Abiotic niche divergence of hybrid species from their progenitors

Although more frequently discussed recently than previously, the role of ecology in homoploid hybrid and allopolyploid speciation has not been subjected to comparative analysis. We examined abiotic niche divergence of 22 assumed homoploid hybrid species and 60 allopolyploid species from those of their progenitors. Ecological niche modeling (ENM) was employed in an analysis of each species’ fundamental niche, and ordination methods were used in an analysis of realized niches. Both analyses utilized 100, 000 georeferenced records. From estimates of niche overlap and niche breadth, we identified for both types of hybrid species four niche divergence patterns: niche novelty, niche contraction, niche intermediacy and niche expansion. Niche shifts involving niche novelty were common and considered likely to play an important role in the establishment of both types of hybrid species, although more so for homoploid hybrid species than allopolyploid species. Approximately 70% of homoploid hybrid species versus 37% allopolyploid species showed shifts in fundamental niche from their parents, and ~86% versus ~52%, respectively, exhibited shifts in realized niche. Climate was shown to contribute more than soil and landform to niche shifts in both types of hybrid species. Overall, our results highlight the significance of abiotic niche divergence for hybrid speciation, especially without genome duplication.