Adaptive Radiation

Ecology ◽  
2019 ◽  
Author(s):  
Linyi Zhang ◽  
Scott P. Egan
Keyword(s):  
Adaptive Radiation ◽  
Evolutionary Process ◽  
Ecological Traits ◽  
Rapid Diversification ◽  
African Rift ◽  
Rift Lake ◽  
Multiple Species ◽  
Definition Of ◽  
Life On Earth ◽  
Diversity Of Life

The spectacular diversity of life on earth presents one of the most intriguing questions for biologists: why and how does the variation among organisms arise? One powerful concept that has its origins with Darwin (late 1800s) and was developed in detail during the Modern Synthesis (early to mid-1900s), is “adaptive radiation.” This evolutionary process refers to the rapid diversification of a single lineage into many different species during which different morphological/ecological traits evolve in association with different environments and niches. The central components of adaptive radiation are (1) rapid diversification of multiple species from a single common ancestor and (2) different species exhibit different ecological traits that are adaptive to different niches. While many great individual cases of adaptive radiation have been studied, such as Darwin’s finches, African rift lake cichlids, and Hawaiian silverswords, controversies remain on topics such as the definition of an adaptive radiation, the appropriate approach to test for it, and the ultimate causes of an adaptive radiation. This article provides a general overview of the literature addressing the study of adaptive radiation, including taxa-specific examples and major literature reviews. The article will highlight literature that helps to clarify the concept of adaptive radiation by distinguishing it from other related biological processes. Then the literature on specific approaches to test for adaptive radiation is featured. Next, connections to the literature aiming to understand the proximate and ultimate causes of adaptive radiation are provided, including explicit tests of the role of ecology, as well as an exploration of the source of genetic variation and geographic conditions promoting adaptive radiation. Lastly, we connect to the literature addressing the constraints on adaptive radiations. Overall, this article will address research on the origin of new species and the evolution of ecological differences between them.

Adaptation

2001 ◽  
Author(s):  
David Reznick ◽  
Joseph Travis
Keyword(s):  
Natural Selection ◽  
Charles Darwin ◽  
Theory Of Evolution ◽  
Cause And Effect ◽  
Evolution By Natural Selection ◽  
Definition Of ◽  
Life On Earth ◽  
Diversity Of Life ◽  
First Time ◽  
Over Time

When Charles Darwin and Alfred Russell Wallace proposed their theory of evolution by natural selection, the concepts of evolution and speciation were not new. Darwin introduced The Origin with “An Historical Sketch,” in which he summarized the work of 34 previous authors who had speculated on evolution and the origin of species. What was new about Darwin and Wallace’s proposition was natural selection as the mechanism of evolutionary change. Darwin further proposed that natural selection was a unifying process that accounts for adaptation, for speciation, and hence for the diversity of life on earth. Darwin and Wallace proposed natural selection as a process that caused evolution. Adaptations are features of organisms that were shaped by this process. The modern version of Darwin and Wallace’s theory allows for other agents of evolution, such as genetic drift, migration, and mutation, but adaptation remains a product of natural selection alone. The virtue of their proposal is that it allows us to develop testable hypotheses about cause-and-effect relationships between features of the environment and presumed adaptations. Natural selection immediately became a source of controversy, although the nature of the controversy has shifted over time. First, there has been considerable debate about the definition of adaptation (e.g., Reeve and Sherman 1993). We do not wish to add to or summarize this debate because we feel that Darwin got it right the first time. Besides defining a cause-and-effect relationship between selection and adaptation, Darwin emphasized that we should not expect organisms to be perfectly adapted to their environment. In fact, this emphasis was a large component of his argument against divine creation. For example, Darwin recognized, through his experience with artificial selection, that different aspects of morphology were in some way “tied” to one another so that selection on one trait would cause correlated changes in others that were not necessarily adaptive. He also recognized that organisms were subject to constraints that might limit their ability to adapt. Finally, he argued that how organisms evolved was a function of their history, so that the response to selection on the same trait would vary among lineages. A more telling criticism considers the application of cause-and-effect reasoning to the interpretation of features of organisms as adaptations, and hence to the empirical study of adaptation.

What is life?

1997 ◽  
Author(s):  
John Maynard Smith ◽  
Eors Szathmary
Keyword(s):  
Natural Selection ◽  
Origin Of Life ◽  
Definition Of Life ◽  
The Sun ◽  
Physical Processes ◽  
Living Things ◽  
Survival And Reproduction ◽  
The Origin Of Life ◽  
Definition Of ◽  
Life On Earth

Imagine that, when the first spacemen step out of their craft onto the surface of one of the moons of Jupiter, they are confronted by an object the size of a horse, rolling towards them on wheels, and bearing on its back a concave disc pointing towards the Sun. They will at once conclude that the object is alive, or has been made by something alive. If all they find is a purple smear on the surface of the rocks, they will have to work harder to decide. This is the phenotypic approach to the definition of life: a thing is alive if it has parts, or ‘organs’, which perform functions. William Paley explained the machine-like nature of life by the existence of a creator: today, we would invoke natural selection. There are, however, dangers in assuming that any entity with the properties of a self-regulating machine is alive, or an artefact. In section 2.2, we tell the story of a self-regulating atomic reactor, the Oklo reactor, which is neither. This story can be taken in one of three ways. First, it shows the dangers of the phenotypic definition of life: not all complex entities are alive. Second, it illustrates how the accidents of history can give rise spontaneously to surprisingly complex machine-like entities. The relevance of this to the origin of life is obvious. In essence, the problem is the following. How could chemical and physical processes give rise, without natural selection, to entities capable of hereditary replication, which would therefore, from then on, evolve by natural selection? The Oklo reactor is an example of what can happen. Finally, section 2.2 can simply be skipped: the events were interesting, but do not resemble in detail those that led to the origin of life on Earth. There is an alternative to the phenotypic definition of life. It is to define as alive any entities that have the properties of multiplication, variation and heredity. The logic behind this definition, first proposed by Muller (1966), is that a population of entities with these properties will evolve by natural selection, and hence can be expected to acquire the complex adaptations for survival and reproduction that are characteristic of living things.

scholarly journals The promise of next-generation taxonomy

Megataxa ◽  
2020 ◽  
Vol 1 (1) ◽  
pp. 35-38
Author(s):  
MIGUEL VENCES
Keyword(s):  
Machine Learning ◽  
Global Changes ◽  
Next Generation ◽  
Dna Taxonomy ◽  
Technological Developments ◽  
Baseline Information ◽  
Life On Earth ◽  
Diversity Of Life

Documenting, naming and classifying the diversity of life on Earth provides baseline information on the biosphere, which is crucially important to understand and mitigate the global changes of the Anthropocene. We should meet three main challenges, using new technological developments without throwing the well-tried and successful foundations of Linnaean nomenclature overboard. 1. Fully embrace cybertaxonomy, machine learning and DNA taxonomy to ease, not burden the workflow of taxonomists. 2. Emphasize diagnosis over description, images over words. 3. Understand promises and pitfalls of omics approaches to avoid taxonomic inflation.

Notes on the genus Cactodera Krall & Krall, 1978 and proposal of Betulodera betulae gen. nov., comb. nov. (Nematoda: Heteroderidae)

Nematology ◽  
2002 ◽  
Vol 4 (7) ◽  
pp. 875-882 ◽  
Author(s):  
Dieter Sturhan
Keyword(s):  
Adaptive Radiation ◽  
New Genus ◽  
Morphological Characteristics ◽  
Sensu Stricto ◽  
Lateral Field ◽  
Second Stage ◽  
Species Inquirenda ◽  
Definition Of ◽  
Relationship Of ◽  
The Relationship

AbstractBased mainly on an analysis of the host ranges of the species presently placed in Cactodera, sensu lato, and of selected morphological characteristics, an attempt is made to improve the definition of the genus which, after exclusion of C. betulae and C. johanseni, is considered to be monophyletic. The host range of Cactodera, sensu stricto, appears to be restricted to the subclass Caryophyllidae with the ten known species showing an adaptive radiation on host genera in five families of the orders Caryophyllales and Polygonales. This may be a result of co-evolution. Cactodera betulae cannot be assigned to any of the presently recognised genera of cyst-forming nematodes and therefore Betulodera gen. nov. is proposed with B. betulae comb. nov. as the type and only species. The relationship of Betulodera gen. nov. to other genera of Heteroderidae and to some undescribed heteroderid species has still to be evaluated. The new genus is characterised by circumfenestrate cysts with only a slightly protruding vulval cone, three incisures in the lateral field of the second-stage juveniles and presence of phasmids in the males. The hosts are in unrelated plant orders and subclasses. Cactodera aquatica, a species inquirenda, is returned to the genus Heterodera and Heterodera johanseni (Sharma et al. , 2001) comb. nov. is proposed for C. johanseni.

Questioning Nature and Environmental Ethics in Schools

2020 ◽  
Author(s):  
Jorge Moreira ◽  
Fátima Alves ◽  
Ana Mendonça
Keyword(s):  
Environmental Ethics ◽  
Social Order ◽  
Learning System ◽  
Social Dimensions ◽  
Pedagogical Strategies ◽  
The World ◽  
Relevant Role ◽  
Educational Paradigm ◽  
Life On Earth ◽  
Diversity Of Life

Contemporary sciences and societies are facing several problems when analyzing the relationship between the natural and social dimensions of the world as reflected in the field of education. A serious effort must be urgently made to identify and tackle environmental problems in order to understand the world in which we live, in ways that are beneficial to present and future life on Earth. In this context, it is fundamental to create a new social order in a way that thinking “out of the box” can emerge with other orders closer to the diversity of life that coexist on the planet. Consequently, the awareness of the complexity and multidimensionality of our world requires the building of new forms of reflexivity and the development of critical thinking, reversing the still predominant characteristics of modern societies such as compartmentalization of knowledge, unhealthy competition, profit-seeking motivations, the exploitation of nature, and excessive individualist and anthropocentric approaches. In this regard, educational institutions play a relevant role in shaping future human actions to be more ethically harmonic (both environmentally and socially) as they are sites of knowledge production and sharing. Hence, it is crucial to rethink the entire educational paradigm and learning system (objectives, curricula, pedagogical strategies, instruments, competencies, school management framework, and even school buildings), because schools often function as “islands,” isolating students from nature, the community, and the “real world,” not preparing them to be well-informed and conscious citizens nor for the challenges that lie ahead. Some theoretical and practical alternatives are needed since schools actually embody the paradoxes and dilemmas of the current societal malaise but have not yet been able to deal with them or to provide adequate effective responses.

Islamic Theological Views on Darwinian Evolution

2016 ◽  
Author(s):  
Nidhal Guessoum
Keyword(s):  
Evolutionary Process ◽  
Darwinian Evolution ◽  
Theory Of Evolution ◽  
Human Exceptionalism ◽  
The World ◽  
The Problem Of Evil ◽  
History Of ◽  
Life On Earth ◽  
Biological Entities ◽  
Muslim Scholars

The various positions that Muslim scholars have adopted vis-à-vis Darwin’s theory of evolution since its inception in 1859 are here reviewed with an eye on the theological arguments that are embraced, whether explicitly or implicitly. A large spectrum of views and arguments are thus found, ranging from total rejection to total acceptance, including “human exceptionalism” (evolution is applicable to all organisms and animals but not to humans). The two main theological arguments that are thus extracted from Muslim scholars’ discussions of evolution are: 1) Is God excluded by the evolutionary paradigm or does the term “Creator” acquire a new definition? 2) Does Adam still exist in the human evolution scenario, and how to include his Qur’anic story in the scientific scenario? Additional, but less crucial issues are sometimes raised in Islamic discussions of evolution: a) Does the extinction of innumerable species during the history of life on earth conflict with the traditional view of God’s creation? b) Is theodicy (“the problem of evil”) exacerbated or explained by evolution? c) Are “species” well-defined and important biological entities in the Islamic worldview? d) Can the randomness that seems inherent in the evolutionary process be reconciled with a divine creation plan? These questions are here reviewed through the writings and arguments of Muslim scholars, and general conclusions are drawn about why rejectionists find it impossible to address those issues in a manner that is consistent with their religious principles and methods, and why more progressive, less literalistic scholars are able to fold those issues within a less rigid conception of God and the world.

scholarly journals Preface

1996 ◽  
Vol 351 (1345) ◽  
pp. 1227-1231 ◽  
Keyword(s):  
Natural Selection ◽  
20Th Century ◽  
Comparative Morphology ◽  
Biological Science ◽  
Selective Pressures ◽  
Evolutionary Pathways ◽  
Life On Earth ◽  
Diversity Of Life ◽  
Violent Conflicts

The great Darwinian truth that underlies our attempts to discover rhyme and reason in the diversity of life on Earth is that natural selection has shaped the form and behaviour of organisms. The search for the evolutionary pathways that lead to the present diversity of life, the study of phylogeny, was among the most powerful forces in the development of biological science in the latter part of the 19th and first half of the 20th century. It provided a fascinating intellectual exercise to draw out putative evolutionary sequences and gave the excuse for quite violent conflicts of interpretation. Comparative morphology was the main (and often the only) source of data for such phylogenetic speculation. It acknowledged that some features, ‘conservative characters’, were more resistant than others to evolutionary pressures and so were more reliable for tracing lineages. To establish phylogenies it became vitally important to identify these ‘conservative’ characters and to distinguish them from features that responded m ore quickly to selective pressures and therefore indicated only recent ancestry.

scholarly journals Linkage Relationships and Haplotype Polymorphism Among Cichlid Mhc Class II B Loci

Genetics ◽  
1998 ◽  
Vol 149 (3) ◽  
pp. 1527-1537
Author(s):  
Edward Málaga-Trillo ◽  
Zofia Zaleska-Rutczynska ◽  
Brendan McAndrew ◽  
Vladimir Vincek ◽  
Felipe Figueroa ◽  
...  
Keyword(s):  
Mhc Class Ii ◽  
Adaptive Radiation ◽  
Genetic System ◽  
Class Ii ◽  
East African ◽  
Cichlid Species ◽  
Definition Of ◽  
The Individual ◽  
Haploid Embryos ◽  
Species Flocks

Abstract The species flocks of cichlid fishes in the Great East African Lakes are paradigms of adaptive radiation and hence, of great interest to evolutionary biologists. Phylogenetic studies of these fishes have, however, been hampered by the lack of suitable polymorphic markers. The genes of the major histocompatibility complex hold the promise to provide, through their extensive polymorphism, a large number of such markers, but their use has been hampered by the complexity of the genetic system and the lack of definition of the individual loci. In this study we take the first substantial step to alleviate this problem. Using a combination of methods, including the typing of single sperm cells, gyno- or androgenetic individuals, and haploid embryos, as well as sequencing of class II B restriction fragments isolated from gels for Southern blots, we identify the previously characterized homology groups as distinct loci. At least 17 polymorphic class II B loci, all of which are presumably transcribed, have been found among the different species studied. Most of these loci are shared across the various cichlid species and genera. The number of loci per haplotype varies from individual to individual, ranging from 1 to 13. A total of 21 distinct haplotypes differing in the number of loci they carry has thus far been identified. All the polymorphic loci are part of the same cluster in which, however, distances between at least some of the loci (as indicated by recombination frequencies) are relatively large. Both the individual loci and the haplotypes can now be used to study phylogenetic relationships among the members of the species flocks and the mode in which speciation occurs during adaptive radiation.

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