Browsing by Subject "Extinction"

In the present study, we examined the predictions of an attentional-associative model (Schmajuk, Lam, & Gray Journal of Experimental Psychology: Animal Behavior Processes, 22, 321-349, 1996) regarding the effect of attentional manipulations on both discrete and contextual conditioned inhibitors.

The SLG model assumes that non-reinforced presentations of an inhibitory conditioned stimulus (CS) do not decrease its inhibitory associations. However, the model predicts that extended presentations will decrease attention to the inhibitor, thereby, decreasing both the expression of its inhibitory power in a summation test and the rate of acquisition in a retardation test. The model also predicts that subsequent presentations of the inhibitory CS with a novel CS will increase both its inhibitory power in a summation test and the rate of acquisition in a retardation test. Using a predictive learning design in humans, Experiment 1 examined the predictions involving the summation tests, whereas Experiments 2 and 3 examined the predictions involving the retardation tests. Experimental results were in agreement with the predictions of the model.

The SLG model also predicts that a salient extinction context (CX) becomes inhibitory and prevents extinction of the excitatory CS-unconditioned stimulus (US) association. Although some data seem to contradict that prediction (e.g., Bouton and King, 1983, Bouton and Swartzentruber, 1986, 1989), Larrauri and Schmajuk (2008) indicated that the CX might not appear inhibitory in a summation test because attention to the CX decreases with many but not few extinction trials. In a human predictive learning experiment, we confirmed the model's predictions that the inhibitory power of the extinction CX can be detected after a few extinction trials when attention to the CX is still high, but not after many extinction trials once attention to the CX has decreased (Experiment 4), and even after many extinction trials by presenting novel CSs to increase attention to the unattended CX (Experiment 5). Furthermore, using an eye-tracker, we confirmed the model's explanation of Experiment 4 results by showing decreased overt attention to the CX after many but not after few extinction trials (Experiment 6).

Importantly, the view that the extinction CX becomes inhibitory allows the model to explain spontaneous recovery (because attention to the excitatory CS increases before attention to the inhibitory CX), renewal (because the inhibition provided by the extinction CX disappears), and reinstatement (the inhibitory CX becomes neutral or excitatory), as well as a very large number of other experimental results related to extinction. Based on the prediction of the SLG, model the implications of our results for the treatments of anxiety disorders were discussed.

The Northern Andes stands as a bastion of unique and narrowly distributed global biodiversity. However, it has also experienced rapid transformation of habitats, posing a serious threat to species in the wild by shrinking their ranges. In this dissertation, I aim to deepen our comprehension of how species react to global changes, pinpointing areas where conservation efforts are lacking and highlighting urgent conservation priorities. Moreover, I demonstrate tangible conservation strategies designed to safeguard vulnerable species, while also prioritizing potential exploration regions to confirm the extent of their ranges.In the first chapter, I assess elevational retreats of nearly 200 range-restricted birds from their lower and upper elevational ranges (Medina et al. 2023). Using abundant crowd-sourced data from the Cornell Lab of Ornithology database, eBird, and the Global Biodiversity Information Facility, I examine whether species shifted their elevational ranges over time by comparing observed versus expected occurrences below a low elevational threshold and above a high elevational threshold for two periods: before and after 2005. I also test for deforestation effects at lower elevations within each species’ distribution ranges. Species’ retreats from lower elevations are ubiquitous and involve a 23–40% decline in prevalence at the lowest elevations. Increases at higher elevations are not consistent. The retreats occur across a broad spectrum of species, from predominantly lowland to predominantly highland. Because deforestation show no relationship with species retreats, I contend that a warming climate is the most parsimonious explanation for such shifts. In the second chapter, I identify priority range-restricted bird species and their conservation hotspots in the Northern Andes (Medina et al. 2024). I employ updated maps of Area of Habitat (AOH), following a protocol I contributed along a set of experts from the Cornell Lab, Birdlife International, and American Bird Conservancy (Huang et al. 2021). In this protocol, I was tasked to build R and Python scripts capable to handle crowd-sourced data and batch-generate habitat maps for a thousand birds across the Americas. With the updated maps of species distribution, I estimate protection within each species’ AOH and for the cumulative distribution of birds. For the latter, I also calculate protection across the elevational gradient. I estimate how much additional protection community lands (Indigenous and Afro-Latin American lands) would contribute if they were conservation-focused. AOHs ranged from 8 to 141,000 km2. I identify four conservation priorities based on cumulative species richness. These priorities are high-resolution mapped representations of Endemic Bird Areas for the Tropical Andes that should be considered critically important. Protected areas cover only 31% of the cumulative AOH, but community lands could add 19% more protection. Sixty-two per cent of the 335 species have ranges smaller than their published estimates, yet IUCN designates only 23% of these as Threatened. Top 50 priority species concentrate in areas of low protection near community lands and at middle elevations where, on average, only 34% of the land is protected. I highlight the importance of collaborative efforts among stakeholders: governments should support private and community-based conservation practices to protect the region with the most range-restricted birds worldwide. Private reserves hold promise for the restoration of degraded landscapes and the protection of fragmented animal populations. In the third chapter, I advocate for the creation and implementation of private reserves as concluded in the previous chapter, drawing upon a case study from the Eastern Andes of Colombia to illustrate their potential. This study examines the rehabilitation efforts spanning four decades within Rogitama, aiming to assess their impact on mammal diversity and composition (Medina et al. 2021). Findings reveal the presence of 22 species, predominantly bats and rodents. These results mirror biodiversity levels akin to those observed in less disturbed areas of the Eastern Cordillera, indicating promising advances in ecosystem recovery within the reserve. I posit Rogitama, as a noteworthy case of successful plant rejuvenation, highlighting its significance in the broader context of biological conservation efforts. I firmly advocate for stakeholders to take heed of this case study as a blueprint for development in Northern Andean regions, where I have previously identified critical conservation gaps and priorities. In the last chapter, I identify species and areas that urgently need exploration to increase knowledge on distribution limits (Medina et al. in prep). I consider the AOH where there is less probability of finding a target species given its closeness to non-detection areas. These non-detection areas have checklists where a target species has yet to be reported. The proportion of species absent from an area over the species present will result in relatively uncertain areas. To define potential exploration sites, I mapped these areas along cumulative AOH for 281 species. I found priority exploration areas (high richness and high relative uncertainty) are relatively small compared to non-priority areas. Since 2000, human impact has penetrated 8% of priority areas and allowed 8% of the areas to be studied. Deforestation has progressively reduced, but some countries are still dealing with it. Protection along the priority regions is low. It is essential that governments devote more efforts to exploring biodiversity to better understand patterns in species distribution and thus develop accurate conservation and management plans.

Biodiversity conservation issues are complex and contentious. In this dissertation, I focus on Indian mammal conservation science, management, as well as policy issues that shape these factors. I am particularly interested in, where and which mammals are extinction prone, and what factors promote species persistence in human-dominated landscapes. I examine patterns of extinction, range contraction and current distribution of 25 species of large mammals in India in Chapters 2 and 3. I apply occupancy models to data from a sub-continental scale expert opinion survey. I model species occurrence in relation to ecological and social covariates based on a priori hypotheses about the determinants of mammalian distribution patterns.

I find that all 25 large mammal species are extinction prone. I find time affects extinction, and conservation initiatives of the last four decades have allowed some species to re-colonize some areas. I find protected wildlife reserves are critically important for persistence of species. Many species with much of their habitat outside existing protected areas will require new protected areas to persist. I find that human population density negatively influences survival probability for species, and human cultural tolerance positively affected persistence of species. Most large-bodied animals, habitat specialists, and rare species had higher extinction probabilities. I find that in addition to protected areas, land use, and human population densities, regionally rooted cultural and religious factors have allowed some species to survive. Conservation strategies must integrate all these factors to ensure the survival of India's large mammals in the future.

Conservation efforts to protect wildlife in human-dominated landscapes, often requires relocation of people. This policy has rarely been examined in detail. In Chapter 4, I focus on a reserve in India's Western Ghats of India to assess resettlement experiences of people during and after implementation of a relocation project.

Lastly, the success or failure of conservation policies and management interventions be they for protecting wildlife or addressing needs of local communities, depends substantially on the attitudes of conservation practitioners. In Chapter 5, I examine the attitudes, perspectives and opinions of Indian conservationists towards conservation issues and policies in India.

This dissertation explores the concept of toxicity through the lens of literature. It takes the Plantationocene on the Hispanophone, Francophone, and Creolophone Caribbean experiences as the starting point to understand how the period and location circumstances affect the narratives we create around biological exposure to toxins and ideas of immunity and biological harm. Through the analysis of six contemporary novels, drawing from health humanities, biopolitics, and ecocriticism, it offers an understanding of what toxicity entails in contemporary imaginaries of the Caribbean and what kind of narratives are born from the need to make sense of an existence surrounded by discourse about climate collapse, pandemics, and extinction. The three chapters delve into intoxication in sacred spaces, the visual politics of infection using the zombie trope, and the role of storytelling in the transmission of abstract and material toxicity. They show how authors of this era offer alternative narratives of human existence in our current context that stray away from conservationist and purist ideas of ecology and planetary balance. The study aims to enhance our understanding of the centrality of toxicity in the Plantationocene context as well as the counterplantation practices that arise as alternatives for survival, contributing valuable insights into our post-pandemic world.