Ruiz Guajardo J.C.,University of Edinburgh |
Schnabel A.,Indiana University at South Bend |
Ennos R.,University of Edinburgh |
Otero-Arnaiz A.,Instituto Nacional Of Ecologia |
Stone G.,University of Edinburgh
Molecular Ecology | Year: 2010
Acacias across Africa have enormous ecological and economic importance, yet their population genetics are poorly studied. We used seven microsatellite loci to investigate spatial genetic structure and to identify potential ecological and geographic barriers to dispersal in the widespread acacia, Senegalia (Acacia) mellifera. We quantified variation among 791 individuals from 28 sampling locations, examining patterns at two spatial scales: (i) across Kenya including the Rift Valley, and (ii) for a local subset of 11 neighbouring locations on Mpala Ranch in the Laikipia plateau. Our analyses recognize that siblings can often be included in samples used to measure population genetic structure, violating fundamental assumptions made by these analyses. To address this potential problem, we maximized genetic independence of samples by creating a sibship-controlled data set that included only one member of each sibship and compared the results obtained with the full data set. Patterns of genetic structure and barriers to gene flow were essentially similar when the two data sets were analysed. Five well-defined geographic regions were identified across Kenya within which gene flow was localized, with the two strongest barriers to dispersal splitting the Laikipia Plateau of central Kenya from the Western and Eastern Rift Valley. At a smaller scale, in the absence of geographic features, regional habitat gradients appear to restrict gene flow significantly. We discuss the implications of our results for the management of this highly exploited species. © 2010 Blackwell Publishing Ltd.
Blackman A.,Resources for the Future |
Lahiri B.,Oklahoma State University |
Rivera Planter M.,Instituto Nacional Of Ecologia |
Munoz Pina C.,Instituto Nacional Of Ecologia
Journal of Environmental Economics and Management | Year: 2010
Because conventional command-and-control environmental regulation often performs poorly in developing countries, policymakers are increasingly experimenting with alternatives, including voluntary regulatory programs. Research in industrialized countries suggests that such programs are sometimes ineffective, because they mainly attract relatively clean participants free-riding on unrelated pollution control investments. We use plant-level data on more than 100,000 facilities to analyze the Clean Industry Program, Mexico's flagship voluntary regulatory initiative. We seek to identify the drivers of participation and to determine whether the program improves participants' environmental performance. Using data from the program's first decade, we find that plants recently fined by environmental regulators were more likely to participate, but that after graduating from the program, participants were not fined at a substantially lower rate than nonparticipants. These results suggest that although the Clean Industry Program attracted dirty plants under pressure from regulators, it did not have a large, lasting impact on their environmental performance. © 2010 Elsevier Inc.
Zhang T.,Tsinghua University |
Fiedler H.,UNEP DTIE Chemicals Branch |
Yu G.,Tsinghua University |
Ochoa G.S.,Instituto Nacional Of Ecologia |
And 4 more authors.
Chemosphere | Year: 2011
Open burning of waste is the most significant source of polychlorinated dibenzo-para-dioxins and dibenzofurans (PCDD/PCDF) in many national inventories prepared pursuant to the Stockholm Convention on Persistent Organic Pollutants. This is particularly true for developing countries. Emission factors for POPs such as PCDD/PCDF, dioxin-like polychlorinated biphenyls (dl-PCB) and penta- and hexachlorobenzenes (PeCBz/HCB) from open burning of municipal solid waste in China and Mexico are reported herein. Six different waste sources were studied varying from urban-industrial to semi-urban to rural. For PCDD/PCDF, the emission factors to air ranged from 3.0 to 650ngTEQkg-1waste and for dl-PCB from 0.092 to 54ngTEQkg-1waste. Emission factors for PeCBz (17-1200ngkg-1waste) and HCB (24-1300ngkg-1waste) spanned a wide but similar range. Within the datasets there is no indication of significant waste composition effect on emission factor with the exception of significantly higher Mexico rural samples. © 2011 Elsevier Ltd.
Achcar J.A.,University of Sao Paulo |
Rodrigues E.R.,National Autonomous University of Mexico |
Tzintzun G.,Instituto Nacional Of Ecologia
Environmetrics | Year: 2011
In this paper, we consider some non-homogeneous Poisson models to estimate the probability that an air quality standard is exceeded a given number of times in a time interval of interest. We assume that the number of exceedances occurs according to a non-homogeneous Poisson process (NHPP). This Poisson process has rate function $\lambda(t)$, $t \geq 0$, which depends on some parameters that must be estimated. We take into account two cases of rate functions: the Weibull and the Goel-Okumoto. We consider models with and without change-points. When the presence of change-points is assumed, we may have the presence of either one, two or three change-points, depending of the data set. The parameters of the rate functions are estimated using a Gibbs sampling algorithm. Results are applied to ozone data provided by the Mexico City monitoring network. In a first instance, we assume that there are no change-points present. Depending on the adjustment of the model, we assume the presence of either one, two or three change-points. Copyright © 2009 John Wiley & Sons, Ltd.
Zamorano P.,Instituto Nacional Of Ecologia |
Hendrickx M.E.,National Autonomous University of Mexico
Cahiers de Biologie Marine | Year: 2011
A bibliographic search, a compilation of collection data and recent sampling of deep-water mollusks (from 200 to 4200 m) in the Gulf of California (Talud IV-IX cruises, 2000-2005) yield a total of 685 records on both sides of the Baja California Peninsula, Mexico. Records were split into Gulf of California (GC) and the slope of Baja California in the influence zone of the California Current (Mexico only) records (CC) and a comparative analysis of β diversity for both fauna was made using depth and latitude records. Five commonly used similarity indices (Jaccard, Sørensen, Sokal and Sneath, Braun-Blanquet, and Ochiai-Barkman) were calculated for each cell of the latitude by depth matrix. A total of 281 species and 201 genera were recognized. Number of records and species richness were usually higher in the GC, but diversity profiles obtained on both sides of the Peninsula were similar. Using the Sørensen index, highest similarity between GC and CC fauna was observed at 23°N (species: 13%, genera: 23%) and at 200-699 m (species: 20%, genera: 33%). Based on data available and our present knowledge, the effect of the Baja California Peninsula and of the local currents pattern results in a low similarity between GC and CC fauna (86% of the species and 75% of the genera are distinct).
Gerrodette T.,Southwest Fisheries Science Center |
Rojas-Bracho L.,Instituto Nacional Of Ecologia
Marine Mammal Science | Year: 2011
Bycatch in artisanal gill nets threatens the vaquita, Phocoena sinus, with extinction. In 2008 the Mexican government announced a conservation action plan for this porpoise, with three options for a protected area closed to gill net fishing. The probability of success of each of the three options was estimated with a Bayesian population model, where success was defined as an increase in vaquita abundance after 10 yr. The model was fitted to data on abundance, bycatch, and fishing effort, although data were sparse and imprecise. Under the first protected area option, the existing Refuge Area for the Protection of the Vaquita, bycatch was about 7% of population size, and probability of success was 0.08. Under the second option with a larger protected area, the probability of success was 0.35. The third option was large enough to eliminate vaquita bycatch and had a probability of success >0.99. Probability of success was reduced if elimination of vaquita bycatch was delayed or incomplete. Despite considerable efforts by the Mexican government to support vaquita conservation, abundance will probably continue to decline unless additional measures to reduce vaquita bycatch are taken, such as banning gill nets within the vaquita's range and developing effective alternative fishing gear. 2011 by the Society for Marine Mammalogy Published 2011. This article is a US Government work and is in the public domain in the USA.
Avila-Forcada S.,National Autonomous University of Mexico |
Avila-Forcada S.,Princeton University |
Martinez-Cruz A.L.,University of Maryland University College |
Munoz-Pina C.,Instituto Nacional Of Ecologia
Marine Policy | Year: 2012
Vaquita marina, a small species of porpoise endemic to the Northern Gulf of California in Mexico, is the world's most endangered cetacean species. With the purpose of preserving vaquita, the Mexican government launched PACE-Vaquita in 2008. This voluntary program offers an innovative schedule of compensations: as in a payment-for-conservation program, PACE-Vaquita compensates for temporary reductions in fishing effort; as in a program to accelerate technology adoption, PACE-Vaquita compensates for switching to vaquita-safe fishing methods; and as in a buyback program, PACE-Vaquita compensates fishermen for a permanent exit from fisheries. This paper seeks the factors explaining fishermen's participation in PACE-Vaquita during its first year of operation. Analysis is carried out through a multinomial logit specification on a data set collected one week after the enrollment deadline. This paper shows that fishermen with skills in alternative economic activities more likely quit fishing, and fishermen with relatively less productive vessels more likely switched to vaquita-safe fishing methods. Discussion of public policy implications is provided. © 2011 Elsevier Ltd.
Velasco A.,Instituto Nacional Of Ecologia |
Ramirez M.,Instituto Nacional Of Ecologia |
Hernandez S.,Metropolitan Autonomous University |
Schmidt W.,Programa Ambiental GTZ |
Revah S.,Metropolitan Autonomous University
Journal of Hazardous Materials | Year: 2012
Single Cr(VI) reduction and coupled reduction/stabilization (R/S) processes were evaluated at pilot scale to determine their effectiveness to treat chromite ore processing residue (COPR). Sodium sulfide was used as the reducing agent and cement, gypsum and lime were tested as the stabilizing agents. The pilot experiments were performed in a helical ribbon blender mixer with batches of 250kg of COPR and mixing time up to 30min. Na 2S/Cr(VI) mass ratios of 4.6, 5.7 and 6.8 were evaluated in the single reduction process to treat COPR with Cr(VI) concentration of ≈4.2g/kg. The R/S process was tested with a Na 2S/Cr(VI) mass ratio of 5.7 and including stabilizing agents not exceeding 5% (w/w COPR), to treat COPR with a Cr(VI) content of ≈5.1g/kg. The single reduction process with a ratio of 6.8, reached Cr(VI) reduction efficiencies up to 97.6% in the first days, however these values decreased to around 93% after 380 days of storage. At this point the total Cr level was around 12.5mg/L. Cr(VI) removal efficiencies exceeding 96.5% were reached and maintained during 380 days when the coupled R/S process was evaluated. Total Cr levels lower than 5mg/l were attained at the initials days in all R/S batch tested, however after 380 days, concentrations below the regulatory limit were only found with gypsum (2%) as single agent and with a blend of cement (4%) and lime (1%). These results indicated that the coupled R/S process is an excellent alternative to stabilize COPR. © 2011 Elsevier B.V..
Zamorano P.,Instituto Nacional Of Ecologia |
Hendrickx M.E.,National Autonomous University of Mexico
Marine Biodiversity Records | Year: 2012
From samples taken during the oceanographic cruises TALUD IV-X in the southern and central Gulf of California, Mexico, 291 specimens of Lucinoma heroica were obtained in a depth interval of 731 to 991 m. The species occurred under conditions of severe (<0.1 ml l-1O2) and moderate hypoxia (0.1-0.5 ml l-1O2). The correlation between height and length of the shell showed isometric growth with a trimodal size distribution, showing an average interval of 3.75 mm to 47.40 mm in height and 4.96 mm to 54.00 mm in length. Small individuals (≤20 mm) were distributed in a moderate hypoxic environment, while the larger (>35 mm) tolerated an almost anoxic habitat. Medium-sized specimens (21-35 mm) were found in concentration close to 0.2 ml l-1O2. Average density was 1.532 ind l-1 in infauna samples (dredge and core) and 0.002 ind m-2 in epifauna samples (benthic sledge). © 2012 Marine Biological Association of the United Kingdom.
Wagner H.H.,Instituto Nacional Of Ecologia
Heredity | Year: 2016
Strong spatial genetic structure in plant populations can increase homozygosity, reducing genetic diversity and adaptive potential. The strength of spatial genetic structure largely depends on rates of seed dispersal and pollen flow. Seeds without dispersal adaptations are likely to be dispersed over short distances within the vicinity of the mother plant, resulting in spatial clustering of related genotypes (fine-scale spatial genetic structure, hereafter spatial genetic structure (SGS)). However, primary seed dispersal by zoochory can promote effective dispersal, increasing the mixing of seeds and influencing SGS within plant populations. In this study, we investigated the effects of seed dispersal by rotational sheep grazing on the strength of SGS and genetic diversity using 11 nuclear microsatellites for 49 populations of the calcareous grassland forb Dianthus carthusianorum. Populations connected by rotational sheep grazing showed significantly weaker SGS and higher genetic diversity than populations in ungrazed grasslands. Independent of grazing treatment, small populations showed significantly stronger SGS and lower genetic diversity than larger populations, likely due to genetic drift. A lack of significant differences in the strength of SGS and genetic diversity between populations that were recently colonized and pre-existing populations suggested that populations colonized after the reintroduction of rotational sheep grazing were likely founded by colonists from diverse source populations. We conclude that dispersal by rotational sheep grazing has the potential to considerably reduce SGS within D. carthusianorum populations. Our study highlights the effectiveness of landscape management by rotational sheep grazing to importantly reduce genetic structure at local scales within restored plant populations.Heredity advance online publication, 6 July 2016; doi:10.1038/hdy.2016.45. © 2016 The Genetics Society