Pollen Sculpture Research Articles

Neglected plants of Prunus L. (Rosaceae) in East China

A new species with a new variety of Prunus L. (Rosaceae) from Zhejiang, East China, namely P. huadongensis, and P. huadongensis var. pubipes, were described and illustrated. Prunus huadongensis is similar to P. conradinae Koehne, but differs in having leaf blades glabrous on both surfaces, margin obtusely serrulate, teeth curved-inward with a breast-like apical gland, and pedicel apically slightly thickened. Additionally, pollen sculpture of P. huadongensis is characterized by relatively coarse striae and no distinctive perforations between striate elements, whereas pollen sculpture of P. conradinae shows fine striae and dense perforations between striate elements. The new variety, var. pubipes, differs from the typical variety in leaf blades appressed-pubescent on veins of abaxial surfaces, branchlets, petioles, peduncles, pedicels, outside base of hypanthium and sepals all spreading-pubescent, leaf blade obtusely biserrulate at margin.

Pollen morphology of selected tropical plants in Peninsular Malaysia and its implication in the paleoecological reconstruction of Southeast Asia

Marine pollen records from the southern South China Sea (SCS) have yielded critical information regarding epicontinental vegetation succession since the last glacial period, which involves understanding the role of tropical rainforests in driving climate change. However, the rich biodiversity and pollen taxa in Southeast Asia are challenging for palynological work, such as detecting pollen signals from various vegetation types and tracing the source areas of pollen grains deposited in the ocean; therefore, improving the taxonomic level of fossil pollen identification is significantly crucial for pollen analysis in tropical regions. To enrich modern pollen references of Southeast Asia, we observed the pollen morphology of 124 identified species (111 genera and 42 families) from tropical Malaysia using a light microscope and scanning electron microscope (SEM). The results show 19 pollen morphotypes, of which the tricolporate type occurs in half of the samples, reflecting the complexity of fossil pollen classification and identification. Pollen sculpture and aperture details of the selected taxa are clearly shown under SEM, which significantly improves the morphological understanding of tropical pollen (e.g., fabaceae, euphorbiaceae, and rubiaceae). This result presents the potential of extracting unique pollen signals to distinguish different vegetation types that contain many common species in Southeast Asia. It highlights the significance of improving pollen identification levels to clarify whether there was a widespread rainforest on the exposed continental shelf during the last glacial period in the southern SCS.

Grimmipollis burmanica gen. et sp. nov.: New genus of the soapberry family (Sapindaceae) from the late Eocene of central Myanmar

As a crossroads for plant dispersal between Laurasia and Gondwana since at least the late Eocene, the Central Myanmar Basins have yielded rich and diverse fossil pollen. Here we report Grimmipollis burmanica, a new genus and species in the soapberry family (Sapindaceae) from the upper Eocene Yaw Formation in the Central Myanmar Basins. We also investigate its similarity of pollen sculpture with other selected genera using hierarchical cluster analysis, and its source paleoecology with pollen diagrams. Grimmipollis pollen grains are characterized by parasyncolporate apertures with an apocolpial field at each side, distinct margines along the colpi, arcuate, tuberculate and rope-shaped mesocolpial ridges, and prominent, verrucate or fossulate apocolpia. These features distinguish this genus from other syncolporate and parasyncolporate types in the extant Sapindaceae genera, and fossil pollen genera. As most syncolporate and parasyncolporate types occur in the tribe Cupanieae, G. burmanica is likely derived from an extinct Cupanieae and thus a rainforest tree species. The hierarchical cluster analysis confirms our establishment of Grimmipollis, and reveals it is morphologically close to Meyeripollis. The sedimentary environment from which these pollen grains were retrieved suggests that G. burmanica could be a member of seasonal swamp forests.

Theriophonum blumei (Araceae), a new species from Tamil Nadu, India

Theriophonum blumei sp. nov., a new species is described and illustrated from Tamil Nadu, India based on morphological and leaf epidermal features. Although morphologically T. blumei appears to be similar to T. sivaganganum (Ramam. & Sebastine) Bogner having long acuminate spathe, it is different from T. sivaganganum in various aspects such as ellipsoid seed with ridged surface, spinulose and bifid stigma, filiform neuters and berries with purplish strands. T. blumei has echinate pollen sculpture and T. sivaganganum has verrucate sculpture. Added to that, molecular based (rbcL, matK, trnL‐F) phylogenetic analysis also indicate that T. blumei is genetically distinct from T. sivaganganum.

Pollen Morphology of Rosa sericea Complex and Their Taxonomic Contribution

In this research, the pollen morphology of the Rosa sericea complex has been studied by Scanning Electron Microscope (SEM). The present study aimed to provide baseline information for the taxonomic identification of the R. sericea complex taxa. The pollen sculpture, outline, and aperture show variability in the studied taxa. The R. sericea complex includes taxonomically challenging species with undistinguishable boundaries. Identifying taxon boundaries in closely related species is fundamental to investigating evolution and biodiversity. Taxa circumscription of R. sericea complex is insufficient, unresolved, and is a prerequisite for comprehensive systematic revisions. To resolve these issues, we have attempted to identify some important diagnostic characters for the species of R. sericea complex. This research studied different qualitative and quantitative characteristics of R. sericea complex pollen. The qualitative characteristics included polar and equatorial view, sculpture, pollen outline, apertures, exine, size category, and polarity of pollen. In contrast, the quantitative features include polar and equatorial diameter, P/E, colpi length and width, and distance between colpi. Pollen of this complex is mono and tricolporate. The morphological characters studied here provide very few taxonomic details with which to separate the species of the complex into distinct taxa. Some of the studied characters offer important information for species delimitation including sculpture, pollen outline, and apertures.

Study of Phenotypes Variability of Pollen Grains Malus domestica Borkh. by Scanning Electron Microscopy

The studying of Malus domestica Borkh. pollen allows us to determine the details of morphological characteristics and describe the most important parameters and pollen sculpture that can be used to identify representatives of species. We analysed pollen morphology of seven Malus domestica genotypes from old and local varieties from the territory of Slovakia via a scanning electron microscope. We used principal components analysis to explore variability in pollen grain size (polar and equatorial diameter), shape, aperture type, and exine ornamentation. The complexity of these morphological characteristics and ultrastructure allows determining the differences or similarities between the same and various species and genotypes, which may be a useful tool for systematics with significant diagnostic value. Findings confirmed small differences among the genotypes in measured traits with polar and equatorial diameters in the range from 31.85 to 42.85 μm and from 21.23 to 23.93 μm, respectively. Shape index (P/E ratio) depending on elongation or roundness of pollen grains varied from 1.44 to 1.87. Hierarchical cluster analysis and principal component analysis of morphological data helped to compare evaluated morphometric parameters and identified five closely related groups. It was noted that diversity of surface sculpturing of pollen grains in combination with shape and size enables to use of a complex of thin morphologic signs for M. domestica pollen identifications. Pollen data combined with other morphological evidence (e.g., floral characters) have more recently become an important indicator of which genotypes may be the best representatives of species.

Study of Morphological Characters of Pollen Grains Sweet Chestnut (Castanea sativa Mill.) by Scanning Electron Microscopy

The studying of Castanea sativa Mill. pollen allows us to determine the details of morphological characteristics and described the most important parameters and pollen sculpture that can be used to identify representatives of species. The general characteristics and significant morphological traits of pollen grains of 16 genotypes Castanea sativa Mill. collected from M.M. Gryshko National Botanical Garden of Ukraine(Kyiv) were observed via a scanning electron microscope (SEM). The measurement of morphometric parameters was carried out on 50 pollen grains from each genotype using the AxioVision Rel. 4.8.2.0 program. The length of the polar axis (P) and the equatorial diameter (E) of grain, P/E ratio were measured and their variation was compared among studied genotypes. SEM investigations showed that the pollen grains of Castanea sativa are small-sized, the equatorial view is elliptic, the polar view is angular, with convex mesocolpia, more or less circular. This study showed the small differences between the genotypes in all measured factors. The average polar axis and equatorial diameter of pollen grains values varied in the interval 19.10 ±0.21–20.53 ±0.21 and 8.86 ±0.05–9.85 ±0.08, respectively. We determined the variation coefficient in the range of 3.37–8.93 %. It was noted that diversity of surface sculpturing of pollen grains in combination with shape and sizes enables to use of a complex of thin morphological signs for Castanea sativa pollen identifications.

Application of multimicroscopic techniques (LM and SEM) in comparative palynological study of Asteroideae members, inhabited in Pakistan.

In the present study light and scanning electron microscopic approaches were used to study the palynological variations among 30 Asteroideae members. Variety of qualitative and quantitative palynological characters like pollen shape and type, pollen sculpturing, pollen size, P/E ratio, exine and intine thickness, interspecific difference, colpi size, pore size, spines length, spine width, and pollen fertility were observed. Results reported remarkable variations among pollen characters of studied taxa. The shape of pollen grains in polar and equatorial views varied from specie to specie such as spheroidal, prolate, oblate, subspheroidal, oblate spheroidal, prolate spheroidal, suboblate, and sub prolate. Bidens pilosa L. showed maximum pollen size in both polar and equatorial views, whereas minimum pollen size in polar view was found in Tetraneuris scaposa (DC.) Greene. (i.e., 30.5 μm) and in equatorial view was found in Cosmos sulphureus Cav. (25.5 μm).The highest P/E ratio (1.39 μm) was measured in Glebionis coronaria L. The values of exine and intine thickness also varied. Tricolporate, tetracolporate, trizonocolporate, pentoporate, and polypentoporate pollen types were examined. Spinateand echinate pollen sculpturingobserved under SEM. Variations in spine length and width also recorded. The maximum pollen fertility (98%) was measured in Chrysanthemum morifolium Ramat. and the lowest (56%) was recorded in Thymophylla tenuiloba (DC.) Small. It was concluded that the variations in qualitative and quantitative characters were seemed to be valuable for the taxonomic investigations of Asteroideae taxa.

Scanning Electron Microscopy-based palynological characterization of selected Euphorbiaceae taxa colonized in Pakistan.

The present study was carried out on scanning electron microscopic-based palynological characterization of selected 20 Euphorbiaceae taxa. In this study, important pollen qualitative and quantitative features of selected Euphorbiaceae species such as polar diameter, equatorial diameter, P/E ratio, sculpturing of pollen, exine thickness, intine thickness, presence or absence of colpi and length of colpi, and pollen fertility were examined. Remarkable variations in these pollen characters had been observed among these species. In both polar and equatorial views, Riccinus communis L. exhibited the highest pollen size (polar = 264.1 μm, Equatorial = 270 μm), while Acalypha wilkesiana Mull Arg. showed lowest pollen size (Polar = 17 μm, Equatorial = 18.5 μm). Most of the pollen varied from oblate to spheroidal in shape. With regard to the P/E ratio, Sapium sebiferum L. Roxb showed the highest ratio while Bischofia javanica Blume showed minimum, that is, 1.18 and 0.85, respectively. Intine and exine thickness also varied. Most of the pollen grains were monade. Tricolporate, tricolpate, monocolpate, pentaporate, and polyporate pollen aperture types have been observed. Most of the plants showed regular, reticulate, and echinate pollen sculpturing. Pollen fertility also varied from species to species but most of the plant showed pollen fertility between 70 and 80%. Through this work, it has been concluded that quantitative and qualitative pollen features are helpful at the specific level as well as the generic level and can provide a fruitful taxonomic solution.

Pollen morphology of the Megamexican cycads reveals the potential of morphometrics to identify cycad genera

Background: Although pollen morphology has always been an important tool in plant systematics, the possibility of distinguishing between related taxa is still debated. A difficult case is the cycads, where their morphology and small size is very similar. Pollen morphology has been important in plant systematics and determination at the species level is possible depending on the group. Controversial cases are the cycads, where their small pollen and smooth sculpture when observed under light microscopy present few useful characters for separation at the species level.
 Question: Will cycad pollen morphometry be useful to distinguish taxa?
 Study species: 15 species within the genera Ceratozamia, Dioon and Zamia were investigated with five species of each genus.
 Methods: Pollen was obtained from both live specimens from the Clavijero Botanic Garden of the Instituto de Ecología, A.C., as well as herbarium specimens. Acetolyzed pollen was used for descriptions and morphometry, and non-acetolyzed pollen for SEM images.
 Results: The thickness of the exine and pollen sculpture of Dioon differed from that of Ceratozamia and Zamia thus allowing its identification. The pollen morphology of Ceratozamia and Zamia is very similar and therefore difficult to distinguish between species.
 Conclusions: The thicker exine of Dioon allows its pollen to be distinguished from the other two genera. Morphometric methods must be applied to distinguish pollen between species of Ceratozamia and Zamia.

Can pollen sculpture in Rhododendron subsec. Rhodorastra differentiate species?

Pollen sculpture elements of four Rhododendron species from 49 populations were studied using scanning electron microscopy. The sculpture in the polar areas of the studied taxa pollen differed in type, shape, size, and distribution of individual elements. There were five sculpture types identified. The pollen of Rhododendron ledebourii from various populations in Altai revealed sculpture elements characteristic of R. dauricum, R. mucronulatum, and R. sichotense, questioning the taxonomic position of the former species. Analysis of the geographical distribution of sculpture types clarified species boundaries and zones of sympatric distribution. The northern boundary of R. mucronulatum was expanded and new populations of R. sichotense were revealed. In the sympatric zones of R. mucronulatum and R. sichotense, there were intermediate populations showing pollen sculptures typical of R. dauricum, R. mucronulatum, and R. sichotense. The sculpture diversity observed in the pollen of R. dauricum, together with its presence in sympatric zones, suggests that it is probably a hybrid of R. sichotense and R. mucronulatum or a subspecies of R. sichotense.

Pollen morphology of subfamily Maloideae (Roseaceae) with special focus on the genus Photinia

Pollen morphology of 27 species of Photinia sensu stricto and five closely related genera of subfamily Maloideae (Rosaceae) were studied in detail. Palynomorphological characteristics were examined using scanning electron microscopy (SEM). Comparative pollen analysis was accomplished based on pollen size, shape, polar and equatorial views, polar and equatorial diameter ratio (P/E ratio), width of aperture, and exine ornamentation. The pollen grains of studied species were found to be monad, tricolporate, small to medium in size (P=17.42–30.45 μm, E=9.26–20.18 μm) and to have shapes oblate-spheroidal (0.88–1.0 μm), prolate-spheroidal (1.01–1.14 μm), sub-prolate (1.15–1.33 μm), prolate (1.34–2 μm), and perprolate (>2 μm). The exine ornamentation was perforated-striate, and two different types were identified. The result of quantitative characters has paltry taxonomic importance. The characters studied here delimit at generic level for some genera but not at species level. The obtained result was partially consistent with that of molecular studies published earlier. The pollen size and shape were found to be different between Asian and American species of Photinia. Especially exine sculpture was found to be an important feature to distinguish species of all genera studied. PCA analysis showed that the pollen shape, pollen sculpture, pollen size, and polarity are the key characters to distinguish the species of Photinia and the closely related genera in subfamily Maloideae. Based on pollen exine, two groups (Type I and Type II) were distinguished. The aim of the present study was to find out the taxonomic significance of palynomorphological characteristics in subfamily Maloideae (Rosaceae).

Taxonomic study of subfamily Nepetoideae (Lamiaceae) by polynomorphological approach.

The present study is insight into pollen morphology for characterizing species and their utility in the taxonomic separation of certain taxa of subfamily Nepetoideae (Lamiaceae) from Pakistan. The pollen micromorphology of 11 species of the Nepetoideae was analyzed and documented using light microscopy and scanning electron microscopy (SEM) for both qualitative and quantitative characteristics. Most species have hexazonocolpate pollen grains but trizonocolpate and tetrazonocolpate pollen with circular and oval amb were also rarely observed in Mentha spicata. The basic pollen shape in most of the studied species was subspheroidal but prolate grains were also observed in M. spicata, S. coccinea, and S. plebeia. The exine sculpturing of Nepetoideae pollen was taxonomically very informative particularly at subfamily level. Observations of exine sculpturing with SEM revealed various types of pollen grains: reticulate, bireticulate, microreticulate, perforate, aerolate, and gammate. The bireticulate type further subdivided into three subtypes based on the number of secondary lumina in each primary lumen and is characterized by varying characteristics of the secondary reticulum and primary muri. A significant variation was observed in colpus surface ornamentation. The maximum polar diameter was found in O. americanum (58 ± 5.8 μm) and the maximum equatorial diameter observed in O. basilicum (50.25 ± 1.37 μm). Pollen features of the studied species were discussed and compared based on the current taxonomical concepts. The results showed that pollen traits of the subfamily Nepetoideae was found significant to classify the taxa. Furthermore, pollen features provide additional evidence to distinguish macromorphologically similar taxa from each other.

Implication of light and scanning electron microscopy of foliar cuticular and palynological features in the correct identification of medicinal plants

Abstract Foliar epidermal anatomy and palynology of six medicinal plant species Catharanthus roseus., Carum carvi L., Trachyspermum ammi L., Anethum graveolens L., Foeniculum vulgare Mill. and Nigella sativa L. are commonly used for different medicinal uses Six medicinal species were used as an example and their foliar cuticular and pollen features were evaluated by light and scanning electron microscopy (SEM). Features allied to pollen grains (pollen type, colpi,and sculpture type) and foliar cuticular features (epidermis, stomata, and trichome) were found to be important examined characters. Pollen grain morphology of these medicinal plants revealed that the pollen is the prolate and per-prolate type. Their foliar epidermal anatomy revealed the presence of an anomocytic type of stomata in C. roseus, C. carvi and N. sativa, dicytic type in F. vulgare and anisocytic type in A. graveolens. Keywords: Medicinal plants; Palynology; SEM; Taxonomic identification http://dx.doi.org/10.19045/bspab.2018.700177

Morpho-palynological assessment of medicinal flora of district Lahore, Pakistan based on LM and SEM.

This study was carried out to identify 20 high valued medicinal plants of District Lahore, Punjab, Pakistan with the help of the palynological studies. The distinguishing characteristics for selected species were found by systematized methods using light microscopy and Scanning Electron Microscopy. In this study, important pollen qualitative and quantitative features of these medicinal species such as polar and equatorial outline and their diameter, P/E ratio, presence or absence of pore, sculpturing of pollen, exine thickness, intine thickness, intercellular distance of exine and intine, presence or absence of spines, length of spines, width of spines, presence or absence of colpi and length of colpi, were compared. Remarkable variations in these pollen characters have been observed. Pollen grains were usually circular-semicircular (Calendula officinalis), spheroidal (Convolvulus arvensis), bilobed and trilobed (Convolvulus arvensis), spiny, (Abutilon indicum), oblate (Terminalia chebula) and elongated (Euphorbia pilulifera). In polar view Conyza bonariensis exhibited the highest pollen size [195.9 (211.6-180.2) μm]. While in equatorial view Calendula officinalis and Euphorbia pilulifera had lowest value [22.5 (20-25) μm] whereas Carissa carandas [165 (140-179) μm] appeared to be the largest. Parthenium hysterophorus showed the highest P/E ratio, that is, 1.28. Colpi were reported in only 7 species. Most of the plants showed 100% fertility but Terminalia chebula showed the least value 35%. In the present, project the diversity in pollen morphology present pollen as a valuable taxonomic tool. It is also concluded that pollen features are helpful at the specific level as well as generic level and can provide us fruitful taxonomic solutions. RESEARCH HIGHLIGHTS: Palynological flora of the medicinal plant species of district Lahore, Pakistan is investigated first time on the basis of LM and SEM and the flora is found very significant for taxonomic investigations.

Molecular systematics of Caryopteris (Lamiaceae) and its allies with reference to the molecular phylogeny of subfamily Ajugoideae

AbstractAjugoideae, the third–largest subfamily of Lamiaceae with 23 genera and about 760 species, is distributed worldwide, but is primarily found in tropical regions. During the past two decades, substantial progress has been made towards discerning phylogenetic relationships and generic boundaries in Ajugoideae, but major questions still remain. This phylogenetic study was conducted using 422 DNA sequences from seven DNA regions (nrITS, ETS, and matK, rbcL, rps16, trnL–trnF, trnH–psbA) representing 50 species from 22 of 23 genera in Ajugoideae, to reconstruct the backbone phylogeny of the subfamily, with emphasis on phylogenetic relationships among Caryopteris, Schnabelia and their closest allies. Key results: (1) Ajugoideae is monophyletic and can be divided into four main clades. (2) Discretitheca and Glossocarya, which have not been included in any previous molecular analysis, are members of Ajugoideae and closely related to Karomia and Rotheca. (3) Expanded Schnabelia is monophyletic, sister to Rubiteucris, and consists of two morphologically distinct clades, recognized here as sect. Cylindricaulis and sect. Schnabelia. (4) Traditionally defined Caryopteris is confirmed to be polyphyletic, with several segregate genera. (5) Recircumscribed Caryopteris was found to be monophyletic, but intrageneric relationships were not fully resolved. Synapomorphies of Caryopteris include boat–shaped nutlets that are winged along the edge, fimbriate anterior corolla lobes, and suprareticulate pollen sculpturing. Caryopteris forrestii var. minor was elevated to species rank based on molecular and morphological evidence.

Study on pollen characteristics of different calla lily cultivars (Zantedeschiaspp.)

Calla lily cultivars (Zantedeschia spp.) are internationally popular products. However, their pollen germination rate is relative low under natural condition, which hampers the breeding of new cultivars. In this work, morphological characteristics, viability and germination characteristics of pollen from 18 different calla lily cultivars were analyzed. The results showed that pollen among all samples was prolate in shape and similar in size. The lengths of the polar and equatorial axes were 28.8-39.5 and 21.9-32.3 µm, respectively, and the polar to equatorial axis ratio ranged from 1.14 to 1.43. Pollen extine was smooth without aperture, pollen sculpture was not obvious. At 25°C in the dark, the pollen germination ratio and pollen tube length were highest within 24 h, especially in the first 9 h. Different culture media were used to study the culture conditions for 'Crowborough' pollen, and we found that a suitable testing medium for pollen viability contained 10% sucrose and 0.01% H3BO3.

Pollen morphology of Asian Vigna species (genus Vigna; subgenus Ceratotropis)from India and its taxonomic implications

The pollen morphology of 22 Asian Vigna [subgenus Ceratotropis (Piper) Verdc.] species, including wild and cultivated taxa from India, was investigated with light microscopy and scanning electron microscopy. The quantitative data were analyzed by descriptive statistics and multivariate statistics. The pollen grains are prolate spheroidal in shape with equatorial diameter of 36.06-116.33 μm and polar diameter of 36.31-120.96 μm in equatorial view. The small pollen dimensions were observed in Vigna hainiana, V. trilobata, and V. indica and the largest in V. vexillata. The pollen grains have reticulate-homobrochate and reticulate-heterobrochate types of pollen sculpture. The lumina are psilate or granulate with penta-hexagonal, penta-polygonal, and irregular shape. The muri are sinuous, straight, or narrow-straight. Pair group method using arithmetic averages analysis was used to divide the main pollen taxa into four groups based on pollen morphology. Statistically distinctive taxa were identified using principal component analysis. In the present investigation, the taxa studied demonstrated sufficient pollen polymorphism in their sizes, equatorial views, lumina shapes, and muri widths.

Morphological study of some taxa of Ranunculaceae Juss in Egypt (anatomy and pollen grains)

Ranunculaceae is a large angiospermic family (43 genera and 2346 species). Seven taxa were subjected in the present study representing six genera. Stem anatomy, flower anatomy, lamina epidermal characters as well as the pollen morphology were carried out according to traditional taxonomic methods using LM and SEM. The specific target of the present study is to contribute knowledge to Ranunculaceae from different perspectives. The obtained microcharacters of stem, leaf and flowers are considered diagnostic at the generic and specific levels (e.g., stem outline, types of cortex, internal appearance of stem, leaf types, perianth vascularization and presence of nectary scales). The pollen characters of the studied taxa are considered highly diagnostic at the generic and specific levels especially pollen class (trizonocolpate, pantocolpate and pantoporate) and pollen sculpture (aculeate, verrucate-aculeate, aculeate-faveolate and scabrate-verrucate). The obtained data facilitate the construction of artificial keys to delimitation between the studied taxa.

Differences in sculpture and size of pollen grains: new morphological evidence of diversification in Pelliciera rhizophorae, an ancient Neotropical mangrove species

The present study shows new evidence of morphological traits that supports the hypothesis of diversification between two genetic variants of Pelliciera rhizophorae (Tetrameristaceae), the most ancient species in the Neotropical mangrove ecosystem. Previous studies using molecular markers identified two variants of this species. Our new study, using pollen grain morphology, revealed differences in pollen sculpture between the two variants; that is, in Variant A the exine is characterised as perforate–verrucose, while in Variant B, it is punctuate. Pollen size in Variant A is larger than in Variant B, whereas the exine is thicker in Variant B than in Variant A. The differences in pollen morphology between the two variants represent new evidence suggesting that a diversification process might be occurring within P. rhizophorae, possibly due to adaptive processes in response to environmental conditions or pollination vectors.