Flowering Frequency Research Articles

Flower Position and Size Impact Ovule Number per Flower, Fruitset, and Fruit Size in Pomegranate

Pomegranate trees (Punica granatum) produce large numbers of both hermaphroditic (bisexual) flowers that produce fruit and functionally male flowers that characteristically abort. Excessive production of male flowers can result in decreased yields resulting from their inability to set fruit. Within hermaphroditic flowers, sex expression appears to follow a spectrum ranging from those exhibiting strong to weak pistil development. Unknown is the scope that flower quality plays in influencing fruit production. A description of floral characteristics and how they vary with flowers of different sizes and positions is lacking in pomegranate and was the focus of this study. Furthermore, the effects of flower size and position on fruit set and fruit size were evaluated. This study documents that flower size characteristics and ovule development can be quite variable and are related to flower type and position. Single and terminal flowers within a cluster were larger than lateral flowers. In addition, lateral flowers exhibited a high frequency of flowers with poor ovule development sufficient to negatively impact fruiting in that flower type. Ovule numbers per flower were significantly influenced by flower size with more ovules in larger flowers. Pollination studies verified significantly higher fruit set and fruit weight, and larger commercial size distributions were obtained with larger vs. smaller flowers. Thus, flower quality is an important issue in pomegranate. Cultural and environmental factors that influence flower size and vigor may have a direct consequence on fruit production and yield.

Characterization of north-eastern Australian environments using APSIM for increasing rainfed maize production

Recurring water stresses are a major risk factor for rainfed maize cropping across the highly diverse agro-ecological environments of Queensland (Qld) and northern New South Wales (NNSW). Enhanced understanding of such agro-ecological diversity is necessary to more consistently sample target production environments for testing and targeting release of improved germplasm, and to improve the efficiency of the maize pre-breeding and breeding programs of Qld and New South Wales. Here, we used the Agricultural Production Systems Simulator (APSIM) – a well validated maize crop model to characterize the key distinctive water stress patterns and risk to production across the main maize growing regions of Qld and NNSW located between 15.8° and 31.5°S, and 144.5° and 151.8°E. APSIM was configured to simulate daily water supply demand ratios (SDRs) around anthesis as an indicator of the degree of water stress, and the final grain yield. Simulations were performed using daily climatic records during the period between 1890 and 2010 for 32 sites-soils in the target production regions. The runs were made assuming adequate nitrogen supply for mid-season maize hybrid Pioneer 3153. Hierarchical complete linkage analyses of the simulated yield resulted in five major clusters showing distinct probability distribution of the expected yields and geographic patterns. The drought stress patterns and their frequencies using SDRs were quantified using multivariate statistical methods. The identified stress patterns included no stress, mid-season (flowering) stress, and three terminal stresses differing in terms of severity. The combined frequency of flowering and terminal stresses was highest (82.9%), mainly in sites-soils combinations in the west of Qld and NNSW. Yield variability across the different sites-soils was significantly related to the variability in frequencies of water stresses. Frequencies of water stresses within each yield cluster tended to be similar, but different across clusters. Sites-soils falling within each yield cluster therefore could be treated as distinct maize production environments for testing and targeting newly developed maize cultivars and hybrids for adaptation to water stress patterns most common to those environments.

Differential competitive ability between sexes in the dioecious Antennaria dioica (Asteraceae).

Differences in competitive ability between the sexes of dioecious plants are expected as a result of allocation trade-offs associated with sex-differential reproductive costs. However, the available data on competitive ability in dioecious plants are scarce and contradictory. In this study sexual competition was evaluated using the dioecious plant Antennaria dioica in a common garden transplantation experiment. Male and female plants were grown for 3 years either in isolation, or in competition with a plant of the same sex or the opposite sex. Flowering phenology, sexual and asexual reproduction, plant growth, nutrient content and arbuscular mycorrhizal colonization in the roots were assessed. Our results showed little evidence of sexual differences in competitive ability. Both sexes suffered similarly from competition, and competitive effects were manifested in some traits related to fitness but not in others. Survival was unaffected by competition, but competing plants reduced their vegetative growth and reproductive investment compared with non-competing plants. In addition, differences in sexual competitive ability were observed in relation to flowering frequency, an important life history trait not reported in previous studies. The findings indicate that female and male A. dioica plants possess similar intersexual competitive abilities which may be related to the similar costs of reproduction between sexes in this species. Nevertheless, intrasexual competition is higher in females, giving support for asymmetric niche segregation between the sexes.

Impact of disease frequency and host density on pollination and transmission of an African anther-smut fungus

The vast majority of flowering plants rely solely on insects for pollination. A number of pathogens have evolved mechanisms to exploit these close associations and use pollinators as vectors of infective propagules. Factors that affect pollinator movements and successful pollination may in turn also influence successful transmission of fungal spores. Here we investigate the effect of host density and the frequency of diseased Oxalis lanata individuals infected by the anther-smut fungus, Thecaphora capensis, on the likelihood of receiving pollen and fungal spores. Specifically, we determined the numbers of spores and pollen grains deposited on stigmatic surfaces of selected flowers under natural and standardized conditions where host density and disease frequency varied. The effect of host flower density and diseased flower frequency on pollen and spore transfer was variable under natural conditions and these factors interacted significantly. However, an increase in host density and disease frequency significantly influenced pollen and spore deposits under standardized conditions. The effect of host density was, however, not linear and an optimal flower density for pollen and fungal spore transmission was found. Similar to other systems of vector-borne disease, the transmission of anther-smut of Oxalis lanata is more frequency-dependent than density-dependent. This study represents a first step towards understanding the disease transmission process of T. capensis on Oxalis and lays the foundation for future comparative studies between this and other systems to develop and test general hypotheses of disease dynamics in vector-borne disease transmission systems.

Generative Reproduction Dynamics in Populations of The Perennial HerbPolygonatum Multiflorum(Asparagaceae)

Generative reproduction traits of the perennial Polygonatum multiflorum (Asparagaceae) were studied in seven populations in 2000–2010. The frequencies of typical hermaphrodite flowers and functionally male flowers with short or atrophied carpels were 76%, 17% and 7%, respectively. Most hermaphrodite flowers occurred in the lower and middle positions on the ramets. The final fruit/flower ratio per ramet amounted to 25% and its variation was higher among populations than among years. The initial fruit set was on an average twice as high as the final fruit set. The mean number of seeds per fruit was 3.2, and the distribution was skewed to the right. At the inter-population level, the seed number and mass of fruits were negatively correlated with each other. Seed size/number trade off was significant for shoots and for fruits. The seedling emergence was 65%–82% and it was positively correlated with the seed size as well as the survival of seedlings. In the garden conditions, a few individuals flowered in the seventh year of development.

Andromonoecy in an Old World Papilionoid legume, Erophaca baetica

Andromonoecy (i.e. the occurrence on individual plants of hermaphroditic and male flowers) is a rare sexual system among the angiosperms, regarded by some authors as a transitional stage from hermaphroditism to monoecy. Having discovered the occurrence of andromonoecy in Erophaca baetica (a Mediterranean shrubby legume with two subspecies), a novelty for Old World papilionoid legumes, we investigated the morpho-functional correlates and the geographical distribution of this phenomenon in the species. The relative frequencies of hermaphrodite and male flowers were determined in two field and 111 herbarium populations. Biomass allocation within flowers, pollen production and viability, pollen tube growth, nectar production and the temporal pattern of male flower production were also studied in two nearby southern Spanish populations. Virtually all of the studied populations were andromonoecious. Male flowers tended to appear at apical positions within the inflorescence, and became more abundant by the end of the flowering season. Male flowers were externally similar to hermaphroditic flowers (although with less biomass and smaller parts) and released equivalent amounts of pollen and nectar; however, their pollen germinated significantly better. Erophaca is the first example of an andromonecious Papilionoid in the Old World. Since the main difference among floral morphs in this species is functional (i.e. pollen germination rate) rather than morphological, andromonoecy is not readily noticeable, and very careful inspection may be required to reveal it. The potential effect of andromonoecy in enhancing outcrossing rate in this species is discussed.

Nutrient limitation restricts growth and reproductive output in a tropical montane cloud forest bromeliad: findings from a long-term forest fertilization experiment

From studies in seasonal lowland tropical forests, bromeliad epiphytes appear to be limited mainly by water, and to a lesser extent by nutrient supply, especially phosphorous. Less is understood about the mineral nutrition of tropical montane cloud forest (TMCF) epiphytes, even though their highest diversity is in this habitat. Nutrient limitation is known to be a key factor restricting forest productivity in TMCF, and if epiphytes are nutritionally linked to their host trees, as has been suggested, we would expect that they are also nutrient limited. We studied the effect of a higher nutrient input on reproduction and growth of the tank bromeliad Werauhia sintenisii in experimental plots located in a TMCF in Puerto Rico, where all macro- and micronutrients had been added quarterly starting in 1989 and continuing throughout the duration of this study. We found that bromeliads growing in fertilized plots were receiving litterfall with higher concentrations of N, P, and Zn and had higher concentrations of P, Zn, Fe, Al, and Na in their vegetative body. The N:P ratios found (fertilized = 27.5 and non-fertilized = 33.8) suggest that W. sintenisii may also be phosphorous limited as are lowland epiphytes. Fertilized plants had slightly longer inflorescences, and more flowers per inflorescence, than non-fertilized plants, but their flowers produced nectar in similar concentrations and quantities. Fertilized plants produced more seeds per fruit and per plant. Frequency of flowering in two consecutive years was higher for fertilized plants than for controls, suggesting that fertilized plants overcome the cost of reproduction more readily than non-fertilized plants. These results provide evidence that TMCF epiphytic bromeliads are nutrient limited like their lowland counterparts.

Temperature-Dependent Fluctuation Of Stamen Number InCardamine hirsuta(Brassicaceae)

Floral organ number is often fixed within families, and the basic floral ground plan of Brassicaceae is well conserved. Cardamine hirsuta L. (Brassicaceae) shows variation in lateral stamen number, that is, zero to two lateral stamens. The aim of this study was to examine whether temperature conditions alter stamen number. Temporal changes in the frequency of flowers with zero, one, and two lateral stamens were assessed during the flowering periods of a natural population and a garden-transplanted population in Japan. We conducted an experiment to evaluate how temperature regimes during flowering (15°/15°C and 15°/5°C) alter the number of stamens. The proportion of flowers with zero lateral stamens increased in both the natural and the garden-transplanted population as the flowering season progressed. In the growth experiment, lateral stamen numbers fluctuated even within individual inflorescences, but the frequency of flowers with zero lateral stamens was higher in the high-temperature condition than in the low-temperature condition. Temperature-dependent phenotypic plasticity is likely to be the cause of the field-observed variation in lateral stamen number for C. hirsuta. Developmentally unstable but partly temperature-dependent production of the lateral stamen may be an indication of some epigenetic regulations as an underlying mechanism.

Pollination Requirements and the Foraging Behavior of Potential Pollinators of Cultivated Brazil Nut (Bertholletia excelsaBonpl.) Trees in Central Amazon Rainforest

This study was carried out with cultivated Brazil nut trees (Bertholletia excelsaBonpl., Lecythidaceae) in the Central Amazon rainforest, Brazil, aiming to learn about its pollination requirements, to know the floral visitors of Brazil nut flowers, to investigate their foraging behavior and to determine the main floral visitors of this plant species in commercial plantations. Results showed thatB. excelsais predominantly allogamous, but capable of setting fruits by geitonogamy. Nineteen bee species, belonging to two families, visited and collected nectar and/or pollen throughout the day, although the number of bees decreases steeply after 1000 HR. Only 16, out of the 19 bee species observed, succeeded entering the flower and potentially acted as pollinators. However, due to the abundance, flower frequency and foraging behavior of floral visitors, it was concluded that only the speciesEulaema mocsaryiandXylocopa frontaliscould be considered relevant potential pollinators.

Photoperiod Affects <i>in Vitro</i> Flowering in Wild Peanut <i>Arachis paraguariensis</i>

Arachis paraguariensis, a wild peanut species, is a potential experimental system for studying the molecular mechanisms of flowering in the genus Arachis. The present study was carried out to investigate the effect of photoperiod on in vitro reproductive behavior of five genotypes of A. paraguariensis. Day-lengths of 12, 16 and 24 h were tested to monitor in vitro flowering using growth chambers kept at 26?C ± 1?C and 60% ± 5% relative humidity under an illumination of 40 μmol?m–2?s–1. Flowering percentage of plantlets ranged from 35% to 93%, 20% to 75%, and 5% to 53% for 12, 16 and 24 h day-lengths, respectively. Genotype PI 262842 displayed the highest frequency of flowering under all the day-length treatments but in vitro flower bud initiation was delayed. The highest mean flowering percentage of 65% across all the genotypes for plantlets exposed to 12 h photoperiod is indicative that flowering induction actually occurred. The results presented in this paper provide evidence for photoperiodic flowering response as well as the occurrence of short day-length-enhanced flowering in A. paraguariensis.

Patterns of shallow seagrass (Posidonia oceanica) growth and flowering along the Tunisian coast

Shoot density and temporal patterns in leaf and rhizome production and other flowering parameters were assessed using a reconstruction technique (Lepidochronology) in Tunisian Posidonia oceanica meadows. Three meadows were sampled in October 2005 while seven in October 2007. Correlation between lepidochronological parameters and climate data (temperature and rainfall) was investigated. Shoot density in the ten meadows varied from 388±42shootsm−2 at El Kantaoui to 893±109shootsm−2 at Rafraf and showing significant differences between all sites. The meadows growing on hard substrate (Rafraf, Nabeul, Hergla cliff, Mahdia and Djerba) exhibited the highest shoots densities. Annual leaf formation rate showed a statistically significant difference between localities and years, indicating the importance of interannual growth fluctuations. The meadow in Tabarka produced two more leaves per year (8.3±0.7) than Rafraf ones (6.3±0.7). Vertical rhizome elongation rates differed significantly among sites, ranging from higher rates in Tabarka (average 13.72±2.26mmyear−1) to lower rates in El Kantaoui (average 5.01±1.13mmyear−1). The correlation analysis between seagrass growth and climate records showed significant correction between mean rainfall data and vertical rhizome elongation rates. Flowering was most prevalent in 2003. The maximum flowering frequency (FF) and shoot flowering probability (Pf) values were observed in Tabarka. The mean FF and Pf for all studied meadows were respectively estimated to 0.15±0.09 and 0.011±0.009. A large spatial–temporal variation in the flowering frequency occurred among populations and between years in P. oceanica meadows along the Tunisian coast.

Seed dispersal and seed banks in Aloe marlothii (Asphodelaceae)

Aloe marlothii flowers during dry winter months (July–September) and produces large numbers of wind dispersed seeds. Fire disturbance in a population of several thousand A. marlothii plants at Suikerbosrand Nature Reserve, Gauteng, permitted a series of seed dispersal experiments to be conducted. Germination trials indicated that seedling emergence decreased with increased distance from a well defined aloe stand and burn area margin, with seeds dispersed up to 25 m. Flowering frequency and total seed production were positively correlated with plant height, with seed production estimated to range from 26,000 to 375,000 seeds/plant. Although a large number of seeds are produced by flowering plants the survival rate of seeds did not extend beyond the following flowering season.

Micropropagation and in vitro flowering of endemic and endangered plant Ceropegia attenuata Hook

Factors affecting in vitro propagation were evaluated for Ceropegia attenuata Hook., an endemic and endangered plant having ornamental potential but a limited reproductive capacity. Rapid shoot multiplication from nodal explants was established using varying concentrations of cytokinins and auxins either alone or in combinations. The highest frequency of shoot induction was achieved when nodal explants were inoculated on Murashige and Skoog (MS) medium supplemented with 13.31 μM 6-benzylaminopurine with a mean of 12.9 ± 0.5 shoots per explant. High concentrations of TDZ (6.81–11.35 μM) and KN (6.78–11.61 μM) resulted in stunted and vitrified shoots. Factors implicated in the promotion of floral transition of the C. attenuata have been identified which are 4-amino-3, 5, 6-trichloropicolinic acid (picloram), 6-benzylaminopurine, sucrose and photoperiod. The highest frequency of flowering (100%) was obtained when axillary shoot explants were transferred to MS medium supplemented with picloram (4.14 μM) within 4 weeks of culture. Transfer of in vitro regenerated shoots to half strength MS medium with 2.46 μM indole-3-butyric acid (IBA) showed maximum root induction. The in vitro grown plantlets were successfully acclimatized in the glasshouse with 85% of survival and showed normal development. The developed protocol provided a simple, cost-effective approach for the conservation of endangered plant C. attenuata for replenishing its declining populations.

Sexual dimorphism of reproductive allocation at shoot and tree levels in Zanthoxylum ailanthoides, a pioneer dioecious tree

Sexual dimorphisms are often found in reproductive allocation and vegetative growth, and these sexual dimorphisms may lead to a reduction of subsequent reproductive allocation in woody dioecious species. However, in some species, female-biased reproductive allocation does not result in a reduction of subsequent reproductive allocation in females. To clarify the mechanisms underlying this phenomenon, we studied the dioecious tree Zanthoxylum ailanthoides Sieb. et Zucc., in which leafing and inflorescence development occur sequentially. Reproductive allocation and vegetative growth were examined in both sexes at the shoot and tree levels. At tree level, they were evaluated with respect to flowering frequency and annual tree-ring width over 5 years. Reproductive allocation per shoot in females was 1.7× that in males. The ratio of reproductive to total current-year shoots per tree in males was 1.2× that in females. Reproductive allocation in females exceeded that of males by a factor of 1.5 at the tree level, which was less than that at the shoot level, owing to modular integrity. Biased vegetative growth was not detected at the leaf, shoot, or tree level, suggesting that a compensatory mechanism is not employed by this species. The results support the conclusion that a species-specific phenophase sequence of Z. ailanthoides enables females to achieve consecutive reproductive allocation.

Demography of Sulfur Cinquefoil (Potentilla recta) in a Northern Rocky Mountain Grassland

AbstractSulfur cinquefoil is native to Eurasia and has invaded meadows and grasslands of North America. It occurs in intermountain valleys of the Rocky Mountains, including a nature reserve in northwest Montana that supports a mosaic of mesic fescue and xeric needlegrass grassland communities. We did tests to determine germination requirements, followed the fate of mapped sulfur cinquefoil from 1998 to 2005 to determine vital rates, and used a matrix modeling framework to analyze population-level dynamics. Sulfur cinquefoil plants were highly fecund; large plants produced > 10,000 seeds that require light for germination. The survivorship curve of the 1999 cohort suggested low juvenile but high adult survival. Simulations indicated that a 10% decline in survival would decrease population size more than a 10% decline in recruitment. Annual recruitment, growth of nonreproductive plants, survival, and flowering frequency of sulfur cinquefoil were all higher in the three needlegrass sample plots compared with the one fescue plot, and projected equilibrium sulfur cinquefoil populations were approximately 12 times larger in needlegrass than fescue grasslands. Our results suggest that biological control agents that negatively affect survival, such as root borers, might be more effective at controlling established sulfur cinquefoil populations than those that diminish seed production. Our results also suggest that sulfur cinquefoil might have more potential to become dominant in xeric grasslands and demonstrate the need for doing multiple demographic studies over a variety of habitats because the same species will respond differently in different habitats.

Population structure, growth rates and spatial distribution of two dioecious tree species in a wet forest in Puerto Rico

Abstract:Dioecious plants often exhibit male-biased sex ratios and sexual differences in life history traits such as plant size, growth rate and frequency of flowering, which arise from the different costs of reproduction for male and female plants. In tropical dioecious species sexual differences in reproductive costs have been demonstrated for several subcanopy species, but few canopy dioecious trees have been studied. We recorded the sexual expression of c. 2600 trees of Cecropia schreberiana and Dacryodes excelsa, two canopy dioecious species, during several censuses over 2 y in a 16-ha plot located in ‘subtropical wet forest’ in the Luquillo Mountains, Puerto Rico. There were similar numbers of male and female trees of C. schreberiana but D. excelsa had a female-biased population. Cecropia schreberiana showed no differences in male and female diameter distributions or growth rates, suggesting that reproductive maturation and longevity are similar for both sexes. This lack of differences in size and growth rate in C. schreberiana may result from mechanisms to compensate for the higher cost of reproduction in females, no resource limitation related to its pioneer life-history, or similar male and female reproductive costs. In contrast, D. excelsa males were larger than females, probably because males grow slightly faster than females. This sexual difference in D. excelsa may reflect a higher cost of reproduction in females than in males. Spatial segregation of males and females into different habitats is not common in tropical forest and neither C. schreberiana nor D. excelsa males and females exhibited significant spatial segregation. The contrasting results for these two canopy species reflect their different life history strategies in this hurricane-affected forest.

Varietal Differences and Morphology of Cleistogamy in Soybean

ABSTRACTCleistogamy, the production of open (chasmogamous, CH) and closed (cleistogamous, CL) floral forms by one species, is present in soybean [Glycine max (L.) Merr.]. Soybean cultivars that originated from high latitudes generally have a strong tendency to produce CL flowers. The first objective of this study was to determine varietal differences in cleistogamy. The second objective was to observe morphological differences between CH and CL flowers. A total of 32 and 31 soybean cultivars (maturity groups 00 to II) were grown in fields at Tsukuba and Sapporo, Japan, respectively, in 2005. Flowers that were fertilized up to 5 d after anthesis were classified into either CH or CL. Frequency of CL flowers ranged from 0.0 to 100.0% in Tsukuba and 6.7 to 100.0% in Sapporo. Cultivars from Russia and Hokkaido generally had a high frequency of CL flowers, whereas those from the Tohoku region had a lower frequency. Average of mean temperatures for 1 wk before anthesis was negatively correlated with frequency of CL flowers. Growth chamber experiments were conducted using CL cv. Severnaya 4 and a CH cv. Toyosuzu under constant temperatures of 25°C to eliminate temperature effects. Frequency of CL flowers in Severnaya 4 and Toyosuzu was 33.7 and 92.8%, respectively, suggesting involvement of genetic factors. At the same developmental stage, CL flowers had shorter sepal, petal, and stamen than CH flowers. There was no distinct morphological change in floral organs between CH and CL flowers except for length of the organs.

Bolting and flowering control in sugar beet: relationships and effects of gibberellin, the bolting gene B and vernalization

Bolting, the first visible sign of reproductive transition in beets (Beta vulgaris), is controlled by the dominant bolting gene B (B allele), which allows for flowering under long days (LDs, >14 h light) without prior vernalization. The B-locus carries recessive alleles (bb) in sugar beet (Beta vulgaris L. spp. vulgaris), so that vernalization and LDs are required for bolting and flowering. Gibberellin growth hormones (GAs) control stem elongation and reproductive development, but their role during these processes in sugar beet is not defined. We aimed to investigate the involvement of GAs in bolting and flowering in sugar beet, and also its relationship with the vernalization requirement as defined by the B-gene. Plants segregating for the B allele were treated with exogenous GA(4) under inductive (16 h light) and non-inductive (8 h light) photoperiods, with and without prior vernalization treatment. A co-dominant polymerase chain reaction (PCR) marker was used to genotype the B-gene locus. Bolting and flowering dates were scored, and bolt heights were measured as appropriate. Analysis of variance was used to determine the effects and interactions of GAs, the B allele and vernalization on bolting and flowering. The effects of the B allele on bolting were also verified in the field. Application of GAs or the B allele could initiate bolting independently. When the B allele was absent, the applied GAs promoted stem growth, but did so only in vernalized plants, irrespective of photoperiod. Under LDs, bolt height before flowering in plants carrying the B allele (BB; Bb) was not significantly influenced by GAs. The timing and frequency of flowering were influenced by the B allele without interactive effects from GAs. In sugar beet, GA acts independently of the B allele and photoperiod to induce bolting. Vernalization enables GA action independently of the B allele; hence, the dominant B allele may not directly participate in vernalization-induced bolting.

Ecological study on Dobera glabra Forssk. at Jazan region in Saudi Arabia

Research on Dobera glabra Forssk is very little. A study was carried out in Jazan (south western Saudi Arabia) on the ecology of D. glabra. The species was distributed over a large area, but with decreasing density towards the Red Sea coast. Generally, the density of the species is very little. This is combined with 0% survival of seedlings and samplings after 8 months made the species existence endangered and urgent intervention is required to conserve it. Although the frequency of flowering was normal, nevertheless fruiting is extremely little (0.29%). The species regenerates well with seeds without any pretreatment, however, the seedlings require immediate protection from grazing and other human activities. Seedling growth is extremely slow. All attempts of vegetative propagation of D. glabra from cuttings, failed despite the use of suitable rooting media and growth hormones. Due to the importance of the species as a fodder during the dry season where most other resources are unavailable and as famine food for humans, further research is needed on how to conserve D. glabra. Key words: Dobera glabra, germination, vegetative propagation, grazing, famine, foods, fodder.

Morphological variation and floral abnormalities in a trigger plant across a narrow altitudinal gradient

AbstractLocal adaptation in alpine plants has been demonstrated across wide altitudinal gradients, but has rarely been examined across the alpine‐to‐montane transition that often encompasses only a few hundred metres. Here we characterize morphological variation in leaf and floral characteristics of the trigger plant Stylidium armeria along a narrow altitudinal gradient in the Bogong High Plains in Victoria. Across this gradient, which encompasses the high‐elevation limit of this species, linear changes were found for floral scape height, leaf length and flower number. All these traits decreased with increasing altitude, whereas the frequency of abnormal flowers increased. When plants were grown in a common garden environment, an altitudinal pattern for flower abnormalities was no longer detected. However, altitudinal patterns for leaf length and scape height were maintained, albeit weaker than in the field. This indicates heritable variation for these morphological traits; the altitudinal patterns are likely to reflect the effects of selection by environmental factors that vary with altitude. Selection pressures remain to be identified but have generated both cogradient and countergradient patterns of variation.