Octad pollen formation in Cymbopetalum (Annonaceae): the binding mechanism

Our recent study of tetrad pollen formation in Annona (Annonaceae) revealed that after meiosis the callose-cellulose envelope forms a special conjugation with individual microspores and the forthcoming callose digestion is incomplete. The undigested part forms a central binder holding the four microspores of the tetrad together. This process causes the microspores to rotate 180 degrees. In this paper we describe pollen formation in another annonaceous genus, Cymbopetalum, in which the pollen is shed in octads, through use of light microscopy, epifluorescence microscopy, and TEM. In Cymbopetalum, two meiocytes, connected by abundant cytomictic channels, are produced in each sporangium. Octad pollen formation in Cymbopetalum is shown to be comparable to the synchronized formation of two connected Annona tetrads, which then integrate into a single octad. Unique features of Annona polyad formation, e.g. special binding between the callose-cellulose envelopes and microspores, incomplete callose digestion, and microspore rotation, also occur in Cymbopetalum. In addition, formation of the Cymbopetalum octad involves development of a cushion-like structure that binds the distal pronexine of all eight microspores, and there is the production of intine protrusions. The evolutionary origin of the callose-cellulose binding mechanism within the family is discussed.     

Apical pattern of fruit production in the racemes of Ceratonia siliqua (Leguminosae: Caesalpinioideae): role of pollinators

Fruit production and arrangement within the raceme were studied in two dioecious populations of Ceratonia siliqua (Leguminosae: Caesalpinioideae), an arboreal species that produces caulogenous racemes (emerging only from the old branches) with numerous flowers. Fruit production per raceme was low and similar between years and populations and even between individuals. During flowering, there were considerable flower losses from predation and lack of pollination. A mean of nine flowers per raceme began the transformation into fruits, of which 77% aborted. The final fruit production per raceme increased significantly following hand pollination, but was always very much lower than the availability of flowers in the raceme. The results suggest that fruit production of each raceme is limited by both availability of resources and a deficient pollination. In racemes setting fruit arrangement follows a definite pattern that remains constant between years and populations: fruit production was significantly higher in the apical zone of the raceme and lower in the basal zone. The pollinators of C. siliqua (flies and wasps) showed a clear preference for beginning their visits at the apex of a raceme. As a result, the pollen load deposited on the stigmas decreased from apex to base of the raceme. In most of the flowers situated in the central and basal zone of the raceme, the number of pollen grains deposited on their stigmas was lower than the number of their ovules. The high number of seeds in developed fruits suggests that the plant selectively aborts flowers that receive a smaller pollen load. The results indicate that the final pattern of fruit arrangement within the raceme is a direct result of pollinator activity.     

Genetic variability of an endangered Bromeliaceae species (Pitcairnia albiflos) from the Brazilian Atlantic rainforest

Pitcairnia albiflos is a Bromeliaceae species endemic to Brazil that has been included as data-deficient in the extinction risk list of Brazilian flora. We analyzed genetic variability in P. albiflos populations using RAPD markers to investigate population structure and reproductive mechanisms and also to evaluate the actual extinction risk level of this species. Leaves of 56 individuals of P. albiflos from three populations were collected: Urca Hill (UH, 20 individuals), Chacrinha State Park (CSP, 24 individuals) and Tijuca National Park (TNP, 12 individuals). The RAPD technique was effective in characterizing the genetic diversity in the P. albiflos populations since it was possible to differentiate the populations and to identify exclusive bands for at least two of them. Even if there is low genetic diversity among them (CSP-UH = 0.463; CSP-TNP = 0.440; UH-TNP = 0.524), the populations seem to be isolated according to the low genetic diversity observed within them (H(pop) CSP = 0.060; H(pop) UH = 0.042; H(pop) TNP = 0.130). This fact might be the result of clonal and self-reproduction predominance and also from environmental degradation around the collection areas. Consequently, it would be important to protect all populations both in situ and ex situ to prevent the decrease of genetic variability. The low genetic variability among individuals of the same population confirms the inclusion of this species as critically endangered in the risk list for Brazilian flora.     

Richness and diversity of sand flies (Diptera,Psychodidae) in an Atlantic rainforest reserve in southeastern Brazil

Our objective was to study and evaluate the richness and diversity of Phlebotominae fauna in the Duas Bocas Biological Reserve (DBBR) in the state of Espírito Santo, in southeastern Brazil. Sand fly collections were carried out during four consecutive nights each month between August 2007 and July 2008 at DBBR by using CDC automatic light traps and an illuminated Shannon trap. Specific richness (S) and Shannon diversity index (H) was calculated for each trap. We collected 18,868 sand flies belonging to 29 species and 13 genera. Nyssomyia yuilli yuilli was the most abundant species followed by Psychodopygus ayrozai, Ps. hirsutus, Psathyromyia pascalei, and Ps. matosi. We recorded Brumptomyia cardosoi, Br. troglodytes, and Ps. geniculatus for the first time in the state of Espírito Santo. We discuss the differences in diversity and richness of the sand flies in both traps and in relation to other Brazilian localities and biomes. We also discuss the possibility of wild transmission of Leishmania in the DBBR and the influence of the sand fly species in leishmaniasis transmission to the adjacent areas of the reserve.     

Low genetic structure in an epiphytic Orchidaceae (Oncidium hookeri) in the Atlantic rainforest of South-eastern Brazil

BACKGROUND AND AIMS: Oncidium hookeri is a neotropical species of epiphytic Orchidaceae found in the Brazilian Atlantic rainforest at the top of the Mantiqueira Range of mountains. The genetic variation of O. hookeri was studied to assess the distribution of genetic variability within and among six populations localized in Atlantic rainforest remnants. Gene flow among populations and the occurrence of recent bottlenecks were investigated in order to infer the degree of isolation of these populations. METHODS: Thirteen polymorphic loci were used for allozyme electrophoresis. The data were analysed by means of standard statistical approaches, to estimate gene diversity and the genetic structure of the populations. KEY RESULTS: The mean gene diversity and allelic richness were H(e) = 0.099 and A = 1.75, respectively. F-statistics revealed high heterozygote deficiencies in all populations (F(IS) = 0.43-0.82). Several rare alleles were found in all the populations, and three populations presented private alleles. Low genetic differentiation among O. hookeri populations was detected (F(ST) = 0.029); natural selection may be involved in PGM locus differentiation among populations. The genetic differentiation between paired populations was low, bearing no correlation with geographic distance (Mantel test: r = -0.34, P = 0.72). Only two populations showed signs of recent bottlenecks. CONCLUSIONS: The heterozygote deficiency found seems to be caused by pollinator behaviour; the low frequencies of several alleles of different loci can be maintained due to clonal propagation. Despite the stochastic nature of the wind-dispersal of seeds to long distances, this process may promote an effective gene flow among populations, thus avoiding genetic differentiation.     

Fruiting phenology of palms and trees in an Atlantic rainforest land-bridge island

Tropical forests show periods of scarcity and high fruit production in the same year and/or between years. Palms are an important component of Neotropical rainforests and a significant food resource for several frugivores. Therefore, their role as keystone resource may be exacerbated in highly impoverished areas. In Anchieta Island, São Paulo/Brazil, human settlements have modified and impoverished the forest, mainly through overharvesting and the introduction of exotic plants and several mammal species. We assessed the offer of fruits consumed by vertebrate frugivores at this island, the vegetation of which is belonging to the Brazilian Atlantic rainforest. We compared whether the fruiting patterns and fruit fall differ between palms and trees, and discuss the importance of palms as a food resource for frugivores and the implications for Anchieta Island conservation. Phenological patterns were seasonal for both trees and palms; however, the times of fruiting occurrence differed. Fruit fall biomass was at least twice lower than reported for other Atlantic rain forests and was also different between trees and palms. Palms contributed more than 80% of the overall fruit fall biomass. Palms may constitute an alternative food resource in periods of low fruit availability, although they do not provide resources for the entire assemblage of vertebrate frugivores. Energy-rich fruits, such as those produced by palms, may play an important role in the maintenance of frugivore populations in isolated, disturbed environments with a high density of vertebrate frugivores, low diversity of fruiting species and fruit biomass such as those found on Anchieta Island.     

Perfume-collecting male euglossine bees as pollinators of a basal angiosperm: the case of Unonopsis stipitata (Annonaceae)

Pollination of Unonopsis stipitata (Annonaceae) by males of two perfume-collecting bees, Euglossa imperialis and Eulaema bombiformis (Euglossini) is described. This is the first detailed account of this pollination mode in a member of a basal angiosperm family. Pollinator behaviour, identification of the odour bouquet and electrophysiological reaction of one of the two pollinators to the odour bouquet were determined. The collected odour is produced by 'osmophores' located adaxially on the petals. Starch and polysaccharides accumulated in petals are metabolized during odour emission. Mainly monoterpenes were detected in the scent samples, among them trans-carvone oxide. This molecule is thought by several authors to be the key attractant for male Eulaema bees and may be pivotal for convergent evolution of the perfume-collecting syndrome among dicotyledonous and monocotyledonous plants. It is speculated that Unonopsis , which on the basis of molecular age dating is considered a relatively recent genus of the Annonaceae (being 15–30 million years old), has diversified in relation to male euglossine bee pollinators.     

Effects of flower and seed predators and pollinators on fruit production in two sequentially flowering congeners

We examined spatial and temporal variability of understory herbaceousvegetation on opposing north- and south-facing slopes in an eastern deciduousold-growth forest in southeastern Ohio, USA. Secondly, we explored theinfluenceof sampling scale and analytical technique on our assessment of diversitypatterns. The influence of aspect and seasonality were examined at varyingsampling scales using observed richness, evenness, andH diversity measures, non-parametric richnessestimators, species-area curves, and SHE analysis. Herb layer composition,abundance, and diversity were strongly influenced by location (north slope vs.south slope), seasonal sampling period (April, June, August), and plot size(micro (2 m²)- vs. meso (70m²)-scale samples). Although north and south plots werecompositionally distinct, they followed similar courses of change through thegrowing season. Richness, evenness, and H diversitywere generally greater on the south plot whereas herbaceous abundance wasgreater on the north plot. Species composition and diversity showed markedphenological (temporal) changes, and comparison of diversity measures at micro-and meso-scales produced markedly different results. Minimum sample areas of150–200 m² were needed to evaluate micro-scalerichness in these species rich communities, suggesting that forest understoriesmay be frequently undersampled in ecological studies. Comparison of observedandestimated meso-scale richness also suggested underestimation of richness in thenorth plot, particularly earlier in the growing season. Thus, sample size,area,and time of sampling appear critical to assessment of diversity in spatiallyandtemporally variable communities such as herbaceous forest understories.     

Reproduction of beetle‐pollinated Anaxagorea dolichocarpa (Annonaceae) is resilient to habitat disturbance in rainforest fragments

Strong evidence exists that fragmentation negatively affects pollination and plant reproduction, but little research has been conducted with regards to tropical trees. Specifically, effects of forest fragmentation on reproduction of plants with beetle‐pollinated flowers are poorly understood, and there are no data on the impact of fragmentation on reproduction in the structurally important tropical family Annonaceae. We examined the relationship between fragment size, pollinator abundance and seed set of beetle‐pollinated Anaxagorea dolichocarpa (Annonaceae) in a disturbed Brazilian Atlantic rainforest. Flower and fruit production and abundance of pollinators were quantified over ten months in three large (306–388 ha) and three small (6–14 ha) forest fragments. We recorded per flower pollinator abundance, resulting fruit set (fruits per flower) and seed set (monocarps per fruit) for a total of 209 individually marked flowers, and compared pollinator abundance in 186 flowers across all fragments. Flower and fruit production differed among fragments, but were similar for the combined large and small fragments. Between 64.8% (large fragments) and 66.3% (small fragments) of flowers received at least one pollinator. We found no significant difference in pollinator numbers between large and small fragments, and no correlation between pollinator abundance and fruit and seed set. A single visitor had a high probability of pollinating a flower. We conclude that 1) fragment size had no influence on pollinator number and plant reproductive success, and 2) generalist behavior of the pollinating beetles mitigate the risk of pollination failure for the reproductively specialized plant. However, further research may yet reveal genetic impoverishment of populations in small fragments due to restricted pollinator movements.     

A rapid diversification of rainforest trees (Guatteria; Annonaceae) following dispersal from Central into South America

Several recent studies have suggested that a substantial portion of today's plant diversity in the Neotropics has resulted from the dispersal of taxa into that region rather than vicariance, but more data are needed to substantiate this claim. Guatteria (Annonaceae) is, with 265 species, the third largest genus of Neotropical trees after Inga (Fabaceae) and Ocotea (Lauraceae), and its widespread distribution and frequent occurrence makes the genus an excellent model taxon to study diversification patterns. This study reconstructed the phylogeny of Guatteria and inferred three major biogeographical events in the history of the genus: (1) a trans-oceanic Miocene migration from Central into South America before the closing of the Isthmus of Panama; (2) a major diversification of the lineage within South America; and (3) several migrations of South American lineages back into Central America via the closed Panamanian land bridge. Therefore, Guatteria is not an Amazonian centred-genus sensu Gentry but a major Miocene diversification that followed its dispersal into South America. This study provides further evidence that migration into the Neotropics was an important factor in the historical assembly of its biodiversity. Furthermore, it is shown that phylogenetic patterns are comparable to those found in Ocotea and Inga and that a closer comparison of these genera is desirable.     

Distyly and sequential pollinators of Psychotria nuda (Rubiaceae) in the Atlantic rain forest, Brazil

Reciprocal herkogamy is known to promote intermorph-pollination in distylous species, which are generally self- and intramorph-incompatible. Legitimate crossing rates are also influenced by pollinator foraging strategy, which determines most of the pollen flow in natural populations. This study reports on the floral morphology, compatibility relations and pollination biology of Psychotria nuda (Cham. and Schltdl.) Wawra in the Atlantic rain forest, southeastern Brazil, based on floral measurements, hand-pollination experiments and focal observation of floral visitors. It was found that P. nuda does not present an exactly reciprocal herkogamy, however, this morphological trait in P. nuda is as good as in most of Rubiaceae. Reproductive experiments showed compatibility relations similar to those frequently observed in distylous species. The hummingbirds Ramphodon naevius and females of Thalurania glaucopis were the main pollinators of P. nuda, presenting the traplining foraging strategy, which seems to maximize intermorph crosses in P. nuda flowers. These hummingbirds pollinated P. nuda flowers sequentially throughout the flowering period.     

Pollination in Jacaranda rugosa (Bignoniaceae): euglossine pollinators, nectar robbers and low fruit set

Nectar robbers access floral nectar in illegitimate flower visits without, in general, performing a pollination service. Nevertheless, their effect on fruit set can be indirectly positive if the nectar removal causes an incremental increase in the frequency of legitimate flower visits of effective pollinators, especially in obligate outcrossers. We studied pollination and the effect of nectar robbers on the reproductive fitness of Jacaranda rugosa , an endemic shrub of the National Park of Catimbau, in the Caatinga of Pernambuco, Brazil. Xenogamous J . rugosa flowers continuously produced nectar during the day at a rate of 1 μl·h⁻¹. Female and male Euglossa melanotricha were the main pollinators. Early morning flower visits substantially contributed to fruit set because stigmas with open lobes were almost absent in the afternoon. Ninety-nine per cent of the flowers showed damage caused by nectar robbers. Artificial addition of sugar water prolonged the duration of flower visits of legitimate flower visitors. Removal of nectar, simulating the impact of nectar robbers, resulted in shorter flower visits of euglossine bees. While flower visits of nectar-robbing carpenter bees ( Xylocopa frontalis , X . grisescens, X . ordinaria) produced only a longitudinal slit in the corolla tube in the region of the nectar chamber, worker bees of Trigona spinipes damaged the gynoecium in 92% of the flowers. This explains the outstandingly low fruit set (1.5%) of J. rugosa in the National Park of Catimbau.     

Genetic structure of Partamona helleri (Apidae, Meliponini) from Neotropical Atlantic rainforest

Stingless bees of the genus Partamona are distributed from southern Mexico to southern Brazil. This genus has been subject to different approaches to solve questions concerning general biology, taxonomy, systematics and biogeography, but population studies applying molecular techniques are inexistent. We analyzed the genetic structure of P. helleri across its geographic distribution along the coastal Atlantic tropical rainforest in Brazil. Ten mtDNA haplotypes were observed in 47 colonies of P. helleri of which some were exclusive and others shared among geographic sub-groups. Statistical analysis showed high genetic differentiation between geographic areas sampled. Fragmentation of the Atlantic forest during Pleistocene glaciations is discussed as a possible cause of the present haplotype distribution and frequency.     

Higher frequency of legitimate pollinators and fruit set of autotetraploid trees of Libidibia ferrea (Leguminosae) compared to diploids in a mixed tropical urban population

Journal of Plant Research - In mixed-ploidy populations, newly formed polyploids initially occur at low frequencies when compared to diploids. However, polyploidy may lead to morphological and...     

Conservation status of parrot populations in an Atlantic rainforest area of southeastern Brazil

A census of four species of syntopic parrots was carried out using distance sampling methods on São Sebastião island, SE Brazil. Most of the 33593 ha island is covered by mature and secondary Atlantic rainforest. Almost 80% of these forests are within the Ilhabela Park. Although the species counted have marked differences in size and weight, density (individuals/km²) and estimated population size in 23500 ha of well-preserved forests were similar: Amazona farinosa (13.82±5.94; 3247±1395), Pionus maximiliani (15.79±7.04; 3712±1654), Brotogeris tirica (15.05±4.87; 3537±1143) and Pyrrhura frontalis (13.06±5.53; 3068±1298). Encounter rates of Forpus crassirostris and Pionopsitta pileata were very low, which suggests that there is only a small population of these species on the island. The São Sebastião forests still support healthy populations of parrots. Although woodpecker population estimates on the island are large enough to provide nesting sites for parrots, competition for holes with other secondary cavity nesters such as toucans, flycatchers and tytiras, and the selective cutting of dead trees for canoe construction, which is a common practice on the island, may limit hole availability for parrots.     

Comparative cyto-embryological investigations of sexual and apomictic dandelions (Taraxacum) and their apomictic hybrids

. In the autonomous apomictic Taraxacum officinale (common dandelion), parthenogenetic egg cells develop into embryos and central cells into endosperm without prior fertilisation. Unreduced (2n) megaspores are formed via meiotic diplospory, a nonreductional type of meiosis. In this paper, we describe the normal developmental pathways of sexual and apomictic reproduction and compare these with the development observed in the apomictic hybrids. In sexual diploids, a standard type of megasporogenesis and embryo sac development is synchronised between florets in individual capitula. In contrast, we observed that megasporogenesis and gametogenesis proceeded asynchronously between florets within a single capitulum of natural triploid apomicts. In addition, autonomous endosperm and embryo development initiated independently within individual florets. Parthenogenetic initiation of embryo development in outdoor apomicts was found to be temperature-dependent. Egg cells produced in natural apomicts were not fertilised after pollination with haploid pollen grains although pollen tubes were observed to grow into their embryo sacs. Both reductional and diplosporous megasporogenesis were observed in individual inflorescences of triploid apomictic hybrids. Embryo and endosperm development initiated independently in natural and hybrid apomicts.     

Ticks (Acari: Ixodidae) parasitizing humans in an Atlantic rainforest reserve of Southeastern Brazil with notes on host suitability

While conducting projects on ticks from deer and on tick ecology in animal trails in an Atlantic rainforest reserve in Southeastern Brazil, researchers of our group were bitten by ticks several times. Some of these episodes were recorded. Three species of adult ticks attached to humans: Amblyomma brasiliense Aragão, Amblyomma incisum Neumann, and Amblyomma ovale Koch. Eight nymphal attachments with engorgement on humans were recorded. From these, six molted to adults of A. incisum, one to an adult of A. brasiliense, and one had an anomalous molting, therefore the adult tick could not be properly identified. Local reactions to tick attachment varied among individual hosts from almost imperceptible to intense. Especially itching, but hyperemia and swelling as well, were prominent features of the reaction. Overall it can be affirmed that human beings can be a physiologically suitable host species for ticks in the Atlantic rainforest and that itching was an important if not the major component of the resistance to tick bite.     

The North Atlantic Oscillation synchronises fruit production in western European forests

Weather and its lagged effects have been associated with interannual variability and synchrony of fruit production for several tree species. Such relationships are used often in hypotheses relating interannual variability in fruit production with tree resources or favourable pollinating conditions and with synchrony in fruit production among sites through the Moran effect (the synchronisation of biological processes among populations driven by meteorological variability) or the local availability of pollen. Climatic teleconnections, such as the North Atlantic Oscillation (NAO), representing weather packages, however, have rarely been correlated with fruit production, despite often being better predictors of ecological processes than is local weather. The aim of this study was to test the utility of seasonal NAO indices for predicting interannual variability and synchrony in fruit production using data from 76 forests of Abies alba, Fagus sylvatica, Picea abies, Pseudotsuga menziesii, Quercus petraea, and Q. robur distributed across central Europe. Interannual variability in fruit production for all species was significantly correlated with seasonal NAO indices, which were more prominently important predictors than local meteorological variables. The relationships identified by these analyses indicated that proximal causes were mostly responsible for the interannual variability in fruit production, supporting the premise that local tree resources and favourable pollinating conditions are needed to produce large fruit crops. Synchrony in fruit production between forests was mainly associated with weather and geographical distance among sites. Also, fruit production for a given year was less variable among sites during warm and dry springs (negative spring NAO phases). Our results identify the Moran effect as the most likely mechanism for synchronisation of fruit production at large geographical scales and the possibility that pollen availability plays a role in synchronising fruit production at local scales. Our results highlight the influence of the NAO on the patterns of fruit production across western Europe.