The match between plant and pollinator morphologies has fascinated naturalists for centuries and led to the proposition that these mutualistic partners influence each other’s evolution in a process called coevolution. Plant-hummingbird interactions are touted as a classic example of such coevolutionary dynamics in which plants rely on hummingbirds to complete their reproductive cycle and hummingbirds rely on nectar to fuel their fast-paced lifestyle. As a result, plants produce brightly colored flowers, with long corollas and narrow openings that are thought to have evolved specially to attract hummingbirds and prevent access from other pollinators. Likewise, hummingbirds have a variety of bill shapes and lengths that are believed to have evolved to perfectly fit the flowers. Yet, tests for plant-hummingbird coevolution are relatively rare, focused on a few groups, and have yielded mixed results. With a diverse group of researchers skilled in plant and hummingbird ecology and phylogenetic methods, I’m reviewing current evidence and testing for plant-hummingbird coevolution.
Angiosperm phylogeny showing the proportion of hummingbird-pollinated species within each family
Different perspectives on species endemism
No species is distributed everywhere on Earth. Such geographic restriction, broadly termed endemism, is one of the most conspicuous diversity patterns and is at the heart of biogeography. Scientists from different fields of science study endemism, resulting in the emergence of multiple research traditions, terminologies, and analytical approaches. Originally, the term endemism was borrowed from the medical sciences to refer to organisms that occur only within a geographical region, regardless of range size. Historical biogeography used this definition to identify the areas of congruence in species distribution to infer historical processes, such as dispersal and vicariance events associated with a geographic barrier (e.g., river). An alternative perspective on endemism emerged as conservationists and ecologists began to search for regions with greater endemism (i.e., centers of endemism) and their environmental correlates. To operationalize this approach, range size thresholds or weighting schemes were used, and endemism began to refer to an organism whose range size is small. Both definitions are valid but may serve different purposes and that should be made clear in the studies. I’m reviewing the extensive literature on endemism, highlighting definitions, and providing a road map of the main methods and findings. Ultimately, I aim to facilitate communication between biogeographers and to assist young scientists to navigate the vast and rich literature, inspiring them to engage in a more integrative biogeography.
Both species can be considered endemic depending on the definition. Species a is endemic to Brazil, whereas species b is not endemic to a single country, but is range-restricted.
