Temperate Snake Community in South America: Is Diet Determined by Phylogeny or Ecology?

Abstract

Communities are complex and dynamic systems that change with time. The first attempts to explain how they were structured involve contemporary phenomena like ecological interactions between species (e.g., competition and predation) and led to the competition-predation hypothesis. Recently, the deep history hypothesis has emerged, which suggests that profound differences in the evolutionary history of organisms resulted in a number of ecological features that remain largely on species that are part of existing communities. Nevertheless, both phylogenetic structure and ecological interactions can act together to determine the structure of a community. Because diet is one of the main niche axes, in this study we evaluated, for the first time, the impact of ecological and phylogenetic factors on the diet of Neotropical snakes from the subtropical-temperate region of South America. Additionally, we studied their relationship with morphological and environmental aspects to understand the natural history and ecology of this community. A canonical phylogenetical ordination analysis showed that phylogeny explained most of the variation in diet, whereas ecological characters explained very little of this variation. Furthermore, some snakes that shared the habitat showed some degree of diet convergence, in accordance with the competition-predation hypothesis, although phylogeny remained the major determinant in structuring this community. The clade with the greatest variability was the subfamily Dipsadinae, whose members had a very different type of diet, based on soft-bodied invertebrates. Our results are consistent with the deep history hypothesis, and we suggest that the community under study has a deep phylogenetic effect that explains most of the variation in the diet.

Ecological and phylogenetic determinants of life‐history patterns among ten loricariid species

“…In this way, our study supports the hypothesis that phylogenetic history is more important in the determination of life‐history strategies than key ecological factors. This is consistent with studies carried out in fish (Lujan et al ., ; Roa‐Fuentes et al ., ; Vila‐Gispert et al ., ) and other vertebrate groups (Bellini et al ., , ; Cadle & Greene, ; França et al ., ; Kraft et al ., ; Vitt & Pianka, ; Vitt et al ., ; Webb et al ., ), that sustain a strong signature of phylogenetic history on the observed phenotypic patterns of organisms.…”

Species distribution models and empirical test: Comparing predictions with well‐understood geographical distribution of Bothrops alternatus in Argentina

“…We used several discrimination indices derived from the confusion matrix, namely sensitivity, specificity (Fielding & Bell, ), and the under‐prediction and overprediction rates (UPR and OPR, respectively). The latter rates refer to the proportion of observed presences in the predicted absence area and the proportion of observed/assumed absences in the predicted presence area, respectively (Barbosa et al., ). We obtained the ROC curve, that is, AUC index, which represents the probability that the model correctly predicted the observed presences and absences and varies from 0 to 1, 1 being perfect discrimination and 0.5 to 0 implying a discrimination worse than random (Araújo et al., ; Elith et al., ).…”

“…As a model for this study, we selected B. alternatus, a poisonous snake species with public health importance. Thorough and continuous efforts have been made for decades to perform unbiased samplings throughout its distribution area in Argentina (e.g., Arzamendia & Giraudo, 2009;Bellini, Giraudo, Arzamendia, & Etchepare, 2015;Giraudo, 2001;Giraudo & Arzamendia, 2014;Giraudo et al, 2008;Nori, Carrasco, & Leynaud, 2013). Besides, B. alternatus: (a) presents (Bellini et al, 2015;Giraudo, 2012;Giraudo et al, 2008;Scrocchi, Moreta, & Kretzschmar, 2006); (e) presents peculiarities in its distribution which constitute real challenges in modeling; for example, it has not been found in humid forests to the northeast of its distribution (Giraudo, 2001) and two disjunctive and isolated populations occur in coastal areas and the Pampean hills in Buenos Aires province (South distribution).…”

“…We defined the ED of B. alternatus (Figure 1b) mainly based on both collected data with intensive spatial and temporal sample coverage and our knowledge (Bellini et al, 2015;Giraudo, 2001;Giraudo & Arzamendia, 2014;Giraudo et al, 2008) as well as by delimiting areas inhabited and not inhabited by the species. We included some areas without data in the inhabited territory of B. alternatus because we know that, they can be occupied by the species (Hortal et al, 2015).…”

“…Nonetheless, studies that provide techniques to improve SDMs predictions in relation to expert maps are needed, as in Merow, Wilson, and Jetz () where they sought to determine if expert maps can help reduce biased extrapolation in SDMs prediction. In a similar way, most of the accuracy measures from the confusion matrix (Barbosa, Real, Muñoz, & Brown, ; Fielding & Bell, ) and indices (e.g., area under the curve—AUC‐ROC; Akaike information criterion, see Guisan & Thuiller, ) used for this purpose does not provide a comparison of the model with the empirical distribution (ED) of the species (Loiselle et al., ). These last authors pointed out the importance of validating models with independent data, and warned that failure to include independent model validation, especially in cases where training points are limited, may potentially lead to serious errors in conservation decision‐making.…”