ISSN:0307-692X    

DOI:10.1111/j.1442-9993.1990.tb01463.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractExperimental tests of clearly articulated hypotheses are an increasingly widespread feature of modern marine ecology. Increased use of experiments has not, however, been accompanied by increased understanding of the logical structure of falsificationist tests. Most observations can be explained by several different models or theories. To distinguish among these requires demonstration of the falsity of the consequences or predictions of incorrect models. This is best achieved by deriving from each model one or more hypotheses (predictions) about the type, form or nature of observations that should occur in some not‐yet‐examined set of circumstances. Because of logical constraints on the possibility of proving the correctness of such hypotheses, they must be inverted to form logical null hypotheses which comprise all alternative possibilities to those predicted in the hypotheses. Correctness or not of null hypotheses can then be ascertained by an appropriately designed experiment (or test), leading to unambiguous rejection or retention of the null hypotheses. The former corroborates the hypotheses and provides support for the correctness of the explanatory model for the original observations. In contrast, retention of a null hypothesis identifies an incorrect model. The growth of knowledge is thus the elimination of false models, theories and explanations.Ecological experiments usually require statistical procedures for determining whether or not null hypotheses should be retained. Construction of statistical null hypotheses (i.e. definitions of parameters of frequency distributions of test statistics) sometimes requires that these be identical to logical hypotheses (and not to the logical nulls). This leads to irrational acceptance of hypotheses and the models or theories from which they were derived. It also poses immense problems for determinations of statistical power of experiments.Ecological experiments are analysed to reveal the nature of, and linkages between, their components in relation to falsificationism, statistical procedures and the logical properties and interpretations of ecological theor

ISSN:0307-692X    

DOI:10.1111/j.1442-9993.1990.tb01464.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractThe early life of reef‐associated organisms is generally spent in the plankton. Recent evidence suggests that oceanographic processes have an important influence on the fate of early developmental forms; a surprising number of these manifest themselves as lines at the ocean surface. Lines, or slicks, are convergence zones where organic material collects. Internal waves, Langmuir circulations, topographically controlled fronts, estuarine, coastal and oceanic fronts produce linear or curvi‐linear slicks. The biological importance of these features is discussed. Slicks are ideal for investigating factors influencing meroplank

ISSN:0307-692X    

DOI:10.1111/j.1442-9993.1990.tb01465.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractThis paper reviews the use of genetic data, in combination with manipulative experimentation, to infer the mode of reproduction and the extent and directionality of dispersal for a range of Australian temperate marine invertebrates. Local populations of obligately sexually reproducing species have been inferred to be strongly interconnected by larval dispersal, over distances of thousands of kilometres. Their larvae may be subject to strong post‐settlement selection, but this selection is independent of obvious geographic or intertidal gradients. Within local populations selection may therefore result in apparently chaotic genetic patchiness which is eliminated by the effects of sexual reproduction and the widespread dispersal and mixing of the colonizing larvae of each generation. In partial contrast, local populations of species which rely on asexual reproduction for the maintenance of populations show evidence of similar larval connections, but no recent settlement of their sexually generated larvae has been demonstrated. The apparent connectedness of these populations may reflect either historical events or a more episodic pattern of settlement by sexually generated larvae. Local populations of these species are more highly differentiated as a result of the continued asexual replication of a limited number of genotypes. In one of these species, reciprocal transplantation of the clones within and among populations has revealed that resident clones can be highly locally adapted (as reflected by much higher asexual fecundity), which implies that selection is an important determinant of the composition of local populations. Nevertheless, the failure to detect continuing sexual recruitment into these populations obscures the evolutionary significance of this findin

ISSN:0307-692X    

DOI:10.1111/j.1442-9993.1990.tb01466.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractBenthic suspension feeders often occur at high densities on temperate reefs and other hard bottoms. Beeause many such organisms hayc prodigious feeding rates in the laboratory, it has often been predicted that established epifauna would deplete larval populations, thereby influencing density, spatial distribution and species eomposition at settlement. Most field manipulations of filter‐feeder density have not controlled for faetors other than larval predation that could produce the same pattern. In controlled experiments, larval predation effects are seldom observed. Intermittent feeding and small radii of predator influenee present many more opportunities for settlement than has generally been assumed. Two important faetors often foil attempts to measure predation effeets: low statistieal power due to small effect sizes, and choice of spatial scales larger than thdse where predation effeets oeeu

ISSN:0307-692X    

DOI:10.1111/j.1442-9993.1990.tb01467.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractDespite increasing recognition of the importance of larval settlement, recent models have concentrated on small and large scale hydrodynamic effects as determinants of larval settlement. Implicit in most of these discussions is the assumption that variability in larval behaviour either does not exist, or is unimportant.We present evidence that this is an inaccurate description of larval behaviour at the time of settlement. There exists considerable variation in behaviour at a number of scales, even under controlled laboratory conditions. For almost all species examined, responses to attractive and discrete stimuli were non‐uniform. The causes of variability in larval behaviour both within and between populations are largely unexplored. We suggest that variable behaviour, in response to discrete stimuli, may be a selectable trait. If so, the manifestation of such variability in individuals within a population is simply the expression of an adaptive trail. By this reasoning, differences in larval behaviour between populations are evidence for varying selective pressures. We conclude with an examination of possible consequences to a population, arising from variable larval behaviou

ISSN:0307-692X    

DOI:10.1111/j.1442-9993.1990.tb01468.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractLife history charaeters. which are generally eonsidered to be of eritieal signifteanee in evolution, consist of various pheiiotypie trails eoneerned with growth and reproduetion. Suites ot life history charaeters are frequently referred to as ‘strategies’. These are hypotheses which attempt to explain the adaptive significance of particular suites of charaeters. This paper reviews life history charaeters of species belonging to various orders of brown algae (Phaeophyeeae) and diseusses their possible adaptive, significance, together with the extent to which they are eonsistent with opportunistie, stress tolerant and biotieally eompetent strategies. In general, speeies belonging to the same order have broadly similar suites of life history charaeters and, thus, to some degree they share eomparable adaptive strategies. For example. the Laminariales, Fueales and Durvillaeales inelude a high proportion of biotieally eompetent speeies. many ofthe Dietyotales appear to be stress tolerant, and the Eetoearpales are typieally opportunistie. The two heteromorphie generations of speeies in the Seytosiphonales are viewed as having divergent strategies, the erustose stages showing a greater degree of stress toleranee than the opportunislie ereet sta

ISSN:0307-692X    

DOI:10.1111/j.1442-9993.1990.tb01469.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractRecent ecological studies have postulated some indirect effects of predation, which are thought to arise by a variety of interactions propagating through the many vertical and horizontal links in food webs. Such theoretical explanations have been invoked by some empirical studies that demonstrated surprising or unexpected results in field experiments. Studies of intertidal and subtidal portions of temperate rocky reefs provide some of the best examples of such indirect effects of predation. Rarely, however, have the actual mechanisms involved been elucidated. To do this requires independent evidence of how processes that are only indirectly linked to predation are affected by a variety of predation regimes. This paper speculates on how factors such as competition, mutualism, desiccation, wave action and variation in recruitment on seashores might interact with predation, both during and subsequent to predatory events. I present evidence from experiments with predatory whelks in New South Wales, Australia, to emphasize the plausibility of these speculations. Predation on local seashores indirectly benefited algae by removing small grazers, providing bare space for larger grazers and living space for cryptic animals, and interacted synergistically with barnacle recruitment to increase turnover of the prey population. These studies indicate the value of elucidating experimentally the mechanisms by which indirect effects are proposed to occur. Only by demonstrating that the effects work as hypothesized can they be pronounced unambiguously as particular indirect effects. Without such evidence, other possibilities (either more simple or more complex) need to he investigated.

ISSN:0307-692X    

DOI:10.1111/j.1442-9993.1990.tb01470.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractTraditionally, compared with the tropics, temperate systems are believed to: (i) have environments which are less favourable (i.e. harsher, more variable and less predictable); and (ii) support communities which are less diverse. Explanations for differences between temperate and tropical communities, including differences in diversity, generally rely on the former notion.The evidence for these ideas is, at best, equivocal. Organisms are subjected to physical stresses and disturbances on both temperate and tropical reefs. Communities on temperate reefs are not invariably less diverse than those in the tropics, at least at small spatial scales. Finally, there is as yet little evidence of genuine differences between the ecology of temperate and tropical communities.There is, however, much small‐scale, spatial patchiness in the structure of reef communities and their physical environment. This patchiness in structure may result from patchiness in biological factors (e.g. recruitment) or in the physical environment. This small‐scale variation in environmental factors may prove to be a more important determinant of community structure than the large‐scale, latitudinal trends some ecologists have been obsessed

ISSN:0307-692X    

DOI:10.1111/j.1442-9993.1990.tb01471.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractFor communities of intertidal rock surfaces, inshore soft sediments and streams, disturbance is regarded as an important community‐structuring force. Care needs to be taken in defining disturbance to avoid confusion with other processes such as predation. In the environments discussed, there have been many descriptive studies of disturbance and relatively few experimental studies. The latter have yielded interesting insights. Disturbance generates patches and thus may alter the outcome of biotic interactions, especially competition, by providing refuges for poor competitors and beleaguered prey. Between the three environments, colonization and succession differ — a difference no doubt related to the proportion of mobile versus sedentary biota in each environment. In succession on hard intertidal surfaces inhibition appears to be most important, whereas facilitation is dominant on soft sediments and tolerance is the most plausible mechanism of succession in streams. Across the three environments there are some striking similarities in the colonization dynamics of the mobile fauna. Disturbance is a key part of several hypotheses proposed to explain the regulation of community diversity, and for communities in the environments examined none of the hypotheses has been found to have general applicat

ISSN:0307-692X    

DOI:10.1111/j.1442-9993.1990.tb01472.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY