Ecological stoichiometry of the epiphyte community in a subtropical forest canopy

Epiphytes in tree canopies make a considerable contribution to the species diversity, aboveground biomass, and nutrient pools in forest ecosystems. However, the nutrient status of epiphytes and their possible adaptations to nutrient deficiencies in the forest canopy remain unclear. Therefore, we analyzed the stoichiometry of five macroelements (C, N, P, K, and Ca) in four taxonomic groups (lichens, bryophytes, ferns, and spermatophytes) to investigate this issue in a subtropical montane moist evergreen broad‐leaved forest in Southwest China. We found that the interspecific variations in element concentrations and mass ratios were generally greater than the intraspecific variations. And there were significant stoichiometric differences among functional groups. Allometric relationships between N and P across the epiphyte community indicated that P might be in greater demand than N with an increase in nutrients. Although canopy nutrients were deficient, most epiphytes could still maintain high N and P concentrations and low N:P ratios. Moreover, ferns and spermatophytes allocated more limited nutrients to leaves than to stems and roots. To alleviate frequent drought stress in the forest canopy, vascular epiphytes maintained several times higher K concentrations in their leaves than in the tissues of lichens and bryophytes. Our results suggest that epiphytes may have evolved specific nutrient characteristics and adaptations, so that they can distribute in heterogeneous canopy habitats and maintain the stability of nutrient metabolism.     

The distribution of epiphyte growth-forms in the canopy of a Colombian cloud-forest

Cloud forests are known for their abundance in epiphytes. The growth-form composition of the epiphytic vegetation in the crowns of two tree-species in an upper-andean forest in Colombia is described. Bryophytes formed the bulk of the living epiphytic biomass, with tall turfs and smooth mats (sensu Richards 1984) as commonest growth-forms. Vascular plants and lichens were subordinate to bryophytes. Along the canopy-branches a clear sequence of growth-forms could be demonstrated. Analysis of this gradient by Detrended Correspondence Analysis (DCA), Two Way Indicator Species Analysis (TWINSPAN) and calculation of association-indices between growth-forms revealed two basic groups. One group is typical for the inner canopy, another for the outer canopy. An important determinant of the growth-form composition was the phorophyte species. The vegetational gradient was interpreted in terms of gradual changes in microclimatological factors, water- and nutrient availability and substratumage.     

Low genetic diversity in small leading edge populations of the European paleoendemic Ramonda serbica (Gesneriaceae) in Bulgaria

Ramonda serbica Pan?. (Gesneriaceae) is an endangered endemic species of the Balkan Peninsula which has been the subject of several studies in the past, but has not yet been investigated in terms of its genetic variation. Ramonda serbica is one of only five European representatives of the mainly subtropical family Gesneriaceae categorized as paleoendemics or Tertiary relicts sequestered in southern Europe by Quaternary climate oscillations. Here, an inter simple sequence repeat (ISSR) analysis was performed to determine the genetic diversity of five populations sampled from the geographically eastern fringe of its range in northwestern Bulgaria. We found relatively low levels of genetic diversity and significant genetic differentiation among the investigated populations, typical of a leading edge scenario. From a conservation point of view, the low genetic diversity, together with the presence of only few extant localities stress the need for urgent in situ and ex situ conservation actions to ensure the long‐term survival of R. serbica in Bulgaria.     

Genetic structure and diversity in Ramonda myconi (Gesneriaceae): effects of historical climate change on a preglacial relict species

The importance of the Mediterranean Basin as a long-term reservoir of biological diversity has been widely recognized, although much less effort has been devoted to understanding processes that allow species to persist in this area. Ramonda myconi (Gesneriaceae) is a Tertiary relict plant species restricted to the NE Iberian Peninsula. We used RAPD and chloroplast markers to assess the patterns of genetic structure in eight mountain regions covering almost the full species range, to identify the main historical processes that have shaped its current distribution and to infer the number and location of putative glacial refugia. While no cpDNA variation was detected, the species had relatively high levels of RAPD variation. Maximum levels of diversity were found within populations (71%), but there was also a significant differentiation between geographical regions (20%) and among populations within regions (9%). A spatial AMOVA identified three main groups of populations, corresponding to previously recognized centers of endemism and species richness. In addition, we found a marked geographical pattern of decreasing genetic diversity and increasing population differentiation from west to east. Our results support a complex phylogeographic scenario in the Iberian Peninsula of "refugia-within-refugia" and suggest that the higher diversity observed in western regions might be associated with prolonged and more stable climatic conditions in this area during the Quaternary.     

Dyssochroma viridiflorum (Solanaceae): a reproductively bat-dependent epiphyte from the Atlantic rainforest in Brazil

Few Neotropical plant species seem to depend on the same animal type both for pollination and seed dispersal, and the known instances refer mostly to birds as the agents in these two phases of a plant reproductive cycle. Dyssochroma viridiflorum (Solanaceae), an epiphyte endemic to the Atlantic rainforest in south-eastern Brazil, was found to be visited by phyllostomid bats for nectar as well as for fruits, with the pollination and seed dispersal of the plant ensured by these flying mammals. The greenish flowers open at night and are visited by the nectar-feeding bat Glossophaga soricina, whereas the yellowish-white fruits are consumed by two species of fruit-eating bats, Carollia perspicillata and Sturnira lilium. Only clinging visits, an uncommon behavioural pattern for glossophagine bats while feeding on flowers, were recorded. The small seeds of D. viridiflorum are swallowed along with the fruit pulp and later defecated on the bats' flying pathways. It is suggested that species of Dyssochroma and two other solanaceous bat-pollinated genera, Merinthopodium and Trianaea, form a derived and bat-dependent clade within the Juanulloeae.     

Howling on the edge: Mantled howler monkey (Alouatta palliata) howling behaviour and anthropogenic edge effects in a fragmented tropical rainforest in Costa Rica

The function of long calling is a subject of interest across animal behaviour study, particularly within primatology. Many primate species have male‐specific long‐distance calls, including platyrrhines like the folivorous howler monkey (Alouatta spp.). Howler monkeys may howl to defend resources such as feeding trees or areas of rich vegetation from other monkey groups. This study tests the ecological resource defence hypothesis for howling behaviour in the mantled howler monkey (Alouatta palliata) and investigates how anthropogenic forest fragmentation may influence howling behaviour. More specifically, this study examines how howling bout rate, duration, precursors and tree species richness, DBH, and canopy cover vary in 100 m anthropogenic edge and interior forest zones at La Suerte Biological Research Station (LSBRS), a fragmented tropical rainforest in Costa Rica. Results show that tree species richness and canopy cover are higher in forest interior at this site, suggesting that monkeys should howl at greater rates in the interior to defend access to these higher‐quality vegetation resources. Overall, our results supported the ecological resource defence hypothesis. The main howl precursor was howling from neighbouring groups. Although howling rate did not differ between forest zones, howling bouts from forest interior were longer, had a greater number of howls per bout and were preceded by different precursors than howls from anthropogenic edge zones, including more howls from neighbouring groups. Our findings provide some of the first evidence for behavioural edge effects in primate vocal communication behaviour.     

Evolution of Cyrtandra (Gesneriaceae) in the Pacific Ocean: the origin of a supertramp clade

Cyrtandra comprises at least 600 species distributed throughout Malesia, where it is known for many local endemics and in Polynesia and Micronesia, where it is present on most island groups, and is among the most successfully dispersing genera of the Pacific. To ascertain the origin of the oceanic Pacific island species of Cyrtandra, we sequenced the internal transcribed spacers of nuclear ribosomal DNA of samples from throughout its geographical range. Because all oceanic Pacific island species form a well-supported clade, these species apparently result from a single initial colonization into the Pacific, possibly by a species from the eastern rim of SE Asia via a NW-to-SE stepping stone migration. Hawaiian species form a monophyletic group, probably as a result of a single colonization. The Pacific island clade of Cyrtandra dispersed across huge distances, in contrast to the apparent localization of the SE Asian clades. Although highly vagile, the Pacific clade is restricted to oceanic islands. Individual species are often endemic to a single island, characteristic of the "supertramp" life form sensu Diamond (1974, Science 184: 803-806). The evolution of fleshy fruit within Cyrtandra provided an adaptation for colonization throughout the oceanic Pacific via bird dispersal from a single common ancestor.     

Postpollination nectar reabsorption in the African epiphyte Aerangis verdickii (Orchidaceae)

Nectar reabsorption in flowering plants seems to be a rare phenomenon and to our knowledge it has not been reported previously in the Orchidaceae. In this study we present data that show statistically significant differences in nectar sugar concentrations before and after pollination. Virgin flowers of the African epiphytic orchid Aerangis verdickii showed mean sugar concentrations in the nectar of 14.4 and of 18.3% in 1994 and 1995, respectively (sucrose mass by mass equivalent). Sugar concentration in nectar from naturally pollinated flowers had a mean of 3.2 and of 8.7% for the same period. In an experiment in the wild 60 flowers were protected against nectar theft by the ants. Half of those flowers were hand-pollinated. Control (virgin) flowers had nectar with a mean value of 13.8%, while flowers measured 48 h after pollination had a mean sugar concentration of 4.3%. The mean volume of nectar based on measurements of 23 virgin flowers from nine different plants was 19 uL. We estimated an average energy value for the nectar produced of 684 J per plant per season. At the study site, over 60% of the unmanipulated flowers were robbed of all their nectar by arboreal ants, Polyrachis spp. (Formicinae). The adaptive significance of nectar reabsorption for A. verdickii is probably a function of the environmental stresses to which it has been exposed and the relative costs of nectar production.     

Human dirofilariasis due to Dirofilaria (Nochtiella) repens: an update of world literature from 1995 to 2000.

Following on from their review of 1995 (Pampiglione et al.), the authors present an update of human cases of dirofilariasis due to Dirofilaria (Nochtiella) repens (Nematoda, Filarioidea, Onchocercidae) reported in the world literature. Cases of the parasitosis published from 1995 to 2000 are reported country by country. The essential data are presented in tabular form and the clinical, parasitological, histopathological, epidemiological features are analysed. 372 new cases spread over 25 countries are thus added to the list published in 1995. The countries most affected are Italy, Sri Lanka, some republics of the ex-Soviet Union. The age of the patients varied from 4 months to 100 years, the majority being in their 40s. There was virtually no difference in incidence between sexes. The parasite appeared most frequently in the upper half of the body, particularly in the head and ocular region and also in the upper limbs. Cases of visceral involvement are also reported. Of the various forms of human dirofilariasis, that due to D. (N.) repens is confirmed to be the most important as regards not only the number of subjects affected and the wide geographical distribution but also the variety of organs involved, notably the lungs, the male genitals and the female breast, invariably leading to a wrong diagnosis of malignant tumour. In man, the zoonosis may be described as emerging: whereas until the middle of the last century only a few dozen cases were reported, in the last 50 years the number has gradually increased to reach the present 782.     

Edge effects on the orchid-bee fauna (Hymenoptera: Apidae) at a large remnant of Atlantic Rain Forest in southeastern Brazil

Male orchid bees were sampled with chemical baits monthly from July 1999 to April 2000 at six sites situated at different distances from the forest edge (0 to 4,000 m) at Parque Estadual do Rio Doce, the largest remnant of Atlantic Forest in the state of Minas Gerais, southeastern Brazil. The main goal of this study was to assess the abundance, richness, and the community structure of the orchid-bee fauna at different distances from the edge. In all, 1,183 males from 20 species were collected. Only minor and insignificant variation in richness and abundance were observed among the sites. Two dominant species, Euglossa analis Westwood (Hymenoptera: Apidae) and Eulaema cingulata (Fabricius) (Hymenoptera: Apidae), showed strongly opposing habitat associations: while males of the former were most collected in the interior of the forest, the latter was most found at or close to the edge. The responses of individual species, such as these, and not composite measures of richness and abundance, are more informative regarding forest integrity and edge effects.     

Some effects of increased atmospheric carbon dioxide on white clover (Trifolium repens) and pea (Pisum sativum)

Summary The effects of atmospheric carbon dioxide enrichment on nitrogen fixation by white clover and pea, and on stomatal aperture, transpiration loss and nitrate reductase activity in white clover, are described and the implications discussed.     

Analysis of stand density effects on canopy structure: a conceptual approach

Summary A few assumptions were used to generate a series of specific, quantitative predictions for the relationships between stand density and various dimensional measures of canopy structure. The predictions, each indicating an increase in mean crown size as density decreased, appeared to be reasonable and intuitive. Predictions were compared to data for two conifer species with different crown forms, Pinus contorta var. latifolia and Abies lasiocarpa. Results of these comparisons were mixed — the linear, directly measured dimensions were consistent with predicted relationships, but dimensions calculated from the linear measures were not. Re-examination of the original assumptions indicated that the model should account for crown shyness (engagement/disengagement) to adequately reflect the influence of stand density on canopy structure. The results also indicated a strong association between stand height and measures of mean crown size. Mean crown size of lodgepole pine was altered much more by density than was mean crown size of subalpine fir, due primarily to the different relative shade tolerances of the two species. Some of the observed differences between species may also reflect the range of densities examined and uneven spacing in the unmanaged natural stands.     

Floral ecology of Oreocharis pumila (Gesneriaceae): a novel case of sigmoid corolla

Attraction of pollinators and successful pollen transfer represent the primary targets of selection during flower evolution, leading to repeated evolutionary shifts between pollinators and consequently to the diversification of floral forms. However, most studies in floral evolution focus on the characteristics of flowers with straight corolla tube. Here, we report on an unusual form of sigmoid corolla combined with protandry and herkogamy in a Chinese species of Gesneriaceae, Oreocharis pumila (formerly Opithandra pumila). Contrary to species with sigmoid corollas studied previously, the base of the corolla tube of this species is inclined at an oblique angle downwards before the tube bends forward, and the stigma and anthers are included in the upper part of the corolla tube. The plants were found to be self‐compatible but incapable of autonomous selfing. Successful pollination was found to depend fully on the presence of insect pollinators (Nomia sp.) and pollen grains are the greatest reward for the visitors. Different from the other sigmoid flowers, the sigmoid corolla of O. pumila was not found to favor insect pollinators with long flexible proboscises. A mechanical fit between floral morphology and pollinator was found, in which only small insect visitors with specialized visiting behavior are legitimate pollinators. The protandry combined with herkogamy in the sigmoid corolla tube strongly ensures pollination efficiencies. Oreocharis pumila is the only species with sigmoid corolla in the genus Oreocharis. We hypothesize that such a corolla has arisen through selection due to inadequate pollination in early spring in the mountainous habitat that O. pumila occupies.     

Resprouters vs reseeders in South African forest trees; a model based on forest canopy height

1. We expect tree species that regenerate primarily by sprouting to produce fewer seedlings than co-occurring species that regenerate mainly from seedlings, because of the trade-off between allocating resources either to ensuring vegetative reproduction (e.g. protective bark/latent buds) or to sexual reproduction (e.g. seeds).
2. Furthermore, resprouting species, because of their multi-stemmed nature, should be at a relative disadvantage, and therefore relatively infrequent, in tall forests. This is because a resprouting individual allocates resources to a number of basal branches/stems and buds rather than maximizing vertical extension of a single leader, as is the case in a seeder. Also, many tall stems arising from the same multi-stemmed base, as is the case in resprouters, will be relatively poorly supported in comparison to the single stem of a reseeder.
3. To test these two ideas we surveyed a number of plots in a range of South African forests and thicket communities. We noted the numbers of seedlings and resprouts for each species and determined a mean for each site.
4. Short forests and thickets were dominated by multi-stemmed species and there was an almost total absence of seedlings. In contrast, tall forests were dominated by single-stemmed reseeding species and were accompanied by seedlings.     

Role of canopy height in the resistance of Lycopersicon hirsutum f. glabratum to Tuta absoluta (Lep., Gelechiidae)

The objective of this work was to study the effect of plant canopy height on the resistance of the tomato species Lycopersicon hirsutum to the tomato leafminer Tuta absoluta . Determination of the levels of tridecan-2-one (2-TD) and undecan-2-one (2-UD) in L. hirsutum , as well as the leaf area, density and types of trichomes present in L. hirsutum and L. esculentum were made on apical, medium and basal parts of plant canopy. Correlation of these data were made with the following biological characteristics of T. absoluta : rates of oviposition and egg hatching; length of egg, larval and pupal stages; mortality of the larval and pupal stages; pupal weight; and sex ratio. Levels of 2-TD on leaves of L. hirsutum increased from bottom to top of canopy. Tuta absoluta had higher oviposition and egg hatching, as well as lower mortalities and smaller larval and pupal periods in L. esculentum than in L. hirsutum . Longer pupal period and greater number of small and large mines of T. absoluta were verified in the apical and medium parts of L. hirsutum plants. On the other hand, higher pupal mortality and longer larval periods were obtained in the apical and basal parts of the L. hirsutum plants. Larval mortality was higher in the basal part of those plants. In L. esculentum , leaves from the apical part of the plant promoted lower mortality, longer larval period and greater number of large mines of T. absoluta . However, a shorter pupal period was verified on leaves of the basal part. It appears that an increase in glandular trichome density in L. hirsutum leads to an increase in the levels of 2-TD, which, in turn slows down larval development.     

石蝴蝶属八种植物的染色体数目报道

观察了苦苣苔科石蝴蝶属(Petrocosmea)8种植物的染色体.发现它们的染色均属小型染色体,数目一致,皆为2n=34.     

Mosquito (Diptera: Culicidae) diversity along a rainy season and edge effects in a riparian forest in Southeastern Brazil

Knowledge on the distribution of mosquito communities over time and across human-modified landscapes is important in determining the risk for vector-borne disease. The diversity of mosquitoes along a rainy season and edge effects were evaluated in a riparian forest in the Cerrado biome, Southeastern Brazil. Mosquito communities were sampled with Shannon traps in three distinct habitats (forest interior, forest edge and pasture) throughout an entire rainy season, comprising five sampling months (December 2015 to April 2016). A total of 13 549 mosquitoes belonging to 54 species were sampled. Mosquito species richness and abundance were greater in February, which coincided with the middle of the rainy season and just after the months with greater rainfall. Mosquito species richness did not differ among habitats for any particular month. In February, month when 74% of individuals were recorded, mosquito abundance was lower in the pasture compared with the forest edge and interior, which did not differ statistically from each other. Four of the six most abundant mosquito species (which account for 93.5% of the sampled individuals) had more individuals collected in the forest edge, and 28 species were more abundant at the edge compared with 15 species in the forest interior. Months with high rainfall probably allowed the availability and maintenance of high-water level in breeding sites leading to a further increase in mosquito populations. While the pasture did not seem to have the ideal abiotic conditions and/or resources (e.g. food and breeding sites) for mosquito species, edge effects appear to favour mosquito populations. Therefore, the risk of mosquito-borne diseases is expected to be greater in the middle of the rain season at the riparian forest-pasture edge, when and where a greater number of disease-vectoring species are present.     

Assembly of tropical plant diversity on a local scale: Cyrtandra (Gesneriaceae) on Mount Kerinci, Sumatra

At a regional scale, the high species numbers (gamma diversity) of tropical forests have been explained by either a gradual accumulation of species through time (museum hypothesis) or, by contrast, rapid recent speciation in large genera. However, the origins of local rain forest diversity (alpha diversity) have been given little attention. Cyrtandra (Gesneriaceae), an understorey genus in the highly species-rich Indo-Malayan rain forest, has considerable capacity for producing local endemics, making it particularly suitable for studying diversity on a local scale. We sampled Cyrtandra species from one community on Mount Kerinci, Sumatra, and phylogenetic analyses of ITS sequences suggest that this community is an assembly of three distinct phyletic lineages: (1) a group of herbaceous or subshrub plants of Bornean affinity, (2) one member of a group of widespread shrubs forming Cyrtandra section Dissimiles and (3) a second group of shrubs. The evolutionary origin of this community is therefore not a result of rapid and recent speciation: it is assembled from species resulting from a gradual accumulation of diversity through time (museum hypothesis), although one lineage shows evidence of more recent, continuing speciation than the other two. The community includes two distantly related, apparently endemic species, but there is no evidence for a local adaptive radiation. The protection of representative species from each lineage would allow the conservation of genetic diversity.  © 2004 The Linnean Society of London, Biological Journal of the Linnean Society , 2004, 81 , 49–62.