DOI: 10.5061/dryad.4b6rv
title: Data from: Realized trophic niche driven by apparent competition: an example with marsupials

description: According to apparent competition theory, the co-occurrence of two species
 that share the same predators appears to affect each other's
 population growth and abundance. However, due to habitat loss and
 over-hunting, top predators are being made rare worldwide. Considering
 that apparent competitors share similar resources, we would expect the
 absence of top predators to reflect in changes on prey realized trophic
 niches. To test our hypothesis, we developed a model to predict the
 abundance ratio of apparent competitor species based on changes in their
 realized trophic niches. We tested our model against field data on the
 Neotropical marsupials Didelphis aurita and Metachirus nudicaudatus. Our
 results revealed that D. aurita and M. nudicaudatus are two species under
 apparent competition and their realized trophic niche and diet overlap
 change according to the presence of top predators. The model was able to
 predict the actual relative abundances of D. aurita and M. nudicaudatus in
 the three empirical studies analyzed. Our study presents quantitative
 support to the apparent competition theory; however, the model's
 applications to other groups still need to be verified. Additionally, our
 study shows that the lack of top predators has consequences on the
 realized trophic niche of their prey, and therefore, we reinforce that
 conservation plans need to focus on the effects of top predator loss on
 ecosystems.
description: Occurrence of food items
 found in Didelphis aurita and Metachirus nudicaudatus fecal
 samplesThe study was conducted
 in an Atlantic Rainforest area, in the Serra do Mar State Park (23°20’S
 and 44°50’W), southeast of Brazil (São Paulo State coast), at altitudes
 between 43 and 89m asl (Eisenlohr et al. 2013). A trapping session of four
 consecutive nights was conducted monthly from October 2013 to November
 2014. In order to capture the animals, we used one hundred Tomahawk traps
 (45 x 16 x 16 cm) on the ground, baited with banana, peanut butter, and
 bacon. The traps were 20 m apart from each other, forming a 3.4 ha grid
 (280m x 120m). Individuals captured were marked in each ear with one 1g
 monel ear tag (National Band and Tag Co.®), weighted, and identified by
 sex and age (Tyndale-Biscoe and MacKenzie 1976). Samples of scats were
 collected from adults only. Scats were collected from the bottom of the
 trap where the animal spent the night. The traps were placed on a platform
 of hardboard in order to isolate the scats from litter. Feces samples were
 dissolved in water and then filtered through a 1mm mesh screen sieve under
 running tap water. Then the material retained on the sieve was dried at
 ambient temperature. This undigested material was analyzed with a
 stereoscope and the taxonomic classification of the prey items found was
 done by specialists. After one year of trapping sessions (48 nights of
 trapping, 4800 trap-nights) we recorded 35 individuals (i.e., adults and
 juveniles) of *Didelphis aurita* and 19 individuals of *Metachirus
 nudicaudatus*. In order to avoid differences in the diet samplings of
 individuals, only adult feces were taken. Thirty-eight fecal samples were
 collected from 18 adults of *D. aurita*, and 32 fecal samples were
 collected from 15 adults of *M. nudicaudatus*. Their diet items are
 described in Table 01.Kuhnen et
 al.2017_Dryad.docx