Thesis

Biogeography of the Dendrobatidae family in Ecuador: Ecological Niche Models, diversity, endemism and threats

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Abstract

Future predictions developed with Climate Change Models describe changes in precipitation patterns, temperature and changes in the intensity and frequency of extreme weather events, generating a geographic shift of the Ecological Niche and causing threats to species diversity. The intent of this work is to identify priority conservation areas, using the interaction of climatic change scenarios, deforested areas and protected areas with Ecological Niche Models of species of the Dendrobatidae family. Poisonous frogs in Ecuador are represented by 46 species, of which 17.4% are Critically Endangered (CR), 15.22% Endangered (EN), and 8,7% Vulnerable (VU). The environmental suitability of the species covers 256,091km2 (90.31%) of the total of the country, and are present in all the ecosystems of Ecuador. The ecoregions of the Eastern Montane Forest, Amazonian Tropical Humid Forest, Choco Tropical Humid Forest and Western Montane Forest present the greatest abundance and diversity. 46 spp. were analyzed and Ecological Niche Models (ENM) of 35 spp. were generated to get to know the current distribution of the area of environmental suitability and to be able to elucidate its adaptability to different scenarios of future climate change by the year 2050. On average, a contraction of (33.81%) and an expansion of (24.67%) was obtained, confirming the loss of the environmental suitability area. At the same time, the interaction of current species with deforested areas (104,560 km2 - 36.87% -) and protected areas (46,138 km2 - 16.27% -) was analyzed, where 96.60% of deforested areas and 96.95% of protected areas coincide with the environmental suitability areas of this family. Considering the results obtained in the models of diversity, future climate change, endemism, density, threatened species, interaction with deforested areas and with the National System of Protected Areas (SNAP, in Spanish), there are areas of high diversity and endangered endemicity. This generates the need for continuous revisions and updates of the SNAP, where new protected areas are created (Amazon eastern center and eastern foothills of the Andes), others, expanded (Yasuni National Park, Limoncocha Biological Reserve, and Cuyabeno Fauna Production Reserve) and biological corridors that guarantee the non-isolation of species are generated.

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This study investigates, on a continent-wide scale, which environmental factors associate with the distributional boundaries of wintering North American avifauna. Distribution and abundance maps of 148 land birds wintering in the contiguous United States and southern Canada are compared with maps of six environmental factors: average minimum January temperature, mean length of frost-free period, potential vegetation, mean annual precipitation, average general humidity, and elevation. The species maps were generated from 10 years of National Audubon Society's Christmas Bird Count data. The comparisons reveal that average minimum January temperature, mean length of frost-free period, and potential vegetation frequently associate with the northern range limits of wintering species (60.2%, 50.4%, 63.7%, respectively). Only two factors, potential vegetation and mean annual precipitation, are coincident with a large proportion of species' eastern range boundaries (62.8% and 39.7%, respectively). The frequency of association between the environmental factors and the western boundaries of the species' ranges is lower than in the other two directions, and more factors exhibit a correspondence. These include potential vegetation (46.0%), mean annual precipitation (36.0%) and elevation (38.0%). Associations with species' southern boundaries are ignored, because 89.2% of the species have range limits abutting the edge of the study area. Only 0.6% of the possible associations between the species' ranges and environmental factors are expected to occur by chance. To enhance the understanding of the correspondence between species' range limits and environmental factors, four mutually exclusive feeding guilds are examined. These include Raptors and Shrikes, Bark Gleaners, Foliage Gleaners, and Seed Eaters. Predictably, both temperature factors, minimum January temperature and mean length of frost-free period, associate with northern range limits of many species in all four guilds (Raptors and Shrikes, 54.5% and 36.4%; Bark Gleaners, 46.1 and 46.1%; Foliage Gleaners, 86.4% and 68.2%; and Seed Eaters, 60.0% and 56.0%, respectively). Isopleths of mean lenght of frost-free period also coincide with the western boundaries of Foilage Gleaners (55.6%). Potential vegetation corresponds with the northern distributional boundaries of a large proportion of species in all four guilds (Raptors and Shrikes, 54.5%; Bark Gleaners, 76.9%; Foliage Gleaners, 68.2%; Seed Eaters, 68.0%), while along the eastern and western boundaries, vegetation is coincident with members of the two guilds most strongly linked with vegetation: Bark Gleaners (East 88.9% and West 66.7%) and Seed Eaters (East 62.5% and West 42.9%). The western range edges of the Bark and Foliage Gleaners associate with elevation (44.4% and 44.4%).
Article
A new species of Colostethus from Colombia is described. This species is related to those Colostethus having males with Finger III expanded. The presence or absence of neopalatines is examined in 25 species of Colostethus, two Dendrobates, three Mannophryne, one Minyobates, and two Nephelobates. The absence of neopalatines is synapomorphic within the Dendrobatidae. The absence of neopalatines suggests that Colostethus (sensu lato) is paraphyletic with respect to the aposematic dendrobatids. /// Se describe una nueva especie de Colostethus de Colombia. Esta especie esta relacionada a aquellos Colostethus cuyos máchos tienen el Dedo III expandido. La presencia o ausencia de neopalatinos se examina en 25 especies de Colostethus, dos Dendrobates, tres Mannophryne, uno Minyobates, y dos Nephelobates. La ausencia de neopalatinos es sinapomórfica dentro de los dendrobatidos. La ausencia de neopalatinos sugiere que Colostethus (sensu lato) es parafilético con respecto a los dendrobatidos aposemáticos.
Article
The herpetofauna of the equatorial dry forest ecoregion of the Peruvian Pacific slope consists of 6 species of amphibians and 33 of reptiles, being of this total 2 amphibian species and 13 reptiles species endemics. The habitat, microhabitat and diel activity of each species is described. The biogeographic distribution pattern of the herpetofauna of this ecoregion and its relation with the pacific desert ecorregión and the montane forests of the occidental slope of the Andes is also described.
Article
Poison frogs in the genus Dendrobates have very small clutch sizes (2–6 eggs among species for which there are data) and typically transport their tadpoles singly to small phytotelmata, such as bromeliad tanks, leaf axils, fallen fruit capsules, and treeholes. Tadpoles of many species are predaceous, consuming larvae of insects that use the same microhabitat for breeding, such as giant damselflies and mosquitoes. Previous studies and observations on the behavior of poison frog tadpoles led us to question whether tadpoles might be cannibalistic. We studied a population of Dendrobates castaneoticus in lowland rainforest in Pará, Brazil; additional data were collected on Dendrobates auratus in Nicaragua. At the study site in Brazil, we established a grid of 40 Brazil nut capsules, the microhabitat used by D. castaneoticus for tadpole deposition. Of 42 tadpoles deposited during the 55 days of the study, 20 were killed or died; 16 of these were presumably killed by conspecific tadpoles. Growth rate and time to metamorphosis was higher among tadpoles that consumed three or more tadpoles or relatively large larvae of the mosquito Trichoprosopon digitatum, a colonist of newly opened Brazil nut capsules. We propose that selection has favored the development of predatory behavior in poison frog tadpoles primarily as a mechanism to eliminate predators from the small phytotelmata in which they develop and that cannibalism is a secondary outcome of this behavior. Predatory behavior also provides tadpoles with a source of food, which is frequently limited in these microhabitats. Additional studies of the biology of tadpoles of other species of Dendrobates are needed to determine the evolution of predatory and cannibalistic behavior in the clade.
Article
Maps of species' distributions or habitat suitability are required for many aspects of environmental research, resource management and conservation planning. These include biodiversity assessment, reserve design, habitat management and restoration, species and habitat conservation plans and predicting the effects of environmental change on species and ecosystems. The proliferation of methods and uncertainty regarding their effectiveness can be daunting to researchers, resource managers and conservation planners alike. Franklin summarises the methods used in species distribution modeling (also called niche modeling) and presents a framework for spatial prediction of species distributions based on the attributes (space, time, scale) of the data and questions being asked. The framework links theoretical ecological models of species distributions to spatial data on species and environment, and statistical models used for spatial prediction. Providing practical guidelines to students, researchers and practitioners in a broad range of environmental sciences including ecology, geography, conservation biology, and natural resources management.
Article
Dendrobatid frogs perform a unique mode of parental care, ranging from egg attendance and tadpole transport to tadpole feeding. It is hypothesized that a behaviour in which the egg attending parent remains with the cluch is the most primitive condition. In more advanced forms or parental care, the male is able to attend several clutches of eggs. Tadpole attendance and feeding, finally, started as deceit; the male induced the female to lay eggs into a bromeliad leaf axil already occupied by a larva. Costs and benefits of the different modes of parental care and possible alternative reproductive tactics are discussed.
Article
MaxEnt is a program for modelling species distributions from presence-only species records. This paper is written for ecologists and describes the MaxEnt model from a statistical perspective, making explicit links between the structure of the model, decisions required in producing a modelled distribution, and knowledge about the species and the data that might affect those decisions. To begin we discuss the characteristics of presence-only data, highlighting implications for modelling distributions. We particularly focus on the problems of sample bias and lack of information on species prevalence. The keystone of the paper is a new statistical explanation of MaxEnt which shows that the model minimizes the relative entropy between two probability densities (one estimated from the presence data and one, from the landscape) defined in covariate space. For many users, this viewpoint is likely to be a more accessible way to understand the model than previous ones that rely on machine learning concepts. We then step through a detailed explanation of MaxEnt describing key components (e.g. covariates and features, and definition of the landscape extent), the mechanics of model fitting (e.g. feature selection, constraints and regularization) and outputs. Using case studies for a Banksia species native to south-west Australia and a riverine fish, we fit models and interpret them, exploring why certain choices affect the result and what this means. The fish example illustrates use of the model with vector data for linear river segments rather than raster (gridded) data. Appropriate treatments for survey bias, unprojected data, locally restricted species, and predicting to environments outside the range of the training data are demonstrated, and new capabilities discussed. Online appendices include additional details of the model and the mathematical links between previous explanations and this one, example code and data, and further information on the case studies.
Article
1. Understanding the factors affecting species occurrence is a pre-eminent focus of applied ecological research. However, direct information about species occurrence is lacking for many species. Instead, researchers sometimes have to rely on so-called presence-only data (i.e. when no direct information about absences is available), which often results from opportunistic, unstructured sampling. maxent is a widely used software program designed to model and map species distribution using presence-only data.
Article
The Genetic Algorithm for Rule-Set Prediction (GARP) is one of several current approaches to modeling species’ distributions using occurrence records and environmental data. Because of stochastic elements in the algorithm and underdetermination of the system (multiple solutions with the same value for the optimization criterion), no unique solution is produced. Furthermore, current implementations of GARP utilize only presence data—rather than both presence and absence, the more general case. Hence, variability among GARP models, which is typical of genetic algorithms, and complications in interpreting results based on asymmetrical (presence-only) input data make model selection critical. Generally, some locality records are randomly selected to build a distributional model, with others set aside to evaluate it. Here, we use intrinsic and extrinsic measures of model performance to determine whether optimal models can be identified based on objective intrinsic criteria, without resorting to an independent test data set. We modeled potential distributions of two rodents (Heteromys anomalus and Microryzomys minutus) and one passerine bird (Carpodacus mexicanus), creating 20 models for each species. For each model, we calculated intrinsic and extrinsic measures of omission and commission error, as well as composite indices of overall error. Although intrinsic and extrinsic composite measures of overall model performance were sometimes loosely related to each other, none was consistently associated with expert-judged model quality. In contrast, intrinsic and extrinsic measures were highly correlated for both omission and commission in the two widespread species (H. anomalus and C. mexicanus). Furthermore, a clear inverse relationship existed between omission and commission there, and the best models were consistently found at low levels of omission and moderate-to-high commission values. In contrast, all models for M. minutus showed low values of both omission and commission. Because models are based only on presence data (and not all areas are adequately sampled), the commission index reflects not only true commission error but also a component that results from undersampled areas that the species actually inhabits. We here propose an operational procedure for determining an optimal region of the omission/commission relationship and thus selecting high-quality GARP models. Our implementation of this technique for H. anomalus gave a much more reasonable estimation of the species’ potential distribution than did the original suite of models. These findings are relevant to evaluation of other distributional-modeling techniques based on presence-only data and should also be considered with other machine-learning applications modified for use with asymmetrical input data.
Article
Living organisms are under selection not only for one, but also for several inheritable characters at the same time. Well-sampled and well-supported phylogenies are necessary for the studies of character evolution and their history. The poison frogs (Dendrobatidae) are a well-known example of aposematism in anurans. They include ~270 species of Neotropical frogs with aposematic (toxic and conspicuous) and non-defended (palatable and cryptic) species. The origin of aposematism in poison frogs is puzzling, because of its predicted low probability of establishment due to the prey's increased conspicuousness. Previous studies suggested a single origin of toxicity and warning coloration. By expanding taxon sampling of the group, I reexamined the phylogenetic correlation between the origins of toxicity and warning coloration. I found four or five independent origins of aposematism; by using simulations, I rejected hypotheses of one, two, or three origins of aposematism (P < 0.002). I also found that diet specialization is linked with the evolution of aposematism and has evolved independently at least two times. Poison frogs are endemic to the Neotropic, which is one of the Earth's largest reservoir of biodiversity. I reconstructed the biogeography of the poison frog clade and rejected an Amazonian center-of-origin in favor of a model expanding over the Neotropics. I inferred 14 dispersals into and 18 out of Amazonia to adjacent regions; the Andes were the major source of dispersals into Amazonia. Significant percentage of dendrobatid diversity in Amazonia and Chocó resulted from repeated immigrations, with radiations at <10.0 million years ago. In contrast, the Andes, Venezuelan Highlands, and Guiana Shield have undergone extended in situ diversification at near constant rate since the Oligocene. Poison frogs have significant variation on their physiological characteristics. I measured resting and active metabolic rates of 54 species. I traced metabolic measurements along aposematism, diet specialization, molecular rates, and body mass. I found a synergistic and co-adapted functionality of active metabolic rates with all previous traits that is perhaps the consequence of the increase in complexity in most biological systems. My thesis has expanded the knowledge of the biology, phylogenetic history, and biogeography of the poison frogs. Biological Sciences, School of
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