Oil palm plantations are expanding in Latin America due to the global demand for food and biofuels, and much of this expansion has occurred at expense of important tropical ecosystems. Nevertheless, ...there is limited knowledge about effects on aquatic ecosystems near to oil palm-dominated landscapes. In this study, we used Landsat 7 ETM+, Landsat 8 OLI imagery and high-resolution images in Google Earth to map the current extent of oil palm plantations and determined prior land use land cover (LULC) in the Usumacinta River Basin as a case-study site. In addition, we assess the proximity of the crop with aquatic ecosystems distributed in the Usumacinta floodplains and their potential effects. Based on our findings, the most significant change was characterized by the expansion of oil palm crop areas mainly at expenses of regional rainforest and previously intervened lands (e.g. secondary vegetation and agriculture). Although aquatic ecosystem class (e.g. rivers, lagoons and channels) decreased in surface around 3% during the study period (2001–2017), the change was not due to the expansion of oil palm lands. However, we find that more than 50% of oil palm cultivations are near (between 500 and 3000 m) to aquatic ecosystems and this could have significant environmental impacts on sediment and water quality. Oil palm crops tend to spatially concentrate in the Upper Usumacinta ecoregion (Guatemala), which is recognized as an area of important fish endemism. We argue that the basic information generated in this study is essential to have better land use decision-making in a region that is relative newcomer to oil palm boom.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
It is commonly assumed that bats, due to their flight capacity, are not affected by landscape attributes across small geographic extensions. However, recent studies with phyllostomids have found ...evidence of negative responses, such as decreasing genetic diversity with decreasing forest amount, specifically in areas dominated by agricultural land. The purpose of this study was to evaluate if landscape composition and configuration could be influencing the genetic diversity of a common frugivorous bat:
Artibeus jamaicensis
. We worked in an area characterized by the presence of extensive agricultural land, with a trend towards open spaces of high contrast with forests. Through mtDNA control region sequences, we inferred high levels of genetic diversity in the surveyed landscapes. In order to determine a possible relationship between genetic diversity and landscape attributes, we employed a multivariate exploratory analysis that allowed us to determine the independent contribution of each variable, in a hierarchical model. We found a negative relationship between genetic diversity and total forest edge, which is a variable that reflects the degree of fragmentation. This procedure can be implemented in population genetics, allowing the incorporation of spatially explicit variables.
En especies de amplia distribución, como Didelphis marsupialis y Didelphis virginiana, se predicen tamaños poblacionales grandes, alta diversidad y poca diferenciación genética. En este estudio se ...estimó la abundancia relativa de D. marsupialis y D. virginiana mediante la captura de organismos en la región de Los Altos y la Depresión Central de Chiapas. Se estimó también la diversidad y estructura genética a partir de 7 loci microsatélites. La abundancia relativa fue baja, entre 0.008-0.06 individuos trampas noches y la mayor incidencia de tlacuaches se observó en la Depresión Central. La proporción de sexos se ajustó significativamente a la relación 1:1 en ambas especies. La mayor diversidad genética se registró en la Depresión Central en D. virginiana (He=0.58) con altos niveles de endogamia. Se observó diferenciación genética moderada entre las especies (Frt=0.13) y mínima entre poblaciones de cada especie (Fsr=0.01). A pesar de que los valores de diversidad genética fueron moderados, D. marsupialis y D. virginiana tienen abundancias relativas bajas con altos niveles de endogamia, lo que puede tener consecuencias negativas a futuro sobre la variabilidad genética de estas especies en las poblaciones estudiadas.
In wide distribution species, as D. marsupialis and D. virginiana, large population sizes, high diversity and little genetic differentiation are predicted. In this study, the relative abundance of D. marsupialis and D. virginiana by capturing organisms in the Highlands and the Central Depression regions, in Chiapas, was estimated. Also the diversity and structure genetic from 7 microsatellite loci were estimated. The relative abundance was low (between 0.008-0.06 individuals traps nights) and the highest incidence of opossums was observed in the Central Depression. The sex ratio was significantly adjusted to the relation 1:1 in both species. The greater genetic diversity was recorded in the Central Depression in D. virginiana (He=0.58), with high levels of inbreeding. Genetic differentiation moderate was observed between species (Frt=0.13) and minimum among populations of each species (Fsr=0.01). Although the values of genetic diversity were moderate, D. marsupialis and D. virginiana have low abundances with high levels of inbreeding, which may have negative consequences in the future on the genetic variability of these species in the studied populations.
The Virginia opossum (Didelphis virginiana) is considered highly adaptable to anthropogenic disturbances; however, the genetic effects of disturbance on this marsupial have not been studied in wild ...populations in Mexico. Here we evaluated the genetic diversity of D. virginiana at sites with different levels of disturbance within the Highlands and Central Depression regions of Chiapas in southern Mexico. Twelve microsatellite loci were used and the results demonstrated moderate mean heterozygosity (He = 0.60; Ho = 0.50). No significant differences in heterozygosity were found among sites with different levels of disturbance in both regions (range Ho = 0.42–0.57). We observed low but significant levels of genetic differentiation according to disturbance level. The inbreeding coefficient did not differ significantly from zero, suggesting that low genetic differentiation in these environments may be associated with sufficient random mating and gene flow, a result associated with the high dispersal and tolerance characteristics of this marsupial. Our results for D. virginiana in this particular area of Mexico provide a foundation for exploring the impact of human disturbance on the genetic diversity of a common and generalist species.
Fruit-eating bats play a fundamental role in animal seed dispersal and should be considered key actors in tropical forest restoration. We explored the use of commercial fruits as attractants for bats ...to increase seed dispersal to areas affected by forest fires in southern Mexico. We captured bats and collected seeds from feces and seed rain at perturbed sample sites where mature bananas and mangos were placed, and from non-treated control sites. Bat and bat-dispersed plant species richness and abundance were analyzed, and the importance of each bat species as a disperser was evaluated. Additionally, germination boxes were set up to evaluate the germination of seeds found in bat feces. We captured 724 individuals of 16 frugivorous bat species, 15 spp in treated and 12 spp in control sites. Sowell's Short-tailed bat, Toltec Fruit-eating bat and the Western Long-tongued bat showed higher abundances in treated sites, suggesting that these three species were attracted by fruits. The most important disperser was the Sowell's Short-tailed bat, followed by the Jamaican Fruit-eating and Toltec Fruit-eating bat. A greater proportion of pioneer species and trees, followed by shrubs, were found in the overall bat diet. The germination percentage was > 50%, suggesting that the use of fruits to attract bats can be a feasible wildlife management activity to encourage the succession process. We recommend further studies to test and improve this activity.
Forests are a key habitat for bats, but tend to be lost and fragmented in some agri-environment schemes. We studied the effects of forest cover change on phyllostomid bats in agricultural landscapes ...with increment of open areas in an upland region in Chiapas, southeast Mexico. We tested whether with forest cover increase there is a directly proportional response on assemblage species diversity measures, on the capture success and body condition of particular ensembles. Depending on the spatial analysis window, and presumably on vagility, we found positive and significant associations with the sanguivore ensemble's capture success, as well as with the nectarivore and shrub frugivore ensembles' body condition. We support the idea that appropriate amounts of forest over small geographic extents may propitiate favorable environments for some phyllostomids, which can also provide important ecological services. Furthermore, the arrangement of ecologically similar species proved to be valuable for exploring adaptive traits, and adequate for conservation strategies of species-rich taxa.
The resplendent quetzal Pharomachrus mocinno is an endangered bird specie that reproduces only in small cloud forests, such as those found in Latin America, but over the past century, intensification ...of cattle ranching and agriculture has resulted in the loss and fragmentation of cloud forests. Results are presented from a study in which the effects of land-cover changes of cloud forests on the current distribution of quetzals were explored in southern Mexico. Past breeding habitats were identified based on a literature review, and the distribution was then compared with the current distribution determined by recent field surveys. Of the 39 breeding evergreen cloud forests that existed in 1970, only five were found to have persisted. The bird surveys revealed that the distribution of quetzals had been reduced by 82% during the past 30 yr due to the destruction and fragmentation of evergreen cloud forests caused by land transformation.
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