ADDITIONS AND UPDATED NAMES FOR GRASSES OF DURANGO , MEXICO

Twelve years after publication of the floristic treatment “Las Gramíneas de Durango”, a list of accepted names is updated based on recent botanical work in Durango, Mexico. Ninety-one genera, 367 species, 15 subspecies, 55 varieties and 2 forms are included. Of these, 14 genera are newly recognized for Durango, whereas 17 genera previously reported from the state are now treated as synonyms, and three genera previously recorded are excluded. At the specific and infraspecific levels, 46 changes for synonymy occurred. Fifteen species were excluded, while 43 species and 27 infraspecific taxa were added. Four species are reported as new records for the state.


INTRODUCTION
Because of the great economic importance and large size of the family, the nomenclature of Poaceae is huge and elaborate.The first comprehensive treatment of grasses from North America was prepared by Beal (1896) and later Hitchcock (1913) prepared a treatment of Mexican grasses.In addition to making plant collections throughout the continent since the end of the 19th Century, American agrostologists continued to verify the identity of the taxa, as well as describe and apply names to new species.As a result of their efforts, a number of important floristic and floristic-ecologic reports from large regions have been published, e.g., North America (Hitchcock, 1935 andHitchcock &Chase, 1951), "Nueva Galicia" (McVaugh, 1983), and "The grasslands of Durango" (Gentry, 1957).Most taxa have more than one name, because they were described by different authors, and some names have been repeatedly misapplied to different species.In both cases, valid names since have been established with the later names relegated to synonymy.
The first important catalogue of grasses in the New World was the "Index of American grasses", edited by Chase and Niles (1962), who included all accepted names and synonymy known at the time.Another very recent compilation of this kind is the Catalogue of New World Grasses (Soreng et al. 2013, http://www.tropicos.org/Project/CNWG, continually updated) with hard copies published by subfamilies (Judziewicz et al. 2000, Peterson et al. 2001, Zuloaga et al. 2003, and Soreng et al. 2003, 2013).Dávila et al. (2006) compiled and edited the corresponding data of the accepted names and synonymy for the Mexican taxa in the "Catálogo de las Gramíneas de México".The present article is based on these two last catalogues, and has been further enriched by recently published treatments (e.g., Finot et al. 2004, Bess et al. 2006, Zuloaga et al. 2007, Bell and Columbus 2008, Valdés-Reyna et al. 2009, Columbus and Smith 2010, Peterson et al. 2010, Chemisquy et al. 2010, Peterson et al. 2012) and/or additions of new described species (Finot et al. 2004, Peterson et al. 2004, 2006, Peterson and Columbus 2009).In addition, I have included new reports based on review of recently collected grass specimens in the state of Durango (Herrera Arrieta et al. 2004, Herrera Arrieta and Cortés Ortíz 2009, 2010, Herrera Arrieta et al. 2012).
In conjunction with projects that the Mexican Comisión Nacional para el Conocimiento y Uso de la Biodiversidad (CONABIO) has funded to pursue biodiversity research, I have found that there are substantial changes that should be reported to the community of agrostologists, grassland students, and general users.These include newly found taxa, new synonyms, and corrections to erroneous determinations.The purpose of the current study is to review these changes and provide an updated list of the names of the currently accepted taxa for Durango.

MATERIALS AND METHODS
Grass specimens from Durango are constantly being deposited by scientists and students at the CIIDIR herbarium, and this material has been the source of new records during the past 12 years.In addition, other important herbaria with many Mexican collections were examined: CHAPA, ENCB, HUAA, IEB, MEXU, SLPM, TAES, US.Most of the synonyms and nomenclatural changes follow those given in the Catalogue of New World Grasses (Soreng et al. 2013, http: //www.tropicos.org).

RESULTS
Tables 1 and 2 show the numerous modifications at the generic, specific or infraspecific level for grasses in Durango that have occurred during the last 12 years.Accepted taxa are displayed in bold.
In summary, an additional 15 genera are currently recognized as occurring in Durango (these indicated by * in Table 1 and 2), whereas 17 genera previously recognized for the state are now treated as synonyms (**Table 1).Three previously recorded genera are excluded: Allolepis Soderstr.& H.F. Decker, Guadua Kunth and Setariopsis Scribn.Guadua was based on an erroneous determination; Allolepis and Setariopsis were cited for Durango but a specimen was never found.
Forty-six changes due to synonymy occurred at the specific and infraspecific level (Table 1).

Table 1 .
Poaceae with nomenclatural changes.i) Species now considered synonyms of other species (either staying in the same genus or transferred to a different one).ii) Species for which the current recognized genus was segregated from another.iii) Species for which the previously recognized genus was synonymized under another.* New genera recognized as occurring in Durango.**Genera in synonymy.

Table 2 .
Additional taxa (species and infraspecific taxa) not reported in 2001.i = New records for Durango; ii = Recently described species not listed in Herrera Arrieta, 2001; iii = Reported in Herrera Arrieta et al., 2012; iv = Reported in Herrera Arrieta & Cortés Ortíz, 2010; v = excluded in 2001 but now confirmed to occur in the state.