PALYNOLOGICAL FEATURES OF ELEVEN AETHIONEMA TAXA FROM TURKEY AND THEIR SYSTEMATIC IMPLICATIONS

Pollen morphology of 11 taxa, including 2 endemic of the genus Aethionema W.T. Aiton from Turkey was examined under light and scanning electron microscopes. The pollens of Aethionema are mostly isopolar and bilaterally symmetric; spheroidal, prolate, perprolate and subprolate with the polar axes 14.07-26.41 μm and the equatorial axes 7.85-22.02 μm; mostly tricolpate, rarely 2-colpate; surface ornamentation is micro or macro reticulate. The exine thickness varies between 0.66 and 1.91 μm, and in tine thickness ranges from 0.27 to 0.85 μm. It is found that dimension of pollen grains, surface ornamentation, apocolpidium and amb diameter are taxonomically significant. Introduction The family Brassicaceae (Cruciferae), one of the largest angiosperm families, consists about 340 genera and 3350 species distributed mostly in temperate Northern Hemisphere (Al-Shehbaz, 1986; Karaismailoglu, 2016). The genus Aethionema W.T. Aiton represents with about 45 taxa in Turkey, including 20 endemic taxa (Guner et al., 2012). Turkey is one of the biodiversity rich centers of the genus, and its number in outside Anatolia declines gradually (Davis, 1965; Pinar et al., 2007). Aethionema having relatively few morphological characters and dimorphism in fruits among individuals of some species poses some taxonomic problems in classification of taxa within the genus (Al-Shehbaz et al., 2007). Besides, some of taxa within genus are of the common convergence in fruits and seeds in the family (Mummenhoff et al., 1997). Using morphological characters in infrageneric delimitation becomes problematic in the genus. Therefore, additional features could make useful contribution to the solution of taxonomical problems in the genus. The significance of palynological information has been stressed by several workers in the family Cruciferae, viz. Inceoglu and Karamustafa (1977), Brochmann (1992), Pinar et al. (2009), and Mutlu and Erik (2012). There has been no comprehensive palynological study in the genus Aethionema. However, recently Atceken et al., (2016) investigated pollen morphology of four species of the genus. Therefore, the present investigation aims to enhance current palynological knowledge of the genus and to evaluate their taxonomic significance as taxonomic characters. Material and Methods Plant samples used for investigation were collected from different natural habitats of Turkey. A list of studied specimens is given in Table 1 with collection localities and collection numbers, and specimens were stored in the ISTF (Istanbul University Science Faculty Herbarium). Specimens for scanning electron microscopy were prepared mounting with silver adhesive on the stub, covered by gold, and examined with a JEOL Neoscope-5000 scanning electron microscope (Karaismailoglu, 2015). Email: cengiz.karaismailoglu@istanbul.edu.tr


Introduction
The family Brassicaceae (Cruciferae), one of the largest angiosperm families, consists about 340 genera and 3350 species distributed mostly in temperate Northern Hemisphere (Al-Shehbaz, 1986;Karaismailoglu, 2016).The genus Aethionema W.T. Aiton represents with about 45 taxa in Turkey, including 20 endemic taxa (Guner et al., 2012).Turkey is one of the biodiversity rich centers of the genus, and its number in outside Anatolia declines gradually (Davis, 1965;Pinar et al., 2007).Aethionema having relatively few morphological characters and dimorphism in fruits among individuals of some species poses some taxonomic problems in classification of taxa within the genus (Al-Shehbaz et al., 2007).Besides, some of taxa within genus are of the common convergence in fruits and seeds in the family (Mummenhoff et al., 1997).Using morphological characters in infrageneric delimitation becomes problematic in the genus.Therefore, additional features could make useful contribution to the solution of taxonomical problems in the genus.
The significance of palynological information has been stressed by several workers in the family Cruciferae, viz.Inceoglu and Karamustafa (1977), Brochmann (1992), Pinar et al. (2009), and Mutlu and Erik (2012).There has been no comprehensive palynological study in the genus Aethionema.However, recently Atceken et al., (2016) investigated pollen morphology of four species of the genus.Therefore, the present investigation aims to enhance current palynological knowledge of the genus and to evaluate their taxonomic significance as taxonomic characters.

Material and Methods
Plant samples used for investigation were collected from different natural habitats of Turkey.A list of studied specimens is given in Table 1 with collection localities and collection numbers, and specimens were stored in the ISTF (Istanbul University Science Faculty Herbarium).
Specimens for scanning electron microscopy were prepared mounting with silver adhesive on the stub, covered by gold, and examined with a JEOL Neoscope-5000 scanning electron microscope (Karaismailoglu, 2015).
Pollen slides for light microscope were prepared following the technique of Wodehouse (1935).Pollen grains were dyed by safranin, and mounted with a cover slip, examined with Olympus CX21FS1 light microscope, and photographed by Kameram Imaging Software.Pollen terminology based on Erdtman (1952 and1969), Brochmann (1992) and Punt et al. (1994).Ten palynological characters have been determined to discriminate the 11 taxa of Aethionema genus (Table 2), and applied Duncan's multiple range tests for each of them (SPSS, 2006), and dissimilarity matrix was consisted (Table 3).Afterwards, the variations of the determined characters are presented in Figure 3 with the whisker graph.Cluster analysis of taxa was performed in accordance with UPGMA (Fig. 4) (Mohammadi and Prasanna, 2003).Besides, the ordination of taxa is performed with Principal Component Analysis (PCA) (Fig. 5).Computations except Duncan's multiple range tests were made with the MVSP software (Kovach, 2007).
The most common shape in the examined taxa is prolate (eight taxa), subprolate (one taxon), perprolate (one taxon) and rarely spheroidal (one taxon), respectively (Figures 1-2).The result is compatible with the result of Mutlu and Erik (2012), found in the genus Arabis L. of the family Cruciferae.
Table 3. Dissimilarity matrix of the examined taxa (for the taxa abbreviations see Table 1).1).
Fig. 3. Correlation among the palynological characters for the studied taxa (for abbreviations of the characters see Table 2).
Fig. 4. UPGMA clustering of the examined taxa based on palynological characters (for taxa abbreviations see Table 1).
The pollen exine ornamentations are of a significant role in delimitation of the some closely related taxa in Cruciferae (Khalik et al., 2002).The present communication reveals that the pollen ornamentations of genus Aethionema are reticulate, coarsely reticulate, and micro-reticulate (Table 2).Anchev and Deneva (1997) reported ornamentation of the pollens of Cruciferae family is mostly reticulate and foveolate, which confirms the present result.
Pollen and colpus dimensions and, diameter of the apo and amb figure are remarkably variable to separate taxa, and to be useful for the delimitation of taxa unlike muri, lumina and thickness of intine and exine (Fig. 3).The pollen morphology of Aethionema taxa shows a close relationship with other genera of the family, for example; Arabidopsis Heynh.(Khan, 2004), Hesperis L. (Pinar et al.,2009), and Arabis (Mutlu and Erik, 2012).Fig. 5. PCA of the studied taxa based on palynological characters (for taxa abbreviations see Table 1) A dendrogram of cluster analysis of 11 Aethionema taxa has been created based on 10 characters.To define the correlation of the dendrogram and the dissimilarity matrix (Table 3), the co-phenetic correlation coefficient is measured; the higher relationship reflects more preferable in terms of position in the hierarchy.In the cluster analysis of the studied taxa formed two distinctive clades, clade A and clade B. Clade A includes taxa A. oppositifolium (A8), A. iberideum (A9) and A. grandiflorum (A11).Clade B includes taxa A. froedinii (A1), A. arabicum (A2), A. eunomioides (A3), A. fimbriatum (A4), A. speciosum ssp.speciosum (A5), A. speciosum ssp.compactum (A6) and A. saxatile (A7).However, taxon A. armenum (A10) remains out the cluster (Fig. 4).It is found that the most closely related taxa are A. speciosum ssp.speciosum (A5) and A. saxatile (A7) (dissimilarity ratio: 0.72), while taxa A. froedinii (A1) and A. armenum (A10) are the most distantly related (dissimilarity ratio: 4.66) (Fig. 5, Table 3).Clade B consists of most of the taxa studied, which can be attributed as the taxa of this clade having primitive characteristics within Aethionema.
The current investigation reveals that palynological data has taxonomic significance, and it offers substantial contribution to the current classification of Aethionema.