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Morphological Diversification (morphological + diversification)
Selected AbstractsAnalysis of nubbin expression patterns in insectsEVOLUTION AND DEVELOPMENT, Issue 5 2004Hua Li Summary Previous studies have shown that the gene nubbin (nub) exhibits large differences in expression patterns between major groups of arthropods. This led us to hypothesize that nub may have evolved roles that are unique to particular arthropod lineages. However, in insects, nub has been studied only in Drosophila. To further explore its role in insects in general, we analyzed nub expression patterns in three hemimetabolous insect groups: zygentomans (Thermobia domestica, firebrat), dyctiopterans (Periplaneta americana, cockroach), and hemipterans (Oncopeltus fasciatus, milkweed bug). We discovered three major findings. First, observed nub patterns in the ventral central nervous system ectoderm represent a synapomorphy (shared derived feature) that is not present in other arthropods. Furthermore, each of the analyzed insects exhibits a species-specific nub expression in the central nervous system. Second, recruitment of nub for a role in leg segmentation occurred early during insect evolution. Subsequently, in some insect lineages (cockroaches and flies), this original role was expanded to include joints between all the leg segments. Third, the nub expression in the head region shows a coordinated change in association with particular mouthpart morphology. This suggests that nub has also gained an important role in the morphological diversification of insect mouthparts. Overall, the obtained data reveal an extraordinary dynamic and diverse pattern of nub evolution that has not been observed previously for other developmental genes. [source] Functionally redundant SHI family genes regulate Arabidopsis gynoecium development in a dose-dependent mannerTHE PLANT JOURNAL, Issue 1 2006Sandra Kuusk Summary Gene duplication events, and the subsequent functional divergence of duplicates, are believed to be important evolutionary agents, driving morphological diversification. We have studied the structural and functional diversification of members of a plant-specific gene family in Arabidopsis thaliana by analysing mutant phenotypes, expression patterns and phylogeny. The SHI gene family comprises ten members that encode proteins with a RING finger-like zinc finger motif. We show that, despite being highly divergent in sequence, except in two conserved regions, many of the SHI -related genes are partially redundant in function and synergistically promote gynoecium, stamen and leaf development in Arabidopsis. Gynoecia of the loss-of-function sty1-1 mutant display subtle morphological defects, and, although mutations in the related STY2, SHI, SRS3, SRS4, SRS5, SRS7 and LRP1 genes have no apparent effect on gynoecium development, the sty1-1 mutant phenotype is gradually enhanced in double, triple, quadruple and quintuple mutant combinations, suggesting a remarkably extensive functional conservation within the family, which appears to be based on dosage dependency and protection against dominant negative mutations. In multiple mutant lines, all marginal tissues in the apical part of the gynoecium are dramatically reduced or missing, and our data indicate that SHI family members may promote formation of these tissues downstream of the transcriptional co-repressor LEUNIG (LUG). [source] Does sympatry predict life history and morphological diversification in the Mexican livebearing fish Poeciliopsis baenschi?BIOLOGICAL JOURNAL OF THE LINNEAN SOCIETY, Issue 3 2010LAURA E. SCOTT Understanding why some species coexist and others do not remains one of the fundamental challenges of ecology. Although there is evidence to suggest that closely-related species are unlikely to occupy the same habitat because of competitive exclusion, there are many cases where closely-related species do co-occur. Research comparing sympatric and allopatric populations of co-occurring species provides a framework for understanding the role of phenotypic diversification in species coexistence. In the present study, we compare phenotypic divergence between sympatric and allopatric populations of the livebearing fish, Poeciliopsis baenschi. We focus on life-history traits and body shape, comprising two sets of integrated traits likely to diverge in response to varying selective pressures. Given that males and females can express different phenotypic traits, we also test for patterns of divergence among sexes by comparing size at maturity and sexual dimorphism in body shape between males and females in each population type. We take advantage of a natural experiment in western Mexico where, in some locations, P. baenschi co-occur with a closely-related species, Poeciliopsis turneri (sympatric populations) and, in other locations, they occur in isolation (allopatric populations). The results obtained in the present study show that sympatric populations of P. baenschi differed significantly in life-history traits and in body shape compared to their allopatric counterparts. Additionally, males and females showed different responses for size at maturity in sympatric conditions versus allopatric conditions. However, the amount of sexual dimorphism did not differ between sympatric and allopatric populations of P. baenschi. Hence, we conclude that not all traits show similar levels of phenotypic divergence in response to sympatric conditions. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 100, 608,618. [source] Latitudinal variation in axial patterning of the medaka (Actinopterygii: Adrianichthyidae): Jordan's rule is substantiated by genetic variation in abdominal vertebral numberBIOLOGICAL JOURNAL OF THE LINNEAN SOCIETY, Issue 4 2009KAZUNORI YAMAHIRA Because the body axes of fish consist of two anatomically distinct vertebrae, abdominal and caudal, one type may be more variable in number than the other and thus contribute more to morphological diversification. Jordan's rule, a geographical tendency for fish from higher latitudes to have more vertebrae, has not been examined in terms of numbers of abdominal and/or caudal vertebrae, despite its prevalence. Vertebral observations of wild populations of the medaka (Oryzias latipes) revealed that the latitudinal increase in vertebral number is caused by an increase in abdominal vertebrae; caudal vertebrae did not vary systematically across latitudes. Laboratory experiments revealed that this latitudinal cline in abdominal vertebral number persists in a range of common environments, demonstrating a genetic basis. Phenotypic plasticity was also evident: lower developmental temperatures resulted in more abdominal vertebrae. This indicates that greater numbers of abdominal vertebrae in higher latitude individuals in the wild may be caused not only by genetic factors but by lower habitat temperatures, although the contribution of the former to Jordan's rule is assessed to be much greater. The genetic basis of the latitudinal variation in abdominal vertebral number suggests that selection on functions associated with abdominal regions is the probable explanation for Jordan's rule in this fish. © 2009 The Linnean Society of London, Biological Journal of the Linnean Society, 2009, 96, 856,866. [source] Heritability and genetic correlation of abdominal versus caudal vertebral number in the medaka (Actinopterygii: Adrianichthyidae): genetic constraints on evolution of axial patterning?BIOLOGICAL JOURNAL OF THE LINNEAN SOCIETY, Issue 4 2009KAZUNORI YAMAHIRA Variation in the number of abdominal vs. caudal vertebrae is an important source of morphological diversification of fish. It is not clear, however, whether abdominal and caudal regions evolve independently. Regressions of offspring on parents demonstrated substantial additive genetic variation within populations, i.e. heritability, in both abdominal and caudal vertebral numbers of the medaka (Oryzias latipes). However, the heritability of caudal vertebrae tended to be smaller than that of abdominal vertebrae in some estimations, suggesting that abdominal and caudal regions are controlled by separate developmental modules. Furthermore, genetic correlation between abdominal and caudal vertebral numbers, estimated using full-sib family means, was negative but weak, supporting independent evolution. In addition, substantial genetic differentiation among populations was demonstrated in abdominal vertebral numbers, but not in caudal numbers. These results support our view that Jordan's rule, a geographical tendency for fish from higher latitudes to have more vertebrae, in this fish reflects local adaptations of abdominal vertebral numbers. In contrast, the low heritability of caudal vertebrae may reflect the intrinsic invariability of genes associated with a change in caudal vertebral numbers. This genetic constraint may have restricted morphological diversification of not only the medaka, but also the Order Beloniformes as a whole. © 2009 The Linnean Society of London, Biological Journal of the Linnean Society, 2009, 96, 867,874. [source] Phylogenetic relationships of Clematis (Ranunculaceae) based on chloroplast and nuclear DNA sequencesBOTANICAL JOURNAL OF THE LINNEAN SOCIETY, Issue 2 2006OSAMU 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] | ||||||||||||||||||||||