Background:

Among the flora of the Mexican conifer, oak, and cloud forests, the northern and southern phytogeographic elements stand out; the latter is analyzed in the current contribution.

Question:

In which of the types of vegetation mentioned above are the southern floristic affinities strongest?

Study group:

Phanerogams (Spermatophytes).

Study site:

Essentially, Mexico and South America.

Methods:

A detailed bibliographic review was conducted to prepare a list of Mexican genera that are essentially restricted to the Americas and possess greater diversity in South America than in Mexico. Using pertinent taxonomic revisions and phylogenetic studies, only those genera that have a likely origin in the Southern Hemisphere and belong to families originating in this region are included.

Results:

A catalogue of 84 genera belonging to 39 families of phanerogams is presented. For each genus, the total number of species and number of species in Mexico is provided. The known geographic distribution is also provided, defining the northern and southern limits.

Conclusions:

Based on the list, the following can be inferred: a) Southern affinities are much stronger for the flora of cloud forests than for the floras of conifer or oak forests. b) Most of the southern elements reach their northern limit in central Mexico, some in the state of Chiapas and few extend to Canada. c) Although it is likely that some genera recently arrived in Mexico, many have been present since at least the Early Miocene.

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