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941.
Spatial and temporal genetic homogeneity in the Arctic surfclam (<Emphasis Type="Italic">Mactromeris polynyma</Emphasis>) 总被引:1,自引:0,他引:1
Commercially harvested marine bivalve populations show a broad range of population-genetic patterns that may be driven by
planktonic larval dispersal (gene flow) or by historical (genetic drift) and ecological processes (selection). We characterized
microsatellite genetic variation among populations and year classes of the commercially harvested Arctic surfclam, Mactromeris polynyma, in order to test the relative significance of gene flow and drift on three spatial scales: within commercially harvested
populations in the northwest Atlantic; among Atlantic populations; and between the Atlantic and Pacific oceans. We found small
nonsignificant genetic subdivision among eight populations from the northwest Atlantic (F
ST = 0.002). All of these Atlantic populations were highly significantly differentiated from a northeast Pacific population
(F
ST = 0.087); all populations showed high inbreeding coefficients (F
IS = 0.432). We tested one likely source of heterozygote deficits by aging individual clams and exploring genetic variation
among age classes within populations (a temporal Wahlund effect). Populations showed strikingly different patterns of age
structure, but we found little differentiation among age classes. In one case, we were able to analyze genetic diversity between
age classes older or younger than the advent of intensive commercial harvesting. The results generally suggest spatially broad
and temporally persistent genetic homogeneity of these bivalves. We discuss the implications of the results for the biology
and management of surfclam populations.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
942.
Carlos Toledo-Hernández Alberto M. Sabat Anabella Zuluaga-Montero 《Marine Biology》2007,152(3):527-535
Gorgonia ventalina’s density, size structure and lesion prevalence was measured at six sites in Puerto Rico that exhibited variation in horizontal
water transparency, sedimentation rates, suspended particle matter, scleractinian and macroalgal cover. G. ventalina density varied significantly among sites (between 0.84 and 0.007 colonies/m2), and was positively correlated with water transparency. Size structure did not vary much among sites, and reflects high
mortality among the smaller size classes and high survivorship in large colonies. Prevalence of active fungi-induced lesions
(type I) did not vary significantly among sites and was density-independent. However, prevalence of old lesions of unknown
origin (type II) did vary among reefs and was negatively correlated with water transparency. Prevalence of types I or II lesions
was independent of colony size. Our results suggest that (1) turbidity and sedimentation are important abiotic factors controlling
the abundance of sea fans, (2) variation in settlement success and early survivorship of recruits has more impact on the sea
fan populations than variation in the survivorship of large colonies and (3) prevalence of aspergillosis (type I) at the studied
sites is similar to that reported for other Caribbean reefs and supports the epizootic nature of the disease and (4) lesions
with exposed skeleton are more likely to be colonized by fouling organisms at impacted reefs. The combined effects of anthropogenic
impacts and aspergillosis may cause local extinctions of sea fans, as is becoming evident in many reefs in Puerto Rico. 相似文献
943.
We used microsatellite genetic markers to investigate adult population structure and the formation of a new year-class in
Sebastes mystinus (blue rockfish). Since S. mystinus may live as long as 45 years and reach reproductive age at approximately 5 years, the adult population may contain as many
as eight generations of reproductive adults. We investigated whether the juveniles of the 2000 year-class and the adult population
were genetically homogeneous along the California coast. We sampled approximately 100 juveniles from three sites, two sites
along the Monterey Peninsula (Carmel and Monterey) in central California and one at Fort Ross in northern California, and
approximately 50 adult S. mystinus from five sites throughout the population center. The adult sampling spanned approximately 700 km from the northern Channel
Islands to Fort Bragg. The juveniles showed significant heterogeneity in allele frequencies among distant locations and genetic
homogeneity among adjacent locations. In contrast, the adults showed genetic homogeneity over large distances (San Miguel
Island to Fort Bragg), indicating little limitation of gene flow in this region. Allele frequencies of juveniles differed
from adult samples and in some cases reduced genetic diversity indicative of sweepstakes recruitment (small sample of the
adult reproductive potential). The genetic structure of the 2000 year-class suggests that despite a genetically homogenous
adult population, settled juveniles can be genetically heterogeneous along the California coast. The results also suggest
that the adults, with several year-classes, are capable of maintaining a panmictic population despite the genetic distinctiveness
of individual year-classes. 相似文献
944.
A regression tree-based method for integrating land-cover and land-use data collected at multiple scales 总被引:1,自引:0,他引:1
As data sets of multiple types and scales proliferate, it will be increasingly important to be able to flexibly combine them
in ways that retain relevant information. A case in point is Amazonia, a large, data-poor region where most whole-basin data
sets are limited to understanding land cover interpreted through a variety of remote sensing techniques and sensors. A growing
body of work, however, indicates that the future state of much of Amazonia depends on the land use to which converted areas
are put, but land use in the tropics is difficult to assess from remotely sensed data alone. An earlier paper developed new
snapshots of agricultural land use in this region using a statistical fusion of satellite data and agricultural census data,
an underutilized ancillary data source available across Amazonia. The creation of these land-use maps, which have the spatial
detail of a satellite image and the attribute information of an agricultural census, required the development of a new statistical
technique for merging data sets at different scales and of fundamentally different data types. Here we describe and assess
this nonlinear technique, which reinterprets existing land cover classifications by determining what categories are most highly
related to the polygon land-use data across the study area. Although developed for this region, the technique appears to hold
broad promise for the systematic fusion of multiple data sets that are closely related but of different origins.
The figures in the printed version of this article appear in black and white. Color figures are available from the author
upon request. 相似文献
945.
Sperm competition occurs when the sperm of two or more males compete to fertilize the egg/s of a particular female. Males
of some species respond to a high risk of sperm competition by increasing the number of sperm in their ejaculates. Males may
accomplish such a response by increasing the intensity or duration of contraction of the cauda epididymidis and vas deferens.
During emission (first phase of the ejaculatory process), the vas deferens receives sperm from the cauda epididymidis and
propels the sperm to the urethra. In this paper, we tested the hypothesis that males exposed to a high risk of sperm competition
mobilize larger numbers of sperm from the cauda epididymidis to the vas deferens before initiation of copulatory behavior.
This accumulation of sperm in the vas deferens would result in a larger number of sperm in the ejaculate. To test this hypothesis,
we exposed male meadow voles, Microtus pennsylvanicus, to either low or high risks of sperm competition using soiled bedding of conspecific individuals. At three different times
after this exposure (15, 30, or 60 min), we removed both vasa deferentia and counted the sperm within them. We found a significant
increase in sperm numbers in the vas deferens of males after 30 min of being exposed to a high risk of sperm competition.
The lower sperm numbers after 15 and 60 min of exposure suggest that the observed response is relatively slow and that sperm
mobilized to the vasa deferentia may return to the cauda epididymides if ejaculation does not occur some time after the observed
response. Our results indicate that the physiological response that may result in high sperm numbers in the ejaculate in relation
to high risk of sperm competition can occur before initiation of copulatory behavior. 相似文献
946.
947.
László Z. Garamszegi Thorsten J. S. Balsby Ben D. Bell Marta Borowiec Bruce E. Byers Tudor Draganoiu Marcel Eens Wolfgang Forstmeier Paolo Galeotti Diego Gil Leen Gorissen Poul Hansen Helene M. Lampe Stefan Leitner Jan Lontkowski Laurent Nagle Erwin Nemeth Rianne Pinxten Jean-Marc Rossi Nicola Saino Aurélie Tanvez Russell Titus János Török Els Van Duyse Anders P. Møller 《Behavioral ecology and sociobiology》2005,57(4):305-317
Repertoire size, the number of unique song or syllable types in the repertoire, is a widely used measure of song complexity in birds, but it is difficult to calculate this exactly in species with large repertoires. A new method of repertoire size estimation applies species richness estimation procedures from community ecology, but such capture-recapture approaches have not been much tested. Here, we establish standardized sampling schemes and estimation procedures using capture-recapture models for syllable repertoires from 18 bird species, and suggest how these may be used to tackle problems of repertoire estimation. Different models, with different assumptions regarding the heterogeneity of the use of syllable types, performed best for different species with different song organizations. For most species, models assuming heterogeneous probability of occurrence of syllables (so-called detection probability) were selected due to the presence of both rare and frequent syllables. Capture-recapture estimates of syllable repertoire size from our small sample did not differ significantly from previous estimates using larger samples of count data. However, the enumeration of syllables in 15 songs yielded significantly lower estimates than previous reports. Hence, heterogeneity in detection probability of syllables should be addressed when estimating repertoire size. This is neglected using simple enumeration procedures, but is taken into account when repertoire size is estimated by appropriate capture-recapture models adjusted for species-specific song organization characteristics. We suggest that such approaches, in combination with standardized sampling, should be applied in species with potentially large repertoire size. On the other hand, in species with small repertoire size and homogenous syllable usage, enumerations may be satisfactory. Although researchers often use repertoire size as a measure of song complexity, listeners to songs are unlikely to count entire repertoires and they may rely on other cues, such as syllable detection probability.Communicated by A. Cockburn 相似文献
948.
Many deep-sea animals produce blue bioluminescence, but species of three genera of midwater dragonfishes also produce red light. In addition to numerous small body photophores, species of these genera (Malacosteus, Pachystomias and Aristostomias) have large suborbital photophores that emit red light and postorbital ones that emit blue light. Pachystomias microdon additionally has a red-emitting preorbital photophore. Fluorescence measurements from the intact suborbital photophores, and from their exposed cores, confirm the previous hypothesis that the red light emitted by Malacosteus is spectrally altered by a superficial shortwave cutoff brown filter. No such filter is present in the other two genera. Studies of the anatomy of the photophores show that the suborbital photophore of Malacosteus is similar in general organisation to other photophores, including the postorbital photophore. The red-emitting photophores of Pachystomias and Aristostomias, however, have a unique organisation, in which the bulk of the photophore comprises a gland that lies outside the thick reflector. Strands of tissue run from the gland into the photogenic core of the photophore through numerous pores in the reflector. The production and use of red light by these fishes is discussed in the context of these results.Electronic Supplementary Material Supplementary material is available for this article at 相似文献
949.
A. A. -F. A. Gab-Alla R. G. Hartnoll A. -F. Ghobashy S. Z. Mohammed 《Marine Biology》1990,107(3):417-426
A study was made from January 1988 to March 1989 of the penaid prawns in the Great Bitter Lake and Lake Timsah located in the central part of the Suez Canal. Two species of Red Sea origin were investigated,Metapenaeus stebbingi andTrachypenaeus curvirostris; the former is by far the commoner. Both species displayed seasonal breeding over the period April to October, with peaks in the early and late parts of the season.M. stebbingi had two main cohorts each year. A spring-spawned cohort survived 16 mo, and attained modal sizes of 23 mm carapare length (CL) for females and 16 to 17 mm CL for males. The autumn-spawned cohort survived 13 mo, and reached modal sizes of 20 mm and 15 mm CL for males and females, respectively. The reasons for the success ofM. stebbingi in the Canal lakes, in contrast to other Lessepsian penaeids which have flourished in the Mediterranean Sea, have been considered. The main factors are that it is essentially a shallow-water species, with excellent tolerance of salinity variations and adverse environments. However, the Canal lake populations have smaller maximum sizes, and mature earlier, than those in open seas. 相似文献
950.
The application of a multiple-recapture technique for the study of relatively small fish populations
S. Z. Rafail 《Marine Biology》1972,16(3):253-260
Expressions are given for the estimation of catchability of untagged fish using the type of multiple-recapture experiments suited to relatively small fish populations. in these experiments all captured fish are released after tagging untagged fish. The realistic assumption that fish populations suffer from different causes of mortality during the sampling surveys is adopted here. The catchability estimate for untagged fish is used to evaluate instantaneous fishing mortality, abundance, survival, instantaneous total mortality and instantaneous natural mortality rates of untagged fish. These estimates are free from Types A and B tagging errors, and take into consideration that catchabilities of tagged and untagged fish are different. 相似文献