Background:

Attaining a reasonable floristic knowledge for any given region is a progressive task, of gradual, periodic accumulation of data with no deadline, beyond programmatic or budgetary limitations. The knowledge gained synthesized in floristic checklist, regional taxonomic treatments, and floras. The taxonomic studies of particular groups, traditionally known as treatments, frequently reveal changes in the knowledge of biodiversity that must be incorporated periodically into floristic checklist and floras. Also, phylogenetic systematics, especially that based on molecules, has yielded dramatic changes in the way we understand relationships and classify organismic diversity, and also needs to be taken into account. No less important are the regional taxonomic novelties and new species for Science described from material originally collected and / or exclusively in the area of interest, in this case, the Mexican portion of the Yucatan Peninsula (MYP). Finally, practicing systematists often change their opinion in relation to circumscriptions of particular organisms as a consecuence of the evaluation of new evidence. Also, we make mistakes that must be corrected. This work summarizes the daily task of increasing and updating the floristic knowledge of the MYP.

Question:

How many species of vascular plants grow wild in the MYP? How many of these are endemic to this area? What important floristic and taxonomic changes have occurred since the publication of the last checklist? What human resources and infrastructure are currently available to study this flora? What are the gaps in our floristic and taxonomic knowledge?

Studied species:

Gimnosperms, ferns and related groups, Angiosperms.

Study site and and years of study:

The MYP is made up of the states of Campeche, Quintana Roo, and Yucatan. As a biogeographic unit, its extends to the northern portion of Belize (Departments of Belize, Corozal, and Orange Walk) and the Peten in Guatemala. This is a compilation of the advances of our knowledge during the last eigth years (2010-2017) after the publication of the Checklist of the Flora Ilustrada de la Península de Yucatán.

Methods:

The reseach consisted in the revision of botanical literature published during the last eigth years (2011-2017), including information arising from the revision of older literature (from the XIX and XX centuries), a task that allowed us to produce a new floristic synopsis. An assessment of the infrastructure and human resources responsible for generating botanical information in the MYP is also included.

Results:

Our latest account of taxonomic richness for the MYP yields the following figures: 168 vascular plant families, 970 genera and 2,327 species. Of these species, 99 are restricted to the combined Campeche, Quintana Roo and Yucatán three-state area whereas other 85 occur also in the northernmost parts of Belize and Guatemala. There are ten additional species-level taxa that are currently known in these areas of Belize and Guatemala that will possibly be found to occur in the southern sections of the MYP. There are six herbaria in the MYP, housing approximately 140,000 herbarium specimens. There are also about 20 local professional botanists devoted to the study of the MYP flora; these botanists are specialists in the study of circa 15 Angiosperm families, including five of the ten most species-rich plant families (Asteraceae, Convolvulaceae, Fabaceae, Orchidaceae, and Poaceae).

Conclusion:

The MYP is an area of relatively low floristic richness as compared to other areas or biogeographic units of Mexico and the Neotropics: its flora accounts for 9.95 % of the country's total flora and 0. 85 % of its endemic flora (1.58 % if the entire biotic province of the Yucatán Peninsula is considered). This low species richness is best explained, among other factors, by its geographical location, the physiographic homogeneity, the lack of rivers, high, constant temperatures and strong seasonality (precipitation). Unquestionably, a prolonged human presence in the region and an intense human development in the XX and XXI centuries, also has played an important role in the transformation of the vegetal cover.

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