Rapid anthropogenic environmental changes are impacting global ecological systems, affecting all levels of biological organisation, from molecules to ecosystems. A main line of my research is focused on understanding the eco-evolutionary pathways by which species respond and adjust to rapid environmental change in distributional boundaries and in highly anthropized systems. A critical question is whether ecological and evolutionary responses are being fast and strong enough to keep track of ongoing environmental changes.
Climate change:
Climate change is a main driver of global change and is exerting ever increasing pressure on species already living in harsh environments subject to strong climate variability. My research on the topic has especially focused on populations of salmonids, which are thermally sensitive fish species, living on the trailing edge of their ranges. Both stream-dwelling brown trout and migratory Atlantic salmon have experienced marked population declines over the last decades in the Iberian pensinsula. Through statistical modelling we have tried to answer two questions: (1) are climate-driven environmental changes in breeding and feeding habitats linked to reductions in trout (Almodóvar et al. 2012, Ayllón et al. 2013) and salmon abundance (Nicola et al. 2018, Almodóvar et al. 2019)? (2) Are other anthropogenic drivers and stressors, such as land-use change, flow regulation, damming, water pollution, invasive species, and harvesting interacting with climatic changes (Ayllón et al. 2013)?
There is also worldwide evidence that fish populations are undegoing phenotypic changes in phenological, morphological, physiological, behavioural and life-history traits through plastic and/or evolutionary pathways to mitigate fitness losses induced by climate change. So the necessary question here is: what is the maximum rate of environmental change that populations can cope with? I have used eco-genetic individual-based modelling to address the extent to which density-dependent, plastic and evolutionary changes in phenology and life-history traits can buffer demographic impacts of climate change on trout populations and thus prevent local extinctions in Mediterranean rivers (e.g., Ayllón et al. 2016, 2019a).
Harvest:
Contemporary evolution is driven not only climate change but by several anthropogenic pressures that often operate on the same traits and thus impose new adaptive challenges to populations. Intensive and size-selective harvest produces strong demographic impacts and exerts a strong directional selection force on fitness-related traits in exploited populations. Indeed, the rate of trait changes induced by harvest are typically several times greater than those from natural and other anthropogenic disturbances. My research effort on this topic has centred on assessing the numerical and structural population impacts, as well as the interrelated phenotypic changes in body size and reproductive traits at the individual level, induced by size-selective recreational fishing across alternative regulatory landscapes (Ayllón et al. 2018, 2019b). I have also analyzed which harvest regulations will most likely lead to overexploitation of populations under the new environmental conditions set by climate change (Ayllón et al. 2021).
Daniel Ayllón 