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1.
V. J. Harriott 《Marine Biology》1998,132(2):319-325
The growth (extension rate, number of radial branches, skeletal mass, branch diameter) of the␣staghorn coral Acropora formosa (Dana, 1846) was examined at four sites on the Beacon Island platform at Houtman Abrolhos, in subtropical Western Australia
(28°S). Sites were at depths of 7 to 11 m, with variable exposure to weather and swell conditions. Two sites on the western
reef slope were partly exposed to the oceanic swell, and two sites in the lagoon were largely protected from wave action.
Linear extension rate between 1994 and 1995 varied significantly between sites, with greater linear extension at the more
protected lagoonal sites. However, accumulation of skeletal mass per branch and number of newly initiated radial branches
did not vary significantly between the sites. Carbonate was deposited in similar amounts, but either as porous, rapidly extending
branches, or as denser branches which extended more slowly. Branch extension rate over 11.5 mo ranged from a mean of 50.3 mm
(range=13 to 93 mm) at a reef slope site to a mean of 76.0 mm (range=31 to 115 mm) at a sheltered lagoonal site. Mean extension
rates were almost twice that previously reported for this species in Houtman Abrolhos (37 to 43 mm yr−1) from a shallower site where environmental conditions were apparently sub-optimal. Growth was within the range reported for
A. formosa from tropical sites, which is consistent with the relatively high calcification and reef-accretion rates recorded for Houtman
Abrolhos in geological and metabolic studies. The role of reduced coral growth-rate in limiting coral reef formation at high
latitudes remains equivocal.
Received: 19 November 1997 / Accepted: 5 May 1998 相似文献
2.
For marine organisms, decoupling between the planktonic larval stage and the benthic-associated juvenile stage can lead to
variable patterns of population replenishment, which have the potential to influence the effectiveness of marine reserves.
We measured spatial and temporal variability in larval supply and recruitment of fishes to coral reefs of different protection
levels and tested whether protection level influenced the relationship between supply and recruitment. We sampled pre-settlement
larvae and newly settled recruits from four reefs (two reserves and two non-reserves) in the Florida Keys National Marine
Sanctuary, USA. Replicate point measures of larval supply over 14 months and 17 monthly measurements of recruitment varied
significantly among months and sites. Sites with the same protection level had significantly different patterns of larval
supply as well as larval and recruit diversity, but recruitment magnitude differed only by protection level, where densities
were greater at reserves. Differences in larval supply among sites included two particularly large peaks in larval abundance
at one site, possibly associated with the observed passage of small-scale oceanographic features. To examine whether relationships
between larval supply and recruitment varied by protection level, we selected one species that was present in both the light
trap samples and the monthly recruitment surveys. Recruitment of the bicolor damselfish Stegastes partitus was significantly and positively related to larval supply at three of the four sites thus, protection level did not influence
this linkage. Since local variability among sites can lead to spatial differences in population replenishment, characterization
of larval supply and recruitment to potential marine reserve sites may help to identify optimal locations in a region and
contribute to more effective reserve design. 相似文献
3.
An allozyme survey, using starch-gel electrophoresis, was carried out on eight populations of the Antarctic nemertean worm
Parborlasia corrugatus (McIntosh, 1876) collected from locations around the South Orkney Islands, Antarctica. These populations were separated by
distances in the order of tens of kilometres. Genetic variation was estimated over 22 enzyme loci for all populations examined,
giving an observed heterozygosity of 0.142. This was much lower than the expected heterozygosity (H
e
= 0.201), and it was found that there was a significant deficiency of het‐erozygotes across four enzyme loci ( p ≤ 0.01). A more detailed examination of this deficiency of heterozygotes was undertaken for the six populations and six variable
enzyme loci for which the most complete data sets existed. A significant deficiency of heterozygotes was found at the enzyme
locus Odh-1 for four of the six populations examined ( p ≤ 0.01). Mean F
is
(0.240) indicated a significant ( p ≤ 0.01) within-population component of the heterozygote deficiency estimated for the six populations sampled, and this was
mainly due to the␣Ap-1, Odh-1 and Pgm-1 loci. The mean F
st
value (0.036) was also significant ( p ≤ 0.01), indicating a degree of genetic differentiation between populations. The observed levels of genetic differentiation
between populations of P. corrugatus and the significant heterozygote deficiencies were unexpected, because this species has been reported to have a long-lived
planktotrophic larva. It is hypothesised that recruitment of P. corrugatus in the South Orkney Islands originates from genetically distinct populations located in the Weddell Sea and to the west of
the Antarctic Peninsula. Shifts in the relative position of the Weddell Sea Front, Weddell–Scotia Confluence and Scotia Front,
relative to the South Orkney Islands, provide a mechanism for variation in the origin of recruits over time.
Received: 24 July 1997 / Accepted: 31 October 1997 相似文献
4.
Results of isozyme electrophoresis were used to explore the genetic relationships between several Mediterranean morphs of
Cerithium (Gastropoda: Prosobranchia), for which taxonomy is currently uncertain because of high intraspecific variability and low
interspecific differentiation. The large species, classically known as C. vulgatum Bruguière, 1789 was identified at four sites (two in the French Mediterranean and two in southern Spain). Two different larval
types were found in the French sites, but poecilogony could not be demonstrated. Individuals collected from harbours were
not genetically distinct from open-sea populations of classic C. vulgatum. However, a population in the Embiez lagoon (French Mediterranean) which morphologically resembles C. vulgatum did display distinct genetic traits, supporting its status as a separate species. Of the small Cerithium species usually known as C. rupestre, two sympatric species (C.“rupestre” Risso, 1826 and C. lividulum Risso, 1826) were distinguished. Genotype frequencies within the analysed populations revealed much heterozygote deficiency.
F
ST
values (fixation index measuring the effects of population subdivision) suggest a higher genetic differentiation for C. lividulum populations than for C. vulgatum populations. We assume that a high larval dispersal capability (via planktotrophy) allows a high gene flow between populations
of C. vulgatum.
Received: 24 November 1998 / Accepted: 24 September 1999 相似文献
5.
The genetic effects of larval dispersal depend on spatial scale and habitat characteristics 总被引:1,自引:0,他引:1
K. E. Parsons 《Marine Biology》1996,126(3):403-414
The intertidal gastropods Bembicium vittatum and Austrocochlea constricta, which have direct and planktonic larval development, respectively, occur sympatrically at sites across a number of islands at the Houtman Abrolhos archipelago and two harbours at Albany in Western Australia. Their distribution provide an opportunity to examine the effect of dispersal ability on levels of genetic subdivision at a number of spatial scales. F
ST
(standardised variance in allelic frequencies) values in the range 0.361 to 0.396, determined from allozyme frequencies at 12 to 13 polymorphic loci, confirm isolation of Abrolhos and Albany populations, which are separated by 900 km of coastline, in both species. Within the Abrolhos and Albany, levels of subdivision in B. vittatum were high, but similar, as indicated by F
ST
values of 0.091 and 0.090, respectively. In A. constricta, a mean value of 0.160 at the Abrolhos suggests severe restrictions to gene flow, while 0.021 at Albany indicates much stronger connections among populations. F
ST
values at the Abrolhos support previous suggestions that this archipelago favours genetic subdivision in both direct and planktonic-developing species. The Albany harbours favoured subdivision only in B. vittatum, the low values of F
ST
in A. constricta being attributed to strong mixing between the harbours, thus facilitating gene flow via planktonic larvae. The isolation of A. constricta populations at the Abrolhos can be explained in terms of highly localised recruitment, the result of limited water movement in complex intertidal habitats. The study illustrates the value of examining sympatric direct and planktonic developers in assessing the role of larval dispersal in patterns of genetic subdivision, and concludes that planktonic larvae may not promote gene flow over broad or even some fine spatial scales. 相似文献
6.
Assignment of individuals to populations based upon genetic data is an important ecological problem that requires many polymorphic
markers, often more than are available using single locus techniques. To demonstrate the utility of amplified fragment length
polymorphisms (AFLP) in studying larval dispersal and recruitment in coral populations, two sets of AFLP primers were used
to genotype colonies of the coral Agaricia agaricites Linnaeus from three widely separated geographic locations: the Bahamas (23°28′N, 75°42′W) and Key Largo, Florida (24°55′N,
80°31′W—two sites separated by 12 km) in 1995, and the Flower Garden Banks (FGB) in the Gulf of Mexico (27°55′N,93°36′W) in
1997. In addition to adult samples from each site, recruits were collected from settling plates placed on the East FGB for
1 year (1997–1998). The AFLP technique yielded 45 polymorphic markers. An analysis of molecular variance (AMOVA) showed significant
genetic differences among the four adult populations, even between the two Key Largo sites. The recruits were significantly
different from all adult populations except those from the FGB. Discriminant function analysis and the program AFLPOP were
used to assign individuals to populations. Using the adult AFLP-banding patterns to build the statistical models, both procedures
correctly assigned the majority of adults to their respective populations in simulations and assigned all but one of the recruits
to the Flower Garden population from where they were collected . The AFLP technique provides a simple and adaptable population
assignment method for studying recruitment processes in A. agaricites and other coral species.
Electronic Supplementary Material Supplementary material is available for this article at 相似文献
7.
The genetic structure of Mycedium elephantotus (Pallas, 1766) populations from three regions around Taiwan was examined using allozyme electrophoresis. Eight loci were
scored from seven enzyme systems. Seven loci were polymorphic under the 95% criterion. The high ratio of observed to expected
genotypic diversities at the collection sites (G
O:G
E=0.8 to 1.0) indicate that M. elephantotus propagates predominantly by sexual reproduction. Allele frequencies of M. elephantotus differed significantly among regions (D=0.024 to 0.256, F
ST=0.032 to 0.218, p < 0.001), while populations among collection sites within each region were homogeneous (D=0.000 to 0.015, F
ST=0.010 to 0.022, p > 0.05). Genetic differentiation between populations from southern Taiwan and the Penghu Islands is greater than that between
southern and northern Taiwan populations, although the former two regions are much closer geographically. The UPGMA dendrogram
based on Nei's unbiased genetic distance showed a clear subdivision of populations into two groupings, northern Taiwan/Penghu
Islands and southern Taiwan. A higher level of gene flow was found between M. elephantotus populations in northern Taiwan and the Penghu Islands (N
m=7.56) than that between populations in southern Taiwan and other regions (N
m=0.90 to 1.72). The pattern of genetic subdivision among regions is consistent with the pattern of ocean currents, indicating
that genetic differentiation is likely driven by surface circulation vicariance.
Received: 2 December 1997 / Accepted: 15 September 1998 相似文献
8.
The structure of the larval fish assemblages in three large estuarine systems on the KwaZulu-Natal coast of South Africa
was examined using a combination of univariate, distributional and multivariate techniques. The database was comprised of
a full annual set of larval fish samples taken from each estuarine system: Durban Harbour, Richards Bay Harbour and St Lucia
Estuary. The mean monthly densities of each species in each system were used in the species matrix, and the mean monthly values
of salinity, temperature and turbidity were used in the environmental matrix. The mean species diversity and evenness index
were significantly higher in Durban Harbour (H′ = 1.03, J′ = 0.65) than in the other two systems. The cumulative dominance curve showed that St Lucia Estuary has a high dominance
of a few species, with Richards Bay Harbour intermediate and Durban Harbour being the most diverse. Classification and MDS
(multiple-dimensional scaling) analyses of larval fish densities in all three systems grouped together into three main clusters
on the basis of system. The species similarity matrix (inverse analysis) clustered into five groups at the 25% similarity
level. The MDS analysis of the same matrix showed that the groups separated out according to the degree of estuarine association
of a species and hence habitat type. The species most responsible for system groupings were: Glossogobius callidus, Gilchristella aestuaria, Stolephorus holodon, Croilia mossambica and Gobiid 12. The “best fitting” of the environmental variables to explain the larval fish community patterns in each system
was turbidity on its own (weighted Spearman's rank correlation, ρw = 0.55). The relationship of larval densities to environmental conditions was shown to be species-specific with estuarine
species (e.g. G. callidus and G. aestuaria), having a strong positive correlation with temperature and turbidity but negative correlations with salinity. In summary,
much longer term studies with more sites within each system are needed to assess whether the larval fish assemblages are stable
or at an equilibrium (both spatially and temporally) and whether these assemblages are indicative of the relative “health”
and nursery function of the system.
Received: 28 April 1999 / Accepted: 30 May 2000 相似文献
9.
Genetic heterogeneity among adult and recruit red sea urchins, Strongylocentrotus franciscanus 总被引:1,自引:1,他引:0
Allozyme electrophoresis was used to characterize genetic variation within and among natural populations of the red sea urchin
Strongylocentrotus franciscanus. In 1995 to 1996, adult urchins were sampled from twelve geographically separated populations, seven from northern California
and five from southern California (including Santa Rosa Island). Significant population heterogeneity in allelic frequencies
was observed at five of six polymorphic loci. No geographic pattern of differentiation was evident; neighboring populations
were often more genetically differentiated than distant populations. Northern and southern populations were not consistently
distinguishable at any of the six loci. In order to assess within-population genetic variation and patterns of recruitment,
large samples were collected from several northern California populations in 1996 and 1997, and were divided into three size
classes, roughly representing large adults (>60 mm), medium-sized individuals (31 to 60 mm, “subadults”) and individuals <2 yr
of age (≤30 mm test diam, referred to as “recruits”). Comparisons of allelic counts revealed significant spatial and temporal
differentiation among size-stratified population samples. Recruit samples differed significantly from adult samples collected
at the same locale, and showed extensive between-year variation. Genetic differentiation among recruit samples was much higher
in 1997 than in 1996. Between-year differences within populations were always greater for recruits than for adults. Potential
explanations for the differentiation of recruit samples include pre- and post-settlement natural selection and high interfamily
variance in reproductive success or “sweepstakes” recruitment. Unless recruit differentiation can be attributed to an improbable
combination of strong and spatially diverse selection, such differentiation across northern California populations indicates
that the larval pool is not well mixed geographically (even on spatial scales <20 km), despite long planktonic larval duration.
Received: 6 July 1999 / Accepted: 25 January 2000 相似文献
10.
As part of a “European Sardine/Anchovy Recruitment Program” (SARP), sardine larvae (Sardina pilchardus) were sampled off the Atlantic coast of Spain through the spawning season from March to June. The larvae were analysed for
carbon and nitrogen content as a measure of nutritional condition and survival potential. There was no significant diel variation
in larval carbon content, but there was a small significant diel variation in nitrogen; the absence of a strong diel signal
in elemental composition was ascribed to the overnight retention of the gut contents. There was an increase in carbon content
with increase in body length which reached an asymptote at ∼40% carbon content at a larval length of 20 mm. It is argued that
larvae with a carbon content of <25% of body weight were nutritionally stressed, with the smaller larvae (<10 mm in length)
appearing to be more vulnerable to food limitation. Although larvae with the lowest age-specific carbon content (poorest condition)
occurred on the cruise with the lowest food availability, there was no consistent relationship between carbon content and
food availability. While the successive monthly estimates of carbon content revealed differences in potential recruitment
between months, these were not related to the birth-date distribution of the surviving juveniles.
Received: 23 November 1998 / Accepted: 3 March 1999 相似文献
11.
The endemic New Zealand echinoid, Evechinus chloroticus (Valenciennes), was sampled approximately monthly from September 1990 to October 1994 at three sites in Tory Channel, Marlborough
Sounds, New Zealand. These channel sites (outer, mid and inner) were up to 20 km from the open ocean and differed in their
shore type, exposure to wave action and macrophyte abundance. E. chloroticus showed an annual reproductive cycle at each site, with gametogenesis commencing in the late austral winter and spawning in
summer. Maximum gonad indices (reproductive potential) varied spatially, with the outer site generally having higher maximum
gonad indices than the inner site, and temporally, with maximum gonad indices occurring earlier in 3 of the 4 seasons at the
outer site than the inner site. The mid and inner sites showed much greater variation in maximum gonad indices (range 15.83
to 26.99% and 11.87 to 20.90%, respectively) than the outer site (range 19.31 to 22.95%). Reproductive output (weight of gametes
released per gram echinoid) also varied, with the different sites showing significantly different outputs in the different
years. A regression of maximum reproductive potential against reproductive output was significant ( p < 0.001), and had a positive slope with an r
2 of 0.79. While, the initiation of gametogenesis was relatively synchronous between sites and years, and is possibly cued
by increasing daylength, it progressed at different rates among populations. Spawning did show spatial and temporal variability,
occurring near the time of highest sea-surface temperatures (∼15 °C). The observed variations in reproductive cycle may be
related to small-scale variability in diet and environmental conditions. Furthermore, asynchronous spawning, variable spawning
duration, and variable reproductive output are likely to strongly influence annual recruitment variability in E. chloroticus, with different larval subpopulations contributing unequally in different years. The ecological consequences of this, both
for the ability of E. chloroticus to propagate itself in space and time and for the management of the developing E. chloroticus fishery in New Zealand, are discussed.
Received: 9 December 1998 / Accepted: 13 June 2000 相似文献
12.
To test the importance of special environments for local genetic subdivision in species with a larval phase, we examined allozyme variation among populations of the intertidal snail Austrocochlea constricta, in 18 tidal ponds in the Houtman Abrolhos Islands, Western Australia. Levels of genetic divergence between pond populations were correlated with those of parallel analyses among adjacent shore populations. However, divergence among the isolated ponds, which lack surface connection to the sea, were generally substantially higher, with an overall FST of 0.408, compared with 0.274 among the shore sites. The pond populations had less genetic variation than their shore counterparts, and the reduction of heterozygosity was correlated with the isolation of the pond population, as measured by FST. Both the degree of isolation and the reduction of heterozygosity were greater in deeper ponds, where snails can produce a local pool of larvae. In contrast, ponds that dry out frequently are less likely to allow production of local recruits, and these appear to be better connected genetically to adjacent shore populations. These patterns contrast sharply with those previously documented at the same sites for the direct-developing snail Bembicium vittatum, which shows greater isolation in ponds that are often dry. The comparison between the two species shows significant interaction between intrinsic and extrinsic impediments to gene flow, and highlights the importance of characteristics of the life history in determining which circumstances favour isolation of local populations.Electronic Supplementary Material Supplementary material is available in the online version of this article at http://dx.doi.org/10.1007/s00277-005-1553-5.Communicated by G.F. Humphrey, Sydney 相似文献
13.
Lynne Van Herwerden J. Howard Choat Stephen J. Newman Matthieu Leray Grethe Hillersøy 《Marine Biology》2009,156(8):1595-1607
Here the population genetic structure of an ecologically and economically important coral reef fish, the coral trout Plectropomus leopardus, is investigated in the context of contemporary and historical events. Coral trout were sampled from four regions (six locations)
and partial mtDNA D-loop sequences identified six populations (Fst = 0.89209, P < 0.0001): Scott Reef and the Abrolhos Islands in west Australia; the Great Barrier Reef (GBR), represented by northern and
southern GBR samples; New Caledonia and Taiwan, with Taiwan containing two genetic lineages. Furthermore, this study identified
source and sink populations within and among regions. Specifically, the northern population in west Australia (Scott Reef)
was identified, as the source for replenishment of the Abrolhos population, whilst New Caledonia was a source for recruitment
to the GBR. Based on these insights from a single mtDNA marker, this study will facilitate the development of rational management
plans for the conservation of P. leopardus populations and therefore mitigate the risk of population declines from anthropogenic influences. 相似文献
14.
Halogenated metabolites in two marine polychaetes and their planktotrophic and lecithotrophic larvae
This study investigated the occurrence and ontogenetic changes of halogenated secondary metabolites in planktotrophic and
lecithotrophic larvae and adults of two common, infaunal polychaetes, Streblospio benedicti (Spionidae) and Capitella sp. I (Capitellidae), with different life-history traits. S. benedicti contains at least 11 chlorinated and brominated hydrocarbons (alkyl halides) while Capitella sp. I contains 3 brominated aromatic compounds. These halogenated metabolites are potential defense compounds benefiting
both larvae and adults. We hypothesized that: (1) planktotrophic larvae contain halogenated metabolites because they are not
protected by adult defenses, (2) quantitative and qualitative variation of planktotrophic larval halogenated metabolites parallels
that of adults, and (3) brooded lecithotrophic larvae initiate the production of halogenated metabolites only after metamorphosis.
To address these hypotheses, volatile halogenated compounds from polychaete extracts were separated using capillary gas chromatography
and identified and quantified using mass spectrometry with selected ion monitoring. All four life stages (pre- and post-release
larvae, new recruits, adults) of both S. benedicti and Capitella sp. I contained the halogenated metabolites previously identified from adults. This is the first report of halocompounds
identified and quantified in polychaete larvae. Allocation of potential defense compounds to offspring varied as a function
of species, feeding type and developmental stage. Pre-release larvae of S. benedicti with planktotrophic development contained the lowest concentration of total halogenated metabolites (1.75 ± 0.65 ng mm−3), post-release and new recruits contained intermediate concentrations (8.29 ± 1.72 and 4.73 ± 2.63 ng mm−3, respectively), and planktotrophic adults contained significantly greater amounts (28.9 ± 9.7 ng mm−3). This pattern of increasing concentrations with increasing stage of development suggests synthesis of metabolites during
development. Lecithotrophic S. benedicti post-release larvae contained the greatest concentrations of halometabolites (71.1 ± 10.6 ng mm−3) of all S. benedicti life stages and developmental types examined, while the amount was significantly lower in new recruits (34.0 ± 15.4 ng mm−3). This pattern is consistent with a previously proposed hypothesis suggesting a strategy of reducing potential autotoxicity
during developmental transitions. Pre-release lecithotrophic larvae of Capitella sp. I contained the highest concentration of total halogenated metabolites (1150 ± 681 ng mm−3), whereas the adults contained significantly lower total amounts (126 ± 68 ng mm−3). All concentrations of these haloaromatics are above those known to deter predation in previously conducted laboratory and
field trials. As a means of conferring higher larval survivorship, lecithotrophic females of both species examined may be
expending more energy on chemical defenses than their planktotrophic counterparts by supplying their lecithotrophic embryos
with more of these compounds, their precursors, or with energy for their synthesis. This strategy appears common among marine
lecithotrophic larval forms.
Received: 14 July 1999 / Accepted: 20 January 2000 相似文献
15.
Interference competition for limited habitat or refuges is known to produce density-dependent mortality and generate patterns
of micro-habitat distribution. While in mobile species the outcome of interference at a local scale can usually be determined
from differences in body size and behavior, the population-level consequences of such interactions vary depending on rates
of settlement and recruitment at a site, which are not directly correlated to local reproductive success. Previous experimental
studies in central Chile demonstrated that interference competition for refuges is the primary factor driving microhabitat
segregation between the predatory crabs Acanthocyclus gayi and Acanthocyclus hassleri, with the latter species monopolizing galleries inside mussel beds and excluding A. gayi to rock crevices. Between April 2001 and March 2006 we quantified monthly recruitment rates in artificial collectors at 17
sites over 900 km of the central coast of Chile. Results show that recruitment rates of A. hassleri are almost two orders of magnitude lower than those of A. gayi, and that they are tightly and positively correlated among sites across the region, suggesting that at scales of kilometers
larval stages of these species are affected by similar oceanographic processes. Total crab densities per site were also positively
correlated between species and strongly associated to mussel cover, with overall low crab densities at all sites where mussel
cover was lower than about 60%. At all sites with mussel cover >60%, the ratio of A. gayi to A. hassleri density progressively decreased from recruits (2.6) to juveniles (0.5) to adults (0.04), overcoming initial differences in
recruitment rates. The relative success of the inferior competitor at sites with low mussel cover does not appear to provide
a potential mechanism favoring regional coexistence through dispersal to other sites (“mass effects”), because their densities
were lower than at sites of high mussel cover. Yet, at many sites of low mussel cover the dominant competitor is virtually
absent, allowing A. gayi to attain larger population sizes at the scale of the region. Thus, the factors limiting the dominant competitor from successfully
utilizing other microhabitats seem to be the most critical factor in promoting both local and regional coexistence between
these species. 相似文献
16.
Using a biopsy dart system, samples of skin tissue were collected from southern right whales (Eubalaena australis) in 1995 on two wintering grounds, southwest Australia (n = 20) and the Auckland Islands of New Zealand (n = 20); and on offshore feeding grounds at Latitudes 40 to 43°, south of Western Australia (n = 5). A variable section of the mitochondrial DNA control-region (289 nucleotides) was amplified and sequenced from these
45 individuals (21 males, 20 females and 4 of unknown sex), distinguishing a total of seven unique sequences (i.e. mtDNA haplotypes).
Two haplotypes were found on both wintering grounds (including a common type representing 45% of each sample), and five types
were unique to only one wintering ground. An analysis of variance adapted for molecular information revealed significant genetic
differentiation between the two wintering grounds (p = 0.017). The feeding-ground sample was too small for statistical comparison with the wintering grounds, but included two
haplotypes found only in the Auckland Islands as well as the common haplotype found on both wintering grounds. The nucleotide
diversity and differentiation of mtDNA among the right whales was similar to that among humpback whales (Megaptera novaeangliae) from the same regions (Baker et al. 1998), but haplotype diversity was significantly reduced, perhaps as a result of more
intensive hunting during the last century and continued illegal hunting during this century.
Received: 16 March 1998 / Accepted: 18 December 1998 相似文献
17.
The atherinid fish Craterocephalus capreoli Rendahl is abundant in the Houtman Abrolhos Islands, 70 km off the Western Australia coast and 250 km south of the southern limit of the range of the species along the mainland. Electrophoretic examination of 7 allozyme loci at 17 sites in the Houtman Abrolhos revealed a substantially lower level of polymorphism than found in an earlier study of the species in its mainland distribution, with many of the uncommon alleles and some common ones missing. There is a very high degree of genetic subdivision among the populations in the Houtman Abrolhos, measured by a mean F
ST
of 0.437 over a distance of 35 km. This F
ST
(standardized variance in allelic frequencies) is six times that found previously among populations along the mainland coast over distances up to 850 km. The subdivision of populations in the Houtman Abrolhos is similar within one island group on a scale up to 12 km, and between two groups that are separated by 15 km of deep water. Significant differences in allelic frequencies were found between populations from the open shore and enclosed lagoons less than 800 m apart, but the overall levels of subdivision were similar for the two types of environment. Previous work had shown high levels of genetic subdivision in the Houtman Abrolhos for a gastropod with direct development. The results for C. capreoli demonstrate that the archipelago favours subdivision even for a species with potentially much greater mobility and different life history. 相似文献
18.
Potential mechanisms for the communication of height and distance by a stingless bee, Melipona panamica 总被引:1,自引:1,他引:0
This study investigates the recruitment communication mechanisms of a stingless bee, Melipona panamica, whose foragers can evidently communicate the three-dimensional location of a good food source. To determine if the bees
communicate location information inside or outside the nest, we conducted removal experiments by training marked foragers
to one of two identical feeders and then separating these experienced foragers from potential recruits as they left the nest.
The feeders were positioned to test the communication of each dimension. The results show that recruits do not simply follow
experienced foragers to the food source. Height and distance are communicated within the nest, while direction is communicated
outside the nest. We then examined the pulsed sounds produced by recruiting foragers. While unloading food, recruiting foragers
produced several short pulses and one or more very long pulses. On average, the longest unloading pulse per performance was
31–50% longer (P ≤ 0.018) for bees foraging on the forest floor than for bees foraging at the top of the forest canopy (40 m high). While
dancing, recruiting foragers produced sound pulses whose duration was positively correlated with the distance to the food
source (P < 0.001). Dancing recruiters also produced several short sound pulses followed by one or more long pulses. The longest dance
pulse per performance was 291 ± 194 ms for a feeder 25 m from the nest and 1858 ± 923 ms for a feeder 360 m away from the
nest. The mechanism of directional communication remains a mystery. However, the direction removal experiment demonstrates
that newcomers cannot use forager-deposited scent marks for long-distance orientation (>100 m from the nest).
Received: 25 September 1997 / Accepted after revision: 31 May 1998 相似文献
19.
The sizes at which female and male western rock lobster Panulirus cygnus become mature were examined over 32 years from records at six localities along the coast of Western Australia. The size of males at maturity was estimated from a subset of these data by a morphometric and a physiological method, with both producing statistically similar results. Males were larger at first maturity than females at the same sites. For both sexes, the sizes at first maturity at each location correlated (P<0.05) with the mean annual water temperature at that location, decreasing from south to north along the mainland coast and being smallest at the offshore Abrolhos Islands. Smaller sizes at maturity were recorded for both sexes than have been published previously. One certain explanation for these differences is that management measures protecting females with ovigerous setae have distorted size compositions and the ratio of immature to mature females, thereby increasing the likelihood of capturing small mature females. However, these fishing effects cannot fully account for the progressive decline in CL50 observed over the past 20 years. Other possible hypotheses considered include increases in water temperature over this period, as well as whether this change could be consistent with a genotypic response caused by the selective removal of large lobsters combined with high exploitation rates. 相似文献
20.
Otolith microstructure and microchemistry were examined in juveniles of American (Anguilla rostrata) and European (A. anguilla) eels. Otolith increment width markedly increased from age 132 to 191 d (156 ± 18.9 d; mean ± SD) in A. rostrata and 163 to 235 d (198 ± 27.4 d; mean ± SD) in A. anguilla, both of which were coincident with drastic decreases in otolith Sr:Ca ratios, suggesting that metamorphosis from leptocephalus
to glass eel began at those ages in each species. The duration of metamorphosis was estimated to be 18 to 52 d from otolith
microstructure, for both species studied. Ages at recruitment were 171 to 252 d (206 ± 22.3 d; mean ± SD) in A. rostrata and 220 to 281 d (249 ± 22.6 d; mean ± SD) in A. anguilla. In these two species, positive linear relationships were found in ages between the beginning of metamorphosis and recruitment,
suggesting that early metamorphosing larvae recruited at younger ages. Duration of the leptocephalus stage to recruitment
in A. anguilla was about 40 d longer than that in A. rostrata. The geographical segregation between the two species in the Atlantic Ocean seems to be involved in the differences in the
duration of the leptocephalus stage (age at metamorphosis).
Received: 8 November 1999 / Accepted: 8 May 2000 相似文献