Species Of Clarkia Research Articles

V. Introduction and selection of a new species of Clarkia (C. purpurea) and development of a method for evaluating Clarkia pursh varieties for distinctiveness, uniformity and stability

During 2011–2023 in the south of Western Siberia, with the aim of introducing and selecting a new species of clarkia (C. purpurea), its biological characteristics and morphological characteristics were studied. Based on the data obtained and the use of other species and varieties of the genus Clarkia Pursh. For the first time, a methodology for conducting tests for distinctiveness, uniformity and stability (DUS) for this crop was developed. This technique is applicable to all varieties of the genus Clarkia Pursh, classified into sections: Godetia (C. purpurea (Curtis) A. Nelson & J. F. Macbr.), Phaeostoma (C. unguiculata Lindl.), Rhodanthos (C. amoena (Lehm.) A . Nelson & J. F. Macbr., Clarkia amoena ssp. lindleyi (Douglas) H. F. Lewis & M. Е. Lewis), fireweed family (Onagraceae Juss.). Many species of clarkia are characterized by long-lasting flowering and are promising for floral decoration of urban spaces, as well as for cutting. Most varieties are from very low – up to 25 cm tall, to very high – 96 cm or more; leaves are simple, lanceolate, narrow-lanceolate, wide-lanceolate, ovate, smooth, pubescent. The flowers are very decorative, varying in size from 2.0 to 8.0 cm tall, simple, semidouble, terry and strongly terry with or without fragrance, with a large variability of colors and types of floral pigmentation. Based on the study of the bioecological and morphological properties of the crop under study and in accordance with the rules approved by the Federal State Budgetary Institution “State Varietal Commission”, 36 characteristics were selected by which it is possible to test clarkey varieties. As a result of breeding work, a new variety of C. purpurea, Lilac Fairy, was created. When analyzing crossing, it was established that the lilac (violet) color of flowers is dominant in relation to pale pink (almost white), and when crossing F1 hybrids with light purple color, splitting 15:1 (15 violet from dark purple to pale purple was obtained and 1 is pale pink), which confirms the hypothesis about the polygenic nature of the inheritance of the main color of flowers in C. purpurea. The national methodology RTG/1157/1, created for the first time, for testing the DUS of Clarkia Pursh varieties will serve as a scientific basis for practical breeding.

Co-flowering richness has variable effects on pollen quantity and quality limitation in four Clarkia species.

Pollination failure occurs from insufficient pollen quantity or quality. However, the relative contributions of pollen quantity vs. quality to overall pollen limitation, and how this is affected by the co-flowering context, remain unknown for most plant populations. Here, we studied patterns of pollen deposition and pollen tube formation across populations of four predominately outcrossing species in the genus Clarkia to evaluate how the richness of co-flowering congeners affects the contribution of pollen quantity and quality to pollen limitation. We partition variation in pollen deposition and pollen tube production across individuals, populations and species to identify the main sources of variation in components of reproductive success. We further quantify the relative contribution of pollen quantity and quality limitation to the reproductive success of the four Clarkia species using piecewise regression analyses. Finally, we evaluate how variation in the number of co-flowering Clarkia species in the community affects the strength of pollen quality and quality limitation. Across all contexts, pollen deposition and the proportion of pollen tubes produced varied greatly among individuals, populations and species, and these were not always correlated. For instance, C. xantiana received the smallest pollen loads yet produced the highest proportion of pollen tubes, while C. speciosa exhibited the opposite pattern. Yet, co-flowering richness had variable effects on the strength of pollen quantity and quality limitation among populations. Specifically, breakpoint values, which are an indicator of overall pollen limitation, were two-fold higher in the four-species community compared with one- and two-species communities for two Clarkia species, suggesting that pollen limitation can increase with increasing richness of co-flowering congeners. Our results reveal a complex interplay between the quantity and quality of pollen limitation and co-flowering context that may have different evolutionary outcomes across species and populations.

The extent of introgression between incipient Clarkia species is determined by temporal environmental variation and mating system

Introgression is pervasive across the tree of life but varies across taxa, geography, and genomic regions. However, the factors modulating this variation and how they may be affected by global change are not well understood. Here, we used 200 genomes and a 15-y site-specific environmental dataset to investigate the effects of environmental variation and mating system divergence on the magnitude of introgression between a recently diverged outcrosser-selfer pair of annual plants in the genus Clarkia. These sister taxa diverged very recently and subsequently came into secondary sympatry where they form replicated contact zones. Consistent with observations of other outcrosser-selfer pairs, we found that introgression was asymmetric between taxa, with substantially more introgression from the selfer to the outcrosser. This asymmetry was caused by a bias in the direction of initial F1 hybrid formation and subsequent backcrossing. We also found extensive variation in the outcrosser's admixture proportion among contact zones, which was predicted nearly entirely by interannual variance in spring precipitation. Greater fluctuations in spring precipitation resulted in higher admixture proportions, likely mediated by the effects of spring precipitation on the expression of traits that determine premating reproductive isolation. Climate-driven hybridization dynamics may be particularly affected by global change, potentially reshaping species boundaries and adaptation to novel environments.

Biological features of flowering of the genetic collection of plants of the family Onagraceae Juss. in the forest-steppe conditions of Western Siberia

Data on the timing of the onset of phenological phases and the duration of the flowering period of the genetic collection of annual flowering plants from three sections of the family Onagraceae Juss. are presented: Rhodanthos, Godetia and Phaeostoma of the Clarkia Pursh. generic complex, outside their natural habitats (ex situ), on the collection site of the Novosibirsk State Agrarian University. As a result of the evaluation of the flowering phenomena of Clarkia sections, two flowering periods were identified. The species were distributed into summer-flowering plants C. purpurea from the Godetia section - with a vegetation duration of 102 ± 2 days and summer-autumn C. amoena and C. amoena subsp. Lindleyi from the Rhodanthos section with a vegetation duration of 123 ± 2 days and a species of C. unguiculata blooming throughout the period from the Phaeostoma section with a vegetation duration of 126 ± 2 days. Correlation analysis showed a high dependence of the growth and development periods of Clarkia species on the sum of biologically active temperatures > 10 °C (0.77 - 0.99). Cpurpurea from the Godetia section has the greatest adaptive potential to local climatic conditions, it requires the least amount of biologically active temperatures of the growing season (1903 °C) for growth and development than two other sections: Phaeostoma (2090 °C), Rhodanthos (2188 °C). Thus, all three sections of the Clarkia family Onagraceae Juss. they are characterized by prolonged flowering in the conditions of the forest-steppe of Western Siberia, are promising for urban gardening, differ in the possibility of sowing seeds in the open ground and are suitable for flower beds of continuous flowering.

Emission Rates of Species-Specific Volatiles Vary across Communities of Clarkia Species: Evidence for Multimodal Character Displacement.

AbstractA current frontier of character displacement research is to determine whether displacement occurs via multiple phenotypic pathways and varies across communities with different species compositions. Here, we conducted the first test for context-dependent character displacement in multimodal floral signals by analyzing variation in floral scent in a system that exhibits character displacement in flower size and that has multiple types of sympatric communities. In a greenhouse common garden experiment, we measured quantitative variation in volatile emission rates of the progeny of two species of Clarkia from replicated parental communities that contain one, two, or four Clarkia species. The first two axes of a constrained correspondence analysis, which explained 24% of the total variation in floral scent, separated the species and community types. Of the 23 compounds that were significantly correlated with these axes, nine showed patterns consistent with character displacement. Two compounds produced primarily by C. unguiculata and two compounds produced primarily by C. cylindrica were emitted in higher amounts in sympatry. Character displacement in some volatiles varied across sympatric parental communities and occurred in parallel with displacement in flower size, demonstrating that this evolutionary process can be context dependent and may occur through multiple pathways.

Phylogenomic analysis does not support a classic but controversial hypothesis of progenitor-derivative origins for the serpentine endemic Clarkia franciscana.

Budding speciation involves isolation of marginal populations at the periphery of a species range and is thought to be a prominent mode of speciation in organisms with low dispersal and/or strong local adaptation among populations. Budding speciation is typically evidenced by abutting, asymmetric ranges of ecologically divergent sister species and low genetic diversity in putative budded species. Yet these indirect patterns may be unreliable, instead caused by postspeciation processes such as range or demographic shifts. Nested phylogenetic relationships provide the most conclusive evidence of budding speciation. A putative case of budding speciation in the serpentine endemic Clarkia franciscana and two closely related widespread congeners was studied by Harlan Lewis, Peter Raven, Leslie Gottlieb, and others over a 20‐year period, yet the origin of C. franciscana remains controversial. Here, we reinvestigate this system with phylogenomic analyses to determine whether C. franciscana is a recently derived budded species, phylogenetically nested within one of the other two putative progenitor species. In contrast to the hypothesized pattern of relatedness among the three Clarkia species, we find no evidence for recent budding speciation. Instead, the data suggest the three species diverged simultaneously. We urge caution in using contemporary range patterns to infer geographic modes of speciation.

Lipid Profiles of the Heads of Four Shrimp Species by UPLC-Q-Exactive Orbitrap/MS and Their Cardiovascular Activities.

Lipids are key factors in nutrition, structural function, metabolic features, and other biological functions. In this study, the lipids from the heads of four species of shrimp (Fenneropenaeus chinensis (FC), Penaeus japonicus (PJ), Penaeus vannamei (PV), and Procambarus clarkia (PCC)) were compared and characterized based on UPLC–Q–Exactive Orbitrap/MS. We compared the differences in lipid composition of four kinds of shrimp head using multivariate analysis. In addition, a zebrafish model was used to evaluate pro-angiogenic, anti-inflammatory, anti-thrombotic, and cardioprotective activities of the shrimp head lipids. The lipids from the four kinds of shrimp head had different degrees of pro-angiogenic activities, and the activities of PCC and PJ shrimp lipids were more significant than those of the other two species. Four lipid groups displayed strong anti-inflammatory activities. For antithrombotic activity, only PCC (25 μg/mL) and PV (100 μg/mL) groups showed obvious activity. In terms of cardioprotective activity, the four kinds of lipid groups significantly increased the zebrafish heart rhythms. The heart distances were shortened, except for those of the FC (100 μg/mL) and PJ (25 μg/mL) groups. Our comprehensive lipidomics analysis and bioactivity study of lipids from different sources could provide a basis for the better utilization of shrimp.

PHENOLOGICAL SENSITIVITIES TO CLIMATE ARE SIMILAR IN TWO CLARKIA CONGENERS: INDIRECT EVIDENCE FOR FACILITATION, CONVERGENCE, NICHE CONSERVATISM, OR GENETIC CONSTRAINTS

To date, most herbarium-based studies of phenological sensitivity to climate and of climate-driven phenological shifts fall into two categories: detailed species-specific studies vs. multi-species investigations designed to explain inter-specific variation in sensitivity to climate and/or the magnitude and direction of their long-term phenological shifts. Few herbarium-based studies, however, have compared the phenological responses of closely related taxa to detect: (1) phenological divergence, which may result from selection for the avoidance of heterospecific pollen transfer or competition for pollinators, or (2) phenological similarity, which may result from phylogenetic niche conservatism, parallel or convergent adaptive evolution, or genetic constraints that prevent divergence. Here, we compare two widespread Clarkia species in California with respect to: the climates that they occupy; mean flowering date, controlling for local climate; the degree and direction of climate change to which they have been exposed over the last ∼115 yr; the sensitivity of flowering date to inter-annual and to long-term mean maximum spring temperature and annual precipitation across their ranges; and their phenological change over time. Specimens of C. cylindrica were sampled from sites that were chronically cooler and drier than those of C. unguiculata, although their climate envelopes broadly overlapped. Clarkia cylindrica flowers ∼ 3.5 d earlier than C. unguiculata when controlling for the effects of local climatic conditions and for quantitative variation in the phenological status of specimens. However, the congeners did not differ in their sensitivities to the climatic variables examined here; cumulative annual precipitation delayed flowering and higher spring temperatures advanced flowering. In spite of significant spring warming over the sampling period, neither species exhibited a long-term phenological shift. Precipitation and spring temperature interacted to influence flowering date: the advancing effect on flowering date of high spring temperatures was greater in dry than in mesic regions, and the delaying effect of high precipitation was greater in warm than in cool regions. The similarities between these species in their phenological sensitivity and behavior are consistent with the interpretation that facilitation by pollinators and/or shared environmental conditions generate similar patterns of selection, or that limited genetic variation in flowering time prevents evolutionary divergence between these species.

Bee species exhibit different phenological trajectories in communities of annual flowering plants in the genus Clarkia

Phenological matching between the timing of flowering and pollinator activity is critically important for the persistence of pollination systems globally. Phenological mismatch between plants and their insect pollinators can occur if flowering and adult insect activity do not occur simultaneously. There is evidence that the phenological trajectories vary among bee species, but little has been done to compare these trajectories with the phenology of the corresponding floral community. In this work, we use daily pan trapping across nine different annual Clarkia (Onagraceae) plant communities that vary in Clarkia species composition to estimate the phenological trajectory (within-season abundance curve) of the two most abundant bee pollinators - Lasioglossum incompletum, a generalist, and Hesperapis regularis, a Clarkia specialist - over the course of a Clarkia flowering season in California USA. Clarkia flower at the end of the winter annual growing season when all other winter annual plants have senesced, and therefore are phenologically separate from other flowering plants. We find that Hesperapis pollinator abundances follow the same phenological trajectory as Clarkia floral abundances in all community types. In contrast, Lasioglossum abundances do not track Clarkia floral abundance through time. Our results demonstrate that Clarkia exhibit closer phenological matching with Hesperapis than with Lasioglossum. These findings imply that pollinator communities may not respond monolithically to changes in the environment. Future research should study the phenological trajectories of plants and pollinators in different systems to determine if this pattern is common and repeatable.

Molecular assays of pollen use consistently reflect pollinator visitation patterns in a system of flowering plants.

Determining how pollinators visit plants vs. how they carry and transfer pollen is an ongoing project in pollination ecology. The current tools for identifying the pollens that bees carry have different strengths and weaknesses when used for ecological inference. In this study we use three methods to better understand a system of congeneric, coflowering plants in the genus Clarkia and their bee pollinators: observations of plant-pollinator contact in the field, and two different molecular methods to estimate the relative abundance of each Clarkia pollen in samples collected from pollinators. We use these methods to investigate if observations of plant-pollinator contact in the field correspond to the pollen bees carry; if individual bees carry Clarkia pollens in predictable ways, based on previous knowledge of their foraging behaviors; and how the three approaches differ for understanding plant-pollinator interactions. We find that observations of plant-pollinator contact are generally predictive of the pollens that bees carry while foraging, and network topologies using the three different methods are statistically indistinguishable from each other. Results from molecular pollen analysis also show that while bees can carry multiple species of Clarkia at the same time, they often carry one species of pollen. Our work contributes to the growing body of literature aimed at resolving how pollinators use floral resources. We suggest our novel relative amplicon quantification method as another tool in the developing molecular ecology and pollination biology toolbox.

Intraspecific variability of floral and ornamental plants of Onagraceae family and mechanisms of their variety formation

The present review is devoted to intraspecific variability of floral and ornamental plants of the genus Clarkia purch. Family Onagraceae and clarification of the systematic status of the Godetia species introduced into Novosibirsk. Clarkia species from the Godetia and Rhodantos sections are noted for their particular beauty and duration of flowering. A comprehensive study of the influence of environmental conditions on genetic features of populations, ornamental qualities, flowering biology, morphogenesis, organogenesis, seed production and seed quality, agrotechnology’s of growing the above species of Clarkia, for selecting suitable forms and creating local varieties included in the basic assortment of flower crops for climatic conditions of Western Siberia as well as their introduction into urban gardening is necessary. The article discusses taxonomic markers important for determining the systematic position of Clarkia species from Godetia and Rhodantos sections in the family Onagraceae. Experimental data of genetic and cytological analyses carried out by foreign scientists for the last 100 years are presented, which give an idea of morphological, karyological characteristics and genetic variability in various species in the Godetia section. The mechanisms of inheritance of the flower colour trait and numerous variations in the position of the spot on the petals of different clarkia species have been established. Formation of the list of genes responsible for the Clarkia pigmentation system, location and size of the carmine spot will allow targeted selection for qualitative traits. The study of the pattern of multifactorial inheritance of habitus and flower shape traits among C. amoena subspecies contributes to the passage of the most decorative hybrid forms (varieties) as the starting material. In conclusion, a brief overview of promising species of the genus Clarkia from the Godetia and Rhodantos sections for ornamental plant breeding and selection is given.

Species‐specific variation in germination rates contributes to spatial coexistence more than adult plant water use in four closely related annual flowering plants

Abstract Spatial partitioning is a classic hypothesis to explain plant species coexistence, but evidence linking local environmental variation to spatial sorting, demography and species' traits is sparse. If co‐occurring species' performance is optimized differently along environmental gradients because of trait variation, then spatial variation might facilitate coexistence. We used a system of four naturally co‐occurring species of Clarkia (Onagraceae) to ask whether distribution patchiness corresponds to variation in two environmental variables that contribute to hydrological variation. We then reciprocally sowed Clarkia into each patch type and measured demographic rates in the absence of congeneric competition. Species sorted in patches along one or both gradients, and in three of the four species, germination rate in the ‘home’ patch was higher than all other patches. Spatially variable germination resulted in the same three species exhibiting the highest population growth rates in their home patches. Species' trait values related to plant water use, as well as indicators of water stress in home patches, differed among species and corresponded to home patch attributes. However, post‐germination survival did not vary among species or between patch types, and fecundity did not vary spatially. Synthesis. Our research demonstrates the likelihood that within‐community spatial heterogeneity affects plant species coexistence, and presents novel evidence that differential performance in space is explained by what happens in the germination stage. Despite the seemingly obvious link between adult plant water‐use and variation in the environment, our results distinguish the germination stage as important for spatially variable population performance.

Ecological sorting and character displacement contribute to the structure of communities ofClarkiaspecies

Despite long-standing interest in the evolutionary ecology of plants that share pollinators, few studies have explored how these interactions may affect communities during both community assembly (ecological sorting) and through ongoing, insitu evolution (character displacement), and how the effects of these interactions may change with community context. To determine if communities display patterns consistent with ecological sorting, we assessed the frequency of co-occurrence of four species of Clarkia in the southern Sierra foothills (Kern County, CA, USA). To investigate potential character displacement, we measured pollination-related traits on plants grown in a greenhouse common garden from seed collected in communities with one, two or four Clarkia species. Among the four species of Clarkia in this region, the two species that are often found in multi-species communities also co-occur with one another more frequently than expected under a null model. This pattern is consistent with ecological sorting, although further investigation is needed to determine the role of pollinators in shaping community assembly. Patterns of trait variation in a common garden suggest that these two species have diverged in floral traits and converged in flowering time where they co-occur, which is consistent with character displacement. Trait variation across community types also suggests that the process and outcome of character displacement may vary with community context. Because community context appears to affect both the direction and magnitude of character displacement, change in more species-rich communities may not be predictable from patterns of change in simpler communities.

Empirical test on the relative climatic sensitivity between individuals of narrowly and broadly distributed species

AbstractClimate change is already influencing global ecology, exacerbating human‐induced biodiversity loss with potentially devastating results. A first step to addressing climate change impacts on conservation is to better understand how and to what extent species will be affected. Species with smaller geographic distributions are commonly perceived to be at highest risk of extinction. However, estimates of species vulnerability are frequently based on simplifying assumptions regarding climatic tolerance, usually arrived at through the use of models that associate mean spatial or temporal climate values with species distributions. Model estimated climatic tolerances may be improved by incorporating either finer spatial or temporal resolutions and/or additional distribution‐limiting factors like dispersal, habitat connectivity, and species interactions. However, the underlying assumption that species‐level climatic reflect individual tolerances can skew vulnerability estimates toward over‐or underestimation. We use empirically derived fitness reaction norms of biomass and seed pod count to estimate the relative sensitivity of individuals of broadly distributed (BD) and narrowly distributed (ND) species across temperature and water gradients. Temperature and water treatments were based on local climate station data and IPCC projections of climatic change. On the basis of fitness reaction norms, we infer relative vulnerability to examine the assumption that ND species are relatively more vulnerable to climatic change than BD species. Study species included the BD Mimulus guttatus and Clarkia purpurea and the ND Mimulus nudatus and Clarkia gracilis ssp. tracyi. Compared to M. nudatus (ND), individuals of M. guttatus (BD) exhibited biomass responses that were significantly more sensitive to temperature and seed pod count responses that were significantly more sensitive to water and temperature. Conversely, compared to C. purpurea (BD), C. gracilis ssp. tracyi (ND) individuals exhibited biomass and seed pod count responses that were significantly more sensitive to temperature. In addition, we measured unexpected positive responses from both Clarkia species to increases in temperature. Our results support the idea that, when examined at a local scale, the size of a species' geographic distribution does not necessarily correlate to climate change vulnerability.

Winning in style: Longer styles receive more pollen, but style length does not affect pollen attrition in wild Clarkia populations.

One proposed function of long styles is to intensify selection among male gametophytes relative to short styles. If so, given sufficient competition, longer styles will have higher rates of pollen tube attrition (failure to reach the style base) within the style than shorter ones. Alternatively, style length may influence pollen receipt, which itself may affect attrition rates. We tested these predictions by collecting senescing styles from wild populations of two insect-pollinated Clarkia species. We examined the number of pollen grains adhering to the stigma, length of styles, and rates of attrition from the stigma surface to the stigma-style junction (SSJ), from the SSJ to the style base, and from the stigma surface to the style base. Multivariate analyses estimated the independent effects of pollen grains per stigma, the number of pollen tubes at the SSJ, and style length on attrition. Style length was generally positively correlated with pollen receipt, and the number of pollen grains per stigma was positively correlated with all three attrition rates. In neither species was any attrition rate affected by style length independent of the number of pollen grains per stigma. Pollen attrition was mediated by style length, but the function of style length was primarily to increase the number of germinating pollen grains, which affected attrition rates either through stigma clogging or pollen-pollen interactions. Style length may have a direct effect on pollen receipt due to the stigma's position relative to pollinator body parts, but traits correlated with style length may also directly affect pollen receipt.

Allyl/propenyl phenol synthases from the creosote bush and engineering production of specialty/commodity chemicals, eugenol/isoeugenol, in Escherichia coli

The creosote bush (Larrea tridentata) harbors members of the monolignol acyltransferase, allylphenol synthase, and propenylphenol synthase gene families, whose products together are able to catalyze distinct regiospecific conversions of various monolignols into their corresponding allyl- and propenyl-phenols, respectively. In this study, co-expression of a monolignol acyltransferase with either substrate versatile allylphenol or propenylphenol synthases in Escherichia coli established that various monolignol substrates were efficiently converted into their corresponding allyl/propenyl phenols, as well as providing proof of concept for efficacious conversion in a bacterial platform. This capability thus potentially provides an alternate source to these important plant phytochemicals, whether for flavor/fragrance and fine chemicals, or ultimately as commodities, e.g., for renewable energy or other intermediate chemical purposes.Previous reports had indicated that specific and highly conserved amino acid residues 84 (Phe or Val) and 87 (Ile or Tyr) of two highly homologous allyl/propenyl phenol synthases (circa 96% identity) from a Clarkia species mainly dictate their distinct regiospecific catalyzed conversions to afford either allyl- or propenyl-phenols, respectively. However, several other allyl/propenyl phenol synthase homologs isolated by us have established that the two corresponding amino acid 84 and 87 residues are not, in fact, conserved.

Drought alters the expression of mating system traits in two species of Clarkia

Variation in mating system traits can have important consequences for plant populations by affecting reproductive assurance, the expression of inbreeding depression, and the colonization of and persistence in new or altered habitats. Environmental stressors, such as drought, have been hypothesized to induce higher rates of self-fertilization, yet this hypothesis has rarely been tested. Here we measure the response of two sister species of self-compatible annual herbs from contrasting habitats, Clarkia breweri and C. concinna, to an experimentally imposed greenhouse drought treatment. We find that the species differ in their baseline per-flower autogamy rates and the degree of spatial and temporal separation of male and female function within their flowers. Both species show a reduction in temporal separation of anthesis and stigma receptivity with the drought treatment. However, the species from the more mesic habitat, C. concinna, increases its low autogamy rate under drought conditions, whereas the species from the more xeric habitat, C. breweri, decreases its high autogamy rate under drought conditions. Neither species showed a response to drought in flower size or anther-stigma distance. Our results demonstrate that the induction of selfing under environmental stress cannot be assumed and that, in this case, the developmental timing of flower maturation is more plastic than floral morphology.

A Taxonomic Reassessment of Clarkia Calientensis and Clarkia Tembloriensis

The taxonomic relationships of Clarkia calientensis were re-evaluated in light of information accumulated subsequent to its designation as C. tembloriensis subsp. calientensis. Closeness of relationship between C. calientensis and C. tembloriensis was based on ease of crossing and on cytological pairing configurations in intertaxon hybrids. These interpretations require the assumptions that closely related species are easy to cross, and that maximum cytological configurations are known. However, extensive crossing data show that sympatric, closely related species of Clarkia are very difficult to cross but allopatric species cross rather readily. Furthermore, the cytological data are incomplete as maximum configurations are seldom observed, and some hybrids have not been produced. In both cases, the required assumptions are not tenable. Sterile hybrids between these two easily crossed taxa are strong evidence that they are not conspecific. Consequently, C. calientensis should be recognized as an independent species. Examination of floral variation in C. tembloriensis led to the recognition of large-flowered, protandrous forms as a new subspecies: C. tembloriensis subsp. longistyla.

MATING SYSTEM AND PLOIDY INFLUENCE LEVELS OF INBREEDING DEPRESSION IN CLARKIA (ONAGRACEAE)

Inbreeding depression is the reduction in offspring fitness associated with inbreeding and is thought to be one of the primary forces selecting against the evolution of self-fertilization. Studies suggest that most inbreeding depression is caused by the expression of recessive deleterious alleles in homozygotes whose frequency increases as a result of self-fertilization or mating among relatives. This process leads to the selective elimination of deleterious alleles such that highly selfing species may show remarkably little inbreeding depression. Genome duplication (polyploidy) has also been hypothesized to influence levels of inbreeding depression, with polyploids expected to exhibit less inbreeding depression than diploids. We studied levels of inbreeding depression in allotetraploid and diploid species of Clarkia (Onagraceae) that vary in mating system (each cytotype was represented by an outcrossing and a selfing species). The outcrossing species exhibited more inbreeding depression than the selfing species for most fitness components and for two different measures of cumulative fitness. In contrast, though inbreeding depression was generally lower for the polyploid species than for the diploid species, the difference was statistically significant only for flower number and one of the two measures of cumulative fitness. Further, we detected no significant interaction between mating system and ploidy in determining inbreeding depression. In sum, our results suggest that a taxon's current mating system is more important than ploidy in influencing levels of inbreeding depression in natural populations of these annual plants.

Seed Mass and Morphology in Outcrossing and Selfing Species of Clarkia (Onagraceae): An SEM Study

Seed Mass and Morphology in Outcrossing and Selfing Species of Clarkia (Onagraceae): An SEM Study