Phylogeny and biogeography of the hollies (Ilex L., Aquifoliaceae)

The holly genus, Ilex L., in the monogeneric Aquifoliaceae, is the largest
woody dioecious genus (>664 spp.), with a near‐cosmopolitan
distribution in mesic environments. We constructed a phylogeny based on
two nuclear genes, representing 177 species spread across the geographical
range, and dated using macrofossil records. The five main clades had a
common ancestor in the early Eocene, much earlier than previously
suggested. Ilex originated in subtropical Asia and extant clades colonized
South America by 30 Ma, North America by 23 Ma, Australia by 8 Ma, Europe
by 6 Ma, and Africa by 4 Ma. South and North America were colonized
multiple times. Ilex also reached Hawaii (10 Ma) and other oceanic
islands. Macrofossil and pollen records show the genus has tracked mesic
climates through time and space, and had a wider distribution before late
Miocene global cooling. Our phylogeny provides a framework for studies in
comparative ecology and evolution.