Seed predation food web, nutrient availability, and impact on the seed germination of Senegalia tenuifolia (Fabaceae)

Abstract

Food web studies, which include qualitative and quantitative information about species interactions for all trophic levels in a specific community, are important tools to characterize the community structure, and to understand the role of species interaction in natural communities. With this aim, we collected fruits of Senegalia tenuifolia from a total of nine sites from three different areas in Minas Gerais, from June to August 2011. Fruits were collected and taken to the laboratory in special containers, to allow insect development and description. And then, we characterized the food web of insects associated with these seeds, and described interactions between these organisms and the host plant, and assessed the impact of insect attacks on seed germination with an experiment under controlled conditions. Additionally, we estimated the available NPK content and the Carbon:Nitrogen ratio in both fruits and seeds. In S. tenuifolia seeds, we have found 937 associated insects of 15 species structured in four trophic levels. We found two Bruchinae seed-feeders species: Merobruchus terani and Stator maculatopygus. We also have observed the seed-feeding hymenopteran species Allorhogas sp. 1 and Prodecatoma sp. 1, and hymenopteran parasitoids species such as Eupelmus sp.1, Lyrcus sp.1, Eurytoma sp.1, Horismenus sp.1, Chelonus sp.1, Aprostocetus sp.1, Eiphosoma sp.1 and an unidentified Pteromalinae. Considering quantitative food web metrics, our data have suggested low values of generality and high values of trophic vulnerability, besides others, which demonstrated how species interactions are specialized. The impact of seed-feeding insects on seeds was found severe and prevented their germination. Lastly, seeds contained higher NPK content than fruits. In conclusion, the seed predation food web supported by S. tenuifolia has depicted two different features: specialized species interactions, considering parasitoids and seed-feeding species, and, generalized species interactions, considering host-plant and seed-feeding species. Indeed, seeds are resources with high nutrient concentration supporting a rich and complex food web. Finally, S. tenuifolia seeds are directly impacted by seed-feeding insects, preventing them from germination, which could result in a negative effect on host-plant population. Rev. Biol. Trop. 63 (4): 1149-1159. Epub 2015 December 01.Key words: Bruchinae, seed-feeders, host-parasitoids, insect-plant interactions, quantitative food web.Food web studies, which focus mainly on trophic interactions, are important tools for characterizing community structure, understanding the role of species interaction and determining the influence of these interactions on observed patterns and dynamic properties of natural communities (Paine, 1992;Hall & Raffaelli, 1991). A complete food web study should include qualitative and quantitative information about species interactions for all trophic levels in a specific community (Lewis et al., 2002). However, the effort to explore a complete food web is dauntin...

Multitrophic interactions drive body size variations in seed‐feeding insects

“…Building upon data previously collected (Tuller et al ., ; Maia et al ., , ), we gathered information on seed biomass of S . tenuifolia and on the abundance of the three seed‐feeding species and their parasitoids in each fruit.…”

“…We established the interactions involving the seed‐feeding hymenoptera species ( A . vulgaris ) using information from previous works (Tuller et al ., ; Zaldívar‐Riverón et al ., 2018). After the emergence of insects we separated the seeds (per fruit) into paper bags, dried at 40 °C for 48 h, before being weighed using analytical digital weighing scales.…”

“…Indeed, parasitism should benefit the body size of individuals by decreasing fruit infestation. However, due to variation in biological characteristics of the three species, such as oviposition behaviour and strategy of resource exploitation (Johnson & Romero, ; Tuller et al ., ), we hypothesised they will respond differently to interactions within the food web.…”

Occurrence of Allorhogas sp. (Hymenoptera: Braconidae: Doryctinae) associated with galls on seeds of Inga vera (Fabaceae) in Brazil

“…For Eurytoma, we observe that inside the galls had traces of parasitism, but the remains of the host could not be directly associated to Allorhogas. However, specimens of Eurytoma has been pointed out as ectoparasitoides of Allorhogas in works such as those of Macêdo and Monteiro (1989), Penteado-Dias and Carvalho (2008) and Tuller et al (2015). All galls presented a similar aspect as those observed by Tuller et al (2015), of Allorhogas specimens feeding on S. tenuifolia seeds extremities and causing their deformation.…”

“…However, specimens of Eurytoma has been pointed out as ectoparasitoides of Allorhogas in works such as those of Macêdo and Monteiro (1989), Penteado-Dias and Carvalho (2008) and Tuller et al (2015). All galls presented a similar aspect as those observed by Tuller et al (2015), of Allorhogas specimens feeding on S. tenuifolia seeds extremities and causing their deformation. In our studies the galls had an ovoid aspect with yellow / brown coloration, located at the extremities of the seed.…”