1
|
Hu F, Fan J, Qin Q, Huo Y, Wang Y, Wu C, Liu Q, Li W, Chen X, Liu C, Tao M, Wang S, Zhao R, Luo K, Liu S. The Sterility of Allotriploid Fish and Fertility of Female Autotriploid Fish. Front Genet 2019; 10:377. [PMID: 31105746 PMCID: PMC6498098 DOI: 10.3389/fgene.2019.00377] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2018] [Accepted: 04/09/2019] [Indexed: 11/29/2022] Open
Abstract
Based on the formation of an autotetraploid fish line (4nAUT, 4n = 200; F2-F11) derived from the distant hybridization of female Carassius auratus red var. (RCC, 2n = 100) × male Megalobrama amblycephala (BSB, 2n = 48), we produced autotriploid hybrids (3nAUT) by crossing females of RCC with males of 4nAUT and allotriploid hybrids (3nALT) by crossing females of Cyprinus carpio (CC, 2n = 100) with males of 4nAUT. The aim of this study was to comparatively investigate the reproductive characteristics of 3nALT and 3nAUT. We investigated morphological traits, chromosomal numbers, DNA content and gonadal development in 3nAUT and 3nALT. The results indicated both 3nAUT and 3nALT possessed 150 chromosomes and were triploid hybrids. The females and males of 3nALT and males of 3nAUT had abnormal gonadal development and could not generate mature eggs or sperm, but the females of 3nAUT had normal gonadal development and generated mature eggs at 2 years old. The females of 3nAUT generated different sizes of eggs, which fertilized with haploid sperm from RCC and formed viable diploid, triploid, and tetraploid offspring. The formation of these two kinds of triploid hybrids provides an ideal model for studying the reproductive traits of triploid hybrids, which is of great value in animal genetics and reproductive biology.
Collapse
Affiliation(s)
| | | | | | | | | | | | | | | | | | | | | | | | | | | | - Shaojun Liu
- State Key Laboratory of Developmental Biology of Freshwater Fish, College of Life Science, Hunan Normal University, Changsha, China
| |
Collapse
|
2
|
Motazedi E, Finkers R, Maliepaard C, de Ridder D. Exploiting next-generation sequencing to solve the haplotyping puzzle in polyploids: a simulation study. Brief Bioinform 2019; 19:387-403. [PMID: 28065918 DOI: 10.1093/bib/bbw126] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2016] [Indexed: 11/12/2022] Open
Abstract
Haplotypes are the units of inheritance in an organism, and many genetic analyses depend on their precise determination. Methods for haplotyping single individuals use the phasing information available in next-generation sequencing reads, by matching overlapping single-nucleotide polymorphisms while penalizing post hoc nucleotide corrections made. Haplotyping diploids is relatively easy, but the complexity of the problem increases drastically for polyploid genomes, which are found in both model organisms and in economically relevant plant and animal species. Although a number of tools are available for haplotyping polyploids, the effects of the genomic makeup and the sequencing strategy followed on the accuracy of these methods have hitherto not been thoroughly evaluated.We developed the simulation pipeline haplosim to evaluate the performance of three haplotype estimation algorithms for polyploids: HapCompass, HapTree and SDhaP, in settings varying in sequencing approach, ploidy levels and genomic diversity, using tetraploid potato as the model. Our results show that sequencing depth is the major determinant of haplotype estimation quality, that 1 kb PacBio circular consensus sequencing reads and Illumina reads with large insert-sizes are competitive and that all methods fail to produce good haplotypes when ploidy levels increase. Comparing the three methods, HapTree produces the most accurate estimates, but also consumes the most resources. There is clearly room for improvement in polyploid haplotyping algorithms.
Collapse
Affiliation(s)
- Ehsan Motazedi
- Bioinformatics Group, Wageningen University and Research, The Netherlands.,Wageningen UR Plant Breeding, The Netherlands
| | | | | | - Dick de Ridder
- Bioinformatics Group, Wageningen University and Research, The Netherlands
| |
Collapse
|
3
|
Ren L, Tang C, Li W, Cui J, Tan X, Xiong Y, Chen J, Wang J, Xiao J, Zhou Y, Wang J, Tao M, Zhang C, Liu S. Determination of dosage compensation and comparison of gene expression in a triploid hybrid fish. BMC Genomics 2017; 18:38. [PMID: 28056785 PMCID: PMC5216571 DOI: 10.1186/s12864-016-3424-5] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2015] [Accepted: 12/14/2016] [Indexed: 12/15/2022] Open
Abstract
Background Polyploidy and hybridization are both recognized as major forces in evolution. Most of our current knowledge about differences in gene regulation in polyploid hybrids comes from plant studies. The gene expression of diverged genomes and regulatory interactions are still unclear in lower vertebrates. Results We generated 229 million cleaned reads (42.23 Gbp) from triploid of maternal grass carp (Ctenopharyngodon idellus, Cyprininae, 2n = 48) × paternal blunt snout bream (Megalobrama amblycephala, Cultrinae, 2n = 48) and their diploid parents using next-generation sequencing. In total, 157,878 contigs were assembled and 15,444 genes were annotated. We examined gene expression level changes among the parents and their triploid offspring. The mechanisms of dosage compensation that reduced triploid expression levels to the diploid state were determined in triploid fish. In this situation, novel gene expression and gene silencing were observed. Then, we established a model to determine the extent and direction of expression level dominance (ELD) and homoeolog expression bias (HEB) based on the relative expression level among the parents and their triploid offspring. Conclusions Our results showed that the genome-wide ELD was biased toward maternal genome in triploid. Extensive alterations in homoeolog expression suggested a combination of regulatory and epigenetic interactions through the transcriptome network. Additionally, the expression patterns of growth genes provided insights into the relationship between the characteristics of growth and underlying mechanisms in triploids. Regulation patterns of triploid state suggest that various expression levels from the initial genomic merger have important roles in adaptation. Electronic supplementary material The online version of this article (doi:10.1186/s12864-016-3424-5) contains supplementary material, which is available to authorized users.
Collapse
Affiliation(s)
- Li Ren
- State Key Laboratory of Developmental Biology of Freshwater Fish, Hunan Normal University, Changsha, 410081, China
| | - Chenchen Tang
- State Key Laboratory of Developmental Biology of Freshwater Fish, Hunan Normal University, Changsha, 410081, China
| | - Wuhui Li
- State Key Laboratory of Developmental Biology of Freshwater Fish, Hunan Normal University, Changsha, 410081, China
| | - Jialin Cui
- State Key Laboratory of Developmental Biology of Freshwater Fish, Hunan Normal University, Changsha, 410081, China
| | - Xingjun Tan
- State Key Laboratory of Developmental Biology of Freshwater Fish, Hunan Normal University, Changsha, 410081, China
| | - Yafeng Xiong
- State Key Laboratory of Developmental Biology of Freshwater Fish, Hunan Normal University, Changsha, 410081, China
| | - Jie Chen
- State Key Laboratory of Developmental Biology of Freshwater Fish, Hunan Normal University, Changsha, 410081, China
| | - Jun Wang
- State Key Laboratory of Developmental Biology of Freshwater Fish, Hunan Normal University, Changsha, 410081, China
| | - Jun Xiao
- State Key Laboratory of Developmental Biology of Freshwater Fish, Hunan Normal University, Changsha, 410081, China
| | - Yi Zhou
- State Key Laboratory of Developmental Biology of Freshwater Fish, Hunan Normal University, Changsha, 410081, China
| | - Jing Wang
- State Key Laboratory of Developmental Biology of Freshwater Fish, Hunan Normal University, Changsha, 410081, China
| | - Min Tao
- State Key Laboratory of Developmental Biology of Freshwater Fish, Hunan Normal University, Changsha, 410081, China
| | - Chun Zhang
- State Key Laboratory of Developmental Biology of Freshwater Fish, Hunan Normal University, Changsha, 410081, China
| | - Shaojun Liu
- State Key Laboratory of Developmental Biology of Freshwater Fish, Hunan Normal University, Changsha, 410081, China.
| |
Collapse
|
4
|
Morgan-Richards M, Hills SFK, Biggs PJ, Trewick SA. Sticky Genomes: Using NGS Evidence to Test Hybrid Speciation Hypotheses. PLoS One 2016; 11:e0154911. [PMID: 27187689 PMCID: PMC4871368 DOI: 10.1371/journal.pone.0154911] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2016] [Accepted: 04/21/2016] [Indexed: 12/30/2022] Open
Abstract
Hypotheses of hybrid origin are common. Here we use next generation sequencing to test a hybrid hypothesis for a non-model insect with a large genome. We compared a putative hybrid triploid stick insect species (Acanthoxyla geisovii) with its putative paternal diploid taxon (Clitarchus hookeri), a relationship that provides clear predictions for the relative genetic diversity within each genome. The parental taxon is expected to have comparatively low allelic diversity that is nested within the diversity of the hybrid daughter genome. The scale of genome sequencing required was conveniently achieved by extracting mRNA and sequencing cDNA to examine expressed allelic diversity. This allowed us to test hybrid-progenitor relationships among non-model organisms with large genomes and different ploidy levels. Examination of thousands of independent loci avoids potential problems produced by the silencing of parts of one or other of the parental genomes, a phenomenon sometimes associated with the process of stabilisation of a hybrid genome. Transcript assembles were assessed for evidence of paralogs and/or alternative splice variants before proceeding. Comparison of transcript assemblies was not an appropriate measure of genetic variability, but by mapping reads back to clusters derived from each species we determined levels of allelic diversity. We found greater cDNA sequence diversity among alleles in the putative hybrid species (Acanthoxyla geisovii) than the non-hybrid. The allelic diversity within the putative paternal species (Clitachus hookeri) nested within the hybrid-daughter genome, supports the current view of a hybrid-progenitor relationship for these stick insect species. Next generation sequencing technology provides opportunities for testing evolutionary hypotheses with non-model organisms, including, as here, genomes that are large due to polyploidy.
Collapse
Affiliation(s)
- Mary Morgan-Richards
- Ecology Group, Institute of Agriculture and Environment, Massey University, Palmerston North, New Zealand
- * E-mail:
| | - Simon F. K. Hills
- Ecology Group, Institute of Agriculture and Environment, Massey University, Palmerston North, New Zealand
| | - Patrick J. Biggs
- Infectious Disease Research Centre, Institute of Veterinary, Animal & Biomedical Sciences, Massey University, Palmerston North, New Zealand
| | - Steven A. Trewick
- Ecology Group, Institute of Agriculture and Environment, Massey University, Palmerston North, New Zealand
| |
Collapse
|
5
|
Hoffmann A, Plötner J, Pruvost NBM, Christiansen DG, Röthlisberger S, Choleva L, Mikulíček P, Cogălniceanu D, Sas-Kovács I, Shabanov D, Morozov-Leonov S, Reyer HU. Genetic diversity and distribution patterns of diploid and polyploid hybrid water frog populations (Pelophylax esculentus complex) across Europe. Mol Ecol 2015; 24:4371-91. [PMID: 26308154 DOI: 10.1111/mec.13325] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2014] [Revised: 07/09/2015] [Accepted: 07/10/2015] [Indexed: 11/29/2022]
Abstract
Polyploidization is a rare yet sometimes successful way for animals to rapidly create geno- and phenotypes that may colonize new habitats and quickly adapt to environmental changes. In this study, we use water frogs of the Pelophylax esculentus complex, comprising two species (Pelophylax lessonae, genotype LL; Pelophylax ridibundus, RR) and various diploid (LR) and triploid (LLR, LRR) hybrid forms, summarized as P. esculentus, as a model for studying recent hybridization and polyploidization in the context of speciation. Specifically, we compared the geographic distribution and genetic diversity of diploid and triploid hybrids across Europe to understand their origin, maintenance and potential role in hybrid speciation. We found that different hybrid and parental genotypes are not evenly distributed across Europe. Rather, their genetic diversity is structured by latitude and longitude and the presence/absence of parental species but not of triploids. Highest genetic diversity was observed in central and eastern Europe, the lowest in the northwestern parts of Europe. This gradient can be explained by the decrease in genetic diversity during postglacial expansion from southeastern glacial refuge areas. Genealogical relationships calculated on the basis of microsatellite data clearly indicate that hybrids are of multiple origin and include a huge variety of parental genomes. Water frogs in mixed-ploidy populations without any parental species (i.e. all-hybrid populations) can be viewed as evolutionary units that may be on their way towards hybrid speciation. Maintenance of such all-hybrid populations requires a continuous exchange of genomes between diploids and triploids, but scenarios for alternative evolutionary trajectories are discussed.
Collapse
Affiliation(s)
- Alexandra Hoffmann
- Institute of Evolutionary Biology and Environmental Studies, University of Zurich, Winterthurerstrasse 190, Zurich, CH-8057, Switzerland
| | - Jörg Plötner
- Museum für Naturkunde, Leibniz Institute for Evolution and Biodiversity Science, Invalidenstraße 43, Berlin, 10115, Germany
| | - Nicolas B M Pruvost
- Institute of Evolutionary Biology and Environmental Studies, University of Zurich, Winterthurerstrasse 190, Zurich, CH-8057, Switzerland
| | - Ditte G Christiansen
- Institute of Evolutionary Biology and Environmental Studies, University of Zurich, Winterthurerstrasse 190, Zurich, CH-8057, Switzerland
| | - Sandra Röthlisberger
- Institute of Evolutionary Biology and Environmental Studies, University of Zurich, Winterthurerstrasse 190, Zurich, CH-8057, Switzerland
| | - Lukáš Choleva
- Laboratory of Fish Genetics, Institute of Animal Physiology and Genetics, AS CR, v.v.i., Rumburská 89, Liběchov, 277 21, Czech Republic.,Department of Biology and Ecology, Faculty of Science, University of Ostrava, Chittussiho 10, Ostrava, 710 00, Czech Republic
| | - Peter Mikulíček
- Department of Zoology, Faculty of Natural Sciences, Comenius University in Bratislava, Mlynska dolina B-1, Bratislava, SK-84215, Slovak Republic
| | - Dan Cogălniceanu
- Faculty of Natural Sciences and Agricultural Sciences, University Ovidius Constanţa, Al. Universităţii 1, corp B, Constanţa, Romania
| | - István Sas-Kovács
- Department of Biology, Faculty of Sciences, University of Oradea, Universitatii str. 1, Oradea, 410087, Romania
| | - Dmitry Shabanov
- Karazin Kharkiv National University, Svobody sq 4, Kharkiv, 62077, Ukraine
| | - Svyatoslav Morozov-Leonov
- Department of Evolutionary Genetic Basics of Systematics, Schmalhausen Institute of Zoology, B. Khmelnitskogo st., 15 Kyiv-30, Kyiv, MSP UA-01601, Ukraine
| | - Heinz-Ulrich Reyer
- Institute of Evolutionary Biology and Environmental Studies, University of Zurich, Winterthurerstrasse 190, Zurich, CH-8057, Switzerland
| |
Collapse
|
6
|
Reyer HU, Arioli-Jakob C, Arioli M. Post-zygotic selection against parental genotypes during larval development maintains all-hybrid populations of the frog Pelophylax esculentus. BMC Evol Biol 2015; 15:131. [PMID: 26141702 PMCID: PMC4491251 DOI: 10.1186/s12862-015-0404-3] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2015] [Accepted: 06/02/2015] [Indexed: 11/10/2022] Open
Abstract
Background Hybridization between two species usually leads to inviable or infertile offspring, due to endogenous or exogenous selection pressures. Yet, hybrid taxa are found in several plant and animal genera, and some of these hybrid taxa are ecologically and evolutionarily very successful. One example of such a successful hybrid is the water frog, Pelophylax esculentus which originated from matings between the two species P. ridibundus (genotype RR) and P. lessonae (LL). At the northern border of the distribution all-hybrid populations consisting of diploid (LR) and one or two triploid (LLR, LRR) frog types have been established. Here, the hybrid has achieved reproductive independence from its sexual ancestors and forms a self-sustaining evolutionary unit. Based on the gamete production of these hybrids, certain mating combinations should lead to LL and RR offspring, but these parental forms are absent among the adults. Results In order to investigate the mechanisms that maintain such an all-hybrid system, we performed a field study and a crossing experiment. In the field we sampled several ponds for water frog larvae at different developmental stages. Genotype compositions were then analysed and life-history differences between the genotypes examined. In the experiment we crossed diploid and triploid males and females from different ponds and determined fertilization success as well as development speed and survival rates of the offspring under high, medium and low food availability. In both parts of the study, we found numerous LL and RR offspring during the egg and early larval stages; but the frequency of these parental genotypes decreased drastically during later stages. In natural ponds almost all of them had disappeared already before metamorphosis; under the more benign experimental conditions the last ones died as juveniles during the following year. Conclusions From the combined results we conclude that the absence of parental genotypes in all-hybrid populations is due to post-zygotic selection against them, rather than to pre-zygotic mechanisms that might prevent their formation in the first place. For this post-zygotic selection, genetic mechanisms resulting from low genetic diversity and fixation of deleterious mutations seem to be a more likely explanation than ecological factors.
Collapse
Affiliation(s)
- Heinz-Ulrich Reyer
- Institute of Evolutionary Biology and Environmental Studies, University of Zürich, Winterthurerstrasse 190, Zürich, CH-8057, Switzerland.
| | - Christian Arioli-Jakob
- Institute of Evolutionary Biology and Environmental Studies, University of Zürich, Winterthurerstrasse 190, Zürich, CH-8057, Switzerland.
| | - Martina Arioli
- Institute of Evolutionary Biology and Environmental Studies, University of Zürich, Winterthurerstrasse 190, Zürich, CH-8057, Switzerland.
| |
Collapse
|
7
|
Alam MS, Islam MM, Khan MR, Hasan M, Wanichanon R, Sumida M. Postmating Isolation in Six Species of Three Genera (Hoplobatrachus, EuphlyctisandFejervarya) from Family Dicroglossidae (Anura), with Special Reference to Spontaneous Production of Allotriploids. Zoolog Sci 2012; 29:743-52. [DOI: 10.2108/zsj.29.743] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
|
8
|
Jakovlić I, Gui JF. Recent invasion and low level of divergence between diploid and triploid forms of Carassius auratus complex in Croatia. Genetica 2011; 139:789-804. [PMID: 21644055 DOI: 10.1007/s10709-011-9584-y] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2010] [Accepted: 05/23/2011] [Indexed: 10/18/2022]
Abstract
Carassius auratus is an invasive species in European waters, comprising a complex of diploid and polyploid forms with different modes of reproduction. However, the evolutionary history and relationships between the diploids and polyploids are still unresolved. In this study, 51.5% diploids and 48.5% triploids, including four triploid males, were discovered among the 363 individuals sampled in Croatia. We used eight microsatellite loci and mitochondrial displacement loop sequences to analyze the structure and origin of populations; and to attempt to infer the evolutionary history of the two different forms in Croatia. Microsatellite analyses revealed high allelic and clonal diversity, corroborating that high propagule vectors can compensate for the negative effects of genetic bottlenecks in successful invasive species. The absence of significant population structuring confirmed recent origin and rapid spreading of populations. No evidence was found for the existence of native European populations. Distances between individuals using both nuclear and mtDNA markers revealed the absence of substantial clustering on the ploidy level, while the split between the different ploidies on population level was only partial, suggesting that the reproductive isolation between the two forms is either of a very recent origin, or that there exists uni-, or bidirectional gene flow between the diploid and triploid forms.
Collapse
Affiliation(s)
- Ivan Jakovlić
- State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences, Graduate School of the Chinese Academy of Sciences, 430072 Wuhan, People's Republic of China
| | | |
Collapse
|
9
|
Gui J, Zhou L. Genetic basis and breeding application of clonal diversity and dual reproduction modes in polyploid Carassius auratus gibelio. SCIENCE CHINA-LIFE SCIENCES 2010; 53:409-15. [PMID: 20596906 DOI: 10.1007/s11427-010-0092-6] [Citation(s) in RCA: 138] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/12/2009] [Accepted: 12/02/2009] [Indexed: 01/17/2023]
Abstract
A unisexual species is generally associated with polyploidy, and reproduced by a unisexual reproduction mode, such as gynogenesis, hybridogenesis or parthenogenesis. Compared with other unisexual and polyploid species, gibel carp (Carassius auratus gibelio) has a higher ploidy level of hexaploid. It has undergone several successive rounds of genome polyploidy, and experienced an additional, more recent genome duplication event. More significantly, the dual reproduction modes, including gynogenesis and sexual reproduction, have been demonstrated to coexist in the polyploid gibel carp. This article reviews the genetic basis concerning polyploidy origin, clonal diversity and dual reproduction modes, and outlines the progress in new variety breeding and gene identification involved in the reproduction and early development. The data suggests that gibel carp are under an evolutionary trajectory of diploidization. As a novel evolutionary developmental (Evo-Devo) biology model, this work highlights future perspectives about the functional divergence of duplicated genes and the sexual origin of vertebrate animals.
Collapse
Affiliation(s)
- JianFang Gui
- State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan 430072, China.
| | | |
Collapse
|
10
|
Arioli M, Jakob C, Reyer HU. Genetic diversity in water frog hybrids (Pelophylax esculentus) varies with population structure and geographic location. Mol Ecol 2010; 19:1814-28. [PMID: 20374490 DOI: 10.1111/j.1365-294x.2010.04603.x] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Pelophylax esculentus is a hybridogenetic frog originating from matings between P. ridibundus (RR) and P. lessonae (LL). Typically, diploid hybrids (LR) live in sympatry with one of their parental species, upon which they depend for successful reproduction. In parts of their range, however, pure hybrid populations can be found. These hybrid populations have achieved reproductive independence from their parental species by using triploid hybrids (LLR, LRR) rather than LL and RR as their sexual hosts. These different breeding systems also entail differences in reproduction (clonal versus sexual) and hence offer the opportunity to study how genetic diversity is affected by reproductive mode, population structure and geographic location. We investigated 33 populations in the Scania region (South Sweden) and 18 additional populations from Northern and Central Europe. Within both genomes (L, R), genetic variability increases with the potential for recombination and declines from the main species distribution area southeast of the Baltic Sea to the fringe populations northwest of the Baltic Sea. Within the main study area in Scania, genetic diversity is low and decreases from a core area to the periphery. Genetic differentiation between Scania populations is small but significant and best explained by 'isolation by distance'. Despite the low genetic variability within the discrete genomes, all-hybrid P. esculentus populations in southern Sweden are apparently not suffering from direct negative fitness effects. This is probably because of its somatic hybrid status, which increases diversity through the combination of genomes from two species.
Collapse
Affiliation(s)
- Martina Arioli
- Institute for Evolutionary Biology and Environmental Studies, University of Zurich, Winterthurerstrasse 190, CH-8057, Zurich, Switzerland
| | | | | |
Collapse
|
11
|
Abstract
Species are generally considered to be the basic units of evolution, and hence to constitute spatio-temporally bounded entities. In addition, it has been argued that species also instantiate a natural kind. Evolution is fundamentally about change. The question then is how species can remain the same through evolutionary change. Proponents of the species qua individuals thesis individuate species through their unique evolutionary origin. Individuals, or spatio-temporally located particulars in general, can be bodies, objects, events, or processes, or a combination of these. It is here argued that species are best understood as open or closed, causally integrated processual systems that also instantiate an historically conditioned homeostatic property cluster natural kind.
Collapse
Affiliation(s)
- Olivier Rieppel
- Department of Geology, The Field Museum, 1400 S Lake Shore Drive, Chicago, IL 60605-2496, USA.
| |
Collapse
|
12
|
|
13
|
Sousa-Santos C, Collares-Pereira MJ, Almada V. Fertile triploid males: an uncommon case among hybrid vertebrates. ACTA ACUST UNITED AC 2007; 307:220-5. [PMID: 17351916 DOI: 10.1002/jez.363] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
The endemic Iberian minnow Squalius alburnoides is a complex of fishes of hybrid origin including both males and females with distinct ploidy levels and varying proportions of the parental genomes. In this paper we demonstrated that in contrast to many vertebrate hybrid lineages the sperm of triploid hybrid males of S. alburnoides is viable and fully functional. Flow cytometry and analysis of sequences of a fragment of the beta-actin nuclear gene applied to progenitors and offspring evidenced that these males produced their sperm clonally, as already described for diploid hybrids. The presence of different types of fertile males (nonhybrid diploids with normal meiosis and both diploid and triploid hybrids) coupled with hybridogenetic meiosis in females endows this vertebrate complex with a high level of independence from other species and contributes to maintain its genetic variability.
Collapse
Affiliation(s)
- Carla Sousa-Santos
- Instituto Superior de Psicologia Aplicada, Unidade de Investigação em Eco-Etologia, Lisboa, Portugal.
| | | | | |
Collapse
|