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1.
Amanda D. Melin Linda M. Fedigan Chihiro Hiramatsu Shoji Kawamura 《Behavioral ecology and sociobiology》2008,62(5):659-670
Many species of platyrrhine primates are characterised by sex-linked color vision polymorphism. This presents an opportunity
to study the biology and ecology of individuals with different phenotypes living in the same group. Several evolutionary processes
could maintain polymorphic genes in populations. In this study, we evaluate the hypothesis that foraging niche divergence
among monkeys explains the presence of multiple color vision phenotypes. Specifically, we test whether dichromats and trichromats
differ in foraging time devoted to cryptic vs brightly colored resources. We did not find any differences in foraging time
spent on different food types by dichromatic and trichromatic monkeys in two groups of white-faced capuchins (Cebus capucinus) living in a tropical dry forest. We conclude that in so far as these variables are concerned, niche divergence does not
likely explain color vision polymorphism in our study population. 相似文献
2.
Physiological studies were made on the crabs Ucides cordatus (L.) and Callinectes danae sampled from populations living in “polluted” mangroves on the southeast littoral of Brazil. Analysis of Cu, Cd, Zn, and
Fe of sediments and crab tissues showed interspecific differences in tissue concentrations, and significantly higher levels
of Cu, Cd, and Zn in “polluted” populations compared to “unpolluted” crabs living in uncontaminated mangrove in the same geographical
area. Individuals of both species from the polluted site showed significantly greater capacities for regulating blood osmotic
concentrations at low salinity (9‰). However, U. cordatus showed a reduced hypo-regulatory ability in 34‰S. Differences in ionoregulation were also seen. “Polluted”C. danae showed significantly higher Na/ K-ATPase levels in posterior gills compared to “unpolluted” crabs. Oxygen consumption rates
(M˙
O2) were elevated in U. cordatus, but depressed in C. danae from the “polluted” population. Individuals of both species from this site showed significantly lower O:N ratios, mainly
because of an increased net efflux of ammonia. Adenylate energy charge (AEC) values of muscle and hepatopancreas in “unpolluted”
and “polluted” populations of both species were not significantly different. These physiological differences are discussed
in relation to the known acute physiological and metabolic effects of heavy metals in crustaceans, and interpretated in the
light of possible adaptive changes following long-term exposure to contamination.
Received: 6 August 1999 / Accepted: 22 June 2000 相似文献
3.
Nayuta Yamashita Kathryn E. Stoner Pablo Riba-Hernández Nathaniel J. Dominy Peter W. Lucas 《Behavioral ecology and sociobiology》2005,58(6):618-629
The intensity of available light is important in determining how well a diurnal animal can distinguish color. Primates with different types of color vision may exhibit behaviors that maximize visual contrast during critical activities such as feeding. We hypothesized that (1) trichromatic taxa will feed in a wide range of light conditions because color constancy permits stabilized color appearance across changes in illumination, and (2) that taxa with a high proportion of dichromatic individuals will tend to feed at higher light levels to increase color contrast. We recorded light levels during feeding bouts of seven primate taxa with varying degrees of color vision: the dichromatic Lemur catta, two polymorphic species, Propithecus v. verreauxi and Ateles geoffroyi, and the routine trichromats, Alouatta palliata, Colobus guereza, Piliocolobus badius, and Cercopithecus ascanius. Results were equivocal for our hypotheses. While routinely trichromatic taxa used varying light levels, the pattern of results did not differ from the dichromatic Lemur catta. However, polymorphic taxa not only sought the highest light, but females, which are the only individuals in polymorphic taxa that can be trichromatic, fed in higher light levels than males when eating non-green foods. This result is consistent with selection operating to maintain a balanced polymorphism in these taxa, though the connection between light levels and color vision type for the females is unclear. Our results further suggest that trichromatic vision may afford a selective advantage because it permits foraging under a greater range of light levels. 相似文献
4.
M. Thiel 《Marine Biology》2000,137(4):661-674
The population dynamics and reproductive biology of an ascidian- and a sponge-dwelling amphipod were examined. The two undescribed
amphipod species, Leucothoe“ascidicola” and L.“spongicola”, are closely related to each other, and occur in ascidians and sponges, respectively, along the Florida Atlantic coast.
L. “ascidicola” was abundant in solitary ascidians during fall 1997, disappeared during spring/early summer, and became abundant again in
September 1998. During the time when L. “ascidicola” were absent from their hosts, a copepod became a frequent inhabitant of the ascidians but disappeared again when L.“ascidicola” returned to the ascidians in September 1998. The numbers of L.“spongicola” in sponges increased substantially during spring, when high reproductive activity was observed. Following this reproductive
peak, both adult and juvenile amphipods apparently left the sponges, and during the summer amphipod numbers in the sponges
were very low. Another small amphipod species, which often co-occurred with L.“spongicola”, showed less seasonal variation and was found in sponges throughout the whole study period. The percentage of ovigerous
females per host unit was usually lower in the ascidian-dwelling than in the sponge-dwelling amphipods. In solitary ascidians,
L.“ascidicola” amphipods usually occurred in groups of several adults, yet there never was more than one ovigerous female per ascidian.
In contrast, several ovigerous L.“spongicola” females were found to cohabit in the same spongocoel. This suggests that intrasexual aggression may be stronger among reproductive
amphipod females in the ascidians than in sponges. The size distributions of juvenile cohorts indicate that juvenile L.“ascidicola” remain for relatively long time periods in the parental ascidian, where they may reach sexual maturity. In contrast, in
L.“spongicola”, only cohorts of very small juveniles could be identified, indicating that juveniles disperse shortly after emerging from
the female's brood pouch. It is concluded that extended parental care is of very short duration or does not occur in the sponge-dwelling
amphipod L. “spongicola”, possibly because fast-growing sponges with a highly branched spongocoel system do not allow long-lasting coexistence of
parent-offspring groups. In contrast, the discrete character of the solitary ascidians may enhance the potential for exclusion
of other species, resource monopolization by reproductive females, and furthermore for long-lasting extended parental care
in the ascidian-dwelling amphipod. Groups of single parents together with cohorts of large juveniles are reported in the literature
for amphipods and isopods from brachiopods, bivalves and ascidians, suggesting that these discrete biotic microhabitats may
favor the evolution of extended parental care in peracarid crustaceans.
Received: 30 July 1999 / Accepted: 8 May 2000 相似文献
5.
Within the tropical and subtropical oceans, tuna forage opportunistically on a wide variety of prey. However, little is known
about the trophic ecology of the smallest size classes which play an important role in stock assessments and fisheries management.
The foraging behavior of yellowfin tuna, Thunnus albacares (23.5–154.0 cm FL), collected from nearshore Fish Aggregating Devices (FADs) around Oahu was studied using stable isotope
and stomach contents analyses. Emphasis was placed on small juveniles. Yellowfin tuna changed their diets significantly between
45 and 50 cm forklength (ca. 1.5 kg). Smallest size classes fed on planktonic organisms inhabiting the shallow mixed layer,
primarily larval stomatopod and decapod crustaceans, whereas larger tuna fed on teleosts and adult Oplophorus gracilirostris, a vertically migrating mesopelagic species of shrimp. When interpreting the variation in prey δ
15N values, we considered both their relative trophic position and δ
15N values of the nitrogen at the base of the food web. Based on the distinct diet shift of the yellowfin tuna, demonstrated
by both isotope and stomach content analyses, we propose a critical mass threshold was reached at about 45 cm FL that enabled
sufficient endothermic capability to allow tuna to access prey dwelling in deeper, colder water. These ontogenetic changes
in foraging range and commensurate shift in diet of small tunas would affect their vulnerability to fishing pressure. 相似文献
6.
Protandry, the earlier arrival of males than females to breeding areas, is widespread in birds, but its underlying mechanisms
are far from well understood. The two, not mutually exclusive most highly supported hypotheses to explain avian protandry
postulate that it has evolved from intrasexual male competition to acquire the best territories (“rank advantage” hypothesis)
and/or to maximize the number of mates (“mate opportunity” hypothesis). We studied for two consecutive years the relative
importance of both hypotheses in a population of pied flycatchers (Ficedula hypoleuca), a territorial songbird with a mixed mating strategy. We measured territory quality using a long-term dataset on nest occupation
and breeding output, and we used molecular techniques to assess male fitness across the range of social and genetic mating
options. Territory quality was unrelated to breeding date and had no influence on extra-pair paternity or social polygynous
events. However, males breeding early increased their chances of becoming socially polygynous and/or of attaining extra-pair
paternity and, as a consequence, increased their total reproductive success. These results support the “mate opportunity”
hypothesis, suggesting that sexual selection is the main mechanism driving protandry in this population. 相似文献
7.
Bruce Lyon 《Behavioral ecology and sociobiology》2007,61(3):455-463
Hosts of avian brood parasites use a variety of defenses based on egg recognition to reduce the costs of parasitism; the most important of which is rejecting the parasitic eggs. Two basic recognition mechanisms are possible: “true recognition”, whereby hosts recognize their own eggs irrespective of their relative frequency in the clutch, and minority recognition (or “recognition by discordancy”), whereby hosts respond to the minority egg type. The mechanism of recognition has been experimentally studied in a handful of species parasitized by interspecific brood parasites, but the mechanism used in defenses against conspecific brood parasitism is unknown. I experimentally determined the mechanism of egg recognition in American coots (Fulica americana), a species with high levels of conspecific brood parasitism, egg recognition, and rejection. I swapped eggs between pairs of nests to alter frequencies of host and “parasite” eggs and then used two criteria for recognition: egg rejection and nonrandom incubation positions in the clutch. Eight of 12 nests (66%) given equal frequencies of host and parasite eggs showed evidence of true recognition. In contrast, only one of eight (12.5%) nests where host eggs were in the minority showed evidence of recognition by discordancy. The nonrandom incubation positions of parasitic eggs indicates that birds sometimes recognize parasitic eggs without rejecting them and provides a means of assessing recognition on a per nest basis in species with large clutches. Adaptive recognition without rejection may also be an important evolutionary stepping stone to the evolution of egg rejection in some taxa. 相似文献
8.
Often in colonial seabirds, all colony members are believed to defend against nest predators and experience equal nest predation
risk. However, the variation of defense behavior among members and its reproductive consequences are largely unknown. We investigated
(1) individual variation in the nest defense of breeding Black-tailed Gulls Larus crassirostris against a natural egg predator, the Jungle Crow Corvus macrorhynchos and (2) how this behavioral variation affects an individual’s own nest predation risk and that of their neighbors. Results
were compared between 2 years where crow attack levels were manipulated to average 5 and 22 times normal rates (“low” and
“high” predation risk years, respectively) by the placement of varying numbers of artificial nests containing unguarded eggs
at the perimeter of the gull colony. In both years, 23–38% of parents, mostly males, showed “aggressive” defense behavior
(strikes or chases) against crows and decoys. Other “non-aggressive” gulls showed no defense. In the year of low predation
risk, intrusion rates by crows (landing within 0.5 m of an individual gull’s nest) were similar for aggressive and non-aggressive
gulls. In the year of high predation risk, however, the rates of intrusion for aggressive gulls (4%) and for non-aggressive
gulls with an aggressive neighbor (37%) were significantly lower than for non-aggressive gulls without an aggressive neighbor
(76%). These results indicate that aggressive individuals reduce nest predation risk for themselves and conspecific neighbors
in a colonially breeding species. 相似文献
9.
Multivariate abundance data are commonly collected in ecology, and used to explore questions of “community composition”—how
relative abundance of different taxa changes with environmental conditions. In this paper, we propose a log-linear marginal
modeling approach for analyzing such compositional count data, via generalized estimating equations. This method exploits
the multiplicative nature of log-linear models for counts, by reparameterizing models that describe marginal effects on mean
abundance. This allows partitioning into “main effects” and compositional effects, which is appealing for interpretation.
We apply the proposed approach to reanalyze compositional counts of benthic invertebrates from Delaware Bay, and data of invertebrate
communities inhabiting Acacia plants in eastern Australia. In both cases we resort to a resampling approach to make inferences about regression parameters,
because the number of clusters was not large compared to cluster size. 相似文献
10.
Jonathan N. Pruitt Nicholas DiRienzo Simona Kralj-Fišer J. Chadwick Johnson Andrew Sih 《Behavioral ecology and sociobiology》2011,65(10):1987-1995
Research on consistent individual differences in behavior, or “behavioral syndromes”, continues to grow rapidly, and yet,
the aspects of behavior under consideration have remained remarkably limited. Here, we consider individual variation in consistency
of choice (termed here “choosiness”), as expressed during habitat choice. We repeatedly tested the responses of female Western
Black Widows, Latrodectus hesperus, to two cues of habitat quality: prey chemical cues and variation in web site illuminance. We estimated females’ response
by the distance they positioned themselves from (1) the source of prey chemical cues and (2) the darkest edge of our test
arena. Individuals with low variance in their responses are deemed more “choosy”, whereas individuals with high variance are
deemed less “choosy”. Generally, most females initiated web construction near the source of the prey chemical cues and tended
to place themselves in low-light conditions. However, we detected strong, repeatable differences in females’ intensity of
response, and within-individual variance of response (i.e., choosiness) was correlated across situations: females with highly
consistent responses towards cricket chemical cues also exhibited highly consistent responses towards variation in light conditions.
When deprived of food for extended periods, females were indistinguishable in their responses towards prey chemical cues,
but tended to initiate web construction in brighter lighting conditions. Food-deprived females universally exhibited higher
variance and diminished consistency in their responses (i.e., they were less choosy). Additionally, higher choosiness was
associated with greater mass loss during choice trials, suggesting choosiness is energetically costly. Our results demonstrate
that consistency of response to environmental cues is yet another element of behavior that varies among individuals and variation
in choosiness could beget speed/quality trade-offs during animal decision making. 相似文献
11.
L. Fishelson 《Marine Biology》1999,133(2):345-351
The morphology and partial cytology of a group of bacteria-related organisms from the guts of surgeonfish are described.
These gigantobacteria symbionts are encountered in the guts of various species of this fish family throughout the Indo-Pacific
region and the Red Sea. They have been tentatively grouped and placed in a “family”, Epulopiscidae, according to the first
species described, Epulopiscium fishelsoni Montgomery and Pollak, 1988. In addition to a morphological comparison between the various forms from different species of
surgeonfish, suggestions are presented with regard to their possible morphological diversification during evolutionary and
host-species specificity.
Received: 10 June 1998 / Accepted: 29 October 1998 相似文献
12.
Summary. The aim of this work was to investigate whether or not the predominant aggressive behaviour in spiders is stereotypic and
whether there is a relation with cuticular chemicals. We compared the intraspecific behaviour of adult females of Tegenaria atrica reared in isolation and grouped. Some plasticity emerges from environmental conditions and allows spiders to tolerate each
other. This switch of behaviour, in favour of “acceptance behaviour” vs. “attack”, is promoted by an increase in food resources.
Learning during ontogenesis and changes in cuticular lipids could prolong it. A pattern of 6 compounds distinguishes grouped
from solitary spiders. We hypothesize that a similar evolution could in part explain the emergence of certain communal species
of spiders.
Received 6 March 2001; accepted 22 June 2001. 相似文献
13.
Becky L. Williams Vanessa Lovenburg Christine L. Huffard Roy L. Caldwell 《Chemoecology》2011,21(3):131-141
Some pelagic marine larvae possess anti-predator chemical defenses. Occasionally, toxic adults imbue their young with their
own defensive cocktails. We examined paralarvae of the greater blue-ringed octopus (Hapalochlaena lunulata) for the deadly neurotoxin tetrodotoxin (TTX), and if present, whether TTX conferred protection to individual paralarvae.
Paralarvae of H. lunulata possessed 150 ± 17 ng TTX each. These paralarvae appeared distasteful to a variety of fish and stomatopod predators, yet
food items spiked with 200 ng TTX were readily consumed by predators. We conclude that TTX alone does not confer individual
protection to paralarvae of H. lunulata, and that they possess an alternative defense. In larger doses, tetrodotoxin is a deterrent to the predatory stomatopod Haptosquilla trispinosa (mean dose = 3.97 μg/g). This corresponds to 12–13 paralarvae per predator based on the TTX levels of the clutch we examined.
Thus, the basic assumption that individual paralarvae of H. lunulata are defended by TTX alone was disproved. Instead, functionality of TTX levels in paralarvae may arise through alternative
selective pathways, such as deterrence to parasites, through kin selection, or against predator species not tested here. 相似文献
14.
Bioluminescence spectra of shallow and deep-sea gelatinous zooplankton: ctenophores, medusae and siphonophores 总被引:3,自引:0,他引:3
We have examined the variability and potential adaptive significance of the wavelengths of light produced by gelatinous zooplankton.
Bioluminescence spectra were measured from 100 species of planktonic cnidarians and ctenophores collected between 1 and 3500 m
depth. Species averages of maximal wavelengths for all groups ranged from 440 to 506 nm. Ctenophores (41 species) had characteristically
longer wavelengths than medusae (34 species), and the wavelengths from siphonophores (25 species) had a bimodal distribution
across species. Four species each produced two different wavelengths of light, and in the siphonophore Abylopsistetragona these differences were associated with specific body regions. Light from deep-dwelling species had significantly shorter
wavelengths than light from shallow species in both ctenophores (p = 0.010) and medusae (p = 0.009). Although light production in these organisms was limited to the blue-green wavelengths, it appears that within
this range, colors are well-adapted to the particular environment which the species inhabit.
Received: 27 April 1998 / Accepted: 27 October 1998 相似文献
15.
Duccio Lambardi Francesca R. Dani Stefano Turillazzi Jacobus J. Boomsma 《Behavioral ecology and sociobiology》2007,61(6):843-851
Some social parasites of insect societies are known to use brute force when usurping a host colony, but most use more subtle
forms of chemical cheating either by expressing as few recognition cues as possible to avoid being recognized or by producing
similar recognition cues to the host to achieve positive discrimination. The former “chemical insignificance” strategy represents
a more general adaptive syndrome than the latter “chemical mimicry” strategy and is expected to be characteristic of early
evolutionary stages of social parasitism. We tested this hypothesis by experimentally analyzing the efficiency by which Acromyrmex echinatior leaf-cutting ants recognize intruding workers of the incipient social parasite Acromyrmex insinuator. The results were consistent with the parasite being “chemically insignificant” and not with the “chemical mimicry” hypothesis.
Gas chromatography–mass spectrometry analysis of cuticular hydrocarbon profiles showed that social parasite workers produce
significantly fewer hydrocarbons overall and that their typical profiles have very low amounts of hydrocarbons in the “normal”
C29–C35 range but large quantities of unusually heavy C43–C45 hydrocarbons. This suggests that the C29–C35 hydrocarbons are
instrumental in normal host nestmate recognition and that the C43–C45 compounds, all of which are dienes and thus more fluid
than the corresponding saturated compounds, may reinforce “chemical insignificance” by blurring any remaining variation in
recognition cues. 相似文献
16.
The behavioral sensitivities of five species of deep-sea crustaceans (order Decapoda: Acanthephyra curtirostris, A. smithi, Notostomus gibbosus, Janicella spinacauda and Oplophorus gracilirostris) to near-UV and blue-green light were studied during a research cruise off the coast of Hawaii in 1993. Two of the five species have electrophysiologically-measured spectral sensitivity peaks at 400 and 500 nm, while the remaining three species have a single sensitivity peak at 490 to 500 nm. In the current study, behavioral mean threshold sensitivities (defined as the lowest irradiance change to which the shrimp would give a behavioral response) were determined for tethered specimens of each species at two wavelengths, 400 and 500 nm. The mean behavioral threshold sensitivities of the two species with putative dual visual-pigment systems were approximately the same to near-UV and blue-green light, while the other three species were significantly less sensitive to near-UV vs blue-green light. Results from these experiments indicate that (1) behavioral information obtained from tethered shrimp accurately reflects their spectral sensitivity, and (2) the sensitivity of the putative dichromats to near-UV light is sufficiently low to detect calculated levels of near-UV light remaining in the down-welling field at their daytime depth of 600 m. Possible functions of this high sensitivity to short wavelength light are discussed. 相似文献
17.
Using data from electroretinogram recordings, we designed a submersible light meter with a spectral luminous efficiency comparable
to that of a vertically migrating shrimp. Using this light meter on the “Johnson Sea Link” submersible, we were able to ascend
with the isolumes (preferred light levels) associated with the sergestid and euphausiid shrimp layers. The speed of the submersible's
movement was recorded and correlated with simultaneous measurements of surface irradiance. In situ measurements of the downwelling
spectral distribution were also made with a fiber optic spectrometer. The average measured speed of the sergestid isolume
was 8.8 cm s−1, while that of the shallower euphausiid isolume was 6.7 cm s−1. These values are different from those calculated using average diffuse attenuation coefficients and surface light measurements.
This difference was due to the broadening of the spectral distribution of downwelling light above 120 m and to the variability
of the diffuse attenuation coefficients with depth. These results clearly demonstrate that when investigating the relationship
between light and vertical migration patterns, it is important that: (1) the light measurements be made in situ and (2) such
measurements take into account the spectral sensitivity of the eyes of the migrators.
Received: 7 June 2000 / Accepted: 18 November 2000 相似文献
18.
Clément Dumont Christopher M. Pearce Cathy Stazicker Yu Xin An Laurie Keddy 《Marine Biology》2006,149(2):365-378
A laboratory experiment was conducted in the winter of 2003–2004 to assess the effect of varying photoperiod regime on consumption rate, assimilation rate, absorption efficiency, and gonad development of the green sea urchin, Strongylocentrotus droebachiensis. Adult individuals were collected from the wild after they had been exposed to the ambient autumn photoperiod cue (which is the extraneous trigger thought to elicit gametogenesis in this species) and placed at ambient temperature for 12 weeks under five different photoperiod regimes: (1) 24 h light:0 h dark=“0D”, (2) 16 h light:8 h dark=“8D”, (3) 8 h light:16 h dark=“16D”, (4) 0 h light:24 h dark=“24D”, and (5) ambient photoperiod (range: 10.50–15.25 h dark). Urchins in these five treatments were fed ad libitum with bull kelp, Nereocystis luetkeana. A sixth treatment consisted of starved individuals held under 0D conditions. Various gonad factors including gonad index, percent gonad water, gonad colour (CIE lightness or L*, CIE hue or a*, and CIE chroma or b*), percent area occupation of the gonad by various cell types (nutritive phagocytes, spermatozoa, and secondary oocytes/ova), and stage of development were assessed at the beginning of the experiment and at weeks 4, 8, and 12 of the study. Consumption and assimilation rates were assessed at weeks 4 and 12 and absorption efficiency at week 12 of the experiment. Urchins were predominantly in the growing and premature stages at the beginning of the experiment, but by week 4 at least 20% of individuals in all treatments receiving food were classified as mature. Spawning occurred during all these treatments between weeks 4 and 8, as evidenced by significant decreases in spermatozoa and secondary oocytes/ova and a significant decrease in percent gonad water, but was not accompanied by major declines in gonad indices. Greater than 90% of individuals in all five of the fed treatments were in the recovering and growing stages at the end of the experiment. The 16D treatment had by far the greatest percentage of urchins in the growing stage. In contrast, individuals that were starved were predominantly in the mature stage at weeks 4, 8, and 12, with only ~30% reaching the spawning stage by the end of the experiment. Photoperiod significantly affected gonad indices at the termination of the experiment with gonad index being the highest in the 16D treatment; this was significantly greater than in the 8D and ambient treatments. Photoperiod did not significantly affect gonad percent water, gonad lightness, or gonad hue. Gonad chroma was significantly affected by photoperiod, urchins held under ambient conditions having significantly lower b* readings than individuals in any other treatment. Photoperiod had little or no affect on consumption rate, assimilation rate, or absorption efficiency. Thus, differences among treatments in regards to gonad index, gonad chroma, and stage of development cannot be attributed to variations in feeding, absorption, or assimilation. The results of this experiment indicate that once gametogenesis is initiated, photoperiod manipulation cannot prevent ultimate spawning. However, photoperiod regime can affect the rate at which urchins move through the various stages of the gametogenic cycle. Urchins placed on short days under artificial lighting (16D) moved through the spawning stage into recovering and growing stages the fastest. This photoperiod regime also produced the highest gonad index at the end of the experiment. Since the commercial urchin market prefers large gonads in the growing and premature stages (i.e. before the mature stage is reached and gonads start leaking sperm and eggs), short day-lengths under artificial lighting (16D) appear to be the best photoperiod conditions for optimizing marketability. 相似文献
19.
Common goldeneyes adjust maternal effort in relation to prior brood success and not current brood size 总被引:3,自引:0,他引:3
Parental investment theory predicts that parental effort should be related to the reproductive value of the current brood.
This depends on both the number of young and the survival prospects of each of them. Thus parents may provide more care to
larger broods either because of (1) the direct effect of brood size per se on reproductive value (the “brood size” hypothesis)
or because (2) past mortality, reflected in current brood size, predicts future mortality of the brood and hence its reproductive
value (the “brood success” hypothesis). Earlier studies have not attempted to distinguish between these alternatives. We tested
the hypotheses in the precocial, nidifugous common goldeneye Bucephala clangula, a species with uniparental female care. Maternal effort was measured as the time spent by the female in rearing the brood.
We found that brood size itself is not associated with maternal effort, but that females modify their maternal effort according
to the mortality already experienced by the brood, supporting the prediction of the brood success hypothesis. We also found
that brood mortality varied considerably between broods and that previous mortality predicts future mortality within broods,
basic assumptions of the brood success hypothesis.
Received: 30 January 1996 / Accepted after revision: 27 October 1996 相似文献
20.
The existence of “free-living” Symbiodinium that can form symbioses with hosts is implied by the presence of hosts that produce Symbiodinium-free gametes and expulsion and/or expelled symbiotic algae from host. However, it is still unclear if potentially symbiotic
Symbiodinium are found “free-living” in the coral reef environment. Sixteen Symbiodinium strains were established from samples taken from three sampling locations of coral reef sand in Okinawa, Japan. Phylogenetic
analyses of the partial large subunit ribosomal DNA (28S-rDNA) and the internal transcribed spacer of ribosomal DNA (ITS-rDNA)
conclusively showed that all 16 isolates belonged to Symbiodinium clade A sensu Rowan and Powers (1991). The lack of other Symbiodinium clades besides clade A in this study may be due to other clades not being readily culturable under culture conditions used
here. The new isolates could be phylogenetically divided into four groups, though no sequences were identical to previously
reported Symbiodinium. Two of the four groups were closely related to symbiotic Symbiodinium clade A isolated from a variety of host species. One isolate group formed a highly supported monophyly with Symbiodinium types that have previously been characterized as “free-living”. The remaining isolate group, although within clade A, was
quite divergent from other clade A Symbiodinium. These results indicate that novel diversity of free-living Symbiodinium exists in coral sand. 相似文献