The correct explanation of why species, in evolutionary theory, are individuals and not classes is the cladistic species concept. The cladistic species concept defines species as the group of organisms between two speciation events, or between one speciation event and one extinction event, or (for living species) that are descended from a speciation event. It is a theoretical concept, and therefore has the virtue of distinguishing clearly the theoretical nature of species from the practical criteria by which species may be (...) recognized at any one time. Ecological or biological (reproductive) criteria may help in the practical recognition of species. Ecological and biological species concepts are also needed to explain why cladistic species exist as distinct lineages, and to explain what exactly takes place during a speciation event. The ecological and biological species concepts work only as sub-theories of the cladistic species concept and if taken by themselves independently of cladism they are liable to blunder. The biological species concept neither provides a better explanation of species indivudualism than the ecological species concept, nor, taken by itself, can the biological species concept even be reconciled with species individualism. Taking the individuality of species seriously requires subordinating the biological, to the cladistic, species concept. (shrink)

The world's foremost geneticist surveys the major developments in what is emerging as the most important single area of scientific inquiry in the twentieth century: biological theory of evolution.

The long-awaited revision of the industry standard on phylogenetics Since the publication of the first edition of this landmark volume more than twenty-five years ago, phylogenetic systematics has taken its place as the dominant paradigm of systematic biology. It has profoundly influenced the way scientists study evolution, and has seen many theoretical and technical advances as the field has continued to grow. It goes almost without saying that the next twenty-five years of phylogenetic research will prove as fascinating as the (...) first, with many exciting developments yet to come. This new edition of Phylogenetics captures the very essence of this rapidly evolving discipline. Written for the practicing systematist and phylogeneticist, it addresses both the philosophical and technical issues of the field, as well as surveys general practices in taxonomy. Major sections of the book deal with the nature of species and higher taxa, homology and characters, trees and tree graphs, and biogeography—the purpose being to develop biologically relevant species, character, tree, and biogeographic concepts that can be applied fruitfully to phylogenetics. The book then turns its focus to phylogenetic trees, including an in-depth guide to tree-building algorithms. Additional coverage includes: Parsimony and parsimony analysis Parametric phylogenetics including maximum likelihood and Bayesian approaches Phylogenetic classification Critiques of evolutionary taxonomy, phenetics, and transformed cladistics Specimen selection, field collecting, and curating Systematic publication and the rules of nomenclature Providing a thorough synthesis of the field, this important update to Phylogenetics is essential for students and researchers in the areas of evolutionary biology, molecular evolution, genetics and evolutionary genetics, paleontology, physical anthropology, and zoology. (shrink)

Argues for the primacy of the phylogenetic system as the general reference system in biology. This book, first published in 1966, generated significant controversy and opened possibilities for evolutionary biology.

The Development of Modern Taxonomy Taxonomy has a long history, going back to the ancient Greeks and to forerunners even less sophisticated in systematics. Our interest here is centered on modern taxonomy itself, and we shall largely ...

The goal of cladistic systematics is to discern sister-group relations (cladistic relations) by the methods of cladistic analysis and to represent them explicitly and unambiguously in cladograms and cladistic classifications. Cladists have selected cladistic relations to represent for two reasons: cladistic relations can be discerned with reasonable certainty by the methods of cladistic analysis and they can be represented with relative ease in cladograms and classifications. Cladists argue that features of phylogeny other than cladistic relations cannot be discerned with sufficient (...) certainty to warrant attempting to represent them in either cladograms or classifications and could not be represented if they could. I argue that a better alternative is to work toward improving methods of cladistic analysis (or else to supplement them with other methods) so that such features of phylogeny can be discerned and to devise methods of representation capable of representing them in both cladograms and classifications. However, cladograms and classifications cannot represent everything about phylogeny. It is better to represent one or two aspects of phylogeny explicitly and unambiguously than nothing at all. (shrink)

The goal of a phylogenetic species concept is to reveal the smallest units that are analysable by cladistic methods and interpretable as the result of phylogenctic history. We define species as the smallest aggregation of populations (sexual) or lineagcs (asexual) diagnosable by a unique combination of character states in comparable individuals (semaphoronts). A character state is an inherited attribute distributed among all comparable individuals (semaphoronts) of the same historical population, clade, or terminal lineage. This definition of species is character-based and (...) pattern oriented. Evolutionary explanations of phylogenetic species are consistent with contemporary explanations of processes of speciation, but require only the assumption of nested hierarchical pattern. We discuss the compatibility of the phylogenetic species concept with various biological needs for species and justify its use at the exclusion of alternative species concepts. (shrink)