Plant apomixis is rare in Himalayan high-alpine flora

Abstract

Gametophytic apomixis is a way of asexual plant reproduction by seeds. It should be advantageous under stressful high altitude or latitude environment where short growing seasons, low temperatures, low pollinator activity or unstable weather may hamper sexual reproduction. However, this hypothesis remains largely untested. Here, we assess the reproductive mode in 257 species belonging to 45 families from the world’s broadest alpine belt (2800–6150 m) in NW Himalayas using flow cytometric seed screen. We found only 12 apomictic species, including several members of Poaceae (Festuca, Poa and Stipa), Rosaceae (Potentilla) and Ranunculaceae (Halerpestes, Ranunculus), which are families typical for high apomict frequency. However, several apomictic species were newly discovered, including the first known apomictic species from the family Biebersteiniaceae (Biebersteinia odora), and first apomicts from the genera Stipa (Stipa splendens) and Halerpestes (Halerpestes lancifolia). Apomicts showed no preference for higher elevations, even in these extreme Himalayan alpine habitats. Additional trait-based analyses revealed that apomicts differed from sexuals in comprising more rhizomatous graminoids and forbs, higher soil moisture demands, sharing the syndrome of dominant species with broad geographical and elevation ranges typical for the late-successional habitats. Apomicts differ from non-apomicts in greater ability of clonal propagation and preference for wetter, more productive habitats.

Breeding system of diploid sexuals within theRanunculus auricomuscomplex and its role in a geographical parthenogenesis scenario

“…Although differential niche dynamics, the occurrence of apomictic conspecifics, and ecological preferences can explain a geographical separation of sexual and asexual lineages in some cases (Karunarathne et al., 2018; Kirchheimer et al., 2018; Nardi et al., 2020), others do not confirm a scenario of niche separation (Mau et al., 2015). Sexual species are otherwise (without asexual congeners) also the most abundant colonizers in extremely high altitudes and latitudes (Asker & Jerling, 1992; Brožová et al., 2019; Hörandl et al., 2011). It remains an open question why sexual species are unsuccessful in GP scenarios.…”

Application‐based guidelines for best practices in plant flow cytometry

“…In such cases the 3C peak may be much smaller than the successive peaks (i.e., 6C, 12C, or higher), or even almost undetectable, as seen for example, in studies of Leptorhabdos and Pedicularis (Orobanchaceae). 175 range of fluorescence intensities to be displayed (i.e., including additional peaks representing higher ploidy levels). This may be achieved either by locating the embryo peak near the left-hand side limit of the fluorescence axis (i.e., the X-axis) or using a logarithmic scale (preferable).…”

“…Some species may contain endosperm cells that have undergone endoreduplication (see Section 7). In such cases the 3C peak may be much smaller than the successive peaks (i.e., 6C, 12C, or higher), or even almost undetectable, as seen for example, in studies of Leptorhabdos and Pedicularis (Orobanchaceae) 175 . If endopolyploid cells are present in the endosperm, users should take particular care in analyzing the FCM histogram to avoid misidentifying peaks.…”

“…After this, only embryo nuclei can be detected by FCM, and hence insights into reproductive pathways cannot be determined. For example, Brožová et al 175 were unable to detect the endosperm peak in 37 out of 257 species (ca. 15%) of the Himalayan flora.…”

“…In contrast, the opposite has been reported for some species, that is, the endosperm peak is much larger than the embryo peak. Examples of this include Anethum graveolens (Apiaceae, Figure 9B), 177 and more generally in some families (e.g., Apiaceae, Papaveraceae, and Ranunculaceae 175 ). Given these observations, comparing the position of the 2C peak in leaf tissue with the putative 2C embryo peak obtained from analyzing seeds is strongly recommended when analyzing a new species for the first time.…”