Bruno Edgar Irgang

Composição florística das formações vegetais sobre uma turfeira topotrófica da planície costeira do Rio Grande do Sul, Brasil

Turfeiras topotroficas caracterizam-se como corpos de aguas rasas, permanente ou periodicamente alagados por agua do lencol freatico, percolada atraves do solo inorgânico das terras altas adjacentes a depressao central da turfeira. Possuem solos orgânicos e a cobertura vegetal e dominanda por fanerogamas aquaticas emergentes. Este estudo visou o levantamento da diversidade especifica e caracterizacao das principais formacoes vegetais ao longo de duas transeccoes de 200m em uma turfeira topotrofica na localidade de Domingos Petrolini (Rio Grande, RS). Em marco/1998, o total de 48 especies vegetais (30 familias) foram encontradas nas 40 parcelas de 5m × 2m observadas nas duas transeccoes efetuadas. Cerca de 56% das especies eram plantas aquaticas herbaceas (submersas, flutuantes ou emergentes) e apenas 10% arbustos ou arvores. Sete especies dominaram a cobertura vegetal (Eupatorium tremulum, Eryngium pandanifolium, Blechnum brasiliense, Rhynchospora sp., Xyris jupicai, Utricularia gibba e Cladium jamaicense). Quatro formacoes vegetais tipicamente distribuidas em relacao a topografia e a distância do lencol freatico foram caracterizadas: (1) banhados do capim-navalha Cladium jamaicense, drenados apenas no verao, ocupam a depressao central da turfeira (DCT); (2) planos medios de Gravatas/Caraguatas (Eryngium pandanifolium) associados a samambaia Blechnum brasiliense (+0,5 a +1,5m da DCT); (3) bosques marginais de arbustos palustres (+1 a +3m da DCT) sao dominados por Eupatorium tremulum; e (4) campos de turfa recobertos por ciperaceas de pequeno porte, gramas boiadeiras e botoes-de-ouro (Xyris jupicai) ocupam a borda do afloramento da turfa (+3 a +4m da DCT).

Estrutura floral das angiospermas usadas por Heliconius erato phyllis (Lepidoptera, Nymphalidae) no Rio Grande do Sul, Brasil

FLOWER STRUCTURE OF ANGIOSPERMS USED BY HELICONIUS ERATO PHYLLIS (LEPIDOPTERA, NYMPHALIDAE) IN RIO GRANDE DO SUL STATE, BRAZIL. A field survey of flowering plants used as food resource by the adults of Heliconius erato phyllis (Fabricius, 1775) was carried out in four sites located in Rio Grande do Sul state, Brazil. Samples were taken in preserved areas of the Atlantic Rain and Myrtaceae forests, an Eucalyptus plantation, and an urban park. Adult feeding frequencies on flowers were registered monthly from December 1996 to May 1997, on plants located on previously marked 200 m long transects. Flowers on which H. erato phyllis fed in the field were collected, drawn and morphometrically characterized. Feeding was registered on flowers of twenty-three species, of which seventeen are new records for H. erato in Brazil . The use of a given plant varied among localities, as a function of its corresponding abundance. The most visited flowers were those of Lantana camara L. and Stachytarpheta cayennensis (Rich.) Vahl, followed by Dahlia pinnata Voss in the urban site. The data suggest the existence of size and shape convergence between the proboscis and the small, tubular flowers upon which H. erato phyllis feeds. They also indicate that H. erato phyllis adults have an opportunistic nectar feeding / pollen gathering habit, using several of those flowers available in a given time and locality that fit such a morphometrical pattern. Since plant species of both primitive and derived families are used, there is no indication that phylogenetic constraints play a major role in this association, nor that color of flowers, growth pattern or size of the plants are relevant in determining their use by H. erato phyllis.

Are there evidences of a complex mimicry system among Asclepias curassavica (Apocynaceae), Epidendrum fulgens (Orchidaceae), and Lantana camara (Verbenaceae) in Southern Brazil?

The goal of this paper was to test the presence of mimicry in Asclepias curassavica L., Epidendrum fulgens Brong., and Lantana camara L. The study was carried out at the Parque Estadual de Itapeva, RS, southern Brazil, from 2004 to 2006. Flowering period of each of the three species was followed up; focal observations of butterflies visiting flowers, from fixed point and during random walks were carried out. We also estimated the frequency of pollinaria removal in the orchid, as well as its mode of reproduction. All these variables were important for testing the mimicry hypothesis. Despite some temporal coincidences in the flowering period of two plants in the system, there was no statistical association among the three plants as to flowering period. Twenty-nine species of butterflies, as potential pollinators, were recorded, particularly Agraulis vanillae maculosa, Dryas iulia alcionea, Urbanus simplicius, Tegosa claudina, and Heliconius erato phyllis, which were the more frequent visitors of the three plants. There was association between the number of visits to L. camara and E. fulgens, based on Pearson correlation (r = 0.4603; n = 19; P = 0.0473). Pollinaria removal of E. fulgens was low, as measured by the percentage of removal (range: 0 - 10%). The analysis of the mode of reproduction of this orchid showed its pollinator-dependence, since no fruits were formed by spontaneous self-pollination. In contrast, the percentage of fruit set that resulted from geitonogamy and xenogamy was, in average, 86%. The results here shown are not conclusive as to the occurrence of a mimicry system among the three plants.

A ocorrência do mutualismo facultativo entre Dyckia maritima Backer (Bromeliaceae) e o cupim Cortaritermes silvestrii (Holmgren), Nasutitermitinae, em afloramentos rochosos no Parque Estadual de Itapuã, Viamão, RS

The presence of colonies of C. silvestrii is common, both on the rock surface and at islands of vegetation. At Morro da Grota1 station, 92,0 % of the termite nests on rocky outcrops and at island of vegetation are associated with this bromeliad. These nests are associated with D. maritima, in 31,2 % of the islands where this bromeliad occurs. At these island communities, the comparison between the substrata where D. maritima occurs, the litolic Waldemar & Irgang: Mutualismo facultativo entre Dyckia maritima e o cupim Cortaritermes silvestrii humic soil existing under the mantle of the moss Campylopus spp. and the substratum produced by termites indicates that this possesses higher levels of the nutrients P, K, Ca, Mg, Zn and Mn, CEC and higher fine particles content, mainly silt. The establishment of D. maritima rosettes on great termite nests increase their value of relative coverage at islands inside areas between 2,7 to 8,0 m2. This fact is attributed to the improvement physical-chemistry of the substratum and the increase of surface and volume to be colonized for the Bromeliad. It provides for greater competitiveness at this species in relation to other vegetal species. The features presented for the interaction between this termite and D. maritima, for the first time described in literature, lead to the classification of this ecological relationship as facultative mutualism. The set of observations constitute a temporal model of development of this mutualism at islands vegetation, whose phases, initial and advanced are described.