Siring success and paternal effects in heterodichogamous Acer opalus.

BACKGROUND AND AIMS: Heterodichogamy (a dimorphic breeding system comprising protandrous and protogynous individuals) is a potential starting point in the evolution of dioecy from hermaphroditism. In the genus Acer, previous work suggests that dioecy evolved from heterodichogamy through an initial spread of unisexual males. Here, the question is asked as to whether the different morphs in Acer opalus, a species in which males co-exist with heterodichogamous hermaphrodites, differ in various components of male in fitness. METHODS: Several components of male fertility were analysed. Pollination rates in the male phase were recorded across one flowering period. Pollen viability was compared among morphs through hand pollinations both with pollen from a single sexual morph and also simulating a situation of pollen competition; in the latter experiment, paternity was assessed with microsatellite markers. It was also determined whether effects of genetic relatedness between pollen donors and recipients could influence the siring success. Finally, paternal effects occurring beyond the fertilization process were tested for by measuring the height reached by seedlings with different sires over three consecutive growing seasons. KEY RESULTS: The males and protandrous morphs had higher pollination rates than the protogynous morph, and the seedlings they sired grew taller. No differences in male fertility were found between males and protandrous individuals. Departures from random mating due to effects of genetic relatedness among sires and pollen recipients were also ruled out. CONCLUSIONS: Males and protandrous individuals are probably better sires than protogynous individuals, as shown by the higher pollination rates and the differential growth of the seedlings sired by these morphs. In contrast, the fertility of males was not higher than the male fertility of the protandrous morph. While the appearance of males in sexually specialized heterodichogamous populations is possible, even in the absence of a fitness advantage, it is not clear that males can be maintained at an evolutionary equilibrium with two classes of heterodichogamous hermaphrodites

Microsatellite segregation analysis and cytogenetic evidence for tetrasomic inheritance in the American yam Dioscorea tridifa and a new basic chromosome number in the Dioscoreae

International audienceDespite the economic and cultural importance of the indigenous “Amerindian” yam Dioscorea trifida, very little is known about their origin, phylogeny, diversity and genetics. Consequently, conventional breeding efforts for the selection of D. trifida genotypes resistant to potyviruses which are directly involved in the regression of this species have been seriously limited. Our objective of this paper is to contribute to the clarification of the cytogenetic status, i.e., inheritance and chromosome number. Our results provide genetic evidence supporting tetrasomic behaviour of the genome of D. trifida based on chromosomal segregation pattern analysis using eight SSRs markers in three different crosses. This is the first reliable evidence of an autopolyploid species in the genus Dioscorea. The second major result in this study is the revealing of a new base chromosome number in the botanical section Macrogynodium to which D. trifida belongs. To date, our assumptions about the ploidy level of yams are based on the observations that the basic chromosome number is 10 or 9, and D. trifida was described as octoploid. The chromosome number of D. trifida accessions was also assessed using somatic chromosomic count techniques. Flow cytometry did not show significant variation of 2C DNA content among 80 accessions indicating homogeneity of the ploidy level of the cultivated D. trifida. This suggests that autotetraploidy is well established as well as the rule for the cultivated pool of D. trifida, even if the direct diploid ancestor remains to be identified. The data presented in this paper are significant and important for the effective breeding and conservation of the species and for elucidating the phylogeny and the origins of the yam and the evolution of the genus Dioscorea

Local versus regional intraspecific variability in regeneration traits

7 páginas, 1 figura, 2 tablas.Intraspecific trait variability has a fundamental contribution to the overall trait variability. However, little is known concerning the relative role of local (e.g. disturbances and species interaction) and regional (biogeographical) processes in generating this intraspecific trait variability. While biogeographical processes enhance plant trait variability between distant populations, in fire-prone ecosystems, recurrent fires may have a preponderant role in generating variability at a local scale. We hypothesize that plants respond to the local spatio-temporal heterogeneity generated by fire by having a relatively large local variability in regeneration traits in such a way that overrides the variability at a broader biogeographical scale. We test this hypothesis by assessing the intraspecific variability in fire-related regeneration traits of two species (Cistus salviifolius and Lavandula stoechas) growing in fire-prone ecosystems of the Mediterranean Basin. For each species, we selected six populations in two distant regions, three in the east (Anatolian Peninsula) and three in the west (Iberian Peninsula). For each species and population, we analysed the following regeneration traits: seed size, seed dormancy and stimulated germination by fire-related cues (heat and smoke). To evaluate the distribution of the variability in these traits, we decomposed the variability of trait values at each level, between regions (regional) and between population within region (local), using linear mixed-effect models. Despite the biogeographical and climatic differences between regions, for the two species, intraspecific variability in regeneration traits was higher at a local (within regions) than at a regional scale (between regions). Our results suggest that, in Mediterranean ecosystems, fire is an important source of intraspecific variability in regeneration traits. This supports the prominent role of fire as an ecological and evolutionary process, producing trait variability and shaping biodiversity in fire-prone ecosystems.B.M. is supported by a grant from the Fundação para a Ciência e a Tecnologia SFRH/BD/41343/2007), and Ç.T. was supported by the Short Term ScientiWc Mission of European Cooperation in Science and Technology (COST) Action No: FP0701, European Commission (Post-Wre forest management in Southern Europe). We thank I. Fernandes for her help during the germination experiment and J. Messier for helpful comments on the manuscript. This work was supported by the Spanish project VIRRA (CGL2009-12048/BOS). CIDE is supported by Consejo Superior de Investigaciones Científicas (CSIC), Generalitat Valencia and the University of Valencia. The experiments performed in this article comply with the current laws of Spain and Turkey.Peer reviewe