scholarly journals Solitary ecology as a phenomenon extending beyond insular systems: exaptive evolution in Anolis lizards

2019 ◽  
Vol 15 (5) ◽  
pp. 20190056 ◽  
Author(s):  
Julián A. Velasco ◽  
Steven Poe ◽  
Constantino González-Salazar ◽  
Oscar Flores-Villela
Keyword(s):  
Body Size ◽  
Adaptive Evolution ◽  
Environmental Filtering ◽  
Phenotypic Evolution ◽  
Phenotypic Differentiation ◽  
Evolutionary Transitions ◽  
Ecological Release ◽  
Selective Pressures ◽  
Island Species

The mechanisms driving phenotypic evolution have been of interest to biologists since Darwin. Ecological release—wherein adaptive evolution occurs following relaxation of constraining selective pressures—and environmental filtering—wherein exaptive traits allow colonization of a new area—have been studied in several insular cases. Anolis lizards, which may exist in solitude or sympatry with multiple congeners, are an excellent system for evaluating whether ecological release and environmental filtering are associated with phenotypic shifts across phylogenetic and geographical scales. Insular solitary Anolis exhibit phenotypic differentiation in body size and sexual size dimorphism—SSD—through exaptive and adaptive evolution, respectively. But, the generality of these effects has not yet been addressed. Here, we analyse the evolution of body size and SSD relative to sympatry in mainland Anolis . We found that mainland species co-occurring with few congeners exhibit uniform body size and greater SSD relative to other random mainland assemblages, consistent with the insular solitary pattern. The locations of evolutionary shifts for both traits do not coincide with evolutionary transitions to decreased levels of sympatry. These results are consistent with exaptive environmental filtering but not adaptive ecological release. Future studies should be conducted at local scales to evaluate the role of these factors in the evolution of solitary existence in mainland and island species.

scholarly journals New insights on equid locomotor evolution from the lumbar region of fossil horses

2016 ◽  
Vol 283 (1829) ◽  
pp. 20152947 ◽  
Author(s):  
Katrina Elizabeth Jones
Keyword(s):  
Body Size ◽  
Adaptive Evolution ◽  
Axial Skeleton ◽  
Lumbar Region ◽  
Scaling Effects ◽  
Classic Case ◽  
Strong Selection ◽  
Selection For ◽  
Joint Shape

The specialization of equid limbs for cursoriality is a classic case of adaptive evolution, but the role of the axial skeleton in this famous transition is not well understood. Extant horses are extremely fast and efficient runners, which use a stiff-backed gallop with reduced bending of the lumbar region relative to other mammals. This study tests the hypothesis that stiff-backed running in horses evolved in response to evolutionary increases in body size by examining lumbar joint shape from a broad sample of fossil equids in a phylogenetic context. Lumbar joint shape scaling suggests that stability of the lumbar region does correlate with size through equid evolution. However, scaling effects were dampened in the posterior lumbar region, near the sacrum, which suggests strong selection for sagittal mobility in association with locomotor–respiratory coupling near the lumbosacral joint. I hypothesize that small-bodied fossil horses may have used a speed-dependent running gait, switching between stiff-backed and flex-backed galloping as speed increased.

scholarly journals The importance of alternative splicing in adaptive evolution

2021 ◽  
Author(s):  
Pooja Singh ◽  
Ehsan Pashay Ahi
Keyword(s):  
Gene Expression ◽  
Alternative Splicing ◽  
Adaptive Evolution ◽  
Adaptive Divergence ◽  
Mrna Isoforms ◽  
Evolutionary Transitions ◽  
Splice Variation ◽  
Gene Regulatory ◽  
Splice Forms

Although alternative splicing is a ubiquitous gene regulatory mechanism in plants and animals, its contribution to evolutionary transitions is understudied. Splicing enables different mRNA isoforms to be generated from the same gene, expanding transcriptomic and proteomic diversity. While the role of gene expression in adaptive evolution is widely accepted, biologists still debate the functional impact of alternative isoforms on phenotype. In light of recent empirical research linking splice variation to ecological adaptations, we propose that alternative splicing is an important substrate for adaptive evolution and speciation, particularly at short timescales. We synthesise what is known about the role of splicing in adaptive evolution. We discuss the contribution of standing splice variation to phenotypic plasticity and how hybridisation can produce novel splice forms. Going forwards, we propose that splicing be included as a standard analysis alongside gene expression analysis so we can better understand of how splicing contributes to adaptive divergence at the micro- and macroevolutionary levels.

scholarly journals The geographical diversification in varanid lizards: the role of mainland versus island in driving species evolution

2020 ◽  
Vol 66 (2) ◽  
pp. 165-171
Author(s):  
Xia-Ming Zhu ◽  
Yu Du ◽  
Yan-Fu Qu ◽  
Hong Li ◽  
Jian-Fang Gao ◽  
...  
Keyword(s):  
Body Size ◽  
Joint Effect ◽  
Offspring Quality ◽  
Frequency Distributions ◽  
Island Species ◽  
Size Frequency ◽  
Wide Range ◽  
Body Sizes ◽  
Species Evolution

Abstract Monitor lizards (Varanidae) inhabit both the mainland and islands of all geological types and have diversified into an exceptionally wide range of body sizes, thus providing an ideal model for examining the role of mainland versus island in driving species evolution. Here we use phylogenetic comparative methods to examine whether a link exists between body size-driven diversification and body size-frequency distributions in varanid lizards and to test the hypothesis that island lizards differ from mainland species in evolutionary processes, body size, and life-history traits (offspring number and size). We predict that: 1) since body size drives rapid diversification in groups, a link exists between body size-driven diversification and body size-frequency distributions; 2) because of various environments on island, island species will have higher speciation, extinction, and dispersal rates, compared with mainland species; 3) as a response to stronger intraspecific competition, island species will maximize individual ability associated with body size to outcompete closely-related species, and island species will produce smaller clutches of larger eggs to increase offspring quality. Our results confirm that the joint effect of differential macroevolutionary rates shapes the species richness pattern of varanid lizards. There is a link between body size-driven diversification and body size-frequency distributions, and the speciation rate is maximized at medium body sizes. Island species will have higher speciation, equal extinction, and higher dispersal rates compared with mainland species. Smaller clutch size and larger hatchling in the island than in mainland species indicate that offspring quality is more valuable than offspring quantity for island varanids.

scholarly journals Do avian species survive better on islands?

2021 ◽  
Vol 17 (1) ◽  
pp. 20200643
Author(s):  
Guy Beauchamp
Keyword(s):  
Life History ◽  
Body Size ◽  
Clutch Size ◽  
Ecological Factors ◽  
Adult Survival ◽  
Apparent Survival ◽  
Island Species ◽  
Island Syndrome ◽  
Shed Light

Island species are often predictably different from their mainland counterparts. Milder climates and reduced predation risk on islands have been involved to explain shifts in body size and a suite of life-history traits such as clutch size and offspring growth rate. Despite the key role of adult survival on risk taking and reproduction, the prediction that living on islands increases adult survival has yet to be tested systematically. I gathered data on adult annual apparent survival from the island and mainland year-round resident species of birds from around the world. With this large dataset (697 species), I found that species of birds living on islands showed higher apparent survival than their mainland counterparts in the two Hemispheres and at all latitudes, controlling for several known predictors of adult survival, including body size, clutch size and breeding system. These results shed light on the ecological factors that influence survival on islands and extend the life-history island syndrome to adult survival.

Testing ecological release as a compensating mechanism for mass mortality in a keystone predator

2020 ◽  
Vol 637 ◽  
pp. 59-69 ◽  
Author(s):  
J Sullivan-Stack ◽  
BA Menge
Keyword(s):  
Community Dynamics ◽  
Limiting Factor ◽  
Sea Star ◽  
Top Predator ◽  
Oregon Coast ◽  
Ecological Release ◽  
Keystone Predator ◽  
Pisaster Ochraceus ◽  
Wasting Syndrome

Top predator decline has been ubiquitous across systems over the past decades and centuries, and predicting changes in resultant community dynamics is a major challenge for ecologists and managers. Ecological release predicts that loss of a limiting factor, such as a dominant competitor or predator, can release a species from control, thus allowing increases in its size, density, and/or distribution. The 2014 sea star wasting syndrome (SSWS) outbreak decimated populations of the keystone predator Pisaster ochraceus along the Oregon coast, USA. This event provided an opportunity to test the predictions of ecological release across a broad spatial scale and determine the role of competitive dynamics in top predator recovery. We hypothesized that after P. ochraceus loss, populations of the subordinate sea star Leptasterias sp. would grow larger, more abundant, and move downshore. We based these predictions on prior research in Washington State showing that Leptasterias sp. competed with P. ochraceus for food. Further, we predicted that ecological release of Leptasterias sp. could provide a bottleneck to P. ochraceus recovery. Using field surveys, we found no clear change in density or distribution in Leptasterias sp. populations post-SSWS, and decreases in body size. In a field experiment, we found no evidence of competition between similar-sized Leptasterias sp. and P. ochraceus. Thus, the mechanisms underlying our predictions were not in effect along the Oregon coast, which we attribute to differences in habitat overlap and food availability between the 2 regions. Our results suggest that response to the loss of a dominant competitor can be unpredictable even when based in theory and previous research.

scholarly journals Landscape resistance constrains hybridization across contact zones in a reproductively and morphologically polymorphic salamander

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Guillermo Velo-Antón ◽  
André Lourenço ◽  
Pedro Galán ◽  
Alfredo Nicieza ◽  
Pedro Tarroso
Keyword(s):  
Contact Zone ◽  
Environmental Heterogeneity ◽  
Evolutionary Dynamics ◽  
Morphological Differentiation ◽  
Phenotypic Traits ◽  
Hybrid Zones ◽  
Landscape Resistance ◽  
Phenotypic Differentiation ◽  
Contact Zones

AbstractExplicitly accounting for phenotypic differentiation together with environmental heterogeneity is crucial to understand the evolutionary dynamics in hybrid zones. Species showing intra-specific variation in phenotypic traits that meet across environmentally heterogeneous regions constitute excellent natural settings to study the role of phenotypic differentiation and environmental factors in shaping the spatial extent and patterns of admixture in hybrid zones. We studied three environmentally distinct contact zones where morphologically and reproductively divergent subspecies of Salamandra salamandra co-occur: the pueriparous S. s. bernardezi that is mostly parapatric to its three larviparous subspecies neighbours. We used a landscape genetics framework to: (i) characterise the spatial location and extent of each contact zone; (ii) assess patterns of introgression and hybridization between subspecies pairs; and (iii) examine the role of environmental heterogeneity in the evolutionary dynamics of hybrid zones. We found high levels of introgression between parity modes, and between distinct phenotypes, thus demonstrating the evolution to pueriparity alone or morphological differentiation do not lead to reproductive isolation between these highly divergent S. salamandra morphotypes. However, we detected substantial variation in patterns of hybridization across contact zones, being lower in the contact zone located on a topographically complex area. We highlight the importance of accounting for spatial environmental heterogeneity when studying evolutionary dynamics of hybrid zones.

scholarly journals Multifunctional Role of Astrocyte Elevated Gene-1 (AEG-1) in Cancer: Focus on Drug Resistance

Cancers ◽  
2021 ◽  
Vol 13 (8) ◽  
pp. 1792
Author(s):  
Debashri Manna ◽  
Devanand Sarkar
Keyword(s):  
Drug Resistance ◽  
Cancer Cells ◽  
Cancer Development ◽  
Epigenetic Alterations ◽  
Hallmarks Of Cancer ◽  
Comprehensive Description ◽  
Molecular Abnormalities ◽  
Selective Pressures ◽  
Resistance To Chemotherapy

Cancer development results from the acquisition of numerous genetic and epigenetic alterations in cancer cells themselves, as well as continuous changes in their microenvironment. The plasticity of cancer cells allows them to continuously adapt to selective pressures brought forth by exogenous environmental stresses, the internal milieu of the tumor and cancer treatment itself. Resistance to treatment, either inherent or acquired after the commencement of treatment, is a major obstacle an oncologist confronts in an endeavor to efficiently manage the disease. Resistance to chemotherapy, chemoresistance, is an important hallmark of aggressive cancers, and driver oncogene-induced signaling pathways and molecular abnormalities create the platform for chemoresistance. The oncogene Astrocyte elevated gene-1/Metadherin (AEG-1/MTDH) is overexpressed in a diverse array of cancers, and its overexpression promotes all the hallmarks of cancer, such as proliferation, invasion, metastasis, angiogenesis and chemoresistance. The present review provides a comprehensive description of the molecular mechanism by which AEG-1 promotes tumorigenesis, with a special emphasis on its ability to regulate chemoresistance.

scholarly journals Assessing evidence for adaptive evolution in two hearing-related genes important for high-frequency hearing in echolocating mammals

2021 ◽  
Author(s):  
Hui Wang ◽  
Hanbo Zhao ◽  
Yujia Chu ◽  
Jiang Feng ◽  
Keping Sun
Keyword(s):  
Adaptive Evolution ◽  
Hair Cells ◽  
High Frequency ◽  
Phylogenetic Trees ◽  
Outer Hair Cells ◽  
Functional Domain ◽  
Coding Region ◽  
Selective Pressures ◽  
Wide Range ◽  
Different Parts

Abstract High-frequency hearing is particularly important for echolocating bats and toothed whales. Previously, studies of the hearing-related genes Prestin, KCNQ4, and TMC1 documented that adaptive evolution of high-frequency hearing has taken place in echolocating bats and toothed whales. In this study, we present two additional candidate hearing-related genes, Shh and SK2, that may also have contributed to the evolution of echolocation in mammals. Shh is a member of the vertebrate Hedgehog gene family and is required in the specification of the mammalian cochlea. SK2 is expressed in both inner and outer hair cells, and it plays an important role in the auditory system. The coding region sequences of Shh and SK2 were obtained from a wide range of mammals with and without echolocating ability. The topologies of phylogenetic trees constructed using Shh and SK2 were different; however, multiple molecular evolutionary analyses showed that those two genes experienced different selective pressures in echolocating bats and toothed whales compared to non-echolocating mammals. In addition, several nominally significant positively selected sites were detected in the non-functional domain of the SK2 gene, indicating that different selective pressures were acting on different parts of the SK2 gene. This study has expanded our knowledge of the adaptive evolution of high-frequency hearing in echolocating mammals.

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