“…Most extant genera of caviomorph and phiomorph rodents can also be traced to divergences that took place during the Miocene (Patterson and Upham 2014, Upham and Patterson In press). The Middle Miocene origin for chipmunk lineages that is suggested by both fossils and molecular dating falls comfortably within the range typically associated with genus-level divergence (Holt and Jønsson 2014).…”
Abstract:The chipmunks are a Holarctic group of ground squirrels currently allocated to the genus Tamias within the tribe Marmotini (Rodentia: Sciuridae). Cranial, postcranial, and genital morphology, cytogenetics, and genetics each separate them into three distinctive and monophyletic lineages now treated as subgenera. These groups are found in eastern North America, western North America, and Asia, respectively. However, available genetic data (mainly from mitochondrial cytochrome b) demonstrate that the chipmunk lineages diverged early in the evolution of the Marmotini, well before various widely accepted genera of marmotine ground squirrels. Comparisons of genetic distances also indicate that the chipmunk lineages are as or more distinctive from one another as are most ground squirrel genera. Chipmunk fossils were present in the late Oligocene of North America and shortly afterwards in Asia, prior to the main radiation of Holarctic ground squirrels. Because they are coordinate in morphological, genetic, and chronologic terms with ground squirrel genera, the three chipmunk lineages should be recognized as three distinct genera, namely, Tamias Illiger, 1811, Eutamias Trouessart, 1880, and Neotamias A. H. Howell, 1929. Each is unambiguously diagnosable on the basis of cranial, post-cranial, and external morphology.
“…Most extant genera of caviomorph and phiomorph rodents can also be traced to divergences that took place during the Miocene (Patterson and Upham 2014, Upham and Patterson In press). The Middle Miocene origin for chipmunk lineages that is suggested by both fossils and molecular dating falls comfortably within the range typically associated with genus-level divergence (Holt and Jønsson 2014).…”
Abstract:The chipmunks are a Holarctic group of ground squirrels currently allocated to the genus Tamias within the tribe Marmotini (Rodentia: Sciuridae). Cranial, postcranial, and genital morphology, cytogenetics, and genetics each separate them into three distinctive and monophyletic lineages now treated as subgenera. These groups are found in eastern North America, western North America, and Asia, respectively. However, available genetic data (mainly from mitochondrial cytochrome b) demonstrate that the chipmunk lineages diverged early in the evolution of the Marmotini, well before various widely accepted genera of marmotine ground squirrels. Comparisons of genetic distances also indicate that the chipmunk lineages are as or more distinctive from one another as are most ground squirrel genera. Chipmunk fossils were present in the late Oligocene of North America and shortly afterwards in Asia, prior to the main radiation of Holarctic ground squirrels. Because they are coordinate in morphological, genetic, and chronologic terms with ground squirrel genera, the three chipmunk lineages should be recognized as three distinct genera, namely, Tamias Illiger, 1811, Eutamias Trouessart, 1880, and Neotamias A. H. Howell, 1929. Each is unambiguously diagnosable on the basis of cranial, post-cranial, and external morphology.
“…1). As has been previously shown in different animal groups 13, 20 , the ranges of taxon ages overlapped between the genus and family ranks, making some of these taxonomic units not comparable even within the same family or order.Figure 1Distribution of crown ages of currently accepted genera (blue) and families (red) in the studied data set (Parmeliaceae, Ascomycota). The median for both ranks indicated by a dashed line.
…”
Section: Temporal Inconsistency At the Same Taxonomic Ranksmentioning
confidence: 84%
“…To make taxonomic ranks at supraspecific level more consistent and increase meaningful comparability among higher taxonomic ranks, the use of a standardized time of divergence has been suggested as a universal yardstick for the assignment of ranks 8, 11–13, 20–22 . This means that groups of organisms are given the same rank if they originated in the standardized geological time period.…”
Section: Introductionmentioning
confidence: 99%
“…To this end, we propose an extension of Holt and Jønsson’s Temporal Error Score 20 to find an objective cut-off for each taxonomic rank, using the information from the current classification. To illustrate the utility of this temporal banding approach, we apply this modified approach to the most comprehensive phylogeny of the hyperdiverse lichen-forming fungal family Parmeliaceae.…”
Section: Introductionmentioning
confidence: 99%
“…To illustrate the utility of this temporal banding approach, we apply this modified approach to the most comprehensive phylogeny of the hyperdiverse lichen-forming fungal family Parmeliaceae. We briefly describe the temporal approach with Temporal Error Score 20 and its computational limitations. Finally, we illustrate how the Temporal Error Score to can be used to find the time point with the minimal error to modify the current classification.…”
Comparable taxonomic ranks within clades can facilitate more consistent classifications and objective comparisons among taxa. Here we use a temporal approach to identify taxonomic ranks. This is an extension of the temporal banding approach including a Temporal Error Score that finds an objective cut-off for each taxonomic rank using information for the current classification. We illustrate this method using a data set of the lichenized fungal family Parmeliaceae. To assess its performance, we simulated the effect of taxon sampling and compared our method with the other temporal banding method. For our sampled phylogeny, 11 of the 12 included families remained intact and 55 genera were confirmed, whereas 32 genera were lumped and 15 genera were split. Taxon sampling impacted the method at the genus level, whereas yielded only insignificant changes at the family level. The other available temporal approach also gives a similar cutoff point to our method. Our approach to identify taxonomic ranks enables taxonomists to revise and propose classifications on an objective basis, changing ranks of clades only when inconsistent with most taxa in a phylogenetic tree. An R script to find the time point with the minimal temporal error is provided.
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