Background:

Amaranthus palmeri is a dioecious weed that has become an invasive species because of its proliferation ability and high resistance to herbicides. This species is considered one of the most troublesome weed species for the United States of America agricultural system, therefore, the documentation of this species is important for a region that harbors high biodiversity as well as many agricultural activities, as the Peninsula of Yucatan.

Question:

Amaranthus palmeri is distributed in Peninsula of Yucatan.

Studied species:

Amaranthus palmeri S. Watson

Study site:

Two sites in Yucatán, Mexico in 2014, 2017 y 2018.

Methods:

Morphological characters were examined, characterized and measured, and floral characters were photographed.

Results:

Amaranthus palmeri is documented for the first time in the Peninsula of Yucatan. The collected specimens are described. Differences and similarities with other species of the genus in the region are discussed. Intraspecific variation of the populations is reported. A key to the species of Amaranthus in the Peninsula of Yucatan is provided.

Conclusions:

Twelve species of Amaranthus were identified in the Yucatan Peninsula, including A. palmeri. The morphological variation of sepals of the female flowers of A. palmeri might indicate hybridization, phenotypic plasticity or intraspecific variation, which might be related to its ability to adapt to the agricultural systems and artificial environments that colonizes; therefore, the generation of knowledge for this species might be helpful in designing more efficient management solutions.