Phenological shift along an elevational gradient and dispersal of pollen and seeds maintain a hybrid zone between two cherry tree species

Abstract

Hybrid zones between species with staggered reproductive phenology sometimes occur along elevational gradients. The maintenance of such hybrid zones may depend on elevational shift in phenology and vertical dispersal of pollen and seeds. In a hybrid zone of Cerasus leveilleana (Cl) and C. sargentii (Cs), 111 adults, 372 embryos of 65 mothers, and 133 juveniles were sampled across elevations of 900–1,400 m in central Japan. Using the hybrid index estimated from nuclear microsatellites, the samples were assigned to Cl, Cs or their hybrid taxon. Cs was in higher elevations than Cl with an overlapping range, and their hybrids were in intermediary elevations. Flowering periods were earlier in Cs than in Cl with little overlap at the same elevation and were intermediate in their hybrids. Flowering periods were delayed in higher elevations and overlapped between Cl and Cs in different elevations. Fruiting periods were slightly earlier in Cs than in Cl but were largely overlapped. Effective pollinators and seed dispersers were common among the taxa. Changes in the hybrid index from mothers to their embryos were larger in hybrid mothers than in Cl or Cs mothers, indicating mating of hybrids with diverse taxa. In Cs, juveniles were more abundant in lower elevations than embryos, indicating downhill seed dispersal. Proportions of hybrids were 19% in embryos, 17% in juveniles and 12% in adults. The findings suggest that the hybrid zone is maintained by interspecific pollination between different elevations, backcrossing with hybrids at similar elevations, vertical seed dispersal and mild selection against hybrids.

Asymmetric Reproductive Barriers and Gene Flow Promote the Rise of a Stable Hybrid Zone in the Mediterranean High Mountain

“…The absence of an interspecific genetic structure and differentiation found in the altitudinal transect from E. mediohispanicum to E. nevadense seems to be related to the significant and unidirectional levels of gene flow detected for the hybrid population. These patterns are probably related to the highly diverse pollinator assemblage interacting with these species in the Sierra Nevada (Gómez et al, 2009a,b;Abdelaziz et al, unpublished data) and to their ability to promote pollen movement between populations (Tochigi et al, 2021;Abdelaziz et al, unpublished data), as supported by the high number of multilocus genotypes identified in this study. We could identify the hybrid zone despite the nearby distribution of our populations in this area.…”

When Are Cacti Found with Flowers and Fruits? Estimation of the Reproductive Phenology of the Genus Xiquexique Based on Herbarium Data

“…In addition to the interaction with environmental factors, phenological patterns can influence different biological events, such as the formation of hybrids [32]. Our data revealed an overlap in the flowering periods of X. gounellei and X. tuberculatus, providing a partial explanation for potential hybrid formation, especially when these species are close geographically and genetically [22,23].…”

Metabolomics analysis reveals the metabolite profiles of Rheum tanguticum grown under different altitudinal gradients

“…Second, the aboveground parts of R. tanguticum in low-altitude areas varied from those in high altitudes. Altitude affects the phenological period of plants [ 25 ]. We found that later growth and development were higher at higher altitudes than at lower altitudes.…”