Morphometric studies of the Euphorbia esula group (Euphorbiaceae) in North America

Abstract

Leafy spurge and cypress spurge are important weeds of pastures and unimproved rangeland in western and eastern North America, respectively. Taxonomists disagree as to whether leafy spurge is a single variable species or an aggregate of two or more species. Morphometric techniques (clustering by incremental sum of squares and principal coordinate analysis) were used to analyze relationships in leafy spurge and its allies. On the basis of studying 26 morphological characters found in 200 collections representing 32 putative taxa, we concluded that in North America only four species should be recognized, namely, Euphorbia agraria Bieb., Euphorbia cyparissias L., Euphorbia esula L., and Euphorbia ×pseudoesula Schur. A key to these taxa is provided. No authentic material of Euphorbia lucida Waldst. & Kitt. and Euphorbia salicifolia Host was found from this continent in the collections we examined.

Multiconfigurational second-order perturbation study of the decomposition of the radical anion of nitromethane

“…Fermi and Teller 3 predicted that a fixed ͑nonrotating͒ dipole should bind an electron when the dipole moment is larger than 1.625 D. Later, Crawford and Garrett 4 established that a molecule should permanently bind an electron when its dipole moment was higher than Ϸ2.5 D. The dipole moment of neutral nitromethane ͑3.46 D͒ 5 is well above this lower limit. Indeed, the nitromethane radical anion (CH 3 NO 2 Ϫ ) can be formed from the neutral molecule (CH 3 NO 2 ) by different experimental methods: ͑i͒ electron impact, 6,7 ͑ii͒ collisions with atoms in highly excited Rydberg states, 1,2,6,8 or ͑iii͒ collisions with alkali atoms. 9 Gruzdkov and Gupta 10 have also proposed that CH 3 NO 2 Ϫ is an intermediate in the decomposition of amine-sensitized nitromethane shocked to 12-17 GPa peak pressures.…”

Application of chemotaxonomy of leafy spurges (Euphorbia spp.) in biological control

“…The use of morphological characteristics alone to distinguish leafy spurge species was shown by Ebke and McCarty (5) and Harvey et al (8) to be of only limited value in the identification of leafy spurge, subsequently described by Crompton et al (3) and Stahevitch et al (19) to be E. esula. Mahlberg et al (9,10,11) demonstrated that the triterpenoid profile could be diagnostic for given taxa within the Euphorbiaceae and considered the potential value of triterpenoid analysis to the identification of plants of the E. esula complex.…”

“…Leafy spurge is a deep-rooted perennial with broad ecological tolerance introduced from Eurasia into North America where it is estimated to cover more than one million ha of rangeland (3).…”

“…(as Euphorbia waldsteinii (Sojac)), but there is considerable morphological variability between members comprising the complex and identification is not easily achieved on morphological characteristics alone. Recently Crompton et al (3), in a morphometric analysis on spurge material, concluded that leafy spurge should be considered as a single morphologically variable species, E. esula. Previous studies of cytotaxonomy (12,17,18) and cytogenetics (19) also had indicated the close association between E. esula, E. virgata, and Euphorbia × pseudovirgata.…”

GALL INDUCTION BY PEGOMYA CURTICORNIS (STEIN) (DIPTERA: ANTHOMYIIDAE) WITHIN THE ROOTS OF SPURGES EUPHORBIA VIRGATA WALDST. AND KIT. AND E. ESULA L. (EUPHORBIACEAE)

“…and Kit. More recently, 10 additional root galls were found on E. esula [for the taxonomy of E. esula group see Crompton et al (1990) and references therein]. Galls were removed from their hosts in early June; the four from E. virgata and two from E. esula were fixed in Formalin -acetic acid -alcohol (FAA) and sent to the first author for processing.…”