Inhibitory effects of different quantitative compositions of Hymenaea leaf resins on a generalist herbivore Spodoptera exigua

The hypotheses that quantitative variation in leaf resins in the leguminous genus Hymenaea may partially be a response to insect predation was tested in feeding experiments with the generalist herbivore, the beet armyworm, Spodoptera exigua Hübn (Noctuidae). Leaf resins of all Hymenaea species are comprised of essentially the same suite of sesquiterpene hydrocarbons, but discrete quantitative patterns have been classified as Compositional Types based on the amounts of major components. In this work pure extracts of leaf resins of Type I (high - and β-selinene), Type II (intermediate amounts of -and β-selinene and caryophyllene) and Type III (high caryophyllene) were incorporated into an artificial diet for the insects at 1 and 3.2% (dry wt). Resin Type treatments produced differential dose-dependent effects on growth rate (lower larval weights and increased time to pupation) and in mortality. More significant inhibitory effects occurred in Compositional Types with a predominance of a single compared (i.e. Types I and III). Significantly higher mortality occurring in Type III treatments suggests that caryophllene may have higher potential toxicity than - and β-selinene for S. exigua. These experiments indicate that feeding by generalist herbivores could be a factor determining quantitative compositional variation: (a) among populations; (b) during the development of leaves; (c) in the spatial distribution within the leaves; and (d) between parent tree and seedling progeny.     

Rate of acclimation of the tropical salt-marsh fish Cyprinodon dearborni to temperature changes

The acclimation rates of temperature changes in Cyprinodon dearborni, collected from Laguna Los Patos, Cumana, Venezuela, were determined by the critical thermal maximum method. At an increase in temperature (from 24 to 31°C) fish started to gain acclimation level after 3 hours and took 3 days to fully get up to a higher level of resistance to heat death; however, at a decrease in temperature (from 3 t to 24°C) fish began to lose its acclimation level after 12 days and required 39 days to reach a lower level of resistance to thermal death.     

The genusPicris (Asteraceae,Lactuceae) in Tropical Africa

Three species of the genusPicris L. are native in Tropical Africa:P. abyssinica Sch. Bip. (Ethiopia),P. xylopoda Lack, spec. nova (Nigeria, Ethiopia) andP. humilis DC. (Senegal, Mali). There are indications that the two perennial species,P. abyssinica andP. xylopoda, are related to and have evolved from a primitive Central Asiatic stock in a manner parallel to many African species ofCrepis L.P. humilis, on the other hand, is a small annual plant with a high number of derived characters. The introduced species of European origin growing south of the Sahara are briefly mentioned.     

Assessing Methods for Developing Phosphorus Desorption Isotherms from Soils using Anion Exchange Membranes

Developing desorption isotherms for inorganic phosphorus (P) is a time-consuming and non-standardized procedure. Anion exchange membranes (AEMs) have been successfully used in studies of P desorption kinetics and total membrane-desorbable P, but rarely have they been used for developing P desorption isotherms. Our study had two objectives: (1) to evaluate the suitability of using multiple strips of AEMs (termed the Multiple AEM Method) to develop P desorption isotherms; and (2) to compare the Multiple AEM Method with a sequential-extraction approach using AEMs (termed the Sequential AEM Method) to determine if the manner in which AEMs were used would influence the slope of the desorption isotherm, i.e. the partition coefficient. Both methods yielded well-defined, but numerically different desorption isotherms for all levels of sorbed P. However, estimated K _d values among methods were equivalent in the low and medium levels of P sorbed. The Multiple AEM method was quicker than the Sequential AEM method, but both gave similar K _d values in an agriculturally significant range of soil solution concentrations. These methods should be tested on a range of soil type to determine their suitability in developing P desorption isotherms and to move toward method standardization for desorption isotherms.     

Limitation of seedling growth by potassium and magnesium supply for two ectomycorrhizal tree species of a Central African rain forest and its implication for their recruitment

In the ectomycorrhizal caesalpiniaceous groves of southern Korup National Park, the dominant tree species, Microberlinia bisulcata, displays very poor in situ recruitment compared with its codominant, Tetraberlinia bifoliolata. The reported ex situ experiment tested whether availabilities of soil potassium and magnesium play a role. Seedlings of the two species received applications of K and Mg fertilizer in potted native soil in a local shade house, and their responses in terms of growth and nutrient concentrations were recorded over 2 years. Amended soil concentrations were also determined. Microberlinia responded strongly and positively in its growth to Mg, but less to K; Tetraberlinia responded weakly to both. Added Mg led to strongly increased Mg concentration for Microberlinia while added K changed that concentration only slightly; Tetraberlinia strongly increased its concentration of K with added K, but only somewhat its Mg concentration with added Mg. Additions of Mg and K had small but important antagonistic effects. Microberlinia is Mg‐demanding and apparently Mg‐limited in Korup soil; Tetraberlinia, whilst K‐demanding, appeared not to be K‐limited (for growth). Added K enhanced plant P concentrations of both species. Extra applied Mg may also be alleviating soil aluminum toxicity, and hence improving growth indirectly and especially to the benefit of Microberlinia. Mg appears to be essential for Microberlinia seedling growth and its low soil availability in grove soils at Korup may be an important contributing factor to its poor recruitment. Microberlinia is highly shade‐intolerant and strongly light‐responding, whilst Tetraberlinia is more shade‐tolerant and moderately light‐responding, which affords an interesting contrast with respect to their differing responses to Mg supply. The study revealed novel aspects of functional traits and likely niche‐partitioning among ectomycorrhizal caesalps in African rain forests. Identifying the direct and interacting indirect effects of essential elements on tropical tree seedling growth presents a considerable challenge due the complex nexus of causes involved.     

Área de Conservación Guanacaste,northwestern Costa Rica: Converting a tropical national park to conservation via biodevelopment

The ~30,000 hectare classical Costa Rican Parque Nacional Santa Rosa has used about 35 years and $107 million to be converted to the 169,000 ha government-NGO hybrid Área de Conservación Guanacaste (ACG). This semi-decentralized conservation entity has today a staff of ~150 paraprofessional resident Costa Ricans, biodeveloping at least 650,000 multicellular species (Eucaryotes) into perpetuity for ACG survival through being integrated with its local, regional, national, and international society. ACG began in 1985 as an ongoing exercise of landscape-level ecosystem rescue and restoration of a continuous swath from 6 km out in the Pacific ocean, across dry forested lowlands, up and over the volcanic Cordillera Guanacaste, and down into the rain-forested Caribbean lowlands. It is being impacted by climate change, yet its diverse ecosystems hold hope for major biodiversity survival, albeit in new community assemblages. It quickly became simultaneously a biophysical challenge and an administratively novel challenge in decentralized conservation in a democratic tropical country. ACG specializes at being managed by on-the-job stimulated and trained residents with minimal formal education, searching for ways to involve ACG in its society without damaging its wildness, and pioneering ways to render wild biodiversity to being a welcome member at society's negotiating table. It continues to pay its bills through government subsidy, generous donors, payments for services, project grants, and huge in-kind contributions from mutualisms. ACG hopes that the concept will spread south–south to other tropical countries while they still have some of their wild biodiversity with which to integrate.     

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.