Lilium spp. pollen in China (Liliaceae): Taxonomic and Phylogenetic Implications and Pollen Evolution Related to Environmental Conditions

Abstract

Recent molecular and karyologic studies have significantly modified delimitation of Lilium. However, despite the importance of pollen evolution in the genus comprehensive studies with electron microscopy and evaluation of pollen evolution are lacking. Therefore, we studied pollen morphology in a sample of 65 individuals from 37 taxa covering all the sections distributed in the world, using scanning electron microscopy. Our collection of 49 individuals from 21 taxa covering all five sections in China was also included in the database. We found pollen tetrads in L. bakerianum. Based on present and previous studies, our results suggest that pollen from L. formosanum should be classified as a new type, Formosanum. Combined with morphological and molecular evidence, pollen sculpture patterns appear to reflect phylogenetic relationships and are useful for species or subsection delimitation. Based on a comprehensive survey and correlation with potential functional implications, we propose the following hypothesis: evolution of an exine sculpture shows pollen type trends from Martagon → Callose → Concolor → Formosanum. The evolutionary trend regarding pollen sculpture and size could be related to selective pressure to adapt to environmental conditions. Pollen size and shape showed a significantly positive correlation with annual precipitation, and smaller pollen grains appear to adapt better in habitats with extreme conditions. Evolution trends in exine sculpture do not appear to be definitively correlated with pollen size and shape.

Pollen morphology and anatomical features of Lilium (Liliaceae) taxa from Turkey

“…Pupuleku et al (2010) determined that exine thickness ranges from 1.8 µm to 2.3 µm in L. martagon, but it was measured 2.44 (± 0.36) µm in the present study. Baranova (1985) and Du et. al (2014) classified Lil- In the dendrogram resulting from UPGMA (Fig.…”

Genetic variability and diversity of the main resources of lily assessed via phenotypic characters, pollen morphology, and ISSR markers

“…Baranova (1985) divided the morphological types of pollen into three categories: Martagon, Callose, and Concolor, depending on the pollen number, shape and arrangement of columellae. Based on previous and present studies, Du (2014b) suggested that pollen from L. formosanum should be classified as a new type, Formosanum, and proposed that the trends of pollen types were from Martagon to Callose, to Concolor, to Formosanum, as demonstrated by the evolution of an exine ornamentation. In addition, the pollen morphology of some Chinese species has been described using scanning electron microscopy (SEM) in several relevant studies (Li and Qin, 1993;Zhang et al, 2006;Wu et al, 2007).…”

“…Taxonomists and botanists have gradually recognized the importance of pollen morphology in clarifying the classification of Lilium. Pollen grains should be regarded as a functional unit, with the exine ornamentation as a compromise between the following four major functions: protective, harmomegathic, reservoir, and clustering (Muller, 1979;Du et al, 2014b). Baranova (1985) divided the morphological types of pollen into three categories: Martagon, Callose, and Concolor, depending on the pollen number, shape and arrangement of columellae.…”

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

“…The preparatory work before the scanning electron microscopy (SEM) followed Du et al (2014) and Wang et al (2016), with slight modifications. For the purpose of collecting pollen grains, flower buds of Chinese hawthorn cultivars were collected at the balloon stage, just before the opening of the anthers.…”

“…Researchers have since come to realize the significance of pollen morphology in clarifying the classification. Pollen grains could be regarded as functional units, with functions such as: protective, harmomegathic, reservoir, and clustering (Muller, 1979;Du et al, 2014).…”