Kate Marshall
Tel: +44 (0)
1223 334 430
Fax: +44 (0) 1223 336 676
Email: km547 at cam.ac.uk
Position held:
BBSRC-funded PhD student, supervised by Martin
Stevens
Previous experience/qualifications:
May 2010-Sept 2011: BBSRC funded research assistant with Martin
Stevens
Oct 2008-May 2010: London media agency, ZenithOptimedia
2007-2008: MSc Animal Behaviour, University of Exeter
2004-2007: BSc Psychology and Zoology, University of Bristol
|
|
Even to the human eye, animal coloration is one of the most striking
examples of evolution by natural and sexual selection, facilitating
thermoregulation, predator avoidance and sexual communication,
and varying considerably across the animal kingdom. Colour can
vary between populations of even the same species, posing fascinating
evolutionary questions which will be the focus of my PhD research.
I aim to address two key questions:
1. How do colour patterns help animals remain hidden from
predators, while at the same time provide mates and rivals with
conspicuous, detectable sexual signals?
One clue lies in how colour patterns exploit the visual capabilities
of different ‘receivers’: that is, predators and conspecifics
(mates and rivals). For instance, some predators may not be able
to detect ultraviolet-reflecting patterns that are actually highly
conspicuous to conspecifics. Therefore, by modelling colour patterns
through the eyes of receivers, I aim to objectively understand
why certain colour patterns evolve and how they optimize both
survival and reproduction.
As well as receiver vision, the local environment can also tell
us a lot about the visual systems and signals of its ancestral
inhabitants, which leads on to my second research question:
2. How do different environments drive the evolution of
different colour patterns and visual systems (sensory drive)?
Specifically, as predicted by so-called ‘sensory drive’,
I will look at whether signalling systems adapt to local environments,
resulting in signal divergence in differing environments. This
has the potential to give us remarkable insights into how signalling
systems diverge due to environmental processes, uncovering the
process of speciation and ultimately exposing natural selection
‘at work’ in nature.
Study System:
The Erhard’s wall lizard Podarcis erhardii
(pictured below) exhibits varying coloration between different
populations, commonly occurring across a range of Greek islands
in the Aegean Sea. The islands exhibit environmental divergence,
varying in background colour (i.e. different types of rock and
sand) and habitat/vegetation structure. This presents an ideal
study system for answering my research questions.
A male Erhard’s wall lizard, Podarcis erhardii, pictured
on the Island of Delos, Cyclades Islands, Greece (June 2011).
Source: Kate Marshall.
Methods:
I will be using a combination of field experiments, digital photography,
and visual modelling, taking inspiration from a recent advent
of innovative techniques which work to understand coloration through
receivers’ eyes. I plan to analyse how P.erhardii colour
patterns are perceived by potential predators, such as birds and
snakes, and by other lizards. I also aim to quantify colour divergence
between P.erhardii populations inhabiting different island environments.
I will take photographs of lizards and their background in both
the UV- and human-visible light spectrum on different Greek islands
(see examples pictured) and model these images through receivers’
eyes. I also plan to conduct mate choice experiments to measure
female colour preferences on different islands, and I will use
predation experiments with clay lizard models to assess how colour
patterns affect survival.
Images of a male P.erhardii individual on the Island
of Syros, Cyclades Islands, Greece (June 2011). Left image shows
human
visible light reflectance and the right image shows ultraviolet
light reflectance. Note brighter UV reflectance on throat and
flanks.
Source: Kate Marshall.
|
I
joined Cambridge in summer 2010 to assist Martin Stevens with his
work on adaptive animal coloration. Since then, I have worked on
a variety of projects using a wide range of methods including psychophysics,
digital photography, computer modelling and reflectance spectrometry.
I have co-supervised a number of student field projects in Madingley
Woods, Cambridge. These include investigating how conspicuous ‘distractive’
markings influence the concealment of otherwise camouflaged artificial
moths from wild bird predators. Another involved collecting video
recordings of bird attacks on artificial butterflies (with mealworm
rewards attached) to examine the potential deflective function of
eyespots.
I have also supervised an undergraduate psychophysical project testing
‘motion dazzle’, a theory that highly contrasting dazzle
patterns, such as stripes, prevent predators from making accurate
estimations about the speed and direction of moving prey. We measured
how different patterns influence the effectiveness of moving and
stationary ‘prey’ capture by human ‘predators’
in a computer game. I recently presented this at the Easter 2011
ASAB research conference.
Additionally, working with Dr Stevens’ collaborators in Japan,
Keita Tanaka and Gen Morimoto, on their field site on Mt. Fuji,
I also helped to objectively examine whether the orange wing patch
of Horsfield’s hawk-cuckoo nestlings (Cuculus fugax) simulate
gapes to increase host provisioning.
At Bristol University I worked with my BSc project supervisor, Dr.
Roland Baddeley, to test whether zebra stripes induce an adaptive
spatial illusion in human vision using psychophysical methods. During
my degrees, I also enjoyed several visits to Lundy Island in the
Bristol Channel where I’ve conducted field work on a variety
of species, including: the colony attendance and breeding site selection
in Atlantic puffins Fratercula arctica; morphology and
distribution of pygmy shrews Sorex minutus; factors affecting habitat,
morphology and sexual behavior in dung beetles Typhaeus typhoeus
and the antipredator function of spittlemass 'cuckoo spit'
produced by froghopper larvae Philaenus spumarius. |
