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.