Climate drivers and novel insect associations shape pre-dispersal predation in Hancornia speciosa

Abstract

Pre-dispersal seed predation reduces the numbers of viable seeds produced by plants and their populations. Hancornia speciosa Gomes (Apocynaceae), popularly known as mangabeira, is native to Brazil and widely distributed in savannas, open sandy landscapes, and coastal restinga vegetation formations. Its edible fruits generate income for thousands of families. We recorded attacks by Asphondylia hancorniae , a specialist endoparasitic gall midge, on immature H. speciosa fruits on trees in the Chapada Diamantina mountains and in the coastal zone, Northeastern Brazil, for 24 months. We also investigated the influence of environmental variables on this process. Asphondylia hancorniae attacks cause the withering of immature fruits before seed formation and dispersal. We suggest the use of the Fournier Intensity Index as a quantitative tool to assess the intensity of seed predation and plant disease occurrence in a standardized and comparable manner. Predation intensity reached 47.22% in coastal zone and 35.65% in the inland Chapada Diamantina mountains populations and showed positive correlations with temperature and photoperiod. This approach is especially important for conservation strategies aiming to understand the impact of fruit losses in H. speciosa caused by the gall midge A. hancorniae and how contrasting climatic factors modulate those plant-insect interactions. The damage caused by A. hancorniae on fruits allowed secondary attacks by Hypothenemus obscurus , an association not previously reported as involving a Cecidomyiidae fly and a Scolytinae bark beetle. Our results highlighted the greater habitat fragmentation along the coast appears to amplify negative environmental impacts on the fruiting of H. speciosa .

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