Search Results (3)

The term “Geographical parthenogenesis” describes the phenomenon that asexual organisms usually occupy larger and more northern distribution areas than their sexual relatives, and tend to colonize previously glaciated areas. Several case studies on alpine and arctic plants confirm the geographical pattern, but the causal factors behind the phenomenon are still unclear. Research of the last decade in several plant families has shed light on the question and evaluated some of the classical evolutionary theories. Results confirmed, in general, that the advantages of uniparental reproduction enable apomictic plants to re-colonize faster in larger and more northern distribution areas. Associated factors like polyploidy seem to contribute mainly to the spatial separation of sexual and asexual cytotypes. Ecological studies suggest a better tolerance of apomicts to colder climates and temperate extremes, whereby epigenetic flexibility and phenotypic plasticity play an important role in occupying ecological niches under harsh conditions. Genotypic diversity appears to be of lesser importance for the distributional success of asexual plants. Classical evolutionary theories like a reduced pressure of biotic interactions in colder climates and hence an advantage to asexuals (Red Queen hypothesis) did not gain support from studies on plants. However, it is also still enigmatic why sexual outcrossing remains the predominant mode of reproduction also in alpine floras. Constraints for the origin of apomixis might play a role. Interestingly, some studies suggest an association of sexuality with abiotic stresses. Light stress in high elevations might explain why most alpine plants retain sexual reproduction despite other environmental factors that would favor apomixis. Directions for future research will be given. Full article

We assessed, for the first time, the plant assemblages in coniferous forests of temperate and alpine ecosystems of the Himalayas to understand the diversity of species and their phenological behaviours that lead to different growth forms in the climax forest community. In this study, we selected the coniferous forests of Bhallesa Hills, situated in Pir Panjal Mountain (Jammu and Kashmir) of the Himalayan biodiversity hotspot as a study area and used the quadrat method to document the floristic diversity over four years (2018–2021). The study sites were divided into four sub-sites (Chilli, Kahal, Chanwari, Gandoh), and at each site, 25 replicated plots (each measuring 2500 m², 50 × 50 m²) were established for repeated surveys and documentation. We then analysed species diversity, lifeforms, phenology and leaf size spectra of coniferous plant communities. We consulted various pieces of literature to understand native and non-native plants. The results showed that the species diversity and species richness, growth forms and phenology varied in the experimental plots. In total, we found 328 plant species belonging to 228 genera and 78 families from different localities of various growth forms. Approximately 68.51% of the plant species were native, and 31.49%of the species were non-native. In angiosperms, dicotyledon species were found to be dominant, with 83.23% of the total plant species, while the family Asteraceae was common, with 38 species. The biological spectrum analysis showed 29% of the species were chamaephytes, followed by 28% as therophytes and 21% as phanerophytes. We observed that plant communities respond differently to the existing environment drivers, with chamaephyte and therophytes being more tightly linked to temperate mixed-coniferous and alpine ecosystems, affected by climates and the availability of substrates for their growth and existence. The leaf size spectra analyses showed nanophyll (42.81%) as the dominant group. Conservation-prioritised species (IUCN, regional most threatened species in India), such as Taxus wallichiana Zucc., Picrorhiza kurroa Royle ex Benth., Trillium govanianum Wall. ex D.Don, Aconitum heterophyllum Wall. ex Royle and Euphorbia obovata Decne were found to be the most endangered plants. The results indicated more indigenous species, but there is a slow process of depletion of wild species, leading to colonisation by exotic alien species. This study indicated forests of the Himalayan regions are degrading at a faster rate, species are showing a shift in phenological behaviour due to anthropogenic factors leading to climate change, and indigenous species need conservation measures. Full article

Yunnan has a complicated geological history, a particular geography, and a complex topography, which have influenced the formation of various habitats of high biodiversity: 245 families; 2140 genera; 13,253 species and varieties of seed plants; more than 12 types of vegetation; and 167 plant formations, including tropical rain forests, tropical dry forests, subtropical evergreen broad-leaved forest, cold temperate coniferous forests, and alpine bushes and meadows. An analysis of the geographic elements to the current Yunnan flora shows that the tropical distribution contributed to 51% of all families and to 57.5% of all genera, of which the genera from the tropical Asian distribution make up the highest proportion among all geographical elements. During the late evolution of Yunnan, its flora was strongly affected by the tropical Asian flora. The complicated patterns and diversity in Yunnan flora and vegetation have been shaped mainly by its particular geological histories, which include the differential uplifts in topography, the clock-wise rotation of the Simao-Lanping geoblock, and the extrusion of the Indochina geoblock by the Himalayan uplift. The flora and vegetation of Yunnan were possibly derived from tropical-subtropical Tertiary flora before later diverging. Northwestern Yunnan flora likely evolved due to rapid speciation from families and genera from cosmopolitan and northern temperate distributions during the uplift of the Himalayas and climatic oscillations after the late Tertiary. Southern Yunnan flora likely evolved into tropical Asian flora following the southeastward extrusion of the Indochina block, which brought along tropical Asian elements. Central Yunnan flora inherited most of the elements of the Tertiary flora from East Asia. The formation and strengthening of the southwest monsoon by the uplift of the Himalayas was also a direct factor in the formation of the tropical rain forests found in southern Yunnan. The flora from southern and southeastern Yunnan also diverged, with the former being more closely related to Indo-Malaysian flora and the latter being more closely related to Eastern Asian flora. This floristic divergence is well supported by the geological history of these regions: that is, the tropical flora of southeastern Yunnan derived from the South China geoblock, whereas the flora of southern and southwestern Yunnan mainly derived from the Shan-Thai geoblock. Full article