Morphological analyses are critical to quantify phenotypic variation,identify taxa,inform phylogenetic relationships,and shed light on evolutionary patterns.This work is particularly important in groups that display g...Morphological analyses are critical to quantify phenotypic variation,identify taxa,inform phylogenetic relationships,and shed light on evolutionary patterns.This work is particularly important in groups that display great morphological disparity.Such is the case in geomyoid rodents,a group that includes 2 of the most species-rich families of rodents in North America:the Geomyidae(pocket gophers)and the Heteromyidae(kangaroo rats,pocket mice,and their relatives).We assessed variation in skull morphology(including both shape and size)among geomyoids to test the hypothesis that there are statistically significant differences in skull measurements at the family,genus,and species levels.Our sample includes 886 specimens representing all geomyoid genera and 39 species.We used the geometric mean to compare size across taxa.We used 14 measurements of the cranium and lower jaw normalized for size to compare shape among and within taxa.Our results show that skull measurements enable the distinction of geomyoids at the family,genus,and species levels.There is a larger amount of size variation within Geomyidae than within Heteromyidae.Our phylomorphospace analysis shows that the skull shape of the common ancestor of all geomyoids was more similar to the common ancestor of heteromyids than that of geomyids.Geomyid skulls display negative allometry whereas heteromyid skulls display positive allometry.Within heteromyids,dipodomyines,and non-dipodomyines show significantly different allometric patterns.Future analyses including fossils will be necessary to test our evolutionary hypotheses.展开更多
Geomyoid rodents provide a great study system for the analysis of sexual dimorphism.They are polygynic and many inhabit harsh arid environments thought to promote sexual dimorphism.In fact,there has been extensive wor...Geomyoid rodents provide a great study system for the analysis of sexual dimorphism.They are polygynic and many inhabit harsh arid environments thought to promote sexual dimorphism.In fact,there has been extensive work published on the sexual size dimorphism of individual populations and species within this rodent clade.However,little work has been undertaken to assess the evolutionary patterns and processes associated with this sexual dimorphism.We use multivariate analyses of cranial measurements in a phylogenetic framework to determine the distribution of size and shape dimorphism among geomyoids and test for Rensch’s rule.Our results suggest that sexual dimorphism is more common in geomyids than heteromyids,but it is not in fact universal.There is evidence for variation in sexual dimorphism across populations.Additionally,in many taxa,geographic variation appears to overwhelm existing sexual dimorphism.We find support for the repeated independent evolution of shape and size dimorphism across geomyoid taxa,but we do not find support for an association between size and shape dimorphism.There is no evidence for Rensch’s rule in geomyoids,whether at the superfamily or family level.Together,our findings suggest that there is no single explanation for the evolution of sexual dimorphism in geomyoids and that,instead,it is the product of numerous evolutionary events.Future studies incorporating phylogenetic relationships will be necessary to paint a more complete picture of the evolution of sexual dimorphism in geomyoids.展开更多
基金This research was funded by a Paleontological Society Norman Newel Award,a College of Arts and Sciences Regional Campus Research and Creative Activity Grant from the Ohio State University,a research grant from the Ohio State University at Marion,startup funds from the Ohio State University to JC,and Summer Research Assistantship funds from the Ohio State University at Marion to LN.Some of the ideas for this project were developed while JC was supported by a Meaningful Inquiry grant from The Ohio State University library system.
文摘Morphological analyses are critical to quantify phenotypic variation,identify taxa,inform phylogenetic relationships,and shed light on evolutionary patterns.This work is particularly important in groups that display great morphological disparity.Such is the case in geomyoid rodents,a group that includes 2 of the most species-rich families of rodents in North America:the Geomyidae(pocket gophers)and the Heteromyidae(kangaroo rats,pocket mice,and their relatives).We assessed variation in skull morphology(including both shape and size)among geomyoids to test the hypothesis that there are statistically significant differences in skull measurements at the family,genus,and species levels.Our sample includes 886 specimens representing all geomyoid genera and 39 species.We used the geometric mean to compare size across taxa.We used 14 measurements of the cranium and lower jaw normalized for size to compare shape among and within taxa.Our results show that skull measurements enable the distinction of geomyoids at the family,genus,and species levels.There is a larger amount of size variation within Geomyidae than within Heteromyidae.Our phylomorphospace analysis shows that the skull shape of the common ancestor of all geomyoids was more similar to the common ancestor of heteromyids than that of geomyids.Geomyid skulls display negative allometry whereas heteromyid skulls display positive allometry.Within heteromyids,dipodomyines,and non-dipodomyines show significantly different allometric patterns.Future analyses including fossils will be necessary to test our evolutionary hypotheses.
基金funded by a Paleontological Society Norman Newel Award,a College of Arts and Sciences Regional Campus Research and Creative Activity Grant from the Ohio State University,a research grant from the Ohio State University at Marion,and startup funds from the Ohio State University to J.C.Some of the ideas for this project were developed while J.Cwas supported by a Meaningful Inquiry grant from the Ohio State University library system.
文摘Geomyoid rodents provide a great study system for the analysis of sexual dimorphism.They are polygynic and many inhabit harsh arid environments thought to promote sexual dimorphism.In fact,there has been extensive work published on the sexual size dimorphism of individual populations and species within this rodent clade.However,little work has been undertaken to assess the evolutionary patterns and processes associated with this sexual dimorphism.We use multivariate analyses of cranial measurements in a phylogenetic framework to determine the distribution of size and shape dimorphism among geomyoids and test for Rensch’s rule.Our results suggest that sexual dimorphism is more common in geomyids than heteromyids,but it is not in fact universal.There is evidence for variation in sexual dimorphism across populations.Additionally,in many taxa,geographic variation appears to overwhelm existing sexual dimorphism.We find support for the repeated independent evolution of shape and size dimorphism across geomyoid taxa,but we do not find support for an association between size and shape dimorphism.There is no evidence for Rensch’s rule in geomyoids,whether at the superfamily or family level.Together,our findings suggest that there is no single explanation for the evolution of sexual dimorphism in geomyoids and that,instead,it is the product of numerous evolutionary events.Future studies incorporating phylogenetic relationships will be necessary to paint a more complete picture of the evolution of sexual dimorphism in geomyoids.
