Revisions of Pterogastra and Schwackaea (Melastomataceae: Melastomeae)

The closely related neotropical melastomean genera Pterogastra and Schwackaea are revised, the species illustrated, and their distribution mapped. Schwackaea is maintained as a monotypic genus because it is readily distinguished from all other melastomes by its 8-winged capsule. This weedy little plant occurs from Mexico throughout Central America, chiefly on the Pacific slope, to northern Colombia and on Cocos Island and grows in natural or man-made savannas from sealevel to 2000 m altitude. Two species are recognized in Pterogastra and one new combination, P. divaricata spp. glabra , is made. Pterogastra is characterized by distinctly 4- or 5-winged capsules, unlike those of Schwackaea or any other New World melastome. The more widespread species occurs in Colombia, Venezuela, Guyana, Ecuador, and Peru at altitudes between sealevel and 2600 m in natural or disturbed grasslands. The second species is endemic in southwestern Venezuela and is confined to natural savannas at low altitudes.     

Pollinators of tropical dioecious angiosperms

Dioecy is frequent in tropical forests. It has been suggested that small, unspecialized pollinators are among the factors responsible for gender separation in this habitat. The underlying assumption is that poor fliers and/or communal foragers frequently effect selfing which in turn, given sufficiently severe inbreeding depression, should favor the establishment of dioecy. At least 10% of the genera of the angiosperms includes dioecious species; in tropical flowering plants, however, pollinators are reliably known only in a few species. Whereas temperate dioecious species commonly are wind- or water-pollinated, anemophily is less important in tropical forests, but occurs in at least 30 dioecious genera. Our survey of tropical dioecious zoophilous species in 29 genera (in 21 families) for which detailed pollination information is available shows that these species have specialized flowers adapted to specific pollinators rather than generalized flowers suitable for diverse insects. Known pollinators include solitary and eusocial bees, beetles, moths, flies, wasps (including fig wasps), and rarely bats and birds, and cover a wide range in animal size and locomotive capabilities. Floral rewards comprise pollen, nectar, stylar mucilage, nutritious tissues, brood-places, and resins. About a third of the species offer no reward in the female morph, pollination by deceit apparently being common. Our data thus do not support the hypothesis that there is a broad correlation between a dioecious breeding system and unspecialized pollination, although such a correlation may be found in certain taxa. Specialized plant-pollinator relationships seem as critical in dioecious plants in tropical forests, where individuals often grow far apart, as they are in tropical plants with other breeding systems.     

Superparasitism and sex ratio in the solitary parasitoidEpidinocarsis lopezi

Highly variable sex ratios are found in the solitary parasitoidEpidinocarsis lopezi, both in the field and in a mass-rearing situation. Superparasitism is one of a number of factors which can influence sex ratios in parasitoid Hymenoptera. We show that superparasitism inE. lopezi is common in the field. Sex allocation decisions when parasitizing unparasitized hosts are not different from those with parasitized hosts; neither does differential mortality occur between the sexes in superparasitized hosts. Therefore superparasitism does not contribute to the variable sex ratio ofE. lopezi. Both the occurrence of superparasitism and the sex produced when ovipositing are shown to be functional forE. lopezi.     

Mutualistic interactions shape global spatial congruence and climatic niche evolution in Neotropical mimetic butterflies

Understanding the mechanisms underlying species distributions and coexistence is both a priority and a challenge for biodiversity hotspots such as the Neotropics. Here, we highlight that Müllerian mimicry, where defended prey species display similar warning signals, is key to the maintenance of biodiversity in the c. 400 species of the Neotropical butterfly tribe Ithomiini (Nymphalidae: Danainae). We show that mimicry drives large-scale spatial association among phenotypically similar species, providing new empirical evidence for the validity of Müller's model at a macroecological scale. Additionally, we show that mimetic interactions drive the evolutionary convergence of species climatic niche, thereby strengthening the co-occurrence of co-mimetic species. This study provides new insights into the importance of mutualistic interactions in shaping both niche evolution and species assemblages at large spatial scales. Critically, in the context of climate change, our results highlight the vulnerability to extinction cascades of such adaptively assembled communities tied by positive interactions.     

Linkage of Wiskott-Aldrich syndrome with three marker loci,DXS426, SYP and TFE3, which map to the Xp11.3–p11.22 region

Linkage analysis was performed in 19 families segregating for the Wiskott-Aldrich syndrome (WAS) and in 1 family with X-linked thrombocytopenia using nine polymorphic DNA markers spanning the interval DXS7-DXS14. The results confirm close linkage of WAS to the DXS7, TIMP, OATL1, DXS255, DXS146, and DXS14 loci and reveal three additional marker loci, DXS426, SYP, and TFE3, to be closely linked to WAS. The linkage data are also consistent with the localization of X-linked thrombocytopenia to the same chromosomal region as WAS and support localization of the WAS gene between the TIMP and DXS 146 loci. However, the data were insufficient for positioning these disease genes with respect to the four marker loci that map within this latter interval. Analysis of recombination events between the marker loci place the TFE3 gene distal to DXS255 and favor the marker loci order Xpter-DXS7-(DXS426, TIMP)-(OATL1, SYP, TFE3)-DXS255-DXS146-DXS14.     

Effect of dark treatment on the starch degradation and the agar quality of cultivated Gracilariopsis lemaneiformis (Rhodophyta,Gracilariales) from Venezuela

The effect of darkness and ammonia on Gracilariopsis lemaneiformis agar yield and quality was studied. Plants were cultivated under controlled conditions in the laboratory and fertilized with ammonia prior to a month storage in the dark. Starch inclusions are known to interfere with the mechanical properties of the isolated agar. The starch content of algal tissue and the activities of the floridean starch phosphorylase and -glucosidase were measured during this storage period as a way to follow the enhancement of starch degradation in the absence of light, and to measure the effect of darkness on the content and quality of the synthesized agar. The agar yield, gel strength, 3,6-anhydrogalactose, sulphate and starch content were considerably affected by this dark treatment. The values obtained reflect a pattern of optimization of agar quality when Gracilariopsis lemaneiformis was stored in the dark. The isolated agar following dark treatment is less contaminated by starch inclusions. This is shown by the improvement in the agar yield and quality, the nutrient status of the plant and the reduction of the starch content.Abbreviations DW: Dry weight - FW: Fresh weight - S: Sulphate - 3,6-AG: 3,6-anhydrogalactose - GS: Gel strenght at 1.5% concentration - CX: Cold extract at 25 °C - A: Autoclaved extract at 121 °C - MW: Molecular weight - PFD: Photon flux density