1. Introduction

The Poaceae Barnhart (Gramineae Juss.) family is one of the largest and most ecologically significant for terrestrial ecosystems, including cultivated grasses and numerous wild species. It plays a key role in the functioning of terrestrial ecosystems, providing primary biomass production, forming soil cover, and maintaining biodiversity. Furthermore, members of the Poaceae family are of exceptional economic importance – they contain all major grain crops, forages, turf grasses, and ornamental grasses, making them the foundation of both natural and anthropogenic communities [1,2].

By the 21st century, Poaceae taxonomy had undergone significant changes, moving from morphologically based schemes to molecular phylogenetic classifications. In 1985, Watson, Clifford, and Dallwitz published a seminal paper proposing a quantitative classification of Poaceae based on an analysis of nearly 300. The authors introduced a new systematic characteristic—supertribes—that more precisely group genera within large subfamilies (Pooideae, Panicoideae, Chloridoideae, etc.). A distinctive feature of their relationship is a strictly formalized data analysis method that allows for assessing the degree of relatedness between results based on statistical character detection. This system, although developed for the application of molecular methods, is an important step in the transition from selective classifications to analytical and reproducible systems. In the context of urban flora, rapid classification is convenient for comparing morphofunctional groups and analyzing their adaptation to the urban environment characters [3].

N.N. Tsvelev made a significant contribution to the development of Poaceae taxonomy, examining the family from the perspective of evolutionary morphology. Based on an analysis of flower, leaf, and spikelet structure, as well as chromosomal and anatomical features, he identified approximately 900 genera grouped into 41 tribes and two major subfamilies—Bambusoideae and Pooideae. Tsvelev placed great emphasis on the origins of cereals, their adaptations to various environmental conditions, and evolutionary mechanisms (hybridization, polyploidy, etc.). Although his classification relied heavily on morphological features, it still serves as an important basis for assessing the taxonomic diversity of cereals in regional floras, including in urban ecosystems [4].

In recent decades, the rapid development of molecular taxonomy and phylogenomics has allowed us to further elucidate the evolutionary relationships within the Poaceae family. The use of nuclear and plastome markers, whole-genome analysis, and studies of chromosome duplications and rearrangements have significantly refined our understanding of cereal lineages, their adaptive strategies, and the divergence of genera and tribes. These data are particularly important for understanding the mechanisms of cereal tolerance to urban stresses, such as drought, soil compaction, air pollution, and temperature fluctuations.

In the urban flora of Karshi, characterized by an arid climate, high summer temperatures, and moisture deficit, representatives of the Poaceae family occupy a prominent place in the vegetation structure. They form both spontaneous and introduced phytocenoses, serving as indicators of anthropogenic impact and the adaptive resilience of the flora. It has previously been shown that, under similar climatic conditions in the Karshi oasis, ornamental and introduced species exhibit high ecological plasticity and the ability to adapt to environmental stressors [5,6].

Despite the diversity of grasses found in the urban flora of Karshi, their taxonomic diversity remains poorly studied, highlighting the need for a systematic analysis of representatives of the Poaceae family in the context of the region's urban ecosystems. Based on the above, the relevance of this study stems from the need for a comprehensive analysis of molecular genetic studies of the Poaceae family globally and an understanding of their significance for understanding the species composition and adaptive characteristics of the grasses that make up the flora of the city of Karshi. In this context, the study aims to systematically review current molecular genetic and phylogenomic data on representatives of the Poaceae family, as well as to assess their taxonomic and ecological diversity in the urban flora of Karshi.

2. Materials and Methods

The study was conducted as an analytical and bibliographic review with elements of comparative analysis of published molecular genetic and phylogenomic data on representatives of the Poaceae family. The work included three interrelated stages: searching and selecting sources, systematizing the data by areas of genetic research, and interpreting the taxonomic and ecological diversity of Poaceae in the urban flora of Karshi.

An information search was conducted in international scientific databases: Scopus, Web of Science, PubMed, Google Scholar, and ScienceDirect. The review included papers published between 1980 and 2025.

A topographic map of the city of Karshi was developed, consisting of 186 squares, each measuring 1x1 km. These squares were assigned indices using the Latin alphabet and numerals. Tracklia and Google Earth mobile apps were used to determine the geographic coordinates of objects in the fieldwork. ArcGIS v10.6.1 (ESRI Inc., Redlands, CA, USA) and the WGS 1984 (World Geodetic System 1984) global positioning system [7] were used to create the maps. Statistical analysis was performed on the JASP 14.1 platform.

Study area. Karshi is a southern city in Uzbekistan, located at the foot of the Kungirtag Lowland, in the eastern part of the Kungirtag Desert. The city's geographic coordinates are 38.86119° N and 65.78473° E. The average annual temperature is approximately 16.6°C, and annual precipitation averages 283 mm. The region has a continental climate, with sharp seasonal temperature fluctuations.

Research location. Karshi is one of the southern cities of Uzbekistan, located at the foot of the Kungirtag Lowland, in the eastern part of the desert of the same name. The geographic coordinates of the city are 38.86119° N and 65.78473° E. The average annual air temperature is about 16.6°C, and the annual precipitation averages 283 mm. The region has a continental climate, with sharp seasonal temperature fluctuations. During the year, temperatures vary from -2°C to +39°C, sometimes reaching -8°C in winter and over +41°C in summer. Summer is long, dry, and hot, lasting approximately 3.5–4 months. The average daytime temperature during this time exceeds +32°C, and in July, the hottest month of the year, it often rises to +50°C. Winter in Karshi, by contrast, is cool and generally dry, although in some years it can be snowy and cloudy. It lasts for approximately 3–3.5 months. The average daytime temperature in winter is around +10°C, and the nighttime temperature is around +3.5°C. Minimum temperatures in some years drop to –14°C. January is considered the coldest month: the maximum average daily temperature reaches –1°C, and the minimum is around –8°C. The number of sunny days in winter is 13–15, and the precipitation level ranges from 4.8 to 13.8 mm [8,9]. Thus, the climate of the city of Karshi is characterized as arid, with hot, dry summers and cool, dry winters, which significantly affects the formation of flora and plant communities in the region.

3. Results and Discussion

The grass family (Poaceae) is one of the largest and most significant families of angiosperms, comprising over 11,800 species in 790 genera [10] Historically, grass taxonomy was based on morphological traits, but such approaches did not allow for the reliably establishment of evolutionary relationships between subfamilies. Since the beginning of the 21st century, advances in molecular biology and phylogenetics have led to the formation of a new, genetically based classification of Poaceae.

The first step toward a modern understanding of cereal evolution was the fundamental work of the Grass Phylogeny Working Group (GPWG, 2001), which for the first time constructed a global phylogeny of the family based on chloroplast genes (rbcL, ndhF, matK). This study demonstrated the monophyly of Poaceae and established a division into two main evolutionary lineages – BOP (Bambusoideae, Oryzoideae, Pooideae) and PACMAD (Panicoideae, Arundinoideae, Chloridoideae, Micrairoideae, Aristidoideae, Danthonioideae) [11].

A follow-up to these studies was published by Grass Phylogeny Working Group II (2012), which used more comprehensive chloroplast and nuclear markers. The authors clarified the underlying evolutionary relationships and demonstrated that the transition from C₃ to C₄ photosynthesis occurred independently several times within the PACMAD clade, playing a key role in the adaptation of grasses to arid and tropical conditions [12].

Further development of Poaceae taxonomy is associated with the work of Soreng et al. (2015), who conducted a large-scale revision of the classification based on a combination of morphological and molecular data. These works clarified the relationships between subfamilies and tribes and proposed a detailed global phylogenetic classification of Poaceae, including 12 subfamilies and approximately 50 tribes [13].

The most recent stage is represented by the Grass Phylogeny Working Group III study (2024, 2025), which for the first time used phylogenomic data from nuclear genes (more than 300 loci). Using coalescence models (ASTRAL-Pro) and analysis of gene duplications and losses (GeneRax), a stable family topology was reconstructed despite the presence of individual gene conflicts. The authors confirmed the stability of the division into BOP and PACMAD clades, identified ancient hybridization events, and clarified the origin of key adaptations, including the multiple emergence of C₄ photosynthesis and reticulum evolution [14,15].

A comparative analysis in the table shows that the classification of cereals proposed by the GPWG (2001) laid the foundation for our current understanding of the evolution of the family Poaceae, first recognizing two major clades—BOP and PACMAD (table 1). While the earlier system was based primarily on chloroplast gene data, the current version of GPWG III (2024–2025) relies on a large-scale analysis of nuclear phylogenomic data, which has provided a more robust and accurate reconstruction of relationships. The basic structure of the subfamilies remains intact, but internal relationships have been clarified, and multiple independent origins of C₄ photosynthesis within the PACMAD clade have been confirmed.

Table 1. Comparative characteristics of Poaceae classification according to GPWG (2001) and GPWG III (2024–2025)

A significant contribution to the understanding of chromosomal evolution and ancient genomic rearrangements was made by the study by Tkach, Winterfeld and Röser (2025), where, based on the analysis of genome sizes, paleogenomics and reconstruction of the ancestral karyotype of cereals (Ancestral Grass Karyotype, AGK), it was shown that genomic duplication and structural rearrangements played a key role in the diversification of Poaceae [16].

The results of phylogenomic research are also reflected in applied aspects of botany, including the study of urban floras. In the city of Karshi, members of the Poaceae family play a leading role in the formation of the grass layer and the bioregulation of ecosystems. Thanks to their phylogenetically determined resistance to arid conditions, salinity, and anthropogenic impact, grasses successfully adapt to urban biotopes – roadsides, parks, vacant lots, and industrial sites.

Floristic surveys and network map analysis revealed more than 50 Poaceae species belonging to 27 genera (Fig. 1).

Figure 1. Representatives of the Poaceae family in the urban flora of the city of Karshi (Uzbekistan)

Of these, 37 species belonging to 17 genera belong to the BOP clade (subfamily Pooideae), whose representatives are characterized by a predominantly mesophytic or xeromesophytic ecology and predominate in temperate and relatively cool biotopes. The remaining 13 species, belonging to 10 genera, belong to the RASMAD clade, which unites the subfamilies Panicoideae, Arundinoideae, Chloridoideae, and Aristidoideae. These taxa are typical of arid and subarid conditions and are represented by species with high drought tolerance and adapted to high temperatures, compacted, and saline soils.

The predominance of representatives of the BOP clade (Pooideae) in the urban flora of Karshi, despite the region's arid climate, can be explained by their wide ecological range and ability to adapt to anthropogenically altered conditions. Many of these species (Bromus, Poa, Elymus, Hordeum, Avena, etc.) readily colonize disturbed habitats—roadsides, wastelands, construction sites, and park areas—where microclimatic conditions (shade, temporary moisture, irrigation) partially mitigate the impact of aridity.

At the same time, species of the RASMAD clade (Panicoideae, Arundinoideae, Chloridoideae, Aristidoideae) reflect the natural aridity of the area and form a stable core flora characteristic of the southern regions of Uzbekistan. They are distributed predominantly in dry areas, along sidewalk edges, near roads, and on open, sunny slopes, where they exhibit typical xeromorphic adaptations – narrow leaves, a waxy coating, C4 photosynthesis, and the ability to undergo prolonged seed dormancy.

Thus, the structural relationship between representatives of the BOR and RASMAD clades in the urban flora of Karshi reflects both historical and floristic connections with boreal elements of the flora and the modern adaptation of grasses to the extreme conditions of the urban environment in the arid zone.

Among the representatives of the Poaceae family, the most widespread in the urban flora of the city of Karshi, species with a wide ecological range and high adaptive capacity predominate. Among the most common are Cynodon dactylon (L.) Pers., Echinochloa crus-galli (L.) P. Beauv., Phalaris minor Retz., Phragmites australis (Cav.) Trin. ex Steud., and Poa bulbosa L. (Fig. 2).

Figure 2. The most common species of the Poaceae family in the urban flora of the city of Karshi

The genera with the largest number of species are Bromus L. (9 species), Hordeum L. (4), Setaria P. Beauv. (3), Poa L. (3), and Lolium L. (3). The remaining genera are typically represented by 1–2 species. Taxonomically, this indicates a high representation of both synanthropic and natural steppe and desert flora elements.

An analysis of life forms reveals that annual (therophytic) grasses predominate, comprising approximately 65% of all identified species (Bromus tectorum, Aegilops cylindrica, Eremopyrum bonaepartis, Polypogon fugax, Setaria viridis, etc.). These species are characterized by a short life cycle, the ability to quickly complete vegetation in arid conditions, and the ability to produce numerous seeds, which ensures their successful existence in urbanized landscapes.

Perennial species (Dactylis glomerata, Cynodon dactylon, Poa pratensis, Stipa hohenackeriana, Stipagrostis pennata, etc.) are found primarily on the outskirts of the city, in parks and roadside phytocenoses, as well as in areas with remnants of natural vegetation. Their presence indicates the preservation of fragments of zonal phytocenoses and the resilience of individual urban ecosystems to anthropogenic impacts.

Poaceae species are distributed according to their ecological distribution as follows:

- xerophytes and mesoxerophytes (approximately 46,5%) — typical of open, dry areas, wastelands, and roadside areas (Bromus danthoniae, Stipa szovitsiana, Eragrostis pilosa...);

- mesophytes (42,5%) — found in parks, courtyards, and irrigated areas (Poa pratensis, Lolium perenne, Dactylis glomerata...);

- hydrophytes and halophytes (11%) — represented by coastal-salt marsh flora species (Phragmites australis, Aeluropus littoralis, Imperata cylindrical...).

The dominance of xerophytic and mesoxerophytic species (about 46,5%) confirms the influence of the arid climate, low air humidity (up to 5%) and extreme temperatures in summer (up to +50°C) on plants growing in the city of Karshi (Uzbekistan).

Of interest is the presence of halophytic species (Aeluropus littoralis, Imperata cylindrica, Phragmites australis) in the urban flora, which is associated with the presence of saline and waterlogged microbiotopes—along the edges of irrigation ditches, collectors, and reservoirs. This demonstrates the high ecological range of Poaceae, which are capable of colonizing both saline and dry habitats.

The Poaceae composition of the Karshi urban flora reflects Eurasian, Mediterranean, and Iranian-Turanian floristic elements, typical of southern Uzbekistan. Most species belong to the Eurasian and Mediterranean floristic elements, reflecting their adaptation to the region's continental climate.

A significant proportion are adventitious and ruderal species (Bromus tectorum, Aegilops triuncialis, Setaria verticillata, Sorghum halepense), which actively spread along transport routes, construction sites, and waste fields. These species play a key role in the formation of primary successions on disturbed substrates.

Members of the Poaceae family help stabilize soil cover, preventing erosion, and form the basis of the green framework of urban areas. Some species (Cynodon dactylon) form lawns, while others are found only in lawns (Poa pratensis, Dactylis glomerata). Furthermore, some species (Sorghum halepense, Setaria viridis) act as noxious weeds, capable of reducing the bioproductivity of agrocenoses and disrupting natural phytocenoses.

The most common genera – Phararis, Phragmites, Cynodon, Setaria, Sorghum, Echinochloa and Hordeum – demonstrate a high level of ecological plasticity and resistance to stress factors. Representatives of Poa, Bromus, Setaria, and Digitaria are very common in lawns.

Overall, representatives of Poaceae occupy a leading position in the urban flora of Karshi, characterized by high species diversity and a wide ecological range. Due to this, grasses dominate all stages of anthropogenic succession –from initial ruderal to secondary steppe communities. Their morphobiological characteristics, reflecting profound evolutionary mechanisms, ensure the dominance of this family's species in the synanthropic vegetation of Karshi and demonstrate the high adaptive capacity of Poaceae in the arid urban ecosystems of southern Uzbekistan.

The results of the study show that the Poaceae family occupies a key position in the urban flora of the city of Karshi, which is in line with global trends [17,18]. A high proportion of representatives of the Poaceae family is characteristic not only of the urban flora of the city of Karshi, but also of other regions of Uzbekistan. Thus, 32 species of cereals have been recorded in the urban flora of Bukhara, which makes up 13.33% of the total flora [19], and in Andijan — 52 species, or 14.6% [20].

4. Conclusions

Modern phylogenomic studies have confirmed that the Poaceae family is a monophyletic group, structured into two main evolutionary lineages—BOP and PACMAD – identified by the GPWG (2001). Advances in molecular and genomic methods, particularly within the framework of GPWG III (2024-2025), have significantly refined the phylogeny of cereals and revealed ancient hybridization events and the multiple independent emergence of C₄ photosynthesis. As a result, the current classification, based on nuclear phylogenomic data, is the most stable and reflects the true evolutionary relationships within the family.

Floristic studies have shown that the Poaceae family is one of the dominant components of the urban flora of Karshi, comprising over 50 species from 26 genera. The high proportion of therophytes and the predominance of xerophytic and mesoxerophytic forms reflect the adaptation of grasses to the region's arid conditions and their resilience to anthropogenic impacts. The diversity of ecological groups – from halophytes to mesophytes – testifies to the broad ecological range and flexibility of family members. The data obtained confirm the global trend of grass dominance in the urban floras of arid regions and highlight their key role in shaping the vegetation cover of Karshi.