Project

Back to overview

Unraveling the evolutionary origin and consequences of the largest known recent vertebrate radiation by a comprehensive analysis of complete cichlid genomes

English title Unraveling the evolutionary origin and consequences of the largest known recent vertebrate radiation by a comprehensive analysis of complete cichlid genomes
Applicant Seehausen Ole
Number 163338
Funding scheme Project funding (Div. I-III)
Research institution Institut für Ökologie und Evolution Universität Bern
Institution of higher education University of Berne - BE
Main discipline Zoology
Start/End 01.10.2016 - 30.09.2020
Approved amount 756'000.00
Show all

Keywords (5)

adaptive radiation; cichlid fish; speciation; phylogenomics; population genomics

Lay Summary (German)

Lead
Bei weitem die schnellste Rate von Artbildung wurde bei Buntbarschen im afrikanischen Viktoriasee nachgewiesen. Sie ermöglichte die Entstehung eines der artenreichsten Ökosysteme der Welt in nur wenigen zehntausend Jahren. Die genomischen Grundlagen dieser jungen Artenvielfalt sind noch nie vergleichend untersucht worden. Unser Projekt leistet dazu einen Beitrag.
Lay summary

Grosse Artenradiationen sind Ikonen der Evolutionsbiologie, besonders dann wenn sie in geologisch junger Zeit entstanden sind. Ihr Studium kann uns über das Entstehen und Vergehen von Artenvielfalt lehren, und darüber warum einige Tier- und Pflanzengruppen viel artenreicher werden als andere. Seitdem die Vorfahren der Viktoriabuntbarsche vor nur 15'000 Jahren in den sich damals gerade füllenden Viktoriasee einwanderten, entstanden 500 neue Arten mit den verschiedensten Erscheinungsbildern, Verhaltensweisen und ökologischen Anpassungen. Das ist die schnellste Artbildungsrate, die je bei Tieren festgestellt wurde, und lies eines der artenreichsten Ökosysteme der Erde entstehen.

Ziel unseres Projektes ist es, Veränderungen in den Genomen der Buntbarsche zu charakterisieren, die mit dieser Diversifizierung einhergingen. Wir sequenzieren die gesamten Genome von mehreren hundert Buntbarschen verschiedenster Arten. Wir sequenzieren aber auch die Arten, die wahrscheinlich die direkten Nachkommen der damaligen Einwanderer sind und heute noch unverändert in anderen Gewässern leben, sowie Buntbarsche anderer Evolutionslinien, die in sehr ähnlichen Lebensräumen leben ohne sich aber in neue Arten aufgespalten zu haben.

Wir möchten herausfinden, welche Gene für die Artbildung, und welche für ökologische Anpassungen verantwortlich sind, und wie diese im Genom gekoppelt werden, eine Voraussetzung für die Entstehung und Koexistenz von Arten. Wir möchten auch wissen, was der Ursprung der grossen genetischen Vielfalt ist. Waren die Vorfahren vielleicht bereits ungewöhnlich genetisch variabel und wie kam das? Könnte das Fehlen entsprechender Variation das Ausbleiben von Artbildung bei anderen Gruppen erklären? Wir rekonstruieren auch die zeitliche Abfolge der Geschehnisse in der Radiation um die Interaktion ökologischer und evolutionärer Mechanismen zu verstehen. Letztlich wird unser Projekt zu einem besseren Verständnis eines global einmaligen Biodiversitätshotspots beitragen.

Direct link to Lay Summary Last update: 19.08.2016

Responsible applicant and co-applicants

Employees

Associated projects

Number Title Start Funding scheme
183566 20,000 years of evolution and ecosystem dynamics in the world’s largest tropical lake reconstructed from sediment cores, fossils and ancient DNA 01.03.2019 Sinergia
134657 Population genomics of adaptive radiation 01.02.2012 ProDoc
144046 Measuring ecological and genetic constraints to speciation 01.07.2013 Project funding (Div. I-III)
144046 Measuring ecological and genetic constraints to speciation 01.07.2013 Project funding (Div. I-III)

Abstract

Large and rapid adaptive radiations are iconic textbook examples of evolution in action. When analyzed in an appropriate comparative context, they become powerful systems to investigate and identify causes of variation in rates and patterns of diversification among evolutionary lineages. When cichlid fishes colonized a newly refilled Lake Victoria 15,000 years ago, they diversified into more than 500 species. This is one of the fastest rates of speciation ever documented in animals. Learning how the genomes of these cichlids interacted with environmental and intrinsic drivers of evolution during this radiation will shed light on the evolution of species diversity in general. When compared to other taxa in similar environmental situations, it will also elucidate how constraints to diversification can be overcome. Together with colleagues, we have recently generated five fully annotated reference genomes of African cichlid fish, including one from Lake Victoria. We have also generated extensive population genomic data for several Lake Victoria cichlid species using reduced representation library sequencing methods, and most recently we have sequenced whole genomes of eight further species. In order to more fully understand both the evolutionary processes of species diversification and the genomic mechanisms underlying these processes, we now need whole genome sequence information from many species across the radiation. In this project we propose to reconstruct the evolutionary history of the Lake Victoria radiation by sequencing more than 120 of the 500 known species of Lake Victoria cichlids. We will also use genomic sequence data to reconstruct relationships for several small radiations in isolated lakes that were colonized either by populations descending from the same admixed ancestry as the Victoria radiation, or that descended from one of the lineages that admixed in the history of the Lake Victoria region superflock. Reconstructing the phylogenetic history of radiations in Lake Victoria and those in the smaller lakes will allow us to test important hypotheses about the dynamics of adaptive radiation, such as the temporal sequence in the origination of major ecotypic groups (the “stages of radiation” hypothesis), the extent of parallel speciation at different geographical and time scales, and will allow us, for the first time in a large recent cichlid radiation, to test for a slowdown in speciation and phenotypic evolution rates as would be predicted by ecological limits to evolving species richness. The comparison of radiations with different ancestries will then allow us to understand how a history of admixture has affected these dynamics and shaped the outcomes of cichlid radiation.Using population genomic analyses to infer species and clade-level demographic histories, we will infer demographic parameters for key phases in the radiations and for individual speciation events. We will use these inferences to test predictions made by alternative evolutionary models for speciation and adaptive radiation (speciation in sympatry versus intralacustrine allopatry, speciation in small populations with founder effects versus speciation in large populations, divergent selection, gene flow, hybrid speciation). We shall seek to characterize the genomic elements involved in speciation and post-speciation adaptive radiation in terms of genetic incompatibilities, adaptation-related and sexually selected genes. We will examine if the same elements are repeatedly involved in species differentiation, and at which level such parallelism occurs (SNP, gene, pathway). Finally, we will infer the sources of genetic variants from standing variation within one ancestral population, ancestral admixture between species, and de novo mutation within the radiation. We will use this data to test components of the hybrid swarm origin and syngameon hypotheses of adaptive radiation.
-