Localized environmental heterogeneity drives the population differentiation of two endangered and endemic Opisthopappus Shih species

Background: Climate heterogeneity not only indirectly shapes the genetic
structures of plant populations, but also drives adaptive divergence by
impacting demographic dynamics. The variable localized climates and
topographic complexity of the Taihang Mountains make them a major natural
boundary in Northern China that influences the divergence of organisms
distributed across this region. Opisthopappus is an endemic genus of the
Taihang Mountains that includes only two spatially partitioned species
Opisthopappus longilobus and Opisthopappus taihangensis. For this study,
the mechanisms behind the genetic variations in Opisthopappus populations
were investigated. Results: Using SNP and InDel data coupled with
geographic and climatic information, significant genetic differentiation
was found to exist either between Opisthopappus populations or two
species. All studied populations were divided into two genetic groups with
the differentiation of haplotypes between the groups. At approximately
17.44 Ma of the early Miocene, O. taihangensis differentiated from O.
longilobus under differing precipitation regimes due to the
intensification of the Asian monsoon. Subsequently, intraspecific
divergence might be induced by the dramatic climatic transformation from
the mid- to late Miocene. During the Pleistocene period, the rapid uplift
of the Taihang Mountains coupled with violent climatic oscillations would
further promote the diversity of the two species. Following the
development of the Taihang Mountains, its complex topography created
geographical and ecological heterogeneity, which could lead to
spatiotemporal isolation between the Opisthopappus populations. Thus the
adaptive divergence might occur within these intraspecific populations in
the localized heterogeneous environment of the Taihang Mountains.
Conclusions: The localized environmental events through the integration of
small-scale spatial effects impacted the demographic history and
differentiation mechanism of Opisthopappus species in the Taihang
Mountains. The results provide useful information for us to understand the
ecology and evolution of organisms in the mountainous environment from
population and species perspective.