ORCID Profile
0000-0002-0888-8193
Current Organisation
Universitat Konstanz
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Publisher: Oxford University Press (OUP)
Date: 15-10-2015
DOI: 10.1093/GBE/EVV200
Publisher: Wiley
Date: 26-09-2023
DOI: 10.1111/MEC.17143
Publisher: Wiley
Date: 08-05-2018
DOI: 10.1002/ECE3.4070
Publisher: Oxford University Press (OUP)
Date: 24-05-2019
DOI: 10.1093/GBE/EVZ108
Publisher: Springer Science and Business Media LLC
Date: 04-2013
DOI: 10.1038/NATURE12027
Publisher: Wiley
Date: 27-08-2012
DOI: 10.1111/J.1558-5646.2012.01755.X
Abstract: Volcanic crater lakes are isolated habitats that are particularly well suited to investigating ecological and evolutionary ergence and modes of speciation. However, the mode, frequency, and timing of colonization of crater lakes have been difficult to determine. We used a statistical comparative phylogeographic approach, based on a mitochondrialDNA dataset, to infer the colonization history of two Nicaraguan crater lakes by populations of genetically and ecologically ergent cichlid lineages: Midas (Amphilophus cf. citrinellus complex) and moga (Hypsophrys nematopus). We compared estimates of ersity among populations within the two cichlid lineages and found that Midas were the most genetically erse. From an approximate Bayesian computation analysis, we inferred that the crater lakes were each founded by both cichlid lineages in single waves of colonization: Masaya 5800 ± 300 years ago and Xiloá 5400 ± 750 years ago. We conclude that natural events are likely to have a dominant role in colonization of the crater lakes. Further, our findings suggest that the higher species richness and more rapid evolution of the Midas species complex, relative to other lineages of fishes in the same crater lakes, cannot be explained by earlier or more numerous colonization events.
Publisher: Springer Science and Business Media LLC
Date: 06-09-2016
DOI: 10.1038/NCOMMS12736
Abstract: Our understanding of how biological ersity arises is limited, especially in the case of speciation in the face of gene flow. Here we investigate the genomic basis of adaptive traits, focusing on a sympatrically erging species pair of crater lake cichlid fishes. We identify the main quantitative trait loci (QTL) for two eco-morphological traits: body shape and pharyngeal jaw morphology. These traits erge in parallel between benthic and limnetic species in the repeated adaptive radiations of this and other fish lineages. Remarkably, a single chromosomal region contains the highest effect size QTL for both traits. Transcriptomic data show that the QTL regions contain genes putatively under selection. Independent population genomic data corroborate QTL regions as areas of high differentiation between the sympatric sister species. Our results provide empirical support for current theoretical models that emphasize the importance of genetic linkage and pleiotropy in facilitating rapid ergence in sympatry.
Publisher: Cold Spring Harbor Laboratory
Date: 23-05-2020
DOI: 10.1101/2020.05.22.110833
Abstract: High-quality and complete reference genome assemblies are fundamental for the application of genomics to biology, disease, and bio ersity conservation. However, such assemblies are only available for a few non-microbial species 1–4 . To address this issue, the international Genome 10K (G10K) consortium 5,6 has worked over a five-year period to evaluate and develop cost-effective methods for assembling the most accurate and complete reference genomes to date. Here we summarize these developments, introduce a set of quality standards, and present lessons learned from sequencing and assembling 16 species representing major vertebrate lineages (mammals, birds, reptiles, hibians, teleost fishes and cartilaginous fishes). We confirm that long-read sequencing technologies are essential for maximizing genome quality and that unresolved complex repeats and haplotype heterozygosity are major sources of error in assemblies. Our new assemblies identify and correct substantial errors in some of the best historical reference genomes. Adopting these lessons, we have embarked on the Vertebrate Genomes Project (VGP), an effort to generate high-quality, complete reference genomes for all ~70,000 extant vertebrate species and help enable a new era of discovery across the life sciences.
Publisher: Wiley
Date: 16-12-2013
DOI: 10.1111/MEC.12590
Abstract: Determining the genetic bases of adaptations and their roles in speciation is a prominent issue in evolutionary biology. Cichlid fish species flocks are a prime ex le of recent rapid radiations, often associated with adaptive phenotypic ergence from a common ancestor within a short period of time. In several radiations of freshwater fishes, ergence in ecomorphological traits - including body shape, colour, lips and jaws - is thought to underlie their ecological differentiation, specialization and, ultimately, speciation. The Midas cichlid species complex (Amphilophus spp.) of Nicaragua provides one of the few known ex les of sympatric speciation where species have rapidly evolved different but parallel morphologies in young crater lakes. This study identified significant QTL for body shape using SNPs generated via ddRAD sequencing and geometric morphometric analyses of a cross between two ecologically and morphologically ergent, sympatric cichlid species endemic to crater Lake Apoyo: an elongated limnetic species (Amphilophus zaliosus) and a high-bodied benthic species (Amphilophus astorquii). A total of 453 genome-wide informative SNPs were identified in 240 F2 hybrids. These markers were used to construct a genetic map in which 25 linkage groups were resolved. Seventy-two segregating SNPs were linked to 11 QTL. By annotating the two most highly supported QTL-linked genomic regions, genes that might contribute to ergence in body shape along the benthic-limnetic axis in Midas cichlid sympatric adaptive radiations were identified. These results suggest that few genomic regions of large effect contribute to early stage ergence in Midas cichlids.
Publisher: Oxford University Press (OUP)
Date: 05-2016
DOI: 10.1093/GBE/EVW097
Publisher: American Association for the Advancement of Science (AAAS)
Date: 04-11-2016
Publisher: Springer Science and Business Media LLC
Date: 18-01-2018
DOI: 10.1038/S41598-018-19266-5
Abstract: Fine-scaled genetic structuring, as seen for ex le in many lacustrine fish, typically relates to the patterns of migration, habitat use, mating system or other ecological factors. Because the same processes can also affect the propensity of population differentiation and ergence, assessments of species from rapidly speciating clades, or with particularly interesting ecological traits, can be especially insightful. For this study, we assessed the spatial genetic relationships, including the genetic evidence for sex-biased dispersal, in a colony-breeding cichlid fish, Amphilophus astorquii , endemic to Crater Lake Apoyo in Nicaragua, using 11 polymorphic microsatellite loci (n = 123 in iduals from three colonies). We found no population structure in A . astorquii either within colonies (no spatial genetic autocorrelation, r ~0), or at the lake-wide level (pairwise population differentiation F ST = 0–0.013 and no clustering), and there was no sex-bias (male and female AIc values bounded 0) to this lack of genetic structure. These patterns may be driven by the colony-breeding reproductive behaviour of A . astorquii . The results suggest that strong philopatry or spatial assortative mating are unlikely to explain the rapid speciation processes associated with the history of this species in Lake Apoyo.
Publisher: Springer Science and Business Media LLC
Date: 26-05-2015
DOI: 10.1038/TP.2015.63
Abstract: Stress, particularly when experienced early in life, can have profound implications for mental health. Previous research covering various tissues such as the brain, suggests that the detrimental impact of early-life stress (ELS) on mental health is mediated via epigenetic modifications including DNA methylation. Genes of the hypothalamic–pituitary–adrenal axis—in particular, the glucocorticoid receptor ( hGR ) gene—stand out as key targets for ELS. Even though the link between hGR methylation and either ELS or psychopathology is fairly well established, the mutually dependent relationships between ELS, DNA methylation and psychopathology remain to be uncovered. The specific psychopathology an in idual might develop in the aftermath of stressful events can be highly variable, however, most studies investigating hGR methylation and psychopathology suffer from being limited to a single symptom cluster of mental disorders. Here, we screened volunteers for childhood maltreatment and analyzed whether it associates with hGR methylation in lymphocytes and a range of measures of psychological ill-health. hGR methylation in lymphocytes most likely reflects methylation patterns found in the brain and thus provides valuable insights into the etiology of psychopathology. We find the interaction between childhood maltreatment and hGR methylation to be strongly correlated with an increased vulnerability to psychopathology providing evidence of epigenome × environment interactions. Furthermore, our results indicate an additive effect of childhood maltreatment and hGR methylation in predicting borderline personality disorder (BPD)-associated symptoms, suggesting that the combination of both ELS and DNA methylation that possibly represents unfavorable events experienced even earlier in life poses the risk for BPD.
Publisher: Wiley
Date: 19-08-2013
DOI: 10.1111/MEC.12417
Abstract: Adaptive phenotypic plasticity, the ability of an organism to change its phenotype to match local environments, is increasingly recognized for its contribution to evolution. However, few empirical studies have explored the molecular basis of plastic traits. The East African cichlid fish Astatoreochromis alluaudi displays adaptive phenotypic plasticity in its pharyngeal jaw apparatus, a structure that is widely seen as an evolutionary key innovation that has contributed to the remarkable ersity of cichlid fishes. It has previously been shown that in response to different diets, the pharyngeal jaws change their size, shape and dentition: hard diets induce an adaptive robust molariform tooth phenotype with short jaws and strong internal bone structures, while soft diets induce a gracile papilliform tooth phenotype with elongated jaws and slender internal bone structures. To gain insight into the molecular underpinnings of these adaptations and enable future investigations of the role that phenotypic plasticity plays during the formation of adaptive radiations, the transcriptomes of the two ergent jaw phenotypes were examined. Our study identified a total of 187 genes whose expression differs in response to hard and soft diets, including immediate early genes, extracellular matrix genes and inflammatory factors. Transcriptome results are interpreted in light of expression of candidate genes-markers for tooth size and shape, bone cells and mechanically sensitive pathways. This study opens up new avenues of research at new levels of biological organization into the roles of phenotypic plasticity during speciation and radiation of cichlid fishes.
Publisher: Springer Science and Business Media LLC
Date: 26-01-2011
DOI: 10.1007/S00239-011-9431-X
Abstract: It has been suggested that speciation on the basis of sexual selection is an important mechanism for the generation of new species for East African cichlids, where male body coloration is one of the major discriminatory factors used by females in mate choice. To gain insight into the molecular basis of cichlid coloration, we studied the Lake Malawi cichlid Pseudotropheus saulosi, comparing transcription in the bright blue skin of males to the yellow skin of females. Our cDNA microarray experiments identified 46 clones that exhibited expression differences between the two sexes, of which five were confirmed to be differentially expressed by relative quantitative real-time PCR (qRT-PCR). This gene list includes a representative from the endosomal-to-Golgi vesicle trafficking pathway, Coatomer protein complex, subunit zeta-1 (Copz-1), which is known to be a critical determinant of pigmentation in humans and zebrafish. With the support of microscopic images of the skin of these specimens, we interpret the transcriptional differences between the blue males and yellow females. Here, we provide insight into the putative functional ersification of genes involved in the coloration of cichlids and by extension, on the evolution of coloration in teleost fish.
Publisher: Springer Science and Business Media LLC
Date: 14-12-2016
DOI: 10.1038/NATURE20595
Abstract: Seahorses have a specialized morphology that includes a toothless tubular mouth, a body covered with bony plates, a male brood pouch, and the absence of caudal and pelvic fins. Here we report the sequencing and de novo assembly of the genome of the tiger tail seahorse, Hippoc us comes . Comparative genomic analysis identifies higher protein and nucleotide evolutionary rates in H. comes compared with other teleost fish genomes. We identified an astacin metalloprotease gene family that has undergone expansion and is highly expressed in the male brood pouch. We also find that the H. comes genome lacks enamel matrix protein-coding proline/glutamine-rich secretory calcium-binding phosphoprotein genes, which might have led to the loss of mineralized teeth. tbx4 , a regulator of hindlimb development, is also not found in H. comes genome. Knockout of tbx4 in zebrafish showed a ‘pelvic fin-loss’ phenotype similar to that of seahorses.
Publisher: Wiley
Date: 30-01-2016
DOI: 10.1002/ECE3.1912
Publisher: Wiley
Date: 30-07-2014
DOI: 10.1111/MEC.12851
Abstract: Phenotypic plasticity is the ability of organisms with a given genotype to develop different phenotypes according to environmental stimuli, resulting in in iduals that are better adapted to local conditions. In spite of their ecological importance, the developmental regulatory networks underlying plastic phenotypes often remain uncharacterized. We examined the regulatory basis of diet-induced plasticity in the lower pharyngeal jaw (LPJ) of the cichlid fish Astatoreochromis alluaudi, a model species in the study of adaptive plasticity. Through raising juvenile A. alluaudi on either a hard or soft diet (hard-shelled or pulverized snails) for between 1 and 8 months, we gained insight into the temporal regulation of 19 previously identified candidate genes during the early stages of plasticity development. Plasticity in LPJ morphology was first detected between 3 and 5 months of diet treatment. The candidate genes, belonging to various functional categories, displayed dynamic expression patterns that consistently preceded the onset of morphological ergence and putatively contribute to the initiation of the plastic phenotypes. Within functional categories, we observed striking co-expression, and transcription factor binding site analysis was used to examine the prospective basis of their coregulation. We propose a regulatory network of LPJ plasticity in cichlids, presenting evidence for regulatory crosstalk between bone and muscle tissues, which putatively facilitates the development of this highly integrated trait. Through incorporating a developmental time-course into a phenotypic plasticity study, we have identified an interconnected, environmentally responsive regulatory network that shapes the development of plasticity in a key innovation of East African cichlids.
Publisher: Wiley
Date: 10-2009
Publisher: Springer Science and Business Media LLC
Date: 24-01-2013
Publisher: Springer Science and Business Media LLC
Date: 24-07-2017
DOI: 10.1038/S41559-017-0240-5
Abstract: Phylogenomics is extremely powerful but introduces new challenges as no agreement exists on "standards" for data selection, curation and tree inference. We use jawed vertebrates (Gnathostomata) as model to address these issues. Despite considerable efforts in resolving their evolutionary history and macroevolution, few studies have included a full phylogenetic ersity of gnathostomes and some relationships remain controversial. We tested a novel bioinformatic pipeline to assemble large and accurate phylogenomic datasets from RNA sequencing and find this phylotranscriptomic approach successful and highly cost-effective. Increased sequencing effort up to ca. 10Gbp allows recovering more genes, but shallower sequencing (1.5Gbp) is sufficient to obtain thousands of full-length orthologous transcripts. We reconstruct a robust and strongly supported timetree of jawed vertebrates using 7,189 nuclear genes from 100 taxa, including 23 new transcriptomes from previously uns led key species. Gene jackknifing of genomic data corroborates the robustness of our tree and allows calculating genome-wide ergence times by overcoming gene s ling bias. Mitochondrial genomes prove insufficient to resolve the deepest relationships because of limited signal and among-lineage rate heterogeneity. Our analyses emphasize the importance of large curated nuclear datasets to increase the accuracy of phylogenomics and provide a reference framework for the evolutionary history of jawed vertebrates.
Publisher: Springer Science and Business Media LLC
Date: 05-02-2014
Abstract: Heterochronic shifts during ontogeny can result in adaptively important innovations and might be initiated by simple developmental switches. Understanding the nature of these developmental events can provide insights into fundamental molecular mechanisms of evolutionary change. Fishes from the Suborder Belonoidei display a vast array of extreme craniofacial morphologies that appear to have arisen through a series of heterochronic shifts. We performed a molecular heterochrony study, comparing postembryonic jaw development in representatives of the Suborder Belonoidei, the halfbeak Dermogenys pusilla (where the lower jaw is considerably elongated compared to the upper jaw) and the needlefish Belone belone (where both jaws are elongated), to a representative of their sister group the Suborder Adrianichthyoidei, the medaka Oryzias latipes , which has retained the ancestral morphology. Early in development, the lower jaw displays accelerated growth both in needlefish and halfbeak compared to medaka, and secondary acceleration of the upper jaw is seen in needlefish later in their development, representing a case of mosaic heterochrony. We identified toothless extensions of the dentaries as innovations of Belonoid fishes and the source of heterochronic growth. The molecular basis of growth heterochronies in the Belonoidei was examined through comparing expression of skeletogenic genes during development of halfbeak and medaka. The calmodulin paralogue calm1 was identified as a potential regulator of jaw length in halfbeak as its expression gradually increases in the lower jaw, but not the upper jaw, in a pattern that matches its outgrowth. Moreover, medaka displays equal expression of calm1 in the upper and lower jaws, consistent with the lack of jaw outgrowth in this species. Heterochronic shifts in jaw growth have occurred repeatedly during the evolution of Belonoid fishes and we identify toothless extensions of the dentaries as an important innovation of this group. Our results suggest that calm1 contributes to jaw heterochrony in halfbeak, potentially driving further heterochronic shifts in jaw growth across the Suborder Belonoidei, such as the upper jaw acceleration observed in needlefish.
Publisher: Springer Science and Business Media LLC
Date: 28-04-2021
DOI: 10.1038/S41586-021-03451-0
Abstract: High-quality and complete reference genome assemblies are fundamental for the application of genomics to biology, disease, and bio ersity conservation. However, such assemblies are available for only a few non-microbial species 1–4 . To address this issue, the international Genome 10K (G10K) consortium 5,6 has worked over a five-year period to evaluate and develop cost-effective methods for assembling highly accurate and nearly complete reference genomes. Here we present lessons learned from generating assemblies for 16 species that represent six major vertebrate lineages. We confirm that long-read sequencing technologies are essential for maximizing genome quality, and that unresolved complex repeats and haplotype heterozygosity are major sources of assembly error when not handled correctly. Our assemblies correct substantial errors, add missing sequence in some of the best historical reference genomes, and reveal biological discoveries. These include the identification of many false gene duplications, increases in gene sizes, chromosome rearrangements that are specific to lineages, a repeated independent chromosome breakpoint in bat genomes, and a canonical GC-rich pattern in protein-coding genes and their regulatory regions. Adopting these lessons, we have embarked on the Vertebrate Genomes Project (VGP), an international effort to generate high-quality, complete reference genomes for all of the roughly 70,000 extant vertebrate species and to help to enable a new era of discovery across the life sciences.
Publisher: Elsevier BV
Date: 06-2010
DOI: 10.1016/J.BEPROC.2010.02.021
Abstract: Territorial animals are known to be able to differentiate between intruding in iduals posing a low or high threat and adjust their aggressive response accordingly. However, plastic territorial aggression based on recognising in iduals with different attributes is typically assumed to be relevant only in the context of conspecific interactions. In this study, we investigated territorial aggression of neotropical cichlid fish in their natural habitat to assess whether responses to different types of in iduals of another species can also be plastic. We show that arrow cichlids (Amphilophus zaliosus) adjusted their territorial aggression regarding the status of heterospecific intruders: breeding in iduals of Amphilophus astorquii received a lower level of aggression than non-breeders. The same pattern was also found for the two different types of A. astorquii in iduals intruding into conspecific territories. These results suggest that heterospecific in iduals should not be ignored when considering selection pressures shaping plasticity of aggressive behaviour in territorial animals.
Publisher: Wiley
Date: 10-2004
DOI: 10.1111/J.0014-3820.2004.TB01599.X
Abstract: This study aims at a better understanding of the evolutionary significance of viviparity in some freshwater gastropods. We use a phylogeny based on partial sequences of the mitochondrial 16S gene of representatives of the limnetic and pantropical Pachychilidae to infer the relationships within this particular group of cerithioideans and the evolution of reproductive strategies. The phylogeny presented herein implies a new systematization and suggests that viviparity has appeared three times among the Pachychilidae. This is supported by the finding of very distinct reproductive morphologies in different lineages of viviparous taxa that are exclusively found in Southeast Asia. Based on the observation that oviparity is the ancestral character state in this freshwater family, we conclude that viviparity has evolved subsequent to the exploration of freshwater. We present data showing that all Pachychilidae produce considerably larger but fewer egg capsules compared to most marine snails. In other studies on freshwater gastropods, this has been discussed as an adaptation to freshwater environments. In this context we hypothesize that the increased parental investment involved in the enlargement of eggs in concert with the reduction of clutch sizes was the driving factor that ultimately lead to the evolution of viviparity in the Asian taxa. Consequently, although not directly correlated with the colonization of the new adaptive zone, viviparity is strongly favored by other consequences of this step. Hence, we hypothesize that the production of large eggs, which is necessitated by the exploration of freshwater, represents a preadaptation existing in those ancestors from which viviparous pachychilid lineages eventually evolved in Southeast Asia.
Publisher: The Royal Society
Date: 05-01-2011
Abstract: Cichlid fishes are a textbook ex le of rapid speciation and exuberant ersity—this applies especially to haplochromines, a lineage with approximately 1800 species. Haplochromine males uniquely possess oval, bright spots on their anal fin, called ‘egg-spots’ or ‘egg-dummies’. These are presumed to be an evolutionary key innovation that contributed to the tribe's evolutionary success. Egg-spots have been proposed to mimic the ova of the mouthbrooding females of the corresponding species, contribute to fertilization success and even facilitate species recognition. Interestingly, egg-spot number varies extensively not only between species, but also within some populations. This high degree of intraspecific variation may appear to be counterintuitive since selection might be expected to act to stabilize traits that are correlated with fitness measures. We addressed this ‘paradox’ experimentally, and found that in the haplochromine cichlid Astatotilapia burtoni , the number of egg-spots was related to male age, body condition and dominance status. Intriguingly, the egg-spot number also had a high heritable component (narrow sense heritability of 0.5). These results suggest that the function of egg-spots might have less to do with fertilization success or species recognition, but rather relate to mate choice and/or male–male competition, helping to explain the high variability in this important trait.
Publisher: Oxford University Press (OUP)
Date: 23-03-2018
Publisher: Wiley
Date: 20-05-2016
DOI: 10.1002/ECE3.2184
Publisher: Elsevier BV
Date: 04-1996
Abstract: The subfamily of fishes Trematominae is endemic to the subzero waters of antarctica and is part of the longer notothenioid radiation. Partial mitochondrial sequences from the 12S and 16S ribosomal RNA (rRNA) genes and a phylogeny for 10 trematomid species are presented. As has been previously suggested, two taxa, Trematomus scotti and T. newnesi, do not appear to be part of the main trematomid radiation. The genus Pagothenia is nested within the genus Trematomus and has evolved a unique cyropelagic existence, an association with pack ice. Using a mitochondrial rRNA molecular clock rate of 0.14% transversion changes per million years, the average age of the trematomids is estimated at 3.4 million years (MY). If the age of the trematomids is approximately 3.4 MY, this group could have speciated during the period of deglaciation in Antarctica 2.5-4.8 million years ago. This era was marked by significant changes on the Antarctic shores, such as the opening of fjords, which might have provided a stimulus for specification.
Publisher: Springer Science and Business Media LLC
Date: 19-07-2011
DOI: 10.1038/TP.2011.21
Publisher: Oxford University Press (OUP)
Date: 09-08-2019
Abstract: Cichlid fishes provide textbook ex les of explosive phenotypic ersification and sympatric speciation, thereby making them ideal systems for studying the molecular mechanisms underlying rapid lineage ergence. Despite the fact that gene regulation provides a critical link between ersification in gene function and speciation, many genomic regulatory mechanisms such as microRNAs (miRNAs) have received little attention in these rapidly ersifying groups. Therefore, we investigated the posttranscriptional regulatory role of miRNAs in the repeated sympatric ergence of Midas cichlids (Amphilophus spp.) from Nicaraguan crater lakes. Using miRNA and mRNA sequencing of embryos from five Midas species, we first identified miRNA binding sites in mRNAs and highlighted the presences of a surprising number of novel miRNAs in these adaptively radiating species. Then, through analyses of expression levels, we identified putative miRNA/gene target pairs with negatively correlated expression level that were consistent with the role of miRNA in downregulating mRNA. Furthermore, we determined that several miRNA/gene pairs show convergent expression patterns associated with the repeated benthic/limnetic sympatric species ergence implicating these miRNAs as potential molecular mechanisms underlying replicated sympatric ergence. Finally, as these candidate miRNA/gene pairs may play a central role in phenotypic ersification in these cichlids, we characterized the expression domains of selected miRNAs and their target genes via in situ hybridization, providing further evidence that miRNA regulation likely plays a role in the Midas cichlid adaptive radiation. These results provide support for the hypothesis that extremely quickly evolving miRNA regulation can contribute to rapid evolutionary ergence even in the presence of gene flow.
Publisher: Springer Science and Business Media LLC
Date: 15-09-2011
Publisher: Public Library of Science (PLoS)
Date: 14-04-2014
Publisher: Springer Science and Business Media LLC
Date: 16-09-2011
Publisher: Public Library of Science (PLoS)
Date: 09-01-2012
Publisher: Springer Science and Business Media LLC
Date: 12-05-2010
Abstract: After a volcano erupts, a lake may form in the cooled crater and become an isolated aquatic ecosystem. This makes fishes in crater lakes informative for understanding sympatric evolution and ecological ersification in barren environments. From a geological and limnological perspective, such research offers insight about the process of crater lake ecosystem establishment and speciation. In the present study we use genetic and coalescence approaches to infer the colonization history of Midas cichlid fishes ( Amphilophus cf. citrinellus ) that inhabit a very young crater lake in Nicaragua-the ca . 1800 year-old Lake Apoyeque. This lake holds two sympatric, endemic morphs of Midas cichlid: one with large, hypertrophied lips (~20% of the total population) and another with thin lips. Here we test the associated ecological, morphological and genetic ersification of these two morphs and their potential to represent incipient speciation. Gene coalescence analyses [11 microsatellite loci and mitochondrial DNA (mtDNA) sequences] suggest that crater lake Apoyeque was colonized in a single event from the large neighbouring great lake Managua only about 100 years ago. This founding in historic times is also reflected in the extremely low nuclear and mitochondrial genetic ersity in Apoyeque. We found that sympatric adult thin- and thick-lipped fishes occupy distinct ecological trophic niches. Diet, body shape, head width, pharyngeal jaw size and shape and stable isotope values all differ significantly between the two lip-morphs. The eco-morphological features pharyngeal jaw shape, body shape, stomach contents and stable isotopes (δ 15 N) all show a bimodal distribution of traits, which is compatible with the expectations of an initial stage of ecological speciation under disruptive selection. Genetic differentiation between the thin- and thick-lipped population is weak at mtDNA sequence ( F ST = 0.018) and absent at nuclear microsatellite loci ( F ST 0.001). This study provides empirical evidence of eco-morphological differentiation occurring very quickly after the colonization of a new and vacant habitat. Exceptionally low levels of neutral genetic ersity and inference from coalescence indicates that the Midas cichlid population in Apoyeque is much younger ( ca . 100 years or generations old) than the crater itself ( ca . 1 800 years old). This suggests either that the crater remained empty for many hundreds of years after its formation or that remnant volcanic activity prevented the establishment of a stable fish population during the early life of the crater lake. Based on our findings of eco-morphological variation in the Apoyeque Midas cichlids, and known patterns of adaptation in Midas cichlids in general, we suggest that this population may be in a very early stage of speciation (incipient species), promoted by disruptive selection and ecological ersification.
Publisher: Wiley
Date: 06-01-2021
DOI: 10.1111/MEC.15774
Publisher: Springer Science and Business Media LLC
Date: 04-01-2011
Abstract: Cichlid fishes have undergone rapid, expansive evolutionary radiations that are manifested in the ersification of their trophic morphologies, tooth patterning and coloration. Understanding the molecular mechanisms that underlie the cichlids' unique patterns of evolution requires a thorough examination of genes that pattern the neural crest, from which these erse phenotypes are derived. Among those genes, the homeobox-containing Dlx gene family is of particular interest since it is involved in the patterning of the brain, jaws and teeth. In this study, we characterized the dlx genes of an African cichlid fish, Astatotilapia burtoni , to provide a baseline to later allow cross-species comparison within Cichlidae. We identified seven dlx paralogs ( dlx1a , -2a , -4a , -3b , -4b , -5a and -6a ), whose orthologies were validated with molecular phylogenetic trees. The intergenic regions of three dlx gene clusters ( dlx1a-2a , dlx3b-4b , and dlx5a-6a ) were lified with long PCR. Intensive cross-species comparison revealed a number of conserved non-coding elements (CNEs) that are shared with other percomorph fishes. This analysis highlighted additional lineage-specific gains/losses of CNEs in different teleost fish lineages and a novel CNE that had previously not been identified. Our gene expression analyses revealed overlapping but distinct expression of dlx orthologs in the developing brain and pharyngeal arches. Notably, four of the seven A. burtoni dlx genes, dlx2a , dlx3b , dlx4a and dlx5a , were expressed in the developing pharyngeal teeth. This comparative study of the dlx genes of A. burtoni has deepened our knowledge of the ersity of the Dlx gene family, in terms of gene repertoire, expression patterns and non-coding elements. We have identified possible cichlid lineage-specific changes, including losses of a subset of dlx expression domains in the pharyngeal teeth, which will be the targets of future functional studies.
Publisher: The Royal Society
Date: 12-06-2010
Abstract: The polychromatic and trophically polymorphic Midas cichlid fish species complex ( Amphilophus cf. citrinellus ) is an excellent model system for studying the mechanisms of speciation and patterns of phenotypic ersification in allopatry and in sympatry. Here, we first review research to date on the species complex and the geological history of its habitat. We analyse body shape variation from all currently described species in the complex, s led from six crater lakes (maximally 1.2–23.9 kyr old) and both great lakes in Nicaragua. We find that Midas cichlid populations in each lake have their own characteristic body shape. In lakes with multiple sympatric species of Midas cichlid, each species has a distinct body shape. Across the species complex, most body shape change relates to body depth, head, snout and mouth shape and caudal peduncle length. There is independent parallel evolution of an elongate limnetic species in at least two crater lakes. Mitochondrial genetic ersity is higher in crater lakes with multiple species. Midas cichlid species richness increases with the size and age of the crater lakes, though no such relationship exists for the other syntopic fishes. We suggest that crater lake Midas cichlids follow the predicted pattern of an adaptive radiation, with early ergence of each crater lake colonization, followed by intralacustrine ersification and speciation by ecological adaptation and sexual selection.
Publisher: Wiley
Date: 23-11-2017
DOI: 10.1111/MEC.14405
Abstract: Adaptive radiations are characterized by adaptive ersification intertwined with rapid speciation within a lineage resulting in many ecologically specialized, phenotypically erse species. It has been proposed that adaptive radiations can originate from ancestral lineages with pronounced phenotypic plasticity in adaptive traits, facilitating ecologically driven phenotypic ersification that is ultimately fixed through genetic assimilation of gene regulatory regions. This study aimed to investigate how phenotypic plasticity is reflected in gene expression patterns in the trophic apparatus of several lineages of East African cichlid fishes, and whether the observed patterns support genetic assimilation. This investigation used a split brood experimental design to compare adaptive plasticity in species from within and outside of adaptive radiations. The plastic response was induced in the crushing pharyngeal jaws through feeding in iduals either a hard or soft diet. We find that nonradiating, basal lineages show higher levels of adaptive morphological plasticity than the derived, radiated lineages, suggesting that these differences have become partially genetically fixed during the formation of the adaptive radiations. Two candidate genes that may have undergone genetic assimilation, gif and alas1, were identified, in addition to alterations in the wiring of LPJ patterning networks. Taken together, our results suggest that genetic assimilation may have d ened the inducibility of plasticity related genes during the adaptive radiations of East African cichlids, flattening the reaction norms and canalizing their feeding phenotypes, driving adaptation to progressively more narrow ecological niches.
Publisher: Wiley
Date: 30-06-2016
DOI: 10.1111/MEC.13699
Abstract: How polymorphisms consisting in left-right asymmetries are produced and maintained in natural populations is a tantalizing question, which remains largely unanswered. The scale-eating cichlid fish Perissodus microlepis is a remarkable ex le of extreme ecological specialization achieved by morphological and behavioural laterality. Its asymmetric mouth is accompanied by a pronounced lateralized foraging behaviour, where a left-bending morph preferentially feeds on the scales of the right side of its prey, while the opposite is true for the right morph. This striking asymmetry made this fish a textbook ex le of the astounding degree of ecological specialization and negative frequency-dependent selection. Yet, the genetic basis underlying this spectacular laterality remains unknown. We addressed this question through analyses of wild-caught fish using high-throughput DNA sequencing data. A novel array of SNP markers was developed by ddRAD sequencing (ddRADseq) and the use of pooled DNA s les (PoolSeq). We obtained more than 155 000 SNPs using ddRADseq and 3 900 000 SNPs with PoolSeq. Among these, we identified one (ddRAD) SNP, and 38 or 378 (PoolSeq) windows that are differentiated between the left and right morphs accounting for spurious associations due to geographic structuring. This allowed us to uncover candidate genomic regions that potentially contain genes for this trait. Then, this interesting trait has a genetic basis that is likely to be influenced by multiple loci. This result contributes to a greater understanding of the genetic bases of left-right asymmetry and, ultimately, the evolutionary processes governing the maintenance of this striking case of laterality.
Publisher: Wiley
Date: 10-02-2010
Publisher: Wiley
Date: 17-09-2016
DOI: 10.1002/ECE3.2396
Publisher: Public Library of Science (PLoS)
Date: 16-07-2013
Publisher: Springer Science and Business Media LLC
Date: 2008
DOI: 10.1186/JBIOL86
Location: United States of America
No related grants have been discovered for Axel Meyer.