Abstract: Climate change has already become one of the main drivers of biodiversity loss, impacting many species’ populations across the globe. In order to survive, species have been reported to change their distributions, phenologies, and morphologies, among other factors. Therefore, identifying which species and populations are undergoing change and how is vital to design proactive and effective conservation strategies. Traits are useful tools to achieve this, as they allow identifying groups of species with similar characteristics. However, not all populations of the same species have been observed to respond similarly to climate change, some of them even showing contrasting responses. Here, we aimed to identify the role of intrinsic traits (e.g., generation length), environmental factors (e.g., temperature range), and latitude in determining responses to climate change at the intraspecific level. Birds and mammals constitute ideal study groups for this, as multiple studies have reported their responses to climate change, their distributions are well known, and they have trait data available. To achieve this, we performed a literature review on distributional (for both taxa) and phenological (only for birds) responses to climate change. We classified these responses based on their outcome and obtained species-level traits and intraspecific-level environmental factors and latitudinal position. We then performed binomial generalized linear mixed models to identify which of these factors were significantly associated with experiencing range expansions compared to expansions and phenological advances compared to delays. We found that latitudinal location played a key role in determining the response, with distributional contractions and phenological advances occurring at the warm edge. Traits such as habitat specialization, litter size, and longevity, as well as environmental factors such as temperature increase, maximum temperature, and temperature and precipitation seasonality, also influenced responses to climate change. Our results highlight the need to account for intraspecific differences when analyzing responses to climate change and reinforce the usefulness of location, environmental factors, and traits to identify populations that are vulnerable to climate change.
