Multiple Events of Allopolyploidy in the Evolution of the Racemose Lineages in Prunus (Rosaceae) Based on Integrated Evidence from Nuclear and Plastid Data.

Prunus is an economically important genus well-known for cherries, plums, almonds, and peaches. The genus can be divided into three major groups based on inflorescence structure and ploidy levels: (1) the diploid solitary-flower group (subg. Prunus, Amygdalus and Emplectocladus); (2) the diploid corymbose group (subg. Cerasus); and (3) the polyploid racemose group (subg. Padus, subg. Laurocerasus, and the Maddenia group). The plastid phylogeny suggests three major clades within Prunus: Prunus-Amygdalus-Emplectocladus, Cerasus, and Laurocerasus-Padus-Maddenia, while nuclear ITS trees resolve Laurocerasus-Padus-Maddenia as a paraphyletic group. In this study, we employed sequences of the nuclear loci At103, ITS and s6pdh to explore the origins and evolution of the racemose group. Two copies of the At103 gene were identified in Prunus. One copy is found in Prunus species with solitary and corymbose inflorescences as well as those with racemose inflorescences, while the second copy (II) is present only in taxa with racemose inflorescences. The copy I sequences suggest that all racemose species form a paraphyletic group composed of four clades, each of which is definable by morphology and geography. The tree from the combined At103 and ITS sequences and the tree based on the single gene s6pdh had similar general topologies to the tree based on the copy I sequences of At103, with the combined At103-ITS tree showing stronger support in most clades. The nuclear At103, ITS and s6pdh data in conjunction with the plastid data are consistent with the hypothesis that multiple independent allopolyploidy events contributed to the origins of the racemose group. A widespread species or lineage may have served as the maternal parent for multiple hybridizations involving several paternal lineages. This hypothesis of the complex evolutionary history of the racemose group in Prunus reflects a major step forward in our understanding of diversification of the genus and has important implications for the interpretation of its phylogeny, evolution, and classification

Screening for broad mite susceptibility in Rhododendron simsii hybrids

Broad mite Polyphagotarsonemus latus, is a key pest of pot azalea (Rhododendron simsii Planch hybrids). No information on variation in susceptibility or potential tolerance within these plants is available to date. We evaluated a selection of 32 Rhododendron cultivars, mainly Rhododendron simsii hybrids, for susceptibility to broad mite. The plants were artificially infested in a greenhouse by surrounding each azalea with four broad mite-infested English ivy plants (Hedera helix). Broad mite infestation was evaluated by counting the number of broad mites per shoot tip and assigning a damage rate. Results indicated a comparable infestation rate expressed as the number of mites on all cultivars at the initial stage of the experiments. Correlations between the average damage rate and the number of broad mites per shoot tip on all cultivars at different time intervals were significantly positive, although low, in each experiment, with R-2-values of 0.14 and 0.61. At the end of the experiments significant differences in susceptibility between the evaluated cultivars were observed. The cultivars, 'Emil De Coninck' and 'Mont Blanc' were rated as the most susceptible, whereas 'Mistral' and its bud sport 'Elien' were tolerant towards the broad mite, because damage rates were low and very few broad mites were found

Ploidy variation in Rhododendron subsection Maddenia and its implications for conservation.

Polyploidy, which is common in plants, can confound taxon recognition and hence conservation assessments. In the taxonomically complex genus Rhododendron, 25 % of the over 1,300 taxa are considered under threat and 27 % Near Threatened or Data Deficient, with their taxonomy needing to be resolved urgently. Although ploidy levels of Rhododendron taxa range from diploid (2x) to dodecaploid (12x) according to previous reports, the extent of polyploidy across the genus has not been examined. We first summarized the taxonomic distribution of polyploids in the genus based on the literature. Then as a case study, we estimated ploidy levels of 47 taxa in subsection Maddenia (subgenus Rhododendron, section Rhododendron) using flow cytometry, together with verification of meiotic chromosome counts for representative taxa. The summary of reported ploidy in Rhododendron indicates that polyploidy is most common in subgenera Pentanthera and Rhododendron. In subsection Maddenia, all examined taxa are diploids except for the R. maddenii complex that shows a high ploidy variation (2-8x, 12x). We investigated ploidy level of 12 taxa in subsection Maddenia for the first time, and estimated genome sizes of two Rhododendron species. Knowledge of ploidy levels will inform phylogenetic analysis of unresolved species complexes. Overall, our study of subsection Maddenia provides a model for examining multiple issues including taxonomic complexity, ploidy variation and geographic distribution in relation to biodiversity conservation.fals

Trichome micromorphology in drupe of Amygdalus L. (Rosaceae) from Iran

For delimitation of species and systematic resolution, pericarp indumentum in drupes of 17 species and two hybrids of the genus Amygdalus L., representing two subgenera and two sections distributed in Iran, were studied using scanning electron microscopy (SEM) in order to assess whether in this genus, pericarp micromorphological characters are of taxonomic value. The pericarp indumentum type is velutinous with different density of trichomes. Glabrous pericarp was observed solely in A. reticulata Runemark ex Khatamsaz. All trichomes are simple. Two basic types of trichomes were distinguished on the surface of the pericarp: tubular and flattened. Among these, tubular trichomes are more frequent than other trichomes in most species except for A. kotschyi Boiss. et Hohen., A. eburnea Spach, A. spinosissima Bge. subsp. spinosissima and A. lycioides Spach var. lycioides. Density of trichomes was variable among the studied taxa. In the first subgenus (subgen. Amygdalus) with two sections, there was enough difference between sections. While density of trichomes in sect. Spartioides Spach was very low, most of species in the another section, sect. Amygdalus showed dense pericarp indumentum. Regarding density, the second subgenus, subgen. Dodecandra (Spach) Browicz showed dense indumentum. Two hybrids studied, A.´keredjensis Browicz and A.´kamiaranensis Khatamsaz et Assadi showed different pericarp indumenta, dense and sparse respectively. In conclusion, micromorphological investigation of pericarp indumentum in drupes is a useful tool for distinguishing taxa in some cases, especially those of the two sections in the first subgenus in Amygdalus

Distribution of sex forms in the phanerogamic flora

In the plant kingdom, particularly in the phanerogamic flora, hermaphroditism is by far the most common, yet the number of other sex forms is not negligible. This study was undertaken with the view of ascertaining the relative proportions in which such sex forms occur. For this purpose Engler and Prantls "Natürliche Pflanzenfamilien" with all the Nachträge (which are complete up to 1912) have been used. The lists that follow are the results of this examination

Rhododendron diversity conservation in global botanic gardens: A case study of Maddenia species

Effective ex situ conservation of plants in botanic gardens requires sufficient wild accessions to represent wild diversity. In Rhododendron L. (Ericaceae), c. 64% of the taxa are threatened or require field investigation. As a case study of the analysis of ex situ conservation gaps we used ecogeographical representation as a proxy for genetic representation in ex situ collections of the 65 taxa of Rhododendron subsection Maddenia. We compiled the first list profiling both wild distributions and ex situ wild collections of all taxa in subsection Maddenia. Our results reveal that 55 Maddenia taxa are in cultivation. Of the 18 threatened taxa all are in cultivation but nine require further collection to capture adequate wild diversity. There are 12 Data Deficient taxa: These await further field investigation of wild populations and nine of them require wild collections to conserve genetic diversity. The UK, the USA, Australia, New Zealand and China are the top five countries holding ex situ collections of subsection Maddenia; in these countries nearly 66% of the ex situ sites hold > 86% of the global living collections of subsection Maddenia. We recommend that wild collections of endemic species of subsection Maddenia should be established in all 10 countries of origin and that data should be shared internationally for metacollections. In addition to proposing priorities, our case study highlights the challenges facing data and collection management to help achieve effective ex situ conservation for Rhododendron species.fals

Polyploidy, Phylogeny, and Morphology of <i>Rhododendron's</i> (Ericaceae) 'Hardy Mountaineers' from the Hengduan-Himalayan Mountain Region

Mountain systems have long served as hotspots of plant diversification, where complex evolutionary processes can obscure species boundaries and phylogenetic relationships. This dissertation investigated the evolutionary history, polyploidy, and morphological diversification of Rhododendron (Ericaceae) subsection Lapponica and closely related taxa in section Rhododendron, a group that dominates alpine ecosystems in the Himalaya and Hengduan Mountains. By integrating chloroplast phylogenomics, nuclear target-capture sequencing, and quantitative morphological analyses, I examined how geography, ploidy, and morphology relate to species' relationships in this taxonomically challenging group. In Chapter 2, plastome phylogenies from across section Rhododendron revealed frequent discordance with traditional taxonomy. At broad phylogenetic scales, plastid similarity correlated significantly with both geography and ploidy—marking the first reported association between plastome variation and ploidy level in Rhododendron. At finer phylogenetic scales, geographic proximity more often predicted chloroplast similarity than morphological species identity, suggesting geographically structured chloroplast capture via hybridization. Although many species’ relationships within section Rhododendron remained unresolved, a set of diploid taxa formed strongly supported monophyletic clades, offering key reference points for interpreting maternal lineage structure and reproductive isolation. Chapter 3 employed nuclear target-capture sequencing to infer phylogenomic relationships within subsection Lapponica. The clade was resolved as monophyletic, and several diploid species received strong support. However, polyploid taxa frequently clustered by ploidy level rather than by taxonomic species identity, potentially reflecting widespread gene flow, hybridization, and independent origins of polyploid lineages. Cytonuclear discordance was particularly pronounced in polyploid clusters, providing additional evidence for geographic chloroplast capture and reticulate evolutionary histories. Chapter 4 examined whether floral and vegetative morphology corresponded to species boundaries, and similarly, whether clades supported by the nuclear phylogeny in Lapponica aligned with morphological groupings. Morphometric analyses showed substantial overlap in trait values across taxa, with most floral traits offering little taxonomic resolution or phylogenetic signal. Stamen length was the only trait to exhibit consistent and statistically significant phylogenetic conservatism, likely reflecting constraints tied to pollination function. In contrast, floral shape factor traits appeared evolutionarily labile and were not strongly structured by phylogeny. Multilevel linear models showed that ploidy and elevation had minimal influence on floral trait variation. Together, these findings demonstrated that evolutionary patterns in Rhododendron, especially subsection Lapponica, were shaped by a complex interplay of polyploidy, geography, and hybridization, while traditional morphological characters contributed limited resolution for taxonomic or phylogenetic inference. This work uncovered new polyploid information for previously unexamined taxa, clarified some species-level relationships within a dominant alpine shrub lineage, and highlighted the importance of genomic and quantitative approaches in understanding recent and reticulate plant radiations in montane biodiversity hotspots

Understanding Rhododendron intraspecific compatibility in botanic garden collections for species conservation

Context Controlled pollination is an important technique for maintaining intraspecific diversity in integrated plant conservation practices, particularly in genera such as Rhododendron, where open pollination usually produces hybrids with unknown paternal lineages. Aims This study investigated the capacity for viable seed set from self- and intraspecific cross-pollination for Rhododendron taxa in different categories of the International Union for Conservation of Nature (IUCN) Red List, to guide conservation management of threatened species in botanic garden collections. Methods The following five taxa of subsection Maddenia were studied: R. dalhousiae var. dalhousiae (Least Concern), R. dalhousiae var. rhabdotum (Vulnerable), R. lindleyi (Least Concern), R. nuttallii (Near Threatened), and R. excellens (Vulnerable). Controlled pollination was performed on selected garden accessions, and seed germination was tested at an alternating temperature regime of 15/25°C, 8 h photoperiod, and ~6 μmol m−2 s−1 photosynthetic photon flux density (PPFD). Key results Intraspecific compatibilities varied among different taxa and between self- and outcross treatments. X-ray images for Rhododendron seeds showed low capacity to predict seed germination. Neither X-ray scan nor fungicide (Ridomil) treatment showed any adverse impact on seed germination, which has positive implications for seed-banking and subsequent raising of Rhododendron seedlings. Conclusions Controlled intraspecific pollination can be used to maintain diversity of ex situ accessions for selected Rhododendron species. However, the zero or low compatibility demonstrated in some species, such as R. excellens, suggests that these species may require a different approach. Implications Intraspecific pollination should be evaluated for each Rhododendron species before a propagation program is initiated in ex situ conservation.fals

New remains of Astraponotus (Mammalia, Astrapotheria) and considerations on Astrapothere cranial evolution

Astraponotus Ameghino, 1901, the only valid Mustersan (late Eocene) astrapothere, typifies the Ameghino’s ‘‘Capas Astraponotenses’’. This taxon is traditionally interpreted as structurally ancestral to all the Oligocene– Miocene astrapotheriids. However, it was imperfectly known: only isolated teeth and very partial mandibles have hitherto been described. In this contribution we provide the first description of the skull, mandible, and complete dentition of Astraponotus based on new materials from the Gran Hondonada and other Mustersan localities in central Patagonia, Argentina. The features observed in the dentition of Astraponotus are intermediate between the Casamayoran (middle Eocene) and the Oligocene–Miocene astrapotheres in the degree of hypsodonty, reduction of the dental formula, and development of accessory occlusal elements. Concordantly, the skull retains some plesiomorphies, also observed in Trigonostylops, whereas the auditory region and the basicranium are much closer to those of Parastrapotherium, Astrapotherium, and Granastrapotherium. On the other hand, the skull of Astraponotus differs from all known astrapotheres by the disproportioned height and narrowness of the braincase, the extreme reduction of the nasals and the premaxillaries, the absence of anteorbital rim, and the reduction of the frontal region. Some of these features represent cranial specializations exactly opposite to that of Astrapotherium. These characters look astonishingly derived for an Eocene astrapothere, suggesting that extreme cranial specializations occurred independently during the evolution of the order, and that Astraponotus represents a distinctive lineage from that of Astrapotherium and other Miocene forms.Fil: Kramarz, Alejandro Gustavo. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. División Paleontología Vertebrados; Argentina. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. División Paleontología Vertebrados; ArgentinaFil: Bond, Mariano. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; Argentina. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. División Paleontología Vertebrados; ArgentinaFil: Forasiepi, Analia Marta. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. División Paleontología Vertebrados; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; Argentin