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The annotated bibliography must include a minimum of 5 citations from the primary scientific literature. Your annotated bibliography must include complete, properly formatted citations and a description of the article, including how it relates to your topic statement. At least 2 citations should address the evolutionary concept (e.g., review articles, theoretical papers, history, or perspectives) and at least 2 should be for evidence or examples supporting the topic. One citation may be general background, such as natural history, on the focal species or system. Include your Topic Statement at the top of the Annotated Bibliography assignment.my Topic will be on The origin of adaptive radiation of aposematic coloration in poison dart frog ( family Dendrobatidae ) from other Anura that live in the sympatricKeywords: aposematic coloration, Adaptive radiation, poison dart frog, I have 3 Articles if it fit the requirement please used it AND PLEASE LOOK FOR 2 MOREthanks ! please make sure the plagiarsim is less then 1%Annotated Bibliography RubricCriteriaRatingsPtsThis criterion is linked to a Learning OutcomeCitations10.0 to >9.0 ptsExcellent• Correctly formatted. • A minimum of 5 citations including 2 each for the concept and evidence or examples. • From peer-reviewed primary literature. (2 points per citation)9.0 to >0 ptsPartial Credit• Incorrectly formatted (-1 point per citation, up to 5). • Not peer-reviewed source (-1 point per citation, up to 5). • Fewer than required (-2 points per missing citation)10.0 ptsThis criterion is linked to a Learning OutcomeAnnotations40.0 to >39.0 ptsExcellent• Clearly describes the article, including hypotheses, methods, results, and conclusions (4 point per citation). • Relevance to topic statement is well supported (4 point per citation).39.0 to >0 ptsPartial Credit• Missing one of the required components (-1 point per component per citation) • Citation lacks relevance or relevance is not clearly stated. (-1 to 4 points per citation)40.0 ptsExample:
Vestigial wings and the evolution of flightlessness in Galapagos Island cormorants
(Phalacrocorax harrisi) Keywords: vestigiality, flightlessness, Galapagos Island cormorants McNab, B.K., 1994. Energy conservation and the evolution of flightlessness in birds. The
American Naturalist, 144(4), pp.628-642. https://doi.org/10.1086/285697 The author examined the hypothesis that energy conservation contributes to the evolution
of flightlessness in birds by comparing the factors correlated with basal metabolic rate in flighted
and flightless rails and ducks. They found support for their hypothesis in flightless birds, except
penguins, which use their wings for locomotion in water. The authors concluded that a lack of
selective pressure for flight (lack of predators) combined with a high metabolic demand to
maintain flight capability, contributes to vestigiality (reduction of wings and pectoral muscles) in
environments where resources are limited. This article is relevant to my topic statement because
it addresses a hypothesis about how flightlessness and vestigial wings evolved in birds, more
generally
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The evolution of coloration and toxicity in the poison
frog family (Dendrobatidae)
Kyle Summers* and Mark E. Clough
Department of Biology, East Carolina University, Greenville, NC 27858
The poison frogs (family Dendrobatidae) are terrestrial anuran
amphibians displaying a wide range of coloration and toxicity.
These frogs generally have been considered to be aposematic, but
relatively little research has been carried out to test the predictions
of this hypothesis. Here we use a comparative approach to test one
prediction of the hypothesis of aposematism: that coloration will
evolve in tandem with toxicity. Recently, we developed a phylogenetic hypothesis of the evolutionary relationships among representative species of poison frogs, using sequences from three
regions of mitochondrial DNA. In our analysis, we use that DNAbased phylogeny and comparative analysis of independent contrasts to investigate the correlation between coloration and toxicity in the poison frog family (Dendrobatidae). Information on the
toxicity of different species was obtained from the literature. Two
different measures of the brightness and extent of coloration were
used. (i) Twenty-four human observers were asked to rank different photos of each different species in the analysis in terms of
contrast to a leaf-littered background. (ii) Color photos of each
species were scanned into a computer and a computer program
was used to obtain a measure of the contrast of the colors of each
species relative to a leaf-littered background. Comparative analyses of the results were carried out with two different models of
character evolution: gradual change, with branch lengths proportional to the amount of genetic change, and punctuational change,
with all change being associated with speciation events. Comparative analysis using either method or model indicated a significant
correlation between the evolution of toxicity and coloration across
this family. These results are consistent with the hypothesis that
coloration in this group is aposematic.
aposematism 兩 phylogeny 兩 amphibian
A
posematism (warning coloration) occurs when conspicuous
appearance (particularly coloration) functions to advertise
unprofitability (unpalatability, toxicity, or ability to resist or
escape predation) to predators (1). The evolution of aposematism has been the subject of considerable debate (2, 3). A number
of selective factors have been proposed to favor aposematism,
including kin selection (4), individual selection (5), and ultraselfish gene selection (6).
Theoretical models of the evolution of aposematism predict
that conspicuous coloration will become correlated with unprofitability over evolutionary time (1, 7). This evolutionary correlation should be reflected in variation across species: unprofitable species will tend to be more brightly colored than profitable
species, ceteris paribus (8). Studies of a variety of organisms have
pointed to a correlation between measures of unprofitability
(such as unpalatability or toxicity) and bright coloration as
evidence for aposematism [e.g., insects (8), birds (9), amphibians
(10), and reptiles (11)].
Unfortunately, many of the previous investigations of the
correlation between coloration and unpalatability did not
control for phylogenetic affinities among the taxa compared.
Phylogenetic relationships can profoundly bias the correlation
between characters in comparative analyses, and should be
controlled for with specific methods (12). Recently, studies of
aposematism have begun to use these kinds of comparative
www.pnas.org兾cgi兾doi兾10.1073兾pnas.101134898
methods (12, 13). Here we present a comparative analysis of
the evolution of coloration and toxicity in the poison frog
family (Dendrobatidae) by using a recently derived hypothesis
of evolutionary relationships based on mtDNA sequence
variation (14).
The poison frogs are probably best known for the bright
coloration and extreme toxicity that characterizes some species
in this family (15). Dendrobatids produce some of the most toxic
alkaloid poisons known (16). Experiments with mice indicate
that minute quantities of many of these toxins are lethal to
vertebrates if they enter the bloodstream (17, 18). Experiments
with both vertebrate and invertebrate predators have demonstrated the unpalatability of toxic species of Dendrobates and
Phyllobates (18, 19).
These studies suggest that the bright coloration of the toxic
dendrobatids serves an aposematic function, that is, it serves as
warning coloration in interactions with potential predators (15).
However, this hypothesis has not been tested experimentally or
with modern comparative methods. The hypothesis that the
evolution of higher toxicity selects for the evolution of brighter,
more extensive coloration predicts that the evolution of these
two characteristics will be correlated (8). The correlation between the evolution of toxicity and coloration across species can
be tested by using an analysis of independent contrasts, a method
that controls for the effect of phylogenetic affinities in the
comparative analysis of quantitative characters (20).
The diversity of coloration and toxicity in the dendrobatids
makes a comparative approach to this hypothesis feasible, given
an adequate phylogeny for this group. The family Dendrobatidae
is believed to be monophyletic (21), with the toxic dendrobatids
forming a monophyletic clade within the family (22–24). Myers
(25) placed the toxic dendrobatids into four genera: Phyllobates,
Dendrobates, Epipedobates, and Minyobates. Dendrobates and
Phyllobates were diagnosed as sister taxa based on the shared
presence of a unique class of alkaloid toxins (3,5-disubstituted
indolizidines), shared loss of cephalic amplexus during mating,
and complete loss of the primitive oblique lateral stripe (25).
Recent analyses (14) of mtDNA sequence divergence among
species within the family Dendrobatidae has provided a more
detailed hypothesis of phylogenetic relationships among representative species of Allobates, Epipedobates, Minyobates, Phyllobates, and Dendrobates (Fig. 1).
The goal of this study was to use the hypothesis of evolutionary
relationships produced by phylogenetic analysis of mtDNA
sequence data and comparative analysis of independent contrasts (20) to investigate the relationship between toxicity and
coloration in the Dendrobatidae in a phylogenetic context. This
method allows us to disentangle associations among these traits
that are caused by shared ancestry from those that are caused by
tandem evolutionary change (20).
*To whom reprint requests should be addressed. E-mail: [email protected]
The publication costs of this article were defrayed in part by page charge payment. This
article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C.
§1734 solely to indicate this fact.
PNAS 兩 May 22, 2001 兩 vol. 98 兩 no. 11 兩 6227– 6232
EVOLUTION
Communicated by Richard D. Alexander, University of Michigan, Ann Arbor, MI, March 19, 2001 (received for review February 18, 2000)
Fig. 1. Hypothesis of phylogenetic relationships among representative species in the Dendrobatidae, based on mtDNA sequences from cytochrome b, 12S rRNA,
and 16S rRNA gene regions (14). The figure shows the relationships among 21 species for which data on toxicity and coloration were available (Table 1) and is
derived from a more extensive tree including a total of 27 representative species (14). Photos across the top of the figure show representative members of the
following genera: Colostethus (C. talamancae), Epipedobates (E. tricolor), Dendrobates (D. auratus), and Phyllobates (P. bicolor). Structural diagrams along the
bottom show the inferred (by means of parsimony) origins of some representative toxins. From left to right the toxins are a histrionicotoxin, a 3,5-disubstituted
indolizidine, and a batrachotoxin.
Materials and Methods
The aim of this study was to investigate the evolution of
coloration and toxicity in representative species of poison frogs.
Therefore, we acquired data on coloration and on toxicity for
each of the species listed in Table 1.
Data on coloration was obtained from ratings of color photographs of species in the phylogeny. Ratings were obtained from
a total of 24 human observers. The observers were not familiar
with the frogs and did not know the levels of toxicity in the
different species. A photo (taken with a flash) showing the
dorsum and side of each of 21 species was rated for brightness
and extent of coloration in a composite measure. The mean
measure of coloration across observers was used for each species
(Table 1). Naturally, it would be preferable to use potential
predators rather than humans to rate the coloration of the frogs,
but this method was not feasible. Birds are likely to represent an
important class of predators for small vertebrates living on the
forest floor, including anurans (26). Recent research suggests
that animals that appear colorful to humans are also likely to
appear colorful to birds (27).
An independent analysis of coloration was done by using
scanned color photos (taken with a flash) of each species in the
phylogeny. By using the pixel sampler in the computer program
Adobe PHOTOSHOP (28), the brightness of color for each of the
three major color hues (red, blue, and green) was sampled at 10
6228 兩 www.pnas.org兾cgi兾doi兾10.1073兾pnas.101134898
different points on each differently colored region of each
species. The proportion of the frog that each colored region
comprised was measured with the National Institutes of Health
IMAGE program (29). A similar analysis was carried out on
photos of leaf litter (taken with a flash), which allowed us to
contrast the overall brightness of coloration of each species of
frog relative to a leaf-littered background. Overall coloration
was quantified as the contrast (to leaf litter) for each colored
region multiplied by the proportion of the frog that each colored
region comprised. The data from the computer ratings are shown
in Table 1. The scale of variation in coloration was 1–10 for both
the observer and computer-rated analyses.
Information on the toxicity of different species was taken from
the work of Daly et al. (30). Overall toxicity was scored for three
different attributes: diversity, quantity, and lethality. Diversity
refers to the number of different toxins found in skin extracts
from each species. Quantity refers to the amount of alkaloids
detected in 100 mg of skin: 3 ⫽ ⬎ 150 ␮g兾mg; 2 ⫽ 50 ⫺ 150
␮g兾mg; 1 ⫽ 1 ⫺ 50 ␮g兾mg; and 0 ⫽ no alkaloids detected (30).
Data on both diversity and quantity were averaged across
populations when more than one population of a species was
sampled.
Data on the lethality of all of the different dendrobatid toxins
has not yet been published, but the evidence indicates that the
batrachotoxins are the most toxic alkaloids found in these frogs
Summers and Clough
Genus
Allobates
Colostethus
Colostethus
Dendrobates
Dendrobates
Dendrobates
Dendrobates
Dendrobates
Dendrobates
Dendrobates
Dendrobates
Epipedobates
Epipedobates
Epipedobates
Epipedobates
Epipedobates
Epipedobates
Minyobates
Phyllobates
Phyllobates
Phyllobates
Species
Diversity
Quantity
Lethality
Total toxicity
Coloration (observer)
Coloration (computer)
femoralis
marchesianus
talamancae
auratus
granuliferus
histrionicus
leucomelas
pumilio
speciosus
tinctorius
ventrimaculatus
anthonyi
bilinguis
boulengeri
hahneli
tricolor
trivittatus
minutus
bicolor
lugubris
vittatus
0.17
0
0
16.8
17
18.1
7
16
18.5
10
12.5
2
6
12
6
13
8
7
12
1.7
2
0.167
0
0
2.556
2
2.571
1
2.25
2.75
2
2
1
1.5
1
2
3
2.667
1.2
3
0.67
1
1
0
0
2
2
2
2
2
2
2
2
1
1
1
1
1
1
1
3
3
3
1.2
0
0
6.2
5.7
6.4
3.7
5.9
6.6
5
5.3
2.2
3.1
3.2
3.6
5.3
4.5
2.9
7.2
3.8
4.2
3.8
2.2
1.1
5.9
6.7
7.1
7.1
7.8
7.9
7.8
6.1
4.8
4.8
1.6
3.3
5.6
5.7
3.7
7.9
3.7
4.3
0.3
0.2
0.7
4.8
3.4
2.9
2.6
4.4
4.0
3.7
3.2
1.7
1.3
0.5
1.1
2.0
2.9
1.0
8.5
1.7
4.5
Total toxicity was a composite measurement of the diversity, quantity, and toxicity of the toxins found in each species. Coloration was scored with computer
software and by human observers (see text).
[and one of the most toxic alkaloids on earth (16)]. The second
most toxic class of alkaloids produced by these frogs seems to be
the pumiliotoxins classes A and B, which are substantially more
lethal than the other major classes of alkaloids identified in these
frogs (18). The batrachotoxins are found only in the members of
the genus Phyllobates (16). Classes A and B pumiliotoxins are
found as major components of the alkaloid profile mainly in the
genus Dendrobates (13 of 14 species analyzed) and rarely in the
genus Epipedobates (1 of 8 species analyzed; ref. 30). Phyllobates
and Dendrobates also share a class of toxins, the 3,5-disubstituted
indolizidines (31), which are not found in Epipedobates, Minyobates, Allobates, or Colostethus.
Hence the category ‘‘lethality’’ attempts to quantify consistent
differences among genera in the toxicity of the major components of their skin-alkaloid profiles. This measure was scored on
a four-point scale, with Phyllobates receiving the highest score
with 3, Dendrobates next with 2, Epipedobates and Minyobates
next with 1, and Colostethus [most members of which showed
little or no toxicity (31)] was given the lowest rating of 0.
These measures were combined for an overall toxicity score as
follows (Table 1): (0.1)(diversity) ⫹ (quantity) ⫹ (lethality). The
scale on which diversity was measured was ⬇10 times larger than
that of the other factors (Table 1), thus down-weighting diversity
relative to quantity and lethality actually assigns approximately
equal weight to each category in the final composite measure of
overall toxicity. The exact contribution of each of these three
aspects of toxicity (diversity, quantity, and lethality) to overall
toxicity is not known, but tests with mice suggest that quantity
contributes to the overall lethality of different species of poison
frogs [survival time for mice injected with toxic alkaloids from
poison frogs is dosage-dependent (17)]. Tests with mice also
indicate that some toxins that are unique or major alkaloid
components in only certain taxa (such as batrachotoxin) are
much more lethal than others (18). The contribution of toxin
diversity to overall toxicity is not known but a more diverse toxin
profile is likely to increase both lethality and unpalatability,
ceteris paribus.
Data on toxicity refers to average levels for specific species
(not the specific individuals scored for color in the photographs
Summers and Clough
as described above). Data on toxicity were not available for
Epipedobates boulengeri but we assigned toxicity to it according
to that of its closest relative, Epipedobates espinosai [these two
species were previously considered conspecific (23)]. E. espinosai
is more brightly colored than E. boulengeri (23) and shows
moderate toxicity (30). Hence, this assignation is likely to be
conservative with respect to the hypothesis that coloration and
toxicity coevolve. Some researchers have classified Epipedobates
tricolor and Epipedobates anthonyi as members of the same
species (32). Hence, we have not included a contrast between
these two species or populations in our analysis, but we have
placed the data for both of them in the overall analysis to
compare both with the other species in the phylogeny. Populations of two species sampled by Daly et al. (30) have since been
assigned to different species names: Epipedobates hahneli for
Epipedobates pictus and Epipedobates bilinguis for Epipedobates
parvulus (14). The names E. hahneli and E. bilinguis are used in
this article.
The phylogenetic analysis was carried out with sequence data
from portions of the 16S rRNA, 12S rRNA, and cytochrome b
regions of mtDNA from each species. The combination of 16S
rRNA, 12S rRNA, and cytochrome b sequence fragments provided a total of 1,198 bases for analysis, of which 589 exhibited
1 or more state changes (14).
Phylogenetic analysis [using the program PAUP (33)] produced
a single most parsimonious tree for the ingroup taxa, but the
outgroup species (Colostethus talamancae and Colostethus
marchesianus) formed a basal polytomy with the ingroup (Fig. 1).
This hypothesis of phylogenetic relationships had a consistency
index of 0.48 and a retention index of 0.62, with a total tree length
of 1,823 (14). The results of the analysis were largely in agreement with the generic relationships proposed by Myers (25), with
the exception that Allobates femoralis was placed outside of the
other toxic dendrobatids, and Minyobates minutus was placed as
the sister species to a species within the genus Dendrobates
(Dendrobates ventrimaculatus). The results also were congruent
with a recent hypothesis of phylogenetic relationships within the
genus Dendrobates based on a different mtDNA data set (34),
with the exception of the relationships among Dendrobates
PNAS 兩 May 22, 2001 兩 vol. 98 兩 no. 11 兩 6229
EVOLUTION
Table 1. Data used for the comparative analysis of toxicity and coloration
Table 2. Statistics for the regression of the standardized contrasts of coloration on toxicity, under the punctuational and gradual
models of evolutionary change, using observer- and computer-rated estimates of coloration
Model
Punctuational
Gradual
Punctuational
Gradual
Rating
Contrasts
Tandem
R2
F value
t value
P value
Observer
Observer
Computer
Computer
17
17
17
17
14
13
15
15
0.51
0.38
0.83
0.71
16.43
9.83
78.89
38.27
4.10
3.14
8.88
6.19
0.001
0.006
0.000
0.000
Tandem refers to the number of contrasts in which toxicity and coloration evolved in the same direction.
histrionicus, Dendrobates pumilio, and Dendrobates speciosus.
The relationships among these species were not supported
strongly in our phylogenetic analysis (14), thus this clade was
collapsed into a polytomy for the comparative analysis (Fig. 1).
The phylogenetic tree derived from mtDNA data, together
with data on coloration and toxicity, were used to generate
phylogenetically independent contrasts by using the computer
program CAIC (35). This method enabled us to investigate the
correlation between evolutionary change in coloration and
toxicity. Recent studies suggest that methods that reconstruct
ancestral states can be subject to substantial levels of uncertainty
(36). However, this type of uncertainty has a stronger effect on
the results of methods that rely on the exact reconstruction of
each ancestral state than on correlative comparative methods
(such as the comparative analysis of independent contrasts), in
which ancestral-state reconstruction plays a secondary role (36).
Recent research indicates that the comparative analysis of
independent contrasts accurately reconstructs correlations between evolutionary events, even when exact ancestral states are
not accurately reconstructed (37). Given a general lack of
knowledge about modes of character evolution, the most conservative approach when using comparative analysis of independent contrasts is to try several distinct models of character
evolution to determine whether different assumptions substantially alter the results of the analysis (38). Here we have used two
maximally distinctive models of character evolution, both of
which can be implemented by CAIC, a punctuational model in
which all change occurs at speciation (cladogenetic) events, and
a gradual change model, in which the amount of change is
proportional to the branch length. Branch lengths were calculated on the basis of the amount of genetic change occurring on
each branch. Genetic change was quantified as the genetic
distance based on sequence divergence from our previous
analysis of mtDNA sequences (14), calculated with the Kimura
(39) two-parameter model.
The relationships between the standardized contrasts produced by CAIC were tested for statistical significance by regre …
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