The role of frugivorous birds in fruit removal and seed germination of the invasive alien Cotoneaster franchetii in central Argentina

Abstract

Many invasive plant species have fleshy fruits that are eaten by native frugivorous birds which disperse their seeds and may facilitate their germination, playing an important role in plant invasion success. The fleshy-fruited shrub Cotoneaster franchetii (Rosaceae) is an important invasive alien in the mountainous regions of central Argentina. To determine the role of avian frugivorous in fruit removal of this species, we conducted a frugivore exclusion experiment including bagged and unbagged branches in 75 plants of C. franchetii. At the end of the dispersal period, we compared the percentage of missing fruits (removed by birds + naturally dropped) in unbagged branches with the percentage of naturally dropped fruits in bagged branches. To assess whether any mechanism acting on seeds during their passage through bird guts (de-inhibition by pulp removal and/or seed scarification) affects seed germination of this species, we compared percentage and speed of germination among seeds obtained from faeces of the native frugivorous Turdus chiguanco, from manually de-pulped fruits, and from intact fruits. The percentage of missing fruits per shrub in unbagged branches was significantly higher than the percentage of naturally dropped fruits in bagged branches, suggesting that frugivorous birds play an important role in fruit removal of C. franchetii in the study area. Seeds from bird faeces and from manually de-pulped fruits germinated in higher percentage and faster than seeds from intact fruits. Germination percentage and speed of seeds from manually de-pulped fruits were significantly higher than those of gut-passed seeds. These results indicate that T. chiguanco increases and accelerates seed germination of C. franchetii through pulp removal, but not through seed scarification. Overall, our findings indicate that native frugivorous birds facilitate the dispersal and germination success of C. franchetii, likely playing an important role in its invasion throughout the mountainous region of central Argentina.

Seed Dispersal by Frugivores and Germination Success of the Invasive Alien Shrub Pyracantha Angustifolia in the Eastern Free State Province, South Africa

“…From our observations and remote camera-trap data, results support that birds are important potential seed dispersers (Díaz Vélez et al 2018, Vergara-Tabares et al 2018). This showed that bird species are effective seed dispersers of P. angustifolia.…”

Comparing germination metrics of Opuntia ficus-indica and O. robusta between two sets of bird species (Pied Crows and two smaller species)

“…Seed abrasions and scarification by birds increase seed coat permeability and thus, quick imbibition (Figueroa and Castro, 2002); this may also explain the surprising observation of both the highest and accelerated seed germination of O. robusta after treatment by the smaller birds. When matched with conducive conditions, accelerated seed germination is important for reducing competition with siblings for resources, avoiding secondary predators (Diaz-Velez et al, 2018), and promoting plant species colonisation and invasion success. This finding points to different bird species having different impacts on seeds of similar plant species, as demonstrated in seeds of Acacia cyclops consumed by different dove species (Mokotjomela et al, 2015).…”

Bacterial detoxification of plant defence secondary metabolites mediates the interaction between a shrub and frugivorous birds

“…Endozoochory is a common seed dispersal strategy involving the production of fruits to attract frugivores that feed on the fruits and disperse seeds in their droppings 3 . Beside dispersal, endozoochory enhances germination by separating seeds from the pulp (often containing germination inhibitors), fertilizing the ground with fecal material, and scarification of the seed coat 4 – 7 . Interaction between plants and frugivores is assumed mutualistic, with the consumer benefiting from nutrients in fruits and the plant benefiting from seed dispersal 8 , 9 .…”