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1.
Ana Catarina Ferreira Silva Sónia Brazão Steve J. Hawkins Richard C. Thompson Diana M. Boaventura 《Marine Biology》2009,156(12):2591-2599
Wave action is known to influence the abundance and distribution of intertidal organisms. Wave action will also determine
the duration and suitability of various foraging windows (high-tide and low-tide, day and night) for predation and can also
affect predator behaviour, both directly by impeding prey handling and indirectly by influencing prey abundance. It remains
uncertain whether semi-terrestrial mobile predators such as crabs which can access intertidal prey during emersion when the
effects of wave action are minimal, are influenced by exposure. Here, we assessed the effect of wave action on the abundance
and population structure (size and gender) of the semi-terrestrial intertidal crab Pachygrapsus marmoratus on rocky shores in Portugal. The activity of P. marmoratus with the tidal cycle on sheltered and exposed shores was established using baited pots at high-tide to examine whether there
was activity during intertidal immersion and by low-tide searches. Because prey abundance varies along a wave exposure gradient
on most Portuguese shores and because morphology of crab chelipeds are known to be related to diet composition, we further
tested the hypothesis that predator stomach contents reflected differences in prey abundance along the horizontal gradient
in wave exposure and that this would be correlated with the crab cheliped morphology. Thus, we examined phenotypic variation
in P. marmoratus chelipeds across shores of differing exposure to wave action. P. marmoratus was only active during low-tide. Patterns of abundance and population structure of crabs did not vary with exposure to wave
action. Stomach contents, however, varied significantly between shores of differing exposure with a higher consumption of
hard-shelled prey (mussels) on exposed locations, where this type of prey is more abundant, and a higher consumption of barnacles
on sheltered shores. Multivariate geometric analysis of crab claws showed that claws were significantly larger on exposed
shores. There was a significant correlation between animals with larger claws and the abundance of mussels in their stomach.
Variation in cheliped size may have resulted from differing food availability on sheltered and exposed shores. 相似文献
2.
W. S. Grant 《Marine Biology》1977,44(1):15-25
A mosaic patchwork of the barnacle Balanus balanoides L., the mussel Mytilus edulis L., and the alga Fucus vesiculosus L. was found in the transitional region between the mid and high intertidal zones on a rocky headland on Mount Desert Island, Maine, USA. The development of the mosaic was observed by following recruitment and survival of B. balanoides in denuded patches located at the same tidal level along a 60 m stretch of shore. Barnacle recruitment was least under canopies of F. vesiculosus and greatest in open areas kept moist at low tide by surf. Barnacle survival after settlement was least under the F. vesiculosus canopy due to the whiplash effect of the algal fronds in the surf and greatest in open areas free from competition from mussels. In open areas, early mortality was correlated with settlement density. In areas of dense settlement (60 spat cm-2) up to 90% mortality resulted within 5 months from crowding associated with growth. In older individuals crowding produced hummocks of elongated, weakly attached barnacles which were more prone to removal by surf than uncrowded barnacles. Mussels exerted competitive dominance over barnacles for space and the presence of mussel beds prevented further barnacle recruitment. Mussels suffered extensive mortality during winter storms when surf removed dense mats of weakly attached mussels. The patchy distribution of mussels and barnacles results from irregular rock substrata producing numerous environmental patches with respect to wave exposure and drainage at low tide, and from densitydependent mortality of both mussels and barnacles which creates patches of new colonizable space within each environmental patch. 相似文献
3.
N. D. Pentcheff 《Marine Biology》1991,110(3):399-408
Barnacles of the same species (Balanus glandula) show differences both in shell morphology and in their ability to resist crushing from impact at two sites within 8 km of each other which differ in their natural exposure to wave-borne debris (Cattle Point and False Bay, San Juan Island, Washington, USA). In studies performed in 1987, barnacles with shells of a given base diameter at the site exposed to more impact (Cattle Point) were found to have smaller bodies, shorter and thicker shells, and a more protected placement of their opercular valves than barnacles at the protected site. When tested with a standard impact, barnacles from the exposed site were more resistant to crushing both on the first impact and (for those surviving that test) on a second impact 2 wk later. The morphological differences between the two populations may be due to a combination of different shell: body growth rate ratios at the two sites plus passive remodelling of the exposed barnacles by small impacts. The morphological changes at the exposed site, although gained passively, fortuitously provide improved performance in resisting crushing from impact.Sessile Cirripedes, partly from being attached to surfaces having very different characters, partly from undergoing a varying amount of disintegration, and partly from unknown innate causes, are extremely variable As whole groups of specimens often vary in exactly the same manner, it is not easy to exaggerate the difficulty of discriminating species and varieties.Darwin (1854) 相似文献
4.
Protandrous hermaphrodites are predicted to change sex from male to female when relative reproductive fitness of females surpasses
that of males. How size at sex transition varies with population, mating group and individual parameters was investigated
for five populations of the protandrous hermaphrodite slipper snail, Crepidula fornicata. The populations varied for density, size distribution, average mating group size and sex ratio. Size at sex-change was correlated
with the population sex ratio. Comparisons of multiple hypotheses revealed that variables predicting the sex of a snail vary
among positions in the mating group. The variables included body size, the relative size of the snail sitting atop the focal
snail and population density. Our data support the conclusions that size at sex-change (and by inference, the size at which
one sex has relatively greater fitness) is not fixed for these hermaphrodites and that individual size, social conditions
and population differences all influence variation in relative fitness. 相似文献
5.
Is the bat os penis sexually selected? 总被引:4,自引:0,他引:4
D. Hosken K. Jones K. Chipperfield A. Dixson 《Behavioral ecology and sociobiology》2001,50(5):450-460
. The mammalian os penis or baculum is an extremely diverse bone but our understanding of the selective forces behind this diversity remains poor. While genital morphology is generally assumed to be sexually selected, there have been relatively few attempts to test this hypothesis. Here we investigate associations between baculum length and two measures of sexual selection intensity (mating system and testis mass) across bats. Analyses were conducted using both species-level data and phylogenetic comparative techniques. Controlling for the effect of male body mass, baculum length was positively associated with relative testis mass in all cross-species analyses. Additionally, in an analysis that also included mating system, there was an interaction between testis mass, body mass and mating system that significantly influenced baculum length. However, after using independent contrasts to control for phylogenetic inertia in these data, baculum length was not significantly associated with mating system, testis mass or body mass. Thus, increased length of the baculum in bats appears not to be associated with increased sperm competition risk or sexual selection intensity. 相似文献
6.
Mate availability can vary widely in nature depending upon population density and sex ratio and can affect the ability of
individuals to be selective in mate choice. We tested the effects of prior encounters with the opposite sex (i.e., exposure
to the opposite sex either with or without mating) on subsequent mating behavior in two experiments that manipulated mate
availability for both males and females in the wolf spider, Hogna helluo. The probability of mating in the experimental trial depended upon whether the prior encounter involved mating or not, and
males and females responded in opposite directions. Exposure without mating resulted in a higher subsequent frequency of mating
for females and a lower subsequent frequency of mating for males, while prior mating experience resulted in a lower frequency
of female remating and a higher frequency of male remating. Prior exposure without mating did not affect female aggression.
However, mated females engaged in precopulatory cannibalism more frequently than virgins. Mated males escaped postcopulatory
cannibalism more frequently than virgins. Our results show that males respond to exposure without mating in the expected manner.
However, prior mating (1 week earlier) had unexpected effects on males, which may be due to mated males being of higher quality.
There were little or no effects of the size of the prior exposure individual or mate on subsequent mating behaviors. Further
research is needed to determine why different species use different degrees of prior information in mate choice. 相似文献
7.
Yoshitaka Tsubaki Yuka Samejima Michael T. Siva-Jothy 《Behavioral ecology and sociobiology》2010,64(10):1547-1554
Males of some territorial calopterygid damselflies show an elaborate courtship display that involves high-frequency wing-beats
directed toward an incoming female. Although it has been suggested that female mate preference is based on some characteristics
of male’s courtship display, it is unclear whether the courtship display varies between males or is influenced by environmental
conditions. We combined two recent technologies, thermographic imaging and high-speed digital videography, to show that the
wing-beat frequency during courtship (i.e., courtship intensity) in a damselfly, Mnais costalis, is correlated with thorax temperature. Our data indicated that (1) male thorax temperature was associated with solar exposure
in his territory, (2) environmentally derived thermal gain enhanced courtship intensity, (3) hotter males were more likely
to copulate than others, and (4) female thorax temperature during oviposition within a territory was associated with solar
exposure. Males with territories that have longer exposure to sun spots are expected to attain higher thorax temperatures
for longer and so are able to successfully court more females. We suggest that females benefit from mating with hot males
because they will be on a warmer territory while ovipositing. Hot males might also have greater mate guarding ability, and/or
eggs may develop faster in warmer territories. 相似文献
8.
In many species, the ability to evade predators is known to be periodically impaired by increased weight loads due to feeding
and reproduction. Not only may extra weight reduce escape speed, but feeding and mating can also make the prey more noticeable
to visually hunting predators. A number of butterfly species mate for hours, and if a mating couple is disturbed, one of the
butterflies is responsible for flying, whereas its partner remains still. This study investigated the ability of male Pieris napi butterflies to fly while mating, with the prediction that mate carrying impairs flight ability compared to single flying
males and that males with relatively high flight muscle ratios (FMR; male thorax mass/male + female body mass) will have better
flight performance in copula. Our results clearly show that whereas single males always take off at steep angles and fly upwards,
couples invariably have a negative take-off angle and rarely gain height. Moreover, landing height of the couples is positively
associated with higher FMR. Hence, male flight ability when in copula is positively associated with a high relative thorax
mass. Butterfly pairs may thus be at greater risk of predation as a consequence of their impaired flight ability, especially
couples with critically low FMRs (<16%). 相似文献
9.
William D. Brown 《Behavioral ecology and sociobiology》1993,33(3):151-157
Summary Examples of positive assortative mating by body size are abundant but its causes remain controversial. I show that size-assortative mating occurs in the chrysomelid beetle Trirhabda canadensis and I test a series of alternative hypotheses to explain how this mating pattern comes about. Results suggest that assortative mating in this beetle is due to the greater ease with which size-matched pairs can achieve intromission, and not due to size-biased skews in the availability of mates or mate choice favoring large individuals. There was no correlation between male and female elytron length (a measure of body size) at the initiation of courtship, but pairs assorted positively by size at the onset of intromission. Moreover, in the laboratory, there was a negative correlation between male and female size for pairs engaged in courtship that terminated without mating. Assortative mating was not associated with a large-male mating advantage and there was no evidence of female choice of large males. Nor was there unequivocal evidence for male choice of large females; although mating females were slightly larger and considerably heavier than solitary females, males did not differ in the frequency with which they rejected large and small females. Assortative mating in T. canadensis appeared to be caused by the lower ability of mismatched pairs to achieve intromission after an encounter, both when males were larger and when they were smaller than the female. 相似文献
10.
In this study eight different species of barnacles were found within nine species of sponges from the Red Sea. This brings
to 11 the number of sponge-symbiotic barnacles reported from the Red Sea, two of these are new Acasta species (not described herein) and one (A. tzetlini Kolbasov) is a new record for this sea. This number is much higher than that of symbiotic barnacles found within sponges
from either the N. Atlantic (2) or the Mediterranean (4). Two possible explanations for this are the presence of numerous
predators in coral reefs and scarcity of available substrate for settlement. These factors can lead to high incidence of symbiotic
relationships. Of the nine sponge species, only one (Suberites cf. clavatus) had previously been known to contain barnacles. Even at the family level, this is the first record of symbiotic barnacles
in two out of the seven sponge families (Latrunculiidae, Theonellidae). Our present findings strengthen the apparent rule
that the wider the openings in a barnacle shell, the fewer the host taxa with which it will associate, usually from one or
two closely related families, and the more frequent it will associate with elastic sponges. Most Neoacasta laevigata found on Carteriospongia foliascens were located on the same side as the sponge's ostia, i.e. facing the incoming water. This adaptation allows the barnacles
to catch more suspended particles from the water, provides them with more oxygen and prevents their exposure to discharged
sponge waste. The highest density of barnacles observed on one face of a “leaf ” (with ostia) was 0.389 barnacles cm−2 (one barnacle per 2.57 cm2) and on average 0.181 ± 0.68, while the average on the other side was only 0.068 ± 0.52 barnacles cm−2. As indicated by the Morisita index, these barnacles most frequently (58%, n = 12) had a clumped spatial distribution (while the rest were randomly distributed), as is to be expected from such sessile
organisms with internal fertilization via copulation. The presence of N. laevigata induced the growth of secondary perpendicular projections of its host C. foliascens. Of the N. laevigata examined, 17% brooded 324 ± 41 embryos each, of 286 ± 17 μm total length; only 5.7% (n = 123) were found to be dead. Size distribution analysis of skeletal elements from dead barnacles showed them to be significantly
larger than the skeletal elements of the population of live barnacles ( p < 0.05).
Received: 26 June 1998 / Accepted: 1 December 1998 相似文献
11.
Johan Elmberg 《Behavioral ecology and sociobiology》1991,28(2):125-131
Summary The mating behavior of the European common frog, Rana temporaria, was studied experimentally. Female body length was correlated with body mass as well as with fecundity. However, males showed no mating preference with regard to either female body length, body mass, or fecundity. In successive multiple matings, male readiness to re-mate as well as fertilization success did not vary among the first four matings. Further, fertilization success was not correlated with either the number of days since the previous fertilization, water volume in the experimental container, testes mass, female/male body length ratio, or female fecundity. However, there was a positive correlation between fertilization success and male fat reserve status. Sexual competition and mating patterns were studied in tanks in which operational sex ratio (OSR) and male density were manipulated, and time for sexual competition was allowed to vary. Successful take-overs and nonrandom mating (large male advantage) were observed only at a combination of a four-fold male bias in OSR and an unnaturally high male density (30–50/m2). I argue that in natural populations of Rana temporaria: (1) There is considerable intraspecific variation in the opportunity for sexual competition, (2) OSR influences mating pattern more than male density and time (duration of the prespawning period), and (3) nonrandom mating should be rare. 相似文献
12.
The protandric simultaneous hermaphrodite shrimp Lysmata wurdemanni (Gibbes 1850) has a pure searching mating system, i.e., males are continually searching for receptive females and copulation
is brief. To examine whether size-based advantage in male–male competition occurs and whether the mating ability of male-phase
(M) shrimp equals that of euhermaphrodite-phase shrimp serving as males (Em), mating performance, including mating frequency
and precopulatory behavior, of M and Em shrimp was compared using two M:Em ratios. Two experiments were carried out from March
2004 to August 2004 at Florida Institute of Technology’s Vero Beach Marine Laboratory using laboratory-cultured shrimp that
originated from Port Aransas, TX, USA. In the two experiments, one parturial euhermaphrodite-phase shrimp acting as a female
(Ef) was maintained with one M and two Em shrimp (one with and one without an egg mass), and two M and two Em shrimp, respectively.
The M shrimp used were always smaller than the Em shrimp. Experiment 1 showed that there was no significant difference in
mating ability between Em with and without egg mass. In both experiments, the M shrimp gained mating partners more frequently
than the Em shrimp did. In the experiment with two M and two Em shrimp, mating frequencies of the small M and large M shrimp
were similar. Precopulatory behaviors of the M shrimp were more active than those of the Em shrimp. Mating between the small
M and larger Ef shrimp was sometimes successful even when the size difference was 20.0 mm total length (TL). Mating between
a larger M shrimp and smaller Ef shrimp sometimes failed when the size difference was only 13.0 mm TL. Mating frequency of
M shrimp over that of Em shrimp with Ef shrimp increased significantly with increasing density and operational sex ratio.
The advantage of M over Em shrimp in obtaining mating partners is probably a result of sexual selection and adaptation, and
may partially explain the observed delayed sex change in some L. wurdemanni, i.e., some male-phase shrimp grow very large and never become hermaphrodites. 相似文献
13.
The ability of algae to change the shape of their thallus in response to the environment may be of functional and ecological
importance to the alga, with many species of macroalgae exhibiting a great range of morphological variation across wave exposure
gradients. However, differences in morphology detected between sheltered and exposed environments cannot determine whether
such differences represent plastic responses to the local environment or whether morphology is genetically fixed. This study
tested for differences in the morphology of the common kelp, Ecklonia radiata, between wave sheltered and exposed environments, and reciprocally transplanted juveniles to distinguish the nature of such
differences (i.e. plastic vs fixed traits). Differences between exposure environments were consistent with known effects of
exposure (i.e. a wide, thin thallus at sheltered sites and a narrow, thick thallus with a thick stipe at exposed sites). The
reciprocal transplant experiment confirmed that morphological plasticity was the mechanism enabling this alga to display different
patterns in morphology between exposure environments. Individuals transplanted to the exposed environment underwent a rapid
and extreme response in morphology, which was not apparent in individuals transplanted to the sheltered environment that responded
more slowly. These results suggest that stressors typical of sheltered environments (i.e. diffusion stress) may not be as
influential (if at all) compared to stressors typical of exposed environments (i.e. breakage, dislodgement) in differentiating
morphological characters between exposure environments. 相似文献
14.
Desiccation as a factor in the intertidal zonation of barnacles 总被引:2,自引:0,他引:2
B. A. Foster 《Marine Biology》1971,8(1):12-29
Four species of balanomorph barnacles, Balanus crenatus
Brugière, B. balanoides (L.), Elminius modestus
Darwin and Chthamalus stellatus (Poli), were studied to assess the susceptibility of intertidal barnacle species to desiccation. Known sized samples of barnacles were exposed to controlled desiccating conditions and subsequent survival and water loss were determined. It is clear that the ability to live high on the shore is dependent on a reduction of the overall permeability to water loss. Because of greater surface area to volume ratios, small stages are particularly prone to desiccation. In normal intertidal emersion periods, small stages of B. crenatus particularly, and also of B. balanoides and E. modestus which are similar in their desiccation resistance, would be susceptible to desiccation at normal temperatures and low humidities. Large barnacles would be more prone to death from high temperatures when the tide is out. The spat of C. stellatus, although surviving much longer than spat of larger dimensions of the other species, must also be prone to prolonged emersion conditions at high shore levels. 相似文献
15.
The growth of insoluble, membrane-limited spherical granules has been studied in the barnacleElminius modestus Darwin, collected on 26 March 1983 from the shore of the Huon River, Tasmania. X-ray microprobe analysis of these granules using a non-aqueous fixation method established their elemental composition (in order of abundance) to be phosphorus, zinc, potassium, sulphur and chlorine. Formation of granules is initiated on exposure to high zinc levels in the ambient seawater. Granules were first detected in barnacles transplanted from an area of low seawater zinc levels to one with high levels after 12 d exposure. Over a period of 5 mo, granules increased both in numbers and diameter and were concentrated in specialized cells around the gut, the stratum perintestinale. Barnacles positioned at mid-tide level in high ambient zinc levels, developed greater numbers of larger granules than those positioned below low-tide level. Rate of uptake of zinc was higher in the former group during the first month, after which similar rates were observed in the two groups. Barnacles transplanted from an area of high to one of low seawater zinc concentration, lost zinc slowly (0.3% body load per day over an 11 wk period). There was no evidence to suggest that zinc granules are excreted intact across the gut. We conclude that zinc granules represent a detoxification mechanism for surplus zinc. 相似文献
16.
Hong Kong, lying just below the Tropic of Cancer (22°17′N, 114°09′E), experiences a strongly seasonal environment, with a
cool almost temperate winter and a hot, tropical, summer. Histological sectioning of the gonads of the high-shore barnacle,
Chthamalus malayensis Pilsbry, showed a seasonal trend in the development of its reproductive organs. Four stages of female gonad development were
identified according to the cell types present: post-spawning, resting, growth and mature stages. The female gonad was mature
from April to November, which was related to seawater temperatures, and entered a resting phase from December to March. Although
the male gonad showed a seasonal developmental trend and reached maximum maturity in summer, the seminal vesicles were full
of spermatozoa and functional throughout the year. The reproductive season of this species is therefore solely dependant upon
the maturity of the female gonad. The estimated maximum number of broods per year was up to 10 and the maximum number of eggs
produced per brood can reach 3,000 eggs. The minimum size for female gonad maturity was 6 mm rostro-carinal diameter (RCD)
at which size, the barnacles were ~6-month old. Sperm production occurred at a smaller size (2 mm=2-month old). Compared with
Chthamalus montagui and Chthamalus stellatus from temperate regions, C. malayensis produced a greater number of broods per year, had a longer reproductive period and faster gonad development. Chthamaloid
barnacles in tropical regions may, therefore, invest more energy per year in reproduction during their life span. Contrary
to the seasonal gonad developmental pattern of C. malayensis in the present study, however, C. malayensis in Singapore (which experiences only slight seasonal variation) had mature female and male gonads throughout the year, further
supporting the strong role of climatic conditions effecting the reproductive biology of barnacles. 相似文献
17.
Nathan W. Bailey 《Behavioral ecology and sociobiology》2011,65(12):2269-2278
Social experience can elicit phenotypically plastic changes in mate choice, but little is known about the degree to which
social information from one modality can influence mating decisions based on information from a different modality. I used
the field cricket Teleogryllus oceanicus to test whether experience of chemical cues mimicking a high density of sexually mature males causes changes in mate choice
based on acoustic signals. T. oceanicus males produce long-range calling songs to attract females for mating, but they also produce waxy, non-volatile hydrocarbons
on their cuticle (CHCs) which, when deposited on a substrate, can be detected by females and may provide demographic information.
I manipulated female experience of substrate-bound male CHCs and then performed acoustic mate choice trials. When CHCs were
present on the substrate during trials, females showed greater motivation to respond to male calling song. This effect diminished
with repeated exposure to male songs, demonstrating that the importance of olfactory cues in altering acoustic mate choice
decreased with increasing exposure to acoustic signals. However, the temporal nature of CHC experience mattered: previous
experience of CHCs did not alter subsequent female choice for male calling song traits. Exposure to male song increased the
threshold of mate acceptance over time, and individuals varied considerably in overall levels of responsiveness. Taken together,
the results demonstrate that mate choice is dependent on social context mediated by multiple modalities in T. oceanicus, but they do not support the idea that prior experience of social cues in one modality necessarily influences later mating
decisions based on other signalling modalities. 相似文献
18.
D. Kelly McLain 《Behavioral ecology and sociobiology》1981,9(1):65-66
Summary Interference competition directed at soldier beetles, Chauliognathus pennsylvanicus, by four aggressive wasp species changed the mate choice of females. In the absence of wasps, females mated more frequently with males of greater weight and greater antennal scape diameter. Only in the presence of wasps did females frequently mate when they did not contain mature ova. When wasps were abundant, the proportion of beetles mating was higher. Wasps reacted aggressively toward mating beetles less frequently than toward single beetles. Therefore, females may have fed more efficiently in the presence of wasps when coupled. 相似文献
19.
The influence of wave exposure and of tidal height on mussel (Perna perna Linnaeus) population structure (size, density, biomass and adult/juvenile correlations) was examined at 18 sites along the
south coast of South Africa. Sites were classified as exposed or sheltered prior to sampling, without reference to the biota,
on the basis of aspect, topography and wave regime. A single set of samples was collected from each site during three spring
tide cycles. Adult mussels on these shores almost always attach directly to the rocks, and layering of mussels is virtually
absent. Shore height always had a strong influence on population structure, but exposure had significant effects only lower
on the shore, and almost exclusively on mussel sizes. Principal component analysis (PCA), based on size distribution data
for each population, revealed a general upshore decrease in the modal size of the adult cohort. The effects of exposure on
size distribution, however, varied with tidal height. PCA separated exposed zones, with larger mussels, from sheltered zones
on the low-shore. Farther upshore the two shore types were increasingly confounded. The maximum size of mussels showed a similar
pattern, with significant differences (ANOVA, p < 0.05) between exposed and sheltered sites only on the low- and mid-shores. Density was calculated from randomly placed
quadrats (i.e. not necessarily from areas of 100% cover) and showed a different pattern. Adult (>15 mm) densities decreased
up the shore, with low-, mid- and high-shore zones being significantly different from one another (ANOVA, p < 0.0001; followed by multiple range tests). However, exposure had no significant effect on density, nor was there a significant
interaction with zone. Recruit (<15 mm) densities were positively correlated with adult (>15 mm) densities in all zones and
for both exposure regimes ( p < 0.05 in all cases), but there was considerable variability and extremely low predictability in these relationships (r
2 generally <0.2). Predictability tended to be greater towards the high-shore, where adults were more clumped. As with density,
biomass was not affected by exposure, but decreased upshore as mean size and density decreased. A reduction in the influence
of exposure farther upshore may be caused by greater emersion overriding the effects of exposure. The presence of free space
within mussel beds and significant correlations between recruit and adult densities suggest that these mussel populations
are recruit limited.
Received: 7 January 2000 / Accepted: 6 July 2000 相似文献
20.
Temporal variance reverses the impact of high mean intensity of stress in climate change experiments 总被引:1,自引:0,他引:1
Extreme climate events produce simultaneous changes to the mean and to the variance of climatic variables over ecological time scales. While several studies have investigated how ecological systems respond to changes in mean values of climate variables, the combined effects of mean and variance are poorly understood. We examined the response of low-shore assemblages of algae and invertebrates of rocky seashores in the northwest Mediterranean to factorial manipulations of mean intensity and temporal variance of aerial exposure, a type of disturbance whose intensity and temporal patterning of occurrence are predicted to change with changing climate conditions. Effects of variance were often in the opposite direction of those elicited by changes in the mean. Increasing aerial exposure at regular intervals had negative effects both on diversity of assemblages and on percent cover of filamentous and coarsely branched algae, but greater temporal variance drastically reduced these effects. The opposite was observed for the abundance of barnacles and encrusting coralline algae, where high temporal variance of aerial exposure either reversed a positive effect of mean intensity (barnacles) or caused a negative effect that did not occur under low temporal variance (encrusting algae). These results provide the first experimental evidence that changes in mean intensity and temporal variance of climatic variables affect natural assemblages of species interactively, suggesting that high temporal variance may mitigate the ecological impacts of ongoing and predicted climate changes. 相似文献