Environment and geography drive diversification within the Amazon tree, Protium subserratum

The lowland Amazon rainforest houses some of the greatest tree diversity
on earth. While the vast majority of these species are rare, a small
number are common and widespread. Several recent studies have found that
some dominant species are actually composed of multiple independently
evolving lineages. However, the extent to which widespread and common
Amazonian tree species actually include multiple clades, each on their own
unique evolutionary trajectory, is unknown. Here we investigate
the extent to which lineage divergence may be occurring
within Protium subserratum (Burseraceae), a common and widespread
tree species that is monophyletic with populations exhibiting genotypic
and phenotypic differences associated with environment and geography.
Utilizing a combination of phylogenomic and population genomic methods
with sampling from across the range using herbarium specimens, we found
that P. subserratum contains at least eight distinct
clades defined by geography and environment. Specialization onto
white-sand soils has evolved independently at least two times within the
species; however, phenotype is not correlated with soil type. Finally,
cryptic diversity at the base of the Andes is associated with elevational
shifts. Together these results lend support to the hypothesis that common
and widespread Amazonian species may contain multiple, independently
evolving lineages.