Intraspecific Chemical Variability Research Articles

Chemical composition of precloacal secretions of Liolaemus lizards.

Interspecific chemical variation of precloacal pore secretions of Liolaemus lizards was characterized in 20 species, and intraspecific chemical variation was characterized using nine individuals of L. bellii. The latitude (Chile, 18 degrees to 33 degrees South latitude) and altitude (100 to 4350 m.a.s.l.) of the capture sites were recorded, as well as the number of precloacal pores of each lizard. Secretions were analyzed by GC-MS. A total of 49 compounds were found distributed among the 20 species of Liolaemus. Different chemical patterns occurred at intra- and interspecific levels. Compounds belonged to three main families: n-alkanes, long chain carboxylic acids, and steroids. Cholesterol and five carboxylic acids (tetradecanoic, hexadecanoic, hexadecenoic, octadecanoic, and Z-9-octadecenoic) appeared in all species. The number of precloacal pores correlated positively with altitude and negatively with latitude, suggesting that lizards produce more secretions under harsh environments.

Intraspecific chemical variability of the leaf essential oil of Juniperus phoenicea subsp. turbinata from Corsica.

The composition of 50 samples of essential oil of individual plants of Juniperus phoenicea subsp. turbinata from Corsica was investigated by GC, GC-MS and 13C NMR. alpha-Pinene, beta-phellandrene, alpha-terpinyl acetate, Delta-3-carene, myrcene and alpha-phellandrene were found to be the main constituents. The results were submitted to cluster analysis and discriminant analysis which allowed two groups of essential oils to be distinguished with respect to the content of alpha-pinene, beta-phellandrene and alpha-terpinyl acetate.

Intraspecific chemical variability of the essential oil of Pistacia lentiscus L. from Corsica

Abstract The composition of 105 samples of essential oil of individual plants of Pistacia lentiscus from Corsica was investigated by 13 C NMR and GC. Myrcene, limonene, terpinen-4-ol, α -pinene, β -pinene, α -phellandrene, sabinene, p-cymene and γ -terpinene, were found to be the main constituents. The results were submitted to cluster analysis and discriminant analysis which allowed three groups of essential oils to be distinguished with respect to the content of terpinen-4-ol/ α -pinene, limonene and myrcene.

Chemical variation and defense of Encelia farinosa

Chemical analysis of leaves from 12 different localities of Encelia farinosa (including var. phenicodonta and var. radians) collected on the peninsula of Baja California (Mexico) revealed the presence of various chemotypes that differed with regard to the concentrations of chromenes and sesquiterpene lactones. Localities of E. farinosa collected in the northern part of Baja California were characterized by high concentrations of the chromene encecalin (up to 252 μmol g −1 dry wt.), whereas the sesquiterpene lactone farinosin was not detected. Localities of E. farinosa collected at the southern tip of the peninsula lacked encecalin, but were shown to accumulate farinosin (up to 85 μmol g −1 dry wt.) instead. On the mainland of Mexico, as well as in Arizona (U.S.A.), farinosin concentrations varied from 18 to 44 μmol g −1 dry wt. for 10 different localities analyzed. Chromenes were not detected or present only in minor amounts (up to 13 μmol g −1 dry wt.), when compared to the samples from northern Baja California. Chemical variation within localities was small when compared to variation between different localities. Accumulation of encecalin and aridity seem to coincide at least on the peninsula of Baja California, as localities of E. farinosa that receive the least amount of rainfall contained the largest amounts of encecalin in their leaves. Leaves of E. farinosa that contained sufficiently large amounts of either encecalin or farinosin were both detrimental to neonate larvae of the polyphagous pest insect Spodoptera littoralis as shown by addition of the respective crude leaf extracts to artificial diet. Possible advantages of the observed intraspecific chemical variability of E. farinosa with regard to adaptation by generalist insect herbivores are discussed.

Estudios quimiotaxonomicos de Bursera (Burseraceae). I. Bursera chemapodicta sp. n.

Con el empleo de la cromatografía gas-líquido y analizando el contenido de terpenoides se pretende esclarecer algunos problemas taxonómicos en Bursera. Las primeras experiencias señalaron una gran variabilidad química intraespecífica y se vio que sólo muestreando varios individuos por población se logra una caracterización aceptable de la mayor parte de las especies. Se estudia el caso concreto de una población de la región del Cañón del Zopilote (estado de Guerrero, México), diferenciada por su conspicua pubescencia y al parecer separada a nivel reproductivo del resto de los individuos de B. schlechtendalii EngL., que son perfectamente glabros. Al mostrar que el espectro de terpenoides de dicha población es también distinto en forma significativa, se determina su condición de especie independiente y se la describe como tal.