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1.
Monophylies of Neocalanus cristatus, Neocalanus plumchrus andNeocalanus flemingeri were revealed by nucleotide sequencesof mitochondrial 16S rRNA gene (410 bp) but not of nuclear 18SrDNA gene (1802 bp). Intraspecific variations in mitochondrial16S rRNA of N. cristatus collected from geographically distantregions were very low (<0.5%).  相似文献   

2.
3.
Relationships between body size and abundance in ecology   总被引:8,自引:0,他引:8  
Body size is perhaps the most fundamental property of an organism and is related to many biological traits, including abundance. The relationship between abundance and body size has been extensively studied in an attempt to quantify the form of the relationship and to understand the processes that generate it. However, progress has been impeded by the under appreciated fact that there are four distinct, but interrelated, relationships between size and abundance that are often confused in the literature. Here, we review and distinguish between these four patterns, and discuss the linkages between them. We argue that a synthetic understanding of size-abundance relationships will result from more detailed analyses of individual patterns and from careful consideration of how and why the patterns are related.  相似文献   

4.
Freshwater cyclopoid copepods exhibit at least a fivefold range in somatic genome size and a mechanism, chromatin diminution, which could account for much of this interspecific variation. These attributes suggest that copepods are well suited to studies of genome size evolution. We tested the nucleotypic hypothesis of genome size evolution, which poses that variation in genome size is adaptive due to the bulk effects of both coding and noncoding DNA on cell size and division rates, and their correlates. We found a significant inverse correlation between genome size and developmental (growth) rate in five freshwater cyclopoid species at three temperatures. That is, species with smaller genomes developed faster. Species with smaller genomes had significantly smaller bodies at 22 °C, but not at cooler and warmer temperatures. Species with smaller genomes developed faster at all three temperatures, but had smaller bodies only at 22 °C. We propose a model of life history evolution that adds genome size and cell cycle dynamics to the suite of characters on which selection may act to mold life histories and to influence the distribution of traits among different habitats.  相似文献   

5.
We investigated the impact of abiotic factors and trout density on distribution and abundance of diaptomid copepods in high-elevation lakes in North Cascades National Park Service Complex (NOCA), Washington, USA. The most common large diaptomid, D. kenai (mean length = 1.88 mm), was able to persist over a wide range of abiotic factors, but the small herbivorous diaptomid, D. tyrrelli (mean length = 1.18 mm), was restricted to shallow lakes (maximum depth < ≈ 10 m) with relatively high concentrations of total Kjeldahl nitrogen and total phosphorous. There was a significant negative relationship between the density of D. tyrrelli and the density of large diaptomids ( D. kenai and D. arcticus), which could imply interaction between large and small diaptomids. The abundance of large diaptomids was significantly lower in shallow lakes with high densities of reproducing trout (> 250 fish ha-1) than in fishless lakes, in deep lakes with reproducing trout, or in lakes where trout do not reproduce and are 0periodically stocked with fry at low densities (average 179 fry a-1). In lakes where chemical conditions were suitable for D. tyrrelli, the small diaptomid was often abundant when trout density was high and large diaptomids were either absent or in low abundance. Our research suggests that trout density, nutrient concentration, and lake depth influence the abundance of diaptomid copepods in high lakes in NOCA. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

6.
On average, large-bodied species live at lower densities than small-bodied ones. Early studies suggested that population densities might scale so that the energy use of a population is independent of body size. However, recent work shows that, at the scale of local communities, this is rarely true and that the pattern varies among taxonomic or ecological subsets of those communities. Energetic considerations may only be relevant to the densities of more abundant species. In fact, within natural assemblages o f organisms, the underlying relationship is very variable; in subsets of those assemblages, ecological processes such as competition may structure abundance patterns.  相似文献   

7.
We present a macrogeographic study of spatial heterogeneityin an important subarctic Pacific copepod and describe the firstgenetic analysis of population structure using Continuous PlanktonRecorder (CPR) samples. Samples of Neocalanus cristatus werecollected at a constant depth of 7 m from two CPR tow-routes,(i) an east–west 6500-km transect from Vancouver Island,Canada to Hokkaido Island, Japan, and (ii) a north–southtransect of 2250 km from Anchorage, Alaska to Tacoma, Washington.Analysis of these samples revealed three features of the biologyof N. cristatus. First, N. cristatus undergoes small-scale dielvertical migration that is larger among stages CV–adult(3–6 times more abundant at 7 m at night), than stagesCI–CIV (only 2–4 times higher at night). Secondly,while there were no regions where N. cristatus did not appear,each transect sampled a few large-scale macrogeographic patches.Thirdly, an analysis of molecular variation, using a partialsequence of the N. cristatus cytochrome oxidase I gene, revealedthat 7.3% (P < 0.0001) of the total genetic variation amongN. cristatus sampled from macrogeographic patches by the CPRcould be explained by spatial heterogeneity. We suggest thatspatial heterogeneity at macrogeographic scales may be importantin plankton evolution.  相似文献   

8.
9.
Patterns of sexual size dimorphism and body size in calanoid copepods are examined. We hypothesize that favorable conditions for development will result in large body size and high sexual size dimorphism among populations of a given species and that differences in this allometric relationship among species is governed by the male's role in insemination. We confirm that there is a greater advantage to large female size, normally the larger sex, when compared to males, hence leading to selection for developmental patterns favoring high size dimorphism. Individuals from populations of four centropagid copepod species were measured; other sizes were obtained from published sources. In the four species we examined, the relationships between prosome length and both clutch size and the ability to produce multiple clutches with one insemination were determined. Results show a trend toward hyperallometry in all centropagid species examined: sexual size dimorphism increases with increasing size. Large females produce larger clutches and more additional clutches on one insemination. That hyperallometry is not observed in diaptomid copepods may result from the greater role the male plays in reproduction. Males are needed for each clutch produced, hence the selective pressure to be larger is greater than that in the centropagidae.  相似文献   

10.
Charts are presented of the seasonal variations in the distributionof four phytoplankton and five zooplankton taxa in the NorthAtlantic and the North Sea. The main factors determining theseasonal variations appear to be the distribution of the mainoverwintering stocks, the current system and, in some instances,temperature control of the rate of population increase. Informationis presented about the variation with latitude (over the rangefrom 34° N to 65 ° N) of the seasonal regime of theplankton. On the assumption that there is a relationship betweennutrient supply and vertical temperature stratification themain features of this variability can be interpreted. In thesouth (to about 43° N) nutrient limitation plus grazingappear to be dominant, resulting in a bimodal seasonal cycleof phytoplankton. North of about 60° N the system appearsto be limited by the size of the phytoplankton stocks beinggrazed primarily by Calanus Finmarchicus and Euphausiacea. Inan extensive zone, from about 44° N to 60° N, it wouldappear that the spring bloom of phytoplankton is under-exploitedby grazing while in summer the zooplankton graze the daily productionof the phytoplankton, the stocks of which are probably maintainedby in situ nutrient regeneration. The implications, for at leastthis mid-latitude zone, that rates and fluxes of processes,as opposed to density dependent interactions between stocks,play a major role in the dynamics of the seasonal cycle is consistentwith previously reported observations suggesting that physicalenvironmental factors play a major role in determining year-to-yearfluctuations in the abundance of the plankton.  相似文献   

11.
12.
The central North Pacific is one of the more oligotrophic regionsof the world oceans. There the particulate organic nitrogen:cabonratio of surface waters is variable and less than the Redfieldratio of 16N:106C by atoms. The phytoplankton P/B ratio basedupon both C and N assimilation rate varied directly with theparticulate matter PON:POC ratio as did the productivity index[mg C (mg chl a)–1h–1]. At steady state the doublingtime of the phytoplankton, the turnover time of the limitingnutrient supplied via herbivore grazing, and the time for herbivoresto filter a unit volume of water would be equivalent. They appearto be of the order of 5–9 days based on present methodologyand straightforward interpretation of its results. The rate measurements involved incubation of water samples forseveral hours in bottles. In the central N. Pacific the valueswere similar using bottles of different sizes. Addition of chelatorsdid not enhance the rates implying no poisoning of the planktonby heavy metal contaminants. The observed specific activitiesof 14C and 15N of the particulate matter in the rate measurementsare inconsistent with the notion of an active, rapidly growingand recycling microplankton food web within the incubation bottlesand support the idea that phytoplankton are growing slowly.  相似文献   

13.
Species composition and relative abundance of copepods in Chilean fjords   总被引:1,自引:1,他引:1  
We studied the species composition of copepods in the fjordregion, Isla Madre de Dios, Chile during October 1979. Fifteennew records for the fjords are cited. We found the antarcticcopepod Paraeuchaeta antarctica which is consistent with earlyrecords of other antarctic zooplankters in the area. The analysisof relative abundances shows that changes in dominance occuronly among four most abundant species of copepods.  相似文献   

14.
We examined regional and latitudinal variation in fecundity and egg weight for five species of Pacific salmon ( Oncorhynchus ) along the Pacific coast of North America. Data were examined for 24 chum salmon, 15 pink salmon, 34 sockeye salmon, 44 chinook salmon, and 40 coho salmon populations from published sources, unpublished Canadian hatchery records, our own laboratory investigations, and other unpublished sources. Substantial regional variation in fecundity and egg weight was observed, with salmon on the Queen Charlotte Islands and Vancouver Island in British Columbia generally having lower fecundity and larger egg size than nearby mainland populations. The relative distance of freshwater migration to the spawning grounds generally had a marked effect on both fecundity and egg size, with populations spawning in the upper portions in the drainages of large rivers like the Fraser River in British Columbia having reduced fecundity and egg size compared with coastal spawning populations. Fecundity was generally higher and egg size generally lower in more northern populations of sockeye, chinook, and coho salmon compared with southern ones. We suggest that egg size tends to be lower in northern populations of some species as a result of increased fecundity due to their older ages at maturity and a limited amount of energy that can be expended on egg production.  相似文献   

15.
 Diel and seasonal vertical distribution, life cycle andbody allometry of Pleuromamma scutullata and Heterorhabdus tanneriwere investigated in the Oyashio region during September 1996through October 1997. Monthly samples were collected with 0.1mm mesh closing nets towed through five discrete depths betweenthe surface and  相似文献   

16.
1. Mean body mass (W) and mean numerical (N) or biomass (B) abundance are frequently used as variables to describe populations and species in macroecological and food web studies. 2. We investigate how the use of mean W and mean N or B, rather than other measures of W and/or accounting for the properties of all individuals, can affect the outcome of tests of macroecological and food web theory. 3. Theoretical and empirical analyses demonstrate that mean W, W at maximum biomass (W(mb)), W when energy requirements are greatest (W(me)) and the W when a species uses the greatest proportion of the energy available to all species in a W class (W(mpe)) are not consistently related. 4. For a population at equilibrium, relationships between mean W and W(me) depend on the slope b of the relationship between trophic level and W. For marine fishes, data show that b varies widely among species and thus mean W is an unreliable indicator of the role of a species in the food web. 5. Two different approaches, 'cross-species' and 'all individuals' have been used to estimate slopes of abundance-body mass relationships and to test the energetic equivalence hypothesis and related theory. The approaches, based on relationships between (1) log(10) mean W and log(10) mean N or B, and (2) log(10) W and log(10) N or B of all individuals binned into log(10) W classes (size spectra), give different slopes and confidence intervals with the same data. 6. Our results show that the 'all individuals' approach has the potential to provide more powerful tests of the energetic equivalence hypothesis and role of energy availability in determining slopes, but new theory and empirical analysis are needed to explain distributions of species relative abundance at W. 7. Biases introduced when working with mean W in macroecological and food web studies are greatest when species have indeterminate growth, when relationships between W and trophic level are strong and when the range of species'W is narrow.  相似文献   

17.
Acquisition of recent phytoplankton samples from JGOFS' station ALOHA andthe Climax area prompted updating and re-evaluation of 23 years offloristic data from the summer central North Pacific environment. Recurrentgroup analysis clearly shows the dichotomy between shallow and deepassociations. A new finding is that the deep flora consists of two relatedgroups of species whose abundance centers are vertically displaced from oneanother. At the Climax area, the species structure in both shallow and deepstrata persisted throughout the study period. Within each stratum,differences in rank orders of species' abundances between station ALOHA andthe Climax area are no greater than expected from physical mixingprocesses. However, abundances of species in the deeper recurrent groupswere significantly lower at ALOHA.  相似文献   

18.
Grazing rates and behaviors of the copepod Neocalanus plumchrus were investigated in shipboard experiments during the first SUPER Program cruise (May, 1984). N. plumchrus can exploit cells in the 2 to 30 m size range with equal clearance efficiency but displays considerable flexibility in responding to changes in concentration and size composition. Its functional response helps to stabilize phytoplankton at low densities. In 60-liter microcosms, a density of one copepod liter–1 was sufficient to maintain the ambient abundance and structure of the phytoplankton community for a week. In the absence of the copepod, phytoplankton bloomed to unnaturally high levels, and the community composition was dramatically altered. Despite its grazing potential, N. plumchrus was not present in sufficient density to control phytoplankton blooms in the subarctic Pacific. However, the copepod may have an important role in regulating the abundance of smaller grazers and the size structure of the phytoplankton community.Contribution No. 2002 from Hawaii Institute of Geophysics, University of Hawaii, Honolulu, HI 96822  相似文献   

19.
If common processes generate size-abundance relationships among all animals, then similar patterns should be observed across groups with different ecologies, such as parasites and free-living animals. We studied relationships among body size, life-history traits, and population intensity (density in infected hosts) among nematodes parasitizing mammals. Parasite size and intensity were negatively correlated independently of all other parasite and host factors considered and regardless of type of analyses (i.e., nonphylogenetic or phylogenetically based statistical analyses, and across or within communities). No other nematode life-history traits had independent effects on intensity. Slopes of size-intensity relationships were consistently shallow, around -0.20 on log-log scale, and thus inconsistent with the energetic equivalence rule. Within communities, slopes converged toward this global value as size range increased. A summary of published values suggests similar convergence toward a global value around -0.75 among free-living animals. Steeper slopes of size-abundance relationships among free-living animals could be related to fundamental differences in ecologies between parasites and free-living animals, although such generalizations require reexamination of size-abundance relationships among free-living animals with regard to confounding factors, in particular by use of phylogenetically based statistical methods. In any case, our analyses caution against simple generalizations about patterns of animal abundance.  相似文献   

20.
A total of 178 copepod species were identified in an upwellingarea of the Mienhua Canyon off northern Taiwan, western NorthPacific during a spring cruise in 1995. Paracalanus aculeatus,Oncaea venusta and Clausocalanus furcatus were the three dominantspecies, comprising 43% of the total copepod numbers. Most copepodspecies performed normal diel vertical migration, descendingduring daytime and ascending at night to different depth zonesand with different rates. Some dominant copepod species, suchas P. aculeatus, C. furcatus, Temora discaudata and Canthocalanuspauper, apparently congregated in the surface water (between0 and  相似文献   

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