Abstract
The South American temperate forests have been subjected to drastic past
topographic and climatic changes during the Pliocene – Pleistocene
linked to Andean orogeny and glacial cycles. These changes are common
drivers of genetic structure and adaptation process. Embothrium
coccineum, a member of the Proteaceae family and an emblematic tree of
the South American temperate forest with a distribution spanning 20° of
latitude, has been strongly affected by these topographic and climatic
changes. Previous studies have shown that the species presents a marked
genetic structure with distinct ecotypes described; yet, little is known
about their adaptive genetic responses. The main goal of this study was
to investigate the effects of historical and contemporary landscape
features affecting the genetic diversity and connectivity of E.
coccineum throughout its natural distribution. Using more than 2000
SNPs, two genetic groups (North and Center-South) that have diverged
some 2.8 million years ago were observed. The level of genetic structure
was higher between populations within the North genetic group than
within the Center-South group. We propose that these contrasting
patterns of genetic structure are related to differences in pollinator’s
assemblage and evolutionary histories between genetic groups. Moreover,
we observed the existence a strong patter of isolation by environment in
E. coccineum, suggesting that selection could have leaded to
adaptive divergence among localities. We propose that, within the
Chilean temperate forest, the patterns of genetic variation in E.
coccineum reflect both a Quaternary phylogenetic imprint and the impact
of selection to the strong environmental gradient.