Phytophagous insect fauna tracks host plant responses to exotic grass invasion

The high dependence of herbivorous insects on their host plants implies that plant invaders can affect these insects directly, by not providing a suitable habitat, or indirectly, by altering host plant availability. In this study, we sampled Asteraceae flower heads in cerrado remnants with varying levels of exotic grass invasion to evaluate whether invasive grasses have a direct effect on herbivore richness independent of the current disturbance level and host plant richness. By classifying herbivores according to the degree of host plant specialization, we also investigated whether invasive grasses reduce the uniqueness of the herbivorous assemblages. Herbivorous insect richness showed a unimodal relationship with invasive grass cover that was significantly explained only by way of the variation in host plant richness. The same result was found for polyphagous and oligophagous insects, but monophages showed a significant negative response to the intensity of the grass invasion that was independent of host plant richness. Our findings lend support to the hypothesis that the aggregate effect of invasive plants on herbivores tends to mirror the effects of invasive plants on host plants. In addition, exotic plants affect specialist insects differently from generalist insects; thus exotic plants affect not only the size but also the structural profile of herbivorous insect assemblages.

Psammophilous halacarid mites (Trombidiformes, Halacaridae) from the North Coast of Sao Paulo State, Brazil

Five halacarid species are reported from the Brazilian coast for the first time. Scaptognathides delicatulus, formerly known only from its type locality in Kuwait; Scaptognathus gibbosus, known from Galapagos and Somalia; and Scaptognathus insularis known from northeastern Australia, have their distributions extended. Along with these new records, Halacaroides antoniazziae sp. nov. and Acarochelopodia caissara sp. nov. are described. Halacaroides antoniazziae sp. nov. differs from its congeners by the presence of three subgenital setae in males and none in females, 41-44 perigenital setae and two posterior external genital acetabula in males. Acarochelopodia caissara sp. nov. has a rounded anterior epimeral plate margin, the posterior epimeral plates are partially divided into two halves but anteriorly joined by a narrow band, the dorsal setae on tarsus I are grouped 1:2, and the anterior and posterior dorsal plates have a length: width ratio of 1.61-1.77 and 1.60-1.70, respectively.