Materials and methods

We reviewed family literature including monographs, floristic lists, floras, species original descriptions, thesis, typification literature, nomenclatural synopsis, and phylogenies. The complete list of references is available from Comisión Nacional para el Conocimiento y Uso de la Biodiversidad (CONABIO), or from the authors. With that information and our experience, we validated the correct name for the species and formed the Solanaceae list. We visited MEXU, XAL, MO, IBUG, IEB, SD and QMEX (acronyms according to ^{Thiers, continuously updated}) to review the specimens and obtain their distribution. The list up to 2011 including synonyms is available at <http://www.conabio.gob.mx/institucion/proyectos/resultados/InfHS004.pdf> (consulted in feb 2017).

Species distribution information at the state level was completed with recent floristic lists. Lists prior to 2000 were not used because of nomenclatural problems. Subfamily and genera circumscriptions are according to ^{Hunziker (2001)}. We do not include subgenera or sections here, but the complete nomenclature data base is available from CONABIO. For discrepancies among different classification systems we followed ^{Hunziker (2001)}. Exceptions are the Mexican genera Calibrachoa and Tzeltalia, which ^{Hunziker (2001)} left as synonyms of Petunia and Physalis, respectively, but ^{Olmstead et al. (2008)} and ^{Whitson & Manos (2005)} recognize. Based on molecular data (such as ^{Bohs & Olmstead 1997}), Lycopersicon and Cyphomandra were included in Solanum, although ^{Hunziker (2001)} treated them separately. Finally, we accepted Capsicophysalis and Schraderanthus, described after ^{Hunziker’s (2001)} work.

Results

The list we present (Table 1), has the species described so far excluding synonyms. We found three subfamilies of Solanaceae that group 34 genera, 381 species, and 18 varieties (Figure 1). Genera with the highest number of species were Solanum with 130, Physalis with 65, Cestrum with 42, and Lycianthes with 40. The rest of the genera have 17 species or less (Figure 1). From the genera present in the list, Brugmansia is introduced from South America and is cultivated for its showy flowers known as “floripondio”. Petunia is also introduced and easily cultivated, and Petunia hybrida is the species with the widest distribution in the country, along with “chile” (Capsicum annuum). Finally, Nicandra physalodes, native from Peru (^{Hunziker 2001}) is currently naturalized in 10 states. The rest of the genera are native, although some of the species are introduced, either as food, like the potato (Solanum tuberosum), or as weeds as Nicotiana glauca Graham (“tabaquillo”, “alamillo”). No genera are endemic to Mexico, but Nectouxia (monotypic), grows from southern Texas to Puebla, Datura and Chamaesaracha grow from southern United States to Mexico and thus the three genera are MegaMexico 1 (sensu ^{Rzedowski 1993}) endemics, although several Datura species have become naturalized in Asia, South America and Africa. Other genera have endemic distributions to Mexico and northern Central America (MegaMexico 2, sensu ^{Rzedowski 1993}), as Tzeltalia, Capsicophysalis (monotypic), Schraderanthus (monotypic), and Plowmania (monotypic) (^{Hunziker 2001}).

Figure 1 Species number per genus of Mexican Solanaceae. 

Mexico is an important diversification center for several genera. For Datura and Tzeltalia, Mexico harbors 100 % of the species, 80 % of Chamaesaracha, 77 % of Physalis and 50 % of Solandra (^{Bernardello & Hunziker 1987}). Some genera are underrepresented in Mexican collections. ^{Nee (1993)} estimated that 150 species of Solanum grew in Mexico, but we only found 130 species with four varieties.

As to species distribution in the country, states with the highest number of species are Oaxaca with 173, Chiapas with 167, Jalisco with 148, and Veracruz with 145 (Figure 2). The states with less species were Tlaxcala with 16, Campeche with 19, and Colima with 27. As to elevation, Mexican Solanaceae grow from sea level to over 4,000 m (Solanum verrucosum Schltdl., ^{Spooner et al. 2004}). Species grow in a wide variety of vegetation types, as halophytes in sand dunes and mangroves, palm strands, tropical deciduous forest, thorn forest, xerophitic scrub, pine-oak forest, mesophytic forest, and grassland (^{Nee 1986 1993}, ^{Spooner et al. 2004}, ^{Knapp et al. 2006}, ^{Cuevas-Arias et al. 2008}, ^{Sierra-Muñoz et al. 2015}). Some species are closely related to water, such as Nierembergia angustifolia Kunth (^{García-Rubio et al. 2004}), Datura ceratocaula Jacq., and Physalis sulphurea (Fernald) Waterf., all of which grow in water-logged soils. Another species that grows near wetlands, but with brackish waters is Solanum tampicense Dunal, a mangrove weed. Physalis minuta Griggs also grows on salty soils near mangroves or coastal line vegetation on the Pacific slope. Nicotiana glauca, Datura innoxia Mill., and Datura stramonium L. have been collected almost through the country and are common in disturbed areas.

Figure 2 Species number of Mexican Solanaceae per state. 

Genera distribution in Mexico is far from homogeneous. Lycianthes has the highest species diversity in Chiapas (25), Oaxaca (19), Veracruz (13), and Jalisco (11), as expected for a neotropical genus, since Mexico and Central America are the areas with the highest number of species (^{Hunziker 2001}). Chamaesaracha, excluding Chamaesaracha rzedowskiana, is a genus with arid affinities, and the states with highest number of species are Coahuila (8), Nuevo León (8) and Chihuahua (6). Aguascalientes is the southernmost limit for the genus. Lycium also has an affinity for dry climates, and has the highest number of species in the northern portion of the country. Cestrum is best represented, as to species diversity and endemism, in the mountains. Two important areas are the Transmexican Volcanic Belt, and the mountains of Chiapas (^{Nee 2001}). Physalis has the highest number of species in the central portion of the country, especially along the Transmexican Volcanic Belt and Jalisco (^{Vargas-Ponce et al. 2003}).

One hundred thirty-five species with eight varieties (Table 1) are endemic to Mexico. In Physalis, 37 out of 66 species are endemic, and P. angustior Waterf., P. tehuacanensis Waterf., P. hunzikeriana M. Martínez are microendemic and rare, known only from the type and a few more collections. Cestrum has 18 endemic species, and sect. Habrothamnus, with diurnal flowers, is endemic to Mexico and Guatemala (^{D’Arcy 1999}). Other genera with endemism to the country are Solanum, with 45 species and one variety, Lycianthes with 10 species and 2 varieties, Datura with five species, Jaltomata with 3 and Lycium with 5 species and 5 varieties. In addition to the geographic limits of the country, 30 species and 5 varieties are endemic to MegaMexico 1, and 57 to MegaMexico 2. The endemic element of Chiapas and Guatemala is very important in Mesoamerica. ^{Knapp et al. (2006)} point out that out of 98 species endemic to Mesoamerica, 45 are restricted to Chiapas and Guatemala.

Discussion

Species estimates for the Valley of Mexico, Veracruz, Jalisco, Aguascalientes, and Bajío (Querétaro, Guanajuato, and northern Michoacán) are probably very close to the actual figures. However, other states seem to be underrepresented in the visited herbaria, as Campeche (with 18 species in ^{Knapp et al. 2006} and 19 in our work), which was collected for the Flora Mesoamericana project. We consider that Campeche needs a higher collection effort for the Solanaceae, since Tabasco harbors 45 species, only 15 of which had already been listed by ^{Knapp et al. (2006)}. Colima (with 27 species) and Baja California Sur (with 27) are probably also under collected, because the state area and orography make such low numbers unlikely. Tlaxcala is the state with less species, but its small size and high vegetation deterioration probably account for such a low number.

Solanum is the most species rich genus in Mexico (130 species), but the number is not high if the high number of species in the genus is considered. It is estimated in around 1,000 species (^{Nee 1999}), 850 of which are American. ^{Nee (1993)} estimated that Mexico had probably around 150 species of Solanum, and therefore more collection is needed, a notion that seems reinforced by the high number of species known only from type material. Several species of Cestrum are also known only from the type. We included three Cestrum species (C. pallidissimum Francey, C. schiedei Francey, and C. subcordatum Francey) that were excluded by ^{Nee (2001)}, and for which specimens are lacking in the reviewed herbaria. A much needed taxonomic revision of the genus, beyond the scopes of our work, might reduce the three species to synonymy. Finally, the presence of Chamaesaracha edwardsiana Averett in Mexico is taken from the genus revision (^{Averett 1973}), which cited collections from Texas, Coahuila, Nuevo León, and San Luis Potosí. ^{Turner (2015)} considers that the Mexican specimens belong to Chamaesaracha pallida Averett, and C. edwardsiana as endemic to Texas. A better analysis of the vouchers is needed, since pubescens density, considered a diagnostic character for species delimitation, is highly variable.