Evolving metacommunities: toward an evolutionary perspective on metacommunities

The metacommunity framework predicts that local coexistence depends on the outcome of local species interactions and regional migration. In analogous fashion, spatial structure among populations can shape species interactions through evolutionary mechanisms. Yet, most metacommunity theories assume that populations do not evolve. Here, we evaluate how evolution shapes local species coexistence and exclusion within the multiscale and multispecies context embodied by the metacommunity framework. In general, coexistence in joint ecological-evolutionary models requires low to intermediate dispersal rates that can promote maintenance of both regional species and genetic diversity. These conditions support a set of key mechanisms that modify patterns of species coexistence including local adaptation, gene storage effects, genetic rescue effects, spatial genetic subsidies, and metacommunity evolution. Multispecies extensions indicate that correlated selection can further alter the outcome of interspecific interactions depending on the magnitude and direction of correlations and shape of fitness trade-offs. We suggest that an evolving metacommunity perspective has the potential to generate novel predictions about community structure and function by incorporating the genetic and species diversity that characterize natural communities. In adopting such a perspective, we seek to facilitate understanding about the interactions between evolutionary and metacommunity dynamics.     

Lead detoxification by coontail (Ceratophyllum demersum L.) involves induction of phytochelatins and antioxidant system in response to its accumulation

Coontail (Ceratophyllum demersum L.) plants when exposed to various concentrations of Pb (1-100microM) for 1-7days, exhibited both phytotoxic and tolerance responses. The specific responses were function of concentration and duration. Plants accumulated 1748mugPbg(-1) dw after 7d which reflected its metal accumulation ability, however most of the metal (1222microgg(-1) dw, 70%) was accumulated after 1d exposure only. The toxic effect and oxidative stress caused by Pb were evident by the reduction in biomass and photosynthetic pigments and increase in malondialddehyde (MDA) content and electrical conductivity with increase in metal concentration and exposure duration. Morphological symptoms of senescence phenomena such as chlorosis and fragmentation of leaves were observed after 7d. The metal tolerance and detoxification strategy adopted by the plant was investigated with reference to antioxidant system and synthesis of phytochelatins. Protein and antioxidant enzymes viz., superoxide dismutase (SOD, EC 1.15.1.1), guaiacol peroxidase (GPX, EC 1.11.1.7) ascorbate peroxidase (APX, EC 1.11.1.11), catalase (CAT, EC 1.11.1.6) and glutathione reductase (GR, EC 1.6.4.2) showed induction at lower concentration and duration followed by decline. All enzymes except GPX showed maximum activity after 1d. An increase in cysteine, non-protein thiols (NP-SH) and glutathione (GSH) content was observed at moderate exposure conditions followed by decline. Phytochelatins (PC(2) and PC(3)) were synthesized to significant levels at 10 and 50microM Pb with concomitant decrease in GSH levels. Thus production of PCs seems important for the detoxification of metal, however it may lead to depletion of GSH and consequently oxidative stress. Results suggest that plants responded positively to moderate Pb concentrations and accumulated high amount of metal. Due to metal accumulation coupled with detoxification potential, the plant appears to have potential for its use as phytoremediator species in aquatic environments having moderate pollution of Pb.     

Dissipation and leaching of (14)C-monocrotophos in Soil Columns under subtropical climate

Dissipation and leaching behavior of 14C-monocrotophos was studied for 365 days under field conditions using PVC cylinders. The first set (24 cylinders) was spiked with 1.0 microCi 14C-labeled monocrotophos along with 1.06 mg unlabeled monocrotophos to give a concentration of 2 mg kg -1 in the soil up to 15 cm depth. The second set (24 cylinders) received 14C-labeled monocrotophos along with other non-labeled insecticides viz., dimethoate @ 300 g a.i ha-1, deltamethrin @ 12.5 g a.i ha-1, endosulfan @ 750 g a.i ha-1, cypermethrin @ 60 g a.i ha-1, and triazophos @ 600 g a.i ha-1 at an interval of 15 days each as recommended for the cotton crop. 14C-monocrotophos dissipated faster, up to 45% in first 90 days in columns treated with only monocrotophos compared to 25% in columns that received monocrotophos along with other insecticides. However, both the columns showed similar residues 180 days onward. After 180 days of treatment, 46% radiolabeled residues were observed, which reduced up to 39.6% after 365 days. Leaching of 14C-monocrotophos to 15-30 cm soil layer was observed in both the experimental setups. In the 15-30 cm soil layer of both soil columns, up to 0.19 mg 14C-monocrotophos kg-1d. wt. soil was detected after 270 days.     

Determination of atmospheric heavy metals using two lichen species in Katni and Rewa cities, India

A biomonitoring study was conducted to assess the levels of atmospheric heavy metal pollution in Katni and Rewa cities of Madhya Pradesh, state in central India. The Pyxine cocoes and Phaeophyscia hispidula, two epiphytic foliose lichen were used as bioindicators in the present study and seven metals (As, Al, Cd, Cr, Fe, Zn, Pb) were analyzed in naturally growing thallus. The concentrations of these metals was observed to be in higher range as maximum values of Al, Cd, Cr and Zn were reported from the lichen samples from Rewa city which was 561.8 +/- 2.4, 6.8 +/- 0.8, 35.2 +/- 1.4, 214.6 +/- 2.0 microg g(-1) dry weight respectively. Whereas As, Fe and Pb were reported maximum in the lichen samples collected from Katni city areas with 33.4 +/- 0.05, 689.4 +/- 2.6, 13.3 +/- 0.5 microg g(-1) dry weight respectively. However the accumulation of Cd and Pb from both the cities are more or less similar in concentration. The selectivity sequence of metals were Fe>Al>Zn>As>Cr>Pb>Cd in Katni city, and Al>Fe>Zn>Cr>As>Pb>Cd in Rewa city. The findings of this study indicates that extent of heavy metal pollution in the atmosphere of the two cities which may lead to adverse health affects.     

Ameliorants to immobilize Cd in rice paddy soils contaminated by abandoned metal mines in Korea

The cadmium (Cd) content of rice grain grown in metal-contaminated paddy soils near abandoned metal mines in South Korea was found to exceed safety guidelines (0.2 mg Cd kg?1) set by the Korea Food and Drug Administration (KFDA). However, current remediation technologies for heavy metal-contaminated soils have limited application with respect to rice paddy soils. Laboratory and greenhouse experiments were conducted to assess the effects of amending contaminated rice paddy soils with zerovalent iron (ZVI), lime, humus, compost, and combinations of these compounds to immobilize Cd and inhibit Cd translocation to rice grain. Sequential extraction analysis revealed that treatment with the ameliorants induced a 50-90% decrease in the bioavailable Cd fractions when compared to the untreated control soil. When compared to the control, Cd uptake by rice was decreased in response to treatment with ZVI + humus (69%), lime (65%), ZVI + compost (61%), compost (46%), ZVI (42%), and humus (14%). In addition, ameliorants did not influence rice yield when compared to that of the control. Overall, the results of this study indicated that remediation technologies using ameliorants effectively reduce Cd bioavailability and uptake in contaminated rice paddy soils.     

The interplay between environmental conditions and allee effects during the recovery of stressed zooplankton communities

Many important ecological phenomena depend on the success or failure of small introduced populations. Several factors are thought to influence the fate of small populations, including resource and habitat availability, dispersal levels, interspecific interactions, mate limitation, and demographic stochasticity. Recent field studies suggest that Allee effects resulting from mate limitation can prevent the reestablishment of sexual zooplankton species following a disturbance. In this study, we explore the interplay between Allee effects and local environmental conditions in determining the population growth and establishment of two acid-sensitive zooplankton species that have been impacted by regional anthropogenic acidification. We conducted a factorial design field experiment to test the impact of pH and initial organism densities on the per capita population growth (r) of the sexual copepod Epischura lacustris and the seasonally parthenogenetic cladoceran Daphnia mendotae. In addition, we conducted computer simulations using r values obtained from our experiments to determine the probability of extinction for small populations of acid-sensitive colonists that are in the process of colonizing recovering lakes. The results of our field experiment demonstrated that local environmental conditions can moderate the impacts of Allee effects for E. lacustris: Populations introduced at low densities had a significantly lower r at pH 6 than at pH 7. In contrast, r did not differ between pH 6 and 7 environments when E. lacustris populations were introduced at high densities. D. mendotae was affected by pH levels, but not by initial organism densities. Results from our population growth simulations indicated that E. lacustris populations introduced at low densities to pH 6 conditions had a higher probability of extinction than those introduced at low densities to a pH 7 environment. Our study indicates that environmental conditions and mate limitation can interact to determine the fate of small populations of sexually reproducing zooplankton species. If a more rapid recovery of acid-damaged zooplankton communities is desired, augmentation of dispersal levels may be needed during the early phases of pH recovery in order to increase the probability of establishment for mate-limited zooplankton species.     

Evaluation of lot-to-lot repeatability and effect of assay media choice in the recombinant Factor C assay

Measurement of environmental endotoxin exposures is complicated by variability encountered using current biological assay methods arising in part from lot-to-lot variability of the Limulus-amebocyte lysate (LAL) reagents. Therefore, we investigated the lot-to-lot repeatability of commercially available recombinant Factor C (rFC) kits as an alternative to LAL. Specifically, we compared endotoxin estimates obtained from rFC assay of twenty indoor dust samples, using four different extraction and assay media, to endotoxin estimates previously obtained by Limulus amebocyte lysate (LAL) assay and amounts of 3-hydroxy fatty acids (3-OHFA) in lipopolysaccharide (LPS) using gas-chromatography mass spectroscopy (GC-MS). We found that lot-to-lot variability of the rFC assay kits does not significantly alter endotoxin estimates in house dust samples when performed using three of the four assay media tested and that choice of assay media significantly altered endotoxin estimates obtained by rFC assay of house dust samples. Our findings demonstrate lot-to-lot reproducibility of rFC assay of environmental samples and suggest that use of rFC assay performed with Tris buffer or water as the extraction and assay medium for measurement of endotoxin in dust samples may be a suitable choice for developing a standardized methodology.     

Phenanthrene degradation in soils co-inoculated with phenanthrene-degrading and biosurfactant-producing bacteria

Contaminant sorption within the soil matrix frequently limits biodegradation. However, contaminant bioavailability can be species-specific. This study investigated bioavailability of phenanthrene (PHE) to two PHE-degrading bacteria (Pseudomonas strain R and isolate P5-2) in the presence of rhamnolipid biosurfactant and/or a biosurfactant-producing bacterium, Pseudomonas aeruginosa ATCC 9027. Pseudomonas strain R mineralized more soil-sorbed PHE than strain P5-2, but in aqueous cultures the rate and extent of PHE mineralization by P5-2 exceeded that by P. strain R. In Fallsington sandy loam (fine-loamy, mixed, active, mesic Typic Endoaquult) (high PHE-sorption capacity) the addition of rhamnolipid increased PHE mineralization by P. strain R. Phenanthrene mineralization in soils inoculated with P5-2 was minimal and no enhancement in PHE degradation was observed when biosurfactant was added. Co-inoculation of Fallsington sandy loam with the biosurfactant producer did not affect PHE mineralization by isolate P5-2, but significantly enhanced PHE mineralization by P. strain R. The enhancement of PHE mineralization could not be explained by P. aeruginosa-mediated PHE degradation. The addition of rhamnolipid at concentrations above the critical micelle concentration (CMC) resulted in enhanced PHE release from test soils. These results suggest that the PHE-degrading strains were able to access different pools of PHE and that the biosurfactant-enhanced release of PHE from soils did not result in enhanced biodegradation. The results also demonstrated that bacteria with the catabolic potential to degrade sorbed hydrophobic contaminants could interact commensally with surfactant-producing strains by an unknown mechanism to hasten the biodegradation of aromatic hydrocarbons. Thus, understanding interactions among microbes may provide opportunities to further enhance biodegradation of soil-bound organic contaminants.     

Total bacterial and fungal population after chlorpyrifos and quinalphos treatments in groundnut (Arachis hypogaea L.) soil

Short-term inhibitory effect on the total bacterial population was observed after chlorpyrifos and quinalphos applications in the groundnut fields, which recovered within 60 days after seed treatment and by 45 days of soil treatment. The fungal population was significantly enhanced after chlorpyrifos treatment whereas quinalphos inhibited the fungal population during the initial days of treatment but no effect was observed after 60 days of treatment. The residues of chlorpyrifos and quinalphos in the treated soil were not persistent and their half-lives ranged from 7.0 to 9.2 days and 13.2 to 20.6 days, respectively.     

Benefit–Cost Analysis of StormwaterQuality Improvements

The major purpose of this paper is to explore the potential value of benefit–cost evaluation for stormwater quality management decisions at a local level. A preliminary benefit–cost analysis (BCA) screening method is used for maximum extent practicable (MEP) analysis, identifying promising management practices, and identifying societal and economic tradeoffs for local stormwater problems. Ballona Creek, a major urban storm drain in Los Angeles, California, USA, is used to illustrate the practicality of the benefit–cost evaluation. The Ballona Creek example demonstrates the economic limits of stormwater management in an urban region and attests to the value of coordinated basinwide management compared to uncoordinated management by individual landowners. Evaluation results suggest that in urban areas, the benefit of stormwater quality improvements might be far greater if accompanied by comprehensive redesign of drainage networks and neighboring land uses. In this case, benefit–cost analysis is found to be useful for evaluating and understanding stormwater management alternatives despite the uncertainties in characterizing stormwater quality and the effects of stormwater management on improving receiving water quality.