Western North American Naturalist Volume 60 Number 4 Article 2 10-31-2000 Geographic distribution, morphological and molecular characterization, and relationships of Lathrocasis tenerrima (Polemoniaceae) Leigh A. Johnson North Caolina State University, Raleigh, North Carolina Terri L. Weese North Carolina State University, Raleigh, North Carolina Follow this and additional works at: https://scholarsarchive.byu.edu/wnan Recommended Citation Johnson, Leigh A. and Weese, Terri L. (2000) "Geographic distribution, morphological and molecular characterization, and relationships of Lathrocasis tenerrima (Polemoniaceae)," Western North American Naturalist: Vol. 60 : No. 4 , Article 2. Available at: https://scholarsarchive.byu.edu/wnan/vol60/iss4/2 This Article is brought to you for free and open access by the Western North American Naturalist Publications at BYU ScholarsArchive. It has been accepted for inclusion in Western North American Naturalist by an authorized editor of BYU ScholarsArchive. For more information, please contact [email protected], [email protected]. Western North American Naturalist 60(4), © 2000, pp. 355–373 GEOGRAPHIC DISTRIBUTION, MORPHOLOGICAL AND MOLECULAR CHARACTERIZATION, AND RELATIONSHIPS OF LATHROCASIS TENERRIMA (POLEMONIACEAE) Leigh A. Johnson1 and Terri L. Weese1 ABSTRACT.—Lathrocasis is a recently recognized genus of Polemoniaceae that circumscribes the species first named Gilia tenerrima A. Gray. This species, distributed primarily in the Great Basin and Rocky Mountain floristic regions, has previously escaped thorough taxonomic scrutiny. Surveys of herbarium specimens and living material show that some features of this species have been inaccurately characterized in the past, while other characteristics have not been previ- ously considered in assessing its relationships. Lathrocasis possesses a distinct suite of morphological features that, con- sidered as a whole, distinguish this taxon at the generic level. This suite of characters includes the mostly entire, non- mucronate leaves, effuse branching with diverging to retrorse and threadlike pedicels, uniformity of short stipitate glands throughout, uniovulate locules, spiriliferous seeds with verrucate seed coats, minute funnelform flowers with simple vasculature, and stamens equally inserted approximately mid-tube. Parsimony analyses of ITS, trnL, and matK genes recover similar trees that place Lathrocasis in Gilieae with possible sister relationships to Gilia, a group composed of Allophyllum, Collomia, and Navarretia, or both of these groups combined. A detailed description of L. tenerrima, a review of its taxonomic history, and notes on the type collection are presented. Key words: Lathrocasis, Polemoniaceae, Gilia, taxonomy, phylogeny, geographic distribution. Gilia tenerrima A. Gray is a small-flowered, of Gilia has incrementally narrowed during delicately statured annual species of mid-ele- the 20th century as natural groups previously vations distributed in the Great Basin and housed in this genus received independent Rocky Mountain floristic regions of western taxonomic recognition (Milliken 1904, Grant and United States. As with many inconspicuous Grant 1955, Grant 1956, Porter 1998a, 1998b). species, G. tenerrima has not received thor- Students of Polemoniaceae through the ough systematic study, and its relationship to 1940s generally followed Gray regarding the other Polemoniaceae typically has been inferred relationships of Gilia tenerrima. Brand (1907) without critical examination. Gilia tenerrima provided a more detailed Latin description of was described during a period when Gray’s this species than Gray, and placed it and G. view of diagnostic characters for genera of minutiflora with species now referred to North American Polemoniaceae was princi- Microsteris and Allophyllum in his section pally confined to staminal features and their Phlogastrum. Rydberg (1917) placed G. ten- relationship to the corolla (Gray 1870). Gray’s errima with G. minutiflora and G. sinistra M.E. Gilia was admittedly polymorphous and in- Jones in his informal “Minutiflorae.” Several cluded most temperate Polemoniaceae with important contributions to Polemoniaceae tax- the exception of Phlox, Polemonium, and a few onomy were restricted to the Californian flora disparate species referred to Collomia. Gray (Milliken 1904, Jepson 1925, Munz 1959) and (1870) placed G. tenerrima in section Micro- thus did not treat this species because it gilia, a taxon erected by Bentham (1845) to remained unknown in that state until the late house G. minutiflora Benth., which, like G. 1950s (Hardham 2356 RSA). Mason and Grant tenerrima, has single-seeded locules. Subse- (1948, 1951) placed G. tenerrima in their new quent workers rejected Gray’s generic cir- subgenus Kelloggia with G. minutiflora, G. cumscriptions and emphasized combinations leptalea E. Greene, and G. capillaris Kellogg— of characters, rather than single characters, for a group comparable in composition to Rydberg’s generic recognition in Polemoniaceae (Mason “Minutiflora” considering modern synonymy 1945). As a consequence, the circumscription and the different geographic ranges considered 1Department of Botany, North Carolina State University, Raleigh, NC 27695. Present address: Department of Botany and Range Science, Brigham Young University, Provo, UT 84602. 355 356 WESTERN NORTH AMERICAN NATURALIST [Volume 60 by these authors. Although following earlier for G. tenerrima relative to other Polemoni- workers in describing the leaves of G. tenerrima aceae either are not available in the literature as entire (Mason and Grant 1948), Mason and or, in some instances, have been inaccurately Grant (1951) selected an illustration depicting described. DNA sequence investigations (John- lobed leaves occasionally produced by this son and Soltis 1995, Johnson et al. 1996, Porter species. 1996) have included G. tenerrima, and the Grant and Grant (1954) were the first to inferences therein provided the stimulus to disassociate G. tenerrima from G. minutiflora critically examine the biology and affinities of and discounted relationship with G. leptalea this taxon. As a consequence of in-depth study, and G. capillaris by placing the latter 2 species Johnson (in Porter and Johnson 2000) estab- in their section Saltugilia. Because G. ten- lished a new genus, Lathrocasis, to house this errima was not the focus of their work, they enigmatic species. Here, we elaborate the indicated only that its affinities were probably rationale behind this taxonomic shift. We doc- in the direction of subgenus Campanulastrum ument the geographic distribution of Lathro- (G. campanulata A. Gray and relatives), where- casis tenerrima, describe its morphological as G. minutiflora was referred to subgenus attributes, and infer its phylogenetic relation- Ipomopsis. Grant (1959) reconsidered this deci- ships. The classification of Porter and Johnson sion, in part, and included G. tenerrima in sec- (2000), which encompasses several new com- tion Saltugilia without comment. In a regional binations for Polemoniaceae in addition to the flora of the Intermountain region of the west- formal description of Lathrocasis, is followed ern United States, Cronquist (1984) provided in the remainder of this paper. a somewhat detailed gross description of G. tenerrima and again associated it with G. MATERIALS AND METHODS minutiflora (Cronquist also recognized Gilia Morphology and Biogeography more broadly than Grant [1959] or Munz [1959] by retaining Ipomopsis and Allophyllum with- We obtained gross morphological observa- in Gilia). Day (1993a), in formally recognizing tions, large-scale measurements, and locality section Kelloggia (based on G. capillaris), re- data from a survey of 450 specimens of Lath- ferred G. tenerrima to section Giliastrum, a rocasis tenerrima representing 202 unique polymorphous taxon as defined by Grant accessions from 18 herbaria (BRY, CIC, GH, (1959) that included species showing affinities IDS, MONT, MONTU, NY, OSC, POM, to G. rigidula Benth. as well as species recog- RENO, RM, RSA, SRP, UC, UNLV, UTC, UW, nized earlier in subgenus Campanulastrum. and WILLU). Additional data from specimens Recent treatments attempting to deal specifi- housed at CAS, but not seen by us, were kindly cally with the relationships of G. tenerrima provided by A. Day (California Academy of first referred this species to Allophyllum (Grant Sciences, personal communication). Destructive 1998) and then Tintinabulum (Grant and Day observations, for example electron microscopy 1998). These publications concur with the re- of pollen grains, pollen ovule ratios, and inter- moval of G. tenerrima from Gilia as discussed nal flower measurements, were taken from by Johnson and Porter (1998), but inade- 10–25 samples haphazardly chosen to repre- quately consider the full body of evidence in sent the geographic range of all specimens determining its affinities. while also encompassing the range of size Paralleling its obscurity in the field, few variation at the whole-flower level. We made published comparative studies of character all reproductive measurements from pressed diversity in Polemoniaceae have included Gilia material rehydrated in Pohl’s solution (Pohl tenerrima. Broad investigations in this family 1965). Pohl’s solution was also used to rehy- of pollen morphology (Stuchlik 1967, Taylor drate young anthers for pollen counts. After and Levin 1975), pollen-ovule ratios (Plittman rehydration, anthers were momentarily placed and Levin 1990), and