Passerine birds supporting cross pollination in Erythrina stricta Roxb.

Erythina stricta is an ecologically important tree species in the rainforests of India and its nectar within the flowers contributes to birds’ diet and survival. Reports on the pollination of this species have not been published so far. We therefore explore the reproductive system of this tree species which has great significance to its ecosystem. Birds have an important role in the reproduction of trees through pollination particularly in tropical areas where reproductive success mostly depends on animal pollinator interactions. Study of visitation and nectar feeding behaviour of birds along with breeding system assessment of Erythina stricta. Birds visiting and foraging behaviour was observed during Erythrina stricta flowering season in an indian tropical rainforest. Reproductive system was assessed through controlled pollination experiments. Thirteen bird species were recorded visiting and foraging nectar from the flowers of Erythrina stricta. The maximum numbers of visits recorded were from the Red-vented Bulbul (Pycnonotus cafer, Pycnonotidae). The nectar feeding birds were, either (i) potential pollinator with long bills (e.g. Pycnonotus spp., Chloropsis aurifrons, and Dicrurus spp.) or (ii) nectar robbers with comparatively shorter bills (e.g. Zosterops palpebrosa, Stachyris ruficeps, Macronous gularis, Heterophasia glaciris). Controlled pollination experiments revealed high degree of cross pollination (xenogamy) and self-incompatibility in E. stricta. Birds were more frequent in early mornings and their foraging activity was also observed during evening hours; the frequency however, declined with respect to nectar availability. Long corolla tubes of E. stricta could restrict access to nectar collecting bees.

High gene flow maintains wide-range species cohesion in a Neotropical epiphyte (Tillandsia aeranthos, Bromeliaceae)

Studies of patterns of genetic diversity, genetic structure and ecological data across geographical ranges of species allow us to test hypotheses about the evolutionary responses of organisms to fluctuations in habitat connectivity and availability. Here we present a study aiming to assess genetic diversity, population structure and breeding system across the geographical distribution of a subtropical epiphyte, Tillandsia aeranthos (Bromeliaceae), endemic to the Plata River basin (Pampa biome). Seven nuclear microsatellite markers were genotyped in 203 individuals from 13 localities across Brazil and Argentina and 14 plastid regions were sequenced for a subset of the individuals. Additionally, we performed controlled pollination experiments to discuss correlations between breeding system, genetic diversity and structure in the species. Nuclear diversity levels were high (HE = 0.806, HO = 0.745, allelic richness = 5.860) with no haplotype differentiation detected (c. 9 kpb sequenced). Bayesian assignment analysis, supported by principal coordinate analysis and analysis of molecular variance, show low genetic structure across the studied area (FST = 0.031, P < 0.001). Controlled pollination experiments indicated complete self-incompatibility in all localities analysed. Our results show effective gene flow maintaining low genetic structure between localities for T. aeranthos across an extensive area in the Pampa.

Reproductive biology of duodichogamous Koelreuteria elegans (Sapindaceae): the rare case of a female–male–female flowering sequence

Monoecious species are common within Sapindaceae, and among them a large variation in sexual expression has been reported. In this work we evaluate the sexual expression, phenology, floral biology, and mating system in eight to sixteen individuals of the duodichogamous Koelreuteria elegans (Seem.) A.C. Sm. subsp. formosana (Hayata) F.G. Mey. Results from our study show that all individuals exhibited a pattern of flowering characterised by two cycles of pistillate flowers with an intervening one of staminate flowers. The synflorescences presented a high synchronisation between the male and female phases at the individual level. Therefore, very little functional overlap was observed between pollen receipt and pollen dispatch within individuals. Pollination was by bees, and the manual pollination experiments showed that this species is a xenogamous although self-compatible species. Nevertheless, seed set increased significantly with hand cross-pollination and open pollination experiments. Decrease of fruits and seeds set by geitonogamy could favour the establishment of duodichogamy with interfloral protogyny promoting cross-pollination. In the family this is the first report of a pattern of flowering in which there are two cycles of female with an intervening cycle of male flowers. The importance of detailed these studies for understanding mechanisms underlying duodichogamy was demonstrated, and findings will help to broaden our understanding about this rare sexual system to generalise the specific ecological factors that explain its evolutionary meaning.

The mating system of Acrotriche serrulata (Ericaceae)

Controlled pollination experiments were conducted on Acrotriche serrulata R.Br. (Ericaceae) to determine the mating system for this species. Pollen viability and stigma receptivity were investigated to ensure effective timing and sourcing of material for maximum fertilisation. Stigmas were found to be receptive in mature buds, with receptivity maintained while nectar remained within the corolla tube. Germination testing showed that pollen from within mature buds was viable. The mating system of A. serrulata was found to be predominantly outcrossing, with 49.8% of cross-pollinated flowers developing to fruit, compared with 8.7% of self-pollinated flowers. Seed viability did not differ significantly between fruits produced by cross-pollination and those produced by self-pollination, although this may be attributable to low sample sizes available for self-pollinated fruits. These results in combination with morphological features of the flower suggest that a pollinator is required for this species.

A Novel Gel-based Method for Isolation of Stigmas During Controlled Pollination Experiments

In forestry, controlled pollination (CP) allows the combining of genetic material of selected elite trees to produce high quality, and consequently high value, seed. The aim of the present study was to develop a novel isolation method that would allow the technique to be conducted without expensive and time-consuming bagging, making CPs on small-flowered eucalypts commercially viable. We compared the current method of isolating inflorescences using exclusion bags to a novel method which uses sodium alginate gel. Sodium alginate was effective in keeping external pollen away from the stigma, since no seed was produced in those treatments that were not manually pollinated but isolated in this way. In addition, flowers hand-pollinated and isolated with sodium alginate produced progeny that were 100% outcrossed with the applied pollen. The exclusion bags, on the other hand, were not as effective in protecting the stigma as seed was produced in those treatments that were isolated with an exclusion bag without being handpollinated. Sodium alginate isolation also increased the efficiency of control-pollinations as the gel was naturally shed, removing the need for operators to return to the tree to remove the isolation material.

The pollination ecology of durian (Durio zibethinus, Bombacaceae) in southern Thailand

The floral biology and pollination ecology of durian, Durio zibethinus, were determined in eight semi-wild trees in mixed-fruit orchards in southern Thailand during April-May 2003 and 2005. Flowers open fully at 16h00–16h30 and most androecia drop around 01h00. Anthers dehisce at 19h30–20h00 when the stigmata are already receptive. In a series of pollination experiments, fruit was set in all treatments within 10 d. The greatest pollination success occurred after hand-crossed (76.6%), open (54.4%) and emasculation pollination (53.3%). Consistently, hand-crossed (12.2%), emasculation (8.7%) and open pollination (5.1%) yielded a substantial fruit set 2 mo after the pollination experiments. Very low pollination success in facilitated autogamy suggests that most durian trees are highly self incompatible. No mature fruit was found after insect pollination and automatic autogamy. Fruit bats, especially Eonycteris spelaea, are the major pollinators of this durian although the giant honey bee (Apis dorsata) was the most frequent visitor to the flowers. Bats visited durian flowers at the rate of 26.1 (SD = 20.7) visits per inflorescence per night. Since this semi-wild durian depends on fruit bats as its pollinator, protecting fruit bat populations and their roosts is vital for the production of the durian fruit crop.

The importance of being the first pollen in the strobili of Scots pine

Timing of pollen arrival may affect the level of seeds fertilized by pollen from outside seed orchards, especially in seed orchards of Scots pine ( Pinus sylvestris L.) established in southern Finland with stock from northern populations. We performed sequential pollination experiments with Scots pine pollen collected from seed orchard clones originating from southern and northern Finland and recipient strobili in clones originating from southern Finland. When southern pollen was introduced first, seeds were sired equally by northern and southern genotypes. When northern pollen was introduced first, northern genotypes were found in 75% of the resulting seeds. When both pollen types were introduced at the same time, the resulting seed crop was split almost equally between northern and southern genotypes. These results do not unconditionally support the idea that the first pollen grain in the pollen chamber always fertilizes the ovum; instead, they suggest a more complex way of competition between pollen grains.