Many flowering plants are allopolyploids, meaning they arose from hybridization between different species, followed by genome doubling. Over time, gene trees for such lineages can become a hopeless tangle.
The literature concerning the travels of Alexander von Humboldt (1769-1859) and Aimé Bonpland (1773-1858) is enormous. Despite this extensive scholarship, we do not know the current whereabouts of roughly half their botanical specimens, which also means we do not know precise collection sites.
The reconstruction of ancient environments depends on proxies from earth and climate science combined with animal and plant fossils. No single proxy will tell the whole story. Or so you’d think.