About Names and Taxa
Sources of the Names
Names cited in this website originated as part of a "data dump" for the Violaceae family, provided to Harvey Ballard from the IPNI staff at the Royal Botanic Garden in Kew, London, England in 2004. New names published since then, as well as others that have come to light, have been added. All names were incorporated into a BRAHMS (Botanical Research and Herbarium Management System) database and then split into two databases, with one representing North America north of Mexico and the other, all other regions of the world. The International Plant Names Index (www.ipni.org, under the "Links" menu) provided internationally accepted abbreviations for taxonomic authorities and literature citations for publications of scientific names.
Accepted Names and Taxa
The Violaceae as named, circumscribed and characterized in two submitted regional treatments to be published or made available in the near future formed much of the basis for this website, although a great deal of additional research was necessary. One treatment, the Violaceae of northeastern North America, was prepared for Rob Naczi's "New Gleason and Cronquist" manual of the northeastern United States and Canada. The second treatment, assembled with Alan Weakley and Bruce Sorrie, will soon be posted as part of the newest version of Weakley's "Flora of the southeastern United States". Additional taxa occurring west to the Rocky Mountains and northwestward to the western Arctic have been added to complete the taxon coverage. Only those names established with confidence as the earliest available and validly published have been used as accepted names of taxa, and only names the identify of which has been established with little to no doubt (in most cases, by evaluating typifications) have been included as synonyms. Virtually all accepted names and all of the synonyms have been studied and typifications have been confirmed (see "Typifications" below). For some of the uncertain names, literature references with protologues have been obtained and type material has been identified but not critically studied; research on those will be accomplished in the near future.
Most accepted taxa discussed in this website are treated at the rank of species, including several undescribed species, as a consequence of our research approach (see "Species Concepts and Taxon Delineation in Violets" below, and "Integrative Taxonomy" in the "Our Research" dropdown menu). We also include information on several undescribed anomalous variants that belong to species complexes and do not appear (based on sparse evidence), to match any taxa we recognize. We are currently studying these, and we anticipate that with comprehensive evidence, some or all of these will prove to be worthy of recognition.
For each accepted taxon, I have provided hopefully relevant, useful comments concerning previous treatments of the taxon, interesting observations by violet specialists and authors of state or regional floras; identification or nomenclatural issues; distinctions from similar-looking taxa (although I assume the reader would consult the keys for diagnostic features in identifying violets); and other interesting observations of taxonomy, ecology, or geography. I have not attempted to consult checklists, atlases, "wildflower" guides, county-level florulas, or floras of municipal, state or national parks (although I will investigate literature on national parks in the region of concern in the near future). I have thus far consulted publications by Brainerd (1921b, 1924), Baird (1942), Fernald (1950), Henry (1953a), Russell (1955c), Jørgensen et al. (1958), Alexander (1963), Russell (1965), Lévesque and Dansereau (1966), Scoggan (1978), Strausbaugh and Core (1978), Swink and Wilhelm (1979), Ballard (1995, 2000, 2013), McKinney (1992), Gil-ad (1995, 1997, 1998), McKinney and Russell (2002), Haines et al. (2011), Voss and Reznicek (2012), Weakley et al. (2012), and Little and McKinney (2015). Additional literature will be consulted in the near future will include the work of Klaber (1976), Great Plains Flora Association (1986), Diggs et al. (1999), and several other state floras in our region published since Fernald's 1950 manual. I am relying on James Smith's (2019) valuable and comprehensive bibliography of North American floras, manuals and checklists as a guide to identify additional literature.
Species Concepts and Taxon Delineation in Violets
Species concepts have been under discussion, or in hot debate, for more than a century. Mishler and Donoghue (1982), Sluys (1991), Baum and Donoghue (1993, 1995), Luckow (1995), Olmstead (1995), Meeus et al. (2003), Aleixo (2007), Knapp (2008) and Haveman (2013) reviewed the two dozen-plus species concepts from theoretical and practical perspectives. Slobodchikoff (1976), Mishler and Donoghue (1982), Mishler (1985), Olmstead (1995), Zink and McKitrick (1995), Collar (1996), Wheeler and Meier (2000), Fraser and Bernatchez (2001), Pratt and Pratt (2001), Garnett and Christidis (2007), Vetter and Storch (2009), Rojas-Soto et al. (2010), Braby et al. (2012), and Frankham et al. (2012) examined the impacts of different taxon delineations and species concepts on biodiversity recognition and conservation. Mayden (1997), de Queiroz (2005, 2007), and Naomi (2011) reexamined theoretical and practical aspects of species concepts, with the aim of understanding the underpinnings common to all of them and devising a more fundamental and unified approach to species delimitation. The General Lineage or Unified Species Concept of de Queiroz in particular reflects the understanding of many taxonomists and biologists–that organisms on the landscape represent aggregates of populations comprising distinct evolutionary units one may call a species, with individuals within a species connected by realized or potential gene flow and an ancestry of common descent, and behaving through space and time in an interrelated pattern represented by metapopulation dynamics. de Queiroz proposed that the overarching theme common to all species concepts is a species as a separately evolving metapopulation. To "diagnose" or delineate a species, one must use various types of evidence, and former individual species concepts then become data sources from which one evaluates a set of populations to determine whether or not those populations meet the definition of a species. de Queiroz pointed out that each individual line of evidence will likely give a different viewpoint on how differentiated the set of populations under study is in comparison to its sister taxon (in a simple taxon-pair diverging from the most recent common ancestor), or from related sets of populations. de Queiroz noted that any line of evidence that provides support for a set of populations as a species under the Unified Species Concept is sufficient but argued that more and diverse evidence is better. It is worth noting that the unified species concept allows for any speciation mechanism to produce evolutionary species, including hybrid origin.
It has been customary until relatively recently that plant taxonomists (and violet specialists) did not explicitly state (or, perhaps, did perceive it necessary to state) which species concept(s) they were utilizing to detect, delineate and describe species. Generally, they (and we) have utilized the morphological species concept, at least in the initial approach to detect a set of plants or populations to examine further. Norman Russell (1953, 1955c, 1958a, 1958b, 1959, 1961, and 1965) relied largely on an implicit morphological species concept using predominately largely vegetative traits to delimit taxa. He also examined photoperiodic responses (Russell 1960), variation patterns in several violet species (1954b, 1955b, 1956b, 1956c, Russell and Graham 1958, and Russell and Crosswhite 1963), and hybridization events (1952, 1954a, 1955a, 1956a, Russell and Cooperrider 1955a, 1955b, Russell and Bowen 1960, Russell and Risser Jr. 1960) to delineate taxa, although he did not avail himself of other data such as relative reproductive fitness or isolation mechanisms. Landon McKinney (1977, 1992, McKinney and Blum 1978, 1981, McKinney and Russell 2002) used an implicit morphological species concept that was virtually exclusively confined to vegetative characteristics. Little and McKinney (2015) also employed an implicit morphological species concept but consulted additional evidence from the literature in determining the limits and ranks of many taxa. A few other specialists have taken steps beyond morphology, invoking other concepts to reassess initially morphologically defined taxa. Ezra Brainerd was the first to exploid morphological characteristics of reproductive structures and the behavior or hybrids as it related to the parental taxa. He reported extensively on observations of relative fertility (or sterility) of parental taxa and their hybrids, including any hybrid progeny through the F3 and F4 generations, documenting universal cessation of chasmogamous reproduction, sterility (with no viable seeds) of hybrids of all lineages in North America but the Boreali-Americanae, and sterility or reduced seed output in cleistogamous reproduction in de novo hybrids of the Boreali-Americanae. In cultivating nearly every North American violet in a common garden over a 20-plus year period, he also documented genetically fixed differences among taxa across the growing season and reported on patterns of natural variability in the taxa he recognized (Brainerd 1904a, 1904b, 1905, 1906a, 1906b, 1906c, 1907a, 1907b, 1909, 1910a, 1910b, 1911a, 1911b, 1911c, 1912, 1913a, 1913c, 1913d, 1917a, 1917b, 1921b, 1924). Thus, he implicitly employed a morphological species concept coupled with a modified biological species concept, with elements of a genealogical species concept. In their taxonomic scrutiny of western violets, in which polyploid evolution has been far more active than in eastern North American members, Milo Baker and Jens Clausen (Baker 1935, 1936, 1940, 1949a, 1949b, 1949c, 1953, 1957, Clausen 1964) and Garrett Davidse (1968, 1976) employed both morphological and genetic species concepts in detecting and delineating taxa and recognizing parentage of allopolyploid species. Fabijan et al. (1988) used morphology, biochemistry, morphometric analysis, and chromosome numbers (therefore applying a pluralistic approach involving morphological, biochemical, phenetic and genetic species concepts) to delineate taxa in the primarily western Nuttallianae group of caulescent yellow-flowered violets. In his dissertation research with the Acaulescent Blue violets of Viola subsect. Boreali-Americanae, Nir Gil-ad examined macromorphological features in a more exhaustive and explicit fashion than had ever been accomplished before (Gil-ad 1995, 1997, 1998). He utilized presumably conserved micromorphological features of lateral petal trichomes and seed coats way as a proxy for genetic evidence to delimit taxa and infer potential hybrids or hybrid derivatives. His working hypothesis was that all taxa could be hybrid derivatives, and he sought evidence to reject this hypothesis in a quest to identify and circumscribe orthospecies. He excluded all taxa interpreted as expressing intermediate or non-unique features as hybrids or hybrid derivatives, admitting that this would also exclude taxa now behaving as species that were potentially "stabilized" and of ancient hybrid origin, as well as de novo hybrids. He explicitly employed a modified phylogenetic diagnosability criterion (in the absence of population-level phylogenetic analysis), to which he added the further requirement that at least one unique reproductive feature and unique micromorphological features in lateral petal trichomes and/or seed coats must be present to consider a taxon an orthospecies. He was the first specialist to utilize a phylogenetic species concept (or, rather, a criterion) to evaluate and delineate taxa. Gil-ad provided the first comprehensive descriptions of accepted orthospecies and some of the first methodical and critical typifications for the Boreali-Americanae. Ballard (1985, 1987, 1990, 1995, 2000, 2013, Ballard and Gawler 1994, McCauley and Ballard 2013) adhered closely to Russell's (1965) taxonomic concepts and, early on, employed a morphological species concept alone in recognizing non-hybrid taxa. With hybrids, he alluded to observed reproductive behavior, including pollen stainability or capsule and seed production (Ballard 1990a, 1990b, 1993). He later added morphometric analysis of morphological and other data (Ballard and Wujek 1994, Ballard et al. 2001), relying heavily on the phenetic species concept. His thesis on Rostrate violets (Ballard 1992) included micromorphology of styles and leaf surfaces, morphometrics of macromorphological data, and analysis of flavonoid chromatographic results (a more pluralistic approach to taxon delineation).
Beginning in 2012, my students and I began employing a broader, integrative taxonomic approach with the unified species concept as the most expansive and objective evolutionary species concept for detecting and delineating species, infraspecific taxa and hybrids. In applying the unified species concept to violets as an operational "filter" on the empirical evidence we generated, a number of practical points became obvious. First, in order for a population or taxon under study to conform to a metapopulation, it must have the ability to create genetically and phenotypically similar progeny. This excludes sterile de novo hybrids from consideration, which are the only type of hybrid produced among species in the caulescent groups of our region and among the acaulescent whites (subsect. Stolonosae). Also excluded are de novo hybrids in the first several (or many?) hybrid generations in the taxonomically challenging stemless blues (subsect. Boreali-Americanae), because they do not reproduce by chasmogamous means, and cleistogamous capsules of the hybrids–when not fully sterile–produce recombinant progeny expressing different combinations of phenotypic traits underlain by different genotype combinations of the parental species. Thus, they do not conform to the expectations of a single species metapopulation. A species with a hybrid origin in the more distant past, that had become genetically and phenotypically stabilized, could conform to the unified species concept. Trivial population-level allelic forms, as well as minor regional variants, could potentially be shown to belong to a single separately evolving metapopulation through careful morphological analysis, observations of pollinator and reproductive behaviors, or other means, although genetic evidence would be ideal. In comparing sets of more divergent populations, examining within- and among-population variation in individual phenotypic traits and making comparisons of traits and their variation patterns in similar sets of populations would provide some evidence that one is dealing with a single distinct metapopulation, while evidence from ecological niche, phenology, and other non-genetic sources, perhaps aided by statistical tests, would provide additional evidence to delineate separately evolving (or differentiated) sets of populations. Genetic data (e.g., from microsatellite loci or another population-level multi-locus approach, and perhaps plastid markers) would provide important corroborative evidence to test for potential or realized gene flow representing coalescent relationships among populations of the study group, versus hybridization (whether recent or ancient). A flurry of contributed conference talks and posters have resulted from this new approach and species concept (Ballard 2016, 2017, 2018, 2019a, 2019b, Robertson and Ballard 2014, Zink and Ballard 2014, Zumwalde and Ballard 2014, Ballard et al. 2015, Benson and Ballard 2015, Greff and Ballard 2018, Hastings and Ballard 2018, Burwell and Ballard 2019, Chilson and Ballard 2019), as well as completed Masters theses (Zumwalde 2015, Hastings 2018). Several manuscripts are nearing completion for submission that present some of our data on newly detected undescribed species. A recent example in which an undescribed Palustres violet was detected initially from molecular phylogenetic data (namely, single-copy nuclear genes), and further delineated using morphological traits, was published by Blaxland et al. (2018). In our studies, we have found that detailed morphological analysis, ecological characterization, and examination of reproductive behavior and hybrids with other taxa are minimally sufficient to confidently detect and delineate uniform sets of populations as species under the unified species concept. Sets of living plants from several to many populations over the range of a taxon under study, grown in a common garden, are critical to determining genetically fixed differences among similar sets of populations, especially during different parts of the growing season (chasmogamous flower and cleistogamous fruit in particular). Following Gil-ad's approach, we scrutinize and record quantitative and qualitative macromorphological traits across the plant body and micromorphological features of lateral petal trichomes and seed coats; analyze site and soil variables to characterize the ecological niche; record mature seed vs. abortive ovule number and image seeds from formerly bagged cleistogamous capsules after natural dehiscence to document reproductive behavior in the putative species and in any hybrids with other taxa. In certain instances we find funds to generate molecular marker data to evaluate the extent of genetic differentiation (recently we have employed microsatellite loci identified using shotgun genome sequencing, but we are now exploring double-digest genotying-by-sequencing). We delineate taxa as narrowly as the evidence drives us to do. We place no requirements on the number or type of characteristics or evidence required to support a set of populations as a distinct evolutionary species, nor do we establish preconceived notions on how subtle or dramatic are the suite of characteristics that delineate an evolutionary species from others. Instead, we let the plants and their evolutionary histories speak for themselves. As a consequence, more taxa have been found to represent distinct evolutionary species than previously known, and (perhaps not surprisingly) very few infraspecific taxa have been recognized; the few have generally been morphologically distinctive taxa that are clearly within the genetic structure of a broader species but that possess an unusual ecological or geographic component that urges recognition.
Typifications
Hundreds of names have been published for the native violets occurring in the Great Plains and eastern North America. As McNeill (2014) notes, designation of a holotype as a requirement for valid publication of a plant name has only been in force since 1990. Names published prior to that may or may not have cited specimens which could be construed as holotypes or any type material. For many names of violets published in the middle of the last century or before, authors often dispensed with citing any particular specimens, and when they did cite specimens they commonly listed multiple collections, and they commonly failed to note which herbarium harbored them. Nevertheless, it is incumbent on the specialist to attempt to typify each name. Some of the most widely used names (including accepted names) have been typified, some by McKinney and many by Gil-ad. However, many names have received no attention, and under the current code some typified names need further typification or re-typification (especially where "holotype" was assumed but could not be undeniably proven). McNeill cautions against lax interpretations of type material as representative of holotypes and points out that the requirements for a satisfactory holotype designation by the author of a name are more stringent than have usually been applied in past typifications. In reviewing the 100-plus names of North American violets published by E. L. Greene as well as the names most commonly applied to or accepted for violets in our region, almost none of them are supported by holotypes as specified by the current International Code of Nomenclature for Algae, Fungi and Plants (Turland et al. 2018). Most names require at least lectotypification (assuming original material can be found), and some may require neotypification. For the moment, types are cited mostly for accepted names where they are known or suspected. Clarifying comments are given in brackets.
Literature Cited
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