4.4 | Hybrid speciation
Hybridization was increasingly recognized as an important component of
species evolution (Mallet, 2005; Mallet et al., 2016; Stukenbrock,
2016). New species were produced by different ways of evolution, such as
polyploidization, homoploid hybridization, and introgressive
hybridization (Rieseberg & Carney, 1998; Wang, 2017). Due to the
abundant genetic and phenotypic variation in the hybrid progeny
population, the boundaries between them and their parents became blurred
and difficult to distinguish (Abbott, 2003). Therefore, in the past,
botanists only defined a new species according to morphological
characteristics, which was easy to lead to the wrong understanding of
species. In other words, some previously published species were likely
to be hybrid or intermediate state of hybrid transition to new species.
For example, in the Triticeae, Zeng (2011) through cytology and DNA
sequence analysis showed that Kengyilia stenachyra is a natural
hybrid of K. rigidula and Elymus nutans , rather than a
real species. Hybrid progeny population was highly variable, which
retained the important transition types in the evolution process, and
was an indispensable part of the material system to explore the
formation mechanism of hybrid speciation (Rieseberg, 1997). So, the
natural hybrids found in this study provided a good research material
for exploring the formation. Further research will be needed on the
formation of hybrid species.