Warning signals promote morphological diversification in fossorial uropeltid snakes (Squamata: Uropeltidae)

2020 ◽  
Author(s):  
Vivek Philip Cyriac ◽  
Ullasa Kodandaramaiah
Keyword(s):  
Body Size ◽  
Free Space ◽  
Morphological Evolution ◽  
Environmental Constraints ◽  
Shape Evolution ◽  
Head Shape ◽  
Warning Signals ◽  
Morphological Diversification ◽  
Niche Expansion ◽  
Antipredator Defences

Abstract Many species possess warning colourations that signal unprofitability to predators. Warning colourations are also thought to provide prey with a ‘predator-free space’ and promote niche expansion. However, how such strategies release a species from environmental constraints and facilitate niche expansion is not clearly understood. Fossoriality in reptiles imposes several morphological limits on head and body size to facilitate burrowing underground, but many fossorial snakes live close to the surface and occasionally move above ground, exposing them to predators. In such cases, evolving antipredator defences that reduce predation on the surface could potentially relax the morphological constraints associated with fossoriality and promote morphological diversification. Fossorial uropeltid snakes possess varying degrees of conspicuous warning colourations that reduce avian predation when active above ground. We predicted that species with more conspicuous colourations will exhibit more robust body forms and show faster rates of morphological evolution because constraints imposed by fossoriality are relaxed. Using a comparative phylogenetic approach on the genus Uropeltis, we show that more conspicuous species tend to have more robust morphologies and have faster rates of head-shape evolution. Overall, we find that the evolution of warning colourations in Uropeltis can facilitate niche expansion by influencing rates of morphological diversification.

scholarly journals Do Coral Reefs Promote Morphological Diversification? Exploration of Habitat Effects on Labrid Pharyngeal Jaw Evolution in the Era of Big Data

2019 ◽  
Vol 59 (3) ◽  
pp. 696-704 ◽  
Author(s):  
Kory M Evans ◽  
Keiffer L Williams ◽  
Mark W Westneat
Keyword(s):  
Coral Reef ◽  
Coral Reefs ◽  
Morphological Evolution ◽  
Morphological Data ◽  
Shape Evolution ◽  
Micro Computed Tomography ◽  
Functional Variation ◽  
Morphological Diversification ◽  
Marine Habitats ◽  
Pharyngeal Jaw

Abstract Coral reefs are complex marine habitats that have been hypothesized to facilitate functional specialization and increased rates of functional and morphological evolution. Wrasses (Labridae: Percomorpha) in particular, have diversified extensively in these coral reef environments and have evolved adaptations to further exploit reef-specific resources. Prior studies have found that reef-dwelling wrasses exhibit higher rates of functional evolution, leading to higher functional variation than in non-reef dwelling wrasses. Here, we examine this hypothesis in the lower pharyngeal tooth plate of 134 species of reef and non-reef-associated labrid fishes using high-resolution morphological data in the form of micro-computed tomography scans and employing three-dimensional geometric morphometrics to quantify shape differences. We find that reef-dwelling wrasses do not differ from non-reef-associated wrasses in morphological disparity or rates of shape evolution. However, we find that some reef-associated species (e.g., parrotfishes and tubelips) exhibit elevated rates of pharyngeal jaw shape evolution and have colonized unique regions of morphospace. These results suggest that while coral reef association may provide the opportunity for specialization and morphological diversification, species must still be able to capitalize on the ecological opportunities to invade novel niche space, and that these novel invasions may prompt rapid rates of morphological evolution in the associated traits that allow them to capitalize on new resources.

scholarly journals Arboreality constrains morphological evolution but not species diversification in vipers

2017 ◽  
Vol 284 (1869) ◽  
pp. 20171775 ◽  
Author(s):  
Laura Rodrigues Vieira de Alencar ◽  
Marcio Martins ◽  
Gustavo Burin ◽  
Tiago Bosisio Quental
Keyword(s):  
New Species ◽  
Body Size ◽  
Morphological Evolution ◽  
Trait Evolution ◽  
Morphological Diversification ◽  
Body Sizes ◽  
Speciation Rates ◽  
Slender Bodies ◽  
Morphological Variants ◽  
Arboreal Snakes

An increase in ecological opportunities, either through changes in the environment or acquisition of new traits, is frequently associated with an increase in species and morphological diversification. However, it is possible that certain ecological settings might prevent lineages from diversifying. Arboreality evolved multiple times in vipers, making them ideal organisms for exploring how potentially new ecological opportunities affect their morphology and speciation regimes. Arboreal snakes are frequently suggested to have a very specialized morphology, and being too large, too small, too heavy, or having short tails might be challenging for them. Using trait-evolution models, we show that arboreal vipers are evolving towards intermediate body sizes, with longer tails and more slender bodies than terrestrial vipers. Arboreality strongly constrains body size and circumference evolution in vipers, while terrestrial lineages are evolving towards a broader range of morphological variants. Trait-dependent diversification models, however, suggest similar speciation rates between microhabitats. Thus, we show that arboreality might constrain morphological evolution but not necessarily affect the rates at which lineages generate new species.

scholarly journals Ecological specialization, rather than the island rule, explains morphological diversification in an ancient radiation of geckos

2021 ◽  
Author(s):  
Héctor Tejero-Cicuéndez ◽  
Marc Simó-Riudalbas ◽  
Iris Menéndez ◽  
Salvador Carranza
Keyword(s):  
Body Size ◽  
Morphological Change ◽  
Morphological Evolution ◽  
Habitat Specialization ◽  
Ecological Specialization ◽  
Island Rule ◽  
Morphological Diversification ◽  
Main Driver ◽  
Island System ◽  
Socotra Archipelago

Island colonists are often assumed to experience higher levels of phenotypic diversification than their continental sister taxa. However, empirical evidence shows that exceptions to the familiar "island rule" do exist. In this study, we tested this rule using a nearly complete sampled mainland-island system, the genus Pristurus, a group of sphaerodactylid geckos mainly distributed across continental Arabia and Africa and the Socotra Archipelago. We used a recently published phylogeny and an extensive dataset of morphological measures to explore whether island and mainland taxa share the same morphospace or if they present different dynamics of phenotypic evolution. Moreover, we used habitat data to examine if ecological specialization is correlated with morphological change, reconstructing the ancestral habitat states across the phylogeny to compare the level of phenotypic disparity and trait evolution between habitats. We found that insular species do not present higher levels or rates of morphological diversification than continental groups. Instead, habitat specialization provides insight into the evolution of body size and shape in Pristurus. In particular, the adaptation to exploit ground habitats seems to have been the main driver of morphological change, producing the highest levels of disparity and evolutionary rates. Additionally, arboreal species show very constrained body size and head proportions, suggesting morphological convergence driven by habitat specialization. Our results reveal a determinant role of ecological mechanisms in morphological evolution and corroborate the complexity of ecomorphological dynamics in mainland-island systems.

scholarly journals Ecological specialization, rather than the island effect, explains morphological diversification in an ancient radiation of geckos

2021 ◽  
Vol 288 (1965) ◽  
Author(s):  
Héctor Tejero-Cicuéndez ◽  
Marc Simó-Riudalbas ◽  
Iris Menéndez ◽  
Salvador Carranza
Keyword(s):  
Body Size ◽  
Morphological Change ◽  
Morphological Evolution ◽  
The Body ◽  
Habitat Specialization ◽  
Ecological Specialization ◽  
Morphological Diversification ◽  
Habitat Occupancy ◽  
Island Effect ◽  
Similar Body

Island colonists are often assumed to experience higher levels of phenotypic diversification than continental taxa. However, empirical evidence has uncovered exceptions to this ‘island effect’. Here, we tested this pattern using the geckos of the genus Pristurus from continental Arabia and Africa and the Socotra Archipelago. Using a recently published phylogeny and an extensive morphological dataset, we explore the differences in phenotypic evolution between Socotran and continental taxa. Moreover, we reconstructed ancestral habitat occupancy to examine if ecological specialization is correlated with morphological change, comparing phenotypic disparity and trait evolution between habitats. We found a heterogeneous outcome of island colonization. Namely, only one of the three colonization events resulted in a body size increase. However, in general, Socotran species do not present higher levels or rates of morphological diversification than continental groups. Instead, habitat specialization explains better the body size and shape evolution in Pristurus . Particularly, the colonization of ground habitats appears as the main driver of morphological change, producing the highest disparity and evolutionary rates. Additionally, arboreal species show very similar body size and head proportions. These results reveal a determinant role of ecological mechanisms in morphological evolution and corroborate the complexity of ecomorphological dynamics in continent–island systems.

scholarly journals Variation in pleiotropic hub gene expression is associated with interspecific differences in head shape and eye size in Drosophila

2021 ◽  
Author(s):  
Elisa Buchberger ◽  
Anıl Bilen ◽  
Sanem Ayaz ◽  
David Salamanca ◽  
Cristina Matas de las Heras ◽  
...  
Keyword(s):  
Natural Variation ◽  
Compound Eye ◽  
Genetic Manipulation ◽  
Morphological Evolution ◽  
Morphological Diversity ◽  
Network Evolution ◽  
Head Shape ◽  
Eye Size ◽  
Recurrent Mutations ◽  
Repeated Evolution

Abstract Revealing the mechanisms underlying the breath-taking morphological diversity observed in nature is a major challenge in Biology. It has been established that recurrent mutations in hotspot genes cause the repeated evolution of morphological traits, such as body pigmentation or the gain and loss of structures. To date, however, it remains elusive whether hotspot genes contribute to natural variation in the size and shape of organs. Since natural variation in head morphology is pervasive in Drosophila, we studied the molecular and developmental basis of differences in compound eye size and head shape in two closely related Drosophila species. We show differences in the progression of retinal differentiation between species and we applied comparative transcriptomics and chromatin accessibility data to identify the GATA transcription factor Pannier (Pnr) as central factor associated with these differences. Although the genetic manipulation of Pnr affected multiple aspects of dorsal head development, the effect of natural variation is restricted to a subset of the phenotypic space. We present data suggesting that this developmental constraint is caused by the co-evolution of expression of pnr and its co-factor u-shaped (ush). We propose that natural variation in expression or function of highly connected developmental regulators with pleiotropic functions is a major driver for morphological evolution and we discuss implications on gene regulatory network evolution. In comparison to previous findings, our data strongly suggests that evolutionary hotspots are not the only contributors to the repeated evolution of eye size and head shape in Drosophila.

scholarly journals Genome size drives morphological evolution in organ-specific ways

2021 ◽  
Author(s):  
Michael W Itgen ◽  
Dustin S Siegel ◽  
Stanley K Sessions ◽  
Rachel Lockridge Mueller
Keyword(s):  
Body Size ◽  
Genome Size ◽  
Cell Size ◽  
Structural Changes ◽  
Morphological Evolution ◽  
Empty Space ◽  
Developmental Rate ◽  
Cellular Interactions ◽  
Structure Changes ◽  
Organ Specific

Morphogenesis is an emergent property of biochemical and cellular interactions during development. Genome size and the correlated trait of cell size can influence these interactions through its effects on developmental rate and tissue geometry, ultimately driving the evolution of morphology. We tested the effects of genome size and body size evolution on heart and liver morphology using nine species of the salamander genus Plethodon (genome sizes 29.3-67 Gb). Our results show that whole organ size is determined by body size, whereas tissue structure changes dramatically with evolutionary increases in genome size. In the heart, increased genome size is correlated with a reduction of myocardia in the ventricle, yielding proportionally less force-producing mass and more empty space. In the liver, increased genome size is correlated with fewer and larger vascular structures, positioning hepatocytes farther from the circulatory vessels that transport key metabolites. Although these structural changes should have obvious impacts on organ function, their effects on organismal performance and fitness are likely negligible because low metabolic rates in salamanders relax selective pressure on key metabolic organ performance. Overall, this study reveals the effects of large genome and cell size on the developmental systems producing the heart and liver.

scholarly journals Rates of ecological divergence and body size evolution are correlated with species diversification in scaly tree ferns

2016 ◽  
Vol 283 (1834) ◽  
pp. 20161098 ◽  
Author(s):  
Santiago Ramírez-Barahona ◽  
Josué Barrera-Redondo ◽  
Luis E. Eguiarte
Keyword(s):  
Species Richness ◽  
Body Size ◽  
Ecological Niche ◽  
Morphological Evolution ◽  
Ecological Niches ◽  
Species Diversification ◽  
Tree Ferns ◽  
Size Evolution ◽  
Body Sizes ◽  
Body Size Evolution

Variation in species richness across regions and between different groups of organisms is a major feature of evolution. Several factors have been proposed to explain these differences, including heterogeneity in the rates of species diversification and the age of clades. It has been frequently assumed that rapid rates of diversification are coupled to high rates of ecological and morphological evolution, leading to a prediction that remains poorly explored for most species: the positive association between ecological niche divergence, morphological evolution and species diversification. We combined a time-calibrated phylogeny with distribution, ecological and body size data for scaly tree ferns (Cyatheaceae) to test whether rates of species diversification are predicted by the rates at which clades have evolved distinct ecological niches and body sizes. We found that rates of species diversification are positively correlated with rates of ecological and morphological evolution, with rapidly diversifying clades also showing rapidly evolving ecological niches and body sizes. Our results show that rapid diversification of scaly tree ferns is associated with the evolution of species with comparable morphologies that diversified into similar, yet distinct, environments. This suggests parallel evolutionary pathways opening in different tropical regions whenever ecological and geographical opportunities arise. Accordingly, rates of ecological niche and body size evolution are relevant to explain the current patterns of species richness in this ‘ancient’ fern lineage across the tropics.

scholarly journals Does aquatic foraging impact head shape evolution in snakes?

2016 ◽  
Vol 283 (1837) ◽  
pp. 20161645 ◽  
Author(s):  
Marion Segall ◽  
Raphaël Cornette ◽  
Anne-Claire Fabre ◽  
Ramiro Godoy-Diana ◽  
Anthony Herrel
Keyword(s):  
Aquatic Environment ◽  
Anterior Part ◽  
Three Dimensional ◽  
Shape Evolution ◽  
Head Shape ◽  
Evolutionary Trajectory ◽  
Biomechanical Models ◽  
Historical Factors ◽  
Evolutionary Trajectories ◽  
Do So

Evolutionary trajectories are often biased by developmental and historical factors. However, environmental factors can also impose constraints on the evolutionary trajectories of organisms leading to convergence of morphology in similar ecological contexts. The physical properties of water impose strong constraints on aquatic feeding animals by generating pressure waves that can alert prey and potentially push them away from the mouth. These hydrodynamic constraints have resulted in the independent evolution of suction feeding in most groups of secondarily aquatic tetrapods. Despite the fact that snakes cannot use suction, they have invaded the aquatic milieu many times independently. Here, we test whether the aquatic environment has constrained head shape evolution in snakes and whether shape converges on that predicted by biomechanical models. To do so, we used three-dimensional geometric morphometrics and comparative, phylogenetically informed analyses on a large sample of aquatic snake species. Our results show that aquatic snakes partially conform to our predictions and have a narrower anterior part of the head and dorsally positioned eyes and nostrils. This morphology is observed, irrespective of the phylogenetic relationships among species, suggesting that the aquatic environment does indeed drive the evolution of head shape in snakes, thus biasing the evolutionary trajectory of this group of animals.

scholarly journals The impact of diet, habitat use, and behaviour on head shape evolution in homalopsid snakes

2016 ◽  
Vol 118 (3) ◽  
pp. 634-647 ◽  
Author(s):  
Anne-Claire Fabre ◽  
David Bickford ◽  
Marion Segall ◽  
Anthony Herrel
Keyword(s):  
Habitat Use ◽  
Shape Evolution ◽  
Head Shape ◽  
The Impact
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