Ecotypes and the controversy over stages in the formation of new species

Abstract

Recent interest in the role of ecology in species formation has led to renewed discussion of the stages in the process of speciation. Although attempts to classify the stages in the process of species formation date back at least as far as Alfred Russel Wallace, one of the most intense debates on the subject occurred among botanists during the mid‐20th Century. The present review outlines the progression of the historical debate about stages in the evolution of species, which was instigated by the genecological classification scheme of Göte Turesson in the 1920s, championed in the mid‐century by Jens Clausen, and then brought under harsh scrutiny by many in the 1960s and 1970s. At the heart of the controversy is the question of whether speciation occurs rapidly on a local scale or gradually through the formation of geographically widespread ecotypes that evolve as precursors to species. A corollary to this debate is the question of whether speciation is reversible and, if so, how does it become irreversible? A third wave of interest in stages in the process of speciation is currently underway, thus making a modern historical narrative of the debate important. Both contemporary and past evolutionary biologists have argued that viewing speciation as being composed of stages can free researchers from concerns over species definitions and focus attention on the mechanisms involved in the process. How speciation becomes irreversible and whether ecogeographically isolated ecotypes are integral to this process remain as important unresolved issues. © 2012 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, 106, 241–257.

The role of ecotypic variation and the environment on biomass and nitrogen in a dominant prairie grass

“…E-mail: sgbaer@siu.edu where to source propagules for ecological restoration able to withstand more variable conditions. Ecotypes share a collection of morphological and physiological traits that evolved from a regional selection pressure (Lowry 2012). Climate was an important driver in development of grassland in the central United States (Axelrod 1985) and a plausible regional selection pressure for the evolution of ecotypes across environmental gradients in this ecosystem.…”

Expression Quantitative Trait Locus Mapping across Water Availability Environments Reveals Contrasting Associations with Genomic Features in Arabidopsis

“…Within plant species, soil water availability has long been known to be a major factor driving the evolution of growth rate, flowering time, and life-history transitions (Clausen, 1951;Stebbins, 1952;Roux et al, 2006;Des Marais and Juenger, 2010;Lowry, 2012). Understanding genetic variation in response to water availability is thus of great importance to plant evolutionary biology, improvement of crop performance, and predicting how species will respond to climate change (Jump and Penuelas, 2005;Oliver et al, 2009;Chown et al, 2010).…”

No evidence of intrinsic reproductive isolation between two reciprocally non-monophyletic, ecologically differentiated mountain plants at an early stage of speciation

“…During speciation, divergence in phenotypic traits, genetic constraints, and reproductive isolation varies quantitatively; speciation thus represents a continuum of divergence, starting from continuous variation to distinct species pairs at the final stage (Nosil 2012). Dependent on the extent and stability of reproductive isolation, incipient phenotypic differentiation can lead to the formation of distinct phylogenetic lineages, but this is not necessarily the case (Lowry 2012). Intermediate stages in ecological speciation involve ecotypes (Lowry 2012), i.e.…”

“…Dependent on the extent and stability of reproductive isolation, incipient phenotypic differentiation can lead to the formation of distinct phylogenetic lineages, but this is not necessarily the case (Lowry 2012). Intermediate stages in ecological speciation involve ecotypes (Lowry 2012), i.e. groups of populations within one species differentiated due to adaptation to local environmental conditions, which are frequently still interfertile (Hufford and Mazer 2003) and result from a combination of heritable and non-heritable traits (Pfennig et al 2010;Bonduriansky et al 2012).…”