Droughts and human impact in the ancient Uaymil region of the Maya lowlands inferred from a 2800‐year sedimentary archive at Lake Kaná, Mexico

BackgroundRecent studies have demonstrated the utility of DNA barcoding in the discovery of overlooked species and in the connection of immature and adult stages. In this study, we use DNA barcoding to examine diversity patterns in 121 species of Nymphalidae from the Yucatan Peninsula in Mexico. Our results suggest the presence of cryptic species in 8 of these 121 taxa. As well, the reference database derived from the analysis of adult specimens allowed the identification of nymphalid caterpillars providing new details on host plant use.Methodology/Principal FindingsWe gathered DNA barcode sequences from 857 adult Nymphalidae representing 121 different species. This total includes four species (Adelpha iphiclus, Adelpha malea, Hamadryas iphtime and Taygetis laches) that were initially overlooked because of their close morphological similarity to other species. The barcode results showed that each of the 121 species possessed a diagnostic array of barcode sequences. In addition, there was evidence of cryptic taxa; seven species included two barcode clusters showing more than 2% sequence divergence while one species included three clusters. All 71 nymphalid caterpillars were identified to a species level by their sequence congruence to adult sequences. These caterpillars represented 16 species, and included Hamadryas julitta, an endemic species from the Yucatan Peninsula whose larval stages and host plant (Dalechampia schottii, also endemic to the Yucatan Peninsula) were previously unknown.Conclusions/SignificanceThis investigation has revealed overlooked species in a well-studied museum collection of nymphalid butterflies and suggests that there is a substantial incidence of cryptic species that await full characterization. The utility of barcoding in the rapid identification of caterpillars also promises to accelerate the assembly of information on life histories, a particularly important advance for hyperdiverse tropical insect assemblages.

Contamination by metals poses a significant threat to marine ecosystems and the health of marine organisms, including cetaceans. This study aimed to assess the concentrations of some metal and metalloids in the skin of bottlenose dolphins (Tursiops truncatus) from the Yucatan Peninsula in Mexico using Flame Atomic Absorption (FAA) spectrometry. A total of 41 skin samples were collected, comprising 22 samples from Yucatán in the Gulf of Mexico and 19 samples from Chetumal Bay in the Caribbean. The results of our analysis revealed the presence of various elements in the skin of bottlenose dolphins from coastal waters in the Yucatan Peninsula. Among the detected metals, zinc (Zn), iron (Fe), and arsenic (As) exhibited notable concentrations, with the order of abundance being Zn > Fe > As > Cu > Cr > Cd > Ni. The elevated concentrations of Zn and Fe suggest potential exposure and accumulation of these metals in the studied dolphin population. Interestingly, measurable concentrations of lead (Pb) and manganese (Mn) were not detected in the skin samples, indicating either low levels or the absence of their accumulation in the studied dolphin populations. The absence of measurable Pb concentrations is particularly encouraging as Pb is known to have detrimental effects on marine organisms and is commonly associated with anthropogenic activities. This study provides valuable insights into the metal contamination status in bottlenose dolphins from the Yucatan Peninsula, Mexico. The notable concentrations of Zn, Fe, and As raise concerns about potential health risks to these charismatic marine mammals. Further research is warranted to investigate the sources and pathways of heavy metal exposure in this population and to understand the potential consequences of such exposure on the health and well-being of bottlenose dolphins in the Yucatan Peninsula.

The fourth biennial meeting of the International Biogeography Society (IBS) in Merida, Yucatan in January 2009 represented a double opportunity for Mexican biologists. First, it fostered the integration of the large community of Mexican biogeographers with the activities of the IBS. Second, the meeting allowed us to welcome a large number of delegates from distant parts of the world who were able to visit what has been considered an obligate destination for nature lovers and cultural tourists alike: the Yucatan peninsula. As Edward O. Wilson pointed out, besides economic power every country has two additional and important types of wealth: cultural and natural. Cultural richness is a naturally embedded component of the Mexican way of life.

The karst lakes in Jiuzhaigou Nature Reserve are an integral part of the karst lake landscape, yet research on the formation mechanism for the color of the blue-green lakes in Jiuzhaigou is insufficient. With the help of hyperspectral instruments, coupled with hydro-chemical analysis, this paper elaborates on the unique color characteristics of the Jiuzhaigou karst lakes, delves into the color formation mechanism of the lakes, establishes a regression equation for the color of the lakes as well as the water quality parameters, and sheds light upon the causes for the color distinction between the karst lakes in Jiuzhaigou and the plateau freshwater lakes. The experiment shows that the Jiuzhaigou karst lakes are primarily blue and green, while the proportion of short-wavelength light in the normalized water-leaving radiance and the total incident irradiance of lake water is higher. Based on the redundancy analysis and the correlation analysis, travertine deposition is the core link in the color formation of the blue karst lakes in Jiuzhaigou, while the selective reflection and scattering of the suspended calcium carbonate particulate matters towards visible light represents the optical foundation for the formation. In addition, physical factors such as depth and transparency, changes to the water quality parameters that affect the travertine deposition rate, and the eutrophication process will all exert significant influence over the formation. By building on water-leaving radiance, this paper quantifies the lake color with the tristimulus values (R, G, B) via colorimetrical methods, which features solid goodness of fit with the linear regression equation established based on the water quality parameters. The principal component analysis and colorimetrical analysis show that the color of the karst lakes in Jiuzhaigou varies substantially from that of the plateau freshwater lakes, which mainly results from the difference in the water quality. Research conducted in this paper on the color formation mechanism of the distinct blue karst lakes in Jiuzhaigou illuminates the formation and maintenance mechanism of the plateau karst lakes, which is conducive to better understanding towards the relationship between the water quality and colors of the karst lakes, and provides scientific proof for the establishment of the water quality assessment indicator system based on the colors of the karst lakes.

This chapter presents results generated by an integrated dynamic model used to study the interactions between population, environment, and economy. The model is based on the Population-Development-Environment (PDE) approach developed by Lutz (1994). Recent PDE models have dealt with the small islands of Mauritius (Lutz, 1994) and Cape Verde (Wils, 1996). After studying islands the next step is to develop a more elaborate PDE model for a peninsula. For the present study, the Yucatan peninsula in Mexico was chosen for several reasons. First, it is a region that mostly borders the sea, which poses constraints to trade and human migration. Only recently, the peninsula has been connected by land infrastructure to the rest of Mexico. Second, it has a specific historical culture — the Mayan civilisation whose population suddenly decreased — of which many archaeological sites remain (Lutz et al., 1996). Third, drastic economic and demographic changes have taken place in the last twenty years, such as a large population increase, resulting mostly from the growth of the tourism industry. Fourth, conflicts exist between the goals of economic growth, the population and the environment which are, to a large extent, due to tourism growth. In the PDE modelling of the peninsula special attention is given to the tourism sector for three reasons: (i) it is the most important economic sector in the peninsula; (ii) the tourism sector has developed rapidly in the last decades and is expected to continue growing in the coming years; and (iii) there are many interesting interactions between tourism, other economic sectors, population and environment worth analysing.

The impact of different types of land tenure in areas with high biodiversity and threats of deforestation remains poorly understood. We apply rigorous quasi-experimental methods and detailed geospatial data to assess the role of tenure regimes—communally held lands (specifically, ejidos), private property, and their impact on the effectiveness of protected areas, in reducing forest loss in a biodiversity hotspot- the Yucatan peninsula in Mexico. We find evidence that, while protected areas are effective on average, their impact depends on the underlying type of tenure regime and forest, proxied by biomass levels and biome. Protecting communally held land may reduce deforestation, specifically the loss of medium- and high-biomass forests, compared to forests under private property regimes. Our results have important policy implications for the conservation and climate change mitigation efforts on the Yucatan. However, the high variance in forest loss rates among ejidos indicates that other characteristics of ejidos may be central to understanding community-based forest conservation opportunities.

Voluminous territorialisation: Historical contestations over the Yucatan Peninsula’s subterranean waterscape

Isozymatic variation and phylogenetic relationships among extant henequén (Agave fourcroydes) germplasm and wild populations of its ancestor A. angustifolia in the Yucatan Peninsula in Mexico were analyzed. Analysis of three isozyme systems using starch gel electrophoresis indicated that while A. angustifolia populations have relatively high levels of variation, within each henequén cultivar all individuals were identical. This result corresponds to previous ethnobotanical and morphological analyses, which indicated severe loss of genetic variation of this domesticated plant as a consequence of the promotion by means of asexual propagation of only one cultivar since the middle of the last century. The three extant cultivars of henequén were distinct from each other. Two of them, Sac Ki (SK) and Yaax Ki (YK), could be matched within the progenitor, but Kitam Ki (KK) has a MDH electrophenotype not found in any of the plants growing inside the Yucatan Peninsula, but found in some A. angustifolia plants growing in the Mexican states of Oaxaca and Veracruz. A parsimony analysis of the morphological data indicated two lineages: that of SK and YK, cultivated cordage plants selected for stronger and longer fibers, whose sister group is the Tropical subdeciduous forest ecotype (SF), and that of all the other wild populations, which also included KK, the cultivated textile plants selected for finer fibers and nearly extinct in Yucatan. These results support the hypothesis of the yucatecan origin of SK and YK from the SF ecotype, as well as the hypothesis of a recent introduction of KK to the Yucatan Peninsula in a domestication trend that probably included also Chelem White (its cultivation being abandoned later).

This paper describes different elements leading to the success of cooperatives formed by indigenous Maya women of the Yucatan Peninsula in Mexico. These elements have shown to facilitate the sustainability (permanence over time) of the cooperatives and their presence in the market, while improving the work environment and enhancing the practice of honesty. All these elements have generated an increase in the number of clients and beneficiaries due to their trustable relationships. As can be appreciated in this study, indigenous Maya women living in the Yucatan Peninsula are demonstrating an innovative way to do business, which has resulted in greater social benefits and profitability through social capital, ethical leadership and monitoring of actions.

Trace gas emissions from tropical biomass fires: Yucatan Peninsula, Mexico

Previous studies of overwintering migratory birds in neotropical environments have found that species co-occur in the same habitats despite high diet overlap. Hence, discovering subtle diet differences within habitats can help explain patterns in bird species diversity. The Yucatan Peninsula in Mexico is an important region for overwintering migratory birds, but little is known about how habitat differences in food resources contribute to bird diversity. To address the knowledge gap, we compared the degree of overlap in the diet of all terrestrial migratory birds within and between mangrove and tropical dry forests on the Yucatan Peninsula’s northern coast. We collected data on the consumption of food items through direct observation of birds feeding on four transects in each habitat every week (12 weeks) during the non-breeding season (i.e., overwinter, December-February). We recorded 19 species, 15 species in mangrove and 15 species in forest, with 11 of those found in both habitats. In both habitats, diet overlap was high. However, species present only in the tropical dry forest had less overlap than species occurring in both habitats, indicating that diet specialization might restrict the range of habitats that a species can occupy. On the other hand, species present only in the mangrove had similar diet overlap to species present in both habitats. The diet variation that did exist was greater within than between habitats possibly due to intraspecific diet differences among different geographic locations. Although small, within-habitat diet differences might be key to allowing species to coexist locally in the Yucatan, thus supporting studies demonstrating a similar mechanism in other neotropical regions. More generally, the information we provide on bird diet can be used to discover whether threats like anthropogenic development precipitate species loss via altering the resource base upon which birds rely.

There is a lack of knowledge on the factors driving epiphytic community assemblage along water-limited environments. Epiphytic bromeliad and host communities were analyzed in a range of vegetation types, following a precipitation gradient from 500 to 1500 mm y−1. Plots were set up in scrub mangrove, coastal sand dune scrub, deciduous, semi-deciduous and sub-perennial forests within the Yucatan Peninsula in Mexico. Identity and abundance of hosts and epiphytes, as well as host height and seasonal microenvironmental variables, were recorded at each vegetation type. The study found epiphytic bromeliads to be mainly located in the lower canopy strata of all but the wettest site (sub-peren nial forest). Total epiphyte richness (estimated using species accumulation curves) increased with annual precipitation. Bromeliad species density decreased with vapor pressure deficit and increased with host species density. Semi-variograms and kriging analysis showed a high spatial correlation in bromeliad and host species density. The species composition, however, was unrelated to space, according to a Mantel test, but related to host species composition. The current study shows that diversity and structural integrity of the canopy may be as important as climate in the conservation of epiphytic composition in water-limited environments, where epiphytes are found in sheltered, lower canopy strata.

Although previous work has contributed to our knowledge of bilingual compound verbs (BCVs) in different code-switching varieties, there is scant research on the semantic nature of these innovative constructions. To fill this gap, the present study examines semantic aspects of BCVs in Northern Belize and the Yucatan Peninsula in Mexico, two sociohistorically connected communities where Spanish hacer ‘do’ BCVs have been attested. Drawing on two datasets, we analyzed the semantic domains that are most open to other-language lexical verbs as well as the potential use of these structures as identity markers. The analysis of 1,140 BCVs (903 in Northern Belize and 237 in Yucatan) revealed that whereas ‘education’ particularly favored English lexical verbs in Northern Belize, ‘nourishment’ was the semantic sub-category most open to Yucatec Maya lexical verbs in the Yucatan Peninsula. Notably, only hacer BCVs from Yucatan evince the incorporation of cultural elements and linguistic practices such as albur ‘word play’ to index a Yucatec Maya ethnolinguistic identity. Our findings highlight the importance that the nature of bilingualism and community linguistic norms have on the semantic use of BCVs.

The influence of biological and physicochemical soil properties on the variations in soil organic and inorganic carbon (OC and IC) contents at the soil surface was studied. Three-dimensional plots of variations in OC, IC and the correlated properties were obtained. Soils of the study area were classified as Aridisols and Entisols used as a rangeland. Soil samples were collected from 38 representative points with a wide range of physicochemical soil properties; in addition, three important microbiological indicators—dehydrogenase enzyme activity (DHA), soil basal respiration, and bacterial population—were analyzed. Variation partitioning analysis was carried out to assess the determining factors influencing soil OC and IC variations in soil surface. Additionally, the principal component analysis (PCA) was applied to explore the patterns of determinant soil variables. Variation partitioning demonstrated that the physicochemical soil properties were the determining variables in explaining the variations of both OC and IC. A remarkable portion of the variations remained unexplained by any of the two explanatory sets according to this analysis. Soil OC was not significantly related to the biological soil properties. Soil OC was inversely related to IC, clay, and sodium contents in the soil profiles. Soil type-specific vertical trends were observed for soil OC and IC. Soil conditions and pedogenic processes were deduced to have a major role in OC and IC spatial variations according to the results of soil type-specific trends of variation. The results of this study can be useful for better soil management and OC and IC prediction, or spatial distribution patterns modeling.

The Yucatan Peninsula is a karstic region with groundwater-dependent ecosystems and geological features such as karstic lakes. The objective of this research was to calculate the volume of water stored in this section of the aquifer and to describe the changes in the hydrochemistry of the lake Punta Laguna as a representative of karstic lakes in the Yucatan Peninsula. A bathymetry and calculation of the volume of water stored in the lake resulted in 5,198,505 m3 with a maximum depth measured of 26.6 m Physicochemical measurements were completed in surface and three vertical profiles to estimate the mass of nutrients and ions and to describe the current hydrochemistry. The lake is an oligotrophic one of mixed-typed water (chloride-calcium/magnesium), saturated or supersaturated with calcite, dolomite and aragonite due to limestone dissolution. No evidence obtain regarding the saline intrusion. The conclusion that we can derive from the data is that Punta Laguna is a tropical karstic lake in good condition with low anthropogenic influence, evolving hydrochemically speaking. The changes over a 20-year period suggest that there has been reverse ion exchange, evaporation and sulfate reduction.