POLLEN FLORA OF PAKISTAN – LXVIII
Pollen morphology 20 species of the family Alliaceae from Pakistan has been examined by light and scanning electron microscope. Pollen grains are usually bilateral, hetropolar mostly boat shaped, sexine thicker tor thinner than nexine. Tectal surface is mostly rugulate foveolate or subpsilate rarely reticulate. On the basis of apertural types 3 distinct pollen types are recognized, viz., Allium fedtschenkoanum –type, Allium grifthianum-type and Allium roylei-type.
Pollen morphology and the fl ower visitors of Chaerophyllum coloratum L . ( Apiaceae )
The pollen features of Chaerophyllum coloratum L., endemic to the Dinaric Alps, have been examined by both light microscopy and scanning electron microscopy in order to contribute to a better understanding of the taxonomic status of the species. Flower visitors have also been observed and analyzed with the aim of clarifying certain pollination aspects of the species including fl ower attractiveness especially to honeybees, and also in order to ascertain its contribution to the bee pasture. The pollen grains of C. coloratum are isopolar, radially symmetrical and medium sized. Polar axis (P) is 26.83±1.77 μm length, and equatorial diameter (E) is 9.17±0.57 μm length. P/E ratio amounts 2.90±0.10 indicating a perprolate shape. In an equatorial view, the grains are constricted in the equatorial region (bone-shaped), with obtuse polar caps. In polar view, they are triangular with obtuse angles and furrows in the sides of the triangle (interangular). The grains are tricolporate with three straight ectocolpi arranged regularly meridionally, of mean length 14.43±2.17 μm, each of which has one endopore. The characteristic internal thickenings around the protruding, clearly visible endopores (costae) in the constricted equatorial region are obvious in light microscopy. The ornamentation is psilate, irregularly rugulate (“cerebroid”), the exine surface is rather undulating. With regard to the observed fl ower visitors, the following pollination types occurred: melittophily, myophily, sapromyophily, cantharophily, and phalaenophily, and the most frequent pollinator was the honeybee.
Molecular phylogenetics of Dipsacaceae reveals parallel trends in seed dispersal syndromes
Abstract.Phylogenetic relationships among 17 taxa of Dipsacaceae were inferred from nucleotide sequence variation in both the internal transcribed spacer (ITS) regions of nuclear ribosomal DNA and the chloroplast trnL(UAA) intron sequences. The combined phylogenetic analysis, carried out by using two taxa from Valerianaceae as an outgroup yielded a single most parsimonious tree, in which Dipsacaceae are divided into two major clades: one including Lomelosia and Pycnocomon, both in a sister group relationship with a clade containing Pterocephalus, Scabiosa and Sixalix; the other including Pseudoscabiosa, Succisa and Succisella is sister group to Knautia, Pterocephalidium, Dipsacus and Cephalaria. The results obtained here greatly differ from previous ones based on classical morphology, but are congruent with recent findings on epicalyx differentiation and with pollen characters. In particular, our results would confirm on molecular grounds the recently restricted circumscription for Scabioseae proposed by other authors. Our phylogenetic hypothesis indicates that adaptations to seed dispersal have been a very strong driving force in Dipsacaceae evolution, with similar selective pressures causing the onset of similar epicalyx shapes and dispersal modes in a parallel fashion in various taxa. For this reason, the gross morphology of the involucel is deceptive in inferring relationships.