Karen Marchetti
e-mail: kmarchetti@ucsd.edu |
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The objective of our current
research is to investigate the mechanistic bases of signals and perceptual
systems used by animals in communication. To understand the evolution
of species differences in the colors used in visual signaling we are focusing
on three questions: (1) Do different species vary in the sensitivity
of their visual systems to different colors, and do visual systems vary
adaptively across species in much the way color does? (2) How does
variation in the background habitat (e.g. color and structure of vegetation
and other objects that form the backgrounds to visual display; color of
ambient light ) influence the evolution of colors and color patterns?
(3) In what ways do individuals increase their conspicuousness behaviorally
(e.g. through the use of display movements that enhance conspicuousness;
through choice of particular lighting conditions used in display), and
how do such behaviors influence the evolution of coloration? (4)
How do multi-modal signals (e.g. song, color, display movements) interact
to produce an overall communication signal, and do different aspects
of the signal function in different social contexts?
To address these questions, we are integrating
studies of genetic and functional characterization of the genes that code
for visual pigments (opsin genes) with studies of the visual behavior
and ecology of natural populations. Our work focuses primarily on
two genera of passerine birds, the Old World warblers (genus Phylloscopus)
and the New World warblers (genus Dendroica). The groups provide
good systems with which to examine the adaptive evolution of visual systems
and the genetic mechanisms underlying species differences in visual signals,
such as color patterns, and perception of those signals. We have chosen
these groups because, despite their ecological similarity, they differ
markedly in the amount of coloration exhibited among species within each
genus. The different Phylloscopus species scarcely vary in color, whereas
Dendroica species exhibit enormous variation in plumage coloration.
Both groups use their color patterns in visual communication. The
Phylloscopus and Dendroica groups are therefore natural complements to
each other, and are useful for examining how variation in opsin genes
underlies species differences in color patterns, color vision, and visually
oriented behaviors. The long-term goal of our research is to integrate
genetic, behavioral, ecological and physiological data as a way to examine
how properties of signaling behavior, signal reception and the physical
environment interact to drive species divergence in signaling characters,
specifically animal color patterns and animal color vision.
Sunbird:
Display behaviors of different Phylloscopus species.
Marchetti, K. (1992). Costs to host defence and the persistence of parasitic cuckoos. Proc. R. Soc. Lond. B. 248, 41-45.
Marchetti, K. (1993). Dark habitats and bright birds illustrate the role of the environment in species divergence. Nature 362, 149-152.
Marchetti, K. (1998). The evolution of multiple male traits in the Yellow-browed leaf warbler. Animal Behaviour 55, 361-376.
Marchetti, K. (2000). Egg rejection in a passerine bird: size does matter. Animal Behaviour 59, 877-883.
Gibbs, H.L., Sorenson, M.D., Marchetti, K.,
Brooke, M de L., Davies, N.B. and Nakamura, H. (2000). Genetic evidence
for female host-specific races of the common cuckoo. Nature 407,
183-186.
Karen Marchetti received her Ph.D. from UC Davis and performed postdoctoral work at McMaster University.
