Fitness and Niche Differentiation in Allopolyploid Ferns: Insights from Polystichum aculeatum and its Diploid Progenitors

Allopolyploidy, a process involving hybridization between different species and subsequent duplication of the entire genome, plays a crucial role in plant evolution, especially in ferns. Despite the widespread presence of allopolyploidy in plants, its effects on species’ responses to environmental factors are not well understood. This project investigates how allopolyploidy influences ecological niche segregation and fitness differences by comparing allopolyploid ferns with their diploid progenitors. To encompass a broad spectrum of environmental strategies, we selected two independent complexes representing contrasting habitat types: the Polystichum aculeatum complex, typical of humid montane forests and mountain summits, and three Aleuritopteris (= Oeosporangium) complexes.

The study analyzes how niche segregation and fitness differences between an allopolyploid and its diploid progenitors explain its success in nature. To this end, we compare their ecological niches and evaluate factors such as reproductive isolation, competitiveness, and environmental tolerance. Through fieldwork, niche modeling, and experiments on environmental gradients, we seek the advantages that allow allopolyploids to persist and coexist with their progenitors. The results will provide insights into hybrid speciation, polyploidy, and niche evolution, as well as implications for conservation, given that allopolyploids can perform specific ecological roles and exhibit greater adaptability.