Background:

Floristic knowledge of Northwestern (NW) Mexico was mainly carried out by American botanists until the first half of XX century.

Question:

Do the ancient and recent botanical explorations carried out in the study area, are already enough to document in a conclusive way both the floristic and structural composition?

Methods:

The authors are botanists and managers of the herbaria included in the floristic compilation (BCMEX, HCIB, SD, and USON), each herbarium has been devoted to document the flora of the states of NW Mexico in the last three decades. The floristic information was obtained mainly of the herbaria databases (around 110,000 entries), historic bibliographic information and recent collects from the same authors. The databases consulted are composed by 27,117 collect sites.

Results:

The final database obtained consists of 5,865 taxa at the species level and intraspecific categories. By state, Sonora is the most biodiverse with 3,762 taxa, Baja California has 2,583 and Baja California Sur has 2,070. The Mexican NW is relatively poor in total number of species, but the number of endemic taxa is high. Within this region there are 941 endemic species, where 294, 391, and 79 correspond to the states of Baja California, Baja California Sur, and Sonora, respectively; in addition, there are 177 endemic species shared among these three states. The NW region also has 18 endemic genera, included in 10 families.

Conclusions:

As result of this review, there is excellent floristic knowledge background for NW Mexico, but there are still geographic areas still inaccessible, which includes all kind of topography, that explored could increase the total flora and endemism rate. Presently, the climate change put into risk the species survival, and hence it is a priority that conservation programs be established especially in terms of endemic species, since many of them have a restricted geographical distribution.

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