Efeitos do sexo, do vigor e do tamanho da planta hospedeira sobre a distribuição de insetos indutores de galhas em Baccharis pseudomyriocephala Teodoro (Asteraceae)

Abstract

ABSTRATC.Effects of gender, vigor and size of the host plant Baccharis pseudomyriocephala Teodoro (Asteraceae) on gallinducing insect distribution. Several hypotheses have been proposed to explain the patterns of host plant utilization by herbivorous insects in natural communities. We tested four hypotheses aiming to understand the pattern of attack by gallinducing insects on the dioecious shrub, Baccharis pseudomyriocephala (Asteraceae). The shrub occurs in the Parque Estadual do Itacolomi, Southeastern Brazil, and supports ten species of galling insects. The following hypotheses were tested: i) male plants are more attacked by galling insects than female plants; ii) larger plant modules are preferentially attacked by galling insects; iii) galling insects perform better on larger modules than on smaller modules; iv) galling insects increase in abundance with meristematic availability. To address these questions, 240 plants (120 of each sex) were sampled in both reproductive and vegetative periods. We recorded the growth rate (4 cm), inflorescence and fruit production, attack rates of the galling insects, and their survivorship and mortality per shoot (module). Modules were separated into size classes (cm) and analyzed by regressions and ANCOVAs. Module size and reproductive effort were positively correlated with host plant size. We did not observe any effect of host plant gender on either variables. In the same way, host plant sex did not show any influence on the abundance and richness of galling insects. Although the abundance of galling insects showed a positive correlation with shoot size, the trend disappeared when the analyses were performed taking into consideration the number of galls per unit of growth (number of galls/cm of shoot) or biomass (number of galls/dry weight). Larval survivorship was not influenced by shoot size. Also, we observed that the abundance of one species of hemipteran galling insect showed a positive relation with leaf biomass. Therefore, we conclude that gender and vigor of this plant species do not influence the community structure of its galling herbivores.KEYWORDS. Dioecy; galling insects; insect herbivore; plant architecture; plant vigour hypothesis. INTRODUÇÃOEstudos sobre interações inseto-planta consideram que a riqueza de espécies em comunidades de insetos herbívoros é influenciada pelas características de suas plantas hospedeiras, como área de distribuição e sua complexidade estrutural (STRONG et al. 1984). A qualidade e a quantidade de recursos oferecidos pela planta hospedeira também exercem papel preponderante sobre a diversidade de insetos herbívoros (e.g. PRICE 1992). A hipótese do vigor de plantas (HVP) prevê que plantas ou suas partes mais vigorosas são preferencialmente selecionadas por fêmeas de insetos indutores de galhas como sítios de oviposição, por proporcionarem melhor performance larval da prole (PRICE 1991). O vigor é entendido como o crescimento de plantas ou módulos de plantas acima do crescimento médio de uma dada população (PRICE 1991). O tamanho da ...

The role of Senescent Stem-Galls over Arboreal Ant Communities Structure in Eremanthus erythropappus (DC.) MacLeish (Asteraceae) Trees

“…Six of the regions are near the municipality of Ouro Preto in the southern portion of the Espinhaço Range: 1) Itacolomi State Park (PEIT), 2) Environmental Protection Area of Andorinhas Waterfall (APA); 3) Uaimií State Forest (Uaimií), 4) populations along MG 356 Inconfidentes Highway (Rodovia); 5) Serra do Ribeiro (SRib); and 6) Private Natural Heritage Reserve -Caraça Sanctuary (Caraça). PEIT (20°22'30" S, 43°32'30" W) encompasses approximately 7,500 ha, with its highest point being the Itacolomi Peak at 1,772 m. Some mountain rainforest patches and Araucária trees complement the landscape (Araújo et al, 2003;IEF 2015). APA (20º22'34'' S, 43º29'27'' W) has an area of approximately 18,700 ha with an altitude of 1,300 m, and is located on the hills of Ouro Preto encompassing the headwaters of Rio das Velhas, a very important river in the state of Minas Gerais.…”

Senescent stem-galls in trees of Eremanthus erythropappus as a resource for arboreal ants

“…The study was conducted near the city of Ouro Preto (in Minas Gerais, Brazil) at four different locations: namely, in Itacolomi State Park (PEI), at Ribeiro Mountain, Brígida Mountain and in the area beside the MG-356 highway near the entrance to the city of Ouro Preto. The PEI (20°22'30"S, 43°32'30"W) spans approximately 7,000 ha and is composed mostly of low mountain rainforests, riparian vegetation, and quartzitic and ferruginous fields (Araújo et al 2003). The Serra do Ribeiro (20°27'55.4"S, 43°35'59"W) is composed of rocky formations, quartzitic soil and very similar rock field vegetation (Borges et al 2011).…”

Relationship between invertebrate fauna and bromeliad size

“…Samples of water were collected using a pipette (Lozovei and Silva, 1999). These measurements are used as estimators of the plant size (Kitching, 1987;Lopez et al, 1998, Richardson, 1999Araújo et al, 2003). Two numbered recipients were used for each individual, one containing the phytotelmata community preserved in the water from the plant, and the other containing the invertebrate fauna associated with the bromeliad leaves, preserved in 70% alcohol.…”