Global biogeographic synthesis and priority conservation regions of the relict tree family Juglandaceae

Abstract Aim: To establish a complete database of Juglandaceae at a
spatiotemporal scale and develop a phylogeographic framework with which to
elucidate the distributional patterns, diversity patterns, origins,
evolution, and conservation priority regions of this family. Location:
Worldwide Methods: Data on the distribution of all the extant and fossil
species of Juglandaceae were collected, followed by analyses of its
latitudinal distribution, elevational distribution, and species and
generic diversity. Furthermore, based on all genera and 87% of the
species, we reconstructed phylogenetic relationships, estimated divergence
times, calculated phylogenetic diversity and inferred ancestral
distributions. Results: Extant Juglandaceae (10 genera and 60 species) are
mainly distributed in eastern Asia and North America (principally between
20°N and 40°N). Tropical Juglandaceae mainly inhabit mountainous areas
higher than 1000 m, especially in the New World. Southwest China and
northern Vietnam are characterized by high species, generic, and
phylogenetic diversity. The United States of America has only high species
diversity. The area of origin of Juglandaceae was North America and Europe
in the early Eocene, and its widespread dispersal mainly occurred between
13 and 26 Ma. Main conclusions: The members of Juglandaceae inhabit areas
with temperate climatic conditions. The diversification centre has shifted
intercontinentally from North America and Europe to Southwest China and
northern Vietnam, which are identified as conservation priority regions.
The high-latitude cooling during the Oligocene followed by a long-term
stable warmer climate in the early and middle Miocene drove the southward
translocation of the family.