Xanthium strumarium L. 1753

Sennikov, Alexander N. & Lazkov, Georgy A., 2021, The first checklist of alien vascular plants of Kyrgyzstan, with new records and critical evaluation of earlier data. Contribution 1, Biodiversity Data Journal 9, pp. 75590-75590 : 75590

Xanthium strumarium L. 1753

Xanthium strumarium L., Sp. Pl. 2: 987 (1753).

Xanthium strumarium Xanthium chinense

Xanthium strumarium Xanthium sibiricum

Diagnosis

This species is characterised by unarmed leaves and broadly cylindrical burrs 1-2 cm long with less numerous, sparsely spaced hooked prickles.

Distribution

Native distribution

Pollen and macrofossil evidence suggests that the species is native to the southern temperate zone of Eurasia, stretching from Greece through the Black Sea Basin and the Caspian Sea Basin, including the Middle East and the Caucasus ( Opravil 1983). Recent studies of palaeopalynological records indicate that the eastern limit of its native distribution may extend as far eastwards as to Central India, where its pollen was found in sediments dated over 12000 calibrated years before the present ( Quamar and Kar 2020). The key area for the species seems to be Asia Minor and the South Caspian Region.

In Central Asia, Xanthium strumarium seems to be native in southern Turkmenistan (cf. Nikitin 1960).

Secondary distribution

The species is an archaeophyte in Europe (including a large part of the Mediterranean), Boreal, Central and probably Tropical Asia; it occurs as a neophyte in North and South America and Australia, where its distribution data may be obscured by the confusion with X. orientale .

Although the native distribution of X. strumarium was considered rather uncertain due to its early dispersal by human activities, its archaeophytic occurrence in Central Europe ( Lange 1968, Opravil 1983, Sostarić et al. 2009) and a large part of the Mediterranean ( Opravil 1983) was proven. In Europe, this species belongs to the most widely distributed alien vascular plants ( Lambdon et al. 2008).

In north-western China (Xinjiang), according to the pollen data, the species was introduced about 3700 cal. years before the present, with the expansion of the Andronovo culture ( Tarasov et al. 2019). The invasion of X. strumarium to Xinjiang corresponded to the introduction of wheat cultivation to the territory ( Betts et al. 2014), and Iranian-speaking people of the Androsovo culture seem to have been responsible for both events.

Similarly, wheat cultivation was recorded as present some 4300-4000 cal. years before the present in the steppes near the Dzungarian Range, eastern Kazakhstan ( Frachetti et al. 2010), likely indicating the corresponding expansion of X. strumarium across Central Asia.

The earliest archaeological data from Xinjiang, China ( Sheng et al. 2018) recorded the presence and human use of the species 2200-2400 years ago; this record corresponds to the increase of the Xanthium pollen abundance linked with the intensified human activities through the Silk Road trade connections ( Tarasov et al. 2019).

Wheat cultivation was introduced to Central Asia (Tajikistan and Uzbekistan) from Iran and Afghanistan ca. 5000 years ago ( Spengler and Willcox 2013), and was most likely accompanied by the corresponding invasion of X. strumarium . The introduction of wheat was accompanied by the spread of sheep and taurine cattle in agro-pastoral cultures developed in piedmont areas along main mountain systems in Central Asia, on the way from Iran to north-western China ( Spengler 2015, Stevens et al. 2016), which makes the probability for the arrival of X. strumarium even stronger because this species is a common contaminant of wool and is locally dispersed with sheep and cattle by exozoochory.

Preston et al. (2004) hypothesised that the commonly observed decline of archaeophytes, which occurred largely on arable lands and around human settlements, happened "perhaps because new introductions no longer balance the inevitable losses". We think this explanation is highly likely in the case of X. strumarium . Although this species has a clear adaptation to zoochory and is frequently quoted in connection with this fact, in Kyrgyzstan it was most common on fields and in populated places rather than on pastures ( Deza 1983), thus indicating that the main vector of its local dispersal was management of arable lands. This management implied a constant arrival of new diaspores through contaminated seed. After the Russian colonisation of Central Asia, the original wheat cultivars were replaced by foreign selections due to the constantly increasing demand for higher yields, and the seed material became imported from remote territories. This change implied that the local circulation of wheat weed seeds had stopped or was at least obstructed.

At some point, source fields of the imported wheat seed became infested by X. orientale rather than X. strumarium (cf. Suominen 1979), and new diaspores of X. strumarium no longer arrived to the Central Asian fields. The lack of the outsource renewal, coupled with the constant management of fields and a limited extent of full naturalisation in native habitats, had likely caused a prominent decline of X. strumarium in Central Asia. A similar process had occurred at the same time period in Boreal Europe (e.g. Gudžinskas 1997). In Central Europe, X. spinosum had experienced a similar decline with the recent advancement of agriculture and wool cleaning (e.g. Dudáš and Eliáš Jr. 2021).

According to herbarium collections, in Central Asia, X. strumarium was most likely naturalised in steppe areas along rivers, especially in Kazakhstan. In Kyrgyzstan, its naturalised populations were probably concentrated in the north, along the Chü River, which should be explored for relic occurrences of this species; this territory was found climatically suitable for the naturalisation of X. strumarium s.l., based on the data derived from the current invasion of X. orientale ( Zhang et al. 2021). In other territories, its former occurrences around fields and populated places seem to have been largely ephemeral.

The latest records of X. strumarium are few, and a special effort is required to trace its refugia. We are not aware of any recent collection or observation from Central Asia, whereas one recent specimen was traced from agricultural valleys of northern Xinjiang, China (Fig. 12 ; Seregin 2021).

Distribution in Central Asia

The species was present in all the countries of Central Asia ( Nabiev 1993).

Distribution in Kyrgyzstan

Western Tian-Shan, Northern Tian-Shan, Eastern Tian-Shan, Alay-Turkestan (Fig. 13 ).

The species has been considered occurring in all parts of the country ( Gorbunova 1965, Deza 1983) and was collected from all phytogeographic regions. It occurred in or along all major depressions and valleys.

According to herbarium specimens, the species was found at elevations between 650 and 2100 m, thus covering the territories suitable for agriculture.

Ecology

Same as for Xanthium orientale , but probably less competitive and more confined to steppes rather than to arid depressions; in Central Asia, X. strumarium may reach the altitudes as high as 4000 m ( Nabiev 1993). In Kyrgyzstan, both species occurred in the same habitats.

Biology

Annual.

Introduction to Kyrgyzstan

Period of introduction

Archaeophyte.

The species is an archaeophyte of the Neolithic period, which had arrived with a further development of agriculture.

Pathways of introduction

Transport - Contaminant: Seed contaminant.

The species had likely arrived with the cultivation of wheat, which was introduced to present-day Tajikistan and Uzbekistan no later than 5000 years ago ( Spengler and Willcox 2013). Further dispersal occurred by domestic animals and water ( Ridley 1930).

Invasion status

Naturalised, not invasive. Historically common and abundant, but likely dependent on human management; currently nearly extinct, but probably still resident in the country (current presence is not confirmed, last record dated 1978).

Evidence of impact

Agriculture - minor impact (formerly common weed of fields, gardens and pastures, contaminant of wool; currently not recorded). Native ecosystems - minor impact (formerly extensive occurrence along mountain streams and in steppe-like landscapes around populated places; present-day occurrence is not confirmed). Urban areas - minor impact (former ruderal occurrence).

Trend

Strongly declining (observed).

Figures

Figure 12. A recent specimen of Xanthium strumarium from northern Xinjiang, China (MW 075041).

Figure 13. Historical distribution of Xanthium strumarium in Kyrgyzstan according to the specimens examined.