Cladocera (Crustacea) from Nicaragua

Thirty-one Cladocera taxa are recorded from lakes, rivers and ponds of Western Nicaragua. They include Alona bromelicola sp. nov. found in water accumulations in epiphytic Bromeliads. The Cladocera recorded are neotropical and circumtropical. Other invertebrates found are also listed.     

Occurrence of arbuscular mycorrhizal fungi in bromeliad species from the tropical Atlantic forest biome in Brazil

The mycorrhizal status of epiphytic, rupicolous, and terrestrial bromeliad species from the Brazilian Atlantic Rain Forest has been examined. Roots of 13 species of bromeliads were analyzed for the presence of mycorrhizal structures such as arbuscules, hyphae, and vesicles as well as other fungal structures. Rhizosphere soil was sampled to identify arbuscular mycorrhizal fungal (AMF) species associated only with terrestrial bromeliad species. Most specimens collected were epiphytic bromeliads in the genera Aechmea, Bilbergia, Nidularium, Tillandsia, and Vriesea. Differentiating structures of AMF were found in only three species of bromeliads. The pattern of mycorrhizal colonization was mainly internal, and external mycelium and arbuscules were observed only in the terrestrial Nidularium procerum. Root endophytes with dark brown septate mycelium, thin external hyphae, and Rhizoctonia-like sclerotia were also detected in some root segments. A total of ten spore morphotypes were recovered from the rhizosphere of N. procerum, with Acaulospora mellea, A. foveata, and Glomus sp. being the most common species recovered. Our study demonstrated that most of the epiphytic species are not associated with AMF. We attribute this mainly to the exposed bare root conditions found in epiphytic bromeliads.     

Bottom-up regulation of bacterial growth in tropical phytotelm bromeliads

Evaluating the factors that regulate bacterial growth in natural ecosystems is a major goal of modern microbial ecology. Phytotelm bromeliads have been used as model ecosystems in aquatic ecology as they provide many independent replicates in a small area and often encompass a wide range of limnological conditions. However, as far as we know, there has been no attempt to evaluate the main regulatory factors of bacterial growth in these aquatic ecosystems. Here, we used field surveys to evaluate the main bottom-up factors that regulate bacterial growth in the accumulated water of tank bromeliads. Bacterial production, water temperature, water color, chlorophyll-a, and nutrient concentrations were determined for 147 different tank bromeliads in two different samplings. Bromeliad position and the season of sampling were also noted. Bacterial production was explained by ion ammonium concentration and water temperature, but the total variance explained was low (r ² = 0.104). Sampling period and bromeliad position were included in additional models that gave empirical support for predicting bacterial production. Bromeliad water tanks are extremely variable aquatic ecosystems in space (among bromeliads) and time (environmental conditions can change within hours), and it is well known that bacterial production responds rapidly to environmental change. Therefore, we concluded that several factors could independently regulate bacterial growth in phytotelm bromeliads depending on the characteristics of each bromeliad, such as location, amount of detritus, and ambient nutrient concentrations. A clear bottom-up limitation pattern of bacterial production in tropical phytotelm bromeliads was not found. Handling editor: Luigi Naselli-Flores     

Tissue culture for the conservation and mass propagation of <Emphasis Type="Italic">Vriesea reitzii</Emphasis> Leme and Costa,a bromeliad threatened of extinction from the Brazilian Atlantic Forest

The Brazilian Atlantic Forest biome is considered a hotspot of biodiversity. It is estimated that today the remaining primary vegetation covers only 7.5% of its original area. Bromeliad species are important components of this biome. Some of these species are endemic, like the highly endangered Vriesea reitzii. Tissue culture techniques have been often employed for the mass propagation and conservation of threatened bromeliad species. In the present work we describe a procedure for the micropropagation and in vitro conservation of V. reitzii. Seedling explants were cultured on MS and LPm liquid media supplemented with BA, NAA and GA₃. The induction and multiplication of shoots were observed in the MS medium supplemented with NAA (2 μM) and BA (4 μM). The best conditions for maintenance and conservation of shoots were half-strength or MS medium. Shoot elongation was observed in MS medium supplemented with GA₃ (10 μM). MS medium supplemented with NAA (1 μM) and BA (2 μM) enabled an efficient proliferation system. The acclimatization of shoots longer than 2 cm resulted in 100% survival rate.     

Morphological variation of Aechmea distichantha (Bromeliaceae) in a Chaco forest: habitat and size-related effects

Plants show different morphologies when growing in different habitats, but they also vary in their morphology with plant size. We examined differences in sun- and shade-grown plants of the bromeliad Aechmea distichantha with respect to relationships between plant size and variables related to plant architecture, biomass allocation and tank water dynamics. We selected vegetative plants from the understorey and from forest edges of a Chaco forest, encompassing the whole size range of this bromeliad. Plant biomass was positively correlated with most architectural variables and negatively correlated with most biomass allocation variables. Understorey plants were taller and had larger diameters, whereas sun plants had more leaves, larger sheath area, sheath biomass and sheath mass fraction. All tank water-related variables were positively correlated with plant biomass. Understorey plants had a greater projected leaf area, whereas sun plants had higher water content and evaporative area. Plasticity indices were higher for water-related than for allocation variables. In conclusion, there were architectural and biomass allocation differences between sun- and shade-grown plants along a size gradient, which, in turn, affected tank water-related variables.     

观赏凤梨高效离体快繁影响因素的研究

以侧芽为外植体材料,对其组织培养的各个阶段进行了研究。结果表明:品种对外植体的污染率、褐变率、芽诱导率及丛生芽增殖倍数均有显著影响;外源激素的种类和浓度在芽诱导分化、增殖、生根等各个阶段都是主要的影响因素;外植体在1/2MS+NAA0.2mg·L~(-1)+6-BA2mg·L~(-1)上,48d后芽开始分化,诱导率为40%,平均芽分化数为6个,诱导分化效果最好;芽增殖培养阶段,若培养基中仅含6-BA,且浓度在0~4mg·L~(-1)之间,芽增殖倍数随其浓度增大而增大;若培养基中仅含NAA,且其浓度为0.2mg·L-1时,增殖倍数最大;培养基中同时添加6-BA和NAA,比单独添加6-BA或NAA时,芽的增殖效果好,且在6-BA3mg·L~(-1)+NAA0.5mg·L~(-1)的MS培养基上,G.dissitisflora和G.‘Claret’增殖倍数最大,分别为5.24和3.84;在任何相同的培养基上,G.dissitisflora的增殖倍数显著高于G.‘Claret’;小苗在含有NAA0.5mg·L~(-1)+IBA0·5mg·L~(-1)的生根培养基上生长,生根率可达91.03%,平均根数为5.3条/株,生根效果较好。     

Species richness and ecophysiological types among Bolivian bromeliad communities

The relationship between diversity and composition of neotropicalbromeliad communities and abiotic and autecological factors is still poorlyunderstood. In this study, I related point diversity (mean species number per400 m² plot), diversity (total species number persite), representation of life-forms (epiphytes, terrestrials, saxicoles), andsix ecophysiological types of bromeliads at 74 forest sites in the BolivianAndes and adjacent lowlands to 12 environmental factors reflecting mostlyclimatic conditions. A total of 192 species, including 108 epiphytes, 106saxicoles, and 49 terrestrials, were recorded. Extrapolation revealed that theactual total species number in the region is at least 24% higher than recorded,especially among terrestrial (71%) and saxicolous (40%) species. Epiphytes weremore fully sampled because of their tendency towards larger range size andbecause they are distributed more evenly where they occur. Overall, theenvironmental factors explained up to 61% of the observed variance, reflectingall expected relationships such as the increase of tank bromeliads in wethabitats and of atmospheric bromeliads in arid regions. Point diversity almostalways showed higher regression coefficients than diversity, possibly as aresult of more complete sampling in small plots and because the abundance ofindividual species (which influences point diversity) may be more closelyrelated to abiotic factors than species richness. Despite somewhat lower diversity in arid areas, point diversity peaked in dry habitats,presumably due to the scarcity of competing epiphytic orchids, ferns, and aroidsthat lack the extreme adaptation of bromeliads to drought stress and lownutrient availability. The decline of epiphytic bromeliad diversity at highelevations appears to be linked to low temperatures, particularly increasingfrost frequency. It is hypothesized that the low diversity of bromeliads inhumid tropical lowland forests is caused by low photosynthetic rates due to highwater stress and low light availability combined with high respiration losses.In combination, these factors would impede the maintenance of a positive carbonbalance.     

The role of hybridization and introgression in maintaining species integrity and cohesion in naturally isolated inselberg bromeliad populations

• Hybridization is a widespread phenomenon present in numerous lineages across the tree of life. Its evolutionary consequences range from effects on the origin and maintenance, to the loss of biodiversity.
• We studied genetic diversity and intra‐ and interspecific gene flow between two sympatric populations of closely‐related species, Pitcairnia flammea and P. corcovadensis (Bromeliaceae), which are adapted to naturally fragmented Neotropical inselbergs, based on nuclear and plastidial DNA.
• Our main results indicate a strong reproductive isolation barrier, although low levels of interspecific gene flow were observed in both sympatric populations. The low rates of intraspecific gene flow observed for both P. corcovadensis and P. flammea populations corroborate the increasing body of evidence that inselberg bromeliad species are maintained as discrete evolutionary units despite the presence of low genetic connectivity. Nuclear patterns of genetic diversity and gene flow revealed that hybridization and introgression might not cause species extinction via genetic assimilation of the rare P. corcovadensis.
• In the face of reduced intraspecific gene exchange, hybridization and introgression may be important aspects of the Pitcairnia diversification process, with a positive evolutionary impact at the bromeliad community level, and thus contribute to increasing and maintaining genetic diversity in local isolated inselberg populations.

     

Infructescence size has a larger effect than light environment on the abundance of different arthropod feeding guilds dwelling on the infructescences of a terrestrial bromeliad in a xerophytic forest

Bromeliads are a conspicuous feature of many Neotropical xerophytic forests. Bromelia serra is an understory bromeliad living in xerophytic forests of the Humid Chaco, which shows high phenotypic plasticity when exposed to different environmental conditions. Its infructescences carry many fleshy fruits that are colonized by arthropods from different feeding guilds. We used structural equation modeling and redundancy analysis to evaluate the influences of light environment, plant size, and infructescence size on the abundance of five different feeding guilds of arthropods dwelling on the infructescences (‘fruit-secretion feeders,’ ‘infructescence-detritus feeders,’ ‘predators,’ ‘pulp feeders’ or ‘seed feeders’). Plant size was negatively associated with canopy openness, whereas infructescence size was positively associated with plant size. The abundance of all feeding guilds, except fruit-secretion feeders, were positively associated with infructescence size.     

Recolonization of vascular epiphytes in a shaded coffee agroecosystem

Aim: Shaded coffee plantations constitute an important refuge for biodiversity. Despite the fact that epiphytic plants form a significant component of these agroecosystems, their removal from the shade trees is commonplace in Latin America. To what extent does the epiphyte community recover from this severe disturbance? Location: Shaded coffee agroecosystem in Veracruz, Mexico (19°28′03″ N, 96°55′58″ W; 1200 m asl). Methods: We assessed the diversity, biomass and recolonization patterns of vascular epiphytes in shade trees, 8‐9 yr after complete epiphyte removal (E^?), and in control ‘non‐removal’ sites (E⁺). In order to evaluate the effects of prior epiphyte removal, all vascular epiphytes were completely removed from 10 trees per treatment (E^? and E⁺); all epiphyte species collected were identified and dry biomass measured. Results: Eight to nine years after removal, epiphyte biomass in the E^? shade trees was 35% of that found in the control sites. A total of 55 epiphyte species, belonging to 12 families, were registered; 40 in E^?, and 48 in E⁺. Six species belonging to Bromeliaceae, Orchidaceae, Cactaceae and Araceae accounted for 75% of the biomass in E⁺ while six species of bromeliads accounted for 76% of the biomass in E^?. Some bromeliads proliferated following disturbance; however, ferns showed lower recovery. Conclusions: Epiphyte community recovery, in terms of biomass and diversity, is considerably higher in the coffee plantation than has been previously reported for other tropical ecosystems. Epiphyte recolonization patterns reflected both the abundance of species in the surrounding matrix and certain species‐specific traits. For such agroecosytems to function as effective reservoirs of epiphyte diversity, epiphyte stripping should be avoided.