Acacia chiapensis x A. cornigera . Janzen (1967a, 1974) suggested that some of the morphological variation of Acacia chiapensis is probably an expression of the introgression of A. macracantha and A. cornigera genes into the A. chiapensis population. He found hybrids to be common in a permanently wet site below the dam at Temascal, Río Chichicazapa, and at Arroyo Enmedio, between Temascal, Oaxaca and La Granja, Veracruz, Mexico. On a recent trip (May 1991) to Temascal both A. cornigera and A. chiapensis were common in disturbed sites, but no hybrid individuals were observed.