Species and Lineages

Jun Otsuka (Kyoto University)
This paper argues that biological species should be construed as abstract models, rather than biological or even tangible entities. Various (phenetic, cladistic, biological etc.) species concepts are defined as set-theoretic models of formal theories, and their logical connections are illustrated. In this view organisms relate to a species not as instantiations, members, or mereological parts, but rather as phenomena to be represented by the model/species. This sheds new light on the long-standing problems of species and suggests their connection to broader philosophical topics such as model selection, scientific representation, and scientific realism.

Justin Bzovy (MacEwan University)
Species pluralists argue that there is more than one legitimate species concept, but fail to fully explore the ways concepts interact if we accept pluralism. Since different concepts often cross-classify, most pluralists stress the separation of legitimate species concepts, rather than the extent to which they might be integrated. The aim of this paper is to put species pluralism into practice by showing how a toolbox account of species concepts can make sense of two seemingly incompatible aims: local classificatory consilience and cross-classification. As this paper will show, systematists aim at achieving a degree of local classificatory consilience. However, this aim is not always achieved, but is a "meta-heuristic" that provides insight into the research phenomena even when local classificatory consilience fails (O'Malley 2013). When researchers fail to achieve local classificatory consilience, e.g., cryptic species (species that are morphologically indistinguishable, but cannot interbreed), the use of different species concepts can uncover details about the operating speciation mechanisms. By treating local classificatory consilience as a meta-heuristic, my toolbox pluralism explains why species concepts are flexible: sometimes cross-classifying, and sometimes aligning. In order to highlight this flexibility, I focus on species discovery in the large-spored Metschnikowia clade and related genera.

Beckett Sterner (Arizona State University)
Evolutionary conceptions of species place special weight on each species having dynamic independence as a unit of evolution. However, the idea that species have their own historical fates, tendencies, or roles has resisted systematic analysis. Growing evidence from population genomics shows that many paradigm species regularly engage in hybridization. How can species be defined in terms of independent evolutionary identities if their genomes are dynamically coupled through lateral exchange? I introduce the concept of a "composite lineage" to distinguish species and subspecies based on the proportion of a group's heritable traits that are uncoupled from reproductive exchange.

Celso Neto (University of Calgary)
This paper defends lineage pluralism; the view that biological lineages are not a single, unified type of entity. I analyze aspects of evolutionary theory, phylogenetics, and developmental biology to show that these areas appeal to distinct notions of lineage. Based on this information, I formulate three arguments for lineage pluralism. These arguments undercut the main motivations for lineage monism, namely, the view that biological lineages are a single, unified type of entity. Though this view is rarely made explicit, it is often assumed in philosophy and biology. Hence, this paper sheds light on the implicit monistic assumption, and shows why lineage pluralism should be adopted instead.