Download Beak of the Fish: What Cichlid Flocks Reveal About Speciation

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Beak of the Fish: What
Cichlid Flocks Reveal
About Speciation
Processes
East African Great Lakes and Their Cichlid Flocks
by Holly Jessop
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Introduction
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those fourteen different species of birds continues to
different species has been instructive, then an
fish have evolved thousands of new species within
species that have also emanated from one cichlid
confined to the surface layers and shallow benthic
Cichlid Species: A Kaleidoscope of Form and Color
within the cichlid family provides an opportunity to
reminiscent of aquaria with swarms of colorful fish in
differently colored fish morphs of the same or
used to further uncover the detail in the processes
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characteristics have recently provided an additional
means by which cichlid diversification can be
That is, their classification as separate species was
were derived from different ancestral lines, and in
repeatedly shown that these cichlid radiations have
Origins: Out of Lake Tanganyika Comes Explosive,
Rapid, and Parallel Evolution
Placidochromis
from the fleshy lips of the Lobochilotes
Placidochromis are more closely related
none of these cichlid species are shared between
inter-related becomes an important initial step in
proven to be the most useful tool for this detective
different species separately evolved the same tooth
cichlids are the ancestors from which the cichlids in
independently evolved within different parts of
unrelated, but separately evolved the same color
source reveals that speciation processes within these
Multistage Evolutionary Patterns
The frequent occurrences of parallel evolution
over twice the number of mitochondrial base pairs
and ten times the number of species, confirms that
that they had sampled only 24 of the 200 species of
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This division is then followed by diversification in
differences in color and other communication-related
Speciation Process Stage 1: Division of Habitat
of competitive interspecific influences, early cichlids
adapted to the benthic sand habitat, while others
adapted to the other available benthic substrate that
evolutionary history is well supported by cichlid
Pseudotropheus species have a mouth that is somewhat
Speciation Process Stage 2: Division of Food
Resources
Labeotropheus
that if early speciation processes were not driven by
Labeotropheus
mouths are adaptations that increase the efficiency
Metriaclima cichlids
these species first occurred as a result of trophic
possible food sources, which is reflected in both their
description of cichlid speciation processes that
methodically sift the bottom for detritus, while
birds, males will construct and then defend towers
are free to select any sandcastle territory, and its
success also increases as a function of coloration
in cichlid speciation involves numerous divisions,
all based on colors and behaviors that communicate
do not limit their predation to conspecifics, as many
Similar Speciation Processes in Other Vertebrates
speciation also successfully describes patterns
Speciation Process Stage 3: Division via
Communication
diversified first into bottom- versus water column-
the differences are most notable in male secondary
to select not only the best male, but also to select a
have physically shaped and diversified cichlids, the
found in the Anolis
Anolis comes from
a number of different islands where they evolved
But Why So Many More Cichlids?
While evolutionary scientists have made
evolutionary mechanisms responsible for the uniquely
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to this question continues to evade theorists, but
Additional clues to the mechanisms of evolution
in cichlids have recently been provided by studies
The overall cichlid body plan tends to be
crucial role in cichlid speciation, discovery of the
increase the numbers and types of food items that
Labeotropheus fuelleborni
Metriaclima
zebra
this structure mostly aids directional movement of
were intermediate to that present in the parents,
diet to molluscs, suction up snails with their outer
the spread in frequency becomes wider in the F2
may have unveiled one means by which cichlids
diversified so numerously and rapidly in response to
of every possible food resource, and so to radiate
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and reflection on a more macroscopic-scale are also
diversification in cichlids, then the amino acid
substitutions should have occurred more frequently in
cichlids than finches, despite so many similarities
in the mechanisms involved in their speciation,
acid substitutions should be similar in these cichlids
Bmp4
found that the rate of amino acid substitutions in
Bmp4
Bmp4
speciation rates level off, some species out-compete
role of Bmp4
is also evident from comparisons of cichlids to
protein domain areas affected by these numerous
amino acid substitutions in the Bmp4
found that all substitutions affected the portion of the
protein responsible for post-translational control of
the Bmp4
Bmp4
Disappearing Cichlids
recently been found that the Bmp4
important role in the cranio-facial development of
Bmp4
of the principal molecular variables that provided
comparisons of Bmp4
there with seventy-five percent of their animal
factors involved in the control and modification of
Similarly, the introduction of commercial methods of
a decline in cichlid catch after only twenty years
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Conclusion
cichlids are also valued by the aquarium trade and
speciation are evident in cichlids at small scales, this
practice will undoubtedly disrupt cichlid population
has caused rapid eutrophication and increased
perhaps thousands of spectacularly colored fish will
Figures
ability to properly perceive color was interfered with,
females mated indiscriminately with males of many
for observed decreases in cichlid species diversity
Figure 1:
Great Lake Cichlids Are Monophyletic and Derived
from Lake Tanganyika Flocks.
After Meyer et al. (1990).
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Figure 2:
Similar Cichlid Forms Evolved Independently and Convergently.
From Albertson & Kocher (2006).
Figure 3:
Cichlid Outer Jaw Flexibility and Pharyngeal Jaw Apparatus: Key Innovations.
From Barlow (2000).
Figure 4:
Head, Jaw, and Dentition Differences Between Two Cichlids.
From Albertson & Kocher (2006).
305
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Heredity 97
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102
Evolution 40
94
2
96
inferred from parallel radiations in nuptial
100
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evolutionary processes in East African cichlid
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10
347
Fisheries 6
88
267
273
of the USA 96
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Bmp4
5
19
10
51
300
277
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for a literature review of contemporary scientific
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