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130 results for “mammalian evolution”
Data from: Head-turning morphologies: evolution of shape diversity in the mammalian atlas-axis complex
Mammals flex, extend, and rotate their spines as they perform behaviors critical for survival, such as foraging, consuming prey, locomoting, and interacting with conspecifics or predators. The atlas-axis complex is a mammalian innovation that allows precise head movements during these behaviors. While morphological variation in other vertebral regions has been linked to ecological differences in mammals, less is known about morphological specialization in the cervical vertebrae, which are developmentally constrained in number but highly variable in size and shape. Here, we present the first phylogenetic comparative study of the atlas-axis complex across mammals. We used spherical harmonics to quantify 3D shape variation of the atlas and axis across a diverse sample of species, and performed phylogenetic analyses to investigate if vertebral shape is associated with body size, locomotion, and diet. We found that differences in atlas and axis shape are partly explained by phylogeny, and that mammalian subclades differ in morphological disparity. Atlas and axis shape diversity is associated with differences in body size and locomotion; large terrestrial mammals have craniocaudally elongated vertebrae, while smaller mammals and aquatic mammals have more compressed vertebrae. These results provide a foundation for investigating functional hypotheses underlying the evolution of neck morphologies across mammals.
Data from: Mammalian evolution: timing and implications from using the LogDeterminant transform for proteins of differing amino acid composition
We explore the tree of mammalian mtDNA sequences, using particularly the LogDet transform on amino acid sequences, the distance Hadamard transform, and the Closest Tree selection criterion. The amino acid composition of different species show significant differences, even within mammals. After compensating for these differences, nearest-neighbor bootstrap results suggest that the tree is locally stable, though a few groups show slightly greater rearrangements when a large proportion of the constant sites are removed. Many parts of the trees we obtain agree with those on published protein ML trees. Interesting results include a preference for rodent monophyly. The detection of a few alternative signals to those on the optimal tree were obtained using the distance Hadamard transform (with results expressed as a Lento plot). One rearrangement suggested was the interchange of the position of primates and rodents on the optimal tree. The basic stability of the tree, combined with two calibration points (whale/cow and horse/rhinoceros), together with a distant secondary calibration from the mammal/bird divergence, allows inferences of the times of divergence of putative clades. Allowing for sampling variances due to finite sequence length, most major divergences amongst lineages leading to modern orders, appear to occur well before the Cretaceous/Tertiary (K/T) boundary. Implications arising from these early divergences are discussed, particularly the possibility of competition between the small dinosaurs and the new mammal clades.
Data from: Phylogenetic evidence for a shift in the mode of mammalian body size evolution at the Cretaceous-Paleogene boundary
NOTE: Please also see Slater (2014) published in Methods in Ecology and Evolution at http://dx.doi.org/10.1111/2041-210X.12201 1. Phylogenetic comparative methods provide a powerful way of addressing classic questions about tempo and mode of phenotypic evolution in the fossil record, such as whether mammals increased in body size diversity after the Cretaceous-Paleogene (K-Pg) extinction. 2. Most often, these kinds of questions are addressed in the context of variation in evolutionary rates. Shifts in the mode of phenotypic evolution provides an alternative and, in some cases, more realistic explanation for patterns of trait diversity in the fossil record but these kinds of processes are rarely tested for. 3. In this study, I use a time-calibrated phylogeny of living and fossil Mammaliaformes as a framework to test novel models of body size evolution derived from paleontological theory. Specifically, I ask whether the K-Pg extinction resulted in a change in rates of body size evolution or release from a constrained adaptive zone. 4. I found that a model comprising an Ornstein-Uhlenbeck process until the K-Pg event and a Brownian motion process from the Cenozoic onwards was the best supported model for these data. Surprisingly, results indicate a lower absolute rate of body size evolution during the Cenozoic than during the Mesozoic. This is explained by release from a stationary OU process that constrained realized disparity. Despite a lower absolute rate, body size disparity has in fact been increasing since the K-Pg event 5. The use of time-calibrated phylogenies of living and extinct taxa and realistic, process-based models provides unparalleled power in testing evolutionary hypotheses. However, researchers should take care to ensure that the models they use are appropriate to the question being tested, and that the parameters estimated are intepreted in the context of the best-fitting model.
Data from: The evolution of ontogenetic allometric trajectories in mammalian domestication
Morphological divergence of domesticated as compared to wild forms must result from changes in the ontogenetic process. Species-specific tests for heterochrony have rejected a single explanation of domestic forms representing juveniles of their wild relatives. Ontogenetic allometric trajectories for 12 pairs of wild and domestic mammals were examined using skull growth data for 1070 specimens, including representatives from all lineages in which domestication has occurred. A suite of tests were performed to quantify allometric disparity in wild and domestic forms and assess the extent and patterning of modification to allometric trajectories. Domestication has modified postnatal ontogenetic allometric trajectories in mammals, and has generated disparity, achieved through lengthening of trajectory slopes and alteration to slope angles. Allometric disparity was similar for domestic forms compared to their wild relatives, whereas the magnitude of dispersion along allometric vectors differed between precocial mammals and altricial mammals, underscoring the importance of life history and shared evolutionary history in patterns of ontogenetic variation. The results verify the importance of scaling in the morphological changes associated with domestication. The response to domestication for all measured trajectory parameters was variable across species, suggesting multiple pathways of change.
Data from: Lineage-independent retrotransposition of UTP14 associated with male fertility has occurred multiple times throughout mammalian evolution
In mammals, gamete production is essential for reproductive success. This is particularly true for males where large quantities of sperm are produced to fertilize a limited number of eggs released by the female. Because of this, new genes associated with increased spermatogenic efficiency have been accumulating throughout the evolution of therian mammals. Many of these new genes are testis-specific retrotransposed copies of housekeeping genes located on the X chromosome. Of particular interest are retrotransposed copies of UTP14 that are present in many distantly related eutherian mammals. Analysis of genomic data available in ENSEMBL indicates that these UTP14 retrogenes have arisen independently in the various eutherian clades. They represent an interesting aspect of evolution whereby new homologues of UTP14 have become independently fixed in multiple mammalian lineages due to the reproductive advantage that may be conferred to males. Surprisingly, these genes may also be lost, even after being present within a lineage for millions of years. This phenomenon may potentially be used to delineate evolutionary trees in closely related groups of mammals, particularly in the case of South American primates. Studying these retrogenes will yield new insights into the evolutionary history of male gamete production and the phylogeny of eutherian mammals.
Complementary evolution of coding and noncoding sequence underlies mammalian hairlessness
<p><span>Body hair is a defining mammalian characteristic, but several mammals, such as whales, naked mole-rats, and humans, have notably less hair than others. To find the genetic basis of reduced hair quantity, we used our evolutionary-rates-based method, RERconverge, to identify coding and noncoding sequences that evolve at significantly different rates in so-called hairless mammals compared to hairy mammals. Using RERconverge, we performed an unbiased, genome-wide scan over 62 mammal species using 19,149 genes and 343,598 conserved noncoding regions to find genetic elements that evolve at significantly different rates in hairless mammals compared to hairy mammals. We show that these rate shifts resulted from relaxation of evolutionary constraint on hair-related sequences in hairless species. In addition to detecting known and potential novel hair-related genes, we also discovered hundreds of putative hair-related regulatory elements. Computational investigation revealed that genes and their associated noncoding regions show different evolutionary patterns and influence different aspects of hair growth and development. Many genes under accelerated evolution are associated with the structure of the hair shaft itself, while evolutionary rate shifts in noncoding regions also included the dermal papilla and matrix regions of the hair follicle that contribute to hair growth and cycling. Genes that were top-ranked for coding sequence acceleration included known hair and skin genes KRT2, KRT35, PKP1, and PTPRM that surprisingly showed no signals of evolutionary rate shifts in nearby noncoding regions. Conversely, accelerated noncoding regions are most strongly enriched near regulatory hair-related genes and microRNAs, such as mir205, ELF3, and FOXC1, that themselves do not show rate shifts in their protein-coding sequences. Such dichotomy highlights the interplay between the evolution of protein sequence and regulatory sequence to contribute to the emergence of a convergent phenotype.</span></p>
Data for: The evolution of mammalian Rem2: unraveling the impact of purifying selection and coevolution on protein function, and implications for human disorders
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Fig. 33 in Cranial Anatomy Of Kryptobaatar Dashzevegi (Mammalia, Multituberculata), And Its Bearing On The Evolution Of Mammalian Characters
Fig. 33. Reconstruction of the skull of Kryptobaatar dashzevegi in lateral view. Abbreviations: al anterior lamina; exoc exoccipital; fr frontal; lac lacrimal; man mandible; mx maxilla; na nasal; or orbitosphenoid; pa parietal; pet petrosal; pmx premaxilla; sq squamosal; sth stylohyal.
Fig. 28 in Cranial Anatomy Of Kryptobaatar Dashzevegi (Mammalia, Multituberculata), And Its Bearing On The Evolution Of Mammalian Characters
Fig. 28. The floor of the endocranium of the platypus Ornithorhynchus anatinus in dorsal view (modified from Zeller, 1989: fig. 6, with the author's permission). Parallel lines represent the cut edge of the braincase. Abbreviations: al anterior lamina; bo basioccipital; fV2 foramen for maxillary nerve fV3 foramen for mandibular nerve; hf hypophyseal fossa; iam internal acoustic meatus; jfo 1 hyf confluent jugular and hypoglossal foramina; jsp jugum sphenoidale; mlcp middle clinoid process (ossified remnant of pila antotica); onsf orbitonasal foramen; pet petrosal; pp pila preoptica; prc prootic canal; psf pseudoptic foramen (for II, III, IV, V1, VI); ptc posttemporal canal; sf subarcuate fossa; sq squamosal; tus tuberculum sellae; vaq vestibular aqueduct.
Fig. 30 in Cranial Anatomy Of Kryptobaatar Dashzevegi (Mammalia, Multituberculata), And Its Bearing On The Evolution Of Mammalian Characters
Fig. 30. Stereophotograph of the left lower jaw of Kryptobaatar dashzevegi PSSMAE 113 in medial view.
Figure 16 in Postcranial anatomy of Haldanodon exspectatus (Mammalia, Docodonta) from the Late Jurassic (Kimmeridgian) of Portugal and its bearing for mammalian evolution
Figure 16. Strict consensus tree of 27 equally parsimonious trees for early mammals based on 280 cranio-mandibular and postcranial characters using PAUP 4.0b10 with heuristic branch-and bound search, set at random with 1000 replicates; starting seed = 1794832392. All characters unordered and with equal weight. Each of the 27 equally parsimonious trees has: Treelength = 956, CI = 0.500, RI = 0.763. Haldanodon (arrow) appears above the node of morganucodontids as sister taxon of the common ancestor of Hadrocodium and living mammals plus all of its descendants (node 2 in Luo et al., 2002: figs 1, 2). For character states and score for Haldanodon see the Appendix.
Figure 11. Haldanodon exspectatus, Gui Mam 30 in Postcranial anatomy of Haldanodon exspectatus (Mammalia, Docodonta) from the Late Jurassic (Kimmeridgian) of Portugal and its bearing for mammalian evolution
Figure 11. Haldanodon exspectatus, Gui Mam 30/79. Left femur as originally embedded in a posterior (= ventral) aspect. The width of the shaft is exaggerated due to crushing during fossilization.
Figure 8. Haldanodon exspectatus, Gui Mam 30 in Postcranial anatomy of Haldanodon exspectatus (Mammalia, Docodonta) from the Late Jurassic (Kimmeridgian) of Portugal and its bearing for mammalian evolution
Figure 8. Haldanodon exspectatus, Gui Mam 30/79. Left humerus in: A, anterior; B, medial; C, posterior; D, lateral; and E, distal view. entepic., entepicondylar; entepico., entepicondyle; intertuberc., intertubercular; tuber., tuberosity.
Figure 1. Haldanodon exspectatus, Gui Mam 30 in Postcranial anatomy of Haldanodon exspectatus (Mammalia, Docodonta) from the Late Jurassic (Kimmeridgian) of Portugal and its bearing for mammalian evolution
Figure 1. Haldanodon exspectatus, Gui Mam 30/79. Incomplete and dislocated postcranial skeleton associated with skull and right mandible. M5, fifth upper molar; ri, right.
Data from: Phylogenetic evidence for a shift in the mode of mammalian body size evolution at the Cretaceous-Paleogene boundary
Open the record for dataset details and reuse information.
Data from: Head-turning morphologies: evolution of shape diversity in the mammalian atlas-axis complex
Open the record for dataset details and reuse information.
Data from: Lineage-independent retrotransposition of UTP14 associated with male fertility has occurred multiple times throughout mammalian evolution
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Data from: Mammalian evolution: timing and implications from using the LogDeterminant transform for proteins of differing amino acid composition
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Data from: Size variation, growth strategies and the evolution of modularity in the mammalian skull
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Data from: The evolution of ontogenetic allometric trajectories in mammalian domestication
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