Influence of host-plant sex and habitat on survivorship of insect galls within the geographical range of the host-plant

Abstract

This study evaluated the influence of host-plant sex and habitat on the abundance and survivorship of the galling Psyllidae, Neopelma baccharidis Burckhardt 1987 (Homoptera) on several populations of the host-plant Baccharis dracunculifolia De Candole (Asteraceae) within its geographical range in Brazil. Three questions were addressed: (i) what is the effect of host-plant sex and the habitat occupied by Baccharis dracunculifolia on the abundance of galls induced by Neopelma baccharidis? Plant sex did not affect the abundance of galls per plant while host-plant habitat had a significant effect. Twice as many galls were found on plants in xeric habitats as on plants in mesic habitats; (ii) what is the influence of host-plant sex and habitat on the survivorship rates of Neopelma baccharidis? Populations occurring in mesic habitats suffered 3 times greater mortality than populations in xeric habitats; (iii) does the richness and abundance of inquilines of Neopelma baccharidis galls vary between habitats? Habitat type did not influence the pattern of inquiline richness. The abundance of inquilines was also very similar between xeric (51%) and mesic habitats (49%). This study suggests that host-plant sex did not affect the abundance of the psyllid galls on B. dracunculifolia, while the habitat occupied by the host-plant had a strong influence on gall abundance, with more galls occurring in xeric habitats than in mesic habitats. Otherwise, no effect of habitat was found on gall inquilines. The mechanism generating the pattern of gall abundance was the differential mortality of galls between habitat types.