Comparison of pollen grain morphological features of selected species of the genusCrataegus(Rosaceae) and their spontaneous hybrids

Abstract

The aim of our study was to verify, on the basis of statistical analyses of nine quantitative morphological features of pollen grains, the hypothesis that pollen grains of three parental species of Crataegus (C. laevigata, C. monogyna, C. rhipidophylla) differed from the pollen of three spontaneous hybrids of these species (C. × macrocarpa, C. × media, C. × subsphaericea). Contrast analysis revealed that a majority of the pollen features of hybrid species were characterized by significantly higher mean values than those of parental species. Analysis of pollen shape classes indicated that the parental species clearly differed from each other in contrast with hybrids, which were characterized by a similar proportion of pollen in individual pollen shape classes. Statistical analyses showed that the pollen grains of two parental species, C. laevigata and C. monogyna, were most similar to one another. Pollen grains of typical C. rhipidophylla were similar to the pollen of hybrids and the mean values of almost all studied pollen features [P, E, Exp, Exp/P, Le, d, d/E (PAI)] of C. rhipidophylla var. rhipidophylla were intermediate between those of C. monogyna and C. rhipidophylla var. lindmanii. This corroborates Zieliński's conjecture that C. rhipidophylla is probably an old, conserved hybrid between C. monogyna and C. calycina (= C. lindmanii = C. rhipidophylla var. lindmanii). According to the analysis of canonical variables, C. × macrocarpa and C. × media pollen grains were most similar. C. × subsphaericea and C. rhipidophylla var. rhipidophylla and C. rhipidophylla var. lindmanii formed another pair (group), and C. monogyna and C. laevigata constituted separate ‘single species groups’. © 2013 The Linnean Society of London, Botanical Journal of the Linnean Society, 2013, 172, 555–571.

Comparative Pollen Morphological Analysis and Its Systematic Implications on Three European Oak (Quercus L., Fagaceae) Species and Their Spontaneous Hybrids

“…pubescens . However, in three parental Crataegus species and in their three natural hybrids, deformed pollen grains occurred with similar frequencies (20–40%) [64]. The results on Quercus pollen grains reported here are similar.…”

“…According to some palynologists, hybrids have significantly larger pollen grains than those of their parents [58, 64, 81–83]. Also Quercus taxa investigated in the present study belong to this group because—as in the case of mean values of P and E features (pollen size), as well as for individual taxa—hybrids had greater pollen grains than parental species.…”

“…Other researchers proved that hybrids can have pollen size similar or smaller than their parents [53, 55, 57, 60, 62, 66, 84, 85]. Last but not the least, there are also cases where some hybrids are characterised by pollen grains larger than parental species, while others—smaller [59, 61, 64]. …”

Classification and phylogenetic analysis of Chinese hawthorn assessed by plant and pollen morphology

“…The roles of hybridization and apomixes have been considered to be minimal. The systematics of the genus is still in question, not only because numerous species have been described by several authors, but the circumscription of the species has varied widely (Christensen, 1992;Dönmez, 2008;Wrońska-Pilarek et al, 2013). Depending on the species concept employed, there is no general consensus on the number of species.…”

“…Other researchers supposed that regarding nearly all geographically and morphologically deviating groups as different species resulted in an even higher number of species (Albarouki and Peterson, 2007;Khadivi-Khub et al, 2015). The most acceptable viewpoint is that the genus compromises approximately 150-1200 species (Christensen, 1992;Albarouki and Peterson, 2007;Wrońska-Pilarek et al, 2013).…”