|Aim Islands and archipelagos have played an important role in the development
of ecological and evolutionary theories. Using a newly compiled molecular
phylogeny we infer the biogeographical history of a monarch flycatcher
genus, Myiagra, which is distributed across the Indo-Pacific. We subsequently
integrate biogeographical and ecomorphological data to examine the role of
dispersal and trait evolution in the build-up of avian assemblages.
Location Australia, the Moluccas, New Guinea and Pacific islands.
Methods We generated a taxonomically densely sampled mitochondrial DNA
dataset that included almost all species and subspecies of the reciprocally
monophyletic genera Myiagra and Arses. We then used maximum likelihoood
and Bayesian inference to infer their phylogenetic relationships. To reconstruct
their biogeographical history, we first dated the tree topology and then used
Lagrange to infer ancestral geographical areas. Finally, we combined ancestral
area reconstructions with information on ecomorphological traits to infer
mechanisms underlying community assembly.
Results We provide the first comprehensive molecular phylogenetic reconstruction
for Myiagra and Arses monarch flycatchers. Our phylogenetic reconstruction
reveals a relatively recent diversification from the Miocene associated with several
major dispersal events. Ancestral area reconstruction reveals several independent
colonizations of the Moluccas, Melanesia, Fiji and the Micronesian islands. Ancestral
state reconstruction of ecological traits suggests that the diversity of traits in
co-occurring species of monarch flycatchers results from independent colonization
events and ecological niche conservatism rather than in situ diversification.
Main conclusions Three waves of colonization, non-overlapping in time, led
to independent speciation events in the Bismarcks, Fiji and the Moluccas, in
addition to in situ speciation events on remote islands of Micronesia, the Solomons,
Vanuatu and Samoa. Few of these colonizations have led to the co-occurrence
of congenerics or species with similar ecomorphological profiles on the
same island. Thus, we suggest that priority effects might prevent new colonizers
from establishing themselves if they share high levels of ecological similarity with
resident species. We conclude that historical dispersal to and colonization of new
islands, combined with ecologically deterministic priority effects, drove the
assembly of insular monarch flycatcher communities across the Indo-Pacific.|