The relationship between modularity and snake lifestyle
The network also presented a modular structure, in which the consumption
of different resources divided the network into six different food
modules (Table 1 and Supplementary material Appendix 1 Table A3). We
expected that if the snake lifestyle was related to the formation of
food modules, the distribution of lifestyles in the different modules
would not be random. In fact, modules were associated with particular
lifestyles, as indicated by significant or marginally significant
probability values present in all modules but module 3 (Table 2). Module
3, was composed of species with the greatest variety in diet and
lifestyle, such as boid snakes. Modules with more specific combinations
of lifestyle and diet showed all significant or marginally significant
probability values (Figure 4). Moreover, the formation of groupings
based on diet and lifestyle occurred by species that specialise in the
consumption of certain food resources, probably associated with their
lifestyle. For example, the smallest module (number 5) was formed by
only two arboreal species of the genus Dipsas that feed
exclusively on mollusks; another module grouped species of terrestrial
habits, such as Drepanoides anomalus, Drymoluber dichrous , andMastigodryas boddaerti , which feed on squamate eggs, whereas
another module grouped fossorial species, such as Atractus spp.
that are specialists in preying upon earthworms. On the other hand, the
remaining modules grouped species with varied lifestyles and generalist
diets.
As a consequence of the association between lifestyles and modular
structure, modules often show dissimilar combinations of lifestyles.
Dissimilarity values ranged from 0.33 to 1 (Table 2). The most
dissimular module (Module 0) was composed exclusively of snakes with the
fossorial lifestyle, such as the Atractus species, specialists in
the consumption of earthworms. The most similar modules were modules 1
and 3, which as well as module 2 have the largest variety of lifestyles
and food resources consumed by the snakes (Supplementary material
Appendix 1 Table A3).