Biodiversity and the Species Concept—Lineages are not Enough

Abstract

The nature and definition of species continue to be matters of debate. Current views of species often focus on their nature as lineages-maximal reproductive communities through time. Whereas many authors point to the Evolutionary Species Concept as optimal, in its original form it stressed the ecological role of species as well as their history as lineages, but most recent authors have ignored the role aspect of the concept, making it difficult to apply unambiguously in a time-extended way. This trend has been exacerbated by the application of methods and concepts emphasizing the notion of monophyly, originally applied only at higher levels, to the level of individuals, as well as by the current emphasis on molecular data. Hence, some current authors recognize units that are no more than probable exclusive lineages as species. We argue that biodiversity is inherently a phenotypic concept and that role, as manifested in the organismal extended phenotype, is a necessary component of the species concept. Viewing species as historically connected populations with unique role brings together the temporal and phenotypic natures of species, providing a clear way to view species both in a time-limited and time-extended way. Doing so alleviates perceived issues with "paraphyletic species" and returns the focus of species to units that are most relevant for biodiversity.

Salmo macrostigma(Teleostei, Salmonidae): Nothing more than a brown trout (S. trutta) lineage?

“…These authors recommend the use of concepts such as ESUs (considering the spatial distribution of the genetic diversity; Almodóvar et al, 2006;Moritz, 1994), or alternatives (e.g. operational conservation units or OCU, reflecting interaction with socio-economic issues; Dodson et al, 1998;Machordom et al, 2000), which highlight intraspecific diversity without promoting taxonomic inflation and the arbitrary concept of subspecies (Freudenstein et al, 2017). The North African lineage described in this study and probably more local groups within this lineage certainly must be managed in a more adaptive and integrated evolutionary framework, such as with ESUs, to be more effective (Fraser & Bernatchez, 2001).…”

The classification of asexual organisms: Old myths, new facts, and a novel pluralistic approach

“…Only taxa with a more stable to obligate apomixis would fall into the category of an evolutionary species. A second problem is the lack of criteria for species delimitation and any kind of subdivisions -a problem that arises already for sexual species, as each and every population can be defined as a lineage (Freudenstein & al., 2017). In asexual taxa each and every clone or genotype can establish an ancestor-descendant lineage.…”

“…From the conceptual side, most modern authors agree that species are lineages in the sense of ancestor-descendant series (De Queiroz, 2007;Sukumaran & Knowles, 2017). Lineages should have an evolutionary role to be accepted as species (Freudenstein & al., 2017). Lineages per se can be maintained both by sexual and asexual reproduction.…”

“…Traditional taxonomists tried to recognize the enormous phenotypic diversity of asexual lineages by describing hundreds and thousands distinguishable morphotypes as species. The need to recognize phenotypic diversity -in the sense of an evolutionary role of a lineage -was just recently emphasized (Freudenstein & al., 2017). However, as I will discuss below, a distinguishable phenotype is not necessarily a reliable indicator for an asexual lineage.…”

Glomeromycotina: what is a species and why should we care?

“…This criterion embraces the idea of Freudenstein et al . () that considering the species ‘role’ in the environment needs to be part of the species recognition process.…”