Chromosomal evolution is widely considered an important driver of speciation because it can promote the establishment of reproductive barriers.Karyotypic reorganization is also expected to affect the mea n phe no type...Chromosomal evolution is widely considered an important driver of speciation because it can promote the establishment of reproductive barriers.Karyotypic reorganization is also expected to affect the mea n phe no type,as well as its developme nt and patter ns of phenotypic in tegrati on,through processes such as variation in genetic linkage between quantitative trait loci or between regulatory regions and their targets.Here we explore the relationship between chromosomal evolution and phenotypic integration by analyzing a well-known house mouse parapatric contact zone between a highly derived Robertsonian(Rb)race(2n=22)and populations with standard karyotype(2n=40).Populations with hybrid karyotypes are scattered throughout the hybrid zone connecting the two parental races.Using mandible shape data and geometric morphometries,we test the hypothesis that patter ns of in tegration progressively diverge from the"normal"integration pattern observed in the standard race as they accumulate Rb fusions.We find that the main pattern of integration observed between the posterior and anterior part of the mandible can be largely attributed to allometry.We find no support for a gradual increase in divergence from normal patterns of integration as fusions accumulate.Surprisingly,however,we find that the derived Rb race(2n=22)has a distinct allometric trajectory compared with the standard race.Our results suggest that either individual fusions disproportionately affect patterns of integration or that there are mechanisms which"purge"extreme variants in hybrids(e.g.reduced fitness of hybrid shape).展开更多
Selective pressures favor morphologies that are adapted to distinct ecologies,resulting in trait partition!ng among ecomorphotypes.However,the effects of these selective pressures vary across taxa,especially because m...Selective pressures favor morphologies that are adapted to distinct ecologies,resulting in trait partition!ng among ecomorphotypes.However,the effects of these selective pressures vary across taxa,especially because morphology is also influenced by factors such as phylogeny,body size,and functional trade-offs.In this study,we examine how these factors impact functional diversification in mammals.It has been proposed that trait partitioning among mammalian ecomorphotypes is less pronoun ced at small body sizes due to biomecha nical,energetic,and environ mental factors that favor a"generalist"body plan,whereas larger taxa exhibit more substantial functional adaptations.We title this the Diverge nee Hypothesis(DH)because it predicts greater morphological divergence among ecomorphotypes at larger body sizes.We test DH by using phylogenetic comparative methods to examine the postcranial skeletons of 129 species of taxonomically diverse,small-tomedium-sized(<15 kg)mammals,which we categorize as either"tree-dwellers"or"ground-dwellers."In some analyses,the morphologies of ground-dwellers and tree-dwellers suggest greater between-group differentiation at larger sizes,providing some evidence for DH.However,this trend is n either particularly strong nor supported by all an alyses.In stead,a more pronoun ced patter n emerges that is distinct from the predictions of DH:within-group phenotypic disparity increases with body size in both ground-dwellers and tree-dwellers,driven by morphological outliers among"medium'-sized mammals.Thus,evolutionary increases in body size are more closely linked to increases in within-locomotor-group disparity tha n to in creases in betwee n-group disparity.We discuss biomechanical and ecological factors that may drive these evolutionary patter ns,and we emphasize the significant evolutionary influences of ecology and body size on phenotypic diversity.展开更多
基金the Ministry of Scientific Research and Education,Italy(MIUR).
文摘Chromosomal evolution is widely considered an important driver of speciation because it can promote the establishment of reproductive barriers.Karyotypic reorganization is also expected to affect the mea n phe no type,as well as its developme nt and patter ns of phenotypic in tegrati on,through processes such as variation in genetic linkage between quantitative trait loci or between regulatory regions and their targets.Here we explore the relationship between chromosomal evolution and phenotypic integration by analyzing a well-known house mouse parapatric contact zone between a highly derived Robertsonian(Rb)race(2n=22)and populations with standard karyotype(2n=40).Populations with hybrid karyotypes are scattered throughout the hybrid zone connecting the two parental races.Using mandible shape data and geometric morphometries,we test the hypothesis that patter ns of in tegration progressively diverge from the"normal"integration pattern observed in the standard race as they accumulate Rb fusions.We find that the main pattern of integration observed between the posterior and anterior part of the mandible can be largely attributed to allometry.We find no support for a gradual increase in divergence from normal patterns of integration as fusions accumulate.Surprisingly,however,we find that the derived Rb race(2n=22)has a distinct allometric trajectory compared with the standard race.Our results suggest that either individual fusions disproportionately affect patterns of integration or that there are mechanisms which"purge"extreme variants in hybrids(e.g.reduced fitness of hybrid shape).
基金the National Science Foundation Graduate Research Fellowship,UW BiologyBurke Museumthe National Science Foundation Postdoctoral Research Fellowship in Biology(DBI-1812126).
文摘Selective pressures favor morphologies that are adapted to distinct ecologies,resulting in trait partition!ng among ecomorphotypes.However,the effects of these selective pressures vary across taxa,especially because morphology is also influenced by factors such as phylogeny,body size,and functional trade-offs.In this study,we examine how these factors impact functional diversification in mammals.It has been proposed that trait partitioning among mammalian ecomorphotypes is less pronoun ced at small body sizes due to biomecha nical,energetic,and environ mental factors that favor a"generalist"body plan,whereas larger taxa exhibit more substantial functional adaptations.We title this the Diverge nee Hypothesis(DH)because it predicts greater morphological divergence among ecomorphotypes at larger body sizes.We test DH by using phylogenetic comparative methods to examine the postcranial skeletons of 129 species of taxonomically diverse,small-tomedium-sized(<15 kg)mammals,which we categorize as either"tree-dwellers"or"ground-dwellers."In some analyses,the morphologies of ground-dwellers and tree-dwellers suggest greater between-group differentiation at larger sizes,providing some evidence for DH.However,this trend is n either particularly strong nor supported by all an alyses.In stead,a more pronoun ced patter n emerges that is distinct from the predictions of DH:within-group phenotypic disparity increases with body size in both ground-dwellers and tree-dwellers,driven by morphological outliers among"medium'-sized mammals.Thus,evolutionary increases in body size are more closely linked to increases in within-locomotor-group disparity tha n to in creases in betwee n-group disparity.We discuss biomechanical and ecological factors that may drive these evolutionary patter ns,and we emphasize the significant evolutionary influences of ecology and body size on phenotypic diversity.
