Long term oviposition preference and larval performance of Schizomyia macrocapillata (Diptera: Cecidomyiidae) on larger shoots of its host plant Bauhinia brevipes (Fabaceae)

Abstract

The Plant Vigor Hypothesis (PVH) proposes that natural selection on female oviposition choice results from higher fitness of larvae on more vigorous and larger plant modules. For six consecutive years we tested the PVH predictions by investigating the effect of shoot size of Bauhinia brevipes (Fabaceae) on the oviposition preference and offspring survival of the gall-midge Schizomyia macrocapillata (Diptera: Cecidomyiidae). Additionally, we analyzed the effects of bottom-up and top-down mortality forces on the system. The hypersensitive reaction (bottomup effect) accounted for more than 90% larval mortality of S. macrocapillata, making available few galls to be found and killed by natural enemies (top-down effect). Smaller shoots were always more abundant while longer shoots were rare. Nevertheless, the percent number of galls induced by S. macrocapillata was up to 10-fold greater on the largest shoots, corroborating the preference prediction of the PVH. Schizomyia macrocapillata should use over-exploit larger shoots to maximize the preference for, and consequently increase the performance on these shoots. Our results partially support the performance prediction of the PVH: (1) the observed survival was higher than expected on longer shoots, and (2) the ratio of survival per shoot was positively related with shoot length only in 2 years. Thus, we found a link between female preference and larval performance on large-sized shoots, at least in some years. The gall-midge attack pattern in this study might be an evolved response to maximize the female preference and increased larval performance on longer shoots of the host plant.

Gall wasp community response to fragmentation of oak tree species: importance of fragment size and isolated trees

“…The effects of habitat fragmentation on populations of gall inducing insects are poorly known (but see Chust et al 2007) and few long-term studies have analyzed gall inducing insect interactions (Santos et al 2008). Studies to date show no consistent response of gall inducing insects to habitat fragmentation; in some cases, gall abundance increases with habitat fragmentation (Wang et al 2005, Chust et al 2007), but in others, no relationship has been found (Julião et al 2004, Dunley 2009).…”

Pattern of attack of a galling insect reveals an unexpected preference-performance linkage on medium-sized resources

“…Interestingly, the mortality factors acting upon the other gall midge, S. macrocapillata, differed significantly from that acting upon A. microcapillata on the same host plant. On S. macrocapillata, an induced resistance mechanism, hypersensitive reaction (a bottom-up effect) accounted for more than 90% of the mortality, making few galls available to be found and killed by natural enemies (Fernandes 1990(Fernandes , 1998Fernandes et al 2000;Santos et al 2008). Pathogenic fungi accounted for no more than 3% as predicted by Fernandes & Price (1992) in xeric environments.…”

“…Previous studies on these two galling herbivores showed that S. macrocapillata has a strong preference for longer shoots (Cornelissen et al 1997;Fernandes 1998;Cornelissen & Fernandes 2001, Santos et al 2008 while A. microcapillata lacks a pattern of attack on shoots (Cornelissen et al 1997). In this 3-yr study we tested the preference-performance predictions of PVH that gall induction and survivorship of A. microcapillata are significantly greater on larger shoots and we analyzed the effects of top-down mortality factors on the performance of A. microcapillata.…”

“…Asphondylia microcapillata is univoltine and induces galls only when immature expanding or unfolded B. brevipes leaves are available. Asphondylia microcapillata is the second most abundant gall-former species on B. brevipes, whereas another leaf-galling midge, Schizomyia macrocapillata Maia (Diptera, Cecidomyiidae) is the dominant species (Cornelissen & Fernandes 1998, 2001Santos et al 2008).…”

“…Shoots were bagged, numbered and taken to the laboratory where their length, total number of leaves, number of galled leaves, number of galls, and gall diameter were recorded. Shoots were then divided into 3cm classes based on previous studies in this system (e.g., Fernandes 1998;Santos et al 2008). Mortality factors acting upon the gall were grouped into the following categories (Fernandes & Price 1992): parasitism, predation, pathogens and unidentified factors.…”