The Amazon basin, spanning approximately 540,000 km2, exhibits distinct fluviometric surfaces that differentiate between the dry and rainy seasons. This seasonality, along with hydrological connectivity and the creation of new habitats during the rainy season, significantly promotes the migration, reproduction, and feeding of potamodromous fishes. To estimate the realized niches of species, species distribution models (SDMs) employ the extrapolation of environmental predictors and species occurrence data. Our objective was to compare the spatial distribution of migratory fish species in the Amazon basin using SDMs based on variables characterizing the dry season, rainy season, and a combination of both. All evaluated treatments demonstrated high performance and exhibited different distribution ranges in the applied SDMs, particularly when combining environmental variables with occurrence data during the rainy season. These findings support the hypothesis that spatial distribution is influenced by seasonality. The increased fluviometric surface and enhanced connectivity of the rainy season favor both longitudinal and lateral migrations of Amazonian migratory catfishes. Moreover, the spatial distribution reveals four critical spatial overlap (CSO) regions with higher population densities regardless of the season. These CSOs primarily coincide with the Amazon alluvial plain, which exhibits the highest rates of endemism, species richness, and abundance of organisms. Considering the discontinuous and heterogeneous nature of fluviometry when performing niche modeling processes is pivotal, although SDMs applied in the Amazon generally ignore such regional seasonality.

Introduction: Leptodactylus latinasus and Physalaemus cuqui are sympatric anuran species with similar environmental requirements and contrasting reproductive modes. Climatic configuration determines distribution patterns and promotes sympatry of environmental niches, but specificity/selectivity determines the success of reproductive modes. Species distribution models (SDM) are a valuable tool to predict spatio-temporal distributions based on the extrapolation of environmental predictors. Objectives: To determine the spatio-temporal distribution of environmental niches and assess whether the protected areas of the World Database of Protected Areas (WDPA) allow the conservation of these species in the current scenario and future. Methods: We applied different algorithms to predict the distribution and spatio-temporal overlap of environmental niches of L. latinasus and P. cuqui within South America in the last glacial maximum (LGM), middle-Holocene, current and future scenarios. We assess the conservation status of both species with the WDPA conservation units. Results: All applied algorithms showed high performance for both species (X̅TSS = 0.87, X̅AUC = 0.95). The L. latinasus predictions showed wide environmental niches from LGM to the current scenario (49 % stable niches, 37 % gained niches, and 13 % lost niches), suggesting historical fidelity to stable climatic-environmental regions. In the current-future transition, L. latinasus would increase the number of stable (70 %) and lost (20 %) niches, suggesting fidelity to lowland regions and a possible trend toward microendemism. P. cuqui loses environmental niches from the LGM to the current scenario (25 %) and in the current-future transition (63 %), increasing the environmental sympathy between both species; 31 % spatial overlap in the current scenario and 70 % in the future. Conclusion: Extreme drought events and rainfall variations, derived from climate change, suggest the loss of environmental niches for these species that are not currently threatened but are not adequately protected by conservation units. The loss of environmental niches increases spatial sympatry which represents a new challenge for anurans and the conservation of their populations.

A juvenile king penguin (Aptenodytes patagonicus) was sighted at San Martin Station, Marguerite Bay, west of the Antarctic Peninsula (68(degrees)07'S, 67(degrees)08'W) on 3 February 2020. The animal was apparently healthy. It was uninjured, moving freely between the station buildings. It remained in the area until 27 March, when it was last seen. Numerous king penguin records have been reported in recent years, mostly in the South Shetland Islands. Two chicks have even been recorded hatching on these islands, but there is currently no evidence that king penguins have raised a chick to emancipation successfully. Here we present the most southerly known record of king penguins, the only one farther south than the Antarctic Circle. Coupled with observations from other parts of Antarctica, the information presented here supports previous suggestions by other authors of a southwards expansion of this species specifically in the Antarctic Peninsula region. The presence of this species at numerous Antarctic localities suggests that the known distribution of this penguin could change in the near future in response to climate change.

Fin (Balaenoptera physalus, Linnaeus 1758) and humpback (Megaptera novaeangliae, Borowski 1781) whales feed during the austral summer in Antarctic waters. Despite the spatial (two-dimensional) sympatry of both species, they exhibit trophic segregation (three-dimensional). We used multitemporal presence-only data of fin and humpback whales and Antarctic krill (Euphausia superba, Dana 1852) combined with environmental variables to produce species distribution models (SDMs). We aimed to (1) determine the environmental suitability in the Southern Ocean for fin and humpback whales and krill, with field validation in a region of interest, (2) calculate the areas of spatial overlap between the two whale species and between the whales and krill and (3) quantify the presence of the target species within the protected areas from the world database on protected areas (WDPA). All the SDMs had high performances, with AUC and TSS values higher than 0.8. On a circum-Antarctic scale, fin whales had northern distributions, whilst humpbacks had southern distributions. There was a spatial overlap of 47% between whales and 16% between them and krill. Nearly 92% of fin whale sightings overlapped spatially with their binary predictions, this value was 91% for humpback whales. For fin whales, 2% of their environmental suitability was projected in some WDPA areas, and this value was 4% for humpback whales and 15% for krill. Despite international efforts, the environmental niches of target species are partially protected by the WDPA, mainly where the spatial overlap between species was greatest. The anthropic and climatic pressures that Antarctica is experiencing challenge us to propose new responsible scientific responses to environmental dynamics and biodiversity.

As part of a multi-year study of top predators in Antarctica, we conducted a seabird shipbased survey on board Almirante Irizar icebreaker in the Weddell Sea to the Filchner Ice Shelf in the austral summer 2020. We carried out 10-minute counts along 1843 km during 125 hours of observation. We analyzed the species distributions and the relationships with the ice cover. We registered 15 species of which four represented more than 85% of the total abundance: Antarctic petrel Thalassoica antarctica (43.9%), snow petrel Pagodroma nivea (16.3%), Arctic tern Sterna paradisaea (15.2%) and emperor penguin Aptenodytes forsteri (10.1%). Species distribution and its relationship with ice cover were analyzed statistically. The ice cover concentration was estimated by using satellite images. We compared our results with the first ship-based bird survey conducted up to the Filchner Ice Shelf in the austral summer 1955/56 to analyze possible changes in the bird community over time. Out of 13 recorded species in the 1955/56 cruise, 11 were present in this study with similar abundance proportions. In both cruises, the bird community consisted of a group of non-numerous species associated with icefree waters and another group of very numerous species associated with high concentrations on ice cover. The similarities between the two cruises, spaced 65 years apart, suggest a temporal persistence of the bird community of the central and the southern Weddell Sea that could be explained by the dynamics of the ice cover and the presence of reproductive colonies within the study site. The current environmental warming is alarming in this bird community because more than 85% of all its individuals belong to four species strongly dependent on ice cover.

Crocodile lizards (Shinisaurus crocodilurus) are an endangered, ‘living fossil’ reptile from a monophyletic family and therefore, a high priority for conservation. We constructed climatic models to evaluate the potential impact of climate change on the distribution of crocodile lizards for the period 2000 to 2100 and determined the key environmental factors that affect the dispersal of this endangered species. For the construction of climatic models, we used 985 presence-only data points and 6 predictor variables which showed excellent performance (AUC = 0.974). The three top-ranked factors predicting crocodile lizard distribution were precipitation of the wettest month (bio13, 37.1%), precipitation of the coldest quarter (bio19, 17.9%), and temperature seasonality (bio4, 14.3%). Crocodile lizards were, just as they are now, widely distributed in the north of Guangdong Province in China and Quảng Ninh Province in Vietnam at the last glacial maximum (LGM). Since the LGM, there has been an increase in suitable habitats, particularly in east-central Guangxi Province, China. Under future global warming scenarios, the potential habitat for crocodile lizards is expected to decrease significantly in the next 100 years. Under the most optimistic scenario, only 7.35% to 6.54% of suitable habitat will remain, and under the worst climatic scenario, only 8.34% to 0.86% of suitable habitat will remain. Models for no dispersal and limited dispersal showed that all crocodile lizards would lose habitat as temperatures increase. Our work contributes to an increased understanding of the current and future spatial distribution of the species, supporting practical management and conservation plans.

Abstract The over‐exploitation of land resources poses a serious threat to biodiversity on a global scale. Changes in land‐use and human exploitation have had a major impact on wild populations and their habitat in China. We assessed how habitat quality has changed over time (1995–2020). Specifically, we analyzed how the habitat quality of crocodile lizard has changed over time based on multi‐temporal land‐use data (1995, 2000, 2010, 2015 and 2020) using a land‐use transfer matrix and habitat quality model. The results showed that the main landscape types in the study area were arable land (21.21% of the area) and woodland (69.59% of the area) during the period. Construction land (land used for development) had decreased by 991 km2, a decrease rate of 59.84% from 1995 to 2000, and increased to 2349 km2, an increase rate of 71.69% from 2000 to 2020. The proportion of grasslands and areas with water were negligible and overall, did not vary significantly in size over the study period. The main feature of land use change in the study area was the loss of grasslands and woodlands through development. The habitat quality model indicated that habitat quality was highest and degradation was lowest in Dayao mountain, Guxiu town, Qichong village and Beituo town. Habitat quality improved in Daguishan and Luokeng areas. Habitat quality was good in Daping mountain and Linzhouding, but they were highly fragmented with patches of low‐quality habitat of varying sizes. Habitats were severely degraded in the Dateng Gorge area. The rate of habitat degradation has slowed over time in the study area, but gradually increased in degradation intensity, and low‐quality habitats were widely distributed and overlapped with the crocodile lizards distribution area. We recommend that protected areas for the crocodile lizard be more closely monitored and managed to halt further decline in habitat quality.

Tropical monodominant forests are rare communities with low tree species diversity. Species monodominance is not the product of a single mechanism, but the result of a set of not yet fully understood integrated ecological factors acting together. We compared populations of Brosimum rubescens in monodominant and mixed forests in Southern Amazonia to test whether leaf functional traits are ecological factors related to monodominance. Individuals of B. rubescens in the mixed forest invest in conservative strategies, while those in the monodominant forest invest in acquisitive strategies. Leaf functional traits, such as petiole length and adaxial cuticle thickness, could be associated with the monodominance of B. rubescens. Our study highlights for the first time the power of integrating leaf functional traits as a component of the set of ecological conditions to explain species monodominance. B. rubescens showed different functional strategies to establish and maintain its population in different forests, which makes it a strong competitor for resources, such as water and light, through variation in its leaf functional traits. We also suggest that such high plasticity can be an important condition for the persistence of the species over time.

The phantom vampire, Vampyrum spectrum (Chiroptera: Phyllostomidae), is the largest South American flying mammal classified as threatened by the IUCN. Despite the broad distribution of this species across South America, its low population density and the spatial isolation of its populations may compromise its response to the expected climate change. Using species distribution models, we increased our knowledge of the historical, current, and future spatial distribution patterns of this species. Considering past [last glacial maximum (LGM) and middle Holocene], current, and future climatic scenarios for the South American extent, we used MaxEnt, random forest (RF), and support vector machine methods to model the distribution of V . spectrum over time and identify/quantify climatically stable areas. We observed that our models achieved good performances for all algorithms, especially for RF. The spatial distribution patterns obtained from the models made it possible to identify areas where V . spectrum was more stable over time. From the LGM to the current and future scenarios, the overall balance is the loss of areas in the species distribution range. By using multitemporal analyses, we may be able to identify repeated historical patterns where some conservation areas may be effective in the future if the spatial patterns of distribution are similar to past distributions. Our work contributes to increasing the knowledge of the spatial distribution of the species, providing support for practical management and conservation plans while also showing the importance of predicting historical spatial patterns and considering their spatial trends.

Brosimum rubescens, a tree species with Neotropical distribution, can achieve local monodominance in Southern Amazonian forests. Understanding how and why this species varies across space and time is important because the monodominance of some species alters ecosystem complexity. Here we evaluated the fundamental ecological niche of B. rubescens by species distribution models (SDM), combining predictive environmental variables with occurrence points, and determined the temporal persistence and how the spatial distribution patterns of this species vary with different environmental predictive variables. To generate the SDMs, we incorporated predictive environmental variables as main components of climatic, hydric and edaphic variables. All algorithms showed higher performance in spatial predictions for hydric variables and for the combination of climatic, hydric and edaphic variables. We identified that the potential niches of B. rubescens seem to be defined by climatic fluctuations, with the edaphic conditions not limiting the presence of this species in the evaluated spatial scale. From the last glacial maximum to the present, this species seems to have increased its spatial amplitude; however, from the present to the future, predictions suggest that B. rubescens will experience a considerable loss of its range. Our findings showed independent and combined effects of different environmental variables, allowing us to identify which are limiting or facilitating the spatial distribution of B. rubescens. We corroborate the spatial persistence and geographical fidelity of the species’ distribution patterns over time.

Estimating species' potential distribution is one of the main objectives of macroecology, especially when sampling biases can affect knowledge on how environmental variables affect species distribution. Ecological niche models estimate species' environmental niches from different variables and their occurrences. Using the presence-only data from eight Amazonian fish species, which inhabit rivers and streams, we aimed to (a) explore the effect of different sets variables on the spatial distributions of target species and (b) evaluate the predictive responses of MaxEnt to sets of variables with different degrees of complexity. MaxEnt has high flexibility in relation to the input data and its performance is influenced by a moderate number of adjustable parameters, allowing for high precision results when balancing underestimation and overestimation errors. We used environmental predictors in MaxEnt the principal components of climatic, topographic and edaphic variables as inputs. The combination of topographic and edaphic variables produced more precise and spatially restricted distribution ranges for all species when compared to those generated with climatic variables. All models reached high AUC values, especially for stream species. Modelled range sizes were broader for the river species, suggesting different tolerance thresholds and habitat preferences when compared to stream species. The complexity of the different variables sets did not affect MaxEnt's prediction capacity. However, for stream species, MaxEnt showed a greater predictive power. This work increases the knowledge with regards to the influence of different environmental predictors on the spatial patterns of the distribution of Amazonian fish.

Identifying home ranges—those areas traversed by individuals in their normal foraging, mating, and parenting activities—is an important aspect of cetacean study. Understanding these ranges facilitates identification of resource use and conservation. Fin and humpback whales occur in Antarctica during the austral summer, but information regarding their home ranges is limited. Using opportunistically collected whale sighting data from eight consecutive summer seasons spanning 2010–2017, we approximate the home ranges of humpback and fin whales around Drake Passage (DRA), West of Antarctic Peninsula (WAP), South Shetland Islands (SSI), an area northwest of the Weddell Sea (WED), and around the South Orkney Islands (SOI). Approximate home ranges are identified using Kernel Density Estimation (KDE). Most fin whales occurred north and northwest of the SOI, which suggests that waters near these islands support concentrations of this species. Most humpback whales were observed around the SSI, but unlike fin whales, their distributions were highly variable in other areas. KDE suggests spatial segregation in areas where both species exist such as SOI, SSI, and WPA. Partial redundancy analysis (pRDA) suggests that the distributions of these species are more affected by spatial variables (latitude, longitude) than by local scale variables such as sea surface temperature and depth. This study presents a visual approximation of the home ranges of fin and humpback whales, and identifies variation in the effects of space and environmental variables on the distributions of these whales at different spatial scales. Citation: Orgeira J L, Alvarez F. Approximating home ranges of humpback and fin whales in Drake Passage and Antarctica. Adv Polar Sci, 2020, 31(4): 248-257, doi: 10.13679/j.advps.2020.0014