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Hohangengenoloigy war g omcs anditsassociatedmoleculartools c i bi in the 21st century? Of course, this is impossible to answer in the space of a single article, because genomics has affected so many biological subdisciplinesin so many ways. Instead, I present here a microcosm of these changes, focusing on a small sliver of the biological layer cake, both conceptually and organismally. I will discuss the impact of genomicson thesystematics(phylogenyandspecies limits) of two groups of organisms that are familiarto every- one,reptiles (snakes, lizards,turtles,tuatara,crocodili a ns)and amphibians (frogs, toads, salamanders,caecilians). The study of these two groups is called herpetology.I will address how genomics is changing the practice of herpetological system- atics, what we have learned from these new data so far, and what the future might hold. Although systematics may seem like an abstruse biologi- cal subdiscipline to some, it is important to remember that most biological research depends on systematics at some level. For example, it is through systematics that species are discovered, described, and given scientificnames.The study of phylogeny tellsus fundamentally what organisms are (e.g., a dolphin is more closely relatedto a human than to a tuna), and allows us to make inferencesabout how their traits have evolved over time. A brief history of molecular data in herpetological systematics Tounderstandhow these new sources of molecular data are changing herpetological systematics, we need a historical context.Beforethe widespread useof DNA (deoxyribonucleic acid) sequencing, most molecular studies utilized data from allozymes and albumin immunological distances. Allozyme data typically consist of the frequencies of different alleles at a given enzyme locus, where these alleles are detected on the basis of their different mobilities in a starch or acetate gel. In the 1980s, allozyme data became widely used in phyloge- netic studies of closely related reptile and amphibian species (e.g., Hillis et al. 1983). Allozyme studies also led to the dis- covery of new species that were previously unrecognized becauseof their morphological similarity (e.g.,Highton et al. 1989). However, these data are of limited use for higher-level phylogeny,mostly because distantly related speciestend tohave no alleles in common. Allozymes are also problematic in that the underlying data (mobility of alleles) are entirely rel- ative,and so raw data from differentstudies generally cannot be directly compared or combined. Albumin immunological data were also used in manyher- petological studies in the 1970s and 1980s (e.g., Maxson and Wilson 1974).Immunological data are based on overall sim- ilarity between molecules rather than homology of individ- ual characters. Perhaps because of this, immunological data and the resultingphylogenies havenot been widely embraced in herpetology.These data also sufferfrom thesameproblems of allozyme data, in terms of being entirely relative and dif- ficult to apply over larger phylogenetic scales. John J. Wiens (e-mail: wiensj@life.bio.sunysb.edu)is with the Department of Ecology and Evolution at Stony Brook University in Stony Brook, New York. �� 2008 American Institute of Biological Sciences. Systematics and Herpetology in the Age of Genomics JOHN J. WIENS How is organismal biology changing in the era of genomics? Here, I discuss one example, the changes and trends in the systematics of reptiles and amphibians. The polymerase chain reaction, automated sequencing, and genomic tools now make it possible to apply a vast number of molecular characters to questions of phylogeny and species limits. At higher taxonomic levels, recent studies using these data have revealed some unexpected relationships, but also strong support for many traditionally recognized groups. At lower levels, molecular studies suggest that numerous species have been hidden by misleading taxonomy and morphological conservatism. However, the computational tools for analyzing multilocus data for phylogenetics and species delimitation are in need of further development, including greater integration with population genetics. Given current trends, much of reptile and amphibian phylogeny may soon be resolved. Although opportunities for tree-making by future systematists may shrink, opportunities for using phylogenies to address evolutionary and ecological questions should blossom. Keywords: amphibians, genomics, phylogeny, reptiles, systematics www.biosciencemag.org April 2008 / Vol. 58 No. 4 ��� BioScience 297 21st Century Directions in Biology