Phenotypic plasticity in size of ant-domatia

Bertrand Kokolo,Brama Ibrahim,Christiane Attéké Nkoulémbéné,Bertrand M’Batchi,Rumsais Blatrix

doi:10.1038/s41598-020-77995-y

Bertrand Kokolo, Brama Ibrahim + Show 3 more

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https://doi.org/10.1038/s41598-020-77995-y

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Abstract

Ant-plants produce hollow structures called domatia to host protecting ants. Although size variation in domatia is well documented between related species, intraspecific variation is little explored. The central African ant-plant Barteria dewevrei exibits strong variation in domatium size, giving the opportunity to explore the mechanism underlying variation in a mutualistic trait. We showed that domatium size in Barteria dewevrei varies between sites. We transplanted individual plants between two sites in Gabon where plants have different domatium sizes. Domatium size of transplanted plants changed, revealing that variation in this mutualistic trait is driven by phenotypic plasticity. The two sites differed in their environmental conditions: highland open savanna on sandy soil vs lowland closed tropical rain forest on sandy-loam soil. However, as stomatal density and δ13C of leaves did not differ between sites or between branches produced before and after transplantation, we have no cue on the role of abiotic stress (such as light intensity and water availability) in domatium size variation. As the obligate Tetraponera ant symbionts are too large to fit in the small domatia, variation of the mutualistic trait in response to environmental change through phenotypic plasticity may impact this specialized mutualism.

Highlights

Ant-plants produce hollow structures called domatia to host protecting ants
Our transplantation experiment demonstrated a predominant role of phenotypic plasticity in explaining the smaller diameter of domatia in Souba than in Bongoville: Souba plants grew larger domatia after transplantation to Bongoville and Bongoville plants grew smaller domatia after transplantation to Souba
In our study we did not detect any significant variation of stomatal density or of δ13C in leaves of B. dewevrei, either before and after transplantation, or between the two sites before transplantation

Summary

Introduction

Ant-plants produce hollow structures called domatia to host protecting ants. size variation in domatia is well documented between related species, intraspecific variation is little explored. Domatium size of transplanted plants changed, revealing that variation in this mutualistic trait is driven by phenotypic plasticity. As the obligate Tetraponera ant symbionts are too large to fit in the small domatia, variation of the mutualistic trait in response to environmental change through phenotypic plasticity may impact this specialized mutualism. Humboldtia brunonis is one of the rare ant-plant species in which both domatiabearing and domatia-free individuals o ccur[14] In this species, the proportion of domatia-bearing plants varies geographically and is higher in sites with stronger herbivore pressure[15]. Physophora, such a castration process leads to smaller domatia[16], suggesting a phenomenon of retaliation against cheating ants These studies show that physical damages to the plant can induce intra-specific variation in domatium state

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