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Mixed Mating Systems (mixed + mating_system)
Selected AbstractsClonal diversity and subpopulation structure in central European relict populations of Saxifraga paniculataMill. (Saxifragaceae)FEDDES REPERTORIUM, Issue 3-4 2004C. Reisch Saxifraga paniculata is a rare and endangered glacial relict in central Europe. It shows high clonal reproduction. In this study, we analysed the clonal diversity and the subpopulation structure of three populations from the species main distribution area in Germany outside of the Alps (Swabian Alb, Black Forest, Nahe Mountains). We used RAPD analysis to detect the genetic variation in S. paniculata and found high levels of clonal diversity. The percentage of distinguishable genotypes (PD) within populations of S. paniculata was 1.0 and even spatially well defined mats of rosettes consisted of several genotypes. In a cluster analysis, the investigated populations were clearly separated from each other. However, we detected no genetic differentiation among subpopulations. We ascribe the high level of genotypic variability to the species' mixed mating system, which creates and maintains high levels of genetic diversity within the populations of S. paniculata. Clonal reproduction seems, meanwhile, to be of secondary importance for the propagation of the species. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) Klonale Diversität und Subpopulationsstruktur in mitteleuropäischen Reliktpopulationen von Saxifraga paniculataMill. (Saxifragaceae) Saxifraga paniculata ist in Mitteleuropa ein seltenes und gefährdetes Glazialrelikt, das sich durch die Fähigkeit zu starker klonaler Reproduktion auszeichnet. Die vorliegende Arbeit befasst sich mit der klonalen Diversität und der Subpopulationsstruktur von drei Populationen aus dem Hauptverbreitungsgebiet der Art außerhalb der Alpen (Schwäbische Alb, Schwarzwald, Nahe-Bergland). Die genetische Variabilität wurde mittels RAPD-Analyse untersucht. Dabei konnte ein hohes Maß an klonaler Diversität festgestellt werden. Der Prozentsatz unterscheidbarer Genotypen innerhalb einer Population (PD) betrug 1.0 und selbst größere Matten, deren Entstehung nach rein morphologischer Einschätzung auf klonalem Wachstum beruhen müsste, bestanden aus mehreren Genotypen. In einer Clusteranalyse unterschieden sich die analysierten Populationen klar voneinander. Unterschiede zwischen Subpopulationen konnten jedoch nicht nachgewiesen werden. Das hohe Ausmaß an genetischer Diversität kann dem "mixed mating system" der Art zugeschrieben werden, das genetische Variabilität schafft und erhält. Klonales Wachstum scheint währenddessen eher von zweitrangiger Bedeutung für die Vermehrung der Art zu sein. [source] Low genetic diversity and high genetic differentiation in the critically endangered Omphalogramma souliei (Primulaceae): implications for its conservationJOURNAL OF SYSTEMATICS EVOLUTION, Issue 2 2009Yuan HUANG Abstract Omphalogramma souliei Franch. is an endangered perennial herb only distributed in alpine areas of SW China. ISSR markers were applied to determine the genetic variation and genetic structure of 60 individuals of three populations of O. souliei in NW Yunnan, China. The genetic diversity at the species level is low with P=42.5% (percentage of polymorphic bands) and Hsp=0.1762 (total genetic diversity). However, a high level of genetic differentiation among populations was detected based on different measures (Nei's genetic diversity analysis: Gst=0.6038; AMOVA analysis: Fst=0.6797). Low level of genetic diversity within populations and significant genetic differentiation among populations might be due to the mixed mating system in which xenogamy predominated and autogamy played an assistant role in O. souliei. The genetic drift due to small population size and limited current gene flow also resulted in significant genetic differentiation. The assessment of genetic variation and differentiation of the endangered species provides important information for conservation on a genetic basis. Conservation strategies for this rare endemic species are proposed. [source] Mating system and genetic diversity of a rare desert legume Ammopiptanthus nanus (Leguminosae)JOURNAL OF SYSTEMATICS EVOLUTION, Issue 1 2009Guo-Qing CHEN Abstract Ammopiptanthus nanus is an endangered evergreen shrub endemic to the deserts of central Asia and plays an important role in delaying further desertification. We examined allozyme variation and AFLP diversity in A. nanus populations and investigated the mating system of this species using progeny arrays assayed for polymorphic allozyme loci. Mating system analysis in the Keyi'eryongke'er population showed low levels of out-crossing, and strong inbreeding depression. Low levels of genetic variation were detected at both population (allozyme, Pp= 14.0%, A= 1.14, He= 0.031; AFLP, Pp= 14.5%, Shannon's information index I= 0.063) and species (allozyme, Pp= 21.1%, A= 1.21, He= 0.040; AFLP, Pp= 20.9%, I= 0.083) levels; while moderate genetic differentiation existed among populations, as indicated by allozymes (GST= 0.081) and AFLP (GST= 0.151,0.193). Founder effect, bottlenecks in evolutionary history, the mixed mating system and co-ancestry may have influenced the level of genetic diversity in A. nanus. Markers of both types provide new insights for conservation management, indicating that the Biao'ertuokuoyi and Keyi'eryongke'er populations should be given priority for in situ conservation and regarded as seed sources for ex situ conservation. [source] THE ROLE OF NATURAL ENEMIES IN THE EXPRESSION AND EVOLUTION OF MIXED MATING IN HERMAPHRODITIC PLANTS AND ANIMALSEVOLUTION, Issue 9 2007Janette A. Steets Although a large portion of plant and animal species exhibit intermediate levels of outcrossing, the factors that maintain this wealth of variation are not well understood. Natural enemies are one relatively understudied ecological factor that may influence the evolutionary stability of mixed mating. In this paper, we aim for a conceptual unification of the role of enemies in mating system expression and evolution in both hermaphroditic animals and plants. We review current theory and detail the potential effects of enemies on fundamental mating system parameters. In doing so, we identify situations in which consideration of enemies alters expectations about the stability of mixed mating. Generally, we find that inclusion of the enemy dimension may broaden conditions in which mixed mating systems are evolutionarily stable. Finally, we highlight avenues ripe for future theoretical and empirical work that will advance our understanding of enemies in the expression and evolution of mixed mating in their hosts/victims, including examination of feedback cycles between victims and enemies and quantification of mating system-related parameters in victim populations in the presence and absence of enemies. [source] The evolution of self-fertilization and inbreeding depression under pollen discounting and pollen limitationJOURNAL OF EVOLUTIONARY BIOLOGY, Issue 3 2005E. PORCHER Abstract We model the evolution of plant mating systems under the joint effects of pollen discounting and pollen limitation, using a dynamic model of inbreeding depression, allowing for partial purging of recessive lethal mutations by selfing. Stable mixed mating systems occur for a wide range of parameter values with pollen discounting alone. However, when typical levels of pollen limitation are combined with pollen discounting, stable selfing rates are always high but less than 1 (0.9 < s < 1 in most cases); in this situation, complete selfing does not evolve because pollen discounting becomes very large at high selfing rates, so that the automatic advantage of selfing changes to a disadvantage. These results suggest that mixed mating systems with high selfing rates can be maintained by selection, whereas mixed mating systems with low to moderate selfing rates are more likely attributable to unavoidable geitonogamous selfing. [source] Potential Autonomous Selfing in Gesneria citrina (Gesneriaceae), a Specialized Hummingbird Pollinated Species with Variable Expression of HerkogamyJOURNAL OF INTEGRATIVE PLANT BIOLOGY, Issue 10 2009Xin-Sheng Chen Abstract Species with mixed mating systems often demonstrate variable expression of breeding system characteristics and thus represent the opportunity to understand the factors and mechanisms that promote both outcrossed and selfed seed production. Here, we investigate variation in levels of herkogamy (variation in stigma-anther separation distance) in a Puerto Rican population of hummingbird pollinated Gesneria citrina Urban. There is significant variation in herkogamy levels among individuals of this species and stigma-anther separation is negatively associated with the ability to set fruits and seeds in the absence of pollinators. The variation in levels of herkogamy may represent a mechanism to ensure the production of some self-fertilized progeny in the absence of hummingbird pollinators. We also describe a novel breeding system in G. citrina, where stamens elongate over time to reach stigma height, but stamen elongation is accelerated by pollination. These results suggest that once the flowers are pollinated, stamen elongation may favor increased pollen removal and siring success, while the reduction in stigma-anther distance no longer imposes the risk of interference between male and female functions. We discuss our findings of breeding system variation in the context of pollination system evolution in an island setting (Antillean islands). [source] Genetic variation and clonal diversity in four clonal sedges (Carex) along the Arctic coast of EurasiaMOLECULAR ECOLOGY, Issue 2 2001Anna Stenström Abstract We studied the structure of genetic variation (at both ramet- and genet-level) and clonal diversity within and among populations in the four closely related arctic clonal sedges Carex bigelowii, C. ensifolia, C. lugens and C. stans by use of allozyme markers. Compared to other sedges and arctic plants, the studied taxa all had high levels of genetic variation, both within populations and taxa. These taxa contained most of the total gene diversity (HT) within populations and a small part of the diversity among populations (GST ranged 0.05,0.43). Carex bigelowii had genetic variation (HS = 0.173, mean for populations) at a comparable level to other outbreeding arctic plants and to other widespread, rhizomatous and mainly outbreeding Carex species. In contrast, C. ensifolia (HS = 0.335), C. lugens (HS = 0.339) and C. stans (HS = 0.294) had within-population variations that were higher than in most other studied Carex species and for arctic plants in general. Genetic variation was not related to any tested environmental variable, but it was lower in areas deglaciated only 10 000 years bp compared to areas deglaciated 60 000 years bp or not glaciated at all during the Weichselian. All the populations were multiclonal, except for two populations of C. stans that were monoclonal. In contrast to genetic variation, clonal diversity decreased with latitude and did not differ between areas with different times of deglaciation. In accordance with previous studies, C. bigelowii and C. lugens were found to be outbreeding, while C. ensifolia and C. stans had mixed mating systems. [source] RAPD Evidence for Apomixis and Clonal Populations in Eriotheca (Bombacaceae)PLANT BIOLOGY, Issue 3 2003R. L. Martins Abstract: Two woody species of Eriotheca (Bombacaceae) of the Central Brazilian Cerrados were submitted to RAPD analyses. Both species are bee pollinated and have a similar flower structure, but E. pubescens presents adventitious embryony and apomixis, while E. gracilipes is self-incompatible. The RAPD screening reflects these differences in breeding systems, with very low genetic variation in the apomictic species, while the sexual species presented much higher variability with no similar genotypes among the sampled trees. The results suggest that adventitious embryony in E. pubescens effectively results in clonal populations or population mosaics of clonal individuals. Since recent studies have indicated poly-embryony and possibly apomixis in a number of Cerrado woody species otherwise considered obligatorily allogamous, the RAPD results presented here indicate the technique will be a useful tool to detect clonal populations of apomictic origin among Cerrado woody species with mixed mating systems and will help to assess the importance of apomixis as a breeding system for the Cerrado flora. [source] | ||||||||||||||||||||||