Hirschfeldia incana (L.) Lagr.-Foss., 1847

Hirschfeldia incana (L.) Lagr.-Foss., 1847 View in CoL

Hirschfeldia incana (L.) Lagr.-Foss. View in CoL , Fl. Tarn Garonne: 19 (1847) — Sinapis incana L. View in CoL , Cent. Pl. I: 19 (1755).

Distribution

Native distribution

Mediterranean, including north-western Africa, south-western Europe, Italy, Greece, Crimea, Asia Minor, Near East, Transcaucasia, Iran and south-western Turkmenistan.

Secondary distribution

Europe, South Africa, temperate North and South America, Australia, scattered localities in Asia.

In North America, the species was noted in California first in 1895 and as a noxious weed in the 1930 s ( Jepson 1936). It is widely naturalised in the western states of the USA ( Rollins 1981) and Mexico ( Villaseñor and Espinosa-Garcia 2004).

In South America, the species has developed an extensive occurrence in argicultural areas ( GBIF 2024), which is also connected with the species dispersal with imported wheat to Europe, as recorded in Finland already in the 1950 s ( Suominen 1979).

In Australia, Hirschfeldia incana was introduced in the late 19 th century and became naturalised in the very beginning of the 20 th century. Its significant field occurrence and grain contamination has been observed in the south-eastern provinces ( Parsons and Cuthbertson 2001), causing the species immigration to Finland with Australian contaminated wheat in the 1950 s ( Suominen 1979).

The territories of the extensive naturalisation of Hirschfeldia incana correspond to grain production areas, thus indicating its major distribution pathway with imported grain. Grain import as a major pathway is indicated by the species occurrence along railway tracks, for example, in Lithuania ( Gudžinskas 1997) and North-Western European Russia ( Tzvelev 2000). The secondary dispersal takes place along roadsides by attaching seeds to vehicles and feet, by road construction and with flowing water ( Parsons and Cuthbertson 2001).

A recent expansion of the species in Britain is connected with the increasing trade of contaminated bird seed since the 1990 s ( Patel 2004). In addition to the previous spread of the species by bread grain trade, we suggest that its recent global dispersal may be largely caused by the increasing production of poultry in the Developing World since the 1990 s ( Narrod et al. 2008), which requires extensive import of grain food that is not sufficiently available in arid countries of Asia, whose climate may be suitable for the species naturalisation.

The exact extension of the secondary spread of Hirschfeldia incana may not be properly documented because its occurrences are largely ephemerous due to its high demand for warm temperatures; this can be demonstrated with an example of Finland in which numerous species records exist because of the dedicated sampling for exotic alien plants ( Suominen 1979). Outside the areas with high summer temperatures, its populations are mostly temporarily persisting and not really established.

Distribution in Central Asia

Kyrgyzstan, Tajikistan, Turkmenistan, Uzbekistan (Fig. 11 View Figure 11 ).

In Central Asia, the species was first found in Turkmenistan in 1946, in a single locality at Ajyýap Village, present-day Esenguly District, Balkan Province, along field margins and in saline lands ( Nardina 1954), although the voucher specimen is currently lacking ( Voitenko 1969). In this area, segetal weeds were numerous and especially abundant along the river ( Nardina 1954), thus showing a developed agricultural activity.

The first record of Hirschfeldia incana in Turkmenistan seems to have been connected with an agricultural region in Turkmen Sahra, Golestan, Iran, a territory historically inhabited by the Turkmen people who were otherwise largely nomadic. Herbarium records from this region uncovered a continuous distribution of the species (Fig. 12 View Figure 12 ). This distribution strongly suggests that the species was present in the territory before the Russian conquest of Turkmenistan. Its status can be inferred as presumably native in south-western Turkmenistan because of its numerous occurrences in the lowlands of Turkmen Sahra, not only as a weed, but also in native plant communities and natural landscapes, as noted by Nardina (1954).

One more historical locality, along the railway near Kushka Station, was observed in 1968 ( Voitenko 1969). This occurrence is apparently connected with the imported wheat grain, from the times of the Soviet food crisis ( Volin and Walters 1965, Moravcik 1978); otherwise, the species would have been noticed in that place earlier, in the course of its botanical exploration since the early 20 th century.

In Kyrgyzstan, the species was first observed as a casual alien in Kyr-Koo Village in 2013 ( Lazkov and Sennikov 2014). The second record, dated 2022, is reported in the present contribution.

In Tajikistan, the species has been recorded only once, as a recent casual introduction in a ruderal place in Dushanbe City, in 2019 ( Ebel et al. 2022).

The species records in Uzbekistan are most recent in Central Asia ( German et al. 2024). In a single year, during 2024, it has suddently emerged in several localities along roads and on city lawns in Tashkent and north-eastern parts of Uzbekistan, often as groups of several individuals. We assume that this introduction has originated from the recent import of foreign fodder grain.

Distribution in Kyrgyzstan

Western Tian-Shan, Alay-Turkestan (Fig. 13 View Figure 13 ).

After the first record ( Lazkov and Sennikov 2014), the species has been recently observed in Sary-Talaa Village in south-western Kyrgyzstan (Fig. 14 View Figure 14 ).

Ecology

Open stony, gravelly, sandy and other dry places in the native distribution area; possibly, the species was originally confined to sandy and gravelly sea shores ( Tzvelev 1977). Nutrient-rich soils are preferred ( Hanf 1983).

Biology

Biennial to perennial, with a slender taproot.

In germination experiments, fruit valves were found to induce seed dormancy, which leads to a seed soil deposit originating from an indehiscent apical segment of the fruit, allowing the species to survive periods of drought and successfully colonise the territory ( Voitenko 1969). A strong relation of seed dormancy with seed size has been recently observed ( Mira et al. 2019).

The requirement for warm temperatures in germination (the maximal germination rate was found in experiments with temperatures between 20 and 35 ° C: Castro et al. (2015)) seems to limit the species naturalisation to the areas with a relatively hot climate.

Taxon discussion

The generic position of the species and, consequently, the generic status of Hirschfeldia were recently challenged ( Al-Shehbaz 2018). Based on the comparative genome studies, it has been established that Hirschfeldia is an ancient intergeneric hybrid lineage that originated from the crosses between Brassica L. and Mutarda Moench ( Hoang et al. 2024) .

The genetic diversity in naturalised populations of the British Isles was found as high as in the native populations and also lacking any apparent spatial structure, thus showing multiple and repeated introduction events that presumably enable the species to colonise new territories ( Lee et al. 2004).

The species may produce hybrids with Brassica napus L., but without successful backcrossing ( Darmency 2002).

Notes

Tzvelev (1977) examined the variability of Hirschfeldia incana in the Crimea and the Caucasus and concluded that three subspecies can be distinguished in that area on the basis of fruit variability (in length, width and lignification of the pods, length and direction of the beak). Most notably, he separated H. incana subsp. leptocarpa Tzvel. because of its long and slender pods with a slender and recurved beak; such plants can be found in the same area as the type subspecies occurring from the Near East to the Transcaucasia, without any spatial pattern and may be best treated at the level of variety, as H. incana var. geniculata (Desf.) Bonnet & Barratte. The plants from Central Asa have shorter pods with a short and straight beak, thus belonging to the type variety (Fig. 15 View Figure 15 ).

Introduction to Kyrgyzstan

Period of introduction

Neophyte.

The species has been observed during the independence time, since 2013.

Pathways of introduction

Transport - Contaminant: Seed contaminant.

Both localities observed in Kyrgyzstan are linked with the import of contaminated grain. The species occurrence along ruderal roadsides strongly suggests its immigration without agricultural activities.

Source of introduction

According to the recent reports of the National Statistic Committee of the Kyrgyz Republic, reproduced in the local news media, Kyrgyzstan largely depends on the massive import of fodder for local farming, also from remote areas like Iran. Fodder grain is used, for example, for feeding chickens in the villages and we assume this country as a likely source of introduction because Hirschfeldia incana is broadly distributed in Iran ( Hedge 1968).

Invasion status

Casual.

The ruderal roadside occurrences observed in Kyrgyzstan are limited in size and do not demonstrate that the species has been naturalised and formed sustainable populations.

Evidence of impact

Agriculture - no impact (not found in cultivated lands). Native ecosystems - no impact (restricted to populated places). Urban areas - minor impact (rarely occurs in ruderal places).

Trend

Increasing (observed and inferred).

With the latest spread of the species in Uzbekistan ( German et al. 2024), we predict that further occurrences may emerge in the future because of the continuous import of contaminated grain fodder. However, the species naturalisation is not expected in arid areas of Kyrgyzstan.