence indicates that C. morsei is attracted to freshly dead millipedes. Benzaldehyde and HCN were identified from Amplinus bitumidus; but 2-methyl-1,4-benzoquinone (toluquinone) and 2-methoxy- 3-methyl-1,4-benzoquinone from Anadenobolus putealis. Benzaldehyde attracted significantly more C. morsei individuals than fish meat, or millipedes of both species did after rinsing in hexane. This is the first report of Polydesmida
attracting dung beetles. 相似文献
948.
The microphytoplankton assemblages were studied from water samples collected at eight discrete depths in the top 120 m at
five central (open ocean) and four western (shelf/slope region) locations in the Bay of Bengal. The Bay is a low-productive
warm pool regime with poor inorganic nutrient inputs to its intensely stratified surface layer despite the very large riverine
influx. In addition, the prolonged cloud cover has an adverse effect on the top 25–40 m, on primary production, chlorophyll
concentration and phytoplankton assemblages. Microphytoplankton were the most abundant in the northern area of the Bay. A
total of 153 phytoplankton species were identified during this study. The most abundant species (at least 1,800 individual
cells belonging to a given species or ≥2% of the total counts of identified specimens) during this study were: Thalassiothrix longissima, Thalassiothrix fauenfeldii, Rhizosolenia styliformis, Nitzschia angularis, Thalassionema nitzschioides, Coscinodiscus radiatus, Chaetoceros eibenii, Skeletonema costatum, Coscinodiscus concinnus and Chaetoceros coarctatus. Similarly, there were 20 moderately abundant (≥0.5 but <2%) species. Thirty-three of the least abundant species (<0.5%)
occurred at one station. Diatom species, T. fauenfeldii and T. longissima were ubiquitous in the study area. The exclusive occurrence of S. costatum in the northernmost stations suggests that it proliferates only in the low-salinity regions with adequate silica from the
land inputs. Abundance of pennate diatoms was higher in the open Bay compared to that of centric diatoms in the more productive
northern locations and the western Bay. There appears to be a basic difference between near shore flora and offshore flora.
This first analysis of phytoplankton assemblages from the offshore Bay suggests that while there is predominance of only a
few species, the Bay harbors very diverse diatom communities that seem to be syntrophic, non-competitive and co-habiting in
the generally low nutrient, stratified surface waters. 相似文献
949.
Migrating birds often alternate between flight steps, when distance is covered and energy consumed, and stopover periods,
when energy reserves are restored. An alternative strategy is fly-and-forage migration, useful mainly for birds that hunt
or locate their prey in flight, and thus, enables birds to combine foraging with covering migration distance. The favourability
of this strategy in comparison with the traditional stopover strategy depends on costs of reduced effective travel speed and
benefits of offsetting energy consumption during migration flights. Evaluating these cost-benefit effects, we predict that
fly-and-forage migration is favourable under many conditions (increasing total migration speed), both as a pure strategy and
in combination with stopover behaviour. We used the osprey (Pandion haliaetus) as test case for investigating the importance of this strategy during spring and autumn migration at a lake in southern
Sweden. The majority, 78%, of passing ospreys behaved according to the fly-and-forage migration strategy by deviating from
their migratory track to visit or forage at the lake, while 12% migrated past the lake without response, and 10% made stopovers
at the lake. Foraging success of passing ospreys was almost as good as for birds on stopover. Timing of foraging demonstrated
that the birds adopted a genuine fly-and-forage strategy rather than intensified foraging before and after the daily travelling
period. We predict that fly-and-forage migration is widely used and important among many species besides the osprey, and the
exploration of its occurrence and consequences will be a challenging task in the field of optimal migration. 相似文献
950.
Francesca Rossi 《Marine Biology》2007,150(6):1073-1081
In intertidal sediments, burial and decomposition of macroalgal detritus can fuel the sediment of carbon (C) and nitrogen
(N), which can be either promptly mineralised or assimilated to enter the food web. This study investigates the transfer of
algal-derived C and N to the sediment and to the infauna feeding primarily on benthic diatoms. Thalli of Ulva spp. were 13C- and 15N-labelled in the mesocosm and frozen to create detritus. Thawed macroalgae were, then, buried in the sediment of an intertidal
sand-flat forming a mosaic of small patches (50 × 50 cm2) enriched with the macroalgae interspersed with bare sediment. The area was dominated by Corophium volutator and Hydrobia ulvae. The uptake of 13C and 15N was measured in the residual macroalgae, in the sediment and in those animals. Decomposition of detritus was rapid and after
4 weeks the residual biomass was 3% the amount added. Algal-derived 13C and 15N were moved to the sediment. The total amount of 13C and 15N retained in the sediment after completing the decomposition was 3.4 ± 0.5% 13C and 2.7 ± 0.6% 15N the amount decomposed. During the first 2 weeks more N than C was assimilated (1.7% 13C and 13.5% 15N). During the remaining two weeks, N was released from the sediment, while there was little accumulation of C (+6.4 ± 2.0
% 13C and −7.7 ± 3.8% 15N). At the end of the decomposition, animals were 15N- and 13C-labelled. Considering the total accumulation of label in the sediment, they accounted for 3.5 ± 1.8% 13C and 25.8 ± 12.9 % 15N. Similarly, considering the mass of the heavy isotopes gained (13C) or lost (15N) during the remaining 2 weeks, the animals accounted for 4.7 ± 2.1% of the 13C in excess and for 18.6 ± 9.1% of the 15N loss. The transfer of C and N to the sediment and to the surface deposit-feeders can be a relevant mechanism to remove the
excess of detritus from the sediment. 相似文献