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.

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 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 Evolution in Extremis: The When, How, and Why of Hawaiian Carabid Beetles

2019 ◽  
Vol 2 ◽  
Author(s):  
James Liebherr
Keyword(s):  
Sexual Selection ◽  
Body Size ◽  
Small Body ◽  
Carabid Beetle ◽  
Carabid Beetles ◽  
Habitat Specialization ◽  
Dispersal Ability ◽  
Ecological Specialization ◽  
Hawaiian Archipelago ◽  
Ecological Zones

The Hawaiian Archipelago is the most isolated oceanic island system in the World, separated from the nearest source areas by more than 4000 km. Five independent colonization events have resulted in diversification of a native carabid beetle fauna in excess of 400 known species. This diverse assemblage is disharmonic, with the major radiations restricted to the platynine genus Blackburnia Sharp (139 species), the subgenus Nesocidium Sharp of Bembidion Latreille (21 species), and the moriomorphine genus Mecyclothorax Sharp (239 species). Biogeographical, ecological, and evolutionary attributes of these three radiations are compared in order to determine factors crucial to carabid beetle diversification in this most-isolated situation. Biogeographical attributes include the age of origin of the constituent radiation, the island likely colonized by its common ancestor, and the biological characteristics, where known, of the colonizing ancestors for each independent radiation. Ecological attributes include the amount of habitat specialization undergone during each radiation, taking into account the primordial habitat colonized and the subsequent pattern of occupation of different habitat types during diversification. Evolutionary attributes include brachyptery, body-size evolution, sexual selection, and the evolution of specialized body conformations. It is shown that ecological specialization—i.e., occupation of a diverse array of ecological zones and microhabitats—in concert with reduced dispersal ability brought on by evolution of brachyptery are positively associated with enhanced levels of diversification. Comparing sympatric island faunas, it is shown that the latter operates synergistically with body size, as the smaller-bodied Mecyclothorax beetles speciate much more rapidly than the larger-bodied Blackburnia on Maui and Hawai῾i Island. Nonetheless, small body size does not gaurantee high diversity, as Bembidion beetles attain body sizes similar to Mecyclothorax beetles. Age of origin of a radiation is a subsidiary criterion for diversification given that the Mecyclothorax radiation commenced only 1.2 Ma, whereas it is hypothesized that Blackburnia have been resident in the Hawaiian archipelago for upwards of 28 Ma. Thus especially for Blackburnia we are constrained in our ability to know all of the evolutionary products of the radiation due to extinction of presumably all or nearly all species that occupied the now-sunken islands northwest of the oldest high island of Kauai. We are fortunate to know of several extinct Blackburnia species discovered in lowland subfossil deposits in Kauai, and these species provide crucial information now regarding future patterns of extinction. Sexual selection can be demonstrated for the Bembidion subgenus Nesocidium, and is a likely explanation for genitalic evolution over parts of the Mecyclothorax radiation, but it is not a phenomenon pervasively associated with increased levels of speciation.

scholarly journals Biological and extrinsic correlates of extinction risk in Chinese lizards

2021 ◽  
Author(s):  
Yuxi Zhong ◽  
Chuanwu Chen ◽  
Yanping Wang
Keyword(s):  
Body Size ◽  
Extinction Risk ◽  
Species Traits ◽  
Geographic Range ◽  
Range Size ◽  
Habitat Specialization ◽  
Mean Annual Precipitation ◽  
Mean Annual Temperature ◽  
Small Range ◽  
Extrinsic Factors

Abstract China is a country with one of the most species rich reptile faunas in the world. However, nearly a quarter of Chinese lizard species assessed by the China Biodiversity Red List are threatened. Nevertheless, to date, no study has explicitly examined the pattern and processes of extinction and threat in Chinese lizards. In this study, we conducted the first comparative phylogenetic analysis of extinction risk in Chinese lizards. We addressed the following three questions: 1) What is the pattern of extinction and threat in Chinese lizards? 2) Which species traits and extrinsic factors are related to their extinction risk? 3) How can we protect Chinese lizards based on our results? We collected data on ten species traits (body size, clutch size, geographic range size, activity time, reproductive mode, habitat specialization, habitat use, leg development, maximum elevation, and elevation range) and seven extrinsic factors (mean annual precipitation, mean annual temperature, mean annual solar insolation, normalized difference vegetation index (NDVI), human footprint, human population density, and human exploitation). After phylogenetic correction, these variables were used separately and in combination to assess their associations with extinction risk. We found that Chinese lizards with small geographic range, large body size, high habitat specialization, and living in high precipitation areas were vulnerable to extinction. Conservation priority should thus be given to species with the above extinction-prone traits so as to effectively protect Chinese lizards. Preventing future habitat destruction should also be a primary focus of management efforts because species with small range size and high habitat specialization are particularly vulnerable to habitat loss.

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.

Calibration of Test Diameter and Area As Proxies For Body Size in the Planktonic Foraminifer Globoconella Puncticulata

2018 ◽  
Vol 48 (3) ◽  
pp. 241-245 ◽  
Author(s):  
Anieke Brombacher ◽  
Leanne E. Elder ◽  
Pincelli M. Hull ◽  
Paul A. Wilson ◽  
Thomas H. G. Ezard
Keyword(s):  
Body Size ◽  
Morphological Change ◽  
Statistical Power ◽  
Three Dimensional ◽  
Body Volume ◽  
Test Diameter ◽  
Linear Measurements ◽  
Cross Sectional ◽  
Test Volume ◽  
Computed Tomography Scanning

Abstract Body size is one of the most commonly measured traits in ecology and evolution because it covaries with environmental (e.g., temperature, latitude, degree of population isolation) and life-history (e.g., metabolic rate, generation time) traits. However, the driving mechanisms of body size variation in the distant geological past are poorly known and complicated by partial specimen recovery, limited population-level sampling, and the use of linear measurements as proxies for three-dimensional volumetric-size data. How much information are we missing by using approximate metrics of body size? Here we examine this question in an evolving lineage of planktonic foraminifera. We measure test diameter and surface area of over 500 individuals of the species Globoconella puncticulata using two-dimensional images. These results are compared with measurements of test volume of the same individuals as measured by a recently developed high-throughput method for analysing three-dimensional morphometrics as well as high-resolution three-dimensional computed tomography scanning. Our results show that even in a lineage showing substantial morphological change, a cross-sectional test area can provide a consistent proxy for body volume. Approximating body volume with one-dimensional (linear) size measurements is more problematic as it systematically over- and underestimates the smallest and largest tests, respectively. In our study, shape (here measured as shell-aspect ratio) only explained marginally more variation when included in the regressions. The use of 3D light microscopy introduces a small degree of scatter in the data, but the number of individuals necessary to detect trends in body size with sufficient statistical power is comparable to the sample size required for other traits. These results imply that even in an evolving lineage undergoing substantial morphological change, cross-sectional area can provide a consistent proxy for body size.

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 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.

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