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| Birds vary greatly in their life-history strategies, including their breeding systems, which range from brood parasitism to a system
with multiple nonbreeding helpers at the nest. By far the most common arrangement, however, is where both parents participate
in raising the young. The traits associated with parental care have been suggested to affect dispersal propensity and lineage
diversification, but to date tests of this potential relationship at broad temporal and spatial scales have been limited. Here, using
data from a globally distributed group of corvoid birds in concordance with state-dependent speciation and extinction models,
we suggest that pair breeding is associated with elevated speciation rates. Estimates of transition between breeding systems
imply that cooperative lineages frequently evolve biparental care, whereas pair breeders rarely become cooperative. We further
highlight that these groups have differences in their spatial distributions, with pair breeders overrepresented on islands, and
cooperative breeders mainly found on continents. Finally, we find that speciation rates appear to be significantly higher on islands
compared to continents. These results imply that the transition from cooperative breeding to pair breeding was likely a significant
contributing factor facilitating dispersal across tropical archipelagos, and subsequent world-wide phylogenetic expansion among
the core Corvoidea. | |
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