Creationism in Crisis - How Snakes Evolved To Meet The Demands Of Their Habitat And Food Sources

There are more than 800 species of dipsadine snakes, ranging from less than 12 inches to more than 9 feet in length.

Photos: Gregory G. Pandelis.

Dipsas catesbyi, a snail-eating species

Snake skulls show how species adapt to prey - News Center - The University of Texas at Arlington

The ability to catch and consume prey species is a key aspect of evolutionary biology in carnivorous species, for obvious reasons, and so is a major source of divergence and radiation of species as each species become more and more specialised at catching different prey species.

An example of this was published recently in the journal BMC Ecology and Evolution in which three researcher, led by Gregory G. Pandelis of the Amphibian and Reptile Diversity Research Center, Department of Biology, University of Texas at Arlington, Arlington, Texas, USA with two colleagues from the Department of Ecology and Evolutionary Biology, University of Michigan, Ann Arbor, Michigan, USA, showed a correlation between prey species and skull morphology in dipsadine snakes.

Tell me all about dipsadine snakes. As of my last knowledge update in January 2022, the term "dipsadine" refers to a subfamily of snakes known as Dipsadinae. Dipsadinae is a subfamily within the larger family Colubridae, which includes a diverse group of non-venomous snakes found worldwide. Keep in mind that new scientific discoveries and taxonomic changes may have occurred since then. Here are some general characteristics and information about Dipsadine snakes:

1. Distribution: Dipsadine snakes are primarily found in the Americas, with a focus on Central and South America. They inhabit a variety of ecosystems, ranging from rainforests to dry savannas.
2. Diet: Dipsadine snakes are typically carnivorous, feeding on a variety of prey such as insects, small mammals, amphibians, and other reptiles. Their diet may vary depending on the species and its habitat.
3. Venom: Most dipsadine snakes are non-venomous. They rely on constriction or other methods to subdue their prey. However, it's essential to note that not all species within the subfamily lack venom, and there may be exceptions.
4. Reproduction: Dipsadine snakes generally reproduce by laying eggs. However, some species may give birth to live young through a process called viviparity. The reproductive strategies can vary among different species within the subfamily.
5. Behavior: Dipsadine snakes exhibit a range of behaviors, from arboreal species that are adapted to life in trees to ground-dwelling species. Some may be active during the day (diurnal), while others are more active at night (nocturnal).
6. Taxonomy: The taxonomy and classification of snakes, including Dipsadinae, are subject to ongoing research and revision. New species are sometimes discovered, and advances in genetic analysis may lead to changes in their classification.

For the most up-to-date and specific information on Dipsadine snakes, I recommend consulting recent scientific literature, field guides, or reaching out to herpetological experts and institutions that specialize in snake research.

The research, which confirms both what is known about how evolution works, and the fact that the scientists have no doubts at all about the power of the Theory of Evolution by Natural Selection to explain and understand what can be observed, is explained in a University of Texas news article by Katherine Egan Bennett:

By studying the skull shapes of dipsadine snakes, researchers at The University of Texas at Arlington have found how these species of snakes in Central and South America have evolved and adapted to meet the demands of their habitats and food sources.

The research, conducted in collaboration with colleagues at the University of Michigan, was published in the peer-reviewed journal BMC Ecology and Evolution.

We now have evidence that this group of snakes is one of the most spectacular and largest vertebrate adaptive radiations currently known to science. We found that both habitat use and diet preferences are strongly correlated to skull shape in this group of snakes, indicating these are likely factors driving cranial evolution for these species.

Gregory G. Pandelis, Lead author
Collections manager
Amphibian and Reptile Diversity Research Center.
University of Texas at Arlington, TX, USA.

There are more than 800 species of dipsadine snakes, ranging from less than 12 inches to more than 9 feet in length. This subfamily of snakes is usually harmless to humans and survives on a wide range of foods—from larger creatures like birds, lizards and frogs to smaller, slimier prey like frog eggs, worms and slugs. Some species specialize in consuming specific prey—like snails—while others are generalists.

Researchers focused on skull evolution because skull shape has important functional consequences for snakes, including prey acquisition and ingestion, habitat use, mate choice and defense against predators. Snakes, of course, don’t have limbs, so their skulls play a critical role in moving through their habitat and catching and eating prey much larger than their body size would suggest is possible.

To examine the evolution of skull shape, researchers created 3D digital reconstructions for the skulls of 160 species of dipsadine snakes using X-ray microcomputed tomography-scanning technology (CT scanning) of preserved museum specimens. They then quantified their shape using geometric morphometrics and paired this with data they collected in the field on how these snakes lived and what they ate to explore the relationship between skull shape and ecology.

Our research shows that snakes that are aquatic (water) or fossorial (underground dwellers) seem to have the strongest selective pressure on their skulls, and evolutionary convergence is rampant among these groups. There are only a few good evolutionary solutions to the difficult problems of trying to move through dirt and water efficiently. This study provides important insights into how snakes adapt to their highly unique ways of eating and inhabiting their environments, although there is much that we still don’t know about these enigmatic and fascinating animals.

Gregory G. Pandelis

More detail is given in the open access paper in BMC Ecology and Evolution

Abstract

Background

Dipsadine snakes represent one of the most spectacular vertebrate radiations that have occurred in any continental setting, with over 800 species in South and Central America. Their species richness is paralleled by stunning ecological diversity, ranging from arboreal snail-eating and aquatic eel-eating specialists to terrestrial generalists. Despite the ecological importance of this clade, little is known about the extent to which ecological specialization shapes broader patterns of phenotypic diversity within the group. Here, we test how habitat use and diet have influenced morphological diversification in skull shape across 160 dipsadine species using micro-CT and 3-D geometric morphometrics, and we use a phylogenetic comparative approach to test the contributions of habitat use and diet composition to variation in skull shape among species.

Results

We demonstrate that while both habitat use and diet are significant predictors of shape in many regions of the skull, habitat use significantly predicts shape in a greater number of skull regions when compared to diet. We also find that across ecological groupings, fossorial and aquatic behaviors result in the strongest deviations in morphospace for several skull regions. We use simulations to address the robustness of our results and describe statistical anomalies that can arise from the application of phylogenetic generalized least squares to complex shape data.

Conclusions

Both habitat and dietary ecology are significantly correlated with skull shape in dipsadines; the strongest relationships involved skull shape in snakes with aquatic and fossorial lifestyles. This association between skull morphology and multiple ecological axes is consistent with a classic model of adaptive radiation and suggests that ecological factors were an important component in driving morphological diversification in the dipsadine megaradiation.

Background

Understanding the dynamics and causes of ecological and morphological diversification during major radiations is a key challenge in evolutionary biology. The relationship between ecology and morphology is central to our ability to test the role of ecological opportunity and other factors in mediating lineage and phenotype diversification during such radiations [1,2,3]. However, the ecological basis of phenotypic variation – while readily identifiable with relatively simple phenotypic traits [4] – presents an acute challenge when considering complex, highly-integrated and/or modular morphological structures [5, 6] with multiple functional modalities, such as the vertebrate skull. Previous work on vertebrate skulls has revealed an unexpected complexity to the form-function-ecology relationship [7,8,9]. Obtaining a clear picture of how this highly intricate structure diversifies in parallel with ecological factors has the potential to illuminate how and why some vertebrate clades have become so much more diverse than others, even when those other lineages appear to have had similar ecological opportunity and biogeographic context. In this article, we describe the evolutionary dynamics of the skull during one of the most diverse continental vertebrate radiations: the dipsadine snakes, which have undergone an extraordinary evolutionary explosion in the neotropics [10], diversifying into at least 806 species [11, 12] and a wide variety of ecological roles. In many cases, dipsadines account for over 50% of the species richness within neotropical snake communities [10, 13,14,15]. The (new world or western hemisphere) dipsadine megaradiation has received relatively little attention from a macroevolutionary perspective, despite its extreme ecological and morphological diversity (Figs. 1 and 2).

Diversity of neotropical dipsadine snakes. A – Leptodeira septentrionalis, a semi-arboreal frog specialist; B – Dipsas catesbyi, an arboreal snail-eating specialist; C – Oxyrhopus melanogenys, a terrestrial snake that typically feeds on reptiles; D – Imantodes lentiferus, an arboreal frog-eater; E – Atractus elaps, a small semi-fossorial snake that feeds on annelids; F – Xenopholis scalaris, a cryptic amphibian specialist, pictured here in a defensive flattening posture. See Fig. 2 for the skull morphology of these same six groups.

Photographs by G. Pandelis.

Ecological and morphological diversity across the dipsadine megaradiation. Habitat use and diet groups appear to have independent origins in multiple clades. Skull morphology is highly variable across the radiation, with conspicuous instances of probable convergence – for instance, note the remarkable morphological similarity between Heterodon, (G), an early-diverging North American dipsadine clade and Xenodon, (H), a deeply nested genus found in Central and South America. Position of skulls does not necessarily align with position in tree; circled letters correspond to the phylogenetic position of labeled skulls (uncircled). Skulls A-F correspond to the groups of the same letter pictured in Fig. 1. Abbreviations: Tret. – Tretanorhinus, Ima. – Imantodes, Het. – Heterodon, Far. – Farancia, Aposto. – Apostolepis, Taenio. – Taeniophallus, Xen. – Xenopholis, Lygo. – Lygophis, Urom. – Uromacer. A version of this figure with tip labels is available in the supporting material (Fig. S1)

Pandelis, G.G., Grundler, M.C. & Rabosky, D.L.
Ecological correlates of cranial evolution in the megaradiation of dipsadine snakes.
BMC Ecol Evo 23, 48 (2023). https://doi.org/10.1186/s12862-023-02157-3

Copyright: © 2023 The authors.
Published by BioMed Central Ltd (Springer Nature Ltd.) Open access.
Reprinted under a Creative Commons Attribution 4.0 International license (CC BY 4.0)

This piece of research should worry creationist, if any find the courage to read it, for two reasons:

Firstly, there is the confirmation of the role of natural selection in the morphology of organisms and their radiation from a common ancestor found in the similarities and difference of the skulls of related snakes, and the close association between that morphology and habitat and prey.

Secondly, there is the reliance of the scientists on the Theory of Evolution by Natural Selection to explain these relationships, with no hint that the TOE is about to be abandonned in favour of a magical notion including supernatural entities, as creationist cult leaders tell their dupes is about to happen - for the last 30 or more years.

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