Nesom, G.L. 2012. Taxonomy of Erythranthe sect. Simiola (Phrymaceae) in the USA and Mexico. Phytoneuron 40: 1–123. Published 16 May 2012. ISSN 2153 733X Corrections to Map 9 and Map 15, 21 May 2012 TAXONOMY OF ERYTHRANTHE SECT. SIMIOLA (PHRYMACEAE) IN THE USA AND MEXICO GUY L. NESOM 2925 Hartwood Drive Fort Worth, Texas 76109 www.guynesom.com ABSTRACT Erythranthe sect. Simiola includes 31 species from North America north of Mexico (some of them also occur in Mexico): E. arenicola , E. arvensis , E. brachystylis , E. caespitosa , E. calciphila , Erythranthe charlestonensis Nesom, sp. nov., Erythranthe chinatiensis Nesom, sp. nov., E. corallina , E. cordata , E. decora , E. geyeri , E. glaucescens , E. grandis , E. guttata , E. hallii , E. inamoena , E. laciniata , E. marmorata (including Mimulus whipplei ), E. michiganensis , E. microphylla , E. minor , E. nasuta , E. nudata , E. pardalis (including Mimulus cupriphilus ), E. parvula , Erythranthe regni Nesom, sp. nov., E. scouleri , E. thermalis , E. tilingii , E. unimaculata , and E. utahensis . Seven additional species, Erythranthe brevinasuta Nesom, sp. nov., E. dentiloba , Erythranthe lagunensis Nesom, sp. nov., E. madrensis , E. pallens , E. pennellii , and Erythranthe visibilis Nesom, sp. nov., are endemic to Mexico, while E. glabrata sensu stricto occurs only in Mexico, Central America, and South America . Erythranthe geyeri , E. inamoena , and E. utahensis have previously been treated within M. glabratus . The species are divided into 6 informal groups, several including subgroups. Provided here are a key to species, a description and distribution map for each species, and details of typification for all names, including synonyms. Lectotypes are designated for Mimulus bakeri Gandoger and ten taxa named by E.L. Greene: M. arvensis , M. implexus , M. lucens , M. scouleri var. caespitosus , M. puberulus , Mimulus guttatus var. grandis , M. guttatus var. insignis , M. marmoratus , M. longulus , and M. subreniformis . KEY WORDS : Mimulus sect. Simiolus , Mimulus guttatus , Erythranthe sect. Simiola , Erythranthe guttata , Erythranthe glabrata The species of Erythranthe sect. Simiola constitute a distinctive group in vegetative and floral morphology (Grant 1924) and in pollen morphology (Argue 1980). Molecular data indicate that the group is monophyletic (Beardsley et al. 2004) though relatively few species have been sampled. The species have previously been treated as Mimulus sect. Simiolus (see rationale for altered taxonomic concepts and nomenclature in Barker et al. 2012). The present study provides a taxonomic account of this group that differs substantially from most previous ones. The one closest in concept is that of Pennell (1951). A number of the species of sect. Simiola currently serve as experimental organisms for various laboratories studying evolutionary processes (Dudash et al. 2005; Wu et al. 2008; and see further comments below), and sect. Simiola was the object of intensive investigation from about 1950 until the 1990s by R.K. Vickery and his students, who made hundreds of chromosome counts and interspecific and infraspecific crosses and from these data drew corresponding inferences about isolating mechanisms. Vickery, however, never provided a synthesis that correlated taxonomic concepts with data from biological studies and his only incursion into formal taxonomy involved the naming of several Mexican species. In what might be considered a summary of his studies (1978), he noted that Mimulus guttatus is "highly polytypic which has led many authors to propose one or another of its forms as distinct species or varieties. The segregant taxa include such distinct species as M. glaucescens , M. laciniatus , M. nasutus , M. platycalyx , and at least 20 other less clear-cut forms (Grant 1924; Pennell 1951)." Nesom: Erythranthe sect. Simiola 2 Because of ambiguous identifications and an emphasis on species concepts defined primarily by crossing relationships, many of Vickery's studies are difficult to interpret. Further, many of his evolutionary scenarios were predicated on a priori concepts of relationship that are not supported here. Various botanists have studied the systematics of sect. Simiola , including Grant (1924), Campbell (1950), and Pennell (1935, 1947) and parts of the group have been considered in floristic treatments. Taxonomic assessments, however, have been variable in the ways they apportioned the variation and today there is little agreement on anything except for the status of a few seemingly clearly defined and mostly narrowly endemic species: E. glaucescens , E. laciniata , E. michiganensis , and E. nudata . Erythranthe glabrata , E. guttata , and E. tilingii are generally recognized, but varieties and subspecies have been recognized within each and there has been no agreement on patterns of variation or infraspecific nomenclature. Many superfluous names have been proposed for variants within sect. Simiola and significant disagreement exists in the placement of many names even as synonyms. Beardsley et al. (2004) remarked that "the species making up this section display a high degree of environmental plasticity," which is generally true, but such observations are likely also based in part on morphological variation across more than one species. Grant (1924) recognized 10 species of Mimulus sect. Simiolus in North America (including extra-California regions) and 8 varieties (3 in M. tilingii , 5 in M. guttatus ). Campbell (1950) recognized 4 species (excluding M. glabratus ) and divided M. guttatus into 4 varieties. In the only broad treatment to recognize more narrowly defined variants, Pennell (1951) treated 20 species in sect. Simiolus , including M. guttatus with 4 varieties. For California, Munz (1959) recognized 7 species (including M. guttatus with 4 subspecies) and Thompson (1993) in the Jepson Manual –– in the most recent overview of Mimulus sect. Simiolus –– recognized only 5 species. Mimulus guttatus was described by Thompson (1993, p. 1043) as "Exceedingly complex; local populations may be unique but their forms intergrade over geog or elevation; variants not distinguished here." Thompson even reached across traditional boundaries to include M. glabratus var. utahensis as a synonym within his broadly interpreted M. guttatus . Mimulus as a model study organism Evolutionary studies in Mimulus have emphasized isolating mechanisms and differentiation that can be documented at populational levels and small geographic scales. Evidence for the species status of Mimulus michiganensis (Posto & Prather 2003) and M. cupriphilus (Macnair 1989; Macnair & Cumbes 1989) has been provided along this avenue, and other segregates, especially from within M. guttatus in the broad sense, have been similarly recognized, though usually more tentatively. Evidence from biological studies suggests that isolating mechanisms among these plants are readily developed in local populations, thus it seems reasonable, at least as a working assumption, that some of such formally named variants might indeed be justifiably recognized at specific rank. Darwin's investigation (1876) of inbreeding depression and development of self-fertility in Mimulus luteus L. was the forerunner of monkeyflower biology. More recent studies of evolutionary processes have centered primarily on populations identified simply as Mimulus guttatus (usually without varietal designation or formal qualification) and as Mimulus nasutus (e.g., Kiang & Hamrick 1978; Sweigart & Willis 2003; Hall et al. 2006; Martin & Willis 2007, 2010; Swiegart et al. 2008; Wu et al. 2010). The California endemics M. glaucescens , M. laciniatus , and M. nudatus , which are generally recognized in floristic accounts, also have sometimes been included as well as a few other taxa that are often treated as synonyms in these kinds of detailed studies, e.g., M. caespitosus , M. cupriphilus , M. micranthus , M. platycalyx , and M. guttatus var. depauperutus (e.g., Macnair 1989; Macnair & Cumbes 1989; Ritland 1989; Ritland & Ritland 1989; Fenster & Ritland 1992; Carr & Dudash 1996; Awadalla & Ritland 1997; Lin & Ritland 1997; Fenster & Carr 1997; Ritland & LeBlanc 2004). Nesom: Erythranthe sect. Simiola 3 The basis on which taxa in these evolutionary studies have been identified has rarely if ever been specified. Fenster and Carr (1997) referred to Munz and Keck (1968) for the identification of Mimulus micranthus . Ritland & Ritland (1989) provided line drawings of taxa as guides to the identity of the experimental plants (these drawings do show some diagnostic features, but that of Mimulus nasutus shows large, chasmogamous, long-styled flowers, which evidently are of some other species). Sweigart and Willis (2003) noted that "taxonomic classifications were verified using morphological characteristics as described by Abrams (1951)" (i.e., the treatment contributed by Pennell). Studies of "coastal perennial M. guttatus " by Lowry et al. (2008) apparently refer at least in large part (as established in pers. communication with Lowry) to Erythranthe grandis as treated in the present overview; the contrasting "inland annual M. guttatus " apparently is Erythranthe microphylla . Further, although most of these kinds of studies have indicated at least the general localities from which the plants were obtained, not a single one surveyed in the current taxonomic study has cited vouchers in documentation. A clearer understanding of evolutionary patterns of variation in sect. Simiola , particularly including a knowledge of what