See the page dedicated to Sergey Gavrilet's lab for additional information.
Paper: Palms on an Oceanic Island
Case studies and mathematical models of ecological speciation. 2. Palms on an oceanic island
Sergey Gavrilets and Aaron Vose
2007 Molecular Ecology, Blackwell Publishing Ltd
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A recent study of a pair of sympatric species of palms on the Lord Howe Island is
viewed as providing probably one of the most convincing examples of sympatric speciation
to date. Here we describe and study a stochastic, individual-based, explicit genetic model
tailored for this palms system. Overall, our results show that relatively rapid (< 50 000
generations) colonization of a new ecological niche, and sympatric or parapatric speciation
via local adaptation and divergence in flowering periods are theoretically plausible if
(i) the number of loci controlling the ecological and flowering period traits is small; (ii) the
strength of selection for local adaptation is intermediate; and (iii) an acceleration of flow-
ering by a direct environmental effect associated with the new ecological niche is present.
We discuss patterns and time-scales of ecological speciation identified by our model, and
we highlight important parameters and features that need to be studied empirically in
order to provide information that can be used to improve the biological realism and power
of mathematical models of ecological speciation.
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Download: palms.pdf
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Paper: Cichlids in a Crater Lake
Case studies and mathematical models of ecological speciation. 1. Cichlids in a crater lake
Sergey Gavrilets, Aaron Vose, Marta Barluenga, Walter Salzburger, and Axel Meyer
2007 Molecular Ecology, Blackwell Publishing Ltd
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A recent study of a pair of sympatric species of cichlids in Lake Apoyo in Nicaragua is
viewed as providing probably one of the most convincing examples of sympatric speciation
to date. Here, we describe and study a stochastic, individual-based, explicit genetic model tai-
lored for this cichlid system. Our results show that relatively rapid (< 20 000 generations)
colonization of a new ecological niche and (sympatric or parapatric) speciation via local
adaptation and divergence in habitat and mating preferences are theoretically plausible if:
(i) the number of loci underlying the traits controlling local adaptation, and habitat and
mating preferences is small; (ii) the strength of selection for local adaptation is intermediate;
(iii) the carrying capacity of the population is intermediate; and (iv) the effects of the loci
influencing nonrandom mating are strong. We discuss patterns and timescales of ecological
speciation identified by our model, and we highlight important parameters and features
that need to be studied empirically to provide information that can be used to improve the
biological realism and power of mathematical models of ecological speciation.
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Download: cich.pdf
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Paper: The dynamics of Machiavellian intelligence
The dynamics of Machiavellian intelligence
Sergey Gavrilets and Aaron Vose
2006 Proc. Natl. Acad. Sci. USA 103: 16823-16828
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The "Machiavellian intelligence" hypothesis (or the "social brain" hypothesis) posits that large brains and distinctive cognitive abilities of humans have evolved via intense social competition in which social competitors developed increasingly sophisticated "Machiavellian" strategies as a means to achieve higher social and reproductive success. Here we build a mathematical model aiming to explore this hypothesis. In the model, genes control brains which invent and learn strategies (memes) which are used by males to gain advantage in competition for mates. We show that the dynamics of intelligence has three distinct phases. During the dormant phase only newly invented memes are present in the population. During the cognitive explosion phase the population?s meme count and the learning ability, cerebral capacity (controlling the number of different memes that the brain can learn and use), and Machiavellian fitness of individuals increase in a runaway fashion. During the saturation phase natural selection resulting from the costs of having large brains checks further increases in cognitive abilities. Overall, our results suggest that the mechanisms underlying the "Machiavellian intelligence" hypothesis can indeed result in the evolution of significant cognitive abilities on the time scale of 10 to 20 thousand generations. We show that cerebral capacity evolves faster and to a larger degree than learning ability. Our model suggests that there may be a tendency toward a reduction in cognitive abilities (driven by the costs of having a large brain) as the reproductive advantage of having a large brain decreases and the exposure to memes increases in modern societies.
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Download: mi.pdf
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Paper: Dynamic Patterns of Adaptive Radiation
Dynamic patterns of adaptive radiation
Sergey Gavrilets and Aaron Vose
2005 Proc. Natl. Acad. Sci. USA 102: 18040-18045
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Adaptive radiation is defined as the evolution of ecological and phenotypic diversity within a rapidly multiplying lineage. When it occurs, adaptive radiation typically follows the colonization of a new environment or the establishment of a "key innovation," which opens new ecological niches andor new paths for evolution. Here, we take advantage of recent developments in speciation theory and modern computing power to build and explore a large-scale, stochastic, spatially explicit, individual-based model of adaptive radiation driven by adaptation to multidimensional ecological niches. We are able to model evolutionary dynamics of populations with hundreds of thousands of sexual diploid individuals over a time span of 100,000 generations assuming realistic mutation rates and allowing for genetic variation in a large number of both selected and neutral loci. Our results provide theoretical support and explanation for a number of empirical patterns including "area effect," "overshooting effect," and "least action effect," as well as for the idea of a "porous genome." Our findings suggest that the genetic architecture of traits involved in the most spectacular radiations might be rather simple. We show that a great majority of speciation events are concentrated early in the phylogeny. Our results emphasize the importance of ecological opportunity and genetic constraints in controlling the dynamics of adaptive radiation.
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Download: ar.pdf
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The following projects, while perhaps interesting or fun, are a good few years old now and seem a bit hackish by current standards. Please understand that they are provided along with a slight bit of embarrassment.
pTree: Process Tree Viewer
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I was inspired by `ps auxf`.
If ps can display an ascii tree, I can certainly do better in
OpenGL.
pTree parses the
output of `ps -ef` to gain information about currently
running processes and uses that information to build a process tree in
memory. The process tree is then presented in a fully interactive
3D environment while a background thread applies anti-gravity and
rubber band physics to cause the tree to self organize in space.
Red processes are owned by root, green processes are owned by the
current user, and orange processes are owned by someone else. The
edge color is related its depth in the process tree.
This is still a work in progress and I plan many interface
enhancements. With that in mind, I'll tell you some of the
controls to get you started:
Left mouse down:
Left mouse drag:
Right mouse drag:
Mouse Wheel:
Middle mouse down:
Middle mouse drag:
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Toggle Select
Move Tree X Y
Rotate Tree X Y Z
Move Tree Z
Toggle Anchor
Drag Node
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Download: ptree.tar.bz2
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mChat: 3D Chat Server/Client
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This is a client/server application
that allows the participants to "swim" in a virtual pool floating in
the middle of the air. The participants can't actually chat with
one another, but my excuse is that this is mostly a demonstration
program. Still,
it's fun to play with.
mChat adds a layer of checksums on top of what UDP provides, shows a
working skybox implementation, and is multi-threaded.
The the standard "wasd" system is used to move, and dragging with the
left mouse button will look around (high sensitivity). The right
mouse button will cycle through a short list of avatar skins (your skin
resembles the sample in the bottom right corner).
Download: mchat.tar.bz2
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