Effects of a complex archipelago on genetic subdivision of the intertidal limpet Siphonaria kurracheensis

Allozyme variation in the intertidal limpet Siphonaria kurracheensis was examined in 11 populations from the Houtman Abrolhos Islands, Western Australia, and four from the adjacent mainland, to test if the effects of these islands on genetic subdivision should include species with high dispersal. Consistent with extensive planktonic dispersal, genetic subdivision was low, with an average standardized variance in allelic frequencies (F_ST) of 0.010 over 400 km along the mainland, and 0.009 over 70 km in the Abrolhos Islands. Nevertheless, subdivision was statistically significant at the smallest scale examined (about 10 km), showing a pattern of local heterogeneity and large-scale homogeneity, which is common in planktonic dispersers. Among the island populations, heterozygosity was positively correlated with a multivariate index of exposure. The level of heterozygosity at the most exposed island sites is equivalent to that at the (also exposed) mainland sites, whereas it is lower in the most sheltered island sites. Although this indicates that some island populations are less well connected to the major pool of larvae, the overall effect of the archipelago on genetic subdivision is no greater than occurs on the mainland coast. This is contrary to findings in previously studied species with less potential for dispersal, suggesting that the local impediments to dispersal are selective in their effects, and are unlikely to be broadly important for genetic divergence in widely dispersing species.     

Osteological development of the vertebral column and of the fins in Diplodus sargus (Teleostei: Perciformes: Sparidae)

The osteological development of vertebral column and fins in white sea bream, Diplodus sargus (Linnaeus, 1758) was studied. Vertebral ontogeny started at 5.7 mm total length (TL, post-fixation), with the formation of the first cartilaginous neural and haemal arches, and was completed by the full attainment of dorsal ribs (20.8 mm TL). The formation of vertebral centra occurred between 7.3 and 9.4 mm TL, but was fully completed only after the development of post- and pre-zygapophyses (26.0 mm TL). Pectoral supports were the first fin elements that started to develop (3.8 mm TL), followed by those of the caudal fin (5.2 mm TL), dorsal and anal fins (6.7 mm TL), and then by those of the pelvic fin (9.5 mm TL). The caudal fin of D. sargus was the first to develop fin rays and attain the full count of lepidotrichia (5.6-7.8 mm TL), but the last to attain the full count of dermatotrichia (7.9-16.0 mm TL). The next fins starting to present rays were the pectoral (6.5 mm TL) and the dorsal and anal fins (7.5 mm TL), while the pelvic fins were the last (11.5 mm TL). Following the caudal lepidotrichia (7.8 mm TL), the anal (10.5 mm TL), dorsal (12.0 mm TL), pectoral (11.4 mm TL) and pelvic fins (12.5 mm TL) were the next with fully completed ray counts. Finally, fin meristics were fully developed with the caudal dermatotrichia. The results are discussed in comparison with the fin and vertebral ontogeny of other teleosts.     

Effects of environmental parameters on the oxygen consumption of four marine invertebrates: a comparative factorial study

The oxygen consumption curves of two decapod crustaceans (Palaemon serratus, Penaeus monodon) and two prosobranch molluscs (Trunculariopsis trunculus, Nassarius mutabilis) have been detected in the entire pO₂ interval from 0 to 160 mmHg, under different conditions of temperature and salinity. From the experimental curves, physiological parameters such as the initial oxygen consumption velocity, the Q ₁₀ values and the oxygen independence indices have been measured. The latter parameters have been obtained using normalised plots which allow their better evaluation. The effects of temperature, salinity and oxygen partial pressure on the oxygen-consumption features have been studied using a factorial experimental plan which allows measurement of the effects of each experimental variable as well as the effects of synergistic interactions between different variables. Received: 27 March 2000 / Accepted: 13 November 2000     

Boundaries and Corridors as a Continuum of Ecological Flow Control: Lessons from Rivers and Streams

Abstract: Landscape boundaries and corridors are areas of small spatial extent relative to their large effects on ecological flows. The trend in ecological literature is to treat corridors and boundaries as separate phenomena on the landscape. This approach, however, misses a fundamental aspect they have in common: their strong influence on ecological flows. Corridors and boundaries exist at opposite ends of a permeability gradient, differing in their effects on rates and direction of flow. The position of landscape structures along this permeability gradient depends on attributes of both the flow and of the structure itself. We discuss boundaries and corridors in terms of mover specificity, scale, and effects on different levels of ecological organization, using rivers and streams to illustrate our points. We predict which structures will act as boundaries or corridors and at what spatial and temporal scales they are likely to be relevant. Considering the function of landscape structures across the boundary-corridor continuum will provide researchers and managers with a more complete, holistic viewpoint and will allow better strategies to attain conservation goals.     

Misdirections in Conservation Biology

Abstract: The hypothesis that conservation biology is proceeding along two separate trajectories ( Caughley 1994 ) has provoked extensive discussion. Caughley's dichotomy, a "small-population" paradigm versus a "declining-population" paradigm, has recently been exemplified in discussion of management strategies for conservation of the Javan gibbon (   Hylobates moloch ). Recommendations from extensive fieldwork focused on reducing the major known threat to the species—habitat destruction—and proposed a strategy of forest management and protection. A population and habitat viability analysis focused on an entirely different issue—low genetic diversity—and proposed a program of single-species genetic management. It is not surprising that geneticists see inbreeding as a major conservation problem, and it is not unusual that ecologists focus on how ecology relates to conservation. A problem results when managers assume that addressing only one or the other of these factors is the appropriate conservation action. Conservation biologists must learn to thoroughly analyze every conservation problem before trying to solve it. We must actively involve experts from all fields in forming and reviewing conservation strategies. If only captive breeding specialists or ecologists are invited to address a problem, then the techniques employed to solve it will be irrevocably biased. We do not all see the world in the same way, even within the relatively small field of conservation. To achieve effective conservation action, we must learn to balance and capitalize on our different perspectives.     

Begging calls and parental feeding decisions in tree swallows (Tachycineta bicolor)

We conducted playback experiments to examine how parent tree swallows (Tachycineta bicolor) use nestling begging calls to distribute feedings to individuals within broods. In a first study, we used a paired-choice test to determine if parents discriminated between the taped begging calls of nestlings deprived of food and those of nestlings that had been recently fed. Our results showed that parents directed their first feeding attempt towards model nestlings near speakers playing deprived calls significantly more often than to models near speakers playing fed calls. They also made more feeding attempts overall to models with deprived calls. In the second study, we varied call rate and amplitude to examine which call features parents might use to discriminate begging calls. Parents directed significantly more first feeding attempts and more feeding attempts overall towards non-begging nestlings near speakers playing high call rates than to nestlings near speakers playing low call rates. They did not, however, discriminate between calls differing in amplitude. Previous studies have shown that parent birds use begging calls to regulate overall feeding rates to the brood. Our results suggest that parent tree swallows also use begging calls when feeding individual nestlings and, in particular, prefer calls associated with increased levels of nestling hunger. Received: 14 February 2000 / Revised: 6 October 2000 / Accepted: 16 October 2000     

Metal releases from a municipal solid waste incineration air pollution control residue mixed with compost

The influence of 10 wt.% mature compost was tested on the heavy metal leachate emissions from a calcium-rich municipal solid waste incineration air pollution control residue (MSWI APC). Apart from elongated columns (500 and 1250 mm), an otherwise norm compliant European percolation test setup was used. More than 99% of the metals Al, As, Cd, Cr, Cu, Fe and Ni were left in the APC residue after leaching to a liquid-to-solid ratio (L/S) of 10. Apparent short-term effects of elevated leachate DOC concentrations on heavy metal releases were not detected. Zn and Pb leachate concentrations were one order of magnitude lower for L/S 5 and 10 from the pure APC residue column, which suggests a possible long-term effect of compost on the release of these elements. Prolonging the contact time between the pore water and the material resulted in elevated leachate concentrations at L/S 0.1 to L/S 1 by a factor of 2. Only Cr and Pb concentrations were at their maxima in the first leachates at L/S 0.1. Equilibrium speciation modelling with the PHREEQC code suggested portlandite (Ca(OH)2) to control Ca solubility and pH.     

Biogeochemical gradients as a framework for understanding waste‐site evolution

The migration of biogeochemical gradients is a useful framework for understanding the evolution of biogeochemical conditions in groundwater at waste sites contaminated with metals and radionuclides. This understanding is critical to selecting sustainable remedies and evaluating sites for monitored natural attenuation, because most attenuation mechanisms are sensitive to geochemical conditions, such as pH and redox potential. Knowledge of how gradients in these parameters evolve provides insights into the behavior of contaminants with time and guides characterization, remedy selection, and monitoring efforts. An example is a seepage basin site at the Savannah River Site in South Carolina where low‐level acidic waste has seeped into groundwater. The remediation of this site relies, in part, on restoring the natural pH of the aquifer by injecting alkaline solutions. The remediation will continue until the pH upflow of the treatment zone increases to an acceptable value. The time required to achieve this objective depends on the time it takes the trailing pH gradient, the gradient separating the plume from influxing natural groundwater, to reach the treatment zone. Predictions of this length of time will strongly influence long‐term remedial decisions. © 2008 Wiley Periodicals, Inc.