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

Abstract

ABSTRACT. Pattern of attack of a galling insect reveals an unexpected preference-performance linkage on medium-sized resources. The Plant Vigor Hypothesis (PVH) predicts oviposition preference and higher offspring performance on longer and fastgrowing shoots, and although several studies have tested its predictions, long-term studies concerning the patterns of host selection by galling species are still lacking. The PVH was tested in this study using Bauhinia brevipes (Fabaceae) as the host of a leaf gall midge, Asphondylia microcapillata (Diptera, Cecidomyiidae) during three consecutive years. Shoots were collected from the same 80 plants between 2001 and 2003 and shoot length, number of healthy and galled leaves, gall number, and mortality factors were recorded. Nearly 600 galls were found on the 5,800 shoots collected. Medium-sized shoots supported from 46 to 70% of all galls, with greater gall survival rate in 2002 and 2003. A decrease in parasitism rate coupled with an increase in gall predation lead to a constant similar gall survivorship rate in all years (x = 22.7%). Although gall abundance varied among years (122 in 2001, 114 in 2002 and 359 in 2003) preference for longer shoots was not observed because the percentage of galled shoots and galled leaves were higher on medium shoot length classes in all years. The observed distribution of gall abundance and galled shoots were always greater than the expected distribution on medium shoot length classes. These findings do not support the PVH, and show that A. microcapillata can maximize the female preference and larval performance on medium-sized shoots of B. brevipes.KEYWORDS. Host selection; insect galls; mortality factors; Plant Vigor Hypothesis; top-down effect.RESUMO. Padrão de ataque de um inseto galhador revela uma inesperada ligação entre preferência e performance sobre recursos de tamanho médio. A Hipótese do Vigor de Plantas (HVP) prevê uma oviposição preferencial e alta performance da prole em ramos longos e de crescimento rápido da planta hospedeira. Embora diversos estudos tenham testado suas predições, estudos de longa duração focados no padrão de seleção de planta hospedeira por insetos galhadores ainda são escassos. A HVP foi testada neste estudo usando Bauhinia brevipes (Fabaceae) como planta hospedeira de uma galha foliar induzida por Asphondylia microcapillata (Diptera: Cecidomyiidae) por três anos consecutivos. Ramos foram coletados das mesmas 80 plantas entre 2001 e 2003 e o tamanho do ramo, número de ramos galhados e sadios, número de galhas e fatores de mortalidade foram registrados. Aproximadamente 600 galhas de A. microcapillata foram coletadas em 5.800 ramos de B. brevipes. Ramos médios suportaram entre 46% e 70% do total de galhas, e a taxa de sobrevivência das galhas foi maior em 2002 e 2003. Uma diminuição da taxa de parasitismo associada com um aumento da taxa de predação de galhas resultou em uma sobrevivência similar em todos os anos (x = 22,7%). A abundância de galhas variou entre os anos (122 em 2001, 114 em 2002 e 359 e...

Biology of Asphondyliini (Diptera: Cecidomyiidae)

“…Their results did not support the hypothesis because A. microcapillata maximized the female preference and larval performance on medium‐sized shoots of B. brevipes (Santos et al . ).…”

“…Thompson 1988), particularly in immobile insects such as gall inducers (Tokuda et al 2001). Using Asphondylia microcapillata Maia, which induces leaf galls on Bauhinia brevipes (Fabaceae), Santos et al (2010) tested the plant vigor hypothesis (Price 1991) predicting that insect herbivores prefer more vigorous parts of plants for oviposition and that offspring performance is greater on these parts. Their results did not support the hypothesis because A. microcapillata maximized the female preference and larval performance on medium-sized shoots of B. brevipes (Santos et al 2010).…”