Suturing fragmented landscapes: Mosaic hybrid zones in plants may facilitate landscape restoration

Many widespread plant taxa of western North America have diversified into
phenotypically and genetically divergent lineages due to complex
biogeographic histories across heterogeneous landscapes. Mosaic hybrid
zones can form when geographically co-occurring yet environmentally
distinct lineages cross-pollinate and form hybrids that occupy unique
environmental niches absent of a geographic cline. This expands the total
environmental space across which parental and hybrid individuals grow,
resulting in larger, less fragmented geographic distributions. Here, we
highlight hybridization mosaics across three study systems containing taxa
critical to widespread plant communities in western North America:
Ericameria nauseosa, Artemisia tridentata, and Sphaeralcea fendleri. The
systems contain diverged taxa that co-occur geographically across the
landscape, though not environmentally, and hybridize readily.
Hybridization among taxa has facilitated niche expansion into intermediate
environments consistent with unique combinations of adaptive genetic
variation, creating more continuity within each study system (study
systems occupy ~820–270,000 km2 more geographic space by virtue of
hybridization). Furthermore, hybrids are predicted to play important roles
in future climates (they occupy 8–475% more geographic area compared to
present in a high emission climate scenario). This convergent pattern
signals mosaic hybridization as an underappreciated mechanism with broad
ecological and evolutionary ramifications and suggests understanding the
consequences of this process may be critical to predict responses of taxa
to changing climates. Moreover, leveraging mosaic hybridization may assist
the creation of restoration management plans that aim to mitigate the
deleterious effects of habitat fragmentation on ecosystems in the context
of climate change.