Capturing variation in floral shape: a virtual3D based morphospace for Pelargonium.

BACKGROUND: Variation in floral shapes has long fascinated biologists and its modelling enables testing of evolutionary hypotheses. Recent comparative studies that explore floral shape have largely ignored 3D floral shape. We propose quantifying floral shape by using geometric morphometrics on a virtual3D model reconstructed from 2D photographical data and demonstrate its performance in capturing shape variation. METHODS: This approach offers unique benefits to complement established imaging techniques (i) by enabling adequate coverage of the potential morphospace of large and diverse flowering-plant clades; (ii) by circumventing asynchronicity in anthesis of different floral parts; and (iii) by incorporating variation in copy number of floral organs within structures. We demonstrate our approach by analysing 90 florally-diverse species of the Southern African genus Pelargonium (Geraniaceae). We quantify Pelargonium floral shapes using 117 landmarks and show similarities in reconstructed morphospaces for nectar tube, corolla (2D datasets), and a combined virtual3D dataset. RESULTS: Our results indicate that Pelargonium species differ in floral shape, which can also vary extensively within a species. PCA results of the reconstructed virtual3D floral models are highly congruent with the separate 2D morphospaces, indicating it is an accurate, virtual, representation of floral shape. Through our approach, we find that adding the third dimension to the data is crucial to accurately interpret the manner of, as well as levels of, shape variation in flowers.

Plastome based phylogenetics and younger crown node age in Pelargonium.

The predominantly South-African plant genus Pelargonium L'Hér. (Geraniaceae) displays remarkable morphological diversity, several basic chromosome numbers as well as high levels of organelle genomic rearrangements, and represents the 7th largest Cape Floristic Region clade. In this study, we reconstructed a phylogenetic tree based on 74 plastome exons and nuclear rDNA ITS regions for 120 species, which represents 43% taxon coverage for Pelargonium. We also performed a dating analysis to examine the timing of the major radiations in the genus. Phylogenetic analyses of nucleotide, amino acid, and ITS alignments confirmed the previously-documented subgeneric split into five main clades ((C1,C2),(B(A1,A2))) although clade only A1 received low bootstrap support. Using calibration evidence from a range of sources the Pelargonium crown age was estimated to be 9.7 My old, much younger than previous estimates for the genus but similar to recent studies of other Cape Floristic lineages that are part of both Fynbos and Succulent Karoo biomes.

Anatolian origins and diversification of Aethionema, the sister lineage of the core Brassicaceae.

PREMISE OF THE STUDY: The Irano-Turanian region harbors three biodiversity hotspots and ∼25% of Brassicaceae species are endemic to the region. Aethionema (∼61 species) is the sister lineage to the core Brassicaceae and occurs mainly in the Irano-Turanian region. The evolutionary important position of Aethionema makes it an ideal reference for broader comparative genetics and genomics. To understand the evolution of Aethionema, and for a broader understanding of crucifer evolution, a time-calibrated phylogenetic tree and biogeographical history of the genus is needed. METHODS: Seventy-six plastome coding regions and nuclear rDNA genes, mainly from herbarium material, covering 75% of all Aethionema species, were used to resolve a time-calibrated Aethionema phylogeny. The different clades were characterized based on four morphological characters. The ancestral area of Aethionema was estimated with historical biogeographical analyses. KEY RESULTS: Three well-supported major clades within Aethionema were resolved. The ancestral area reconstruction and divergence-time estimates are consistent with major dispersal events during the Pliocene from the Anatolian Diagonal. CONCLUSIONS: We find that most Aethionema lineages originated along the Anatolian Diagonal, a floristic bridge connecting the east to the west, during the Pliocene. The dispersal of Aethionema correlates with the local geological events, such as the uplift of the Anatolian and Iranian plateaus and the formation of the major mountain ranges of the Irano-Turanian region. Knowing the paleo-ecological context for the evolution of Aethionema, in addition to the other lineages of Brassicaceae, facilitates our broader understanding for trait evolution and species diversification across the Brassicaceae.