TAHUB/II-055 - Especies ganadoras en un mundo en cambio

Human activities are impacting ecosystems globally, to an unprecedented degree and with important effects on global biodiversity. However, human activities do not affect all species in the same way and landscapes transformed by human development may still provide profitable habitats and resources for species with a moderate degree of adaptation to anthropogenic alterations. Population expansions related with human disturbances have recently gained notoriety as a major conservation and management concern in natural and semi-natural ecosystems. However, the mechanisms that facilitate the invasion or proliferation of native species and the ecological consequences of this expansion have been scarcely studied, probably because they are considered natural processes compared to exotic invasions. In fact, expanding populations of native, human-resistant species may represent an important threat to more human-sensitive species that could be superior competitors in natural areas but not always in transformed biota. Also, the expansion of these species could, in some cases, compromise economic activities such as farming and fishing, or human health via dispersion of pathogens. Among natural ecosystems, marine systems are of particular concern, since centuries of human activities have resulted in loss, degradation and transformation of these natural habitats. Consequently, several marine predator species have been undergoing severe population declines over recent decades. The process by which marine predators have been negatively affected by marine ecosystem change, in special overharvesting of marine resources, varies between species but is generally associated with either alteration of available resources and degradation of the suitable habitat. However, alterations of marine ecosystems have affected marine species differentially, in relation to their tolerance to anthropogenic influence. In these ecosystems, those called “winning marine predators” are species efficiently adapted to exploit a diverse suite of natural and human-related resources present in marine, freshwater and terrestrial habitats. Artificial increase in the availability of trophic resources resulting from human activities, such fisheries discards, refuse dumps or introduced prey species, has been suggested as an important factor explaining the substantial increase in population sizes of several seabirds in recent decades. Despite the vast amount of information generated during the last decade, on the population dynamics and main dietary habits of these opportunistic marine predators, aspects directly related to the ecological and behavioural mechanisms explaining the success of these species are still poorly understood. Similarly, the direct consequences of the proliferation of opportunistic species on other predators including humans have been scarcely investigated. Understanding these mechanisms and the potential interactions with other species is important for the appropriate design of management programs. In this project, we aim to investigate the main ecological factors and repercussions related to the success and expansion of the yellow-legged gull (Larus michahellis), species model of an ecological ‘winner’ and successful marine predator adapted to human-transformation. Particularly, we will examine; (i) the degree of individual specialization in foraging habits, (ii) the type of habitat exploited when searching for food; (iii) interactions with other species coexisting in the same area; (iv) the main trophic habits and the relationships between spatial use and (vi) physiological state and (vii) pathogens prevalence. To meet these objectives, we will use a multidisciplinary fieldwork and laboratory approach combining the use of novel, high-resolution GPS-accelerometer devices, intrinsic markers (stable isotopes), ecophysiological parameters (biochemical profiles and oxidative stress) and pathogen screening (salmonella, campylobacter and West Nile virus).