Background and Aims:

The state of Tamaulipas is located in northeastern Mexico, a region conside-red species-rich in oaks; however, inventories and tools for identifying species of the genus Quercus are lacking. The aim of this work is to know the species richness of the genus Quercus in Tamaulipas, as well as provide tools for identifying them.

Methods:

The specimens of the genus Quercus deposited in the herbaria CHAP, ENCB, FCME, HUAP, INEGI, INIF and MEXU were reviewed; additionally, the scanned specimens of the genus Quercus of Tamaulipas from the herbaria MO and K were consulted on the Tropicos web page, as well as the types available on the page JSTOR Global Plants. Parallely, publications about Tamaulipas with emphasis on floristic lists including the genus Quercus were reviewed, resulting in a preliminary list of species collected and reported for this state. The review of specimens and the recognition of respective synonyms allowed to purify the list of species. Based on this information descriptions of the oak species were prepared.

Key results:

We recognize and describe 37 species of the genus Quercus for Tamaulipas; 20 belong to the section Lobatae and 17 to the section Quercus. In addition, a dichotomous identification key is provided, as well as drawings, distribution and phenological data of each species.

Conclusions:

The presence of Quercus durifolia, Q. invaginata, Q. paxtalensis, and Q. potosina has been confirmed, which had not been mentioned before for the state. Tamaulipas ranks fifth in terms of oak richness, after the states of Oaxaca, Puebla, San Luis Potosí, and Jalisco. Oak species richness is concentrated in southern Tamaulipas. Miquihuana, Jaumave, and Victoria are the municipalities with the largest diversity of oaks. Fieldwork should be carried out to increase collections, which will cer-tainly result in modification of the species numbers of the present study.

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