International Journal of Molecular Ecology and Conservation 2024, Vol.14, No.5, 218-224 http://ecoevopublisher.com/index.php/ijmec 220 extinction risk. Hybridization with non-adapted gene pools and selective pressures from human activities further contribute to the loss of genetic variability (Kotiaho et al., 2005). 3.3 Evolutionary constraints and ecological specialization Species with narrow ecological niches and specialized evolutionary traits are more prone to extinction. These species often have limited geographic ranges and specific habitat requirements, making them vulnerable to environmental changes and habitat loss. For example, tropical insectivorous birds are highly specialized and sensitive to habitat fragmentation and other anthropogenic changes, which threaten their survival. 3.4 Disruptions in reproductive strategies and life history traits Disruptions in reproductive strategies and life history traits can significantly impact population viability. Factors such as reduced recruitment, altered reproductive timing, and changes in life cycle events due to environmental stressors can lead to population declines (Hayes et al., 2010). These disruptions are often exacerbated by climate change, which can affect critical windows in species' life cycles, leading to disproportionate impacts on demographic rates. 3.5 Ecosystem changes and the breakdown of ecological interactions Ecosystem changes, including the breakdown of ecological interactions, are critical ultimate causes of population decline. Alterations in species interactions, such as predator-prey dynamics and competition for resources, can destabilize ecosystems and lead to declines in species populations (Cahill et al., 2013; Sherry, 2021). Climate change and habitat modification further disrupt these interactions, leading to cascading effects on biodiversity and ecosystem function. 4 Case Study: The Decline of Large Carnivores in Fragmented Habitats 4.1 Selection of the case: the impact of habitat fragmentation on big cats Habitat fragmentation is a significant threat to large carnivores, particularly big cats, as it disrupts their natural habitats and leads to population declines. Fragmentation results in isolated habitat patches, which can severely impact species that require large territories for hunting and breeding. For instance, pumas in the Santa Cruz Mountains experience reduced survival rates due to habitat fragmentation, which creates source-sink dynamics detrimental to their population stability (Figure 1) (Nisi et al., 2023). Similarly, the fragmentation of habitats in agricultural landscapes has been shown to decrease species numbers and disrupt ecological interactions (Kruess and Tscharntke, 1994). Figure 1 Maps of (A) puma GPS locations and (B) housing density at 1 km2 resolution across our study area in the Santa Cruz Mountains, California, USA. In (A), colors correspond to unique individuals, though due to the high number of pumas monitored, some colors for different pumas appear similar (Adopted from Nisi et al., 2023) 4.2 Proximate causes: human-wildlife conflict, habitat reduction, and prey depletion The proximate causes of large carnivore decline in fragmented habitats include human-wildlife conflict, habitat reduction, and prey depletion. Human encroachment into carnivore territories often leads to direct conflicts,
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