1
|
Dehling JM, Sinsch U. Amphibians of Rwanda: Diversity, Community Features, and Conservation Status. DIVERSITY 2023. [DOI: 10.3390/d15040512] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/05/2023]
Abstract
The diversity and distribution of the amphibians in Rwanda was critically reviewed to provide a reliable species inventory for informed conservation management. The checklist of the amphibian species of Rwanda is based on results of our own fieldwork, historical records compiled from the literature, and examination of voucher specimens in museum collections. A total of 62 species are recorded, and 22 further species listed in field guides and open-access data bases are discussed, identified as erroneous records, and consequently not included in the country list. We provide diagnostic characters of external morphology and the advertisement call for each validated species, and a short synopsis of geographic distribution, altitudinal range, occurrence in the provinces of Rwanda, and habitat preference. We provide keys to all genera, and all taxonomically described species based on morphological characters and additional keys based on features of the advertisement calls. We discuss features of amphibian communities including local community structure and delimitation of altitudinal metacommunities. Based on the IUCN red list assessment and our field surveys, we propose for the first time a national red list of amphibians in Rwanda.
Collapse
Affiliation(s)
- J. Maximilian Dehling
- Department of Biology, Institute of Integrated Natural Sciences, University of Koblenz, D-56070 Koblenz, Germany
| | - Ulrich Sinsch
- Department of Biology, Institute of Integrated Natural Sciences, University of Koblenz, D-56070 Koblenz, Germany
| |
Collapse
|
2
|
Elepfandt A, Gutsche A, Fischer WJ, Leujak W, Bishop PJ. Long-term field study of the behaviour of Xenopus laevis (Pipidae) in a small dam. AFR J HERPETOL 2022. [DOI: 10.1080/21564574.2021.1998234] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Affiliation(s)
| | - Alexander Gutsche
- Humboldt-Universität zu Berlin, Inst. Biologie, Berlin, Germany
- Current address: Museum für Naturkunde, Berlin, Germany
| | - Werner J Fischer
- Universität Konstanz, Fak. Biologie, Konstanz, Germany
- Current address: F. Hoffmann-La Roche Ltd, Basel, Switzerland
| | - Wera Leujak
- Humboldt-Universität zu Berlin, Inst. Biologie, Berlin, Germany
- Current address: Umweltbundesamt (UBA), Dessau-Roßlau, Germany
| | - Phillip J Bishop
- University of the Witwatersrand, Department of Zoology, Johannesburg, South Africa
- Last address: University of Otago, Department of Zoology, Dunedin, New Zealand
- Dedicated to the late Phillip J Bishop
| |
Collapse
|
3
|
Heterogeneity of synonymous substitution rates in the Xenopus frog genome. PLoS One 2020; 15:e0236515. [PMID: 32764757 PMCID: PMC7413554 DOI: 10.1371/journal.pone.0236515] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2020] [Accepted: 07/07/2020] [Indexed: 11/19/2022] Open
Abstract
With the increasing availability of high quality genomic data, there is opportunity to deeply explore the genealogical relationships of different gene loci between closely related species. In this study, we utilized genomes of Xenopus laevis (XLA, a tetraploid species with (L) and (S) sub-genomes) and X. tropicalis (XTR, a diploid species) to investigate whether synonymous substitution rates among orthologous or homoeologous genes displayed any heterogeneity. From over 1500 orthologous/homoeologous genes collected, we calculated proportion of synonymous substitutions between genomes/sub-genomes (k) and found variation within and between chromosomes. Within most chromosomes, we identified higher k with distance from the centromere, likely attributed to higher substitution rates and recombination in these regions. Using maximum likelihood methods, we identified further evidence supporting rate heterogeneity, and estimated species divergence times and ancestral population sizes. Estimated species divergence times (XLA.L-XLA.S: ~25.5 mya; XLA-XTR: ~33.0 mya) were slightly younger compared to a past study, attributed to consideration of population size in our study. Meanwhile, we found very large estimated population size in the ancestral populations of the two species (NA = 2.55 x 106). Local hybridization and population structure, which have not yet been well elucidated in frogs, may be a contributing factor to these possible large population sizes.
Collapse
|
4
|
Ringeis A, Krumscheid B, Bishop PJ, de Vries C, Elepfandt A. Acoustic communication and reproductive behaviour in the aquatic frog Xenopus laevis (Pipidae), a field study. AFR J HERPETOL 2017. [DOI: 10.1080/21564574.2017.1381649] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Affiliation(s)
- Achim Ringeis
- Universität Konstanz, Fak. Biologie, Konstanz, Germany
| | | | | | | | - Andreas Elepfandt
- Universität Konstanz, Fak. Biologie, Konstanz, Germany
- Humboldt-Universität zu Berlin, Inst. Biologie, Berlin, Germany
| |
Collapse
|
5
|
Limited genomic consequences of hybridization between two African clawed frogs, Xenopus gilli and X. laevis (Anura: Pipidae). Sci Rep 2017; 7:1091. [PMID: 28439068 PMCID: PMC5430669 DOI: 10.1038/s41598-017-01104-9] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2016] [Accepted: 03/13/2017] [Indexed: 11/15/2022] Open
Abstract
The Cape platanna, Xenopus gilli, an endangered frog, hybridizes with the African clawed frog, X. laevis, in South Africa. Estimates of the extent of gene flow between these species range from pervasive to rare. Efforts have been made in the last 30 years to minimize hybridization between these two species in the west population of X. gilli, but not the east populations. To further explore the impact of hybridization and the efforts to minimize it, we examined molecular variation in one mitochondrial and 13 nuclear genes in genetic samples collected recently (2013) and also over two decades ago (1994). Despite the presence of F1 hybrids, none of the genomic regions we surveyed had evidence of gene flow between these species, indicating a lack of extensive introgression. Additionally we found no significant effect of sampling time on genetic diversity of populations of each species. Thus, we speculate that F1 hybrids have low fitness and are not backcrossing with the parental species to an appreciable degree. Within X. gilli, evidence for gene flow was recovered between eastern and western populations, a finding that has implications for conservation management of this species and its threatened habitat.
Collapse
|
6
|
Evans BJ, Carter TF, Greenbaum E, Gvoždík V, Kelley DB, McLaughlin PJ, Pauwels OSG, Portik DM, Stanley EL, Tinsley RC, Tobias ML, Blackburn DC. Genetics, Morphology, Advertisement Calls, and Historical Records Distinguish Six New Polyploid Species of African Clawed Frog (Xenopus, Pipidae) from West and Central Africa. PLoS One 2015; 10:e0142823. [PMID: 26672747 PMCID: PMC4682732 DOI: 10.1371/journal.pone.0142823] [Citation(s) in RCA: 63] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2015] [Accepted: 10/27/2015] [Indexed: 01/08/2023] Open
Abstract
African clawed frogs, genus Xenopus, are extraordinary among vertebrates in the diversity of their polyploid species and the high number of independent polyploidization events that occurred during their diversification. Here we update current understanding of the evolutionary history of this group and describe six new species from west and central sub-Saharan Africa, including four tetraploids and two dodecaploids. We provide information on molecular variation, morphology, karyotypes, vocalizations, and estimated geographic ranges, which support the distinctiveness of these new species. We resurrect Xenopus calcaratus from synonymy of Xenopus tropicalis and refer populations from Bioko Island and coastal Cameroon (near Mt. Cameroon) to this species. To facilitate comparisons to the new species, we also provide comments on the type specimens, morphology, and distributions of X. epitropicalis, X. tropicalis, and X. fraseri. This includes significantly restricted application of the names X. fraseri and X. epitropicalis, the first of which we argue is known definitively only from type specimens and possibly one other specimen. Inferring the evolutionary histories of these new species allows refinement of species groups within Xenopus and leads to our recognition of two subgenera (Xenopus and Silurana) and three species groups within the subgenus Xenopus (amieti, laevis, and muelleri species groups).
Collapse
Affiliation(s)
- Ben J. Evans
- Department of Biology, Life Sciences Building Room 328 McMaster University, Hamilton, Ontario, Canada
- * E-mail:
| | - Timothy F. Carter
- Biomedical Sciences, Ontario Veterinary College, University of Guelph, Guelph, Ontario, Canada
| | - Eli Greenbaum
- Department of Biological Sciences, University of Texas at El Paso, El Paso, Texas, United States of America
| | - Václav Gvoždík
- Institute of Vertebrate Biology, Czech Academy of Sciences, Kvetna 8, Brno, Czech Republic
- Department of Zoology, National Museum, Prague, Czech Republic
| | - Darcy B. Kelley
- Department of Biological Sciences, Columbia University, New York, New York, United States of America
| | - Patrick J. McLaughlin
- Department of Biology, Papadakis Integrated Sciences Building, Drexel University, Philadelphia, Pennsylvania, United States of America
| | - Olivier S. G. Pauwels
- Département des Vertébrés Récents, Instítut Royal des Sciences Naturelles de Belgique, Brussels, Belgium
| | - Daniel M. Portik
- Museum of Vertebrate Zoology, University of California, Berkeley, California, United States of America
| | - Edward L. Stanley
- California Academy of Sciences, San Francisco, California, United States of America
| | - Richard C. Tinsley
- School of Biological Sciences, University of Bristol, Bristol, United Kingdom
| | | | - David C. Blackburn
- California Academy of Sciences, San Francisco, California, United States of America
| |
Collapse
|
7
|
Mechkarska M, Prajeep M, Leprince J, Vaudry H, Meetani MA, Evans BJ, Conlon JM. A comparison of host-defense peptides in skin secretions of female Xenopus laevis × Xenopus borealis and X. borealis × X. laevis F1 hybrids. Peptides 2013; 45:1-8. [PMID: 23624316 DOI: 10.1016/j.peptides.2013.04.008] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/07/2013] [Revised: 04/15/2013] [Accepted: 04/17/2013] [Indexed: 12/30/2022]
Abstract
Peptidomic analysis was used to compare the diversity of host-defense peptides in norepinephrine-stimulated skin secretions from laboratory-generated female F1 hybrids of Xenopus laevis and Xenopus borealis (Pipidae). Skin secretions of hybrids with maternal X. laevis (XLB) contained 12 antimicrobial peptides (AMPs), comprising 8 from X. laevis and 4 from X. borealis. Magainin-B1, XPF-B1, PGLa-B1 CPF-B2, CPF-B3 and CPF-B4 from X. borealis and XPF-1, XPF-2, and CPF-6 from X. laevis were not detected and CPF-1 and CPF-7 were present in low concentration. The secretions contained caerulein and caerulein-B1 derived from both parents but lacked X. laevis xenopsin and X. borealis caerulein-B2. Skin secretions of hybrids with maternal X. borealis (XBL) contained 14 AMPs comprising 6 from X. borealis and 8 from X. laevis. Magainin-B1, XPF-B1, PGLa-B1, CPF-B2, XPF-1, CPF-5, and CPF-7 were absent and CPF-B3, CPF-B4, CPF-1 and CPF-6 were present only in low concentration. Xenopsin and caerulein were identified in the secretions but caerulein-B2 was absent and caerulein-B1 was present in low concentration. No peptides were identified in secretions of either XLB or XBL hybrids that were not present in the parental species. The data indicate that hybridization between X. laevis and X. borealis results in increased diversity of host-defense peptides in skin secretions but point to extensive AMP gene silencing compared with previously studied female X. laevis×X. muelleri F1 hybrids and no novel peptide expression.
Collapse
Affiliation(s)
- Milena Mechkarska
- Department of Biochemistry, College of Medicine and Health Sciences, United Arab Emirates University, Al Ain, United Arab Emirates
| | | | | | | | | | | | | |
Collapse
|
8
|
Mechkarska M, Meetani M, Michalak P, Vaksman Z, Takada K, Conlon JM. Hybridization between the African clawed frogs Xenopus laevis and Xenopus muelleri (Pipidae) increases the multiplicity of antimicrobial peptides in skin secretions of female offspring. COMPARATIVE BIOCHEMISTRY AND PHYSIOLOGY D-GENOMICS & PROTEOMICS 2012; 7:285-91. [PMID: 22687652 DOI: 10.1016/j.cbd.2012.05.002] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/01/2012] [Revised: 05/20/2012] [Accepted: 05/20/2012] [Indexed: 01/08/2023]
Abstract
Peptidomic analysis was used to compare the distribution of host-defense peptides in norepinephrine-stimulated skin secretions from laboratory-generated female F1 hybrids of the common clawed frog Xenopus laevis (Daudin, 1802) and Mueller's clawed frog Xenopus muelleri (Peters, 1844) with the corresponding distribution in skin secretions from the parent species. A total of 18 peptides were identified in secretions from the hybrid frogs. Eleven peptides (magainin-1, magainin-2, CPF-1, CPF-3, CPF-4, CPF-5, CPF-6, CPF-7, XPF-1, XPF-2, and PGLa) were identified in secretions of both the hybrids and X. laevis. Four peptides (magainin-M1, XPF-M1, CPF-M1, and tigerinin-M1) were previously found in skin secretions of X. muelleri but magainin-M2 and CPF-M2 from X. muelleri were not detected. Three previously undescribed peptides (magainin-LM1, PGLa-LM1, and CPF-LM1) were purified from the secretions of the hybrid frogs that were not detected in secretions from either X. laevis or X. muelleri. Magainin-LM1 differs from magainin-2 from X. laevis by a single amino acid substitution (Gly(13)→Ala) but PGLa-LM1 and CPF-LM1 differ appreciably in structure from orthologs in the parent species. CPF-LM1 shows potent, broad-spectrum antimicrobial activity and is hemolytic. The data indicate that hybridization increases the multiplicity of skin host-defense peptides in skin secretions. As the female F1 hybrids are fertile, hybridization may represent an adaptive strategy among Xenopus species to increase protection against pathogenic microorganisms in the environment.
Collapse
Affiliation(s)
- Milena Mechkarska
- Department of Biochemistry, Faculty of Medicine and Health Sciences, United Arab Emirates University, 17666 Al-Ain, United Arab Emirates
| | | | | | | | | | | |
Collapse
|
9
|
Madison-Villar MJ, Michalak P. Misexpression of testicular microRNA in sterile Xenopus hybrids points to tetrapod-specific microRNAs associated with male fertility. J Mol Evol 2011; 73:316-24. [PMID: 22207500 DOI: 10.1007/s00239-011-9478-8] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2011] [Accepted: 12/02/2011] [Indexed: 10/14/2022]
Abstract
Spermatogenesis is one of the most complex biological processes undergone by any organism, making it susceptible to perturbations that result in male sterility. Research has demonstrated that mutant phenotypes can be obtained from the disruption of epigenetic modifications, which are commonly microRNA guided. Employing the Xenopus system, whereby homogametic interspecies males are always sterile, thus violating Haldane's Rule, we deep-sequenced testes-specific small-RNAs to identify microRNAs most frequently misexpressed between sterile hybrids and their fertile parental taxa. Using these data, we cross-referenced our expression information with previously published mouse (Mus musculus) data and identified a subset of seven microRNAs common to both (miR-338, miR-222, miR-18, miR-30, miR-10, miR-196, and miR-365). We propose that these microRNAs are likely critical for spermatogenesis in all tetrapods, having retained testicular expression across ~350 million years of evolution (Amphibian-Mammal split). Gene targets of six of these microRNAs are known, and all the six associate with zinc and zinc finger proteins (both previously found critical in male fertility), and three with Hox genes (some of which have also previously been deemed critical for testicular development and male fertility). Expression information for these targets revealed that all those associated with zinc have previously been found to express in mammalian testes. One Hox target has known mammalian testicular expression, two have close relatives with known mammalian testicular expression, and two more are associated with proteins known to have mammalian testicular expression. In addition, miR-222 has prior association with spermatogenesis, and miR-30 has been found to be abundantly expressed in both mouse and human testes.
Collapse
|
10
|
Mechkarska M, Ahmed E, Coquet L, Leprince J, Jouenne T, Vaudry H, King JD, Conlon JM. Peptidomic analysis of skin secretions demonstrates that the allopatric populations of Xenopus muelleri (Pipidae) are not conspecific. Peptides 2011; 32:1502-8. [PMID: 21664395 DOI: 10.1016/j.peptides.2011.05.025] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/26/2011] [Revised: 05/25/2011] [Accepted: 05/25/2011] [Indexed: 01/20/2023]
Abstract
Mueller's clawed frog Xenopus muelleri (Peters 1844) occupies two non-contiguous ranges in east and west Africa. The phylogenetic relationship between the two populations is unclear and it has been proposed that the western population represents a separate species. Peptidomic analysis of norepinephrine-stimulated skin secretions from X. muelleri from the eastern range resulted in the identification of five antimicrobial peptides structurally related to the magainins (magainin-M1 and -M2), xenopsin-precursor fragments (XPF-M1) and caerulein-precursor fragments (CPF-M1 and -M2) previously found in skin secretions of other Xenopus species. A cyclic peptide (WCPPMIPLCSRF.NH₂) containing the RFamide motif was also isolated that shows limited structural similarity to the tigerinins, previously identified only in frogs of the Dicroglossidae family. The components identified in skin secretions from X. muelleri from the western range comprised one magainin (magainin-MW1), one XPF peptide (XPF-MW1), two peptides glycine-leucine amide (PGLa-MW1 and -MW2), and three CPF peptides (CPF-MW1, -MW2 and -MW3). Comparison of the primary structures of these peptides suggest that western population of X. muelleri is more closely related to X. borealis than to X. muelleri consistent with its proposed designation as a separate species. The CPF peptides showed potent, broad-spectrum activity against reference strains of bacteria (MIC 3-25 μM), but were hemolytic against human erythrocytes.
Collapse
Affiliation(s)
- Milena Mechkarska
- Department of Biochemistry, Faculty of Medicine and Health Sciences, United Arab Emirates University, 17666 Al-Ain, United Arab Emirates
| | | | | | | | | | | | | | | |
Collapse
|
11
|
Mable BK, Alexandrou MA, Taylor MI. Genome duplication in amphibians and fish: an extended synthesis. J Zool (1987) 2011. [DOI: 10.1111/j.1469-7998.2011.00829.x] [Citation(s) in RCA: 173] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
|
12
|
Michalak P, Malone JH. Testis-derived microRNA profiles of African clawed frogs (Xenopus) and their sterile hybrids. Genomics 2008; 91:158-64. [PMID: 18079091 DOI: 10.1016/j.ygeno.2007.10.013] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2007] [Revised: 10/26/2007] [Accepted: 10/29/2007] [Indexed: 12/12/2022]
Abstract
Gene regulation was long predicted to play a vital role in speciation and species divergence. Only recently with the advent of new technologies, however, has it been possible to address the question of the relative contributions of different mechanisms of gene expression to the evolution of phenotypic diversity. Here we broaden the question and ask whether microRNAs, a large class of small regulatory RNAs, play a role in reproductive isolation between species by contributing to hybrid male sterility. MicroRNAs from the testes of clawed frogs (Xenopus) were extracted and the expression profiles of sterile hybrids were compared with males of a parental species. Hybrid testes were largely microRNA-depleted relative to those of nonhybrids, and this pattern was validated with quantitative RT-PCR. A number of candidate differential microRNAs from this study have previously been described as testis-specific in the mouse, suggesting that microRNA structural conservation may be associated with functional retention.
Collapse
Affiliation(s)
- Pawel Michalak
- Department of Biology, University of Texas Arlington, Box 19498, Arlington, TX 76019, USA.
| | | |
Collapse
|
13
|
Malone JH, Chrzanowski TH, Michalak P. Sterility and gene expression in hybrid males of Xenopus laevis and X. muelleri. PLoS One 2007; 2:e781. [PMID: 17712429 PMCID: PMC1940320 DOI: 10.1371/journal.pone.0000781] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2007] [Accepted: 07/18/2007] [Indexed: 12/12/2022] Open
Abstract
BACKGROUND Reproductive isolation is a defining characteristic of populations that represent unique biological species, yet we know very little about the gene expression basis for reproductive isolation. The advent of powerful molecular biology tools provides the ability to identify genes involved in reproductive isolation and focuses attention on the molecular mechanisms that separate biological species. Herein we quantify the sterility pattern of hybrid males in African Clawed Frogs (Xenopus) and apply microarray analysis of the expression pattern found in testes to identify genes that are misexpressed in hybrid males relative to their two parental species (Xenopus laevis and X. muelleri). METHODOLOGY/PRINCIPAL FINDINGS Phenotypic characteristics of spermatogenesis in sterile male hybrids (X. laevis x X. muelleri) were examined using a novel sperm assay that allowed quantification of live, dead, and undifferentiated sperm cells, the number of motile vs. immotile sperm, and sperm morphology. Hybrids exhibited a dramatically lower abundance of mature sperm relative to the parental species. Hybrid spermatozoa were larger in size and accompanied by numerous undifferentiated sperm cells. Microarray analysis of gene expression in testes was combined with a correction for sequence divergence derived from genomic hybridizations to identify candidate genes involved in the sterility phenotype. Analysis of the transcriptome revealed a striking asymmetric pattern of misexpression. There were only about 140 genes misexpressed in hybrids compared to X. laevis but nearly 4,000 genes misexpressed in hybrids compared to X. muelleri. CONCLUSIONS/SIGNIFICANCE Our results provide an important correlation between phenotypic characteristics of sperm and gene expression in sterile hybrid males. The broad pattern of gene misexpression suggests intriguing mechanisms creating the dominance pattern of the X. laevis genome in hybrids. These findings significantly contribute to growing evidence for allelic dominance in hybrids and have implications for the mechanism of species differentiation at the transcriptome level.
Collapse
Affiliation(s)
- John H. Malone
- Department of Biology, The University of Texas at Arlington, Arlington, Texas, United States of America
| | - Thomas H. Chrzanowski
- Department of Biology, The University of Texas at Arlington, Arlington, Texas, United States of America
| | - Pawel Michalak
- Department of Biology, The University of Texas at Arlington, Arlington, Texas, United States of America
| |
Collapse
|
14
|
Malone JH, Hawkins DL, Michalak P. Sex-biased gene expression in a ZW sex determination system. J Mol Evol 2006; 63:427-36. [PMID: 17024524 DOI: 10.1007/s00239-005-0263-4] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2005] [Accepted: 05/20/2006] [Indexed: 12/22/2022]
Abstract
Studies of the transcriptome have shown that a substantial fraction of interspecific differences in gene expression is the result of sex-biased gene expression. These results suggest that sex-dependent selection may be an important force in generating differences between species but to date all studies have focused on Drosophila. We examined a sample of the transcriptome in the gonads of two species of Xenopus to provide an additional test of how sex-biased gene expression may contribute to differences in gene expression between species. In contrast to Drosophila, Xenopus provides an example of a ZW system with morphologically indistinguishable sex chromosomes. About 81% of the transcriptome was differentially expressed between X. laevis and X. muelleri and there were more genes that were male-biased compared to the number of genes that were female-biased or non-sex-biased. While there were more genes up-regulated in males of Xenopus, the largest magnitude difference in expression between species occurred in female-biased genes, and male-biased genes were proportionally more abundant for the smallest changes in expression between species. Our results suggest that more genes have a role in the function of the testis compared to the ovary and female-biased genes play a principle role in expression divergence between species. These results differ from those in the Drosophila XY system in that more female-biased genes had >4-fold difference of expression between species than male-biased genes, suggesting that ZW sex chromosomes may facilitate enhanced gene expression divergence between species.
Collapse
Affiliation(s)
- John H Malone
- Department of Biology, The University of Texas--Arlington, Box 19498, Arlington, TX 76019, USA
| | | | | |
Collapse
|
15
|
Evans BJ, Kelley DB, Tinsley RC, Melnick DJ, Cannatella DC. A mitochondrial DNA phylogeny of African clawed frogs: phylogeography and implications for polyploid evolution. Mol Phylogenet Evol 2004; 33:197-213. [PMID: 15324848 DOI: 10.1016/j.ympev.2004.04.018] [Citation(s) in RCA: 212] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2004] [Revised: 04/20/2004] [Indexed: 11/26/2022]
Abstract
The African clawed frogs (Silurana and Xenopus), model organisms for scientific inquiry, are unusual in that allopolyploidization has occurred on multiple occasions, giving rise to tetraploid, octoploid, and dodecaploid species. To better understand their evolution, here we estimate a mitochondrial DNA phylogeny from all described and some undescribed species. We examine the timing and location of diversification, and test hypotheses concerning the frequency of polyploid speciation and taxonomy. Using a relaxed molecular clock, we estimate that extant clawed frog lineages originated well after the breakup of Gondwana, about 63.7 million years ago, with a 95% confidence interval from 50.4 to 81.3 million years ago. Silurana and two major lineages of Xenopus have overlapping distributions in sub-Saharan Africa, and dispersal-vicariance analysis suggests that clawed frogs originated in central and/or eastern equatorial Africa. Most or all extant species originated before the Pleistocene; recent rainforest refugia probably acted as "lifeboats" that preserved existing species, rather than "species pumps" where many new successful lineages originated. We estimate that polyploidization occurred at least six times in clawed frogs.
Collapse
Affiliation(s)
- Ben J Evans
- Department of Biology, McMaster University, Life Sciences Building, Room 328, 1280 Main Street West, Hamilton, Ont., Canada.
| | | | | | | | | |
Collapse
|
16
|
Jackson JA, Tinsley RC. Parasite infectivity to hybridising host species: a link between hybrid resistance and allopolyploid speciation? Int J Parasitol 2003; 33:137-44. [PMID: 12633651 DOI: 10.1016/s0020-7519(02)00255-2] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Variation in host-specific infectivity was studied in monogenean polystome parasites (Protopolystoma spp.) of the interfertile, parapatric anurans Xenopus laevis laevis and Xenopus muelleri. Laboratory-raised host F1 hybrids were resistant to parasites respectively specific to each parent taxon in nature. This resistance occurred against parasite isolates from both inside and outside a host hybrid/sympatric zone (and no isolate was compatible with the foreign host species under experimental conditions). Geographical Protopolystoma xenopodis isolates showed variable infectivity to a single full-sib group of their usual host, X. l. laevis, and strains with high or low infectivity to these sibs co-occurred in spatially distant local areas (separated by 1,700 km). The host compatibility of P. xenopodis was also subject to host genotypexparasite genotype interactions. Refractoriness to some parasites or pathogens, as a consequence of hybridisation, may have conferred a selective advantage on the allopolyploid pathway by which most Xenopus spp. are believed to have evolved.
Collapse
Affiliation(s)
- J A Jackson
- School of Biological Sciences, University of Bristol, Bristol, BS8 1UG, UK.
| | | |
Collapse
|
17
|
Jackson JA, Tinsley RC, Du Preez LH. Differentiation of two locally sympatric Protopolystoma (Monogenea: Polystomatidae) species by temperature-dependent larval development and survival. Int J Parasitol 2001; 31:815-21. [PMID: 11403773 DOI: 10.1016/s0020-7519(01)00185-0] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The developmental response of egg stages to different environmental temperature regimes was studied in Protopolystoma xenopodis and Protopolystoma orientalis (Monogenea: Polystomatidae) isolates from southern Africa. Eggs failed to develop at 10 degrees C, whilst at 15 degrees C only P. xenopodis completed larval development, hatching 49--88 days post-collection. Respective hatching windows were 26--34 (P. xenopodis) and 37--49 (P. orientalis) days at 20 degrees C, and 18--26 and 27--37 days at 25 degrees C. Continuous maintenance at 30 degrees C was lethal for eggs of both species. There were no consistent interspecific differences in the response of egg stages to low and high temperature shocks during early embryonic development.
Collapse
Affiliation(s)
- J A Jackson
- School of Biological Sciences, University of Bristol, Bristol BS8 1UG, UK
| | | | | |
Collapse
|