Increasing evidence suggests that specific interactions between microbial decomposers and plant litter, named home‐field advantage (HFA), influence litter breakdown. However, we still have limited understanding of whether HFA relates to specific microbiota, and whether specialized microbes originate from the soil or from the leaf microbiome. Here, we disentangle the roles of soil origin, litter types and the microbial community already present on the leaf litter in determining fungal community composition on decomposing leaf litter and HFA. We collected litters and associated soil samples from a secondary succession gradient ranging from herbaceous vegetation on recently abandoned ex‐arable fields to forest representing the end stage of succession. In a greenhouse, sterilized and unsterilized leaf litters were decomposed for 12 months in soils from early‐ to late‐successional stages according to a full‐factorial design. At the end, we examined fungal community composition on the decomposing litter. Fungal communities on decomposed late‐successional litter in late‐successional soil differed from those in early‐ and mid‐successional stage litter and soil combinations. Soil source had the strongest impact on litter fungal composition when using sterilized litter, while the impact of litter type was strongest when using unsterilized litter. Overall, we observed HFA, as litter decomposition was accelerated in home soils. Increasing HFA did not relate to the dissimilarity in overall fungal composition, but there was increasing dissimilarity in the relative abundance of the most dominant fungal taxon between decomposing litter in home and away soils. We conclude that early‐, mid‐ and late‐succession litter types did not exert strong selection effects on colonization by micro‐organisms from the soil species pool. Instead, fungal community composition on decomposing litter differed substantially between litter types for unsterilized litter, suggesting that the leaf microbiome, either directly or indirectly, is an important determinant of fungal community composition on decomposing leaves. HFA related most strongly to the abundance of the most dominant fungal taxa on the decomposing litter, suggesting that HFA may be attributed to some specific dominant fungi rather than to responses of the whole fungal community. A plain language summary is available for this article.

Plants respond to herbivore attack by rapidly inducing defenses that are mainly regulated by jasmonic acid (JA). Due to the systemic nature of induced defenses, attack by root herbivores can also result in a shoot response and vice versa, causing interactions between above- and belowground herbivores. However, little is known about the molecular mechanisms underlying these interactions. We investigated whether plants respond differently when roots or shoots are induced. We mimicked herbivore attack by applying JA to the roots or shoots of Brassica oleracea and analyzed molecular and chemical responses in both organs. In shoots, an immediate and massive change in primary and secondary metabolism was observed. In roots, the JA-induced response was less extensive and qualitatively different from that in the shoots. Strikingly, in both roots and shoots we also observed differential responses in primary metabolism, development as well as defense specific traits depending on whether the JA induction had been below- or aboveground. We conclude that the JA response is not only tissue-specific but also dependent on the organ that was induced. Already very early in the JA signaling pathway the differential response was observed. This indicates that both organs have a different JA signaling cascade, and that the signal eliciting systemic responses contains information about the site of induction, thus providing plants with a mechanism to tailor their responses specifically to the organ that is damaged.

In order to gain insight into the causes of parapatric diploid and tetraploid distributions in Plantago media chloroplast DNA (cpDNA) restriction site polymorphism was studied in 36 European populations. Parapatric distributions are often explained by adaptive differences between cytotypes to an underlying heterogeneity in environmental factors. Alternatively, such distribution patterns may be explained nonadaptively, through frequency‐dependant production of hybrids with low fitness. However, nonadaptive explanations have been neglected in polyploid literature. In this study nine chloroplast haplotypes were found. Their phylogeny suggests that tetraploids arose at least three times from diploids. In general, related haplotypes were also geographically clustered, although there were some marked geographical discontinuities. In the Pyrenees, diploids and tetraploids carried diverged haplotypes throughout their parapatric ranges. At the contact zone the level of cpDNA introgression in a mixed diploid‐tetraploid population was low. It is discussed that the cpDNA phylogeography supports the nonadaptive hypothesis that parapatric cytotype distributions may be explained by postPleistocene range expansions followed by mutual minority cytotype exclusion, due to hybrid unfitness.

Some dandelions are diplosporous gametophytic apomicts. In order to study the inheritance and breakdown of apomixis, crosses were made between diploid sexuals and triploid apomicts. To investigate their breeding system, four nonapomictic diploid and 10 nonapomictic triploid hybrids were pollinated with diploids and the progenies were analysed. Seed fertility was signi®cantly reduced in two diploid hybrids. Nine triploid hybrids were fertile and could be classi®ed into three types, with respect to the composition of their progenies. Type A produced n+n hybrids. Type B produced either a mixture of n + n and 2n + n hybrids, or a mixture of pseudogamous 2n + 0 apomicts and 2n + n hybrids. Type C produced exclusively 2n + n hybrids. Inheritance of a microsatellite marker strongly suggested that 2n egg cells in type C plants were produced by a ®rst division restitution mechanism. As in apomicts, microsporogenesis in type C plants was reductional. This suggests that type C plants are diplosporous plants that lack parthenogenesis. Such plants are very rare in other apomictic plant species. It is concluded that`elements of apomixis', diplospory and parthenogenesis, can be uncoupled. This is inconsistent with the single-locus model for apomixis in Taraxacum as suggested by Mogie (1992). Instead, our results suggest that several loci are involved in the genetic control of apomixis in Taraxacum.Keywords: 2n-gametes, apomixis, diplospory, parthenogenesis, pseudogamy, Taraxacum. IntroductionIn apomictic plants seeds are produced asexually (Nogler, 1984; Asker & Jerling, 1992; Mogie, 1992; Koltunow, 1993). Apomictic seed development diers in at least three elements from sexual seed development: (i) avoidance of meiotic reduction; (ii) avoidance of fertilization; and (iii) parthenogenetic embryo development. This results in the production of 2n + 0 maternal ospring, instead of n + n sexual ospring (using the terminology of Harlan & DeWet, 1975). In most apomicts, the endosperm is formed sexually, after fertilization of the central cell of the embryo sac (pseudogamy). In autonomous apomicts, such as dandelions, Taraxacum, however, the endosperm develops autonomously. In this paper we report on the breakdown of apomixis in Taraxacum into its elements.Apomixis is a complex developmental trait and the prevailing opinion has for long been that the elements of apomixis are controlled by independent genes. In order to understand the genetics of apomixis, these elements should be analysed separately in crosses (Asker, 1980; Nogler, 1984). However, the extreme rarity of apomictic recombinants (either producing exclusively 2n + n hybrids or producing exclusively n + 0 polyhaploids) has raised doubts about the independent genetic control of elements of apomixis (Asker & Jerling, 1992). In their monograph on apomixis in plants, Asker & Jerling (1992) cite only three cases of plants producing exclusively 2n + n hybrids: Parthenium argentatum (Powers, 1945), Potentilla argentea (Asker, 1970) and Ranunculus auricomus (Nogler, 1984). Furt...

Some dandelions are diplosporous gametophytic apomicts. In order to study the inheritance and breakdown of apomixis, crosses were made between diploid sexuals and triploid apomicts. To investigate their breeding system, four nonapomictic diploid and 10 nonapomictic triploid hybrids were pollinated with diploids and the progenies were analysed. Seed fertility was signi®cantly reduced in two diploid hybrids. Nine triploid hybrids were fertile and could be classi®ed into three types, with respect to the composition of their progenies. Type A produced n+n hybrids. Type B produced either a mixture of n + n and 2n + n hybrids, or a mixture of pseudogamous 2n + 0 apomicts and 2n + n hybrids. Type C produced exclusively 2n + n hybrids. Inheritance of a microsatellite marker strongly suggested that 2n egg cells in type C plants were produced by a ®rst division restitution mechanism. As in apomicts, microsporogenesis in type C plants was reductional. This suggests that type C plants are diplosporous plants that lack parthenogenesis. Such plants are very rare in other apomictic plant species. It is concluded that`elements of apomixis', diplospory and parthenogenesis, can be uncoupled. This is inconsistent with the single-locus model for apomixis in Taraxacum as suggested by Mogie (1992). Instead, our results suggest that several loci are involved in the genetic control of apomixis in Taraxacum.Keywords: 2n-gametes, apomixis, diplospory, parthenogenesis, pseudogamy, Taraxacum. IntroductionIn apomictic plants seeds are produced asexually (Nogler, 1984; Asker & Jerling, 1992; Mogie, 1992; Koltunow, 1993). Apomictic seed development di ers in at least three elements from sexual seed development: (i) avoidance of meiotic reduction; (ii) avoidance of fertilization; and (iii) parthenogenetic embryo development. This results in the production of 2n + 0 maternal o spring, instead of n + n sexual o spring (using the terminology of Harlan & DeWet, 1975). In most apomicts, the endosperm is formed sexually, after fertilization of the central cell of the embryo sac (pseudogamy). In autonomous apomicts, such as dandelions, Taraxacum, however, the endosperm develops autonomously. In this paper we report on the breakdown of apomixis in Taraxacum into its elements.Apomixis is a complex developmental trait and the prevailing opinion has for long been that the elements of apomixis are controlled by independent genes. In order to understand the genetics of apomixis, these elements should be analysed separately in crosses (Asker, 1980; Nogler, 1984). However, the extreme rarity of apomictic recombinants (either producing exclusively 2n + n hybrids or producing exclusively n + 0 polyhaploids) has raised doubts about the independent genetic control of elements of apomixis (Asker & Jerling, 1992). In their monograph on apomixis in plants, Asker & Jerling (1992) cite only three cases of plants producing exclusively 2n + n hybrids: Parthenium argentatum (Powers, 1945), Potentilla argentea (Asker, 1970) and Ranunculus auricomus (Nogler, 1984). F...