INTRODUCTION
Resource utilization is a fundamental ecological process that mediates a
variety of interactions, from mutualisms to antagonisms (Bronstein
2015). Investigating resource use patterns provides insight into the
trophic niche species occupy and the functional roles they may play in
an ecosystem (Elton 2001, Chase and Leibold 2009, van Leeuwen et al.
2022). Furthermore, quantifying spatiotemporal patterns in resource use
can reveal the consistency of consumers in their dietary habits or
shifts toward preferred food items that are limited in time and/or space
(Abrahms et al. 2021). One spatiotemporally limited resource that is
closely tracked by animals are fleshy fruits (Koike et al. 2008,
Takahashi et al. 2008). In many ecosystems, as fleshy fruits become more
abundant through time, animals shift their diet to become more
frugivorous (Remis 1997, Gerardo Herrera M. et al. 2008, Robira et al.
2023).
Consequently, differences in a consumer’s strength of frugivory may
influence its effectiveness as a seed disperser (Marques Dracxler and
Kissling 2022, van Leeuwen et al. 2022), and since seed dispersal is a
fundamental aspect in the life cycle of plants (Traveset et al. 2014),
the strength of a consumer’s frugivory may have implications for plant
life histories. Thus, quantifying the importance of fruit in the diet of
an animal is a first step toward understanding its dispersal
effectiveness (sensu Schupp 1993, Schupp et al. 2010). Identifying which
fruit species are important in the consumer’s diet then opens the
question about the reciprocal importance of the consumer as its
disperser. While it has been demonstrated that plant dispersal syndromes
are unreliable in predicting ingestion and dispersal (i.e.,
endozoochorous dispersal) of seeds (Green et al. 2021), an approach to
quantify whether the functional role of an animal seed disperser changes
as it becomes more frugivorous is to gauge if seed dispersal for species
with the endozoochory syndrome (i.e., fleshy fruit) increases with
frugivory.
In this study, we investigate patterns of frugivory in a population of
hindgut fermenters, the gopher tortoise (Gopherus polyphemus ),
and aim to address whether its functional role as a seed disperser
changes as it becomes more frugivorous. Specifically, we aim to answer
the following questions: (1) Are there temporal patterns of frugivory in
this species? and (2) Which fleshy fruits drive frugivory? (3) Does the
dispersal of species with the endozoochory syndrome increase as
frugivory increases?
We hypothesize that after the seasonal precipitation begins, there will
be a time lag between peak precipitation and peak frugivory in the
gopher tortoise. Considering the phenology of many fleshy fruits in
south Florida, coinciding with seasonal rains (Lodge 2017, Flora of
North America Editorial Committee, eds. 1993+ 2023), as well as the
two-to-three week gut retention time of the gopher tortoise (Bjorndal
1987), we anticipate that frugivory will increase steadily in throughout
the summer with its peak in late summer/early fall. We expect that
ultimately, the tortoises will disperse more fleshy-fruit species as
they become more frugivorous, given the extremely broad and
opportunistically frugivorous diet of this species (Ashton and Ashton
2008). This would demonstrate a shift along the mutualism-antagonism
continuum by ecologically functioning as a frugivore by dispersing more
species with the endozoochory syndrome as fruit consumption increases
(sensu van Leeuwen et al. 2022).