Frugivory and seed dispersal in the endemic cactus Eulychnia acida: extending the anachronism hypothesis to the Chilean Mediterranean ecosystem

Abstract

Background: Eulychnia acida is an endemic Chilean cactus species whose fruits show several traits that, taken as a whole, are compatible with a seed dispersal syndrome by large herbivore vertebrates. Since only a few large native mammals exist in Chile at present, cactus fruit consumption and seed dispersal may be coopted by introduced mammals as predicted by Janzen and Martin's (1982) hypothesis for tropical ecosystems. Findings: We describe the current frugivore species of E. acida in a protected semiarid-Mediterranean ecosystem using field measurements and feeding experiments. In addition, to examine a potential role as seed dispersers of the cactus species, we offered fruits and performed germination tests on seeds defecated by Lama guanicoe and the introduced goat Capra a. hircus under captivity conditions. Our data indicate that while fruits of E. acida are pecked by the Chilean tinamou, Nothoprocta perdicaria, and the Chilean mockingbird, Mimus thenca, and eaten by the brush-tailed rodent, Octodon degus, none of these species could be considered a legitimate seed disperser. Unlike L. guanicoe, the goat C. a. hircus did not reduce seed germination, having a neutral effect. Conclusions: Results from this study indicate that introduced C. a. hircus was the only species showing a potential role in the seed dispersal process of E. acida. In the absence of native frugivore species, goats might play an important role in population recruitment of the endemic cactus. These results extend Janzen and Martin's (1982) anachronism hypothesis to the Chilean Mediterranean ecosystem.

Intertwined effects of defaunation, increased tree mortality and density compensation on seed dispersal

“…For instance, when fox losses were completely compensated with badgers, seed dispersal into Mediterranean scrubland increased to a level that even surpassed the baseline scenario. Similar compensation has been documented not only among native seed dispersers (Cordeiro andHowe 2003, Zhou et al 2013) but also by introduced and domestic species (García et al 2014, Cares et al 2018, Muñoz-Gallego et al 2019. However, such apparent compensation could be less complete if disperser species differ in subtle but key aspects of the seed dispersal process (e.g.…”

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.…”

“…Given that humans are largely determining the number of goats on Mallorca (Mayol et al, 2017), they are probably influencing the "relative seed dispersal effectiveness", not only for C. humilis, but also for many other systems where livestock "rescues" the seed dispersal service of anachronistic plant species (Janzen and Martin, 1982;Cares et al, 2018). Goats have been described to expel the ingested seeds while defecating (e.g., Mancilla-Leytón et al, 2011) or ruminating (e.g., Delibes et al, 2017a); however, we found no goat feces with C. humilis seeds in our study sites.…”

“…For instance, in the Balearic Islands, introduced pine martens (Martes martes) replace, at least partially, the native lizards which presumably used to be the only legitimate dispersers of the native shrub Cneorum tricoccon until recently (Traveset, 1995;Celedón-Neghme et al, 2013). Therefore, contemporary frugivore assemblages, even though in a suboptimal way (Guimarães et al, 2008), can act as "rescuers" of the seed dispersal service of anachronistic species, mitigating the effects of previous animal extinctions, and avoiding the vanishing of ecological interactions (Zamora, 2000;Valiente-Banuet et al, 2015;Rumeu et al, 2017;Cares et al, 2018).…”

Quaternary diversification of a columnar cactus in the driest place on earth

“…The Peruvian E. ritteri is clearly retrieved as an isolated, early lineage of Eulychnia and cannot go back to recent long‐distance dispersal. However, an early‐dispersal event cannot be ruled out, in particular considering the large, juicy fruits of some Eulychnia taxa, which may in the past have been dispersed by now extinct herbivore mammals (Cares et al, 2018). The guanaco ( Lama guanicoe ), for example, once widespread from northern Peru to Tierra del Fuego but now distributed in less than 30% of its range at the time of arrival of Europeans to South America (Marin et al, 2013 and references therein), may have acted as an important disperser of Eulychnia seeds.…”