Recent Radiation (recent + radiation)

Distribution by Scientific Domains
Distribution within Life Sciences


Selected Abstracts


Phenotypic divergence but not genetic distance predicts assortative mating among species of a cichlid fish radiation

JOURNAL OF EVOLUTIONARY BIOLOGY, Issue 8 2009
R. B. STELKENS
Abstract The hypothesis of ecological divergence giving rise to premating isolation in the face of gene flow is controversial. However, this may be an important mechanism to explain the rapid multiplication of species during adaptive radiation following the colonization of a new environment when geographical barriers to gene flow are largely absent but underutilized niche space is abundant. Using cichlid fish, we tested the prediction of ecological speciation that the strength of premating isolation among species is predicted by phenotypic rather than genetic distance. We conducted mate choice experiments between three closely related, sympatric species of a recent radiation in Lake Mweru (Zambia/DRC) that differ in habitat use and phenotype, and a distantly related population from Lake Bangweulu that resembles one of the species in Lake Mweru. We found significant assortative mating among all closely related, sympatric species that differed phenotypically, but none between the distantly related allopatric populations of more similar phenotype. Phenotypic distance between species was a good predictor of the strength of premating isolation, suggesting that assortative mating can evolve rapidly in association with ecological divergence during adaptive radiation. Our data also reveals that distantly related allopatric populations that have not diverged phenotypically, may hybridize when coming into secondary contact, e.g. upon river capture because of diversion of drainage systems. [source]


Phylogeographic analysis of a recent radiation of Enallagma damselflies (Odonata: Coenagrionidae)

MOLECULAR ECOLOGY, Issue 10 2002
J. Turgeon
Abstract A phylogenetic hypothesis revealed two recent radiations among species of Enallagma damselflies, and extensive ecological work suggests that both adaptive and nonadaptive processes are involved in these radiations. We analysed the geographical pattern of genetic variability at 868 bp of mitochondrial DNA (mtDNA) among 283 individuals of 5 species displaying little ecological differentiation to identify the ancestral lineage, support their independent evolutionary trajectories and identify historical events and the underlying mechanism for one of these radiations. Nested clade analysis results clearly support a past event of range fragmentation in E. hageni. These Atlantic and Continental hageni races experienced distinct dispersal histories and still maintain nearly nonoverlapping ranges All four other species derive from the Continental hageni. Whereas three species endemic to the Atlantic coastal plain show little genetic variation, E. ebrium shared several haplotypes with the Continental hageni. Contrasting levels of genetic differentiation between E. hageni and E. ebrium in geographical areas associated with distinct events of E. hageni's recent history support the recent origin of this species. Altogether, our results are compatible with a process of radiation via divergence in mate recognition systems within the Continental hageni race following secondary contacts between putative refugial races. [source]


Novel features of Equisetum arvense spermatozoids: insights into pteridophyte evolution

NEW PHYTOLOGIST, Issue 1 2002
K. S. Renzaglia
Summary ,,To characterize structural diversity within Equisetum and among pteridophytes, architectural features of the sperm cell are described here in a second subgenus of Equisetum, a divergent basal group in the fern clade. ,,Transmission electron microscopy observations of prereleased spermatozoids of Equisetum arvense were correlated with three-dimensional scanning electron microscopy images of swimming cells. ,,The mature spermatozoid completes a helix of approximately 2.5 revolutions. At the cell anterior is a complex multilayered locomotory apparatus with staggered flagella. Mitochondria (elongated,rounded) are aggregated near the locomotory apparatus and organelles extend along the cell length. The spline contains up to 300 microtubules and wraps in part around the long cylindrical nucleus. In swimming sperm cells, the anterior of the cell remains tightly coiled while the posterior relaxes and extends in a trailing fashion. ,,Spermatozoids of Equisetum arvense are smaller than those of Equisetum hyemale but structurally similar, except for nuclear shape. Conservation of cellular features suggests recent radiation of the genus. Equisetum spermatozoids share several critical features with ferns, including Psilotum, and support monophyly of a fern,Equisetum assemblage. Entry of the male gametes of Equisetum in their entirety into the archegonial venters indicates possible biparental inheritance of chloroplast and mitochondrial genomes. [source]


Morphofunctional patterns in Neotropical felids: species co-existence and historical assembly

BIOLOGICAL JOURNAL OF THE LINNEAN SOCIETY, Issue 3 2010
MIRIAM M. MORALES
Extant felids are morphologically homogeneous, probably as a result of recent radiation and constraints from their predatory specializations. The Neotropical assemblage comprises 12 of the 41 extant felid species, which occupy all habitats available, with many species coexisting locally. We studied this assemblage on the basis of 31 craniodental variables reflecting morphofunctional variation, measured from 229 specimens representing all 12 species. Multivariate patterns were summarized allowing for phylogenetic covariation. Additional factors (geographical distribution, use of habitat and stratum, and activity pattern) were coded for each species. As expected, body size accounted for most variation, covarying with membership to three deep clades and, to a lesser extent, with large-scale geographic variation. The species tend to segregate in morphospace plus one or more factors (e.g. habits) that make interspecific overlap in niche space minimal. Using dated phylogenies, biogeographic history, and the fossil record, we reconstructed the historical assembly of the Neotropical felid guild. We found a pattern of successive invasions and speciation in which new lineages occupied previously vacant areas of morphospace, or new species occupied overlapping areas but with contrasting habits. This may be general among antagonistic species of historically structured guilds, and we predict similar patterns in other continents. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 100, 711,724. [source]


Phylogenetic relationships of Clematis (Ranunculaceae) based on chloroplast and nuclear DNA sequences

BOTANICAL JOURNAL OF THE LINNEAN SOCIETY, Issue 2 2006
OSAMU MIIKEDA
Phylogenetic relationships within Clematis, including Naravelia, Archiclematis and Clematopsis, were analysed using nucleotide sequences of chloroplast DNA [(1) matK and trnK introns; (2) atpB,rbcL spacer; (3) rpoB,trnC spacer; (4) psbA,trnH,trnQ spacer; (5) rbcL,accD spacer] and the nuclear ITS regions. The phylogenetic trees resulting from these analyses suggested nine major clades. The genera Archiclematis, Naravelia and Clematopsis were found to be nested within the genus Clematis, and should be included within it. Within the genus Clematis, the traditional subgenus Viorna was found to be monophyletic. The remaining subgenera (Flammula, Clematis and Campanella) and sections Flammula, Clematis and Cheiropsis, however, were found to be paraphyletic or polyphyletic. Recircumscription of several groups in Clematis was suggested. Enormous morphological diversification and very few nucleotide substitutions within Clematis indicate the recent radiation of the genus. Clematidinae shares a gene order with Anemoninae between the starting point of large single copy region and trnQ of chloroplast DNA, although Hepatica, a genus in Anemoninae, shows a different order in the region near trnH. © 2006 The Linnean Society of London, Botanical Journal of the Linnean Society, 2006, 152, 153,168. [source]


A deficit of detoxification enzymes: pesticide sensitivity and environmental response in the honeybee

INSECT MOLECULAR BIOLOGY, Issue 5 2006
C. Claudianos
Abstract The honeybee genome has substantially fewer protein coding genes (, 11 000 genes) than Drosophila melanogaster (, 13 500) and Anopheles gambiae (, 14 000). Some of the most marked differences occur in three superfamilies encoding xenobiotic detoxifying enzymes. Specifically there are only about half as many glutathione-S-transferases (GSTs), cytochrome P450 monooxygenases (P450s) and carboxyl/cholinesterases (CCEs) in the honeybee. This includes 10-fold or greater shortfalls in the numbers of Delta and Epsilon GSTs and CYP4 P450s, members of which clades have been recurrently associated with insecticide resistance in other species. These shortfalls may contribute to the sensitivity of the honeybee to insecticides. On the other hand there are some recent radiations in CYP6, CYP9 and certain CCE clades in A. mellifera that could be associated with the evolution of the hormonal and chemosensory processes underpinning its highly organized eusociality. [source]


Phylogeographic analysis of a recent radiation of Enallagma damselflies (Odonata: Coenagrionidae)

MOLECULAR ECOLOGY, Issue 10 2002
J. Turgeon
Abstract A phylogenetic hypothesis revealed two recent radiations among species of Enallagma damselflies, and extensive ecological work suggests that both adaptive and nonadaptive processes are involved in these radiations. We analysed the geographical pattern of genetic variability at 868 bp of mitochondrial DNA (mtDNA) among 283 individuals of 5 species displaying little ecological differentiation to identify the ancestral lineage, support their independent evolutionary trajectories and identify historical events and the underlying mechanism for one of these radiations. Nested clade analysis results clearly support a past event of range fragmentation in E. hageni. These Atlantic and Continental hageni races experienced distinct dispersal histories and still maintain nearly nonoverlapping ranges All four other species derive from the Continental hageni. Whereas three species endemic to the Atlantic coastal plain show little genetic variation, E. ebrium shared several haplotypes with the Continental hageni. Contrasting levels of genetic differentiation between E. hageni and E. ebrium in geographical areas associated with distinct events of E. hageni's recent history support the recent origin of this species. Altogether, our results are compatible with a process of radiation via divergence in mate recognition systems within the Continental hageni race following secondary contacts between putative refugial races. [source]