Trawling has a significant effect on the structure of marine communities, yet the ubiquity of trawling impacts makes testing
such effects difficult. This study examines trawling impacts on trophodynamics of three fishes among the Gulfs of Castellammare
and Termini Imerese (northern Sicily), the first of which has been subject to a trawling ban since 1990 that initially resulted
in an eightfold increase in total fish biomass. The Gulf of Termini Imerese remains heavily fished and was treated as a control
site. Nitrogen and carbon stable isotope data were used to assess fishing induced changes in trophic levels or source of production
supporting three demersal fish species; Mullus barbatus,Merluccius merluccius and Lophius budegassa following a control-impact approach. The exclusion of trawling resulted in only small alteration of δ15N in two of the three-three species. There were no systematic changes in the δ13C of any species sampled. Thus, a large influence of trawling on the trophodynamics of the studied species at sampled size
was discounted. Although stable isotopes do not have spatial or temporal resolution to identify detailed shifts in diet composition,
their integrative nature highlights that the trophic role these species play is robust to fishing impacts at scales over which
the fishery operates. This is despite a significant increase in the abundance of these species and of total fish biomass within
the protected area.
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
There is growing evidence that the sex ratios of wild vertebrate populations are determined by mechanisms that are directly
influenced by environmental characteristics. The Trivers–Willard (TWH) and extrinsic modification (EMH) hypotheses postulate
differing determinants of mammalian offspring sex ratios. TWH states that mothers allocate resources according to their current
condition and sex-specific offspring costs. EMH states that environmental forces that affect maternal condition determine
offspring sex ratios, independently of maternal tactics of sex-biased allocation. We statistically assessed support for each
of these hypotheses using long-term life histories of the allied rock-wallaby, Petrogale assimilis; a continuously breeding, polygynous, weakly dimorphic marsupial. We showed that birth sex ratios were equal and independent
of maternal and environmental conditions. However, secondary sex ratios were male-biased under good environmental conditions
and for high quality mothers or mothers in good condition. Sex differences in offspring survival contributed to these biases:
(1) environmental conditions strongly influenced survival to pouch emergence (in support of EMH) and (2) maternal quality
affected survival to the end of maternal care (in support of TWH). Environmental effects on survival were more important than
maternal factors over the entire period of maternal care and contributed most to male-biased sex ratios at pouch emergence.
In contrast, maternal mass was the best predictor of sex ratios at the end of maternal care—the life history stage where offspring
body mass differed between the sexes. 相似文献
Some authors have proposed that homing pigeons are able to correct the error in orientation following a phase-shift treatment
by using the magnetic compass reference. They reported that clock-shifted pigeons bearing magnets display a greater deflection
compared to magnetically unmanipulated clock-shifted birds. However, this hypothesis tested by recording pigeons’ vanishing
bearings has led to contradictory results. The present study reports pigeons’ tracks recorded with a GPS and shows that clock-shifted
pigeons bearing magnets displayed a greater deviation through the whole route compared to the magnetically unmanipulated shifted
pigeons. Moreover, the analysis of the tracks shows that the birds belonging to both experimental groups stop in coincidence
with their subjective night. When re-starting their journey, the birds corrected the clock-shift induced error in orientation,
but the magnetically manipulated pigeons were less efficient in doing so. Our results are consistent with the hypothesis that
homing pigeons released from unfamiliar location re-orient after clock shift by using the magnetic compass. 相似文献
Ocean acidification (OA) and the biological consequences of altered seawater chemistry have emerged as a significant environmental
threat to healthy marine ecosystems. Because a more acidic ocean interferes with fixation of calcium carbonate to form shells
or calcified skeletons, future ocean chemistry may significantly alter the physiology of calcifying marine organisms. These
alterations may manifest themselves directly in the calcification process, or have synergistic effects with other environmental
factors such as elevated temperatures. New tools permit us to explore subtle changes in gene expression patterns in response
to environmental conditions. We raised sea urchins (Strongylocentrotus franciscanus) under conditions simulating future atmospheric CO2 levels of 540 and 970 ppm. When larvae raised under elevated CO2 conditions were subjected to 1-h acute temperature stress, their ability to mount a physiological response (as measured by
expression of the molecular chaperone hsp70) was reduced relative to those raised under ambient CO2 conditions. These results represent the first use of gene expression assays to study the effects of OA on sea urchin development.
They highlight the importance of looking at multiple environmental factors simultaneously as this approach may reveal previously
unsuspected biological impacts of atmospheric changes. 相似文献
We show the potentiality of coupling together different compound-specific isotopic analyses in a laboratory experiment, where 13C-depleted leaf litter was incubated on a 13C-enriched soil. The aim of our study was to identify the soil compounds where the C derived from three different litter species is retained. Three 13C-depleted leaf litter (Liquidambar styraciflua L., Cercis canadensis L. and Pinus taeda L., δ13CvsPDB ≈ ?43‰), differing in their degradability, were incubated on a C4 soil (δ13CvsPDB ≈ ?18‰) under laboratory-controlled conditions for 8 months. At harvest, compound-specific isotope analyses were performed on different classes of soil compounds [i.e. phospholipids fatty acids (PLFAs), n-alkanes and soil pyrolysis products]. Linoleic acid (PLFA 18:2ω6,9) was found to be very depleted in 13C (δ13CvsPDB ≈ from ?38 to ?42‰) compared to all other PLFAs (δ13CvsPDB ≈ from ?14 to ?35‰). Because of this, fungi were identified as the first among microbes to use the litter as source of C. Among n-alkanes, long-chain (C27–C31) n-alkanes were the only to have a depleted δ13C. This is an indication that not all of the C derived from litter in the soil was transformed by microbes. The depletion in 13C was also found in different classes of pyrolysis products, suggesting that the litter-derived C is incorporated in less or more chemically stable compounds, even only after 8 months decomposition. 相似文献
Russian Journal of Ecology - Changes in the distribution of broadleaf tree species—Tilia cordata Mill., Quercus robur L., Acer platanoides L., and Ulmus glabra Huds.—in the central part... 相似文献
In this study, farmland and mining ecotypes of Solanum photeinocarpum (a potential cadmium (Cd) hyperaccumulator plant) were reciprocally hybridized each other, and the Cd accumulation characteristics of the F1 hybrids were studied. In pot experiments, higher biomasses and Cd extraction abilities were found for two S. photeinocarpum F1 hybrids than for the parents, but the Cd contents in various organs were lower in the hybrids than the parents. However, the differences between the Cd contents in the two hybrids were not significant. The antioxidant enzyme (superoxide dismutase and peroxidase) activities were higher for the S. photeinocarpum F1 hybrids than the parents. Less DNA methylation was found in the hybrids than the parents because more demethylation occurred in the hybrids than the parents. The biomass, Cd content, and Cd extraction ability effects in field experiments were similar to the effects in the pot experiments. It was concluded that reciprocally hybridizing different S. photeinocarpum ecotypes improved the ability of S. photeinocarpum to be used to phytoremediate contaminated land.
Analysis of variation in morphological characters of Potanin Altai osman, Oreoleuciscus potanini, from two freshwater and one brackish water lakes of Western Mongolia has shown that specimens of different ecological forms—herbivorous and piscivorous—form two integral and, at the level under consideration, internally indivisible units in the system of phenetic diversity of the species O. potanini. 相似文献