Beautiful Sunbird (Cinnyris pulchellus). Photo: Wenfei Tong

Research Group Evolution of sensory systems

Sensory systems evolve, allowing organisms to detect the environmental cues necessary for their survival.  Different species live in different habitats and eat different foods, and chemosensory receptors, such as taste receptors, pheromone receptors, and olfactory receptors, often vary in number or function across species. This variation can reflect species-specific ecologies and is also shaped by different evolutionary histories.

In birds, the canonical sweet receptor used by mammals has been lost, and in hummingbirds, carbohydrate detection occurs via a re-purposed savory (umami) receptor. How other nectar- and fruit-eating birds detect sugars remains unknown. In our group we examine the mechanisms by which these other birds detect carbohydrates, to investigate the causes and consequences of sensory shifts and the degree of convergent evolution. We use an integrative approach, combining molecular and cell-culture techniques with behavioral studies. In addition, we will develop new tools to probe the function and evolution of the taste system in birds, and in vertebrates more broadly, to examine the effects of diet shifts on organismal ecology and physiology.

Video: Maude Baldwin and François Peaudecerf

High-speed video (slowed for viewing) of a ruby-throated hummingbird (Archilochus colubris) rejecting water presented in the top feeder after three tongue licks (162 milliseconds). Sucrose (500 mM,
bottom feeder) elicits a prolonged feeding bout.

High-speed video (slowed for viewing) of a ruby-throated hummingbird (Archilochus colubris) rejecting water presented in the top feeder after three tongue licks (162 milliseconds). Sucrose (500 mM,
bottom feeder) elicits a prolonged feeding bout.

Ongoing projects

Evolution of sweet perception in nectar-feeding and fruit-eating birds

Hummingbirds have re-evolved a new sweet receptor, but how other groups of birds detect sugars is unknown.

Together with Dr. Alejandro Rico Guevara and Dr. William Buttemer, we are investigating sweet perception in Australian nectarfeeders. At the Max Planck for Ornithology, we will house diverse fruit- and nectar-feeding species across the bird phylogeny to investigate convergence in sweet detection using behavioral, molecular, and morphological approaches (Photo:Wenfei Tong).

Umami perception in birds and the consequences of sensory shifts

How do sensory systems evolve, and what are the repercussions? Hummingbirds detect sweet with the amino acid receptor—how does this impact their perception of proteins?

Together with researchers at the University of Tokyo, UCLA, and the University of Queensland, we are characterizing amino acid detection in hummingbirds and chickens and are looking at the behavioral effects of the altered receptor, laying the groundwork for an examination of the consequences of sensory shifts in the central nervous system (Photo: Maude Baldwin).

Transgenic models of the avian taste system

Together with collaborations at the MPIO we are working on developing genetic tools to investigate the avian taste system. Labeling cells expressing sweet and umami taste receptors (T1Rs) will enable access to taste buds and the nerves that enervate them.

Detecting coevolution

Taste perception is closely linked with many other aspects of organismal physiology. When diets change, what other systems are affected, and what changes first? Using ancestral sequence reconstruction and coevolution analyses we seek to understand the order of key changes that occur during sensory shifts. Correlations with data from the fossil record will allow us to begin to understand the ancestral environment and the conditions under which sensory systems evolved.

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