Format: ORAL

Sofa Ruiz Cano1, Luis G. Quintanilla2, Nagore G. Medina3

1 Universidad Autónoma de Madrid, Madrid, Spain 2 Universidad Rey Juan Carlos, Madrid, Spain 3 Universidad Autónoma de Madrid, Madrid, Spain

Studying the thermal niche of organisms is crucial in the current context of climate change. However, it is a complex task as physiological requirements, species distributions and the modulating factors such as competition need to be analysed simultaneously. We present a study that combines germination experiments along an environmental gradient both with and without interspecific competition, with thermal niche analyses based on estimated climatic data from global distributions. We evaluated the thermal niches by setting up experiments on germination and growth of two fern species: Culcita macrocarpa and Woodwardia radicans. Both species, which are potential competitors, are tropical relics that share distribution, habitat and exhibit synchronous spore dispersal. Spore germination was compared at eight temperatures ranging from 5 to 35 C and gametophyte growth at 10, 20 and 30C. Our findings demonstrated that spores of W. radicans germinated faster and to a higher percentage, and their gametophytes grew faster than those of C. macrocarpa, especially at moderate to high temperatures. Additionally, interspecific competition reduced germination only in C. macrocarpa. Besides, our results reveal an exceptionally high correlation between climatic parameters and germination parameters in both species. In the case of C. macrocarpa, this correlation increased when examining germination under competition. These findings show the advantages of ferns for culture experiments, and their potential usefulness for tackling many research questions, such as community-level experiments on coexistence, dispersal, effects of community structure on ecosystem functioning or ex situ conservation. These results also hold particular relevance for studying the impacts of climate change even in early life stages, shedding light on how competitive interactions among species can shape their thermal responses and ultimately influence their adaptation.