Notes on the Distribution of the Russian Thistle (Salsola kali L. var. tenuifolia) in Mexico

Abstract

THE Russian thistle (Salsola kali L. var. tenuifolia Tausch) called T in some parts of Mexico saladilla is an important weed in the dry regions of the United States. It was introduced in 1873 or 1874 to South Dakota and from there migrated to the West and Southwest, reaching California between 1892 and 1895 (6), where it constitutes a serious problem. The fast invasion by this plant of the United States semiarid lands would be expected to continue into the Northern States of Mexico in which a semiarid climate is found too. However, it was not reported by Muller, either in Nuevo Leon (4) or in Coahuila (5), as late as 1947; also, it is not reported by Leseur who studied the northern part of Chihuahua (3). It seems that S. Kali did not exist abundantly on the other side of the border because Cory and Parks in 1937 (1) mention it in their Catalogue of the Flora of Texas but Reeves and Bain do not include it in 1947 as a component of the flora of South Central Texas (7). Indeed some individuals were present in Mexico, but probably in a very scanty number; thus Johnston (2) reports that Endlich collected the species between Mapiml and Ojuelos, Durango (Figure 1); however the plant was not found by Johnston, who collected in the States of Chihuahua, Coahuila and Northern Durango and Zacatecas. It is interesting to note that the plant was seen by only one worker rather far south from the border and none was found in the northern parts of Mexico. In recent papers by Rzedowski (8, 9) the plant is not mentioned either; however, in a personal communication it was indicated that this author collected Salsola both in Zacatecas (12 Kms. NE from Concepcion del Oro) and San Luis Potosi (10 Kms. S from El Salado). In 1957, Vald's2 collected in various regions of Northern Mexico and found the plant around Torreon, Coahuila (Figure 1). Again, the species was found far from the border and apparently still scarce. In October 1958, the senior author collected samples of S. kali, West from Monterrey, Nuevo Leon (Km. 333 on the highway to Saltillo) and he was told that the weed was established south of Saltillo in potato fields. In the summer of 1959 collected in the central and northeast part of Me1xico and observed Salsola in the following points (Figure 1):