Mexico is a megadiverse country, particularly in vascular plants with between 23,500 and 26,500 species of vascular plants recorded (^{Espejo-Serna et al. 2004}, ^{Villaseñor 2016}). It is the third or fourth most biodiverse country in the world at the species level and the richest at the family level (^{Myers et al. 2000}, ^{Villaseñor & Ortiz 2014}, ^{Ulloa-Ulloa et al. 2017}). Mexico’s plant diversity results from its complex geological and climate history, including numerous morphotectonic provinces, and more than fifty types of ecoregions (^{Rzedowski 1978}, ^{Ferrusquia-Villafranca 1993}, ^{Olson et al. 2001}, ^{Kottek et al. 2006}). This geological and ecological complexity has supported the migration and establishment of a large number of plant species (e.g.,^{Dávila-Aranda et al. 2004}, ^{Farjon 2008}, ^{Godínez-Alvarez & Ortega-Baes 2007}, ^{de Nova et al. 2012}, ^{Sosa et al. 2018}, ^{Jiménez-Barrón et al. 2020}).

While our knowledge of the Mexican Flora has advanced considerably, with fifteen regional Floras completed or underway, a Flora comprising the vascular plant species in Mexico has not yet been published. Floras are a crucial source of information and the starting point for many studies (^{Funk 2006}). A complete Flora facilitates recognizing plant diversity patterns, analyzing endemism and identifying endangered species (^{Forest et al. 2007}, ^{Knapp 2008}, ^{Borsch et al. 2020}, ^{Lagomarsino & Frost 2020}, ^{Auffret 2021}). Floras are the cornerstone of managing plant diversity in a region and for prospecting the potential uses of plants in a wide variety of areas: food production, industry, medicine, bioremediation, and soil conservation (^{Funk 2006}, ^{Cutts et al. 2020}, ^{Auffret 2021}).

Bioinformatic tools and various biodiversity databases are currently used in the preparation of modern Floras and accelerate the publication of biodiversity data (^{Berendsohn et al. 2018}, ^{Palese et al. 2019}).

The purpose of this paper is to summarize and evaluate the taxonomic and digital resources and the bioinformatic tools needed to develop an online Flora for the vascular plants of Mexico, and to discuss its potential content.

History of the online Flora of Mexico: eFloraMEX. The Global Strategy for Plant Conservation (GSPC) is one of the United Nations’ programs in the Convention on Biological Diversity (CBD), created to promote conservation and to slow the pace of plant extinction (www.cbd.int/gspc). In particular, Target 1 of the GSPC refers to an online Flora of all known plants (www.cbd.int/gspc/targets). In Mexico, the National Biodiversity Commission CONABIO (Comisión Nacional para el Conocimiento y Uso de la Biodiversidad) developed a strategy that includes an inventory of the vascular plants of the country as one of its targets (www.biodiversidad.gob.mx/pais/emcv/EMCV). In 2015, a group of plant taxonomists and computer science specialists from various Mexican institutions and CONABIO discussed the most efficient approach to accomplishing this goal and concluded that an online Flora would be the optimal strategy and proposed it be called eFloraMEX.

There are several advantages of online Floras compared to conventional Floras published in print. Online Floras can be linked to other biodiversity platforms (^{Schnase et al. 1997}, ^{Brach & Song 2006}, ^{Brouillet 2014}, ^{Victor et al. 2014}) and are easily accessible worldwide (^{Schnase et al. 1997}, ^{Brach & Song 2006}, ^{Brouillet 2014}). They can be published in sections without waiting for all the treatments of all of the plant groups, nomenclatural and taxonomic changes can be easily updated, new species can be quickly incorporated and new collection records and the documentation of extinctions and changes in conservation status can also be continuously updated.

The members of the committee called to accomplish Target 1 of the GSPC by CONABIO explain the strategies proposed for developing eFloraMEX, which include an inventory of the wild-growing native and naturalized vascular plant species of Mexico with their descriptions.

Floristic research and monographs. Efforts to document Mexico’s plant diversity date back to the 16^th century when Francisco Hernández wrote the History of the Plants of New Spain after the first exploration of Mexican territory from 1571 to 1576. More recently, Floras such as the Flora of Yucatan (^{Standley 1930}), the Flora of Baja California (^{Wiggins 1980}), the Vegetation and Flora of the Sonoran Desert (^{Shreve & Wiggins 1964}) and two Floras of the Valley of Mexico (^{Sánchez 1980}, ^{Calderón de Rzedowski & Rzedowski 2001}) were concluded. Others remained incomplete, such as the Flora Novo-Galiciana (^{McVaugh 1974}) and the Flora del Estado de México (^{Martínez & Matuda 1979}). Several other Floras are currently underway, including Flora de Aguascalientes (^{De la Cerda-Lemus et al. 2004}), Flora del Bajío y de Regiones Adyacentes (e.g.,^{Espejo-Serna et al. 2009}), Flora de Guerrero (e.g.,^{Velázquez-Montes 2005}), Flora de Jalisco y Áreas Colindantes (e.g.,^{Carvajal & González-Villareal 2010}), Flora del Valle de Tehuacán-Cuicatlán (e.g.,^{Lira-Charco & Ochoterena 2012} and Flora de Veracruz (e.g.,^{Castillo-Campos 2008}). Additionally, the Flora Mesoamericana includes the southern part of Mexico (e.g.,^{Bravo-Hollis & Arias 2011}). Figure 1 shows the areas covered by these Floras and they are summarized in Table 1.

Figure 1 Geographic areas encompassing previously published floras, either completed or in progress. The floras are cited in Table 1. 

Other efforts include floristic checklists, reviews, and monographs for several vascular plant groups, such as the checklist for the vascular plants of Mexico published by ^{Villaseñor (2016)}. These Floras do not cover the entire Mexican land mass, so additional taxonomic research will have to be conducted. Furthermore, it is difficult to estimate the number of native and naturalized taxa that are in these Floras because many species are shared between regions. Taxonomic concepts also vary among these Floras and need to be reevaluated. The majority of these Floras were published in print rather than in digital format and therefore are not currently suitable for inclusion in eFloraMEX. To assist the taxonomists, it would be helpful to convert these Floras into a machine-readable and marked-up format.

Herbaria and collections. According to the Index Herbariorum (sweetgum.nybg.org/science/ih), the 68 active herbaria for Mexico house approximately 5,300,000 specimens of which 66 % are located in the five largest herbaria in the country (acronyms assigned by the index): MEXU, the National Herbarium, at the Universidad Nacional Autónoma de México, with 1,550,000 specimens; ENCB at the Instituto Politécnico Nacional, with approximately 1,080,000 specimens; XAL at the Instituto de Ecología AC, in Xalapa, Veracruz, with 350,000 specimens; IBUG at the Universidad de Guadalajara in Jalisco with approximately 210,000 specimens; and IEB at the Instituto de Ecología, AC, in Pátzcuaro, Michoacán, with 245,000 specimens. The Mexican Botanical Society assembled an additional database of the Mexican herbaria, including 16 herbaria not yet registered in the Index Herbariorum. Five of them reported their specimens, adding approximately 45,000 to the total. Thus, there is a good number of collections, crucial to developing the online Flora of Mexico. Table 2 summarizes the number of specimens deposited in Mexican herbaria.

The National Herbarium, MEXU, has a virtual herbarium comprising 1,600,000 specimens (www.ibdata.abaco3.org/web/), and some of the herbaria in the Network of the Herbaria of Northwestern Mexico have approximately 5,000 images of herbarium collections (www.herbanwmex.net). In addition, the New York Botanical Garden Herbarium has digitized 72,500 specimens of Mexican plants (^{Thiers et al. 2016}). Approximately 3,900,000 specimens are not yet digitized and their inclusion in eFloraMEX represents a challenge that should be addressed by a specific project. To this end, previous experiences with large-scale specimen digitization, for example that of the New York Botanical Garden Herbarium, should be applied (^{Thomas & Tulig 2015}, ^{Thiers et al. 2016}).

Taxonomists. Approximately 200 systematists are associated with the 71 active herbaria, according to a census by the Mexican Botanical Society conducted on its members. They specialize in very diverse groups, such as Asteraceae, Euphorbiaceae, Fabaceae, Orchidaceae, Rubiaceae, and groups of monocots, the most important being Asparagaceae, Cyperaceae and Poaceae (Table 3). Additionally, taxonomists from all over the world have become interested in groups of Mexican plants and many form part of international networks of specialists in Compositae (www.compositae.org), Caryophyllales (www.caryophyllales.org), Euphorbiaceae (www.euphorbiaceae.org) and Solanaceae (solanaceaesource.myspecies.info) (to mention the most widely known), and they will be invited to participate in this project. In order to sustain a project as ambitious as the online Flora of Mexico, it is also necessary to continue training young specialists to update and complete the treatments. To achieve this, it is important to organize special programs for taxonomists in different graduate programs at universities and research centers in Mexico.

Virtual resources. In addition to the virtual herbaria mentioned above, a number of digital resources are needed to assist collaborators in developing floristic treatments. CONABIO handles the National Biodiversity Information System (SNIB), which contains information derived from research projects on Mexican plant species. The SNIB also contains data from specimens housed in various national and international herbaria from which data was entered during a special project. Also, portals, such as the herbaria of western Mexico (herbanwmex.net) and the Flora of the Yucatan Peninsula (www.cicy.mx/sitios/floradigital/) will be helpful.

The content of eFloraMEX. For every species, eFloraMex will provide: nomenclature, morphological description, distribution (indicating endemic and introduced species), uses, the main specimens upon which the description was based, illustration, conservation status (if available), and important literature with links, if available. The eFloraMex will also provide identification keys, related searchable data, images, guidelines for contributors, and information on the council and its members, the networks of taxonomists collaborating on plant groups and designated coordinators, and on the people involved in the eFloraMEX project. Links to the Mexican herbaria will be included too (Figure 2). The classification of plants for orders and families will follow APG IV (^{APG 2016}).

Figure 2 Workflow for eFloraMEX: the online flora of Mexico. 

For the morphological descriptions of species in the eFloraMEX, ontologies and descriptive terminologies may be standardized or not, however a controlled vocabulary will be utilized for treatments developed specifically for this Flora. Descriptions can be added from other sources, like previous floras or protologues, with the corresponding credit. The selection of characters will be based on comparative observations of a documented set of specimens for each taxon. Specimens will be cited and, if possible, links to images will be included.

The eFloraMEX platform will have wider applications in addition to the flora treatments. It will include distribution maps, the conservation status of species and common names. It will also document uses of native plants since Mexico is an important region for plant domestication, the origin of agriculture and for an ample knowledge of plant uses (^{Bye 1993}, ^{Casas et al. 2016}, ²⁰¹⁹). Illustrations and images for individual species will be included where possible, either prepared specifically for eFloraMEX or obtained from other previously published Floras with the corresponding permission.

Workflow and organization of eFloraMEX. The backbone of eFloraMEX is the checklist and an initial version, a starting point based on previous research and on CONABIO databases, was published in its portal, including approximately 29,000 vascular plant species (efloramex.ib.unam.mx/). The number of species resulted more elevated in comparison with previous estimations (^{Villaseñor 2016}). It will constantly be updated based on taxonomic research from eFloraMEX collaborators, both in Mexico and worldwide.

eFloraMEX will be managed by a council consisting of systematists and bioinformaticians from Mexican universities, research institutes and CONABIO (Figure 2). The council will make the main taxonomic and technical decisions. It will also organize networks of expert botanists who manage the taxonomic backbone and content of plant groups within their expertise, thus integrating and encouraging participation and collaboration among national and international taxonomists. The lead botanists in charge of organizing contact among plant group specialists should be active researchers on the taxonomy and evolution in their respective plant group. Networks of taxonomists will be organized according to the species richness or complexity of the group, at the level of large genera, tribes, subfamilies, families or groups of related small families. Group leaders will work closely with the council, serving as a bridge to individual systematists. The council will have two chairs, one in charge of coordinating virtual resources and another in charge of coordinating taxonomic research. Proper acknowledgment of and attribution to the authors and contributors will be explicitly required in the eFloraMEX portal.

Technical implementation of eFloraMEX. The EDIT Platform for Cybertaxonomy (cybertaxonomy.org/) will be used for developing eFloraMEX. It is a collection of open source tools that cover all aspects of the taxonomic workflow, including (but not limited to) editing taxon names, preparing taxonomic treatments, generating distribution maps, adding factual data of various kinds, such as morphological descriptions in various formats, diagnoses, common names, distribution, ecology, and much more (^{Ciardelli et al. 2009}). The EDIT Platform consists of three components: an instance (database) that stores the information, the TaxEditor, a graphical user-friendly interface that allows data to be entered and edited, and a data portal which displays the data and can include additional textual information. The EDIT Platform covers the whole taxonomic workflow including publication; components for print-publications, for example checklists or taxonomic treatments can be produced directly from the database (^{Berendsohn et al. 2018}). The EDIT Platform is already being used for several online Flora projects. Examples include the Flora of Greece (portal.cybertaxonomy.org/flora-greece/), the Flora of Cuba (portal.cybertaxonomy.org/flora-cuba/), and the Flora Malesiana (portal.cybertaxonomy.org/flora-malesiana). The management of the data, web portal and technical support will be provided by a working group of bioinformaticians associated with the eFloraMEX council, in collaboration with the specialists of the Botanical Garden Berlin, Germany, where the EDIT Platform is being further developed.

Interoperability. The eFloraMEX will make use of existing sources of information and incorporate the scientific community, with the proper identification of authors and contributors. This will be facilitated by the digital resources mentioned above. Also, data bases such as the Global Biodiversity Information Facility GBIF (^{Telenius 2011}), which provide free, open access to an enormous array of digital resources in the taxonomic literature, as well as specimen and observation records, will be linked in the eFloraMEX portal. Additionally, eFloraMEX will include connections to important plant diversity databases such as Tropicos curated by the Missouri Botanical Garden, which includes more than one million links to scientific names, references and publications (www.tropicos.org). The World Flora Online (WFO), the international initiative providing a global overview of the diversity of plant species is another important link for the eFloraMEX (www.worldfloraonline.org). The Biodiversity Heritage Library (BHL) is an open access digital library for biodiversity literature and archives and an important resource for taxonomists interested in the vascular plants of Mexico (www.biodiversitylibrary.org). These databases and others considered in particular for certain plant groups will be linked in the portal of the eFloraMEX.

The benefits of eFloraMEX. The eFloraMEX will present the most up-to-date taxonomic information on the Flora of Mexico to a global audience and contribute to biodiversity conservation and sustainable development. eFloraMEX will focus on the needs of users by providing original data and links to searchable online databases. For instance, data on the habitats of species, elevation ranges, conservation status and uses can be obtained via searches. Students, botanists and amateurs interested in a particular plant group or in plants from a geographic region will be able to directly contact experts associated with eFloraMEX and provide new information on species or their concepts, increasing the interest and participation of botanists.

Challenges, Prospects and Conclusions. The Brazilian Flora represents an admirable achievement that has demonstrated the utility and feasibility of an online flora of a megadiverse country. Over 12 years, a joint effort by approximately 1,000 taxonomists using cybertaxonomy has produced an updated account of algae, fungi and plants totaling ca. 47,000 species (^{BFG 2022}). The remarkable progress of this flora was only achieved by supporting hundreds of graduate and undergraduate students who conducted research alongside experienced systematists, contributing to the professional development of the next generation of botanists (^{BFG 2022}). Also, the World Flora Online has demonstrated the relevance of a compendium of the world’s species based on a collaborative international effort that builds on existing knowledge and published floras, checklists and revisions (^{Borsch et al. 2020}).

There is a worldwide deficiency in essential taxonomic information, gaps in taxonomic knowledge and a shortage of experienced taxonomists and curators. This has come to be known as the taxonomic impediment (^{Lipscomb et al. 2003}, ^{Wheeler et al. 2004}, ^{Crisci 2006}). In this regard, one of the most difficult challenges to overcome in order to complete the Flora of Mexico is the very low number of Mexican specialists (approximately 200 according to the Mexican Botanical Society). The pace and progress of eFloraMEX will therefore greatly depend on bringing aboard undergraduate and graduate students to be trained in taxonomic research alongside experienced taxonomists. Innovative strategies should be designed for attracting young scientists to conduct research in taxonomy.

An additional endeavor, and one that will require a concerted effort, is digitizing the majority of the specimens deposited in Mexican herbaria. This can be only accomplished with a project dedicated to the Mexican herbaria, with the exception of MEXU, the National Herbarium, and the specimens in the Network of the Herbaria of Northwestern Mexico which already have virtual herbaria, the rest have not yet digitized their specimens.

Best practices in taxonomy are crucial to completing the Flora of Mexico and equally important is the need for taxonomists to come together and request sufficient funding, training and employment opportunities for curators, the personnel associated with herbaria and researchers in systematics. Furthermore, E-infrastructures require long-term funding policies because they are of public interest and the eFloraMEX will need continuous support (^{Canhos et al. 2015}). International pleas to consider taxonomy as a modern and active discipline have been expressed previously in many international forums (^{Ebach et al. 2011}, ^{Grieneisen et al. 2014}, ^{Baldini et al. 2021}, ^{Engel et al. 2021}). The online Flora of Mexico should be seen as a project that foments broad participation, and generates understanding of its value and funding from national and international organizations.

eFloraMEX: the online Flora of Mexico is crucial to advancing the inventory of one of the most biodiverse regions on planet Earth (^{Raven et al. 2020}). Mexican botanists have always dreamed of producing the Flora of Mexico and creating the checklist in the portal of eFloraMEX (efloramex.ib.unam.mx) is a first step toward completing this Flora and documenting an important component of the world’s biodiversity.