Seasonal pattern of dry matter allocation in Dactylorhiza lapponica (Orchidaceae) and the relation between tuber size and flowering

A population of the tuberous orchid Dactylorhiza lapponica was sampled from June 2000 to June 2001 in the Sølendet Nature Reserve, Central Norway. Dry matter of aerial shoots, old tubers and new (replacement) tubers was measured, as well as reproductive status during 1999–2001. The biomass of the new tuber was found to continue to increase after the assimilation from photosynthesis had ceased in August. It is suggested that the increase is caused by mycotrophic activity and reallocation of nutrients from the aerial shoots. There was a clear relationship between tuber size and flowering behaviour. Individuals with flower primordia had the largest replacement tuber, whereas those that flowered in the sampling season or remained vegetative throughout 1999–2001 had the smallest. Individuals that flowered in the sampling season had the largest old tuber. Those, which had not flowered for at least two years, but had developed flower primordia, had the second largest, and those that remained vegetative throughout 1999–2001 had the smallest one. Individuals with a replacement tuber less than 0.22 g in October, have a very low probability of flowering the following season. Flowering entails a cost in terms of reduced biomass of the replacement tuber compared to vegetative individuals with old tubers of similar size. Allometric analyses revealed that above-ground biomass and biomass of replacement tubers increased with the biomass of old tubers in vegetative individuals. For generative individuals, however, above-ground biomass was only weakly related to below-ground biomass.     

Vegetation dynamics following trampling in grassland and heathland in Sølendet Nature Reserve, a boreal upland area in Central Norway

Trampling is recognised as a cause of disturbance in grassland and heathland vegetation along two public nature trails in Sølendet nature reserve in central Norway. The effects of trampling by visitors and of controlled trampling were monitored over a period of 5–7 years in permanent plots. A retrogressive development was recorded as vegetation cover and height were reduced and a substantial loss of species richness and biomass took place. Some species, mainly graminoids such as Agrostis capillaris and Carex vaginata , initially appeared to be more tolerant, but were eventually reduced as well. Low, geophytic and prostrate habits of growth and hardy leaf tissues seemed to be beneficial for tolerance to trampling. Moist grassland and lichen-dominated heathland were more vulnerable to trampling than dry grassland. Even though 350–1500 visitors walked through the permanent plots along the trails each summer, effects on the soil surface remained moderate and only a minor furrow was visible on the ground.     

Effect of season of burn on shoot recovery and post‐fire flowering performance in the resprouter Stirlingia latifolia R. Br. (Proteaceae)

Abstract Stirlingia latifolia R. Br. is a proteaceous undershrub that is widespread in open woodlands and heathlands of the south‐west botanical province of Western Australia where it is subject to frequent fires, both natural and the result of fuel‐reduction burns. Shoots are completely destroyed by fire but regenerate rapidly by resprouting numerous new shoots from the root crown. Flowering is strongly triggered by fire with only sparse flowering in fire‐free periods. A study was undertaken to compare regrowth and flowering in populations of S. latifolia burnt in summer or autumn with populations burnt in spring as well as in unburnt population. Post‐fire flowering was recorded in 92% of plants burnt in summer/autumn compared with 73% of plants burnt in spring and less than 3% in populations that had not been burnt for more than 2 years. Plants burnt in summer/autumn resprouted an average of 8.5 shoots from their root crown, of which 93% developed an inflorescence. In contrast, spring‐burnt plants averaged only 5.9 shoots per plant with only 64% of these bearing an inflorescence. Ability to produce flowers was found to be related to plant age, with young individuals producing fewer or no inflorescences following spring burns in comparison with the more prolific flowering of similarly aged individuals following summer/autumn burns. Summer/autumn‐burnt plants also produced significantly longer inflorescence‐bearing shoots bearing a greater numbers of flower heads than those burnt in spring. Possible explanations for these results are given in the present report.     

Vegetation dynamics following trampling in rich fen at Sølendet, Central Norway; a 15 year study of recovery

In Sølendet nature reserve in the upper boreal of central Norway, the effects of controlled trampling from 1977 to 1981 were observed in four rich fen localities. The vegetation recovery was monitored on permanent plots on 3–4 occasions during the period 1981–1995. During trampling the vegetation cover was reduced and bare peat increased, particularly in a wet fen expanse locality. Woody species and herbs disappeared or were considerably reduced in cover, while some graminoids (e.g. Carex spp. and Eriophorum angustifolium ) and bryophytes (e.g. Campylium stellatum and Scorpidium cossonii ), appeared to be quite tolerant. Equisetum palustre and Eriophorum angustifolium increased in cover on two tracks. Several bryophytes survived trampling, but Sphagnum warnstorfii was eradicated. Campylium stellatum and Tomentypnum nitens were able to increase after the decrease in S. warnstorfii . The recovery was dependent on which species were present at the outset and which species arrived early. Further development seemed to depend largely on the species' capacity for rapid increase in cover. Eventually, the more vulnerable dominants of the untrampled vegetation (e.g. Thalictrum alpinum, Trichophorum cespitosum and Sphagnum warnstorfii ) increased in abundance. After 15 years the tracks still contained fewer species and had less vegetation cover than the surroundings.     

Large delay in flowering in continental versus coastal populations of a Mediterranean shrub, <Emphasis Type="Italic">Globularia alypum</Emphasis>

Globularia alypum is a perennial shrub typical of western Mediterranean thermophilous shrublands. Nine populations of G. alypum located in different localities of Catalonia (NE Spain) were surveyed for flowering phenology. Flower-head buds were present in all the populations in July. Flowering time in the area spans from the late summer–early autumn to the next spring depending on the populations; there are two groups of populations, early and late flowering. Early populations grow mostly in coastal localities and flower from September to November, whereas late flowering populations grow in inland localities and flower from February to April. The flowering order of the populations correlated with minimum temperature of most months except the warmest ones, and correlated with maximum and mean temperatures of the coldest months. Correlations were similar when tested with annual climate. The flowering order also correlated with the thermic interval for most months except the coldest and with the index of continentality. Early populations alone did not present correlations with any variable, whereas late populations alone correlated similarly to all populations together. Flowering order did not correlate with precipitation. Late populations are proposed to be regulated by temperature according to our results whereas early populations could be regulated by timing in precipitation after summer drought, according to published results. We discuss the possibilities of the two flowering patterns, early and late, being due to phenotypic plasticity or to genetic adaptation to local climates. We also discuss the consequences at the plant and ecosystem level of climate warming causing shifts from late to early patterns, a possibility that is likely in the warmest of the late populations if flowering is modulated phenotypically.     

Habitat type plays a greater role than livestock grazing in structuring shrubsteppe plant–pollinator communities

Livestock grazing is a widespread grassland disturbance and can negatively impact biodiversity. Pollinators constitute a vital component of grassland ecosystems, but the impact of grazing on pollinator diversity has seldom been evaluated in North America. We assessed vegetation structure, and pollinator and flowering plant abundance, richness, diversity, and community composition in four pairs of spring-grazed/ungrazed sites in south-central British Columbia, Canada. We also investigated whether pollinator or floral communities differed between the two threatened shrubsteppe habitat types we sampled—antelope-brush and big sagebrush shrubsteppe. Pan-trapping surveys captured 5907 bees, flies, beetles, wasps and butterflies constituting 253 species. We found that the percent cover of shrubs and bare soil increased with grazing, while the height of grasses and forbs decreased. In contrast, pollinator and flowering plant abundance, richness, diversity, and community composition were not significantly affected by grazing. Flowering plant and pollinator community composition did differ significantly between shrubsteppe habitats. Our results indicate that grasslands in North America, when managed responsibly, can maintain pollinator and flowering plant diversity under grazing pressure. The continued effort of land managers to balance ecological integrity and economic viability will be important for the conservation of grassland pollination systems.     

Flowering frequency in a small population of Gymnadenia conopsea-a five year study

This investigation evaluates the usage of genetic markers, microsatellites, to distinguish and re-identify individual plants in a population of the orchid Gymnadenia conopsea. The study also illustrates the problem in estimating the size of a population from single year sampling as individuals can rest underground or occur in vegetative states; information extremely important for the understanding of population dynamics as well as providing information for conservation management. The total population size was, based on information from microsatellite loci, estimated to 84 individuals and vastly larger than the annual number of flowering plants (mean 31.4 individuals/year). Flowering frequency varied from 24–49%, 53 individuals flowered once, five individuals were flowering four years and a single individual was flowering five years. A common pattern was one or two flowering periods followed by a non-flowering period. The observed number of alleles and the observed and expected heterozygosity varied among loci, although allele frequencies and genotype frequencies did not vary significantly among years.     

Flowering and fruiting phenology in the coastal shrublands of Doñana,south Spain

Flowering and fruiting phenological patterns at the individual-, population-, and community level were studied in a southern Spanish scrub community composed of 30 shrub species. Few individuals of any species produced a high number of flowers. Intrapopulation deviation in the peak time of flowering showed a strong and positive skewness. Relative flowering duration, however, displayed a virtually normal distribution. Generally, species flowering in spring have a short flowering time, while species flowering earlier or later in the year show significantly longer flowering periods. Species were in bloom throughout the year, but there was a major peak during spring and two lesser ones in autumn and early summer. Shallow rooting taxa in typically mediterranean genera displayed a strategy of spring flowering and summer fruiting. Summer and autumn flowering occurred among heath-like shrubs of relatively wet places, and forest-associated, vertebrate-dispersed species which commonly have underground storage organs. Species with ripe fruits presented two peaks, the major one during the summer including the majority of taxa with seeds dispersed by non-vertebrate agents. There was a minor fruiting peak in autumn dominated by taxa that rely on vertebrates for dispersal. The complex seasonal patterns observed are interpreted in relation to environmental conditions and physiological constraints on species living in a highly seasonal climate.     

Redundancy, synergism, and active inhibitory range of non-host volatiles in reducing pheromone attraction in European spruce bark beetle Ips typographus

Brandt's voles ( Microtus brandti ) are small native mammals that inhabit the grasslands of Inner Mongolia, China. The species is considered a pest, particularly during population outbreaks, which have increased in frequency since 1970 from 1 every 7 years to 1 every 3 to 5 years. Using historical records taken between 1948 and 1998, we found that there was significant correlation between years for which the monthly averages of the Southern Oscillation Index (SOI) were consistently high, and years in which outbreaks occurred. Also there was a tendency for outbreaks not to occur in years with precipitation above or below average. For some years at some sites, annual or biannual estimates are available for the density of Brandt's vole populations. We found that the seasonal rate of increase over the non-breeding season from autumn to spring was negatively correlated with the density in autumn. The rate of increase over the breeding season from spring to autumn was independent of the density in spring but instead, reflects the species' preference for habitat with short, sparse grass; populations do not persist in highly degraded grasslands or in tall, dense grassland. The link between outbreaks and climatic indices, and the numerical response of Brandt's voles to particular habitat characteristics, suggest that current grazing intensity tends to maintain grass at low height in years with average precipitation. The substantial increase in livestock numbers over the last 50 years appears to have increased the number of years when the balance of grazing and plant growth favours high rates of increase in Brandt's vole populations, and hence, there has been an increase in the frequency of outbreaks.     

Genetic variation in flowering phenology and reproductive performance in a Mediterranean high‐mountain specialist,Armeria caespitosa (Plumbaginaceae)

Adaptive responses to past climate change may play an important role in the persistence of high‐mountain plants, which are vulnerable to global warming. Armeria caespitosa is a high‐mountain plant, endemic to the Iberian Central Range. Differences in abiotic environment along the elevational gradient impose two opposing stress gradients (i.e. water stress and duration of the growth season) on the species. Furthermore, the species is found in two interspersed, contrasting microhabitats (rocky outcrops and dry cryophilic grasslands) that have different effects on plants depending of the elevation. As a result of this, the species shows great among‐population variation in many reproductive and vegetative traits. We used a common garden approach to determine whether this phenotypic variation has a genetic basis or is the result of plastic responses shaped by heterogeneous environmental conditions. Plants from the high‐elevation edge and dry cryophilic grasslands flowered earlier and produced more viable fruits but were smaller. These results confirm that among‐population variation in flowering phenology and reproductive performance traits in A. caespitosa is partially genetically based. The results also show that the stronger selection response in favour of early‐flowering individuals in populations at the low‐elevation edge did not correspond with the greater proportion of early‐flowering individuals. Genetic variability associated with flowering onset may be relevant in coping with the impacts of ongoing global warming. © 2014 The Linnean Society of London, Botanical Journal of the Linnean Society, 2014, 176 , 384–395.     

Flowering phenology: An example of relaxation of natural selection?

Flowering phenology has normally been viewed as fundamental to a plant species' reproductive ecology. Researchers in the field have emphasized the adaptive importance of flowering at a particular time relative to other individuals in the population, or other species in the community. An alternative view, however, is that flowering phenology is a trait that may not be under strong selection, and this may have allowed some variation to appear in populations by chance.     

Plant traits and functional types in response to reduced disturbance in a semi‐natural grassland

Abstract. Question: How do functional types respond to contrasting levels of herbage use in temperate and fertile grasslands? Location: Central France (3°1’E, 45°43’N), 870 m a.s.l. Methods: Community structure and the traits of dominant plant species were evaluated after 12 years of contrasted grazing and mowing regimes in a grazing trial, comparing three levels of herbage use (high, medium and low). Results and Conclusions: Of 22 measured traits (including leaf traits, shoot morphology and composition, phenology), seven were significantly affected by the herbage use treatment. A decline in herbage use reduced individual leaf mass, specific leaf area and shoot digestibility, but increased leaf C and dry matter contents. Plants were taller, produced larger seeds and flowered later under low than high herbage use. Nine plant functional response types were identified by multivariate optimization analysis; they were based on four optimal traits: leaf dry matter content, individual leaf area, mature plant height and time of flowering. In the high‐use plots, two short and early flowering types were co‐dominant, one competitive, grazing‐tolerant and moderately grazing‐avoiding, and one grazing‐avoiding but not ‐tolerant. Low‐use plots were dominated by one type, neither hardly grazing‐avoiding nor grazing‐tolerant, but strongly competitive for light.     

Phenology and phenotypic natural selection on the flowering time of a deceit-pollinated tropical orchid, Myrmecophila christinae

BACKGROUND AND AIMS: Flowering phenology is described and the effect of flowering time on pollination success is evaluated in the deceit-pollinated tropical orchid, Myrmecophila christinae. It was expected that, due to this species' deceit pollination strategy and low observed pollinator visit rate, there would be a higher probability of natural selection events favouring individuals flowering away from the population flowering peak. METHODS: The study covers two consecutive years and four populations of M. christinae located along the north coast of the Yucatán Peninsula. For phenological and pollination success data, a total of 110 individuals were monitored weekly in 1998, and 83 individuals in 1999, during all the flowering and fruiting season. KEY RESULTS: The results showed significant differences in the probability of donating and receiving pollen throughout the flowering season. The probability of receiving or donating pollen increased the further an individual flowering was from the flowering peak. Regression analysis showed directional and disruptive phenotypic natural selection gradients, suggesting the presence of selection events unfavourable to flowering during flowering peak, for both male success (pollen removal) and female success (fruit production). However, the intensity and significance of the natural selection events varied between populations from year to year. The variation between seasons and populations was apparently due to variations in the density of reproductive individuals in each population and each season. CONCLUSIONS: As in other deceit-pollinated orchids, natural selection in M. christinae favours individuals flowering early or late in relation to population peak flowering. However, results also suggested a fluctuating regime of selective events act on flowering time of M. christinae.     

Flowering phenology in natural populations of Iris pumila

In the present study, I examined flowering phenology of dwarf bearded ins, Iris pumila , using naturally occurring clones (three sites, four microsites) and clones transplanted between two sites representing two habitats Naturally occurring clones in contrasting habitats and microsites differed significantly in phenology, with exposition of the site or microsite being the most important Genotypes from more exposed habitats flowered earlier in both habitats and these differences were statistically significant Patterns of between-habitat and between-population differences were stable over years even though years differed markedly in the flowering onset Within-population genetic variability for flowering phenology was also found to be significant Although clones with dark-colored flowers tended to flower earlier in all habitats and microsites I failed to detect statistically significant differences in flowering time among color morphs Flowering phenology in I pumila is highly susceptible to environmental variability, but this factor has not prevented population divergence in flowering time Between-habitat differences in flowering time turned out to be a result of both phenotypic plasticity of individuals and genetic differentiation of populations     

Seasonal Patterns of Flowering and Fruiting in a Dry Tropical Forest in Jamaica1

Tropical dry forests occupy more area and are more endangered than rainforests, yet their regeneration ecology has received less study and is consequently poorly understood. We recorded the flowering and fruiting phenology of a tropical dry forest in Jamaica over a period of 26 mo within ten 15 × 15‐m plots. Community‐wide recruitment reached a maximum in the wet season, whereas no recruitment occurred during the dry season. We observed a unimodal peak in rainfall and fruit production, and the periodicity and intensity of seed production were significantly correlated with rainfall seasonality (the optimal time for germination). Flowering at the community and system levels lagged behind a significant increase and subsequent decrease in rainfall by 7 and 3 mo, respectively, indicating that the dominant factor controlling flowering periodicity is the passage of the major (4‐mo long) rainy season and changes in soil moisture conditions. Fruiting lagged behind flowering by 2 mo and a significant increase in fruiting occurred 2 mo prior to a significant increase in rainfall. At the population level, a correspondence analysis identified a major dichotomy in the patterns of flowering and fruiting between species and indicated two broad species groups based on their time of peak fruiting and the number of times they were in fruit. These were either individuals which were usually in peak fruit 1–2 mo prior to the start of the major rainy season or those that were in fruit more or less continuously throughout the year with no peak fruiting time. This study supports the view that seasonal variation in rainfall and hence soil water availability constitutes both the proximate and the ultimate cause of flowering periodicity in tropical dry forests.     

Effect of flowering on vegetative growth and further reproduction in

Flowering intensity and plant size were monitored in 155 Festuca novae-zelandiae individuals over four years to determine if trade-offs exist between inflorescence production and vegetative growth, and between inflorescence production in different years. Less than half of the population flowered in any one year, 36% of individuals did not flower at all, and only 17% flowered in all four years of the study. Mean number of inflorescences per individual per year varied from 1.54 to 5.53 (maximum = 85). No trade-offs were detected between flowering frequency and intensity; individuals that flowered more frequently also produced more inflorescences in each flowering episode. No trade-off was detected between current and future reproduction, rather flowering intensity was positively correlated between years. Growth, as measured by diameter increment, was positively related to flowering frequency and flowering intensity, both across all individuals studied and within 1m x 1m plots. The presence of a positive relationship between growth and reproduction within plots argues against meso-scale variability in environment factors being the cause of the results from analyses involving all individuals. Clearly reproduction in F. novae-zelandiae does not incur a marked cost in growth or future reproduction. The assumptions underlying theoretical expectations of such trade- offs may not be valid for long-lived clonal plants such as F. novae-zelandiae.     

Flowering phenology and wind-pollination efficacy of heterodichogamous Juglans mandshurica (Juglandaceae)

BACKGROUND AND AIMS: Heterodichogamy differs from normal dichogamy, in that it involves two mating types (protogyny and protandry) that occur at a 1 : 1 ratio in a population. Flowering phases of the two mating types are synchronized and reciprocal, which was considered to ensure between-type outcrossing. This study aims to quantify the flowering pattern and pollination efficacy in Juglans mandshurica, a wind-pollinated heterodichogamous tree. METHODS: The pattern of flowering phenology was monitored within individual trees and pollen traps were used to measure air-borne pollen loads during the spring in 2003 and 2004. Pollen longevity was determined by staining technique. Also a pollen supplementation experiment was performed in 2004 to assess pollen limitation of fruit production. KEY RESULTS: There was no overlap between sexual functions within individual trees. Flowering periods of the two mating types were reciprocal and synchronous in both 2003 and 2004. Air-borne pollen loads were large, and protogynous and protandrous individuals each produced a high pollination peak, consistent with the two blooming periods. Maximum pollen longevity was about 4 h for protandrous individuals, and 3 h for protogynous individuals. Pollen supplementation did not increase fruit production in either protogynous or protandrous individuals. CONCLUSIONS: Heterodichogamous flowering in Juglans mandshurica effectively avoids selfing, promotes between-type outcrossing, and leads to efficient pollination in a natural population.     

Population dynamics of the climate‐sensitive endangered perennial Ferula sadleriana Ledeb. (Apiaceae)

Ancient plant species surviving in isolated small populations are particularly vulnerable to extinction, therefore understanding their population dynamics is necessary for conservation. The iteroparous perennial relic endemic Ferula sadleriana Ledeb. (Apiaceae) is restricted to seven distant localities in the Carpathian Basin, where it inhabits rocky hills. We monitored the species' largest population on the Pilis Hill, Hungary, over 14–19 years (depending on trait) between 1979 and 2010, and relationships were sought between climatic properties and population attributes. The population of 4000 ± 1509 emergent individuals underwent large interannual fluctuations, with the vegetative stage displaying sevenfold and the reproductive stage twenty‐eight‐fold differences. Spring and early summer precipitation had a marked influence on abundances and seed set. Alternating years of high and low counts of reproductive plants suggest costs of reproduction that most probably incur prolonged dormancy and retrogression to the vegetative stage. Seed set was positively influenced by number of reproductive plants over years and by plant size within a year. Ungulates nullify yearly reproductive output by grazing on reproductive individuals. This is particularly intense in dry summers, when reproductive output is already low. The strong precipitation response of abundance, absence of clonal propagation and soil seed bank, and geographical isolation of the populations place F. sadleriana at considerable risk under an increasingly variable and extreme climate. Management should seek to maintain the species' original habitat mosaic (potentially compensating for climate variation), minimize grazing damage and anthropogenic disturbance, and establish ex situ conservation programs to provide propagules for eventual reintroduction.     

The role of individual variation in flowering and pollination in the reproductive success of a crepuscular buzz-pollinated plant

Background and AimsPlant individuals within a population differ in their phenology and interactions with pollinators. However, it is still unknown how individual differences affect the reproductive success of plants that have functionally specialized pollination systems. Here, we evaluated whether plant individual specialization in phenology (temporal specialization) and in pollination (pollinator specialization) affect the reproductive success of the crepuscular-bee-pollinated plant Trembleya laniflora (Melastomataceae).MethodsWe quantified flowering activity (amplitude, duration and overlap), plant–pollinator interactions (number of flowers visited by pollinators) and reproductive success (fruit set) of T. laniflora individuals from three distinct locations in rupestrian grasslands of southeastern Brazil. We estimated the degree of individual temporal specialization in flowering phenology and of individual specialization in plant–pollinator interactions, and tested their relationship with plant reproductive success.Key Results Trembleya laniflora presented overlapping flowering, a temporal generalization and specialized pollinator interactions. Flowering overlap among individuals and populations was higher than expected by chance but did not affect the individual interactions with pollinators and nor their reproductive success. In contrast, higher individual generalization in the interactions with pollinators was related to higher individual reproductive success.ConclusionsOur findings suggest that individual generalization in plant–pollinator interaction reduces the potential costs of specialization at the species level, ensuring reproductive success. Altogether, our results highlight the complexity of specialization/generalization of plant–pollinator interactions at distinct levels of organization, from individuals to populations, to species.