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| Two Tegus, Salvator merianae and S. rufescens JCM |
When two closely related species live side by side it is
generally assumed that they have some way of dividing the resources so that
they are not in direct competition with each other. The large terrestrial
lizards the Black and White Tegu, Tupinambis (=Salavator) merianae, and the Red Tegu, T. (=Salvator) rufescens provide
a model system to examine the role of life history factors in trophic niche
divergence because they share several bioecological traits. They have similar
body sizes and share external morphology and generalized foraging habits.
Phylogenetic studies suggest the two species are sisters. In Argentina,
they occur in parallel allopatric zones from approximately 10–40°S. Tupinambis rufescens occurs further west than T. merianae. However,
they both occupy a large contact zone. These species differ in habitat
requirements in allopatric areas, but in the contact zone the species use the
same landscape and habitat resources. Moreover, T. merianae and T.
rufescens select landscapes with a large proportion of forest and shrubs
than the mean landscape availability in contact zones.
In a new paper López Juri et al. (2015) evaluate the trophic niche segregation between merianae and rufescens in a contact zone to understand how life history traits (body
size, sexual body size dimorphism, sexual maturity and reproductive activity)
might influence the feeding ecology of these lizards and lead to trophic niche
differentiation between species. Their results suggest that, although both species are omnivorous,
they exhibit a tendency to specialize, with arthropods being dominant in the
diet of merianae and fruits and seeds being dominate in the diet of rufescens. The
two species have broad trophic overlap, however, while both species share
several prey items, the relative importance of each item varied between them.
These differences may be important for niche segregation, mainly because the prey
items considered fundamental were different between species, suggesting a
differential use of certain resources. T. merianae is often associated with
anthropogenic areas with cultural vegetation and remnant shrub lands where few
vertebrate species remain which may explain the low diversity of food items and
the dominance of arthropods and some rodents in the diet composition. Their results
indicate that body size, sexual maturity and reproductive activity are relevant
factors influencing the diet of these species. Life history traits of these two
species of Tupinambis are important because they shape diet composition,
contributing to interspecific segregation of the trophic niche and, therefore,
allowing species coexistence.
Citation
López Juri G, Naretto S, Mateos AC,
Chiaraviglio M, Cardozo G. 2015. Influence of life history traits on trophic niche
segregation between two similar sympatric Tupinambis
lizards. South American
Journal of Herpetology, 10(2): 132–142.