TABLE 1.
Definition of concepts to describe units relevant for conservation management and evolutionary research. The list is not intended to be exhaustive, but to illustrate how ‘ecotype’ relates to other concepts and some of the similarities and discrepancies used in defining ecotypes in the literature. Below we attribute definitions to key publications and highlight taxa used as examples in the papers. We highlight the importance of ecological discreteness and adaptive genetic variation in the definition of various concepts, and whether these conditions appear focal, included, possible or not obvious. A proposed ecotype definition is highlighted in bold font
| Concept | Definition | Reference | Taxonomic unit(s) addressed | Ecological discreteness/Adaptive genetic variation |
|---|---|---|---|---|
| Subspecies | ‘Populations partway through the evolutionary process of divergence towards full speciation’ | Frankham et al. (2002) | Across taxa | Included/Included |
| Evolutionary Significant Unit (ESU) | ‘Populations possessing genetic attributes significant for present and future generations of the species in question’ | Ryder (1986) | Across taxa, examples from mammals (Somali black rhino; Diceros bicornis brucii) | Included/Included |
| Evolutionary Significant Unit (ESU) | Populations that are ‘(1) substantially reproductively isolated from other conspecific population units, and (2) represent an important component in the evolutionary legacy of the species’ | Waples (1991) | Fish (Pacific salmon, Oncorhynchus spp.) | Included/Included |
| Evolutionary Significant Unit (ESU) | ‘Clusters of organisms that are evolutionarily distinct and hence merit separate protection’ | Vogler and Desalle (1994) | Across taxa, examples from insects (Tiger beetles, Cicindela spp.) | Possible/Not obvious |
| Evolutionary Significant Unit (ESU) | Units that are ‘reciprocally monophyletic for mtDNA alleles and show significant divergence of allele frequencies at nuclear loci’ | Moritz (1994) | Across taxa | Possible/Possible |
| Evolutionary Significant Unit (ESU) | Units where ‘both genetic and ecological information should be used, with an emphasis placed on exchangeability instead of genetic distinctiveness’ for classification | Crandall et al. (2000), adapted from Templeton (1989) | Across taxa | Focal/Focal |
| Management Unit (MU) | ‘Populations with significant divergence of allele frequencies at nuclear or mitochondrial loci, regardless of the phylogenetic distinctiveness of the alleles’ | Moritz (1994) | Across taxa | Possible/Not obvious |
| Distinct Population Segment (DPS) | ‘A population (or group of populations) will be considered "distinct" (and hence a "species") for purposes of the ESA if it represents an evolutionarily significant unit (ESU [defined above]) of the biological species’ | Waples (1991) | Fish (Pacific salmon, Oncorhynchus spp.) | Included/Included |
| Designatable Unit (DU) | ‘Discrete and evolutionarily significant units of the taxonomic species, where “significant” means that the unit is important to the evolutionary legacy of the species as a whole and if lost would likely not be replaced through natural dispersion’ | COSEWIC (2018) | Across taxa | Included/Included |
| Ecotype | ‘Ecological unit to cover the product arising as a result of the genotypical response of an ecospecies to a particular habitat’ | Turesson (1922) | Plants (Antirrhinum rhinanthoides) | Focal/Focal |
| Ecotype | ‘An intraspecific product of environmental selection arising as a result of genotypic response to a particular habitat’ | Gregor and Watson (1961), citing Turesson (1922) | Across taxa | Focal/Focal |
| Ecotype | ‘Populations within a plant species that are genetically adapted to different ecological conditions, often of soil and climate’ | Frankham et al. (2002) | Across taxa | Focal/Focal |
| Ecotype | ‘Populations of the same species that evolved different demographic and behavioral adaptations to cope with specific ecological (biotic and abiotic) constraints’ | Courtois et al. (2003), adapted from Mallory and Hillis (1998) | Mammal (caribou; Rangifer tarandus) | Focal/Focal |
| Ecotype | ‘Distinct genotypes (or populations) within a species, resulting from adaptation to local environmental conditions; capable of interbreeding with other ecotypes or epitypes of the same species’ | Hufford and Mazer (2003) | Plants (across taxa) | Focal/Focal |
| Ecotype | ‘All the members of a species that are fitted to survive in a particular kind of environment within the total range of the species’ | Erickson and Navarrete‐Tindall (2004), citing Clausen et al. (1945) | Plants (focused on native ecotypes from the tallgrass prairie) | Focal/Possible |
| Ecotype | ‘Conspecific groups with similar ecological adaptations regardless of genealogical relationship’ | Cronin (2006) | Across taxa | Focal/Possible |
| Ecotype | ‘Life history variant’ | D’Amelio & Wilson (2008) | Fish (brook trout; Salvelinus fontinalis) | Focal/Possible |
| Ecotype | ‘A population or a group of populations adapted to a particular set of environmental conditions’ | COSEWIC (2011) | Mammal (caribou; Rangifer tarandus) | Focal/Possible |
| Ecotype | ‘Ecologically specialized lineages’ | Riesch et al. (2012) | Mammal (killer whale; Orcinus orca) | Focal/Possible |
| Ecotype | ‘Groups of populations, which are distinguished by a composite of variation in many traits and allele frequencies across loci over space… formed by multiple trait adaptations to many environmental variables that covary in space’ | Lowry (2012) | Across taxa | Focal/Possible |
| Ecotype | ‘Populations [that] show strong resource specializations based on consistent prey choice within stable, matrifocal social groups (pods), together with genetic and phenotypic differentiation’ | Moura et al. (2015), citing Hoelzel et al. (1998), Pitman and Ensor (2003), Hoelzel et al. (2007), and Morin et al. (2010) | Mammal (killer whale; Orcinus orca) | Focal/Possible |
| Ecotype | ‘Ecologically, genetically and geographically divergent lineages that might represent cryptic species’ | Bracamonte et al. (2015) | Fish (four Australian freshwater species) | Focal/Possible |
| Ecotype | ‘Populations of the same species which have evolved heritable physiological, morphological, behavioural or life history differences that are closely associated with environmental variation’ | Le Moan et al. (2016) | Fish (European anchovy; Engraulis encrasicolus) | Focal/Focal |
| Ecotype | ‘A plant population that originated in a specific area and has genetic adaptations to its environment’ | Altrichter et al. (2017) | Plants (focus on native plants and local ecotypes for ecological restoration) | Focal/Focal |
| Ecotype | ‘The resulting genetic divisions among wolf populations may reflect observed morphologic features related to diet (e.g. dentition, skull robustness and shape), vision (e.g. for open or closed terrain), metabolism, thermal regulation in response to ambient temperature, and locomotion (e.g. for migratory or territorial behavior) suggesting these genetic partitions may define ecological units (“ecotypes”)’ | Hendricks et al. (2019) | Mammal (grey wolf; Canis lupus) | Focal/Focal |