INTEGUMENTARY PROJECT

The INTEGUMENTARY project, or "Integration of the environment and genomics to understand the mechanism ensemble underpinning transcontinental avian reds and yellows" will delve deeper into the mechanisms that explain continent-wide variation in carotenoid-based colours in tinkerbirds.

Nowadays, the genetic basis of much of phenotypic variation seen in the natural world can be investigated using genomic methods. In birds, recent studies have identified regions of the genome that underpin plumage color and pattern. However, much plumage coloration can vary vastly across landscapes, and it remains unclear to which extent, in addition to genetics, variation in, notably, carotenoid-based colour variation is governed by an interplay between the organism and its environment.

Our understanding of the distributions of carotenoid pigments in integuments has grown substantially over recent decades. Yet, our understanding of how the process from dietary carotenoid uptake to integumentary pigment contributes to colour diversity from within-individual to continental interspecific scales is limited. Carotenoid colors (reds, oranges, yellows) differentiate species from each other, and due to their partial condition- and environment-dependence can represent signals of individual quality. However, the extent to which the distribution of carotenoids in natural environments and the effects of disturbance and climate affect the production of these colors on different parts of an organism is little known. The environment interacts with internal processes of an organism, including hormones, gene expression, and epigenetics, but to our knowledge, no study has examined how this combination of interactions affects carotenoid pigmentation. There has also been a burgeoning interest in combinatorial evolution, whereby combinations of genes may interact to produce combinations of phenotypic characters. Here we will harness the opportunity that hybrid zones provide to detect how combinations of genes and the environment interact with further internal processes to affect integument pigmentation. Our study will thus determine the extent to which combinations of genes, organismal processes and the environment interact to explain continent-wide variation in carotenoid colour.

Figure 1. Carotenoid-based colours vary along environmental gradients. The study will focus on variation in six feather patches (a), the crown, throat, breast, eyebrow, wingbar and dorsal streaks. These feather patches vary between yellow-fronted and red-fronted tinkerbirds and introgress in different combinations in hybrids. They also vary in (a) hue, (b) chroma and (c) brightness along environmental gradients of (d) elevation, (e) temperature and (f) rainfall.