Seed dispersal effectiveness of shrubs by goat

Non-native Mammals Are the Main Seed Dispersers of the Ancient Mediterranean Palm Chamaerops humilis L. in the Balearic Islands: Rescuers of a Lost Seed Dispersal Service?

“…Our study demonstrates that both goats and pine martens are effective seed dispersers of C. humilis in Mallorca, and we thus hypothesize that these introduced frugivores, especially the goat, could be replacing the function probably carried out by the extinct M. balearicus in the past, acquiring the role of seed dispersal "rescuers". This role has already been suggested for the goat in other systems (e.g., Mancilla-Leytón et al, 2015;Cares et al, 2018). So, despite the fitness costs imposed by both introduced mammals, they could be providing an indispensable service to this ancient palm by dispersing it on island systems, where native dispersers are extinct and the alternatives are very limited.…”

“…Regarding seedling growth, seeds spit out by goats showed the lowest values of seedling dry weight, whereas pine marten-ingested seeds the highest ones. This could suggest that treatment in the mouth of goats could be more aggressive than treatment in the gut of pine martens, since chewing process is very intensive in ruminant species (Mancilla-Leytón et al, 2015). Nonetheless, the seedling dry weight of seeds regurgitated by goats was rather similar to that of pine marten-ingested seeds (Figures 7A,B), thus further research is required to go in depth in these results.…”

“…In relation to seed coat scarification, seed treatment in goat-stomach during rumination (i.e., digestive contractions and fermentation) could be accelerating seed germination as seed regurgitated by goats showed the highest emergence speed. However, this treatment is sometimes too harsh for seed viability, leading to the damage of seed embryos (i.e., seed predation) (e.g., Mancilla-Leytón et al, 2015;Jara-Guerrero et al, 2018) and, consequently, decreasing the final emergence success. Pine marten-ingested seeds showed the highest emergence success (after the manuallydepulped control seeds); however, this disperser does not seem to be exerting any effect on emergence speed through seed scarification.…”

“…Several authors have suggested the pivotal role of this species as shaper of vegetation dynamics, acting as a keystone species in these insular ecosystems during the Pleistocene and Holocene (Palmer et al, 1999;Winkler et al, 2013b;Welker et al, 2014). Although no seeds have been found so far in any coprolites (Rivera et al, 2014;Welker et al, 2014), it is not discarded that M. balearicus could also feed on fruits (as many goats do today, e.g., Mancilla-Leytón et al, 2015;Delibes et al, 2017a) and discard seeds intact, thus acting also as a legitimate disperser. On the other hand, even though the origin of C. humilis in the Balearic Islands remains uncertain (Carrión, 2012), its old presence in the eastern coast of the Iberian Peninsula (Arroyo et al, 2004;Pérez-Obiol et al, 2010) would make more plausible the hypothesis of a Balearic existence before the recent human arrival.…”