Competition affects mixed-mating strategies by limiting available abiotic or biotic resources such as nutrients, water, space, or pollinators. Cleistogamous species produce closed (cleistogamous, CL), obligately selfed, simultaneously with open (chasmogamous, CH), potentially outcrossed flowers. The effects of intraspecific competition on fitness and cleistogamy variation can range from limiting the production of costly CH flowers because of resource limitation, to favouring CH production because of fitness advantages of outcrossed, CH offspring. Moreover, the effects of competition can be altered when it co-occurs with other environmental variations. We grew plants from seven populations of the ruderal Lamium amplexicaule, originating from different climates and habitats, in a common garden experiment combining drought, interspecific competition, and seasonal variation. All these parameters have been shown to influence the degree of cleistogamy in the species on their own. In spring, competition and drought negatively impacted fitness, but the CL proportion only increased when plants were exposed to both treatments combined. We did not observe the same results in autumn, which can be due to non-adaptive phenotypic variation, or to differences in soil compactness between seasons. The observed responses are largely due to phenotypic plasticity, but we also observed phenotypic differentiation between populations for morphological, phenological, and cleistogamy traits, pointing to the existence of different ecotypes. Our data do not support the hypothesis that CL proportion should decrease when resources are scarce, as plants with reduced growth had relatively low CL proportions. We propose that variation in cleistogamy could be an adaptation to pollinator abundance, or to environment-dependent fitness differences between offspring of selfed and outcrossed seeds, two hypotheses worth further investigation. This opens exciting new possibilities for the study of the maintenance of mixed-mating systems using cleistogamous species as models that combine the effects of inbreeding and reproductive costs.

Department of Biology and Ecology Faculty of Science University of Ostrava Ostrava Chittussiho 10 71000Czech Republic

Department of Biology University Federico 2 of Naples Via Vicinale Cupa Cintia 21 80126 Naples Italy

Zobrazit více v PubMed

Albert LP, Campbell LG, Whitney KD.. 2011. Beyond simple reproductive assurance: cleistogamy allows adaptive plastic responses to pollen limitation. International Journal of Plant Sciences 172:862–869.

Amasino R. 2010. Seasonal and developmental timing of flowering. The Plant Journal: for Cell and Molecular Biology 61:1001–1013. PubMed

Ansaldi BH, Weber JJ, Goodwillie C, Franks SJ.. 2019. Low levels of inbreeding depression and enhanced fitness in cleistogamous progeny in the annual plant Triodanis perfoliata. Botany 97:405–415.

Arathi HS, Smith TJ.. 2023. Drought and temperature stresses impact pollen production and autonomous selfing in a California wildflower, Collinsia heterophylla. Ecology and Evolution 13:e10324.

Barrett SC, Harder LD.. 2017. The ecology of mating and its evolutionary consequences in seed plants. Annual Review of Ecology, Evolution, and Systematics 48:135–157.

Baskin JM, Baskin CC.. 1981. Seasonal changes in the germination responses of buried Lamium amplexicaule seeds. Weed Research 21:299–306.

Bell TJ, Quinn JA.. 1987. Effects of soil moisture and light intensity on the chasmogamous and cleistogamous components of reproductive effort of Dichanthelium clandestinum populations. Canadian Journal of Botany 65:2243–2249.

Berg H, Redbo-torstensson P.. 1998. Cleistogamy as a bet-hedging strategy in Oxalis acetosella, a perennial herb. Journal of Ecology 86:491–500.

Blanusa T, Vysini E, Cameron RWF.. 2009. Growth and flowering of Petunia and Impatiens: effects of competition and reduced water content within a container. HortScience 44:1302–1307.

Cheplick GP. 2007. Plasticity of chasmogamous and cleistogamous reproductive allocation in grasses. Aliso 23:286–294.

Cheptou PO, Mathias A.. 2001. Can varying inbreeding depression select for intermediary selfing rates? The American Naturalist 157:361–373. PubMed

Cheptou P-O, Imbert E, Lepart J, Escarré J; et al.2000. Effects of competition on lifetime estimates of inbreeding depression in the outcrossing plant Crepis sancta (Asteraceae). Journal of Evolutionary Biology 13:522–531.

Cheptou P-O, Lepart J, Escarre J.. 2002. Mating system variation along a successional gradient in the allogamous and colonizing plant Crepis sancta (Asteraceae). Journal of Evolutionary Biology 15:753–762.

Culley TM. 2000. Inbreeding depression and floral type fitness differences in Viola canadensis (Violaceae), a species with chasmogamous and cleistogamous flowers. Canadian Journal of Botany 78:1420–1429.

Falik O, Hoffmann I, Novoplansky A.. 2024. A novel type of neighbour perception elicits reproductive plasticity in an annual plant with a mixed mating system. Plant Biology 26:415–420. PubMed

Fisher RA. 1941. Average excess and average effect of a gene substitution. Annals of Eugenics 11:53–63.

Goodwillie C, Kalisz S, Eckert CG.. 2005. The evolutionary enigma of mixed mating systems in plants: occurrence, theoretical explanations, and empirical evidence. Annual Review of Ecology, Evolution, and Systematics 36:47–79.

Grime J. 1977. Evidence for existence of three primary strategies in plants and its relevance to ecological and evolutionary theory. American Naturalist 111:1169–1194.

Heywood JS, Smith SA.. 2021. Does cleistogamous self-fertilization provide reproductive assurance against seed predation in Ruellia humilis? The Southwestern Naturalist 65:116–122.

Jorgensen R, Arathi HS.. 2013. Floral longevity and autonomous selfing are altered by pollination and water availability in Collinsia heterophylla. Annals of Botany 112:821–828. PubMed PMC

Kalisz S, Vogler DW.. 2003. Benefits of autonomous selfing under unpredictable pollinator environments. Ecology 84:2928–2942.

Kalisz S, Vogler DW, Hanley KM.. 2004. Context-dependent autonomous self-fertilization yields reproductive assurance and mixed mating. Nature 430:884–887. PubMed

Koontz SM, Weekley CW, Haller Crate SJ, Menges ES.. 2017. Patterns of chasmogamy and cleistogamy, a mixed-mating strategy in an endangered perennial. AoB Plants 9:plx059. PubMed PMC

Lande R, Schemske DW.. 1985. The evolution of self-fertilization and inbreeding depression in plants. I. Genetic models. Evolution 39:24–40. PubMed

Lê S, Josse J, Husson F.. 2008. FactoMineR: an R package for multivariate analysis. Journal of Statistical Software 25:1–18.

Le Corff J. 1993. Effects of light and nutrient availability on chasmogamy and cleistogamy in an understory tropical herb, Calathea micans (Marantaceae). American Journal of Botany 80:1392–1399.

Lloyd DG. 1979. Some reproductive factors affecting the selection of self-fertilization in plants. American Naturalist 113:67–79.

Lloyd DG. 1992. Self-and cross-fertilization in plants. II. The selection of self-fertilization. International Journal of Plant Sciences 153:370–380.

Lloyd DG, Schoen DJ.. 1992. Self-and cross-fertilization in plants. I. Functional dimensions. International Journal of Plant Sciences 153:358–369.

Lord E. 1979. Physiological controls on the production of cleistogamous and chasmogamous flowers in Lamium-amplexicaule L. Annals of Botany 44:757–766.

Lord EM. 1981. Cleistogamy: a tool for the study of floral morphogenesis, function and evolution. The Botanical Review 47:421–449.

Lord EM. 1982. Effect of daylength on open flower production in the cleistogamous species Lamium amplexicaule L. Annals of Botany 49:261–263.

Morgan MT, Wilson WG.. 2005. Self-fertilization and the escape from pollen limitation in variable pollination environments. Evolution 59:1143–1148. PubMed

Munguía-Rosas MA, Campos-Navarrete MJ, Parra-Tabla V.. 2013. The effect of pollen source vs. flower type on progeny performance and seed predation under contrasting light environments in a cleistogamous herb. PLoS One 8:e80934. PubMed PMC

Munoz F, Violle C, Cheptou P-O.. 2016. CSR ecological strategies and plant mating systems: outcrossing increases with competitiveness but stress-tolerance is related to mixed mating. Oikos 125:1296–1303.

Oakley CG, Moriuchi KS, Winn AA.. 2007. The maintenance of outcrossing in predominantly selfing species: ideas and evidence from cleistogamous species. Annual Review of Ecology, Evolution, and Systematics 38:437–457.

Passioura JB. 1991. Soil structure and plant growth. Soil Research 29:717–728.

Schemske DW. 1978. Evolution of reproductive characteristics in Impatiens (Balsaminaceae): the significance of cleistogamy and chasmogamy. Ecology 59:596–613.

Schmitt J, Ehrhardt DW.. 1987. A test of the sib‐competition hypothesis for outcrossing advantage in Impatiens capensis. Evolution 41:579–590. PubMed

Seguí J, Lázaro A, Traveset A, Salgado-Luarte C, Gianoli E.. 2018. Phenotypic and reproductive responses of an Andean violet to environmental variation across an elevational gradient. Alpine Botany 128:59–69.

Sicard A, Lenhard M.. 2011. The selfing syndrome: a model for studying the genetic and evolutionary basis of morphological adaptation in plants. Annals of Botany 107:1433–1443. PubMed PMC

Soto TY, Ryan NA, Oakley CG.. 2024. Relative energetic economy of cleistogamous selfing in three populations of the perennial Ruellia humilis. International Journal of Plant Sciences 185:32–41.

Steets JA, Salla R, Ashman T-L.. 2006. Herbivory and competition interact to affect reproductive traits and mating system expression in Impatiens capensis. The American Naturalist 167:591–600. PubMed

Stojanova B, Cheptou P-O, Maurice S.. 2014. Does cleistogamy variation translate into outcrossing variation in the annual species Lamium amplexicaule (Lamiaceae)? Plant Systematics and Evolution 300:2105–2114.

Stojanova B, Maurice S, Cheptou P-O.. 2016. Is plasticity across seasons adaptive in the annual cleistogamous plant Lamium amplexicaule? Annals of Botany 117:681–691. PubMed PMC

Stojanova B, Maurice S, Cheptou P-O.. 2020. Season-dependent effect of cleistogamy in Lamium amplexicaule: flower type origin versus inbreeding status. American Journal of Botany 107:155–163. PubMed

Trapp EJ, Hendrix SD.. 1988. Consequences of a mixed reproductive system in the hog peanut, Amphicarpaea bracteata (Fabaceae). Oecologia 75:285–290. PubMed

Veena V, Nampy S.. 2019. Induced cleistogamy: a strategy for reproductive assurance in Murdannia nudiflora (Commelinaceae). Botany 97:547–557.

Waller DM. 1980. Environmental determinants of outcrossing in Impatiens capensis (Balsaminaceae). Evolution 34:747–761. PubMed

Whitehead MR, Lanfear R, Mitchell RJ, Karron JD.. 2018. Plant mating systems often vary widely among populations. Frontiers in Ecology and Evolution 6:38.

Winn AA, Moriuchi KS.. 2009. The maintenance of mixed mating by cleistogamy in the perennial violet Viola septemloba (Violaceae). American Journal of Botany 96:2074–2079. PubMed