The sequential order of genes in animal mitochondrial DNA tends to be conserved at high taxonomic levels. Consequently, when mitochondrial gene rearrangements occur, they can provide compelling markers of ancient phylogenetic history (see reviews in Boore, Daehler, and Brown [1999], Saccone et al. [1999], and references therein). Such gene order characters have proven particularly useful for resolving deep-branching events characterizing superphyla, phyla, and classes, a scale over which nucleotide sequence analysis has often proven problematic (e.g., Smith et al. 1993; Boore and Brown 1994a, 1998, 2000; Boore et al. 1995; Boore, Lavrov, and Brown 1998; Stechmann and Schlegel 1999). Most frequently, these rearrangements are associated with the movement of tRNA genes which, based on their stem-and-loop structure, may also have an underlying role as mobilizing elements within the mitochondrial genome (Moritz and Brown 1987; Stanton et al. 1994; Saccone et al. 1999). Gene rearrangements involving ribosomal and protein-encoding genes (hereinafter referred to as ‘‘major’’ genes), however, are much rarer. Here we report a mitochondrial gene rearrangement involving major genes that has occurred within a genus of marine vermetid gastropods that diversified within the Cenozoic. Based on data from the fossil record and an independent molecular calibration, we estimate that this gene order change may have occurred within the last 38–48 Myr, making this a very recent major gene order rearrangement. This finding thus has important implications for the use of gene order characters in metazoan phylogeny, in terms of both understanding the mechanism of gene order rearrangements and determining the taxonomic level and timescale over which these major rearrangements may prove useful. The family Vermetidae comprises seven genera with ;100 extant species of sessile, uncoiled, suspension-feeding gastropods found in shallow marine waters in warm temperate to tropical latitudes throughout the world (Keen 1961; Morton 1965; unpublished data). Based on our current understanding of gastropod evolution, vermetid gastropods radiated from a basal caenogastropod stock sometime in the early Cenozoic (Keen 1961; unpublished data). As part of a study to investi-

Timothy A. Rawlings

Timothy M. Collins

Rüdiger Bieler

Molecular Biology and Evolution

MOLECULAR BIOLOGY AND EVOLUTION 在分子（包括基因组学）和进化生物学的界面发表研究。我们考虑包含人口、分类、功能和表型组织各个层次的模式、过程和预测的手稿。除了具有更广泛范围和影响的基本发现外，我们还对出版新的和改进的方法、资源、技术和理论感兴趣，这些方法、资源、技术和理论将显着推进进化研究。我们还发表了对基因组进化最新发展的平衡评论和前瞻性观点，提出了分子进化领域或应用的未来方向。

The journal "Molecular Biology and Evolution" focuses on the interface of molecular biology and evolutionary biology, publishing research in this area. We welcome manuscripts that address patterns, processes, and predictions across various levels, including population, taxonomy, function, and phenotype. In addition to fundamental findings with broad implications, we are also interested in publishing new and improved methods, resources, technologies, and theories that significantly advance evolutionary research. Furthermore, we publish balanced reviews and forward-looking perspectives on the latest developments in genome evolution, proposing future directions for the field of molecular evolution and its applications.

《Molecular Biology and Evolution》期刊专注于分子生物学与进化生物学的交叉领域，发表相关研究成果。我们欢迎涉及种群、分类、功能和表型等多个层面的模式、过程和预测的手稿。除了具有广泛影响的基础研究发现外，我们也对新的和改进的方法、资源、技术和理论感兴趣，这些内容将显著推动进化研究的发展。此外，我们还发表关于基因组进化最新进展的综合评论和前瞻性观点，探讨分子进化领域及其应用的未来方向。

A Major Mitochondrial Gene Rearrangement Among Closely Related Species

A mitochondrial gene rearrangement involving major genes that has occurred within a genus of marine vermetid gastropods that diversified within the Cenozoic is reported, estimating that this gene order change may have occurred within the last 38–48 Myr.

Category	Quartile
生物学	1
生物学, 遗传学	1
生物学, 生化与分子生物学	2
生物学, 进化生物学	2

A Major Mitochondrial Gene Rearrangement Among Closely Related Species

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GENETICS & HEREDITY	1