Multiple Trans‐Marine Dispersals and Niche Conservatism Underlie the Pantropical Distribution of Eugeniinae (Myrtaceae)
Paulo Henrique Gaem, James D. Boyko, Fiorella Fernanda Mazine, Karinne Sampaio Valdemarin, Stephen A. Smith, Thais VasconcelosABSTRACT
Aim
The factors underlying large disjunct distributions among closely related species have long been debated by biogeographers. In general, lineages crossing several trans‐marine barriers should be able to establish more easily where conditions are similar to their ancestral environments, while adaptation to diverse environmental conditions would be more frequent where dispersal is less limited by geographical barriers, such as within landmasses. Here, we test this assumption by contrasting biogeographical history and environmental niche evolution in the large tree clade Eugeniinae (Myrtaceae).
Location
Pantropical.
Taxon
Subtribe Eugeniinae, including the genera Eugenia and Myrcianthes (Myrtaceae).
Methods
We employed the largest available phylogeny of subtribe Eugeniinae to date in a comparative framework for biogeographical models to assess the likelihood of different dispersal routes. We then integrated soil and climatic data to estimate species' environmental niches and used trait evolution models to obtain rates of niche evolution across different regimes and within Eugeniinae clades. Finally, we compared the number of dispersals with rates of niche evolution within each clade.
Results
Eugeniinae originated in South America and achieved a pantropical distribution through a series of predominantly easterly trans‐marine dispersals in the last 25 million years. In general, colonisations of new areas were decoupled from accelerated changes in environmental preferences. Old World Eugeniinae exhibited the highest rates of colonisation of new landmasses and more conserved environmental niches than many exclusively New World clades of the subtribe. High rates of niche evolution in Neotropical Eugeniinae seem to be associated with diversification along elevational gradients and into soils of diverse properties. Finally, the persistence of Eugeniinae within the tropical zone during its geographic expansion may reflect slow evolution of temperature tolerance across all clades.
Main Conclusion
Our findings show that a complex interaction between geographical movement and niche evolution explains the modern distribution of Eugeniinae. Different factors are likely responsible for each trans‐marine long‐distance dispersal event, and further comparative studies across diverse pantropical clades will be useful for determining whether general patterns exist that explain why certain lineages are particularly successful at dispersing across long distances globally.