Georg Zizka

Phylogenetics, ancestral state reconstruction, and a new infrafamilial classification of the pantropical Ochnaceae (Medusagynaceae, Ochnaceae s.str., Quiinaceae) based on five DNA regions

Ochnaceae s.str. (Malpighiales) are a pantropical family of about 500 species and 27 genera of almost exclusively woody plants. Infrafamilial classification and relationships have been controversial partially due to the lack of a robust phylogenetic framework. Including all genera except Indosinia and Perissocarpa and DNA sequence data for five DNA regions (ITS, matK, ndhF, rbcL, trnL-F), we provide for the first time a nearly complete molecular phylogenetic analysis of Ochnaceae s.l. resolving most of the phylogenetic backbone of the family. Based on this, we present a new classification of Ochnaceae s.l., with Medusagynoideae and Quiinoideae included as subfamilies and the former subfamilies Ochnoideae and Sauvagesioideae recognized at the rank of tribe. Our data support a monophyletic Ochneae, but Sauvagesieae in the traditional circumscription is paraphyletic because Testulea emerges as sister to the rest of Ochnoideae, and the next clade shows Luxemburgia+Philacra as sister group to the remaining Ochnoideae. To avoid paraphyly, we classify Luxemburgieae and Testuleeae as new tribes. The African genus Lophira, which has switched between subfamilies (here tribes) in past classifications, emerges as sister to all other Ochneae. Thus, endosperm-free seeds and ovules with partly to completely united integuments (resulting in an apparently single integument) are characters that unite all members of that tribe. The relationships within its largest clade, Ochnineae (former Ochneae), are poorly resolved, but former Ochninae (Brackenridgea, Ochna) are polyphyletic. Within Sauvagesieae, the genus Sauvagesia in its broad circumscription is polyphyletic as Sauvagesia serrata is sister to a clade of Adenarake, Sauvagesia spp., and three other genera. Within Quiinoideae, in contrast to former phylogenetic hypotheses, Lacunaria and Touroulia form a clade that is sister to Quiina. Bayesian ancestral state reconstructions showed that zygomorphic flowers with adaptations to buzz-pollination (poricidal anthers), a syncarpous gynoecium (a near-apocarpous gynoecium evolved independently in Quiinoideae and Ochninae), numerous ovules, septicidal capsules, and winged seeds with endosperm are the ancestral condition in Ochnoideae. Although in some lineages poricidal anthers were lost secondarily, the evolution of poricidal superstructures secured the maintenance of buzz-pollination in some of these genera, indicating a strong selective pressure on keeping that specialized pollination system.

Chromosome numbers of the flora of Germany—a new online database of georeferenced chromosome counts and flow cytometric ploidy estimates

Abstract Chromosomal speciation processes gain increasing attention in plant systematics and evolution, and new approaches revealed a high diversity in chromosome numbers even within recognized taxa. Reliable counts linked to known accessions are thus needed yet often hardly available. We present a new online database for chromosome counts and ploidy estimates of the flora of Germany with a detailed documentation of the examined material, and its sampling locality. The chromosome database builds upon a relational database and includes standardized taxon identification, study date, georeferenced locality and additional collection as well as publication details from which the karyological information was extracted. In order to reach the best compatibility with other botanical publications of the study region, taxonomic concepts and nomenclature follow the “Rothmaler”, a widely accepted field flora of vascular plants in Germany. Our online database is available at http://chromosomes.senckenberg.de. The site consists of the main page with project information, a search tool, an interactive map display, a contact and a data submission form. The zoomable map shows the localities of the search result, allows to refine the geographic search as well as to select individual data points.

Taxonomic diversity masks leaf vein–climate relationships: lessons from herbarium collections across a latitudinal rainfall gradient in West Africa

Abstract Cross-biome data suggest that leaf venation density increases with decreasing moisture availability. If leaf venation traits were related to climatic conditions in such a predictable manner, these traits could serve, for example, as proxies for the reconstruction of past climates from fossil leaf remnants. However, our knowledge on vein–climate relationships is still scarce and relationships are poorly understood, particularly concerning broad-scale patterns in tropical regions. In this study, based on phylogenetic generalized least squares regression, we analysed leaf venation traits together with climatic niche data from 238 herbarium specimens to infer trait–trait and trait–climate relationships along a strong north–south rainfall gradient crossing West African savannas. Variation in leaf venation traits was strong along the climate gradient, yet vein–climate relationships were weak overall. This is in contrast to our expectation from the strong adaptive forces operating in drought-adapted vegetation covered by the gradient. On the other hand, several common patterns including intervein and vein–leaf size relationships were confirmed. A key finding was that while trait–climate relationships were mostly weak, some of these relationships became stronger when breaking down the entire taxon assemblage into smaller family-level units. This suggests that vein traits underlie partially opposing constraints in different clades, a pattern that is likely to become stronger with increasing higher-rank taxonomic diversity of species assemblages.

Heteroploid reticulate evolution and taxonomic status of an endemic species with bicentric geographical distribution.

Campanula baumgartenii is an endemic species of the polyploid complex Campanula section Heterophylla with a peculiar bicentric distribution. C. baumgartenii often grows in sympatry with other morphologically similar Campanula species (C. rotundifolia). Hence its species status has been doubtful. Using a multimethodological approach we confirmed the species status of C. baumgartenii and uncovered complex patterns of genetic and ploidal variability. These were identified as resulting from dynamic and ongoing evolutionary processes including several hybridization and backcrossing events. This study also illustrates that detailed population genetic studies can provide a solid basis for sound identification of conservation targets.

Phylogenetic relationships among Ananas and related taxa (Bromelioideae, Bromeliaceae) based on nuclear, plastid and AFLP data

Since the first description of the genus in 1754, the taxonomy of Ananas underwent many fundamental changes and it is still the subject of a vivid debate. We present a phylogeny comprising all seven known Ananas taxa, Pseudananas sagenarius as well as closely related members of Bromelioideae (Aechmea subg. Chevaliera) based on three nuclear markers (agt1, ETS, phyC), five plastid markers (atpB–rbcL, trnL–trnF, matK, two segments of ycf1) and AFLP data. This study reveals a close relationship between Ananas, P. sagenarius, Aechmea tayoensis and Disteganthus basilateralis, and proposes novel relationship of the Ananas clade and Aechmea fernandae. Taxonomic implications of our analysis in particular the recognition of species versus varieties in Ananas are discussed. Furthermore, we could show that the evolution of two traits (scape bracts and the apical coma of the inflorescence) might be interlinked.