Ecophysiology and Genetic Variation in Domestication of Shpaeralcea and Shepherdia Species for the Intermountain West

The herbaceous perennial species in the genus Sphaeralcea have desirable drought tolerance and aesthetics with potential for low-water use landscapes. However, taxonomy of these species is ambiguous, which leads to decreased consumer confidence in the native plant industry. The goal of this study was to test and clarify morphological and genetic differentiation among four putative species. Morphological characteristics of the type specimens were used as species references in canonical variate analysis to generate a classification model, and assigned putative species names to USU herbarium specimens to clarify morphological, and field specimens to clarify genetic variation among species. Genotypic classifications were tested using Bayesian cluster analyses of AFLP genotypes. The putative S. grossulariifolia was not significantly different morphologically and genetically from S. coccinea, with similarities between S. munroana and S. parvifolia. The composite group of S. coccinea and S. grossulariifolia was distinguished morphologically and genetically from the S. munroana and S. parvifolia composite group, with significant correlation between genotypic and morphological characteristics in the overall samples. There was no correlation between geographical and genetic distances when all putative species pooled together in the Mantel’s correlation tests. However, the correlation was significant when tested within each composite group, suggesting they are con-specific species due to isolation-by-distance within each group. 1 Authors: Chalita Sriladda, Heidi Kratsch, Steven Larson, Roger Kjelgren 2 Additional index words: Sphaeralcea coccinea, Sphaeralcea grossulariifolia, Sphaeralcea munroana, Sphaeralcea parvifolia, globemallow, AFLP 6 Morphological distance exhibited a correlation with geographical distance within the S. parvifolia and S. munroana composite group, suggesting morphological isolation by distance. Therefore, the putative S. munroana may only be an ecotype of S. parvifolia. Globally, urbanization has dramatically increased, with nearly half of the world’s population currently living in urban areas; it is expected that approximately three quarters of the world’s population will be living in urban areas by the year 2025 (United Nations, 2010). Substantial increases in urban population lead to increased demand for water in commercial, industrial, and residential sectors (Foster and Beattie, 1979). This increased demand in arid and semiarid urban regions means facing the additional challenge of absolute water scarcity (Vorosmarty et al., 2000). Demand for urban green spaces includes urban landscapes is increasing with population growth because those spaces provide aesthetic and mental health benefits and a positive association with the perceived general health of residents (Maas et al., 2006). Urban green spaces also mitigate a number of undesirable environmental effects such as urban heat islands (Deloya, 1993). Many urban green spaces require irrigation, particularly in arid and semi-arid areas. Thus, increasing irrigation for urban landscapes is causing an increased demand for efficient watering systems. Low-water landscaping describes landscapes full of plants that use substantially less water. Therefore, low-water landscaping is a key tool for conserving water in irrigated urban landscapes, particularly in arid and semiarid areas (Kjelgren et al., 2009). 7 Drought-tolerant plants, particularly native species promoting water conservation, are key elements for successful low-water landscapes because they require little maintenance, provide a natural look to the landscape (Cane and Kervin, 2009; Kjelgren et al., 2009; McKinney, 2002), and honor natural habitats. Native plant landscaping also supports local economies, facilitating sustainability in urban systems at multiple levels. However, lack of native plant availability, cost of native plant materials, inconsistent and unreliable demand, and lack of production knowledge has minimalized the native plant market (Peppin et al., 2010). The U.S. Intermountain West (IMW) has an abundance of woody and herbaceous perennial native plants that are drought-tolerant and ornamentally attractive (Intermountain Native Plant Growers Association, 2011; Kratsch, 2011; Mee et al., 2003; Meyer et al., 2009). The genus Sphaeralcea (Malvaceae), Globemallow, is an annual or perennial herb or shrub wildflower, characterized by brilliant, largely orange, flowers. About 40 species of the genus are found throughout temperate North and South America (Holmgren et al., 2005). The genus Sphaeralcea includes 27 species in North America, from southern Canada through western United States to northern Mexico, with disjunct populations in temperate South America (Holmgren et al., 2005). Several of these species appear to have both aesthetic and drought-tolerance qualities that lend them well to lowwater landscaping (Intermountain Native Plant Growers Association, 2011; Mee et al., 2003); however, they are ostensibly closely related and difficult to distinguish. Four promising low-water landscape species, S. coccinea, S. grossulariifolia, S. munroana, and S. parvifolia are commonly found in the IMW (Holmgren et al., 2005; Ring, 2005; 8 Ring and Cully, 2007; Ring et al., 2009), and they are particularly difficult to distinguish from one another (Holmgren et al., 2005). Polyploidy and hybridization have been reported as factors contributing to weak morphological differences among species in the genus (La Duke and Northington, 1978). Tate (2002) also suggested the possible importance of geographical isolation for speciation. Analysis of nuclear ribosomal DNA internal transcribed spacer (ITS) sequences showed that the North American Sphaeralcea species (S. angustifolia and S. wrightii) cluster together, as do the two South American taxa (S. crispa and S. philippiana) (Tate, 2002). Inter-gradation among species challenged early taxonomists in their efforts to clearly identify Sphaeralcea species using only morphological distinctions. To varying degrees, these four species are being promoted by the nursery industry (Intermountain Native Plant Growers Association, 2011), but it is difficult to determine which species are actually being sold. Difficulty to determine species decreased consumer confidence in these species. Leaf morphology was used as the first taxonomic key to separate these species into two groups (Holmgren et al., 2005). Leaves shallowly lobed putatively separate S. munroana and S. parvifolia from S. grossulariifolia and S. coccinea, whose leaves are deeply lobed, cleft more than half way to the base, and in many, cleft to the base. However, S. munroana is often difficult to distinguish from S. parvifolia, while S. grossulariifolia can be easily confused with S. coccinea and some specimens of S. munroana (Holmgren et al., 2005). Besides leaf morphology, the mature fruiting carpel characteristics, density of leaf hairs, and hair ray orientation sometimes are used as keys for taxonomists to identify specimens (Atwood and Welsh, 2002). However, 9 these characters are seldom-used in practical settings, and are not efficient for field use or for non-taxonomist collectors. The intergrading morphology of these species might be a result of genetic overlap, and makes selection for superior forms difficult. In terms of the geological distribution of the four species (United States Department of Agriculture, 2010), S. coccinea is found extensively throughout the IMW, and S. grossulariifolia is found throughout the Great Basin area on the west side of the IMW. Distribution of S. munroana and S. parvifolia overlaps in Nevada, Utah, and Colorado, where S. parvifolia is distributed further south and S. munroana distributed further north. In Utah where the distributions of the four species overlap, geographical differences seem to play an important role in putative species distribution, particularly for S. munroana and S. parvifolia, which occur in the north and south, respectively (Shultz et al., 2010). The distribution has sometimes been used as a key for species identification because of difficulty due to morphological overlap among these species. Difficulty in their accurate identification creates concerns for those collecting Sphaeralcea seeds for nursery production, and reduces consumer confidence in the native plant industry, with plants varying widely in morphology being sold as the same species. The goal for this study was to clarify morphological and genetic distinctions among the four Sphaeralcea species, S. coccinea, S. grossulariifolia, S. munroana, and S. parvifolia,which may improve superior cultivar selections for use in low-water landscapes. 10 Materials and Methods Type specimens of the four Sphaeralcea species were used as references. We borrowed all available type specimens (holotype/isotype) representing the four species from herbaria across the U.S. and Great Britain. In summer 2008, we collected field specimens from 20 populations in Utah (Fig. 3-1). The field specimens were used for genetic and correlation analysis. In addition to the field specimens, existing voucher specimens from the Intermountain Herbarium at Utah State University (USU) were used to verify morphological variation within and among species. The voucher specimens from the USU Herbarium were also used to locate the field specimens. MORPHOLOGY. Morphological variation within and among type specimens were evaluated by measuring ten morphological characteristics of fully mature leaves (3 leaves per plant) (Table 3-1). In order to observe all possible variation within and among the type specimens, we measured morphological characteristics of all type specimens even though the numbers representing each species were unequal. Morphological characteristics of the type specimens were subjected to analysis of variance (ANOVA) using PROC GLM in SAS software (SAS Institute, Cary, NC) to compare variation of each morphological character among species. The morphological characteristics were subjected to canonical variate analysis (CVA) in NTSYSpc 2.2N software (Exeter Software, Setauket, NY) to generate a model for the purpose of assigning field and existing herbarium specimens to one of four putative Sphaeralcea species groups.