The Experts below are selected from a list of 342 Experts worldwide ranked by ideXlab platform
Sanae Kasahara - One of the best experts on this subject based on the ideXlab platform.
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comparative karyotype analysis and chromosome evolution in the genus aplastodiscus cophomantini hylinae hylidae
BMC Genetics, 2012Co-Authors: Simone Lilian Gruber, Juliana Zina, Hideki Narimatsu, Célio F. B. Haddad, Sanae KasaharaAbstract:Background: The frogs of the Tribe Cophomantini present, in general, 2n=24 karyotype, but data on Aplastodiscus showed variation in diploid number from 2n=24 to 2n=18. Five species were karyotyped, one of them for the first time, using conventional and molecular cytogenetic techniques, with the aim to perform a comprehensive comparative analysis towards the understanding of chromosome evolution in light of the phylogeny. Results: Aplastodiscus perviridis showed 2n=24, A. arildae and A. eugenioi, 2n=22, A. callipygius, 2n=20, and A. leucopygius, 2n=18. In the metaphase I cells of two species only bivalents occurred, whereas in A. arildae, A. callipygius, and A. leucopygius one tetravalent was also observed besides the bivalents. BrdU incorporation produced replication bands especially in the largest chromosomes, and a relatively good banding correspondence was noticed among some of them. Silver impregnation and FISH with an rDNA probe identified a single NOR pair: the 11 in A. perviridis and A. arildae; the 6 in A. eugenioi; and the 9 in A. callipygius and A. leucopygius. C-banding showed a predominantly centromeric distribution of the heterochromatin, and in one of the species distinct molecular composition was revealed by CMA3. The telomeric probe hybridised all chromosome ends and additionally disclosed the presence of telomere-like sequences in centromeric regions of three species. Conclusions: Based on the hypothesis of 2n=24 ancestral karyotype for Aplastodiscus, and considering the karyotype differences and similarities, two evolutionary pathways through fusion events were suggested. One of them corresponded to the reduction of 2n=24 to 22, and the other, the reduction of 2n=24 to 20, and subsequently to 18. Regarding the NOR, two conditions were recognised: Plesiomorphy, represented by the homeologous small-sized NOR-bearing pairs, and derivation, represented by the NOR in a medium-sized pair. In spite of the apparent uniformity of C-banding patterns, heterogeneity in the molecular composition of some repetitive regions was revealed by CMA3 staining and by interstitial telomeric labelling. The meiotic tetravalent might be due to minute reciprocal translocations or to non-chiasmatic ectopic pairing between terminal repetitive sequences. The comparative cytogenetic analysis allowed to outline the chromosome evolution and contributed to enlighten the relationships within the genus Aplastodiscus.
Simone Lilian Gruber - One of the best experts on this subject based on the ideXlab platform.
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comparative karyotype analysis and chromosome evolution in the genus aplastodiscus cophomantini hylinae hylidae
BMC Genetics, 2012Co-Authors: Simone Lilian Gruber, Juliana Zina, Hideki Narimatsu, Célio F. B. Haddad, Sanae KasaharaAbstract:Background: The frogs of the Tribe Cophomantini present, in general, 2n=24 karyotype, but data on Aplastodiscus showed variation in diploid number from 2n=24 to 2n=18. Five species were karyotyped, one of them for the first time, using conventional and molecular cytogenetic techniques, with the aim to perform a comprehensive comparative analysis towards the understanding of chromosome evolution in light of the phylogeny. Results: Aplastodiscus perviridis showed 2n=24, A. arildae and A. eugenioi, 2n=22, A. callipygius, 2n=20, and A. leucopygius, 2n=18. In the metaphase I cells of two species only bivalents occurred, whereas in A. arildae, A. callipygius, and A. leucopygius one tetravalent was also observed besides the bivalents. BrdU incorporation produced replication bands especially in the largest chromosomes, and a relatively good banding correspondence was noticed among some of them. Silver impregnation and FISH with an rDNA probe identified a single NOR pair: the 11 in A. perviridis and A. arildae; the 6 in A. eugenioi; and the 9 in A. callipygius and A. leucopygius. C-banding showed a predominantly centromeric distribution of the heterochromatin, and in one of the species distinct molecular composition was revealed by CMA3. The telomeric probe hybridised all chromosome ends and additionally disclosed the presence of telomere-like sequences in centromeric regions of three species. Conclusions: Based on the hypothesis of 2n=24 ancestral karyotype for Aplastodiscus, and considering the karyotype differences and similarities, two evolutionary pathways through fusion events were suggested. One of them corresponded to the reduction of 2n=24 to 22, and the other, the reduction of 2n=24 to 20, and subsequently to 18. Regarding the NOR, two conditions were recognised: Plesiomorphy, represented by the homeologous small-sized NOR-bearing pairs, and derivation, represented by the NOR in a medium-sized pair. In spite of the apparent uniformity of C-banding patterns, heterogeneity in the molecular composition of some repetitive regions was revealed by CMA3 staining and by interstitial telomeric labelling. The meiotic tetravalent might be due to minute reciprocal translocations or to non-chiasmatic ectopic pairing between terminal repetitive sequences. The comparative cytogenetic analysis allowed to outline the chromosome evolution and contributed to enlighten the relationships within the genus Aplastodiscus.
Rudi Loesel - One of the best experts on this subject based on the ideXlab platform.
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Comparative neuroanatomy suggests repeated reduction of neuroarchitectural complexity in Annelida
Frontiers in Zoology, 2010Co-Authors: Carsten M Heuer, Carsten Hg Müller, Christiane Todt, Rudi LoeselAbstract:Background Paired mushroom bodies, an unpaired central complex, and bilaterally arranged clusters of olfactory glomeruli are among the most distinctive components of arthropod neuroarchitecture. Mushroom body neuropils, unpaired midline neuropils, and olfactory glomeruli also occur in the brains of some polychaete annelids, showing varying degrees of morphological similarity to their arthropod counterparts. Attempts to elucidate the evolutionary origin of these neuropils and to deduce an ancestral ground pattern of annelid cerebral complexity are impeded by the incomplete knowledge of annelid phylogeny and by a lack of comparative neuroanatomical data for this group. The present account aims to provide new morphological data for a broad range of annelid taxa in order to trace the occurrence and variability of higher brain centers in segmented worms. Results Immunohistochemically stained preparations provide comparative neuroanatomical data for representatives from 22 annelid species. The most prominent neuropil structures to be encountered in the annelid brain are the paired mushroom bodies that occur in a number of polychaete taxa. Mushroom bodies can in some cases be demonstrated to be closely associated with clusters of spheroid neuropils reminiscent of arthropod olfactory glomeruli. Less distinctive subcompartments of the annelid brain are unpaired midline neuropils that bear a remote resemblance to similar components in the arthropod brain. The occurrence of higher brain centers such as mushroom bodies, olfactory glomeruli, and unpaired midline neuropils seems to be restricted to errant polychaetes. Conclusions The implications of an assumed homology between annelid and arthropod mushroom bodies are discussed in light of the 'new animal phylogeny'. It is concluded that the apparent homology of mushroom bodies in distantly related groups has to be interpreted as a Plesiomorphy, pointing towards a considerably complex neuroarchitecture inherited from the last common ancestor, Urbilateria. Within the annelid radiation, the lack of mushroom bodies in certain groups is explained by widespread secondary reductions owing to selective pressures unfavorable for the differentiation of elaborate brains. Evolutionary pathways of mushroom body neuropils in errant polychaetes remain enigmatic.
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comparative neuroanatomy suggests repeated reduction of neuroarchitectural complexity in annelida
Frontiers in Zoology, 2010Co-Authors: Carsten M Heuer, Carsten Hg Müller, Christiane Todt, Rudi LoeselAbstract:Paired mushroom bodies, an unpaired central complex, and bilaterally arranged clusters of olfactory glomeruli are among the most distinctive components of arthropod neuroarchitecture. Mushroom body neuropils, unpaired midline neuropils, and olfactory glomeruli also occur in the brains of some polychaete annelids, showing varying degrees of morphological similarity to their arthropod counterparts. Attempts to elucidate the evolutionary origin of these neuropils and to deduce an ancestral ground pattern of annelid cerebral complexity are impeded by the incomplete knowledge of annelid phylogeny and by a lack of comparative neuroanatomical data for this group. The present account aims to provide new morphological data for a broad range of annelid taxa in order to trace the occurrence and variability of higher brain centers in segmented worms. Immunohistochemically stained preparations provide comparative neuroanatomical data for representatives from 22 annelid species. The most prominent neuropil structures to be encountered in the annelid brain are the paired mushroom bodies that occur in a number of polychaete taxa. Mushroom bodies can in some cases be demonstrated to be closely associated with clusters of spheroid neuropils reminiscent of arthropod olfactory glomeruli. Less distinctive subcompartments of the annelid brain are unpaired midline neuropils that bear a remote resemblance to similar components in the arthropod brain. The occurrence of higher brain centers such as mushroom bodies, olfactory glomeruli, and unpaired midline neuropils seems to be restricted to errant polychaetes. The implications of an assumed homology between annelid and arthropod mushroom bodies are discussed in light of the 'new animal phylogeny'. It is concluded that the apparent homology of mushroom bodies in distantly related groups has to be interpreted as a Plesiomorphy, pointing towards a considerably complex neuroarchitecture inherited from the last common ancestor, Urbilateria. Within the annelid radiation, the lack of mushroom bodies in certain groups is explained by widespread secondary reductions owing to selective pressures unfavorable for the differentiation of elaborate brains. Evolutionary pathways of mushroom body neuropils in errant polychaetes remain enigmatic.
Colin A Chapman - One of the best experts on this subject based on the ideXlab platform.
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frugivores and fruit syndromes differences in patterns at the genus and species level
Oikos, 1993Co-Authors: Kathleen E Fischer, Colin A ChapmanAbstract:Comparative studies have suggested that fruit traits, such as color, size, and protection, have evolved as covarying character complexes («dispersal syndromes») in response to selection by frugivorous dispersers. However, many comparative studies of disperser-specific syndromes have used species as sampling units, a method which implicitly assumes that character complexes evolve de novo in each species. This approach overestimates the number of times a character complex has evolved because covariation that results from common ancestry (Plesiomorphy) is confounded with covariation across independent lineages (convergence)
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Frugivores and fruit syndromes: Differences in patterns at the genus and species level
1993Co-Authors: Kathleen E Fischer, Colin A ChapmanAbstract:ences in patterns at the genus and species level.- Oikos 66: 472-482. Comparative studies have suggested that fruit traits, such as color, size, and protec-tion, have evolved as covarying character complexes ("dispersal syndromes") in response to selection by frugivorous dispersers. However, many comparative studies of disperser-specific syndromes have used species as sampling units, a method which implicitly assumes that character complexes evolve de novo in each species. This approach overestimates the number of times a character complex has evolved be-cause covariation that results from common ancestry (Plesiomorphy) is confounded with covariation across independent lineages (convergence). We compiled data on fleshy fruit traits from five regional floras to test the hypothesis that fruit traits form character complexes which covary independently of phylogeny (i.e. across lineages). Our results suggest that such character complexes are rare, and that analyses of covariation among these character complexes are extremely sensitive to the in-vestigator's choice of sampling unit. When syndromes derived from observations of the foraging behavior of frugivores are analyzed using species as sampling units, our data show significant associations among traits at four out of five locations. I
Alexander R Pyron - One of the best experts on this subject based on the ideXlab platform.
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novel approaches for phylogenetic inference from morphological data and total evidence dating in squamate reptiles lizards snakes and amphisbaenians
Systematic Biology, 2016Co-Authors: Alexander R PyronAbstract:Here, I combine previously underutilized models and priors to perform more biologically realistic phylogenetic inference from morphological data, with an example from squamate reptiles. When coding morphological characters, it is often possible to denote ordered states with explicit reference to observed or hypothetical ancestral conditions. Using this logic, we can integrate across character-state labels and estimate meaningful rates of forward and backward transitions from Plesiomorphy to apomorphy. I refer to this approach as MkA, for “asymmetric.” The MkA model incorporates the biological reality of limited reversal for many phylogenetically informative characters, and significantly increases likelihoods in the empirical data sets. Despite this, the phylogeny of Squamata remains contentious. Total-evidence analyses using combined morphological and molecular data and the MkA approach tend toward recent consensus estimates supporting a nested Iguania. However, support for this topology is not unambiguous across data sets or analyses, and no mechanism has been proposed to explain the widespread incongruence between partitions, or the hidden support for various topologies in those partitions. Furthermore, different morphological data sets produced by different authors contain both different characters and different states for the same or similar characters, resulting in drastically different placements for many important fossil lineages. Effort is needed to standardize ontology for morphology, resolve incongruence, and estimate a robust phylogeny. The MkA approach provides a preliminary avenue for investigating morphological evolution while accounting for temporal evidence and asymmetry in character-state changes.