scholarly journals Comparing Adaptive Radiations Across Space, Time, and Taxa

2020 ◽  
Vol 111 (1) ◽  
pp. 1-20 ◽  
Author(s):  
Rosemary G Gillespie ◽  
Gordon M Bennett ◽  
Luc De Meester ◽  
Jeffrey L Feder ◽  
Robert C Fleischer ◽  
...  
Keyword(s):  
Reproductive Isolation ◽  
Adaptive Radiation ◽  
Related Species ◽  
Evolutionary Process ◽  
Ecological Opportunity ◽  
Ecological Selection ◽  
Adaptive Radiations ◽  
Ecological Shifts ◽  
Remote Islands ◽  
Rich Data

Abstract Adaptive radiation plays a fundamental role in our understanding of the evolutionary process. However, the concept has provoked strong and differing opinions concerning its definition and nature among researchers studying a wide diversity of systems. Here, we take a broad view of what constitutes an adaptive radiation, and seek to find commonalities among disparate examples, ranging from plants to invertebrate and vertebrate animals, and remote islands to lakes and continents, to better understand processes shared across adaptive radiations. We surveyed many groups to evaluate factors considered important in a large variety of species radiations. In each of these studies, ecological opportunity of some form is identified as a prerequisite for adaptive radiation. However, evolvability, which can be enhanced by hybridization between distantly related species, may play a role in seeding entire radiations. Within radiations, the processes that lead to speciation depend largely on (1) whether the primary drivers of ecological shifts are (a) external to the membership of the radiation itself (mostly divergent or disruptive ecological selection) or (b) due to competition within the radiation membership (interactions among members) subsequent to reproductive isolation in similar environments, and (2) the extent and timing of admixture. These differences translate into different patterns of species accumulation and subsequent patterns of diversity across an adaptive radiation. Adaptive radiations occur in an extraordinary diversity of different ways, and continue to provide rich data for a better understanding of the diversification of life.

scholarly journals Iterative adaptive radiations of fossil canids show no evidence for diversity-dependent trait evolution

2015 ◽  
Vol 112 (16) ◽  
pp. 4897-4902 ◽  
Author(s):  
Graham J. Slater
Keyword(s):  
Adaptive Radiation ◽  
Morphological Evolution ◽  
Empirical Support ◽  
Phenotypic Evolution ◽  
Ecological Opportunity ◽  
Radiation Theory ◽  
Molar Teeth ◽  
Adaptive Radiations ◽  
Adaptive Peak ◽  
Adaptive Zone

A long-standing hypothesis in adaptive radiation theory is that ecological opportunity constrains rates of phenotypic evolution, generating a burst of morphological disparity early in clade history. Empirical support for the early burst model is rare in comparative data, however. One possible reason for this lack of support is that most phylogenetic tests have focused on extant clades, neglecting information from fossil taxa. Here, I test for the expected signature of adaptive radiation using the outstanding 40-My fossil record of North American canids. Models implying time- and diversity-dependent rates of morphological evolution are strongly rejected for two ecologically important traits, body size and grinding area of the molar teeth. Instead, Ornstein–Uhlenbeck processes implying repeated, and sometimes rapid, attraction to distinct dietary adaptive peaks receive substantial support. Diversity-dependent rates of morphological evolution seem uncommon in clades, such as canids, that exhibit a pattern of replicated adaptive radiation. Instead, these clades might best be thought of as deterministic radiations in constrained Simpsonian subzones of a major adaptive zone. Support for adaptive peak models may be diagnostic of subzonal radiations. It remains to be seen whether early burst or ecological opportunity models can explain broader adaptive radiations, such as the evolution of higher taxa.

scholarly journals The coincidence of ecological opportunity with hybridization explains rapid adaptive radiation in Lake Mweru cichlid fishes

2019 ◽  
Vol 10 (1) ◽  
Author(s):  
Joana I. Meier ◽  
Rike B. Stelkens ◽  
Domino A. Joyce ◽  
Salome Mwaiko ◽  
Numel Phiri ◽  
...  
Keyword(s):  
Genetic Variation ◽  
Gene Flow ◽  
Great Lakes ◽  
Adaptive Radiation ◽  
Ecological Opportunity ◽  
African Great Lakes ◽  
Cichlid Fishes ◽  
Haplochromine Cichlid ◽  
Genetic Potential ◽  
Adaptive Radiations

AbstractThe process of adaptive radiation was classically hypothesized to require isolation of a lineage from its source (no gene flow) and from related species (no competition). Alternatively, hybridization between species may generate genetic variation that facilitates adaptive radiation. Here we study haplochromine cichlid assemblages in two African Great Lakes to test these hypotheses. Greater biotic isolation (fewer lineages) predicts fewer constraints by competition and hence more ecological opportunity in Lake Bangweulu, whereas opportunity for hybridization predicts increased genetic potential in Lake Mweru. In Lake Bangweulu, we find no evidence for hybridization but also no adaptive radiation. We show that the Bangweulu lineages also colonized Lake Mweru, where they hybridized with Congolese lineages and then underwent multiple adaptive radiations that are strikingly complementary in ecology and morphology. Our data suggest that the presence of several related lineages does not necessarily prevent adaptive radiation, although it constrains the trajectories of morphological diversification. It might instead facilitate adaptive radiation when hybridization generates genetic variation, without which radiation may start much later, progress more slowly or never occur.

scholarly journals Comparative analyses for adaptive radiations

2000 ◽  
Vol 355 (1403) ◽  
pp. 1599-1605 ◽  
Author(s):  
Paul H. Harvey ◽  
Andrew Rambaut
Keyword(s):  
Brownian Motion ◽  
Adaptive Radiation ◽  
Related Species ◽  
Character Evolution ◽  
Motion Model ◽  
Closely Related Species ◽  
Branch Lengths ◽  
Character Variation ◽  
Brownian Motion Model ◽  
Adaptive Radiations

Biologists generally agree that most morphological variation between closely related species is adaptive. The most common method of comparative analysis to test for co–evolved character variation is based on a Brownian–motion model of character evolution. If we are to test for the evolution of character covariation, and we believe that characters have evolved adaptively to fill niches during an adaptive radiation, then it is appropriate to employ appropriate models for character evolution. We show here that under several models of adaptive character evolution and coevolution during an adaptive radiation, which result in closely related species being more similar to each other than to more distantly related species, cross–species analyses are statistically more appropriate than contrast analyses. If the evolution of some traits fits the Brownian–motion model, while others evolve to fill niches during an adaptive radiation, it might be necessary to identify the number of relevant niche dimensions and the modes of character evolution before deciding on appropriate statistical procedures. Alternatively, maximum–likelihood procedures might be used to determine appropriate transformations of phylogenetic branch lengths that accord with particular models of character evolution.

scholarly journals Reinforcement and the Proliferation of Species

2019 ◽  
Vol 111 (1) ◽  
pp. 138-146 ◽  
Author(s):  
Gina M Calabrese ◽  
Karin S Pfennig
Keyword(s):  
Reproductive Isolation ◽  
Adaptive Radiation ◽  
Downstream Effects ◽  
Adaptive Radiations ◽  
Ideal Framework ◽  
Empirical Approaches

Abstract Adaptive radiations are characterized by the rapid proliferation of species. Explaining how adaptive radiations occur therefore depends, in part, on identifying how populations become reproductively isolated—and ultimately become different species. Such reproductive isolation could arise when populations adapting to novel niches experience selection to avoid interbreeding and, consequently, evolve mating traits that minimize such hybridization via the process of reinforcement. Here, we highlight that a downstream consequence of reinforcement is divergence of conspecific populations, and this further divergence can instigate species proliferation. Moreover, we evaluate when reinforcement will—and will not—promote species proliferation. Finally, we discuss empirical approaches to test what role, if any, reinforcement plays in species proliferation and, consequently, in adaptive radiation. To date, reinforcement’s downstream effects on species proliferation remain largely unknown and speculative. Because the ecological and evolutionary contexts in which adaptive radiations occur are conducive to reinforcement and its downstream consequences, adaptive radiations provide an ideal framework in which to evaluate reinforcement’s role in diversification.

Selection on old variants drives adaptive radiation of Metrosideros across the Hawaiian Islands

2020 ◽  
Author(s):  
Jae Young Choi ◽  
Xiaoguang Dai ◽  
Julie Z. Peng ◽  
Priyesh Rughani ◽  
Scott Hickey ◽  
...  
Keyword(s):  
Adaptive Radiation ◽  
Recurrent Selection ◽  
Balancing Selection ◽  
Hawaiian Islands ◽  
Ecological Niches ◽  
Gene Pools ◽  
Ecological Diversity ◽  
Founder Populations ◽  
Adaptive Radiations ◽  
Remote Islands

AbstractSome of the most spectacular adaptive radiations begin with founder populations on remote islands. How genetically limited founder populations give rise to the striking phenotypic and ecological diversity characteristic of adaptive radiations is a paradox of evolutionary biology. We conducted an evolutionary genomic analysis of genus Metrosideros, a landscape-dominant, incipient adaptive radiation of woody plants that spans a striking range of phenotypes and environments across the Hawaiian Islands. Using nanopore-sequencing, we created a chromosome-level genome assembly for M. polymorpha var. incana and analyzed wholegenome sequences of 131 individuals from 11 taxa sampled across the islands. We found evidence of population structure that grouped taxa by island. Demographic modeling showed concordance between the divergence times of island-specific lineages and the geological formation of individual islands. Gene flow was also detected within and between island taxa, suggesting a complex reticulated evolutionary history. We investigated genomic regions with increased differentiation as these regions may harbor variants involved in local adaptation or reproductive isolation, thus forming the genomic basis of adaptive radiation. We discovered differentiation outliers have arisen from balancing selection on ancient divergent haplotypes that formed before the initial colonization of the archipelago. These regions experienced recurrent divergent selection as lineages colonized and diversified on new islands, and hybridization likely facilitated the transfer of these ancient variants between taxa. Balancing selection on multiple ancient haplotypes–or time-tested variants–may help to explain how lineages with limited gene pools can rapidly diversify to fill myriad ecological niches on remote islands.Significance statementSome of the most spectacular adaptive radiations of plants and animals occur on remote oceanic islands, yet such radiations are preceded by founding events that severely limit genetic variation. How genetically depauperate founder populations give rise to the spectacular phenotypic and ecological diversity characteristic of island adaptive radiations is not known. We generated novel genomic resources for Hawaiian Metrosideros––a hyper-variable incipient adaptive radiation of woody taxa—for insights into the paradox of remote island radiations. We found that Metrosideros colonized each island shortly after formation and diversified within islands through recurrent selection on ancient variations that predate the radiation. Recurring use of ancient variants may explain how genetically depauperate lineages can diversify to fill countless niches on remote islands.

scholarly journals The propagation of admixture-derived adaptive radiation potential

2020 ◽  
Vol 287 (1934) ◽  
pp. 20200941
Author(s):  
Kotaro Kagawa ◽  
Ole Seehausen
Keyword(s):  
Genetic Variation ◽  
Genetic Polymorphisms ◽  
Computer Simulations ◽  
Adaptive Radiation ◽  
Hybrid Population ◽  
Ecological Opportunity ◽  
Time Points ◽  
Hybridization Event ◽  
Short Period ◽  
Adaptive Radiations

Adaptive radiations (ARs) frequently show remarkable repeatability where single lineages undergo multiple independent episodes of AR in distant places and long-separate time points. Genetic variation generated through hybridization between distantly related lineages can promote AR. This mechanism, however, requires rare coincidence in space and time between a hybridization event and opening of ecological opportunity, because hybridization generates large genetic variation only locally and it will persist only for a short period. Hence, hybridization seems unlikely to explain recurrent AR in the same lineage. Contrary to these expectations, our evolutionary computer simulations demonstrate that admixture variation can geographically spread and persist for long periods if the hybrid population becomes separated into isolated sub-lineages. Subsequent secondary hybridization of some of these can reestablish genetic polymorphisms from the ancestral hybridization in places far from the birthplace of the hybrid clade and long after the ancestral hybridization event. Consequently, simulations revealed conditions where exceptional genetic variation, once generated through a rare hybridization event, can facilitate multiple ARs exploiting ecological opportunities available at distant points in time and space.

scholarly journals Continental cichlid radiations: functional diversity reveals the role of changing ecological opportunity in the Neotropics

2016 ◽  
Vol 283 (1836) ◽  
pp. 20160556 ◽  
Author(s):  
Jessica Hilary Arbour ◽  
Hernán López-Fernández
Keyword(s):  
Central America ◽  
Adaptive Radiation ◽  
Morphological Diversity ◽  
Evolutionary Rates ◽  
Ecological Niches ◽  
Ecological Opportunity ◽  
Ecological Release ◽  
Adaptive Radiations ◽  
Lineage Diversification

Adaptive radiations have been hypothesized to contribute broadly to the diversity of organisms. Models of adaptive radiation predict that ecological opportunity and ecological release, the availability of empty ecological niches and the response by adapting lineages to occupy them, respectively, drive patterns of phenotypic and lineage diversification. Adaptive radiations driven by ‘ecological opportunity’ are well established in island systems; it is less clear if ecological opportunity influences continent-wide diversification. We use Neotropical cichlid fishes to test if variation in rates of functional evolution is consistent with changing ecological opportunity. Across a functional morphological axis associated with ram–suction feeding traits, evolutionary rates declined through time as lineages diversified in South America. Evolutionary rates of ram–suction functional morphology also appear to have accelerated as cichlids colonized Central America and encountered renewed opportunity. Our results suggest that ecological opportunity may play an important role in shaping patterns of morphological diversity of even broadly distributed lineages like Neotropical cichlids.

scholarly journals Adaptive radiation and hybridization in Wallace's Dreamponds: evidence from sailfin silversides in the Malili Lakes of Sulawesi

2006 ◽  
Vol 273 (1598) ◽  
pp. 2209-2217 ◽  
Author(s):  
Fabian Herder ◽  
Arne W Nolte ◽  
Jobst Pfaender ◽  
Julia Schwarzer ◽  
Renny K Hadiaty ◽  
...  
Keyword(s):  
New Species ◽  
Adaptive Radiation ◽  
Introgressive Hybridization ◽  
Reticulate Evolution ◽  
Species Group ◽  
Potential Force ◽  
Major Interest ◽  
Key Factor ◽  
Adaptive Radiations ◽  
Malili Lakes

Adaptive radiations are extremely useful to understand factors driving speciation. A challenge in speciation research is to distinguish forces creating novelties and those relevant to divergence and adaptation. Recently, hybridization has regained major interest as a potential force leading to functional novelty and to the genesis of new species. Here, we show that introgressive hybridization is a prominent phenomenon in the radiation of sailfin silversides (Teleostei: Atheriniformes: Telmatherinidae) inhabiting the ancient Malili Lakes of Sulawesi, correlating conspicuously with patterns of increased diversity. We found the most diverse lacustrine species-group of the radiation to be heavily introgressed by genotypes originating from streams of the lake system, an effect that has masked the primary phylogenetic pattern of the flock. We conclude that hybridization could have acted as a key factor in the generation of the flock's spectacular diversity. To our knowledge, this is the first empirical evidence for massive reticulate evolution within a complex animal radiation.

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