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1.
Endemism and dispersal: comparative phylogeography of three surgeonfishes across the Hawaiian Archipelago 总被引:1,自引:0,他引:1
To evaluate the hypothesis that a general correlation exists between species range size and dispersal ability, we surveyed
mitochondrial cytochrome b sequence variation in three surgeonfish species with vastly different ranges: Ctenochaetus strigosus, Hawaiian endemic, N = 531; Zebrasoma flavescens, North Pacific, N = 560; Acanthurus nigrofuscus, Indo-Pacific, N = 305. Collections were made throughout the 2,500 km expanse of the Hawaiian Archipelago and adjacent Johnston Atoll. Analyses
of molecular variance demonstrate that all three species are capable of maintaining population connectivity on a scale of
thousands of km (all species global ΦST = NS). However, rank order comparison of pairwise ΦST results and Exact test P-values revealed modest but significantly different patterns of gene flow among the three species surveyed, with the degree
of genetic structure increasing as range size decreases (P = 0.001). These results are consistent with mtDNA surveys of four additional Hawaiian reef fauna in which a wide-spread Indo-Pacific
species exhibited genetic homogeneity across the archipelago, while three endemics had significant population subdivision
over the same range. Taken together, these seven cases invoke the hypothesis that Hawaii’s endemic reef fishes evolved from
species with reduced dispersal ability that, after initial colonization, could not maintain contact with parent populations.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
2.
The euphausiid Euphausia crystallorophias Holt and Tattersall, 1906 is considered to be a neritic species. It has been found in greatest abundance along the Antarctic
continental margins, often in association with regions of pack ice. Although E. crystallorophias has been observed at some islands to the west of the Antarctic Peninsula, the species has not previously been reported from
islands of the maritime- or sub-Antarctic further north. During an oceanographic transect in November 1997 from South Georgia
to the South Sandwich Islands, acoustic observations revealed a dense, discrete pelagic target at 50 m. The target was fished
and was found to be an aggregation of small E. crystallorophias. The fishing location (54.48°S; 30.61°W) was >1500 km from the Antarctic continent, and >250 km from the nearest land, in
water of several thousands of metres depth – clearly a non-neritic environment. Examination of hydrographic data revealed
that the E. crystallorophias swarm had been located within a fast-flowing band of water that had characteristics of water found near the Antarctic Peninsula.
This band was ≃150 km wide, and had a speed ranging from 9 to 22 km d−1 in a north-easterly direction. The possible origins of this E. crystallorophias swarm are explored in the light of the eddy-dominated current patterns prevalent in the Weddell–Scotia Confluence region,
and with reference to published growth-rate estimates for the species. We discuss the potential for long-distance dispersal
of E. crystallorophias and other neritic species in fast current jets, and examine how such oceanographic features could facilitate long-distance
dispersal, colonization, and gene flow.
Received: 23 November 1998 / Accepted: 25 March 1999 相似文献
3.
This study investigated the utility of microsatellite markers for providing information on levels of population connectivity
for a low dispersing reef fish in New South Wales (NSW), Australia, at scales ≤400 km. It was hypothesized that the temperate
damselfish Parma
microlepis, which produces benthic eggs and has limited post-settlement dispersal, would exhibit spatial genetic structure and a significant
pattern of isolation-by-distance (IBD). A fully nested hierarchical sampling design incorporating three spatial scales (sites,
location and regions, separated by 1–2, 10–50 and 70–80 km respectively) was used to determine genetic variability at seven
microsatellite loci. Broad-scale genetic homogeneity and lack of IBD was well supported by single and multi-locus analyses.
The proportion of the total genetic variation attributable to differences among regions, locations or sites was effectively
zero (Φ/R-statistics ≤0.007). The geographic distribution of genetic diversity and levels of polymorphism (H
E 0.21–0.95) indicate high mutation rates, large effective population sizes, and high rates of gene flow. Significant gene
flow may be driven by factors influencing pre-settlement dispersal, including the East Australian Current (EAC) and habitat
continuity. Genetic connectivity may not reflect demographically important connectivity, but does imply that P. microlepis populations are well connected from an evolutionary perspective. Total observed genetic diversity was accounted for within
1–2 km of reef and could be represented within small Marine Protected Areas. Reef fishes in NSW which have life histories
similar to P. microlepis (e.g. pre-settlement durations ≥2 weeks) are also likely to exhibit genetic homogeneity. Genetic markers are, therefore,
most likely to provide information on demographically relevant connectivity for species with lower dispersal capabilities,
small population sizes, short life spans, and whose habitats are rare, or patchily distributed along-shore.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
4.
Mudskippers (Gobiidae: Oxudercinae) are amphibious gobies. The occurrence and habitats of seven sympatric species of Malayan
mudskippers were recorded: Boleophthalmus
boddarti, Boleophthalmus
pectinirostris, Periophthalmodon schlosseri, Periophthalmus chrysospilos, Periophthalmus gracilis, Periophthalmus variabilis and Scartelaos histophorus. A total of 14 surveys were made at six localities along 120 km of the west coast
of the Malay Peninsula in August 1996 and September 2006. A multivariate set of ordinal parameters were used to measure the
quantity of environmental water in mudskippers’ habitats, and three guilds of species were discriminated. The resulting pattern
mirrored the adaptive scenario depicted by physiological and anatomical studies of mudskippers’ terrestriality, although in
one case a terminal taxon was less terrestrial than other more basal ones. Differentiation of trophic niches may also play
a role in habitat selection by the herbivorous Boleophthalmus spp., which were only found in unvegetated, illuminated areas and on wet mud at low tide. With the more terrestrial guild,
a significant negative co-occurrence suggested direct interspecific competition.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
5.
M. Eugenia D’Amato Gordon W. Harkins Tulio de Oliveira Peter R. Teske Mark J. Gibbons 《Marine Biology》2008,155(2):243-247
The genus Nyctiphanes (Malacostraca, Euphausiacea) comprises four neritic species that display antitropical geographic distribution in the Pacific
(N. simplex and N. australis) and Atlantic (N. couchii and N. capensis) Oceans. We studied the origin of this distribution applying methods for phylogenetic reconstruction and molecular dating
of nodes using a Bayesian MCMC analysis and the DNA sequence information contained in mtDNA 16S rDNA and cytochrome oxidase
(COI). We tested hypotheses of vicariance by contrasting the time estimates of cladogenesis with the onset of the major barriers
to ocean circulation. It was estimated that Nyctiphanes originated in the Pacific Ocean during the Miocene, with a lower limit of 18 miilion years ago (Mya). An Atlantic–Pacific
cladogenic event (95% HPD 3.2–9.6) took place after the closure of the Tethyan Sea, suggesting that dispersal occurred from
the Indo-Pacific, most likely via southern Africa. Similarly, the antitropical distribution pattern observed in the eastern
Atlantic Ocean likely resulted from recent Pliocene–Pleistocene (95% HPD 1.0–4.97) northward dispersal from the southern hemisphere.
Our results imply that dispersal appears to have had a significant role to play in the evolution of this group.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
6.
In the marine environment, connectivity is influenced by physical oceanography as well as life history and behavioral traits,
which in combination with historical events such as geology, physical oceanography, and climate, determine population structure.
The Antarctic brittle star Ophionotus victoriae develops via a feeding planktonic larval stage, and therefore has potential for long-distance dispersal throughout its Antarctic/subantarctic
range. To evaluate this hypothesis, phylogeography of this ecologically dominant species was elucidated by sequence analysis
of two mtDNA genes from individuals collected throughout the Antarctic Peninsula and from two subantarctic islands. Counter
to expectations of genetic homogeneity, mtDNA data revealed substantial levels of genetic differentiation as well as diversity.
Although there were some genetically homogeneous populations, such as those throughout Bransfield Strait, we found O. victoriae to have significant population structure throughout much of the Antarctic Peninsula, with evidence of potential cryptic speciation
between the western and eastern Antarctic Peninsula. Furthermore, Antarctic Peninsula populations were genetically distinct
from subantarctic island populations. The low levels of connectivity implied for O. victoriae contrast with those found for many other Antarctic benthic taxa, and suggest a complex interplay between oceanography, recent
climate history, and larval ecology. 相似文献
7.
Prevailing oceanographic processes, pelagic larvae, adult mobility, and large populations of many marine species often leads
to the assumption of wide-ranging populations. Applying this assumption to more localized populations can lead to inappropriate
conservation measures. The Pacific ocean perch (Sebastes alutus, POP) is economically and ecologically valuable, but little is known about its population structure and life history in Alaskan
waters. Fourteen microsatellite loci were used to characterize geographic structure and connectivity of POP collections (1999–2005)
sampled along the continental shelf break from Dixon Entrance to the Bering Sea. Despite opportunities for dispersal, there
was significant, geographically related genetic structure (F
ST = 0.0123, P < 10−5). Adults appear to belong to neighborhoods at geographic scales less than 400 km, and possibly as small as 70 km, which indicates
limited dispersal throughout their lives. The population structure observed has a finer geographic scale than current management,
which suggests that measures for POP fisheries conservation should be revisited. 相似文献
8.
We examined the isotopic signatures (δ13C, δ15N) of adult body feathers from southern giant petrels Macronectes giganteus collected at two breeding colonies in Antarctica (Potter Peninsula and Cape Geddes) and one in southern Patagonia (Observatorio
Island), as well as in whole blood collected from adults of both sexes at each Antarctic colonies and from chicks at Potter
Peninsula. As body feather moult is a continuous process in giant petrels, feathers provide an integrated annual signal of
an adult’s diets and foraging habitats. In contrast, the stable isotope values of adult and chick blood are reflective of
their diets during the breeding season. We found that sex-specific dietary segregation in adults breeding in Antarctica was
notable during the breeding season (blood samples) but absent when examined across the entire year (feather samples). In addition,
blood stable isotope values differed between chicks and adults, indicating that adults provision their offspring with a relatively
higher amount of penguin and seal prey that what they consume themselves. This finding confirms previous work that suggests
that chicks are preferentially fed with prey of presumably higher nutritional value such as carrion. Finally, based on isotopic
differences between major oceanographic zones in the Southern Ocean, our data indicate population-specific differences in
foraging distribution, with Antarctic populations move seasonally between Antarctic and subantarctic zones, while Patagonian
populations likely forage in subtropical waters and in continental shelf habitats year-round. 相似文献
9.
Yves Cherel 《Marine Biology》2008,154(5):813-821
The emperor and Adélie penguins are the only two species of penguins that co-occur at high-Antarctic latitudes. We first measured
and compared their isotopic niches on the same year in Adélie Land in spring, when the two species co-exist. Emperor and Adélie
penguins segregated by their blood isotopic signatures, with adult δ13C values (−24.5 ± 0.2 and −25.4 ± 0.2‰, respectively) suggesting that emperor penguins foraged in more neritic waters than
Adélie penguins in spring. At that time, difference in their δ15N values (4.1‰, 12.0 ± 0.4 vs. 7.9 ± 0.1‰) encompassed more than one trophic level, indicating that emperor penguins preyed
mainly upon fish (and squids), while Adélie penguins fed exclusively on euphausiids. Second, we compared the food of breeding
adults and chicks. The isotopic signatures of adults and chicks of emperor penguins were not statistically different, but
δ15N value of Adélie penguin chicks was higher than that of adults (10.2 ± 0.8 vs. 9.0 ± 0.2‰). The difference showed that adult
Adélie penguins captured higher trophic level prey, i.e. higher-quality food, for their chicks. Third, the isotopic signatures
of Adélie penguins breeding in Adélie Land showed that adults fed on Antarctic krill in oceanic waters in spring and shifted
to neritic waters in summer where they preyed upon ice krill for themselves and upon fish and euphausiids for their chicks.
A comparison of isotopic niches revealed large overlaps in both blood δ13C and δ15N values within the community of Antarctic seabirds and pinnipeds. The continuum in δ15N values nevertheless encompassed more than one trophic level (5.2‰) from Adélie penguin and crabeater seal to the Weddell
seal. Such a broad continuum emphasizes the fact that all Antarctic seabirds and marine mammals feed on varying proportions
of a few crustacean (euphausiids) and fish (Antarctic silverfish) species that dominate the intermediate trophic levels of
the pelagic neritic and oceanic ecosystems. 相似文献
10.
Rodolfo Barreiro Lucia Couceiro María Quintela José Miguel Ruiz 《Marine Biology》2006,148(5):1051-1060
Randomly amplified polymorphic DNA (RAPD) banding patterns were compared between samples of the netted dogwhelk Nassarius reticulatus from 11 locations along the NW Iberian Peninsula coast. To detect if rias (estuaries formed by drowned river valleys) might
promote genetic differentiation, five sampling sites were located within a ria (ria of Muros) and the remaining six were scattered
along open-coast areas at increasing distances from the ria mouth. Population differentiation statistics (Φ-values) were estimated
using a hierarchical analysis of molecular variance (AMOVA) with samples sorted into two groups: open-coast and ria populations.
Despite a high potential to disperse, AMOVA demonstrated a modest, statistically significant genetic heterogeneity among N. reticulatus populations. Most of the genetic structure resided in differences among open-coast populations; ria populations were genetically
homogeneous. No obvious geographical pattern was detected for the pairwise genetic distances (non-metric multidimensional
scaling; UPGMA tree; Mantel test). Unlike previous studies with other species at a variety of estuarine systems other than
rias, there was no evidence that the ria of Muros may enhance the genetic divergence of N. reticulatus populations. This discrepancy is discussed in relation to the biological features of the species (high dispersal potential
and a preference for mid-low estuarine habitat) and the strong hydrographic connectivity between ria and neighbouring off-shore
waters. 相似文献
11.
Rates of respiration and protein synthesis were measured during embryonic and larval development of Antarctic asteroids with
different life-history modes (non-feeding and feeding larvae: Acodontaster hodgsoni, Porania antarctica, Odontaster meridionalis). Patterns of respiration for these species all show an increase during embryogenesis, with subsequent maintenance of routine
respiration (“starvation resistance”), even in the absence of food for ~4 months (O. meridionalis). Fractional rates of protein synthesis (i.e., rate per unit mass of whole-body protein content) in the Antarctic larvae
are essentially identical to those of temperate species. Larvae of O. meridionalis had an average fractional synthesis rate of 0.52% ± 0.05 h−1 at −1.0°C, which is comparable to the temperate asteroid Asterina miniata at 0.53% ± 0.14 h−1 at 15°C. For embryos of the asteroids A. hodgsoni and P. antarctica, fractional rates of protein synthesis (~0.2% h−1) also are comparable to those reported for embryos of temperate echinoderm species. While rates of synthesis are high, rates
of protein deposition are relatively low (percent of protein synthesized that is retained for growth). During a ~4 month growth
period for larvae of O. meridionalis, the average protein depositional efficiency was 5.2%. This contrasts with higher rates of depositional efficiency reported
for similar developmental stages of temperate echinoderm species. The biological significance of maintaining high rates of
macromolecular synthesis for species with low rates of cell division and low protein depositional efficiencies is intriguing
in the context of understanding the mechanistic bases of extended life spans and dispersal potential in response to changing
Antarctic environments. 相似文献
12.
Andrew J. Pemberton Lars J. Hansson Sean F. Craig Roger N. Hughes John D. D. Bishop 《Marine Biology》2007,153(1):71-82
Microscale genetic differentiation of sessile organisms can arise from restricted dispersal of sexual propagules, leading
to isolation by distance, or from localised cloning. Cyclostome bryozoans offer a possible combination of both: the localised
transfer of spermatozoa between mates with limited dispersal of the resulting larvae, in association with the splitting of
each sexually produced embryo into many clonal copies (polyembryony). We spatially sampled 157 colonies of Crisia denticulata from subtidal rock overhangs from one shore in Devon, England at a geographic scale of ca. 0.05 to 130 m plus a further 21
colonies from Pembrokeshire, Wales as an outgroup. Analysis of molecular variance (AMOVA) revealed that the majority (67%)
of genetic variation was distributed among individuals within single rock overhangs, with only 16% of variation among different
overhangs within each shore and 17% of variation between the ingroup and outgroup shores. Despite local genetic variation,
pairwise genetic similarity analysed by spatial autocorrelation was greatest at the smallest inter-individual distance we
tested (5 cm) and remained significant and positive across generally within-overhang comparisons (<4 m). Spatial autocorrelation
and AMOVA analyses both indicated that patches of C. denticulata located on different rock overhangs tended to be genetically distinct, with the switch from positive to negative autocorrelation,
which is often considered to be the distance within which individuals reproduce with their close relatives or the radius of
a patch, occurring at the 4–8 m distance class. Rerunning analyses with twenty data sets that only included one individual
of each multilocus genotype (n = 97) or the single data set that contained just the unique genotypes (n = 67) revealed that the presence of repeat genotypes had an impact on genetic structuring (PhiPT values were reduced when
shared genotypes were removed from the dataset) but that it was not great and only statistically evident at distances between
individuals of 1–2 m. Comparisons to a further 20 randomisations of the data set that were performed irrespective of genotype
(n = 97) suggested that this conclusion is not an artefact of reduced sample size. A resampling procedure using kinship coefficients,
implemented by the software package GENCLONE gave broadly similar results but the greater statistical power allowed small
but significant impacts of repeat genotypes on genetic structure to be also detected at 0.125–0.5 and 4–16 m. Although we
predict that a proportion of the repeat multilocus genotypes are shared by chance, such generally within-overhang distances
may represent a common distance of cloned larval dispersal. These results suggests that closely situated potential mates include
a significant proportion of the available genetic diversity within a population, making it unlikely that, as previously hypothesised,
the potential disadvantage of producing clonal broods through polyembryony is offset by genetic uniformity within the mating
neighbourhood. We also report an error in the published primer note of Craig et al. (Mol Ecol Notes 1:281–282, 2001): loci Cd5 and Cd6 appear to be the same microsatellite.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
13.
Estimating abundance of killer whales in the nearshore waters of the Gulf of Alaska and Aleutian Islands using line-transect sampling 总被引:1,自引:0,他引:1
Alexandre N. Zerbini Janice M. Waite John W. Durban Rick LeDuc Marilyn E. Dahlheim Paul R. Wade 《Marine Biology》2007,150(5):1033-1045
Killer whale (Orcinus orca Linnaeus, 1758) abundance in the North Pacific is known only for a few populations for which extensive longitudinal data
are available, with little quantitative data from more remote regions. Line-transect ship surveys were conducted in July and
August of 2001–2003 in coastal waters of the western Gulf of Alaska and the Aleutian Islands. Conventional and Multiple Covariate
Distance Sampling methods were used to estimate the abundance of different killer whale ecotypes, which were distinguished
based upon morphological and genetic data. Abundance was calculated separately for two data sets that differed in the method
by which killer whale group size data were obtained. Initial group size (IGS) data corresponded to estimates of group size
at the time of first sighting, and post-encounter group size (PEGS) corresponded to estimates made after closely approaching
sighted groups. ‘Resident’-type (fish-eating) killer whales were more abundant than the ‘transient’-type (mammal-eating).
Abundance estimates of resident killer whales (991 [95% CI = 379–2,585] [IGS] and 1,587 [95% CI = 608–4,140] [PEGS]), were
at least four times greater than those of the transient killer whales (200 [95% CI = 81–488] [IGS] and 251 [95% CI = 97–644]
whales [PEGS]). The IGS estimate of abundance is preferred for resident killer whales because the estimate based on PEGS data
may show an upward bias. The PEGS estimate of abundance is likely more accurate for transients. Residents were most abundant
near Kodiak Island in the northern Gulf of Alaska, around Umnak and Unalaska Islands in the eastern Aleutians, and in Seguam
Pass in the central Aleutians. This ecotype was not observed between 156 and 164°W, south of the Alaska Peninsula. In contrast,
transient killer whale sightings were found at higher densities south of the Alaska Peninsula between the Shumagin Islands
and the eastern Aleutians. Only two sightings of ‘offshore’-type killer whales were recorded during the surveys, one northeast
of Unalaska Island and the other south of Kodiak Island. These are the first estimates of abundance of killer whale ecotypes
in the Aleutian Islands and Alaska Peninsula area and provide a baseline for quantifying the role of these top predators in
their ecosystem.
Electronic Supplementary Material Supplementary material is available in the online version of this article at and is accessible for authorized users.
相似文献
Alexandre N. ZerbiniEmail: |
14.
P. R. Teske F. R. G. Forget P. D. Cowley S. von der Heyden L. B. Beheregaray 《Marine Biology》2010,157(9):2029-2042
‘No-take’ marine protected areas (MPAs) are successful in protecting populations of many exploited fish species, but it is
often unclear whether networks of MPAs are adequately spaced to ensure connectivity among reserves, and whether there is spillover
into adjacent exploited areas. Such issues are particularly important in species with low dispersal potential, many of which
exist as genetically distinct regional stocks. The roman, Chrysoblephus laticeps, is an overexploited, commercially important sparid endemic to South Africa. Post-recruits display resident behavior and
occupy small home ranges, making C. laticeps a suitable model species to study genetic structure in marine teleosts with potentially low dispersal ability. We used multilocus
data from two types of highly variable genetic markers (mitochondrial DNA control region and seven microsatellite markers)
to clarify patterns of genetic connectivity and population structure in C. laticeps using samples from two MPAs and several moderately or severely exploited regions. Despite using analytical tools that are
sensitive to detect even subtle genetic structure, we found that this species exists as a single, well-mixed stock throughout
its core distribution. The high levels of connectivity identified among sites support the findings of previous studies that
have indicated that inshore MPAs are an adequate tool for managing overexploited temperate reef fishes. Even though dispersal
of adult C. laticeps out of MPAs is limited, the fact that the large adults in these reserves produce exponentially more offspring than their
smaller counterparts in exploited areas makes MPAs a rich source of recruits. We nonetheless caution against concluding that
the lack of structure identified in C. laticeps and several other southern African teleosts can be considered to be representative of marine teleosts in this region in general.
Many such species are represented in more than one marine biogeographic province and may be comprised of regionally adapted
stocks that require individual management. 相似文献
15.
Nicholas D. Higgs Adam J. Reed Rachel Hooke David J. Honey Olaf Heilmayer Sven Thatje 《Marine Biology》2009,156(5):1073-1081
We present information on the reproductive biology, population structure, and growth of the brooding Antarctic bivalve Adacnarca nitens Pelseneer 1903, from the Ross Sea, Antarctica. Individuals ranging from 0.85 to 6.00 mm were found attached to a hydrozoan colony. This
species shows low fecundity and large egg size, common to other brooding species. The minimum size at which oogenesis was
detected was 2.3 mm and the minimum size at which brooding was evident was 3.9 mm. Embryos of a full range of developmental
stages were brooded simultaneously in females. The population showed a log–normal distribution and results suggest non-periodic
reproduction with continuous embryonic development. The reproductive traits of A. nitens are discussed in the context of circum-Antarctic species distribution and limitations to dispersal in brooding benthic invertebrates. 相似文献
16.
Life-history characteristics exert a profound influence upon the population structure of many marine organisms. However, relatively
few genetic studies have compared direct with indirect-developing species in the same ecosystem or geographical region, and
none to our knowledge within an Antarctic setting. To address this issue, we have collected novel amplified fragment length
polymorphism (AFLP) data from the direct-developing top shell Margarella antarctica to form a comparison with previously published data for the broadcast-spawning Antarctic limpet Nacella concinna. We scored 270 loci in 240 M. antarctica individuals sampled from five populations spanning the full length of the Antarctic Peninsula. Profound differences were
identified in the strength and pattern of population structure between the two species, consistent with gene flow being highly
restricted in M. antarctica relative to N. concinna. 相似文献
17.
Zooplankton community structure across an eddy-generated upwelling band close to a tropical bay-mangrove ecosystem 总被引:2,自引:0,他引:2
M. Rakhesh A. V. Raman C. Kalavati B. R. Subramanian V. S. Sharma E. Sunitha Babu Nanduri Sateesh 《Marine Biology》2008,154(6):953-972
Mesoscale eddies in the world’s oceans are ubiquitous and bring about episodic pulses of nutrients into the photic zone. Transient
in nature, the role of eddy pumping in coastal enrichment via plankton production, and subsequent organic flux is not yet
fully realised. In the context of a cyclonic cold-core eddy that propagates annually under the influence of the East India
Coastal Current and enriches coastal waters in the western Bay of Bengal north of 16°N, a detailed study on zooplankton community
structure along with phytoplankton composition and associated water quality was undertaken during April–May 2002 coinciding
with the spring intermonsoon. Zooplankton samples were collected at 32 hydrographically different (salinity 24.5–35.6 PSU)
GPS fixed locations representing bay-mangrove areas and nearshore waters (30 m) close to the River Godavari, which is one
of India’s largest estuarine systems. During the study, the bay-coastal waters were typified by elevated nutrient levels (nitrate
10.73–22.04 μM), high salinity (27.98–35.52 PSU), and relatively low temperatures (30.63–31.40°C). Altogether, 95 zooplankton
taxa were encountered with copepods forming the predominant population. Agglomerative Hierarchical Cluster Analysis (AHCA)
and Non-metric Multidimensional Scaling (NMDS) based on Bray–Curtis similarity (PRIMER) analysis revealed appreciable alterations
in zooplankton structure across bay-mangrove locations and coastal waters (Stress 0.11; ANOSIM test Global R: 0.94, P = 0.1%). Similarity Percentage (SIMPER) analysis revealed zooplankton associations through “discriminating species” for each
location (Kakinada Bay, Cluster I, 27.9 ± 3.0 PSU; upwelling band, cluster II, 35.5 ± 0.2 PSU; offshore waters, cluster III,
34.2 ± 0.4 PSU; mangrove outlets, cluster IV, 32.7 ± 1.3 PSU and mangrove creeks, cluster V, 33.5 ± 0.6 PSU). The index of
multivariate dispersion (IMD) illustrated high variability in zooplankton standing stock for mangrove/sea locations relative
to the bay. Concurrent observations on phytoplankton revealed the importance of diatoms (r: 0.640, P ≤ 0.05). Within the eddy-generated band of upwelled water, a significant top-down control of diatoms by herbivorous zooplankton
resulted in a comparative increase in abundance of dinophyceans. Based on zooplankton abundance data and species association
patterns, it was possible to distinguish different zooplankton/copepod communities in accordance with mesoscale variability
in physical, chemical and biological processes under tropical conditions. This was confirmed through canonical correspondence
analysis (CCA) that represented coastal-offshore waters and the Bay environment in this area. 相似文献
18.
Heterospecific matings are generally assumed to be unconditionally disadvantageous due to reduced viability or fertility of
hybrid offspring. For female collared flycatchers (Ficedula albicollis) mated to male pied flycatchers (Ficedula hypoleuca), the cost of heterospecific pair formation is reduced due to high levels of conspecific extra-pair paternity and a male-biased
offspring sex ratio. In order to investigate whether these cost-reducing mechanisms are the result of female mating strategies,
rather than being a by-product of species incompatibilities, we manipulated the plumage of male collared flycatchers before
pair formation to make them resemble male pied flycatchers. Since species incompatibilities are absent in this design, any
systematic effect of manipulation on sex ratio or paternity would indicate a role of female mating strategy. Paternity was
determined by means of a likelihood approach that controls the errors made in assigning a chick to be ‘within-pair’ or ‘extra-pair’.
Neither the sex ratio nor the male share of paternity was affected by the manipulation in a systematic manner. We therefore
conclude that our experimental data provide no support for the suggestion that female behavioural strategies are markedly
adjusted in response to formation of mixed-species pairs.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
19.
Carin Jantzen Christian Wild Mohammed El-Zibdah Hilly Ann Roa-Quiaoit Christoph Haacke Claudio Richter 《Marine Biology》2008,155(2):211-221
Two species of giant clams, Tridacna maxima and T. squamosa, coexist in the Red Sea, but exhibit distinctly different depth distributions: T. maxima mostly occurs in shallow waters (reef flat and edge), while T. squamosa may occur down to the lower fore-reef slope. Giant clams have been described as mixotrophic, capable of both filter-feeding
and photosynthesis due to algal symbionts (zooxanthellae), therefore, observed depth preferences were investigated in relation
to possible differences in autotrophy vs. heterotrophy. This study was conducted from April to June 2004, at the reef near
the Marine Science Station, Aqaba, Gulf of Aqaba, Red Sea, and in May 2007, at a reef near Dahab, Sinai Peninsula, Egypt.
In situ measurements using a submersible pulse amplitude modulated fluorometer (Diving PAM), revealed no significant differences
in effective PSII quantum yield (ΔF/Fm′) and relative electron transport rates (ETR) between the two species; but rapid light curves (ETR vs. light, photosynthetically
active irradiance, PAR) showed significant differences in maximum photosynthetic rates (ETRmax), with 20% higher values in T. maxima. Chamber incubations displayed higher net and gross oxygen production by T. maxima (88.0 and 120.3 μmol O2 cm−2 mantle area day−1) than T. squamosa (56.7 and 84.8 μmol O2 cm−2 mantle area day−1); even under shading conditions (simulated depth of 20 m) T. maxima still achieved 93% of the surface gross O2 production, whereas T. squamosa reached only 44%. A correlation was found between ETR and net photosynthesis measured as oxygen production (T. maxima: R
2 = 0.53; T. squamosa: R
2 = 0.61). Calculated compensation depth (CD) (gross photosynthesis equals respiration) in T. maxima (16 m) matches the maximum depth of occurrence in this study (17 m). By contrast, the CD of T. squamosa (9 m) was much shallower than the maximum vertical range (42 m). Findings suggest T. maxima is a strict functional photoautotroph limited by light, whereas T. squamosa is a mixotroph whose photoautotrophic range is extended by heterotrophy.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
20.
Heterogeneity in the photoprotective capacity of three Antarctic diatoms during short-term changes in salinity and temperature 总被引:1,自引:0,他引:1
The Antarctic marine ecosystem changes seasonally, forming a temporal continuum of specialised niche habitats including open
ocean, sea ice and meltwater environments. The ability for phytoplankton to acclimate rapidly to the changed conditions of
these environments depends on the species’ physiology and photosynthetic plasticity and may ultimately determine their long-term
ecological niche adaptation. This study investigated the photophysiological plasticity and rapid acclimation response of three
Antarctic diatoms—Fragilariopsis cylindrus, Pseudo-nitzschia subcurvata and Chaetoceros sp.—to a selected range of temperatures and salinities representative of the sea ice, meltwater and pelagic habitats in the
Antarctic. Fragilariopsis cylindrus displayed physiological traits typical of adaptation to the sea ice environment. Equally, this species showed photosynthetic
plasticity, acclimating to the range of environmental conditions, explaining the prevalence of this species in all Antarctic
habitats. Pseudo-nitzschia subcurvata displayed a preference for the meltwater environment, but unlike F. cylindrus, photoprotective capacity was low and regulated via changes in PSII antenna size. Chaetoceros sp. had high plasticity in non-photochemical quenching, suggesting adaptation to variable light conditions experienced in
the wind-mixed pelagic environment. While only capturing short-term responses, this study highlights the diversity in photoprotective
capacity that exists amongst three dominant Antarctic diatom species and provides insight into links between ecological niche
adaptation and species’ distribution. 相似文献