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Gut bacteria help dung beetles metabolize nutrients contained and synthesize those unavailable in their food, depending on the ecological scenario in which they develop. However, less is known about the influence of environmental and behavioral factors on the taxonomic composition of bacterial gut communities in Scarabaeinae beetles. To address this research topic, we analyzed 13 tropical dung beetle species in the Los Tuxtlas Biosphere Reserve, Mexico, to understand how the beetle tribe, habitat, food preference, food relocation, and parental care influence the composition of gut bacterial communities. We found that the beetle tribe is the primary factor impacting the taxonomic composition of gut bacterial communities. Among them, Deltochilini displayed the highest variability in diversity due to the different combinations of habitat and food preferences among its species. On the other hand, the other tribes studied did not exhibit such variable combinations. Habitat emerged as the second most influential factor, with forest-dwelling beetles displaying higher diversity. This can be attributed to the heterogeneous environments within tropical forests, which offer a greater diversity of food resources. In contrast, grassland beetles, living in more homogeneous environments and relying on cow feces as their main food source, exhibited lower diversity. Our findings suggest a correlation between bacterial diversity and food resource availability in complex habitats, such as tropical forests, which offer a wider array of food sources compared to simpler environments like grasslands. [ABSTRACT FROM AUTHOR]

Background: Land use is a major factor determining stream water physicochemistry. However, most streams move from one land use type to another as they drain their watersheds. Here, we studied three land use scenarios in a tropical cloud forest zone in Mexico. We addressed three main goals, to: (1) assess how land use scenarios generate different patterns in stream physicochemical characteristics; (2) explore how seasonality (i.e., dry, dry-to-wet transition, and wet seasons) might result in changes to those patterns over the year; and (3) explore whether physicochemical patterns in different scenarios resulted in effects on biotic components (e.g., algal biomass). Methods: We studied Tropical Mountain Cloud Forest streams in La Antigua watershed, Mexico. Streams drained different three scenarios, streams with (1) an upstream section draining forest followed by a pasture section (F-P), (2) an upstream section in pasture followed by a forest section (P-F), and (3) an upstream forest section followed by coffee plantation (F-C). Physicochemistry was determined at the upstream and downstream sections, and at the boundary between land uses. Measurements were seasonal, including temperature, dissolved oxygen, conductivity, and pH. Water was analyzed for suspended solids, alkalinity, silica, chloride, sulfate, magnesium, sodium, and potassium. Nutrients included ammonium, nitrate, and phosphorus. We measured benthic and suspended organic matter and chlorophyll. Results: Streams presented strong seasonality, with the highest discharge and suspended solids during the wet season. Scenarios and streams within each scenario had distinct physicochemical signatures. All three streams within each scenario clustered together in ordination space and remained close to each other during all seasons. There were significant scenario-season interactions on conductivity (F = 9.5, P < 0.001), discharge (F = 56.7, P < 0.001), pH (F = 4.5, P = 0.011), Cl- (F = 12.2, P < 0.001), SO42- (F = 8.8, P < 0.001) and NH4+ (F = 5.4, P = 0.005). Patterns within individual scenarios were associated with stream identity instead of land use. Both P-F and F-C scenarios had significantly different physicochemical patterns from those in F-P in all seasons (Procrustes analysis, m12 = 0.05-0.25; R = 0.86-0.97; P < 0.05). Chlorophyll was significantly different among scenarios and seasons (F = 5.36, P = 0.015, F = 3.81, P = 0.42, respectively). Concentrations were related to physicochemical variables more strongly during the transition season. Conclusion: Overall, land use scenarios resulted in distinctive water physicochemical signatures highlighting the complex effects that anthropogenic activities have on tropical cloud forest streams. Studies assessing the effect of land use on tropical streams will benefit from assessing scenarios, rather than focusing on individual land use types. We also found evidence of the importance that forest fragments play in maintaining or restoring stream water physicochemistry. [ABSTRACT FROM AUTHOR]

The occurrence of cyanobacterial blooms has increased globally over the last decades, with the combined effect of climate change and eutrophication as its main drivers. The seasonal dynamic of cyanobacterial blooms is a well-known phenomenon in lakes and reservoirs in temperate zones. Nevertheless, in the tropics, most studies have been performed in shallow and artificial lakes; therefore, the seasonal dynamic of cyanobacterial blooms in deep and eutrophic tropical lakes is still under research. We studied the seasonal variation of the phytoplankton community and the factors associated with Microcystis aeruginosa blooms along the water column of Lake Alberca de Tacámbaro, a warm monomictic crater lake located in Mexico, during 2018 and 2019. According to previous studies performed in 2006 and 2009-2010, this lake was mesotrophic-eutrophic, with Chlorophyta and Bacillariophyta as the dominant groups of the phytoplankton community. During 2018 and 2019, the lake was eutrophic and occasionally, hypertrophic. The dominant species was M. aeruginosa, forming blooms at different depths, and mostly, during autumn and winter months. These findings suggest that M. aeruginosa in Lake Alberca de Tacámbaro displays seasonal and spatial population dynamics. Total phosphorus, dissolved inorganic nitrogen, water temperature and photosynthetically active radiation were the environmental factors related to M. aeruginosa blooms. Our results suggest that the changes in the structure of the phytoplankton community through time, and M. aeruginosa blooms in Lake Alberca de Tacámbaro, are mainly related to changes in land use from forest to farmland in areas adjacent to the lake, which promoted its eutrophication in the last years through runoffs. Comparative studies with other deep and eutrophic lakes will allow us to gain a deeper understanding of the dynamic of cyanobacterial blooms in natural and artificial water reservoirs strongly stressed by human activities. [ABSTRACT FROM AUTHOR]

Background. Anthropized landscapes play a crucial role in biodiversity conservation, as they encompass about 90% of the remaining tropical forest. Effective conservation strategies require a deep understanding of how anthropic disturbances determine diversity patterns across these landscapes. Here, we evaluated how attributes and assembly mechanisms of dung beetle communities vary across the Selva El Ocote Biosphere Reserve (REBISO) landscape. Methods. Community attributes (species diversity, abundance, and biomass) were assessed at the landscape scale, using spatial windows and vegetation classes. Windows were categorized as intact, variegated, or fragmented based on their percent cover of tropical forest. The vegetation classes analyzed were tropical forest, second-growth forest, and pastures. Results. We collected 15,457 individuals and 55 species. Variegated windows, tropical forests, and second-growth forests showed the highest diversity values, while the lowest values were found in intact windows and pastures. Landscape fragmentation was positively and strongly related to dung beetle diversity and negatively related to their abundance; biomass was positively associated with forest cover. Beta diversity was the primary driver of the high dung beetle diversity in the landscape analyzed. Discussion. The landscape heterogeneity and its biodiversity-friendly matrix facilitate the complementarity of dung beetle assemblages in the Selva El Ocote Biosphere Reserve. Random processes govern beta diversity patterns in intact and variegated windows. Therefore, vegetation cover in the region is sufficient to maintain a continuous flow of dung beetles between forested landscape segments. However, intense anthropic disturbances acted as deterministic environmental filters in fragmented windows and pastures sites, leading to biotic homogenization processes. Our results suggest that increasing habitat variegation in highly fragmented sites is an effective strategy to prevent or buffer homogenization processes in the REBISO landscape. [ABSTRACT FROM AUTHOR]

The article discusses a study on the distribution of dung and carrion beetles in a fragmented tropical rain forest. In this study insects were used to evaluate the impact of habitat modification and landscape fragmentation on biological diversity. Forest fragments and forest-pasture edges shared the highest number of species and function as hard edges which prevent movement among forest fragments. These allow the forest beetles to move between the fragments.

We analyzed mate recognition and the cooperative behavior of male-female pairs in Canthon cyanellus cyanellus LeConte (Coleoptera: Scarabaeidae), a carrion-feeding scarab, during food ball rolling among five populations found in tropical forest fragments on the eastern coastal plains of Mexico. Sexual recognition in this species is mostly mediated by chemical cues. Intrapopulation and male-female pairs formed with individual from populations <400 km apart showed cooperative behavior (joint rolling of the food ball by both members). However, male-female pairs from populations <400 km apart showed no cooperative behavior (individual food ball rolling by one of the partners and fights), although they also rolled food balls together. In male-female pairs from the more distant populations (≥600 km apart), >50% fought for food balls. Brood ball production by females and the number of eclosed beetles from the northern population and from the crosses between individuals from the most distant populations were lower than those of other intra- or interpopulation combinations. Gas chromatograph mass spectroscopy of cuticular extract showed that the southern population had 48 surface compounds, 18 of them not present in the northern or intermediate populations. The intermediate population had 41 compounds, 11 of them exclusive. However, the northern population had 24 compounds and only one was exclusive. The lack of cooperative interaction among male-female pairs from distant populations, along with their reduced reproductive success and the differences in cuticular composition between populations, suggest that extreme populations of Canthon c. cyanellus are in a process of incipient speciation. [ABSTRACT FROM AUTHOR]

The purpose of this study was to characterize five crater lakes in Los Tuxtlas, Mexico, on the basis of morphological, physical, chemical, and biological features. A bathymetric map of each lake was obtained and morphometric parameters were calculated. Physical and chemical parameters (temperature, transparency, nutrients, pH, conductivity, cations) and chlorophyll a were measured for three periods: the cold season (January), the dry season (May), and the rainy season (October) of 2000. The trophic state of each lake was determined using Carlson's indices for transparency and chlorophyll a. The lakes studied have the morphometric characteristics of maar-type volcanic lakes. Majahual, Chalchoapan, and Manantiales are the deepest lakes with elliptical basins and are classified as warm monomictic systems; Verde and Mogo are shallow lakes with conic basins and are warm polymictic. Majahual and Chalchoapan had an anoxic hypolimnion, while at Manantiales a metalimnetic oxygen maximum was measured. Sodium was the dominant cation in the five lakes, while bicarbonate was the dominant anion. Nutrient and chlorophyll a concentrations, transparency, and trophic indices suggest that Chalchoapan, Verde, and Mogo are eutrophic lakes with tendencies toward hypereutrophy; Manantiales and Majahual, in contrast, can be classified as mesotrophic lakes. The trophic state of lakes was indirectly related to deforestation and to the use of agricultural fertilizer in Los Tuxtlas as well as to certain morphometric characteristics. [ABSTRACT FROM AUTHOR]

Soil and water characteristics in micro basins with different land uses/land cover (LULC) can influence riparian vegetation diversity, stream water quality, and benthic diatom diversity. We analyzed 18 streams in the upper part of the La Antigua River basin, México, surrounded by cloud forests, livestock pastures, and coffee plantations. Concentrations of P, C, and N were elevated in the humus of forested streams compared to other land uses. In contrast, cations, ammonium, and total suspended solids (TSS) of water streams were higher in pastures and coffee plantations. These results indicate that LULC affects stream chemistry differently across land uses. Vegetation richness was highest (86-133 spp.) in forest streams and lowest in pastures (46-102), whereas pasture streams had the greatest richness of diatoms (9-24), likely due to higher light and temperatures. Some soil and water characteristics correlated with both true diversity and taxonomic diversity; soil carbon exchange capacity (CEC) correlated with vegetation diversity (r = 0.60), while water temperature correlated negatively (r =  - 0.68). Diatom diversity was related to soil aluminum (r =  - 0.59), magnesium (r = 0.57), water phosphorus (r = 0.88), and chlorophyll (r = 0.75). These findings suggest that land use affects riparian vegetation, while physical and chemical changes influence diatom diversity in stream water and soil. The lack of correlation between vegetation and diatom diversity indicates that one cannot predict the other. This research is an essential first step in understanding how land use changes impact vegetation and diatom diversity in mountain landscapes, providing valuable insights for environmental monitoring and conservation efforts in tropical cloud forests., (© 2024. The Author(s), under exclusive licence to Springer Nature Switzerland AG.)