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Paleogene flower-insect interactions and paleo-pollination processes are, in general, poorly understood and fossil evidence for such floral and faunal interactions are rarely reported. To shed light on angiosperm flower-insect interactions, we investigated several hundred fossil flowers and insects from the middle Eocene Fossil Lagerstätte of Eckfeld, Germany. During our work, we discovered a unique fossil Ludwigiaflower (bud) with in situ pollen. The ecological preferences (climate, biome, habitat, etc.) of extant Ludwigiaand the paleoecological configurations of the fossil plant assemblage support the taxonomic affiliation of the flower bud and an Eocene presence of Ludwigiain the vicinity of the former Lake Eckfeld. Today’s Ludwigiaare mostly pollinated by Hymenoptera (bees). Therefore, we screened all currently known hymenopteran fossils from Eckfeld but found no Ludwigiapollen adhering to any of the specimens. On the contrary, we discovered Ludwigiapollen adhering to two different groups of Coleoptera (beetles). Our study suggests that during the Eocene of Europe, Ludwigiaflowers were visited and probably pollinated by beetles and over time there was a shift in primary flower visitors/pollinators, from beetles to bees, sometime during the late Paleogene to Neogene.

The genus Delphinium (Ranunculaceae) consists of ca. 300 species and has a mainly holarctic distribution. Few species have been described from high-altitude areas in West and East Tropical Africa, where the environmental conditions are mostly temperate-like. We aim to clarify the taxonomy of these afro-montane Delphinium species and to understand their evolutionary history in terms of their floral morphology and their phylogenetic and biogeographic relationships. Based on herbarium specimens, we analyze flower shape variation, map the geographic distribution of the morphologically defined taxa and reconstruct the molecular phylogeny of the group. Our quantitative analyses of flower shapes indicate that three species can be defined based on floral morphological traits, hence confirming the latest taxonomic treatment of the group where D. dasycaulon, D. leroyi and D. macrocentrum were described. The examination of herbarium specimens indicates that these three species are almost parapatric. However, their respective monophyly is not supported by molecular data. Considering their relatively young age, the non-monophyly of each of the three morphospecies could be due to incomplete lineage sorting and/or hybridization events. Alternatively, the transition to the D. leroyi floral morph could be the result of evolutionary convergence in the two main groups of afro-montane Delphinium driven by similar pollinators in different sky islands of the East African Rift System. We hypothesize that the main branches of the East African Rift System, as physical barriers to dispersal, may have prevented genetic exchange among geographic clusters.

The sarracenioid families (Actinidiaceae, Roridulaceae, Sarraceniaceae) were rarely affiliated with other ericalean taxa in pre-molecular classifications and have seldom been considered closely related to each other. In molecular phylogenetic studies, the sarracenioids form a strongly supported clade and are sister to the ericoid clade (Clethraceae, Cyrillaceae, Ericaceae); the sarracenioids and ericoids together make up core Ericales. To date, no phylogenetic study has included all sarracenioid genera (Actinidia, Clematoclethraand Saurauiain Actinidiaceae; Roridulain Roridulaceae; Darlingtonia, Heliamphoraand Sarraceniain Sarraceniaceae). In particular, the monophyly of Saurauiahas not previously been tested using molecular characters. We shed light on the phylogenetic relationships within the sarracenioid clade and, based on ancestral state reconstructions, test floral characters previously suggested as potential synapomorphies for the sarracenioids and ericoids. Phylogenetic analysis was performed for the DNA regions ITS, rbcL, rpl32-trnL, trnKand trnL-Fusing RAxML, MrBayes and PAUP*. Our results support the monophyly of the sarracenioid clade as well as of all its families and non-monotypic genera. Two distinct geographical lineages are identified in Saurauia; the two lineages are characterised by differences in petal union (choripetaly versus sympetaly), style union (free versus partially united), gynoecium merism and base chromosome numbers. Our analyses identify the following floral characters as synapomorphic for core Ericales: adaxial anther attachment, anther inversion and a depression at the ovary-to-style transition. Proximally thick to massive petals, the presence of a nucellar hypostase in ovules and polystemony are synapomorphies of the sarracenioid clade. The presence of calcium oxalate raphides, mucilage cells, a secretory inner gynoecium surface and the absence of synlateral vasculature in the ovary are synapomorphies of the Actinidiaceae-Roridulaceae clade. A two-whorled androecium is a synapomorphy of the ericoid clade.

Based on nucleotide sequences from three chloroplast DNA regions (rps16, rpl16 , trnT-trnL), we infer detailed phylogenetic relationships within the subfamily Thunbergioideae (Acanthaceae) and among major lineages of the family as a whole. Taxa were sampled to cover the geographic distribution of Thunbergioideae and to include all subgenera of the largest genus Thunbergia. All other major lineages of Acanthaceae were sampled to test monophyly and intrafamilial position of Thunbergioideae. Both parsimony and Bayesian analyses support Thunbergioideae as monophyletic. The mangrove genus Avicenniais consistently placed as sister to Thunbergioideae although with only moderate support. Thunbergiaand Mendonciaare both monophyletic in all analyses, and Mendonciais placed as sister to Thunbergiaplus Pseudocalyx. Relationships within the two largest genera Mendonciaand Thunbergiaare highly resolved and most branches are strongly supported. Our results suggest that the existing morphology-based classification of Thunbergiapartially holds, but needs revision. Based on the phylogenetic relationships we found it likely that a twining habit is ancestral for the genus Thunbergia. The thecal awns, characteristic for many species in the genus, have probably evolved from unicellular bristles. Longitudinal dehiscence over the whole length of the thecae, which is present in many Thunbergiaspecies, most likely evolved from short slits or pores as present in Pseudocalyxand Mendoncia.

Floral structure and development of 18 species of Thunbergia(Thunbergioideae s.l., Acanthaceae) were studied comparatively. The flowers of Thunbergiaare highly diverse and show a wide range of pollination syndromes. In general they are large and showy. Their pollination apparatus is highly elaborate, floral organs are often synorganized, and floral architecture is complex. In contrast to the high diversity of the anthetic flowers, their bauplan is uniform and their early development shows no major differences, i.e. in all species studied, the calyx arises as a ring primordium, the corolla is «late sympetalous», and petals and stamens are initiated more or less simultaneously. Some differences are found in further calyx development, where several developmental patterns are present. More significant differences arise only later during development and mainly concern the structures of the calyx, the anthers, the stigma, and corolla aestivation. In the anthetic flowers there are many special characters that are present in all or the majority of the species studied, e.g. the calyx is reduced, the corolla tube is subdivided into two compartments and the anthers lack an endothecium. The present results on development and morphology of the flowers of Thunbergiaare compatible with an earlier subdivision of the genus into eight subgenera.

Floral structure and development of 18 species of Thunbergia(Thunbergioideae si, Acanthaceae) were studied comparatively. The flowers of Thunbergiaare highly diverse and show a wide range of pollination syndromes. In general they are large and showy. Their pollination apparatus is highly elaborate, floral organs are often synorganized, and floral architecture is complex. In contrast to the high diversity of the anthetic flowers, their bauplan is uniform and their early development shows no major differences, i.e. in all species studied, the calyx arises as a ring primordium, the corolla is ‘late sympetalous’, and petals and stamens are initiated more or less simultaneously. Some differences are found in further calyx development, where several developmental patterns are present. More significant differences arise only later during development and mainly concern the structures of the calyx, the anthers, the stigma, and corolla aestivation. In the anthetic flowers there are many special characters that are present in all or the majority of the species studied, e.g. the calyx is reduced, the corolla tube is subdivided into two compartments and the anthers lack an endothecium. The present results on development and morphology of the flowers of Thunbergiaare compatible with an earlier subdivision of the genus into eight subgenera.