Lepidium sensu stricto (s.s.) (Brassicaceae) (ca. 150 species) is distributed worldwide with endemic species on every continent. It is represented in Australia and New Zealand by 19 and seven native species, respectively. In the present study we used a nuclear ribosomal internal transcribed spacer (ITS) phylogeny in comparison with a cpDNA phylogeny to unravel the origin of Australian/New Zealand species. Although phylogenetic relationships within Lepidium s.s. were not fully resolved, the cpDNA data were in agreement with a Californian origin of Lepidium species from Australia/New Zealand. Strongly conflicting signals between the cp- and nuclear DNA phylogenetic analysis clearly indicated hybridogenous genomic constitution of Australian Lepidium s.s. species: All 18 studied Australian/New Zealand Lepidium s.s. species examined shared a Californian cpDNA type. While eleven Australian/New Zealand species appeared to harbor a Californian ITS type, a group of seven species shared a South African ITS type. This pattern is most likely explained by two trans-oceanic dispersals of Lepidium from California and Africa to Australia/New Zealand and subsequent hybridization followed by homogenization of the ribosomal DNA either to the Californian or South African ITS type in the two different lineages. Calibration of our molecular trees indicates a Pliocene/Pleistocene origin of Lepidium in Australia/New Zealand. Low levels of cpDNA and ITS sequence divergence and unresolved topologies within Australian/New Zealand species suggest a rapid and recent radiation of Lepidium after the hybridization event. This coincides with dramatic climatic changes in that geological epoch shaping the composition of the vegetation.

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17 18Consistent, repeatable segregation of plant species along hydrological 19 gradients is an established phenomenon that must in some way reflect a trade-off 20 between plants' abilities to tolerate the opposing constraints of drought and 21waterlogging. In C 3 species tissue carbon isotope discrimination (δ 13 C) is known to 22 vary sensitively in response to stomatal behaviour, reflecting stomatal limitation of 23 photosynthesis during the period of active growth. However, this has not been studied 24 at fine-spatial scale in natural communities. We tested how δ 13 C varied between 25 species and sexes of individuals in the family Restionaceae growing along a 26 monitored hydrological gradient. 20 Restionaceae species were investigated using 27 species-level phylogeny at two sites in the Cape Floristic Region, a biodiversity 28 hotspot. A spatial overlap analysis showed the Restionaceae species segregated 29 significantly (p<0.001) at both sites. Moreover, there were significant differences in 30 δ 13 C values among the Restionaceae species (p<0.001) and between male and female 31 individuals of each species (p<0.01). However, after accounting for phylogeny, 32 species δ 13 C values did not show any significant correlation with the hydrological 33 gradient. We suggest that some other variable (e.g. plant phenology) could be 34 responsible for masking a simple response to water availability. 35 36

The floral development of a number of representative genera of the Willdenowia clade of Restionaceae was studied to understand patterns of reduction of floral elements and sample evidence for discussing the relationships of the group. All species studied are characterized by a concordant reductive trend involving the retardation/reduction of the perianth, the loss of the anterior carpel and the displacement of the remaining carpels, linked with a strongly compressed spikelet. Different modes of carpel reduction, such as a progressive or immediate loss, or fusion of two neighboring carpels, are presented and discussed. The most parsimonious event of gynoecium evolution for the Willdenowia clade is either the sterilization of two carpels in an originally trimerous gynoecium, followed by the loss of the anterior carpel, or the sudden loss of the anterior carpel, preceeding the sterilization of one lateral carpel. The concordant development of the taxa of the Wi//denowia clade supports a one-time loss of a carpel and the homogeneity of the clade.

The species-rich genus Carex (Cyperaceae) is one of the 7% of angiosperm genera containing dioecious species. Dioecy is rare in Carex, only 12 spp. out of the 1,776 recorded taxa having been identified as dioecious. This paper focuses on Carex davalliana and C. dioica, the two dioecious species recorded in Europe. We investigated the nuclear (ITS) and chloroplast (trnTLF, rpl16) phylogenies of European Carex and identified incongruence in the phylogenetic history of both C. davalliana and C. dioica. This incongruence probably resulted from hybridisation. We postulate that dioecism was generated from hybridisation between species of opposite inflorescence morphologies (androgynous vs. gynaecandrous). We discuss the advantages of the separation of genders, taking into account the low number of dioecious species in the genus.