Filling gaps in the seed dispersal effectiveness model forProsopis flexuosa: quality of seed treatment in the digestive tract of native animals

Abstract

For endozoochorous species, the quality component of seed dispersal effectiveness depends in part on the treatment seeds receive in the animal's gut. Covering a variety of taxa, diet, digestion system and body size of Prosopis flexuosa seed dispersers, we analysed differences among species in (1) mean retention time of ingested seeds, (2) recovery of viable seeds, (3) seed germination in comparison with seeds collected from trees and (4) germination of seeds after two different periods of retention in the gut. Feeding experiments were conducted with captive individuals of Dolichotis patagonum, Lycalopex gymnocercus, Rhea americana, Chelonoidis chilensis and Lama guanicoe. On the first day, we provided them with fruits containing controlled amounts of seed, and on the subsequent days, we collected faeces in order to recover seeds. We performed germination and viability tests on seeds coming from faeces and collected from trees. The results showed differences among species in the mean retention time of seeds. Chelonoidis chilensis had the longest mean retention time, but its effect on seed recovery and germination was similar to that of the other species, except for L. guanicoe, which showed the lowest seed recovery. When scarification and promotion of seed germination were considered, herbivorous mammals and tortoises (L. guanicoe, D. patagonum and C. chilensis) were the ones increasing germinability, whereas R. americana and L. gymnocercus did not significantly increase final seed germination percentage, which was similar to that for seeds collected from trees. P. flexuosa seeds receive a variety of treatments from endozoochorous dispersers, which might result in an overall fitness benefit for a plant living in unpredictable environments.

Experimental assessment of endozoochorous dispersal of Prosopis flexuosa seeds by domestic ungulates

“…For many plant species with hard‐coated seeds, the time that seeds remain in a disperser's gastrointestinal tract can have negative, positive or even no consequences for the germination success of gut‐passed seeds (Traveset et al, 2007), depending on other factors such as digestive capacity of dispersers (Colucci et al, 1990) or intra‐ and interspecific seed coat variations (Smýkal et al, 2014). In line with these statements and with our results, Campos et al (2020) found no differences in germination of P . flexuosa seeds after their passage through the wild herbivores Chelonoidis chilensis (Argentine tortoise) and Dolichotis patagonum (Patagonian hare), despite the marked difference in seed RT between both animal species.…”

“…The role of many wild animals as seed predators or dispersers of P . flexuosa seed is well known (Campos & Ojeda, 1997; Campos et al, 2007, 2008, 2017, 2018, 2020; Campos & Velez, 2015; Velez et al, 2016, 2018), as are the quantitative aspects related to number of seeds dispersed under different land uses (Bessega et al, 2017; Campos et al, 2016; Miguel et al, 2017, 2018a, 2018b; Tabeni et al, 2017). For domestic animals like cattle, previous studies analysed the number and germinability of P .…”

“…The role of many wild animals as seed predators or dispersers of P. flexuosa seed is well known (Campos & Ojeda, 1997;Campos et al, 2007Campos et al, , 2008Campos et al, , 2017Campos et al, , 2018Campos et al, , 2020Campos & Velez, 2015;Velez et al, 2016Velez et al, , 2018, as are the quantitative aspects related to number of seeds dispersed under different land uses (Bessega et al, 2017;Campos et al, 2016;Miguel et al, 2017Miguel et al, , 2018aMiguel et al, , 2018bTabeni et al, 2017). For domestic animals like cattle, previous studies analysed the number and germinability of P. flexuosa seeds recovered from faeces collected in the field (Campos & Ojeda, 1997) and established the quality of sites where faeces and seeds are deposited (Campos et al, 2011).…”

Addressing Cultural Challenges Through Environmental Education: An Educational Approach for the Preservation of Fauna and the São Francisco River Water Basin

“…This classic example can be cited as one of the milestones that awakened the need for knowledge about coevolution between species for conservation. Some plant species require the process of chemical scarification in the digestive tract of animals to break dormancy or to increase the rate and quality of germination (CAMPOS et al, 2020;KLEYHEEG;CLAESSENS;SOONS, 2018). Therefore, these species have an even greater dependence on dispersing animals.…”

Conflicting selection pressures on seed size and germination caused by carnivorous seed dispersers

“…Gut treatment destroys or removes numerous seeds, both during consumption and during passage through the digestive tract (Campos et al 2020). This process may influence the time of germination and germination success because of the removal of fruit skin and pulp, mechanical and chemical abrasion during consumption and transit through the guts of seed dispersers, and facilitation effects of the fecal material surrounding the seeds (Torres et al 2020).…”