Endozoochorous dispersal of forest seeds by carnivorous mammals in Sierra Fría, Aguascalientes, Mexico

Abstract

Some carnivorous mammals ingest fruit and disperse seeds of forest plant species capable of colonizing disturbed areas in ecosystems. The objective of the present study was to evaluate the dissemination of Arctostaphylos pungens and Juniperus deppeana seeds by the gray fox (Urocyon cinereoargenteus), coyote (Canis latrans), and other carnivores in the Protected Natural Area Sierra Fría, in Aguascalientes, Mexico. Scat collection was undertaken via transects using the direct search method, while the seasonal phenology of A. pungens and J. deppeana was evaluated by recording flower and fruit abundance on both the plant and the surrounding forest floor ground. Seed viability was assessed by optical densitometry via X‐ray and a germination test. It was found that the gray fox, coyote, ringtail (Bassariscus astutus), and bobcat (Lynx rufus) disseminated seeds of A. pungens (212 ± 48.9 seeds/scat) and J. deppeana (23.6 ± 4.9 seeds/scat), since a large proportion of the collected scat of these species contained seeds (28/30 = 93.33%, 12/43 = 27.9%, 6/12 = 50% and 7/25 = 28% respectively). The gray fox, coyote, ringtail, and bobcat presented an average of seed dispersion of both plant species of 185.4 ± 228.7, 4.0 ± 20.0, 12.1 ± 30.4, and 0.8 ± 1.5 per scat; the seed proportions in the gray fox, coyote, ringtail, and bobcat were 89.6/10.4%, 82.3/17.7%, 90.4/9.6%, and 38.1/61.9% for A. pungens and J. deppeana, respectively. The phenology indicated a finding related to the greater abundance of ripe fruit in autumn and winter (p < .01). This coincided with the greater abundance of seeds found in scats during these seasons. Endozoochory and diploendozoochory enhanced the viability and germination of the seeds (p > .05), except in those of A. pungens dispersed by coyote. These results suggest that carnivores, particularly the gray fox, the coyote, and the bobcat, play an important role in forest seed dissemination, and thus forest regeneration, by making both a quantitative and qualitative contribution to the dispersal of the two pioneer species under study.

Seed dispersal by carnivores in temperate and tropical dry forests

“…This is the case for A. pungens, the seeds of which were dispersed at a higher average abundance in the scats of gray fox, which corroborate previous findings for the same species (e.g., Rubalcava-Castillo et al, 2020). It is important to mention the role of the bobcat as a diploendozoochoric seed disperser (Hämäläinen et al, 2017), since J. deppeana seeds were found in its scats (Rubalcava-Castillo et al, 2020). In the tropical dry forest, the coati dispersed the highest abundance of seeds, with more than 8,600 seeds in only three scats.…”

“…It is important to mention the role of the bobcat as a diploendozoochoric seed disperser (Hämäläinen et al, 2017), since J. deppeana seeds were found in its scats, similar to the findings of Rubalcava-Castillo et al (2020). Our results therefore reinforce those of other studies that demonstrate the diploendozoochory in some of these carnivores (Kurek & Holeksa, 2015;Sarasola et al, 2016).…”

“…Within each site, we collected scats located by sight within transects (Nova, 2012) of following walking routes through the study area to locate scats by sight. Each transect is delimited by a central line of 2 km in length, with two parallel lines located at a distance of 20 m on either side of the central line (Rubalcava-Castillo et al, 2020). We have established a total of 30 transects in each area on trails for the movement of fauna, on dirt roads and among vegetation, that is, the scats were screened over a total area of 2 (temperate, tropical dry forest) × 30 (replicate transects) × 2,000 m (transect length) × 40 m (transect width/buffer).…”

“…The most common seed dispersal modes found in this type of ecosystem are endozoochory (dispersal through consumption by animals), anemochory (dispersal by wind), and epizoochory (dispersal by adhering to mobile living beings) (Willson et al, 1990). Likewise, the seeds found in this type of forest are generally thick testas to protect their embryos from changes in temperature during the seasons and the passage through the digestive tract of dispersing animals (Rubalcava-Castillo et al, 2020;Ruprecht et al, 2015). Tropical dry forests have canopy cover values greater than 30% and a great variety of flora and fauna (Olson et al, 2000).…”

Nutrición inicial en una reforestación de Juniperus deppeana Steud. y su capacidad de rebrote posincendio

“…es originaria de Estados Unidos de América y México (Adams et al, 2007). Su importancia ecológica se evidencia de diferentes formas; por ejemplo, sus conos (gálbulas) son alimento de fauna silvestre, como del conejo endémico de monte (Sylvilagus cunicularius Waterhouse) (Lezama-Delgado et al, 2016), el zorro gris (Urocyon cinereoargentus Schreber) y el coyote (Canis latrans Say) (Rubalcava-Castillo et al, 2020); mientras que su follaje es preferido por el venado bura (Odocoileus hemionus Rafinesque) (Schwartz et al, 1980). Juniperus deppeana se ha utilizado para restaurar zonas mineras, ya que es altamente resistente a la sequía y crece en suelos de baja fertilidad o con problemas por presencia de metales pesados, como los sustratos de desechos de minas (Osuna-Vallejo et al, 2017;Osuna-Vallejo et al, 2020).…”