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Rapid Morphological Change in the Masticatory Structures of an Important Ecosystem Service Provider.

Doudna JW, Danielson BJ - PLoS ONE (2015)

Bottom Line: Thus, it is striking that some species continue to thrive under such conditions.In order to understand the evolutionary history of this species' masticatory structures, we examined the maxilla, zygomatic plate, and mandible of historic specimens collected prior to 1910 to specimens collected in 2012 and 2013.We found that mandibles, zygomatic plates, and maxilla have all changed significantly since 1910, and that morphological development has shifted significantly.

View Article: PubMed Central - PubMed

Affiliation: Ecology, Evolution, and Organismal Biology Department, Iowa State University, Ames, Iowa, United States of America.

ABSTRACT
Humans have altered the biotic and abiotic environmental conditions of most organisms. In some cases, such as intensive agriculture, an organism's entire ecosystem is converted to novel conditions. Thus, it is striking that some species continue to thrive under such conditions. The prairie deer mouse (Peromyscus maniculatus bairdii) is an example of such an organism, and so we sought to understand what role evolutionary adaptation played in the success of this species, with particular interest in adaptations to novel foods. In order to understand the evolutionary history of this species' masticatory structures, we examined the maxilla, zygomatic plate, and mandible of historic specimens collected prior to 1910 to specimens collected in 2012 and 2013. We found that mandibles, zygomatic plates, and maxilla have all changed significantly since 1910, and that morphological development has shifted significantly. We present compelling evidence that these differences are due to natural selection as a response to a novel and ubiquitous food source, waste grain (corn, Zea mays and soybean, Glycine max).

No MeSH data available.


Related in: MedlinePlus

Landmarks (circles) and semilandmarks (triangles) digitized onto each specimen.Landmarks are detailed in Table 2.
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pone.0127218.g002: Landmarks (circles) and semilandmarks (triangles) digitized onto each specimen.Landmarks are detailed in Table 2.

Mentions: In order to determine the changes in shape of P. m. bairdii jaws, data were collected from upper and lower jaw structures associated with masticatory muscle attachments. To this end, photographs were taken of the left, lateral perspective of skulls and mandibles separately for all specimens. A few exceptions occurred when historic specimens could not be disarticulated, so photographs were taken with skulls and mandibles attached. Occasionally, photographs of the right side of the specimen were taken, when the left side was too damaged for analysis. A setup of a digital camera with a macro lens was used, set at approximately 0.5m from the specimen, and a mm ruler was oriented along the long axis of the specimen and camera lens. Jaws were aligned so that the left side of the left mandible was aligned with the ruler, while the skull was aligned so that the left zygomatic arch was aligned with the ruler, and the sagittal suture was parallel to the ruler. A Canon EOS XT with an 8.0 MP sensor with a 100mm macro lens (EF = 1:2.8) was used for all photography. After all pictures had been collected, upper and lower jaw landmarks were digitized for all specimens. Landmarks followed McPhee and Myers et al. [25,26], but were modified for this species and question (Fig 2 and Table 2). We chose to exclude incisor and individual tooth landmarks due to tooth wear and movement or loss. Nine landmarks and 7 semilandmarks were digitized on the upper jaw, and 10 landmarks and 7 semilandmarks were digitized on the mandible. Landmarks were a combination of Type 1 and Type 2 landmarks (points of intersection of structures and points of maximum or minimum curvature). Semilandmarks are landmarks along a curve that are moved along that curve during the analysis. All specimens were digitized in tpsDig2 ([27], vers. 2.17). In order to test for errors associated with order of photography, a random subset of 25% of the specimens were re-photographed. No evidence was found that specimens from the original and follow-up test were different (Mean Square Error [MS] = 0.00247, p = 0.22). A random subset of 10% of specimens were re-digitized and a significant effect of practice time was found on digitization of upper jaws, but not mandibles. Therefore, all upper jaws were re-digitized in random order to remove experience bias.


Rapid Morphological Change in the Masticatory Structures of an Important Ecosystem Service Provider.

Doudna JW, Danielson BJ - PLoS ONE (2015)

Landmarks (circles) and semilandmarks (triangles) digitized onto each specimen.Landmarks are detailed in Table 2.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4465031&req=5

pone.0127218.g002: Landmarks (circles) and semilandmarks (triangles) digitized onto each specimen.Landmarks are detailed in Table 2.
Mentions: In order to determine the changes in shape of P. m. bairdii jaws, data were collected from upper and lower jaw structures associated with masticatory muscle attachments. To this end, photographs were taken of the left, lateral perspective of skulls and mandibles separately for all specimens. A few exceptions occurred when historic specimens could not be disarticulated, so photographs were taken with skulls and mandibles attached. Occasionally, photographs of the right side of the specimen were taken, when the left side was too damaged for analysis. A setup of a digital camera with a macro lens was used, set at approximately 0.5m from the specimen, and a mm ruler was oriented along the long axis of the specimen and camera lens. Jaws were aligned so that the left side of the left mandible was aligned with the ruler, while the skull was aligned so that the left zygomatic arch was aligned with the ruler, and the sagittal suture was parallel to the ruler. A Canon EOS XT with an 8.0 MP sensor with a 100mm macro lens (EF = 1:2.8) was used for all photography. After all pictures had been collected, upper and lower jaw landmarks were digitized for all specimens. Landmarks followed McPhee and Myers et al. [25,26], but were modified for this species and question (Fig 2 and Table 2). We chose to exclude incisor and individual tooth landmarks due to tooth wear and movement or loss. Nine landmarks and 7 semilandmarks were digitized on the upper jaw, and 10 landmarks and 7 semilandmarks were digitized on the mandible. Landmarks were a combination of Type 1 and Type 2 landmarks (points of intersection of structures and points of maximum or minimum curvature). Semilandmarks are landmarks along a curve that are moved along that curve during the analysis. All specimens were digitized in tpsDig2 ([27], vers. 2.17). In order to test for errors associated with order of photography, a random subset of 25% of the specimens were re-photographed. No evidence was found that specimens from the original and follow-up test were different (Mean Square Error [MS] = 0.00247, p = 0.22). A random subset of 10% of specimens were re-digitized and a significant effect of practice time was found on digitization of upper jaws, but not mandibles. Therefore, all upper jaws were re-digitized in random order to remove experience bias.

Bottom Line: Thus, it is striking that some species continue to thrive under such conditions.In order to understand the evolutionary history of this species' masticatory structures, we examined the maxilla, zygomatic plate, and mandible of historic specimens collected prior to 1910 to specimens collected in 2012 and 2013.We found that mandibles, zygomatic plates, and maxilla have all changed significantly since 1910, and that morphological development has shifted significantly.

View Article: PubMed Central - PubMed

Affiliation: Ecology, Evolution, and Organismal Biology Department, Iowa State University, Ames, Iowa, United States of America.

ABSTRACT
Humans have altered the biotic and abiotic environmental conditions of most organisms. In some cases, such as intensive agriculture, an organism's entire ecosystem is converted to novel conditions. Thus, it is striking that some species continue to thrive under such conditions. The prairie deer mouse (Peromyscus maniculatus bairdii) is an example of such an organism, and so we sought to understand what role evolutionary adaptation played in the success of this species, with particular interest in adaptations to novel foods. In order to understand the evolutionary history of this species' masticatory structures, we examined the maxilla, zygomatic plate, and mandible of historic specimens collected prior to 1910 to specimens collected in 2012 and 2013. We found that mandibles, zygomatic plates, and maxilla have all changed significantly since 1910, and that morphological development has shifted significantly. We present compelling evidence that these differences are due to natural selection as a response to a novel and ubiquitous food source, waste grain (corn, Zea mays and soybean, Glycine max).

No MeSH data available.


Related in: MedlinePlus