Plant age-dependent dynamics of annatto pigment (bixin) biosynthesis in Bixa orellana.

Age affects the production of secondary metabolites, but how developmental cues regulate secondary metabolism remains poorly understood. The achiote tree (Bixa orellana L.) is a source of bixin, an apocarotenoid used in diverse industries worldwide. Understanding how age-dependent mechanisms control bixin biosynthesis is of great interest for plant biology and for economic reasons. Here we overexpressed miRNA156 (miR156) in B. orellana to comprehensively study the effects of the miR156-SQUAMOSA PROMOTER BINDING PROTEIN-LIKE (SPL) module on age-dependent bixin biosynthesis in leaves. Overexpression of miR156 in annatto plants (miR156ox) reduced BoSPL transcript levels, impacted leaf ontogeny, lessened bixin production, and increased abscisic acid levels. Modulation of expression of BoCCD4-4 and BoCCD1, key genes in carotenoid biosynthesis, was associated with diverting the carbon flux from bixin to abscisic acid in miR156ox leaves. Proteomic analyses revealed an overall low accumulation of most secondary metabolite-related enzymes in miR156ox leaves, suggesting that miR156-targeted BoSPLs may be required to activate several secondary metabolic pathways. Our findings suggest that the conserved BomiR156-BoSPL module is deployed to regulate leaf dynamics of bixin biosynthesis, and may create novel opportunities to fine-tune bixin output in B. orellana breeding programs.

Evaluation of different ratios of neutral detergent-soluble carbohydrate fractions on performance, ingestive behavior, and nitrogen balance in dairy goats.

Cell components soluble in neutral detergent are a diverse group, both compositionally and nutritionally. The present study aimed to evaluate production responses, behavior (eating, ruminating, and idling), and nitrogen balance of dairy goats fed different ratios of neutral detergent-soluble carbohydrate fractions. Five multiparous Alpine does with mean ± SD initial body mass of 49.5 ± 7.9 kg and 60 days of lactation were randomly assigned in a 5 × 5 Latin square design. The treatments were the ratios of starch (starch associated with soluble sugar [StSS]) to neutral detergent-soluble fiber (NDSF) (StSS:NDSF): 0.89, 1.05, 1.24, 1.73, and 2.92. No effect was observed (P > 0.05) of StSS:NDSF on the intakes of neutral detergent fiber (NDF) and NDSC. However, DM intake showed a quadratic behavior (P = 0.049). The ingestive behavior was affected by StSS:NDSF linearly increased (P = 0.002) the feeding efficiency. The increase in StSS:NDSF caused a linear increase in fecal (P = 0.011), urinary (P < 0.001), and milk nitrogen excretion (P = 0.024). The increase in StSS:NDSF affected (P = 0.048) milk yield and net energy lactation (P = 0.036). In conclusion, dairy goats experience reduced dry matter intake and milk yield when subjected to high-NDSC diets, specifically those above 1.24 StSS:NDSF ratio. Elevated NDSC levels in the diets lead to decreased feeding time, whereas rumination remains unaffected. Nitrogen losses in goats increase linearly with high-NDSC diets, and a significant impact on nitrogen balance.

Evaluation of the type of silo associated or not with additives on the nutritional value, aerobic stability, and microbiology of pearl millet silage.

The objective of this study was to evaluate the effect of the silo type with the use or not of additives on chemical composition, in vitro gas production, fermentative losses, aerobic stability, fermentative profile, and microbial population of the pearl millet silage. We used a randomized block design in a 2 × 3 factorial scheme, with two types of silos (plastic bags and PVC silos) and three additives ([CON] without additive; 50 g of ground corn [GC], and Lactobacillus plantarum and Propionibacterium acidipropionici, with five replicates per treatment. We evaluated the chemical analyses, in vitro gas production, losses, aerobic stability, pH, ammoniacal nitrogen, and microbial population of the silages. The use of GC in the ensiling process improved the chemical composition of the silages. The additives and the type of silo did not affect (p > 0.05) the gas production kinetics, ammoniacal nitrogen, and population of lactic acid bacteria and fungi. Thus, the use of ground corn improved the nutritional value of the pearl millet silage. In turn, the inoculant provided better aerobic stability for the pearl millet silage. The plastic bag silos without vacuum were not efficient in the ensiling process like the PVC silos, which resulted in low-quality silage.

Reduction of heat stress pressure and activation of photosystem II repairing system are crucial for citrus tolerance to multiple abiotic stress combination.

Drought, heat and high irradiance are abiotic stresses that negatively affect plant development and reduce crop productivity. The confluence of these three factors is common in nature, causing extreme situations for plants that compromise their viability. Drought and heat stresses increase the saturation of the photosystem reaction centers, increasing sensitivity to high irradiance. In addition, these stress conditions affect photosystem II (PSII) integrity, alter redox balance of the electron transport chain and decrease the photosynthetic rate. Here, we studied the effect of the stress combinations on the photosynthetic apparatus of two citrus genotypes, Carrizo citrange (Citrus sinensis × Poncirus trifoliata) and Cleopatra mandarin (Citrus reshni). Results obtained showed that physiological responses, such as modulation of stomatal aperture and transpiration rate, aimed to reduce leaf temperature, are key to diminishing heat impact on photosynthetic apparatus and increasing tolerance to double and triple combinations of drought, high irradiance and high temperatures. By using transcriptomic and proteomic analyses, we have demonstrated that under these abiotic stress combinations, Carrizo plants were able to increase expression of genes and proteins related to the photosystem repairing machinery (which better maintained the integrity of PSII) and other components of the photosynthetic apparatus. Our findings reveal crucial physiological and genetic responses in citrus to increase tolerance to the combination of multiple abiotic stresses that could be the basis for breeding programs that ensure a sustainable citrus production.

Citrus rootstocks modify scion antioxidant system under drought and heat stress combination.

KEY MESSAGE: The activation of the antioxidant system under stress combination is a transmissible trait from the rootstock to the scion. Therefore, rootstock selection is key to improve crop performance and a sustainable production under changing climate conditions. Climate change is altering weather conditions such as mean temperatures and precipitation patterns. Rising temperatures, especially in certain regions, accelerates soil water depletion and increases drought risk, which affects agriculture yield. Previously, our research demonstrated that the citrus rootstock Carrizo citrange (Citrus sinensis × Poncirus trifoliata) is more tolerant than Cleopatra mandarin (C. reshni) to drought and heat stress combination, in part, due to a higher activation of the antioxidant system that alleviated damage produced by oxidative stress. Here, by using reciprocal grafts of both genotypes, we studied the importance of the rootstock on scion performance and antioxidant response under this stress combination. Carrizo rootstock, under stress combination, positively influenced Cleopatra scion by reducing H2O2 accumulation, increasing superoxide dismutase (SOD) and ascorbate peroxidase (APX) enzymatic activities and inducing SOD1, APX2 and catalase (CAT) protein accumulations. On the contrary, Cleopatra rootstock induced decreases in APX2 expression, CAT activity and SOD1, APX2 and CAT contents on Carrizo scion. Taken together, our findings indicate that the activation of the antioxidant system under stress combination is a transmissible trait from the rootstock to the scion and highlight the importance of the rootstock selection to improve crop performance and maintain citrus yield under the current scenario of climate change.

Feed intake, digestibility, and energy contents in growing bull fed pineapple crop waste silage in different planes of nutrition.

The objective of this study was to nutritionally evaluate the use of pineapple crop waste silage in the feeding of growing bull in different planes of nutrition. We used eight non-castrated growing bull housed in individual covered pens, provided with free access to water and individual trough. Two balanced Latin squares conducted simultaneously were used. Treatments consisted of four planes of nutrition (L), formed by multiples of maintenance, i.e., L = ME/Mm; they were ME/Mm, ME/1.5Mm, ME/2Mm, and ME/2.7Mm. The intake of nutrients in diets was determined by the difference between the total mass of food offered and the mass of orts. To determine nutrient digestibility and nitrogen balance, total feces, and urine, collections were performed for seven consecutive days in each animal per period. The increase in planes of nutrition affected (P < 0.05) nutrient intake between L = 1 and L = 1.5. However, there was no effect nutrients intake to 1.5, 2, and 2.7. Nutrient digestibility was affected by the increase in planes of nutrition (P < 0.05), except for dCF (P = 0.0659). Digestible and metabolizable energies were affected (P < 0.05) by the increase in nutritional plans, as well as nitrogen balance. In conclusion, the pineapple crop waste silage presents itself as a good forage alternative for cattle diets, especially during forage shortage periods. Inclusion in the diet at 2.7 × the maintenance level does not compromise growing bull performance. However, the increases in planes of nutrition reduce the digestible energy contents of the diet.

Performance, digestibility, microbial protein synthesis, and body composition of Brangus x Zebu steers on tropical pasture receiving supplementation.

The use of additional supplement can affect ruminant performance by increasing the animal weight gain and maximizing profits from the activity. Thus, the objective of this study was to evaluate the influence of protein-energy supplementation on microbial synthesis, animal performance, nutrient digestibility, and body composition of Brangus x Zebu steers on pasture. The experiment lasted 160 days and included 36 animals divided into two groups; 18 steers received protein-energy supplementation (PES), and the other 18 received non-supplementation (NPES). Individual pasture intake and nutrient digestibility were estimated using the double indicator technique-chromium oxide and lignin in potassium permanganate. Spot urine samples were collected from 36 animals to determine creatinine, allantoin, and uric acid concentrations. All animals were slaughtered at the end of the experiment to evaluate body composition. There was increase in intake (P < 0.001) and dry matter digestibility (P = 0.01); it resulted in higher animal weight gain (P < 0.001) receiving supplementation. However, there was no difference (P > 0.05) in pasture nutrient intake between treatments. Supplementation increased microbial nitrogen (P < 0.001). For body composition, the model identity test that was applied showed no difference (P > 0.05) between the models, so it was adopted a common equation for both treatments. There was no difference (P > 0.05) for body composition between treatments. Therefore, the use of protein-energy supplementation for steers on pasture allowed higher microbial protein synthesis and better utilization of nutrients, which resulted in better animal performance. The use of protein-energy supplementation at 0.6% BW did not alter the carcass composition of Brangus x Zebu steers. However, it recommends protein-energy supplementation in pasture systems during the rainy period or using an irrigation system.

Phylogeographic analyses of the pampas cat (Leopardus colocola; Carnivora, Felidae) reveal a complex demographic history.

The pampas cat is a small felid that occurs in open habitats throughout much of South America. Previous studies have revealed intriguing patterns of morphological differentiation and genetic structure among its populations, as well as molecular evidence for hybridization with the closely related L. tigrinus. Here we report phylogeographic analyses encompassing most of its distribution (focusing particularly on Brazilian specimens, which had been poorly sampled in previous studies), using a novel dataset comprising 2,143 bp of the mitogenome, along with previously reported mtDNA sequences. Our data revealed strong population strutucture and supported a west-to-east colonization process in this species' history. We detected two population expansion events, one older (ca. 200 thousand years ago [kya]) in western South America and another more recent (ca. 60-50 kya) in eastern areas, coinciding with the expansion of savanna environments in Brazil. Analyses including L. tigrinus individuals bearing introgressed mtDNA from L. colocola showed a complete lack of shared haplotypes between species, indicating that their hybridization was ancient. Finally, we observed a close relationship between Brazilian/Uruguayan L. colocola haplotypes and those sampled in L. tigrinus, indicating that their hybridization was likely related to the demographic expansion of L. colocola into eastern South America.

Plant regeneration capacity in seeds of three species of Miconia (Melastomataceae) may be related to endogenous polyamine profiles.

In plant tissue culture, differences in endogenous levels of species-specific plant growth regulators (PGRs) may explain differences in regenerative capacity. In the case of polyamines (PAs), their dynamics and distribution may vary between species, genotypes, tissues, and developmental pathways, such as sexual reproduction and apomixis. In this study, for the first time, we aimed to assess the impact of varying endogenous PAs levels in seeds from distinct reproductive modes in Miconia spp. (Melastomataceae), on their in vitro regenerative capacity. We quantified the free PAs endogenous content in seeds of Miconia australis (obligate apomictic), Miconia hyemalis (facultative apomictic), and Miconia sellowiana (sexual) and evaluated their in vitro regenerative potential in WPM culture medium supplemented with a combination of 2,4-dichlorophenoxyacetic acid (2,4-D) and 6-benzylaminopurine (BAP). The morphogenic responses were characterized by light microscopy and scanning electron microscopy and discussed regarding the endogenous PAs profiles found. Seeds of M. sellowiana presented approximately eight times more putrescine than M. australis, which was associated with a higher percentage of regenerated calluses (76.67%) than M. australis (5.56%). On the other hand, spermine levels were significantly higher in M. australis. Spermine is indicated as an inhibitor of auxin-carrying gene expression, which may have contributed to its lower regenerative capacity under the tested conditions. These findings provide important insights into in vitro morphogenesis mechanisms in Miconia and highlight the significance of endogenous PA levels in plant regeneration. These discoveries can potentially optimize future regeneration protocols in Miconia, a plant group still underexplored in this area.

Effect of odontoplasty on intake, nutrient digestibility, and intake time of tifton hay in ponies.

We aimed to evaluate the effects of dental correction on voluntary nutrient intake, time of intake, apparent digestibility and fecal particle size in Brazilian ponies. Twelve mares, with no history of previous dental treatments, housed in individual pens and fed a diet based on tifton 85 were used. The study comprised two consecutive experimental phases, pre and post dental treatment. Each phase consisted of 15 days for adaptation to the pen and treatment and 5 days for data collection, totaling 20 days. To calculate nutrient intake and digestibility coefficients, samples of diets, leftovers, and feces were analyzed for dry matter (DM), crude protein (CP), neutral detergent fiber (NDF), acid detergent fiber (ADF), crude fat (CF), mineral matter (MM), organic matter (OM), and non-fiber carbohydrates (NFC). Food intake time was recorded using a digital video recorder. Fecal particles were analyzed by wet sieving. Dental correction did not influence the intake of DM, CP, NDF, CF, and OM by the animals. However, there was an increase in NFC intake from 0.12 kg to 0.14 kg and in food intake time from 654.50 ± 138.98 to 774.95 ± 167.14. There was a decrease in the digestibility of CP from 0.08 kg to 0.04 kg and an increase in the digestibility of NDF from 0.65 kg to 0.82 kg. Although odontoplasty increased the time of hay intake and the digestibility of the fibrous fractions of the feed of ponies, it did not influence the intake of nutrients and the size of the fecal particles.

Distribution and habitat use patterns of the endangered Central American clouded oncilla (Leopardus pardinoides oncilla) in Costa Rica.

Montane cloud forests are highly threatened ecosystems that are vulnerable to climate change. These complex habitats harbor many species that suffer the negative consequences of this global phenomenon, such as shifts in their distribution and habitat use. The Central American clouded oncilla (Leopardus pardinoides oncilla) is the smallest and most endangered wild cat in Mesoamerica and is primarily reported in cloud forests throughout its distribution. The species is poorly understood, with no studies conducted in Central America assessing its habitat preferences. To bridge this knowledge gap, we sampled two mountain ranges in Costa Rica with camera traps and conducted an occupancy analysis to understand the anthropogenic and environmental features that influence oncilla habitat use within them. Additionally, we conducted spatial predictions of habitat use across its northern and southern range in Costa Rica to identify priority conservation areas for the species. We found that Central American clouded oncilla habitat use is driven primarily by environmental factors. Our results showed that oncillas select habitats with denser tree cover at high elevations, closer to permanent water sources, which may provide them with high prey density and a favorable habitat structure for their survival. Spatial predictions identified two main regions as conservation priority areas where threat mitigation efforts and monitoring should be implemented: the Caribbean slope of the Talamanca mountains, and the Arenal-Monteverde forest complex. The occupancy modeling approach turned out to be very useful to assess the spatial associations of the species with the environment and mapping the conservation priority areas. Future research and mitigation actions should focus on potential threats that could negatively impact Central American clouded oncilla populations and habitat use, including the role of mesopredators and feral species.

Ecological modeling, biogeography, and phenotypic analyses setting the tiger cats' hyperdimensional niches reveal a new species.

Recently, the tiger-cat species complex was split into Leopardus tigrinus and Leopardus guttulus, along with other proposed schemes. We performed a detailed analysis integrating ecological modeling, biogeography, and phenotype of the four originally recognized subspecies-tigrinus, oncilla, pardinoides, guttulus-and presented a new multidimensional niche depiction of the species. Species distribution models used > 1400 records from museums and photographs, all checked for species accuracy. Morphological data were obtained from institutional/personal archives. Spotting patterns were established by integrating museum and photographic/camera-trap records. Principal component analysis showed three clearly distinct groups, with the Central American specimens (oncilla) clustering entirely within those of the Andes, namely the pardinoides group of the cloud forests of the southern Central-American and Andean mountain chains (clouded tiger-cat); the tigrinus group of the savannas of the Guiana Shield and central/northeastern Brazil (savanna tiger-cat); and the guttulus group in the lowland forests of the Atlantic Forest domain (Atlantic Forest tiger-cat). This scheme is supported by recent genetic analyses. All species displayed different spotting patterns, with some significant differences in body measurements/proportions. The new distribution presented alarming reductions from the historic range of - 50.4% to - 68.2%. This multidimensional approach revealed a new species of the elusive and threatened tiger-cat complex.

Interspecific patterns of small cats in an intraguild-killer free area of the threatened Caatinga drylands, Brazil.

The semi-arid Caatinga is the largest dry forest ecoregion in the Americas; nevertheless, it is experiencing alarming rates of habitat loss. Most vegetation fragments in the biome are either unprotected or within private lands; however, these private areas are susceptible to anthropogenic activity, and often have the presence of non-native wildlife such as domestic dogs and cats. Two small felid species, the northern tiger cat and the jaguarundi co-occur throughout the Caatinga and have overlapping niches, which require segregation mechanisms to avoid interference competition. Assessing these species strategies for coexistence is crucial, as it can guide conservation actions. With this aim, a private ranch in the Brazilian Caatinga drylands was surveyed and multi-species occupancy models were used to assess co-occurrence patterns between northern tiger cats and jaguarundis. The degree of temporal overlap between both felids and domestic dogs and cats were also assessed. Evidence was found of positive co-occurrence between tiger cats and jaguarundis, suggesting a lack of spatial segregation at our study site; and low temporal overlap was found between both felids, with tiger cats being nocturnal and jaguarundis diurnal. High temporal overlap was found though between domestic dogs and both wild felid species. Our results suggest that small felids can coexist in private areas of the Caatinga with sufficient habitat. However, there is a need to highlight the potential threat of disease transmission by non-native carnivores as something that should be addressed in these private landscapes.

Effects of forage quality and particle size on feed intake and ruminoreticulum content of goats.

The aim was to evaluate the effect of particle size and hay quality on feed intake, granulometric profile, and composition of the ruminoreticulum content in goats. We used 54 Alpine bucks in a completely randomized design with a factorial arrangement of 3 × 3. Treatments were a combination of Bermuda grass hay (Cynodon dactylon) with three quality levels: high (35 days), medium (50 days), and low (65 d) harvested at regrowth times. Were evaluated three particle sizes: small (16% ≥4.76 mm), medium (48% ≥4.76 mm), and large (75% ≥4.76 mm), which accounted for 66%, 75%, and 94% of physically effective fiber, respectively. Samples of offered diet, intake, and ruminoreticulum content were used to generate the granulometric profile. The offered diet, intake, and ruminoreticulum content presented different granulometric profiles regarding hay quality and particle size. Dry matter intake (DMI) and neutral detergent fiber intake (NDFI) increased (P < 0.05) when low-quality hay and large particles were offered. However, when particle size in low-quality hay was reduced, DMI and NDF decreased (P < 0.05). When analyzing the ruminoreticulum content (DM, NDF, peNDF, and indigestible DM), we did not observe any effect (P > 0.05) of hay quality or particle size on the variables. Thus, reducing hay quality and increasing particle size increase dry matter and fiber intake, presenting an interaction between forage quality and particle size. Forage quality and particle size promote intense selective behavior and chewing, which leads to a homogeneous content of particle profile in ruminoreticulum and a uniform average retention time.

Omics analyses in citrus reveal a possible role of RNA translation pathways and Unfolded Protein Response regulators in the tolerance to combined drought, high irradiance, and heat stress.

Environmental changes derived from global warming and human activities increase the intensity and frequency of stressful conditions for plants. Multiple abiotic factors acting simultaneously enhance stress pressure and drastically reduce plant growth, yield, and survival. Stress combination causes a specific stress situation that induces a particular plant response different to the sum of responses to the individual stresses. Here, by comparing transcriptomic and proteomic profiles to different abiotic stress combinations in two citrus genotypes, Carrizo citrange (Citrus sinensis × Poncirus trifoliata) and Cleopatra mandarin (Citrus reshni), with contrasting tolerance to different abiotic stresses, we revealed key responses to the triple combination of heat stress, high irradiance and drought. The specific transcriptomic response to this stress combination in Carrizo was directed to regulate RNA metabolic pathways and translation processes, potentially conferring an advantage with respect to Cleopatra. In addition, we found endoplasmic reticulum stress response as common to all individual and combined stress conditions in both genotypes and identified the accumulation of specific groups of heat shock proteins (HSPs), such as small HSPs and HSP70s, and regulators of the unfolded protein response, BiP2 and PDIL2-2, as possible factors involved in citrus tolerance to triple stress combination. Taken together, our findings provide new insights into the acclimation process of citrus plants to multiple stress combination, necessary for increasing crop tolerance to the changing climatic conditions.

A Potential Role for the Ketogenic Diet in Alzheimer's Disease Treatment: Exploring Pre-Clinical and Clinical Evidence.

Given the remarkable progress in global health and overall quality of life, the significant rise in life expectancy has become intertwined with the surging occurrence of neurodegenerative disorders (NDs). This emerging trend is poised to pose a substantial challenge to the fields of medicine and public health in the years ahead. In this context, Alzheimer's disease (AD) is regarded as an ND that causes recent memory loss, motor impairment and cognitive deficits. AD is the most common cause of dementia in the elderly and its development is linked to multifactorial interactions between the environment, genetics, aging and lifestyle. The pathological hallmarks in AD are the accumulation of ß-amyloid peptide (Aß), the hyperphosphorylation of tau protein, neurotoxic events and impaired glucose metabolism. Due to pharmacological limitations and in view of the prevailing glycemic hypometabolism, the ketogenic diet (KD) emerges as a promising non-pharmacological possibility for managing AD, an approach that has already demonstrated efficacy in addressing other disorders, notably epilepsy. The KD consists of a food regimen in which carbohydrate intake is discouraged at the expense of increased lipid consumption, inducing metabolic ketosis whereby the main source of energy becomes ketone bodies instead of glucose. Thus, under these dietary conditions, neuronal death via lack of energy would be decreased, inasmuch as the metabolism of lipids is not impaired in AD. In this way, the clinical picture of patients with AD would potentially improve via the slowing down of symptoms and delaying of the progression of the disease. Hence, this review aims to explore the rationale behind utilizing the KD in AD treatment while emphasizing the metabolic interplay between the KD and the improvement of AD indicators, drawing insights from both preclinical and clinical investigations. Via a comprehensive examination of the studies detailed in this review, it is evident that the KD emerges as a promising alternative for managing AD. Moreover, its efficacy is notably enhanced when dietary composition is modified, thereby opening up innovative avenues for decreasing the progression of AD.

Assessing microhabitat, landscape features and intraguild relationships in the occupancy of the enigmatic and threatened Andean tiger cat (Leopardus tigrinus pardinoides) in the cloud forests of northwestern Colombia.

Mesocarnivores play a key role in ecosystem dynamics through the regulation of prey populations and are sensitive to environmental changes; thus, they are often considered good model organisms for conservation planning. However, data regarding the factors that influence the habitat use of threatened small wild felids such as the Andean tiger cat (Leopardus tigrinus pardinoides) are scarce. We conducted a two-year survey with 58 camera trap stations to evaluate the determinants of Andean tiger cat habitat use in three protected areas in the Middle Cauca, Colombia. We developed site occupancy models and found that Andean tiger cat habitat use increased with leaf litter depth at intermediate elevations and far from human settlements. Through conditional cooccurrence models, we found that Andean tiger cat habitat use was invariant to the presence of prey or potential intraguild competitors and killers/predators, but its detectability increased when they were present and detected. This suggests that Andean tiger cats may be more likely to be detected in sites with high prey availability. We found that Andean tiger cats preferred sites with deep leaf litter, which is a particular feature of cloud forests that provides suitable conditions for ambush hunting and hiding from intraguild enemies. Our results showed that Andean tiger cats avoided human settlements, which may minimize potential mortality risks in those areas. Moreover, the restricted use of middle elevations by Andean tiger cats suggested that they could be used as a sentinel species to track the effects of climate change since their suitable habitat is likely to be projected upward in elevation. Future conservation actions must be focused on identifying and mitigating human-related threats close to the Andean tiger cat habitat while preserving microhabitat conditions and the existing networks of protected areas.

The dominant mesopredator and savanna formations shape the distribution of the rare northern tiger cat (Leopardus tigrinus) in the Amazon.

Understanding the distribution patterns of threatened species is central to conservation. The Amazonian distribution of the northern tiger cat (N-tiger cat, Leopardus tigrinus) and its interspecific relationship with the ocelot, its potential intraguild killer, are intriguing. Here, we combined presence/absence records with species distribution models (SDMs) to determine N-tiger cat occurrence in the Amazon. We also modeled ocelot density from 46 published estimates. The N-tiger cat's presence in the Amazon was negatively influenced by ocelot density and net primary productivity and positively influenced by savannas and precipitation in the driest month. The best-fitting model predicted highly patchy N-tiger cat occurrence over an area of 236,238.67 km2, almost exclusively in savanna enclaves. Additionally, 312,348 camera trap-days at 49 sites in the Amazon revealed no N-tiger cats. The ocelot densities were significantly higher in areas with denser vegetation cover and warmer habitats, with predicted densities ≥ 0.6 ind/km2 throughout most of the biome. The lowest ocelot densities (≤ 0.06 ind/km2) were observed along the predicted range of N-tiger cats. Our findings highlight that the N-tiger cat's presence in the Amazon is restricted to savannas and highly influenced by ocelot density, emphasizing the importance of including species interactions in SDMs.

Composition of terrestrial mammal assemblages and their habitat use in unflooded and flooded blackwater forests in the Central Amazon.

Several forest types compose the apparently homogenous forest landscape of the lowland Amazon. The seasonally flooded forests (igapós) of the narrow floodplains of the blackwater rivers of the Amazon basin support their community of animals; however, these animals are required to adapt to survive in this environment. Furthermore, several taxa are an important source of seasonal resources for the animals in the adjacent unflooded forest (terra firme). During the low-water phase, the igapó becomes available to terrestrial species that make use of terra firme and igapó forests. Nonetheless, these lateral movements of terrestrial mammals between hydrologically distinct forest types remain poorly understood. This study tested the hypothesis that the attributes of the assemblages (abundance, richness, evenness, and functional groups) of the terrestrial mammals in both these forest types of the Cuieiras River basin, which is located in the Central Amazon, are distinct and arise from the ecological heterogeneity induced by seasonal floods. After a sampling effort of 10,743 camera trap days over four campaigns, two for the terra firme (6,013 trap days) and two for the igapó forests (4,730 trap days), a total of 31 mammal species (five were considered eventual) were recorded in both forest types. The species richness was similar in the igapó and terra firme forests, and the species abundance and biomass were greater in the terra firme forest, which were probably due to its higher primary productivity; whereas the evenness was increased in the igapós when compared to the terra firme forest. Although both forest types shared 84% of the species, generally a marked difference was observed in the composition of the terrestrial mammal species. These differences were associated with abundances of some specific functional groups, i.e., frugivores/granivores. Within-group variation was explained by balanced variation in abundance and turnover, which the individuals of a given species at one site were substituted by an equivalent number of individuals of a different species at another site. However, the occupancy was similar between both forest types for some groups such as carnivores. These findings indicate that seasonal flooding is a relevant factor in structuring the composition of terrestrial mammal assemblages between terra firme and floodplain forests, even in nutrient-poor habitats such as igapós. The results also highlight the importance of maintaining the mosaic of natural habitats on the scale of the entire landscape, with major drainage basins representing management units that provide sufficiently large areas to support a range of ecological processes (e.g., nutrient transport, lateral movements and the persistence of apex predators).

Diversification of Amazonian spiny tree rats in genus Makalata (Rodentia, Echimyidae): Cryptic diversity, geographic structure and drivers of speciation.

Amazonian mammal diversity is exceptionally high, yet new taxonomic discoveries continue to be made and many questions remain for understanding its diversification through time and space. Here we investigate the diversification of spiny rats in the genus Makalata, whose species are strongly associated with seasonally flooded forests, watercourses and flooded islands. We use a biogeographical approach based on a mitochondrial cytochrome b gene through divergence time estimation and reconstruction of ancestral areas and events. Our findings indicate an ancient origin of Makalata for the Guiana Shield and Eastern Amazonia as ancestral area. A first cladogenetic event led to a phylogeographic break into two broader clades of Makalata through dispersal, implying a pattern of western/Eastern Amazonian clades coinciding with the Purus Arch (middle Miocene). Most of subclades we infer originated between the late Pliocene to the early Pleistocene, with few recent exceptions in the early Pliocene through dispersal and vicariant events. The hypothesis of rivers as dispersal barriers is not corroborated for Makalata, as expected for mammalian species associated with seasonally flooded environments. We identify two key events for the expansion and diversification of Makalata species: the presence of geologically stable areas in the Guiana and Brazilian shields and the transition from lacustrine conditions in western Amazonia (Acre system) to a river system, with the establishment of the Amazon River transcontinental system and its tributaries. Our results are congruent with older geological scenarios for the Amazon basin formation (Miocene), but we do not discard the influence of recent dynamics on some speciation events and, mainly, on phylogeographic structuring processes.