Phenotypic plasticity and similarity among gall morphotypes on a superhost, Baccharis reticularia (Asteraceae)

Abstract

Understanding factors that modulate plant development is still a challenging task in plant biology. Although research has highlighted the role of abiotic and biotic factors in determining final plant structure, we know little of how these factors combine to produce specific developmental patterns. Here, we studied patterns of cell and tissue organisation in galled and non-galled organs of Baccharis reticularia, a Neotropical shrub that hosts over ten species of galling insects. We employed qualitative and quantitative approaches to understand patterns of growth and differentiation in its four most abundant gall morphotypes. We compared two leaf galls induced by sap-sucking Hemiptera and stem galls induced by a Lepidopteran and a Dipteran, Cecidomyiidae. The hypotheses tested were: (i) the more complex the galls, the more distinct they are from their non-galled host; (ii) galls induced on less plastic host organs, e.g. stems, develop under more morphogenetic constraints and, therefore, should be more similar among themselves than galls induced on more plastic organs. We also evaluated the plant sex preference of gall-inducing insects for oviposition. Simple galls were qualitative and quantitatively more similar to non-galled organs than complex galls, thereby supporting the first hypothesis. Unexpectedly, stem galls had more similarities between them than to their host organ, hence only partially supporting the second hypothesis. Similarity among stem galls may be caused by the restrictive pattern of host stems. The opposite trend was observed for host leaves, which generate either similar or distinct gall morphotypes due to their higher phenotypic plasticity. The Relative Distance of Plasticity Index for non-galled stems and stem galls ranged from 0.02 to 0.42. Our results strongly suggest that both tissue plasticity and gall inducer identity interact to determine plant developmental patterns, and therefore, final gall structure.

Trade‐off between fecundity and survival generates stabilizing selection on gall size

“…Two related issues not considered in the current experimental design are the role of phenotypic plasticity and the genetic basis of gall size (Formiga, Silveira, Fernandes, & Isaias, 2015; László & Tóthmérész, 2013; Weis & Abrahamson, 1986; Weis et al., 1992). It is possible that plasticity plays a role in the process of gall formation, which is an interaction between the insect genome, the plant genome, and the environment (Weis & Abrahamson, 1986; Weis et al., 1992).…”

Questioning the environmental stress hypothesis for gall diversity of restinga vegetation on dunes

“…The stem galls have a less variety of shapes, which demonstrated the less plastic potential of this host organ (Formiga et al, 2014) to alter its morphogenesis under external stimuli, such as that of the galling herbivores. The fusiform morphotype develops along the longest axis of the host stems with the increment in volume attributed to cell hypertrophy and tissue hyperplasia, as described by Ferreira and Isaias (2013) for stem galls on Marcetia taxifolia (Melastomataceae).…”

“…As Formiga, Silveira, Fernandes and Isaias (2014) proposed, we use the widely accepted concept of gall morphotypes, for it has been widely used in inventories of gall diversity and richness in the Neotropics. Also, each pair of host plant-gall inducer is referred to as a morphospecies, similar to PortugalSantana and .…”

Structural and Nutritional Peculiarities Related to Lifespan Differences on Four Lopesia Induced Bivalve-Shaped Galls on the Single Super-Host Mimosa gemmulata

“…Accordingly, the longer the galling insect stay inside the gall, the higher the gall demand is (Carneiro et al, 2017), therefore, the long-life cycle of the galling insect may determine more complex gall structural profiles (Gonçalves et al, 2005). Such presumption may be analyzed in the nutritional perspective, and the accumulation of energetic resources in gall storage tissues can be higher, the longer the gall lifespan is, which may be elegantly evaluated in superhost plants with several associated galling-insects (Formiga et al, 2014;Amorim et al, 2017;Bragança et al, 2020a;Costa et al, submitted).…”