Consequences of variation in flowering phenology for seed head herbivory and reproductive success in Erigeron glaucus (Compositae)

Summary We examined the relationship between flowering phenology, reproductive success (seed production only), and seed head herbivory for 20 similarly sized clones of Erigeron glaucus growing at Bodega Bay Reserve, northern California, USA. Although clones tended to reach peak flowering on the same date, they differed in the proportion of their total flowers produced around that date (flowering synchrony). Clones also differed in the number and density of flower heads presented at any one time to pollinators and herbivores (floral display). Both of these characteristics had consequences for herbivory and plant reproductive success. The proportion of flower heads damaged by insect herbivores was greater for clones that concentrated flowering activity during the main flowering period for the population as a whole (high synchrony) compared to clones that spread flowering out temporally. The primary reason for this result was that clones with low flowering synchrony produced a significant proportion of their flower heads during the fall and therefore, escaped attack by the tephritid fly, Tephritis ovatipennis. Clones with intermediate synchrony had lower seed success (total number of viable seeds produced over the year) than clones with either low or high synchrony. The proportion of flower heads damaged by insect herbivores and number of tephritid flies reared from flower heads were both negatively correlated to floral display while seed head mass and germination rates were positively related to display. Thus, clones which produced dense floral displays were favored both in terms of reduced herbivory and increased successful seed production.     

Effects of season and population size on pollination and reproductive output in a Mediterranean shrub

• Pollinator guilds may change throughout extended flowering periods, affecting plant reproductive output, especially in seasonal climates. We hypothesised a seasonal shift in pollinator guild and an autumn reduction in pollinator abundance, especially in small and sparse populations.
• We recorded pollinator identity, abundance and behaviour in relation to flower density from plant to population throughout the extended flowering of Ononis tridentata. We evaluated female reproductive output by recording pollination success and pre‐dispersal seed predation in eight populations of contrasting size and density. Offspring quality was also characterised through seed weight and germination.
• A diverse guild of insects visited O. tridentata in spring, while only Apis mellifera was observed in autumn. Visitation frequency did not vary seasonally, but the number of flowers per foraging bout was lower, and seeds were heavier and had a higher germination rate in autumn. Plant and neighbourhood flowering display were not related to pollinator visitation frequency or behaviour. However, the rate of fertilised ovules, seed set and autumn flowering display size were positively related to population density.
• The maintenance of pollination in autumn enhances the reproductive performance of O. tridentata due to higher quality of autumn seed, and to a large reduction in seed predator pressure. We also suggest that observed changes in pollinator behaviour could be one of the processes behind seasonal variation in seed performance, since geitonogamous crosses were less likely to occur in autumn.

     

Co-adaptation of seed dormancy and flowering time in the arable weed Capsella bursa-pastoris (shepherd's purse)

Background and Aims

The duration of the plant life cycle is an important attribute that determines fitness and coexistence of weeds in arable fields. It depends on the timing of two key life-history traits: time from seed dispersal to germination and time from germination to flowering. These traits are components of the time to reproduction. Dormancy results in reduced and delayed germination, thus increasing time to reproduction. Genotypes in the arable seedbank predominantly have short time to flowering. Synergy between reduced seed dormancy and reduced flowering time would create stronger contrasts between genotypes, offering greater adaptation in-field. Therefore, we studied differences in seed dormancy between in-field flowering time genotypes of shepherd''s purse.

Methods

Genotypes with early, intermediate or late flowering time were grown in a glasshouse to provide seed stock for germination tests. Secondary dormancy was assessed by comparing germination before and after dark-incubation. Dormancy was characterized separately for seed myxospermy heteromorphs, observed in each genotype. Seed carbon and nitrogen content and seed mass were determined as indicators of seed filling and resource partitioning associated with dormancy.

Key Results

Although no differences were observed in primary dormancy, secondary dormancy was weaker among the seeds of early-flowering genotypes. On average, myxospermous seeds showed stronger secondary dormancy than non-myxospermous seeds in all genotypes. Seed filling was similar between the genotypes, but nitrogen partitioning was higher in early-flowering genotypes and in non-myxospermous seeds.

Conclusions

In shepherd''s purse, early flowering and reduced seed dormancy coincide and appear to be linked. The seed heteromorphism contributes to variation in dormancy. Three functional groups of seed dormancy were identified, varying in dormancy depth and nitrate response. One of these groups (FG-III) was distinct for early-flowering genotypes. The weaker secondary dormancy of early-flowering genotypes confers a selective advantage in arable fields.     

Preference of an insular flying fox for seed figs enhances seed dispersal of a dioecious species

Interactions among multiple species form complex networks of interdependences and are considered primary factors in the generation and maintenance of biodiversity. Pteropodid bats are keystone species that provide important ecosystem services of pollination and seed dispersal in the tropics and subtropics. In this study, we investigated the utilization and preference of food resources by the insular frugivorous flying fox Pteropus dasymallus. We found that fig species constituted the major portion of the diet of the flying fox (94.6%). When foraging, the flying fox preferred seed figs from female trees over gall figs from male trees in functionally dioecious fig species. Germination experiments showed a significantly higher percentage of germination for fig seeds in feces than those from pellets and ripe figs (feces: 80.2%, pellets: 23.4%, ripe figs: 32.9%). Considering the active selection of seed figs and avoidance of gall figs by foraging flying foxes, we suggest that the abundance of seed figs accurately represents food availability for dioecy. This preference for seed figs or viable seeds can effectively promote the survival of pollinating wasps and might reinforce the evolution of dioecism in figs. In addition, the effects of gut passage on seed germination, in combination with the capacity of flying foxes to travel long distances, may substantially contribute to the efficiency of flying foxes as seed dispersers.     

Are mismatches the norm? Timing of flowering,fruiting, dispersal and germination and their fitness effects in Frangula alnus (Rhamnaceae)

The close morphological and temporal links between phases of plant growth and reproduction call for integrated studies incorporating several reproductive phases from flowering to recruitment, and associated plant‐animal interactions. Phenological strategies, as well as plastic phenological response to climate change, incorporate complex interactions between developmental constraints, pollination and seed dispersal. Relationships between reproductive phenology and components of fitness were studied for two years in the north‐temperate, self‐incompatible, insect‐pollinated, and bird‐dispersed shrub Frangula alnus (Rhamnaceae). Fruit set, dispersal, germination and juvenile survival, as well as seed mass and juvenile size were measured in relation to flowering, fruiting and germination time. The results suggest that effects of flowering and fruiting time prevailed in subsequent phases, to some extent as far as to the juvenile phase, but effects of timing were complex and had partly opposing effects on different fitness components. Early flowers had higher fruit‐set and experiments indicated that synchronous peak flowering increased fruit‐set, but later flowers had higher seed mass. Peak fruiting was not associated with peak dispersal. Late fruits derived from late flowers promoted dispersal. Juvenile recruitment was enhanced by increasing seed size. We conclude that the phenology of flowering and fruiting in F. alnus comprises several features, each with different and sometimes counteracting effects on fitness components. From a general perspective, this result implies that we should not expect to find finely tuned matches in timing specifically between flowering and pollinators, and fruiting and seed dispersing birds.     

Characterizing the interaction between the bogus yucca moth and yuccas: do bogus yucca moths impact yucca reproductive success?

Yucca moths are most well known for their obligate pollination mutualism with yuccas, where pollinator moths provide yuccas with pollen and, in exchange, the moth larvae feed on a subset of the developing yucca seeds. The pollinators, however, comprise only two of the three genera of yucca moths. Members of the third genus, Prodoxus, are the bogus yucca moths and are sister to the pollinator moths. Adult Prodoxus lack the specialized mouthparts used for pollination and the larvae feed on plant tissues other than seeds. Prodoxus larvae feed within the same plants as pollinator larvae and have the potential to influence yucca reproductive success directly by drawing resources away from flowers and fruit, or indirectly by modifying the costs of the mutualism with pollinators. We examined the interaction between the scape-feeding bogus yucca moth, Prodoxus decipiens, and one of its yucca hosts, Yucca filamentosa, by comparing female reproductive success of plants with and without moth larvae. We determined reproductive success by measuring a set of common reproductive traits such as flowering characteristics, seed set, and seed germination. In addition, we also quantified the percent total nitrogen in the seeds to determine whether the presence of larvae could potentially reduce seed quality. Flowering characteristics, seed set, and seed germination were not significantly different between plants with and without bogus yucca moth larvae. In contrast, the percent total nitrogen content of seeds was significantly lower in plants with P. decipiens larvae, and nitrogen content was negatively correlated with the number of larvae feeding within the inflorescence scape. Surveys of percent total nitrogen at three time periods during the flowering and fruiting of Y. filamentosa also showed that larval feeding decreased the amount of nitrogen in fruit tissue. Taken together, the results suggest that although P. decipiens influences nitrogen distribution in Y. filamentosa, this physiological effect does not appear to impact the female components of reproductive success.     

Flower herbivory and seed predation in Silene vulgaris (Caryophyllaceae): effects of pollination and phenology

Pollination and seed predation were studied in Silene vulgaris populations during two seasons, one with much lower pollinator abundance than the other. Among the pollinators, noctuid moths of the genus Hadena also acted as seed predators. Nectar-foraging female moths oviposited in flowers, and their larvae consumed flowers and seed capsules.
Despite a lower percentage of pollinated flowers in the year of low pollinator abundance, similar numbers of flowers set fruit in both years, because fewer flower buds and flowers were eaten by Hadena larvae during the year of low pollinator visitation. The number of seed capsules preyed upon was also lower in the year with low pollinator abundance, resulting in a higher seed set. The positive correlation between the percentage of pollinated flowers and the percentage of seed capsules destroyed was also observed when comparing flowers opening in different parts of the season.
Early flowering plant individuals had the same pollination success but suffered higher seed predation than late flowering ones. Selection for maximized pollination success through synchronous flowering, is probably the main reason for the compressed flowering period in 5. vulgaris , but the high level of predation early in the season may further increase the reproductive success of synchronous flowering individuals.     

REPRODUCTIVE BIOLOGY OF ASTER CURTUS (ASTERACEAE), A PACIFIC NORTHWEST ENDEMIC

Aspects of the reproductive biology of Aster curtus were investigated to shed light on the current rarity of the species, which is endemic to grasslands of western Washington and Oregon. A bagging experiment showed that excluding insect pollinators significantly decreased the production of viable seeds. Where insects were allowed access, seed production by this perennial forb was not unusually low. Seeds of A. curtus exposed to light germinated over a wide range of temperatures, but few seeds germinated in the dark. Stratification improved germination. Aster curtus was shown to be a stress-tolerant species that grows very slowly under all conditions. Although seed production and germination do not appear to limit A. curtus, competition from other species probably restricts seedling recruitment in undisturbed communities. Habitat loss due to agriculture, urban expansion, and the natural conversion of grasslands to Douglas fir forests appears to be a more important reason for the historic loss of A. curtus populations.     

Increased relative abundance of an invasive competitor for pollination, Lythrum salicaria, reduces seed number in Mimulus ringens

When exotic plant species share pollinators with native species, competition for pollination may lower the reproductive success of natives by reducing the frequency and/or quality of visits they receive. Exotic species often become numerically dominant in plant communities, and the relative abundance of these potential competitors for pollination may be an important determinant of their effects on the pollination and reproductive success of co-occurring native species. Our study experimentally tests whether the presence and abundance of an invasive exotic, Lythrum salicaria L. (Lythraceae), influences reproductive success of a co-flowering native species, Mimulus ringens L. (Phrymaceae). We also examine the mechanisms of competition for pollination and how they may be altered by changes in competitor abundance. We found that the presence of Lythrum salicaria lowered mean seed number in Mimulus ringens fruits. This effect was most pronounced when the invasive competitor was highly abundant, decreasing the number of seeds per fruit by 40% in 2006 and 33% in 2007. Reductions in the number of seeds per fruit were likely due to reduced visit quality resulting from Mimulus pollen loss when bees foraged on neighboring Lythrum plants. This study suggests that visit quality to natives may be influenced by the presence and abundance of invasive flowering plants.     

Responses of pre‐dispersal seed predators to sequential flowering of Dipterocarps in Malaysia

Many species of Dipterocarpaceae and other plant families reproduce synchronously at irregular, multi‐year intervals in Southeast Asian forests. These community‐wide general flowering events are thought to facilitate seed survival through satiation of generalist seed predators. During a general flowering event, closely related Shorea species (Dipterocarpaceae) stagger their flowering times by several weeks, which may minimize cross pollination and interspecific competition for pollinators. Generalist, pre‐dispersal seed predators might also track flowering hosts and influence predator satiation. We addressed the question of whether pre‐dispersal seed predation differed between early and late flowering Shorea species by monitoring flowering, fruiting and seed predation intensity over two general flowering events at the Pasoh Research Forest, Malaysia. Pre‐dispersal insect seed predators killed up to 63 percent of developing seeds, with Nanophyes shoreae, a weevil that feeds on immature seeds being the most important predator for all Shorea species. This weevil caused significantly greater pre‐dispersal seed predation in earlier flowering species. Long larval development time precluded oviposition by adults that emerged from the earliest flowering Shorea on the final flowering Shorea. In contrast, larvae of weevils that feed on mature seeds before seed dispersal (Alcidodes spp.), appeared in seeds of all Shorea species almost simultaneously. We conclude that general flowering events have the potential to satiate post‐dispersal seed predators and pre‐dispersal seed predators of mature fruit, but are less effective at satiating pre‐dispersal predators of immature fruit attacking early flowering species.     

濒危植物金花猕猴桃繁殖生物学初步研究

繁殖生物学是目前濒危植物保护生物学研究的重点领域之一,金花猕猴桃(Actinidia chrysantha)是猕猴桃属濒危物种之一,目前未见其繁殖生物学相关报道。因此,该文以分布于花坪国家级自然保护区的野生金花猕猴桃为研究对象,用游标卡尺测量了花器官及果实形态,通过野外观察记录了其物候、访花昆虫及开花结果习性,用人工授粉和套袋法确定其传粉媒介,开展田间播种试验确定种子繁殖力,对其繁殖生物学开展了较为系统的研究。结果表明：金花猕猴桃物候因海拔高度不同而不同,较低海拔地区5月中下旬开花,高海拔地区5月下旬至6月上旬开花,花期持续7~10 d,果实每年9月下旬至10月上旬成熟;雄株花枝率76.5％,雌株果枝率61.9％,果实长圆柱形、短圆柱形或椭圆形,平均单果重7.34~27.53 g,最大果重35.0 g;金花猕猴桃为虫媒和风媒共同授粉,主要访花昆虫有蜜蜂科、细蜂科、鼻蝇亚科、食蚜蝇科、蜡蝉科、大蚊科长脚蚊属昆虫等;金花猕猴桃种子发芽率低,参试的3个居群的种子发芽率存在差异,分别为花坪17.5％,资源车田15.36％,贺州姑婆山0;4种不同种子处理方式中,低温＋GA3处理的种子发芽率(22.67％)最高。综上所述,金花猕猴桃不存在传粉障碍,种子萌发率低可能是致其濒危的重要原因。该研究结果为保护金花猕猴桃种质资源提供了科学依据。     

Flowering,fruiting and seed germination in Chilean rain forest myrtaceae: ecological and phylogenetic constraints

Phenological studies in plant communities have generally focused on taxonomically heterogeneous species assemblages, and have only occasionally examined the evolutionary and ecological constraints on the phenological patterns of species within a single family or a genus. Here, we determine relative importance of phylogenetic versus other constraints on the flowering and fruiting periods of 12 species and the germination ecology of 10 species of Myrtaceae sympatric to the temperate rainforest of Isla Grande de Chiloé (42 °Cs 30 S), in southern Chile.We found that, for most species in the family Myrtaceae, flowering was strongly aggregated in January and February. Although this pattern is consistent with the expectation of the 'facilitation' hypothesis (i.e., interspecific overlaps are maximized to attract pollinators), available evidence suggests that pollinators, mainly hymenopterans and dipterans, do not limit fruit production in these species of Myrtaceae in the temperate rainforest. In contrast to flowering, fruiting occurred all-year-round, showing greater segregation in time among the species. According to the their temporal patterns of fruit ripening, two functional groups were defined within the Myrtaceae: those that ripen their fruits immediately after flowering (species in the subtribe Myrtinae) and those in which green fruit develops slowly for several months before ripening (subtribe Myrciinae). Seed germination in the field occurred mainly between August and October. Lab assays showed that the species of Myrtaceae, subtribe Myrtinae, exhibited a long seed dormancy (>40 days), while the seeds of species in the subtribe Myrciinae often germinated within one week after harvesting. The analysis of the phenology of reproductive events in the species of Myrtaceae in this rainforest suggests that: (1) flowering periods patterns are constrained mainly by phylogenetic inertia at the family level, and (2) differences in fruiting patterns and dormancy periods are determined mainly by fruit and seed size, which in turn are associated primarily with phylogenetic closeness within the family, and secondarily with the activity of vertebrate seed dispersers.     

Pollinator‐mediated interactions between cultivated papaya and co‐flowering plant species

Many modern crop varieties rely on animal pollination to set fruit and seeds. Intensive crop plantations usually do not provide suitable habitats for pollinators so crop yield may depend on the surrounding vegetation to maintain pollination services. However, little is known about the effect of pollinator‐mediated interactions among co‐flowering plants on crop yield or the underlying mechanisms. Plant reproductive success is complex, involving several pre‐ and post‐pollination events; however, the current literature has mainly focused on pre‐pollination events in natural plant communities. We assessed pollinator sharing and the contribution to pollinator diet in a community of wild and cultivated plants that co‐flower with a focal papaya plantation. In addition, we assessed heterospecific pollen transfer to the stigmatic loads of papaya and its effect on fruit and seed production. We found that papaya shared at least one pollinator species with the majority of the co‐flowering plants. Despite this, heterospecific pollen transfer in cultivated papaya was low in open‐pollinated flowers. Hand‐pollination experiments suggest that heterospecific pollen transfer has no negative effect on fruit production or weight, but does reduce seed production. These results suggest that co‐flowering plants offer valuable floral resources to pollinators that are shared with cultivated papaya with little or no cost in terms of heterospecific pollen transfer. Although HP reduced seed production, a reduced number of seeds per se are not negative, given that from an agronomic perspective the number of seeds does not affect the monetary value of the papaya fruit.     

The effect of pollination on the growth and reproduction of oilseed rape (Brassica napus)

Phenotypic plasticity is an organism's ability to alter its development and life history in response to environmental conditions. In plants, biotic and abiotic factors drive the distribution of resources between growth and reproductive traits. One such biotic factor is pollination. Studies show that wind and insect pollination enhance oilseed rape (Brassica napus) yield. However, the impact of pollination on resource allocation towards growth and reproduction is less understood. We conducted a controlled experiment to assess the effect of pollination on growth and functional reproductive traits. We compared two simulated supplementary pollen deposition methods (representing wind and insect pollination) alongside a non-supplementary control. Pollinated plants allocated resources towards growth and reproduction similarly, irrespective of deposition method. Plants receiving no supplementary pollination produced fewer seeds, allocating resources to growth, more prolific and persistent flowering, and heavier seeds. Pollinated plants had a reduced flowering period and were shorter, indicating resources were allocated to seed production rather than growth or the production of additional flowers. This allocation of resources from growth and flowering metrics can increase yield directly through increased seed production and indirectly through shorter plants and a reduced flowering period with seeds that mature earlier (agronomically beneficial traits).Wind and insect pollination can enhance and stabilise oilseed rape yield under various environmental conditions by acting in complementary ways. Since pollination limits yield in oilseed rape, it must be considered an input that can be actively managed. Successful management of pollination services requires growers to detect pollination deficits. Inadequately pollinated oilseed rape plants exhibit apparent morphological changes (e.g. taller plants that flower for longer), acting as an early warning to growers. Equipping growers with this knowledge provides them with a means of detecting deficits and thus enables them to take positive action to restore pollination services by introducing honeybees or enhancing wild pollinators.     

The impacts of flowering phenology on the reproductive success of the narrow endemic Nouelia insignis Franch. (Asteraceae)

Nouelia insignis Franch. (Asteraceae) is a short, narrow endemic and endangered tree, growing with a natural population in the dry and hot valley of the Jinsha River in the southwest area of China. In this work, flowering phenology (time and duration), floral biology, visit frequency and behavior of pollinators, and pollination characteristics were studied based on investigation in the field and analysis in the laboratory with the help of a stereomicroscope, and the relationship between seed setting rate and reproductive traits, as well as the relationship between flowering time and rainfall before flowering, was tested using the method of general linear regression model. The results showed that natural population of N. insignis exhibited high flowering synchrony with relatively stable flowering duration, and the flowering time fluctuated greatly depending on the rainfall 5 months before flowering. The pollination of N. insignis required pollinators, and insect activities played a very important role in the pollination process. However, lack of the pollinators was not a limitation for reproductive fitness in N. insignis, although the number of pollinators was small and the frequency of visits was low. In addition, no pollen limitation was found during pollination. The average seed setting rate of N. insignis in the natural condition was only 1.52%–3.73%, and it was generally affected by changes in flowering phenology between years and had a higher seed set in early flowering year. The annual variation of seed set might be related to the annual variations of stamen and pistil functions, such as changes of pollen viability and stigma receptivity, which were closely related to flowering time. The results of this study are of value for further conservation actions on natural population of this threatened endemic plant.     

Later flowering is associated with a compressed flowering season and reduced reproductive output in an early season floral resource

Climate change‐induced shifts in flowering phenology can expose plants to novel biotic and abiotic environments, potentially leading to decreased temporal overlap with pollinators and exposure to conditions that negatively affect fruit and seed set. We explored the relationship between flowering phenology and reproductive output in the common shrub pointleaf manzanita Arctostaphylos pungens in a lower montane habitat in southeastern Arizona, USA. Contrary to the pattern of progressively earlier flowering observed in many species, long‐term records show that A. pungens flowering onset is shifting later and the flowering season is being compressed. This species can thus provide unusual insight into the effects of altered phenology. To determine the consequences of among‐ and within‐plant variation in flowering time, we documented individual flowering schedules and followed the fates of flowers on over 50 plants throughout two seasons (2012 and 2013). We also measured visitation rates by potential pollinators in 2012, as well as both fruit mass and seeds per fruit of flowers produced at different times. Fruit set was positively related to visitation rate but declined with later dates of flower production in both years. Total fruit production per plant was positively influenced by flowering duration, which declined with later flowering onset, as did fruit mass. Individual flowering schedules were consistent between years, suggesting that plants that begin flowering late have lower reproductive output each year. These patterns suggest that if pointleaf manzanita flowering continues to shift later, its flowering season may continue to become shorter, compressing floral resource availability for pollinators and leading to reduced reproductive output. These results reveal the negative effects of delayed phenology on reproductive output in a long‐lived plant. They highlight the value of using natural variation in flowering time, in combination with long‐term data, to anticipate the consequences of phenological shifts.     

Pollination ecology of Isoglossa woodii,a long‐lived,synchronously monocarpic herb from coastal forests in South Africa

Synchronous monocarpy in long‐lived plants is often associated with pollination by wind, in part because infrequent mass flowering may satiate pollinators. Selfing in synchronous monocarps may provide reproductive assurance but conflict with the benefits of outcrossing, a key evolutionary driver of synchrony. We predicted that animal‐pollinated species with synchronous flowering would have unspecialised flowers and attract abundant generalised pollinators, but predictions for selfing and outcrossing frequencies were not obvious. We examined the pollination biology of Isoglossa woodii (Acanthaceae), an insect‐pollinated, monocarpic herb that flowers synchronously at 4–7‐year intervals. The most frequent visitor to I. woodii flowers was the African honeybee, Apis mellifera adansonii. Hand‐pollination failed to enhance seed production, indicating that the pollinators were not saturated. No seed was set in the absence of pollinators. Seed set was similar among selfed and outcrossed flowers, demonstrating a geitonogamous mixed‐mating strategy with no direct evidence of preferential outcrossing. Flowers contained four ovules, but most fruits only developed one seed, raising the possibility that preferential outcrossing occurs by post‐pollination processes. We argue that a number of the theoretical concerns about geitonogamous selfing as a form of reproductive assurance do not apply to a long‐lived synchronous monocarp such as I. woodii.     

Seed germination and seedling allogamy in Rosmarinus officinalis: the costs of inbreeding

• Self‐pollination by geitonogamy is likely in self‐compatible plants that simultaneously expose a large number of flowers to pollinators. However, progeny of these plants is often highly allogamous. Although mechanisms to increase cross‐pollination have been identified and studied, their relative importance has rarely been addressed simultaneously in plant populations.
• We used Rosmarinus officinalis to explore factors that influence the probability of self‐fertilisation due to geitonogamy or that purge its consequences, focusing on their effects on seed germination and allogamy rate. We experimentally tested the effect of geitonogamy on the proportion of filled seeds and how it influences germination rate. During two field seasons, we studied how life history and flowering traits of individuals influence seed germination and allogamy rates of their progeny in wild populations at the extremes of the altitudinal range. The traits considered were plant size, population density, duration of the flowering season, number of open flowers, flowering synchrony among individuals within populations and proportion of male‐sterile flowers.
• We found that most seeds obtained experimentally from self‐pollination were apparently healthy but empty, and that the proportion of filled seeds drove the differences in germination rate between self‐ and cross‐pollination experiments. Plants from wild populations consistently had low germination rate and high rate of allogamy, as determined with microsatellites. Germination rate related positively to the length of the flowering season, flowering synchrony and the ratio of male‐sterile flowers, whereas the rate of allogamous seedlings was positively related only to the ratio of male‐sterile flowers.
• Rosemary plants purge most of the inbreeding caused by its pollination system by aborting the seeds. This study showed that the rates of seed germination and allogamy of the seedlings depend on a complex combination of factors that vary in space and time. Male sterility of flowers, length of the flowering season and flowering synchrony of individuals within populations all favour high rates of cross‐pollination, therefore increasing germination and allogamy rates. Flowering traits appear to be highly plastic and respond to local and seasonal conditions.

     

Temporal variation in the female components of reproductive success over the extended flowering season of a Mediterranean perennial herb

We examined the reproductive success of the perennial herb Lobularia maritima during its extended flowering and fruiting season. The within- and between-year variability of the female components of reproductive success (from flower, fruit and seed production to seed survival, seed germination and seedling establishment) were analysed during four flowering seasons. All the components of reproductive success studied showed a significant within- and between-year variation. September was the period of the year with the maximum values of flower and fruit production, and the highest germination and establishment rates. Nevertheless, seed losses due to both predispersal and postdispersal seed predation during this period were also the highest, seriously reducing seed output in this period. On the other hand, in those periods in which seed production was low, i.e. January and May, the percentage of seeds lost to seed predators was the lowest. Reproductive success in each period of the flowering season was estimated using a simple demographic model, in which the information concerning all the components already calculated was integrated. The two variables used to estimate reproductive success in each period, i.e. the number of new individuals produced per plant and the probability of a seed becoming an adult plant, showed relatively small differences over the year. These results suggest a counter-balance of the different components of reproductive success in this species, with favourable and unfavourable periods for the different components being compensated during its extended flowering season.     

Tibouchina pulchra (Melastomataceae): reproductive biology of a tree species at two sites of an elevational gradient in the Atlantic rainforest in Brazil

Low-temperature environments interfere with plant reproduction by reducing the frequency of pollinators, and this may favour reproductive strategies such as self-pollination and apomixis. Tibouchina pulchra is a common tree species that occurs at high and low sites of the Brazilian Atlantic rainforest. This study focussed on the pollination biology and breeding system of this species, describing the pollinators and the reproductive success at the two sites of an elevational gradient. Observations were made to determine extent of flowering and fruiting, to identify the richness and abundance of pollinators, and to record data on the floral and reproductive biology at these two sites. Despite more dense flowering at the high site, five visits of bees (two species) were recorded during the observation time (60?h), whereas at the low site there were 948 visits (seven species) during the same period. In contrast with the low site, the flowers of the high site released and received few pollen grains on the stigma. At the high site less fruit was set with fewer seeds as a result of open pollination than at the low site; at that site, however, more seeds were obtained from cross-pollination than at the low site. Tibouchina pulchra is self-compatible; however it is not apomictic and needs pollinators for seed set at both sites. Life-history traits other than the breeding system, for example more dense flowering, advantage of greater fertility in cross-pollination, and multiple reproductive events during the lifetime of the tree may reduce inbreeding depression, increase the hybrid vigour, and balance the lack of pollinators at the high site.