Systematic Diversity of the Family Poaceae (Gramineae) in Chile

The role of Systematics in studies of biodiversity is essential to a variety of studies, including species conservation, extinction, biodiversity hotspots, bio-prospecting and ecosystem function (Alroy, 2002; Scotland & Wortley, 2003; Smith & Wolfson, 2004; Wilson, 2000). The analysis of the biodiversity as well as the analysis of the distribution of species richness at different levels (national, regional), the distribution of the endemic species, the detection of areas whose preservation is necessary and many other topics related to the conservation of the biodiversity requires an important collection effort, so that the organized databases constructed by the herbaria become as comprehensive as possible. Herbarium specimens represent a rich source of information for botanists and ecologists, even though data based on herbaria collections have many limitations, since they are geographically and seasonally biased, and taxonomically incomplete (Crawford & Hoagland, 2009; Delisle et al., 2003; Fuentes et al., 2008; Funk & Richardson, 2002; Ponder et al., 2001). Moreover, it has been established that there is a tendency to a decline in the number of specimens of vascular plants collected in the last years (Prather et al., 2004), although taxonomists are aware that there are still many undescribed species (Smith & Wolfson, 2004). In order to know how many species of grasses exist in Chile, as well as their identity and taxonomic distribution, this chapter provides a checklist of the family Poaceae in Chile, taking into account the nomenclatural changes recently proposed. Moreover, we analyze the completeness of the inventory of the family represented in two of the most important national herbaria. Grasses (Poaceae or Gramineae) are the fifth most diverse family among the flowering plants or Angiosperms and the second most diverse family among the Monocotyledons. Poaceae comprises about 10,000 species in approximately 700 genera (Clayton & Renvoize, 1986; Tzvelev, 1989; Watson & Dallwitz, 1992). Recent evidence suggests that grasses had already diversified during the Cretaceous. The evidence came from phytolith analysis (Prasad et al., 2005), tiny crystals of silica formed in the epidermal cells of leaves or floral bracts of grasses and other plants. The discovery of grass phytoliths in coprolites of titanosaurid sauropods that lived in India 65 to 71 million years ago (Prasad et al., 2005), suggested that grasses and dinosaurs coevolved (Piperno & Sues, 2005). Phylogenetic approach to reveal the evolutionary history of grasses in a biogeographical context suggests that Poaceae originated in the African or South American regions of Gondwana during the late Cretaceous (Bouchenak-Khelladi et al., 2010).


Introduction
The role of Systematics in studies of biodiversity is essential to a variety of studies, including species conservation, extinction, biodiversity hotspots, bio-prospecting and ecosystem function (Alroy, 2002;Scotland & Wortley, 2003;Smith & Wolfson, 2004;Wilson, 2000). The analysis of the biodiversity as well as the analysis of the distribution of species richness at different levels (national, regional), the distribution of the endemic species, the detection of areas whose preservation is necessary and many other topics related to the conservation of the biodiversity requires an important collection effort, so that the organized databases constructed by the herbaria become as comprehensive as possible. Herbarium specimens represent a rich source of information for botanists and ecologists, even though data based on herbaria collections have many limitations, since they are geographically and seasonally biased, and taxonomically incomplete (Crawford & Hoagland, 2009;Delisle et al., 2003;Fuentes et al., 2008;Funk & Richardson, 2002;Ponder et al., 2001). Moreover, it has been established that there is a tendency to a decline in the number of specimens of vascular plants collected in the last years (Prather et al., 2004), although taxonomists are aware that there are still many undescribed species (Smith & Wolfson, 2004). In order to know how many species of grasses exist in Chile, as well as their identity and taxonomic distribution, this chapter provides a checklist of the family Poaceae in Chile, taking into account the nomenclatural changes recently proposed. Moreover, we analyze the completeness of the inventory of the family represented in two of the most important national herbaria. Grasses (Poaceae or Gramineae) are the fifth most diverse family among the flowering plants or Angiosperms and the second most diverse family among the Monocotyledons. Poaceae comprises about 10,000 species in approximately 700 genera (Clayton & Renvoize, 1986;Tzvelev, 1989;Watson & Dallwitz, 1992). Recent evidence suggests that grasses had already diversified during the Cretaceous. The evidence came from phytolith analysis (Prasad et al., 2005), tiny crystals of silica formed in the epidermal cells of leaves or floral bracts of grasses and other plants. The discovery of grass phytoliths in coprolites of titanosaurid sauropods that lived in India 65 to 71 million years ago (Prasad et al., 2005), suggested that grasses and dinosaurs coevolved (Piperno & Sues, 2005). Phylogenetic approach to reveal the evolutionary history of grasses in a biogeographical context suggests that Poaceae originated in the African or South American regions of Gondwana during the late Cretaceous (Bouchenak-Khelladi et al., 2010).
The economic significance of the grass family is undeniable. Grasses are found on all continents, including Antarctica (e.g. Deschampsia antarctica) and are ecologically dominant in some ecosystems such as the African savannas (Kellogg, 2000). Grasslands, in which grasses are the most important floristic component, cover about 40% of the earth surface (Peterson et al., 2010). Most people on Earth depend on grasses, such as wheat, corn, oats, rice, sugarcane, and rye, for a large part of their diet. In addition, domestic animals are fed on diets based largely on forage grasses. Moreover, many of the most serious weeds growing on agricultural land are also members of the grass family.

Diversity, phylogeny and classification of the grass family
Grasses are unique from a morphological point of view. The grass flower contains a bicarpellary gynoecium surrounded by an androecium composed of three or more stamens in one or two whorls. The perianth is reduced to two or three lodicules situated outside the stamens; the lodicules open the florets during the pollination process. Outside the lodicules, in adaxial position, there is the palea. Subtending the flower there is another bract, the lemma (Kellogg, 2000). The elemental inflorescence is the spikelet, with one to many florets inserted along an axis, the rachilla. Each spikelet has two empty bracts called glumes which protect the immature spikelet. The lemma and the palea enclosing the flower or caryopsis constitute the floret. Lemmas often bear awns or mucros born at the apex or on the back of the body of the lemma. Awns are very common in the family, nearly the half of the genera of Poaceae have awns (GPWG, 2001). The inflorescence (in fact a synflorescence) is a panicle, a raceme or a spike (for a detailed descriptive terminology on grass inflorescence see Allred, 1982). The fruit is a caryopsis or grain; a caryopsis is defined as a one-seeded indehiscent fruit with the seed coat fused with the pericarp (the ovary wall). The embryo is lateral and highly differentiated, with shoot (plumule) and root meristems, leaves and vascular system. The embryo has a scutellum considered to be a modified cotyledon; in many species there is the epiblast, opposite to the scutellum, considered to be a rudiment of a second cotyledon or an outgrowth of the coleorrhiza (Tzvelev, 1983). The epiblast is absent in the subfamilies Arundinoideae and Panicoideae (Clayton & Renvoize, 1986). In the lower part of the embryo the root meristem is covered by the coleorrhiza. In the upper part, the plumule is covered by the coleptile. The embryos of Arundinoideae, Chloridoideae, Centothecoideae and Panicoideae have a mesocotyl (first internode), between the insertion of the scutellum and the coleoptile. The embryos of Arundinoideae, Bambusoideae, Centothecoideae, Chloridoideae, Ehrhartoideae and Panicoideae have a cleft between the coleorrhiza and the scutellum. The plants are annual or perennial, herbaceous or woody. The stems, called culms, are simple or branched and often with rhizomes or stolons. Culms are hollow or more rarely, solid. Roots are fibrous and adventitious (homorriza). Leaves are distichous; the leaves have the basal portion forming the sheath and the upper portion forming the blade. At the adaxial junction of the sheath and blade there is a membranous ligule, sometimes transformed in a fringe of hairs. Most grasses lack an abaxial ligule; an abaxial ligule is present in Bambuseae, some members of the PACMAD clade and a few Pooideae. The sheath is sometimes auriculate. In bamboos, the leaves have a pseudopetiole, a constriction at the base of the leaf blade Two main photosynthetic pathways, C3 and C4, are found in Poaceae but C3/C4 intermediates also occur. In C3 photosynthesis CO2 combines with ribulose 1,5-biphosphate in the Calvin-Benson cycle. The first detectable metabolic product of this process is phosphoglycerate, a compound with three carbon atoms. C3 photosynthesis takes place in the leaf mesophyll. C3 grasses are well adapted to temperate climates. In C4 photosynthesis or Hatch-Slack cycle the first detectable metabolic product is oxalacetate, a compound with four carbon atoms. In C4 grasses, C4 activity is confined to the mesophyll and C3 photosynthesis is displaced to the bundle sheath surrounding the vascular tissue (Kranz syndrome). It is presumed that C4 photosynthesis is an adaptation to low CO 2 levels and high O 2 levels. C4 plants minimize photorespiration sequestering Rubisco in the cells of the bundle sheath making C4 photosynthesis more efficient than C3, especially at high temperatures and arid environments. C4 photosynthesis evolved in four of the 13 subfamilies of Poaceae (Panicoideae, Aristidoideae, Chloridoideae and Micrairoideae). The earliest fossil grass leaves with C4 anatomy is dated 12.5 Ma but Chloridoideae phytoliths have been dated 19 Ma. It has been suggested that C3 photosynthesis is ancestral to the origin of C4 photosynthesis and occurs about 32 Ma during the Oligocene, and that the origin of the C4 pathway is polyphyletic (Vincentini et al., 2008). The family Poaceae is monophyletic. Characters that unambiguously support the monophyly of the family are the grass-type embryo lateral, peripheral to the endosperm and highly differentiated in the caryopsis, and a trnT inversion in the chloroplast genome (GPWG, 2001). The grass family has been divided in a number of subfamilies ranging from two to 13 (for a review see GPWG, 2001). Traditionally, the family was divided in two major groups: Festucoideae (= Pooideae) and Panicoideae (Hitchcock, 1950). The system of grasses (Tzvelev, 1989) also recognized only two subfamilies: Bambusoideae with 14 tribes, and Pooideae, with 27 tribes. In Tzvelev's system, Panicoideae are embedded in Pooideae. One of the most widely used systems is that of Clayton & Renvoize, which divided the family in six subfamilies: Bambusoideae, Pooideae, Centothecoideae, Arundinoideae, Chloridoideae and Panicoideae (Clayton & Renvoize, 1986). The phenetic system of Watson & Dallwitz recognizes seven subfamilies (the same as Clayton & Renvoize + Stipoideae) (Watson & Dallwitz, 1992). The largest proposed number of subfamilies is 13 (Caro, 1982): Bambusoideae, Streptochaetoideae, Anomochlooideae, Olyroideae, Centostecoideae, Oryzoideae, Ehrhartoideae, Phragmitoideae, Festucoideae (= Pooideae), Eragrostoideae (= Chloridoideae), Aristidoideae, Panicoideae and Micrairoideae. The evolutionary history of Poaceae has been deciphered using different molecular markers, such as restriction site maps of the chloroplastidial DNA (Soreng & Davis, 1998), sequences of various chloroplast genes such as ndhF (Clark et al., 1995;Sánchez-Ken & Clark, 2010), rpoC2 (Barker et al., 1999), rbcL (Barker et al., 1995;Sánchez-Ken & Clark, 2010), matK (Hilu et al., 1999), rps4 (Nadot et al., 1994), and sequences of several nuclear genes such as phytochrome B , GBSSI (Mason-Gamer et al., 1998), ITS (Hsiao et al., 1999), and 18S rDNA (Hamby and Zimmer, 1988). The Grass Phylogeny Working Group (GPWG, 2001) combined the data from these sources to produce a phylogeny of the family (Kellogg, 2001). They recognized 12 subfamilies: Anomochloideae, Pharoideae, Puelioideae, Bambusoideae* 1 , Ehrhartoideae*, Pooideae*, Aristidoideae*, Arundinoideae*, Danthonioideae*, Centothecoideae, Panicoideae*, and Chloridoideae*. Three early diverging lineages (Anomochloideae, Pharoideae and Puelioideae) and two major lineages were recognized: a clade comprising the subfamilies Bambusoideae, Ehrhartoideae and Pooideae, called the BEP clade, and the PACCAD clade, containing the subfamilies Panicoideae, Arundinoideae, Chloridoideae, Centothecoideae, Aristidoideae and Danthonioideae. Later, the resurrection of the subfamily Micrairoideae and the synonymization of Centothecoideae with Panicoideae changed the acronym of the PACCAD clade to PACMAD (Sánchez-Ken et al., 2007;Sánchez-Ken & Clark, 2010). The PACMAD clade comprises ca. 5000 species or about half of the diversity of the family. Subfamily Anomochlooideae is the earliest diverging lineage of Poaceae followed by Pharoideae and Puelioideae (GPWG, 2001). Anomochlooideae and Pharoideae were embedded in Bambusoideae as tribe Anomochloeae and tribe Phareae respectively, but later resurrected as subfamilies (Clark & Judziewicz, 1996). Anomochlooideae includes two genera (Anomochloa and Streptochaeta) from tropical America characterized by "spikelet equivalent" instead of true grass spikelets. Puelioideae includes two genera (Gaduella, Puelia), native to tropical Africa of perennial rhizomatous grasses of shaded forest understory (Clark et al., 2000). Anomochlooideae, Pharoideae and Puelioideae are absent in the Chilean grass flora. Subfamily Bambusoideae includes approximately 115 genera (GPWG, 2001) of herbaceous (Tribe Olyreae, ca. 110 spp.) and woody bamboos (Bambuseae, ca. 1300 spp.). The world most diverse genus of bamboos is Chusquea, with 134 described species. Bambusoideae are perennial (rarely annual) usually woody grasses, with pseudopetiolated leaves. Culms are erect or scandent. Anatomically, they are characterized by the presence of fusoid cells, aligned perpendicular to the long axis of the leaf blade. Fusoid cells are large, thin walled and lack chloroplasts and other cell contents; they probably represent internal gas spaces. C3 photosynthesis takes place in the arm cells; these are thin walled cells with well developed invaginations or arm like lobes (Judziewicz et al., 1999; for a detailed leaf anatomical description of Chilean bamboos species see also Matthei, 1997). Subfamily Ehrhartoideae includes three tribes (Oryzeae, Ehrharteae and Phyllorachidae) and approximately 120 species (Barkworth et al., 2007), characterized by spikelets with one fertile floret often with one or two proximal sterile florets, two lodicules, three or six stamens, C3 photosynthesis, with a double bundle sheath around the veins, the outer sheath parenchymatous and the inner with thick walls (Kellogg, 2009). Subfamily Pooideae is the largest of the 13 subfamilies of Poaceae (GPWG, 2001), comprising about 3560 species . It includes some of the most economically important species, such as wheat (Triticum aestivum), oats (Avena sativa), barley (Hordeum vulgare) and rye (Secale cereale) and many forage and weed species. Plants herbaceous, with hollow culms (rarely solid); leaves distichous with an adaxial membranous ligule, rarely a fringe of hairs; leaf blades narrow; sheaths with or without auricles. Spikelets usually disarticulating above the glumes, laterally compressed. Glumes 2, lemmas 1 to many. Caryopsis with a linear or punctiform hilum. Endosperm solid, soft or liquid, with compounds starch grains (except in Bromeae, Triticeae, and Brachyelytreae). Embryo small, epiblast present, scutellar cleft absent, mesocotyl internode absent, embryonic leaf margins not overlapping. Photosynthetic pathway: C3. Basic chromosome number x = 7. Microhairs absent. Stomata with parallel-sided subsidiary cells. Pooideae includes some 3300 species distributed in temperate climates and in the tropics in the mountains. Most of the Chilean grasses belong to this subfamily. Subfamily Aristidoideae includes three genera (Aristida L., Stipagrostis Nees and Sartidia de Winter) and more than 350 species in tropical, subtropical and temperate zones, most belonging to Aristida. Aristidoideae are members of the PACMAD clade, with C4 or C3 photosynthesis (Cerros-Tlatilpa & Columbus, 2009). Plants are annuals or perennial. The www.intechopen.com abaxial ligule is absent or present; the adaxial ligule membranous or a fringe of hairs. The leaf sheath is non-auriculate. The inflorescence is a panicle. Spikelets with two glumes; lemmas three-awned; lodicules 2, rarely absent. Caryopsis with short or long-linear hilum. Endosperm hard, containing compound starch grains. Embryo small or sometimes large; epiblast absent; scutellar cleft present or absent; mesocotyl internode elongated; embryonic leaf margins not overlapping. Members of Aristidoideae have C4 photosynthesis (except Sartidia with non-Kranz anatomy and C3 photosynthesis). Basic chromosome number x = 11, 12. Bicellular microhairs present. Stomata with dome-shaped or triangular subsidiary cells. With only one genus (Aristida) and three species, this subfamily is underrepresented among Chilean grasses. Subfamily Arundinoideae includes 33-38 species of temperate and tropical zones (GPWG, 2001). Arundinoideae are perennial (rarely annual), herbaceous or sometimes woody plants, of temperate and tropical zones. Culms usually hollow; leaves distichous usually with adaxial ligule only; ligule membranous or a fringe of hairs; sheath non-auriculate. Inflorescence usually a panicle. Spikelets disarticulating above the glumes; glumes 2; lemma sterile sometimes present; 1 or more female-fertile florets. Lodicules 2. Caryopsis with hilum short or long-linear; endosperm solid, with compound starch grains. Embryo large or small; epiblast absent; scutellar cleft present; mesocotyl internode elongated; embryonic leaf margins meeting or overlapping. Basic chromosome number x = 6, 9, 12. Photosynthetic pathway: C3. Stomata with dome or triangular subsidiary cells. Bicellular microhairs present (sometimes absent). Subfamily Danthonioideae comprises some 250 species (GPWG, 2001). Plants usually perennial, rarely annual, usually herbaceous with rhizomes, stolons or caespitoses and culms most often solid. Leaves with adaxial ligule; ligule membranous or a fringe of hairs. Inflorescence a panicle. Spikelets laterally compressed, with two glumes and one to several fertile florets; rachilla disarticulating above the glumes and between the florets; lodicules two. Caryopsis with short or long-linear hilum; endosperm hard with compound starch grains; embryo large or small, with epiblast, with scutellar cleft, mesocotyl internode elongated and embryonic leaf margins meeting, rarely overlapping. Basic chromosome numbers x = 6, 7, 9. Photosynthetic pathway: C3. Stomata with dome shaped or parallelsided subsidiary cells. Bicellular microhairs present. Subfamily Chloridoideae comprises approximately 140 genera and more than 1420 species of arid environments (Hilu & Alice, 2001;Peterson et al., 2010). Plants annual or perennial with hollow or solid culms. Leaves distichous, with adaxial membranous ligule. Inflorescences paniculate. Spikelets with two glumes, laterally compressed or sometimes dorsally compressed; rachilla disarticulating above the glumes. Lemmas 1 to many; lodicules 2 (or absent), non-membranous (fleshy). Caryopsis with the pericarp often free or loose; endosperm solid, with simple or compound starch grains; embryo large, with epiblast, with scutellar cleft, mesocotyl internode elongated and embryonic leaf margins meeting, rarely overlapping. Stomata with dome-shaped or triangular subsidiary cells; bicellular microhairs or chloridoid type (inflated, spherical microhairs). Photosynthesis C4 of two main types: NAD-ME (nicotinamide adenine dinucleotide co-factor malic enzyme) and PCK (phosphoenolpyruvate carboxykinase). Basic chromosome numbers x = 9, 10, rarely 7 or 8 (GPWG, 2001). Stomata with dome-shaped or triangular subsidiary cells. Bicellular microhairs present. Subfamily Panicoideae comprises approximately 206 genera and 3300 species, mainly from tropical and warm temperate climates (Giussani et al. 2001;GPWG, 2001). Plants annual or www.intechopen.com perennial usually with solid culms. Leaves distichous with adaxial membranous ligule, sometimes a fringe of hairs or absent. Inflorescences panicle, racemes or compound inflorescences. Spikelets 2-flowered, with the lower floret staminate or barren, single or paired, dorsally compressed, with two glumes, disarticulating below the glumes (rarely above the glumes). Lodicules 2, fleshy. Caryopsis with short hilum, hard endosperm containing simple (rarely compound) starch grains; embryo large, epiblast absent, scutellar cleft present, mesocotyl internode elongated, embryonic leaf margins overlapping. Stomata with triangular or dome-shaped subsidiary cells; bicellular microhairs of the panicoid type present. Photosynthetic pathway C3, C4 and C3/C4 intermediates (GPWG, 2001). The presence of bifloral spikelets with the lower flower staminate or neuter, simple starch grains and molecular data, both from chloroplast and nuclear DNA, are synapomorphies that support the monophyly of the Panicoideae (Aliscioni et al., 2003).

Some geographical features of the Chilean territory
Details of the geographical and evolutionary characteristics of the Chilean flora have been published elsewhere (Arroyo et al., 1993;Grau, 1995, Squeo et al., 2008Stuessy & Taylor, 1995). Chile stretches from north to south for nearly 4270 km (ca. 39 degrees) along the western coast of South America, between 17°30'S (10 km North of Visviri) and 56°30´S (Diego Ramírez islands) and extends to the Antarctica at the South Pole (Chilean Antarctic Territory). Also belong to Chile the oceanic islands San Félix and San Ambrosio (Desventuradas islands), the archipelago of Juan Fernández and the Polynesian islands Easter Island and Sala and Gómez. Including the Chilean Antarctic Territory, the country's length spans for about 73 degrees. The maximum width occurs in southern Chile (52º21'S), where there is over 400 km between the Pacific Ocean and the Andes, but the overall width of the country usually does not exceed 200 km. Chile borders with Peru on the North, on the East with Argentina and Bolivia, on the West with the Pacific Ocean and on the South with the South Pole. In the north, Chile shares with Bolivia, Peru and Argentina the Altiplano, a plateau which does not descend from 4000 m of altitude. The Andes runs end-to-end the territory, establishing the border with Argentina. The Andes reaches heights of almost 7000 m in the northern zone, while to the south it falls below 2500 m. The Atacama Desert, considered to be one of the driest places in the world, dominates the climate on the north (Pankhurst & Hervé, 2007), with rainfall below 10 mm per year. From the Aconcagua valley to the region of Bío-Bío (approx. 32-38°S), the Mediterranean climate is dominant, with the exception of the high peaks of the Andes with cold weather due to the altitude. The Mediterranean region of Chile is included in the Chilean hotspot of biodiversity (Winter Rainfall Area of Central-Northern Chile Hotspot or Chilean Winter Rainfall and Valdivian Forests). The Chilean hotspot is located between 25 and 40°S , including the regions of Coquimbo and Atacama and extending to the region of Los Lagos in southern Chile. This hotspot contains 3892 vascular plant species, of which 1957 (more than 50%), are endemic to Chile. The Chilean hotspot covers almost 400.000 km 2 including the islands San Félix, San Ambrosio and the archipelago of Juan Fernández (Conservation International, 2011). South of 38°S the mixed deciduous-evergreen temperate forests occur. The biogeographic sketch of the Chilean vegetation (Cabrera & Willink, 1973) divided the territory into two phytogeographical regions (Región Neotropical and Región Antárctica) and domains (Dominio Patagónico and Dominio Subantárctico). A detailed account of the Chilean vegetation can be found in (Gajardo, 1994). To the Patagonian domain belong the Provinces Provincia Altoandina, Provincia Puneña, Provincia del Desierto, Provincia Chilena Central and Provincia Patagónica (Cabrera & Willink, 1973). Provincia Altoandina extends from Venezuela to Tierra del Fuego, in the high Andes. In the Andes of Mendoza (Argentina) and adjacent regions of Chile of Provincia Altoandina dominate communities of Festuca, Poa, Deyeuxia and Nasella. Provincia Puneña extends from 15-27°S, in the high Andes between 3200 and 4000 m of altitude. Communities of Pappostipa chrysophylla (coirón amargo) are common in this area. Provincia del Desierto is located on the Pacific coast between 5 and 30°S. This province has a warm, dry weather because of the Humboldt Current. The coastal fogs known as "camanchacas" allow the growth of vegetation mainly with species of the family Nolanaceae (Alona, Nolana). This province (also known as Subregión del desierto costero) is very interesting from a floristic point of view due to the high number of endemic species that live there (Gajardo, 1994). South of La Serena (Region of Coquimbo), the coastal fogs provide sufficient moisture to sustain the forest of Fray Jorge, a relict forest of Aextoxicon punctatum (olivillo, Aextoxicaceae), which only reappears only in southern Chile (Valdivia  (Luebert & Pliscoff, 2006). Other species frequently found are Festuca argentina, Jarava neaei, Deschampsia antarctica, D. elongata (Pisano, 1985). Región Antárctica and Dominio Subantárctico include two provinces: Provincia Subantárctica and Provincia de Juan Fernández. The archipelago of Juan Fernández, situated 670 km west of continental Chile in the Pacific Ocean, comprises three islands of volcanic origin: Masafuera or Alejandro Selkirk (33°37'S, 80°46'W), Masatierra or Robinson Crusoe (33°37'S, 78°50'W), and Santa Clara. Masafuera is located 180 km west of Masatierra whereas the small island Santa Clara is located 1 km SW of Masatierra (Errázuriz et al., 1998;Swenson et al. 1997). The archipelago of Juan Fernández is characterized by a high level of endemism; 31% of the vascular plants are endemic (Baeza et al., 2007;Swenson et al. 1997). The vascular flora of the islands comprises 42 families of flowering plants, including the monotypic and endemic Lactoridaceae. According to Skottsberg, the largest families are Asteraceae, Cyperaceae and Poaceae (Skottsberg, 1956). On the other hand, the high number of alien plants is a serious threat to the native flora of Juan Fernández (Matthei et al., 1993;Swenson et al., 1997).

Analysis of the Chilean grass diversity
To analyze the diversity of the family Poaceae in Chile, a database was prepared based on the collections of the herbaria of University of Concepción (CONC), National Museum of Natural History (SGO) and specimens cited in Tropicos database (tropicos.org), and taxonomic literature [Acevedo de Vargas (1959, Cortaderia Stapf); Baeza (1996, Danthonia DC., Rytidosperma Steud.); Cialdella & Arriaga (1998, Piptochaetium J. Presl); Cialdella & Giussani (2002, Piptochaetium); De Paula (1975, Anthoxanthum L. under Hierochlöe R.Br.); Finot et al. (2005, Trisetum Pers.); Matthei (1965, Nassella (Trin.) E. Desv. under Stipa L.;1975, Briza L.;1982, Festuca;1986, Bromus L.;1987ª, Aristida L., 1987b; Panicum L.); Muñoz-Schick (1985, Melica L.;1990, Nassella); Nicora (1998, Eragrostis Wolf); Rúgolo de Agrasar 1982, Bromidium Nees et Meyen; ;Soreng & Peterson (2008, Poa)]. A total of 13.924 records were included in the database, including the name of the species, subfamily, tribe, subtribe, geographical origin (native, introduced, endemic), collector, latitude, longitude, altitude, locality, date of collection, herbarium, and herbarium number. A checklist of the species based in the database, the Catalogue of the New World Grasses (Judziewicz et al., 2000;Peterson et al., 2001;Soreng et al., 2003;Zuloaga et al., 2003, available online at http://www.Tropicos.org) and the Catálogo de las plantas vasculares del Cono Sur (Zuloaga et al., 2008, available online at http://www2.darwin.edu.ar) was prepared. Recent taxonomic treatments of Chloridoideae (Peterson et al., 2007;Peterson et al., 2010), Danthonioideae (Linder et al., 2010), Panicoideae (Sánchez-Ken & Clark, 2010), Avenella, Deschampsia, Vahlodea (Chiapella & Zuloaga, 2010), Bromus (Planchuelo, 2010), Cenchrus (Chemisquy et al., 2010), Deyeuxia (Rúgolo de Agrasar, 2006), Digitaria (Vega et al., 2009) and Trisetum (Finot, 2010), were followed to update the nomenclature and the classification of the species. Lists of the species of the family Poaceae growing in Chile have been published for different regions (Arroyo et al., 1989(Arroyo et al., , 1990(Arroyo et al., , 1992Baeza et al., 1999Baeza et al., , 2002Baeza et al., , 2007Finot et al., 2009;Kunkel, 1968;Matthei et al., 1993;Reiche, 1903;Rodríguez et al., 2008aRodríguez et al., , 2008bRundel et al., 1996) or for all the country (Muñoz, 1941;Marticorena & Quezada, 1985;Zuloaga et al., 2008). Many species of Chilean grasses were collected and described early in the nineteenth century. The collection of grass specimens began at a fairly early stage of the knowledge of the diversity of the Chilean flora, in the early nineteenth century, with the collections made by Eduard Poeppig, Carlo Bertero, Rodulfo Amando and Federico Philippi, and Claudio Gay. In this period, Emile Desvaux published one of the first complete treatments of the Chilean grasses in Gay's "Historia Física y Política de Chile" (Desvaux, 1854), including 22 beautiful illustrations of native and endemic Chilean grasses, in Gay's Atlas. In the early twentieth century, new collections were made by Karl Reiche, Félix Jaffuel, Víctor Baeza, Franz Neger, Ernesto Barros, Atanasio Hollermayer, Hugo Gunckel, Erich Werdermann, Karl Junge, and Gilberto Montero, among others. Nonetheless, the number of specimens and, as a result, the number of species collected in the first 10 decades (1828-1917) is quite small (Fig. 2). In the early twentieth century only about 20% of the currently known grass flora had been collected. Since 1918 the collection effort was significantly increased; among 544 and 2063 specimens per decade were collected. These new collections allowed recording more than 430 new species. In order to compare the collection effort in the fifteen political regions in which the country is divided (Table 1), we calculated the collection index (Squeo et al., 1998):   The collection index takes values ranging from 1 to near zero. Value 1 indicates poor collection effort while values near to 0 indicate that the region is over-collected (Squeo et al., 1998 Fig. 5). The species accumulation curves allow the estimation of species richness from a sample and to compare the species richness of different areas. The accumulation curve for the country together with the curves of the five species richness estimators are shown in Fig. 3. The accumulation curve for the all country tends to be asymptotic (Fig. 3) and the mean number of estimated taxa (  Chilean grasses is good enough. On the other hand, the species accumulation curves at regional level (Fig. 4) show the number of taxa collected as a function of sampling effort (time) for each political region. Figure 4 show that the regions with lower richness are Tarapacá (TA), O'Higgins (OH), Atacama (AT) and Aysén (AY), while those with higher species richness are Bío-Bío (BB), Metropolitan (ME), Araucanía (AR) and Valparaíso (VA). According to Table 1, only 55% of the expected taxa for the region of O´Higgins are represented in the botanical collections. The species richness of Poaceae along the country is shown in Fig. 5. The regions located in northern Chile, Arica and Parinacota (AP), Tarapacá (TA), and Antofagasta (AN), known collectively as "Norte Grande" (Far North), and the regions of Atacama and Coquimbo, known as "Norte Chico" (Near North), are characterized by its desert climate because of the presence of the Atacama Desert. In the Far North, the diversity of grasses reaches relatively low values when compared with the regions of central and southern Chile. In Arica and Parinacota, there are 109 taxa (68% non-endemic native, 5.94% endemic, and 15.84% introduced), belonging to six subfamilies (Bambusoideae and Ehrhartoideae are absent in northern Chile), and 42 genera. The taxonomic biodiversity is higher than in the other regions of the Far North. Six endemic species were detected in Arica and Parinacota: Anatherostipa venusta, Bromus gunckelii, Cynodon nitidus, Festuca panda, Nassella pungens, and Trisetum johnstonii subsp. mattheii, the latter species is an endemic at regional level.
In Tarapacá there were 73 taxa in six subfamilies and 36 genera; however, the collection effort is lower than in the adjacent regions; four species endemic to Chile were present in this region: Anatherostipa venusta, Bromus gunckelii, Cynodon nitidus, and Polypogon linearis Trin. In Antofagasta there were 125 taxa, and a greater collection effort (Table 1); in comparison with the other two regions of "Norte Grande", in Antofagasta reside a greater number of endemic species: Anatherostipa venusta, Festuca morenensis, F. tunicata, F. werdermannii, Jarava matthei, J. tortuosa, Nassella pungens, Poa paposana, and Polypogon linearis. In the near north, we found two regions: Atacama (AT) and Coquimbo (CO), located between the hyper-arid region of Antofagasta and the more fertile region of Central Chile, between the rivers Copiapó and Aconcagua. In Atacama, only 106 taxa were recognized, of which 58 are native or endemic, while other six species were included in the Catalogue of the vascular flora of Atacama (Squeo et al. 2008). Nevertheless, the collection index shows a relatively small collection effort for grasses in Atacama (Table 1). Endemic species in Atacama are Festuca werdermannii, Jarava tortuosa, Nassella duriuscula, N. pungens, and Poa paposana. In Coquimbo there is an increase of the taxonomic biodiversity, coupled with an increased collection effort. The number of taxa reaches 167, which corresponds to the highest for Poaceae in northern Chile. According to the Catalogue of the vascular flora of Coquimbo , the flora of this region (native and naturalized) includes 1727 species of which nearly 9% belong to Poaceae. An analysis of the biodiversity of Coquimbo  mentions 104 species of Poaceae, the second most diverse family after Asteraceae in Coquimbo. An increase in the number of endemic grasses also takes place (Table 1). There are 26 endemic grasses belonging to 12 genera. The high degree of endemic species of Poaceae coincides with the high degree of endemism present in this region (53.5% of the vascular flora is endemic to Chile) . The subfamily Bambusoideae has its septentrional limit of distribution in the region of Coquimbo. In Fray Jorge, there are 11 species of Poaceae, including Chusquea cumingii (Arancio et al., 2004), which represents the northernmost record of subfamily Bambusoideae in Chile. Central Chile includes the regions of Valparaíso, Metropolitana, O'Higgins, Maule and Bío-Bío, approximately between 32° and 36°S. The high degree of anthropic pressure in central Chile is reflected in the greatest number of introduced species (approx. 10-16% of grasses are adventives). Due to the high percentage of endemic species, the high percentage of introduced species is disquieting as most of them are invasive weeds (Matthei, 1995). As has been pointed out, invasive species play a major role in displacing native plants and are the second leading threat to biodiversity following habitat destruction (Holcombe et al., 2010). It has been suggested that approximately 690 species of alien plants have been introduced and became naturalized in Chile, 507 of which reside in the Mediterranean area of central Chile; Poaceae is the most important family, with 151 species (Arroyo et al., 2000). Easter Island (Isla de Pascua, Rapa Nui) belongs to the Region of Valparaíso in central Chile (27°9'S, 109°27'W) and lies 3700 km off the Chilean coast. The island has a small amount of vegetation. Currently, there are 22 genera and about 200 species of seed plants, most of them introduced (Mann et al., 2003). Introduced grasses (Poaceae) dominate the vegetation while native species number about forty-six. Only eight endemic species remain. All trees are introduced species. The endemic tree Sophora toromiro Skottsb. (Fabaceae) disappeared in the 1950's, probably due to animal grazing and anthropogenic impact. A major effort to reintroduce this species on the island has been done by CONAF (Corporación Nacional Forestal) and Jardín Botánico Nacional of Chile.  (Giraldo-Cañas, 2008;Mann et al., 2003;Markgraf, 2003;Matthei, 1995;Skottsberg, 1956;Steadman, 1995). In the archipelago of Juan Fernández (Region of Valparaíso), Poaceae is represented by approximately 35 genera and 61 species. Most of the species belong to the subfamily Pooideae (44 spp., 72%) and Panicoideae (9 spp., 14%). Only two Bambusoideae are found, Chusquea fernandeziana, endemic to Masatierra, and C. culeou (Baeza et al., 2007), one cultivated species of the subfamily Arundinoideae (Arundo donax), two species of Danthonioideae (Danthonia chilensis and D. malacantha), and two species of Chloridoideae (Cynodon dactylon and Eleusine tristachya). Five species are endemic: Agrostis masafuerana Pilg. (Masafuera), Chusquea fernandeziana (Masatierra), Megalachne berteroana and M. masafuerana (Masatierra and Masafuera), and Podophorus bromoides possibly extinct (Baeza et al, 2002;Baeza et al., 2007). Polypogon imberbis is considered endemic to Juan Fernández, but occasionally found in continental Chile (Müller, 1985). Megalachne and Podophorus are endemic genera. The regions with greater diversity of Poaceae in Central Chile were Bío-Bío, Metropolitan, and Valparaíso, with 263, 198, and 186 taxa, respectively. According to our data, 57 species of grasses from 21 genera of grasses endemic to Chile are found in the area of the Chilean hotspot. On the other hand, O'Higgins is the most weakly collected region in Central Chile. Our data show that only 55% of the estimated grass flora in this region is represented in the Herbarium collections. Southern Chile includes the regions of Araucanía, Los Ríos and Los Lagos, from approx.   Table 1 for abbreviations of the regional names.

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Austral Chile, also known as Chilean Patagonia, includes the regions of Aysén and Magallanes and extends from about 43°S to the south. While Aysén has been weekly collected, Magallanes is one of the best known from a floristic point of view (Fig. 5). In Aysén 112 grass species have been collected (Table 1), including 77 native species, 19 introduced species and 4 endemic species (Anthoxanthum altissimum, Chusquea montana, C. quila, and C. uliginosa). In Magallanes 158 species have been collected (Table 1). Endemic species in this region are Alopecurus heleochloides, Festuca magensiana, Hordeum brachyatherum. Introduced species number 38 and native species number 117.

Subfamily
Tribes Subtribes Genera Species Infraspecific taxa The arrangement of the genera of Poaceae according to the classification of ) is shown in Table 3. Under each subfamily each species is mentioned. Introduced species are indicated with and asterisk (*), and endemic species are bold faced.

BEP clade
The three subfamilies of the BEP clade grow in Chile (Bambusoideae, Ehrhartoideae, Pooideae) but only two (Bambusoideae and Pooideae) include native species. The BEP clade comprises the majority of the Chilean grasses (ca. 450 spp, ca. 80%).

Bambusoideae
Bambusoideae are represented in Chile only by the genus Chusquea (Bambuseae, Chusqueinae). This diverse genus comprises some 134 described species; notwithstanding, some 70 species remain undescribed (Judziewicz et al. 1999). The genus Chusquea is exclusively American, growing from Mexico to Chile and Argentina, from approximately 24°N to 47°S and from see level to approximately 4000 m of altitude. Ten species and one variety grow in Chile, seven species are endemic (Tables 2 and 3). In Chile, the species of Chusquea are usually associated to forest margins, from approx. 30°S (Coquimbo) to 46°40'S (Aysén), and from the see level to 2300 m in the Andes. The most widely distributed species in Chile is C. culeou (coligüe), living from Choapa (31 ° S) to Aysén (45 °S) between the see level to ca. 2000 m of altitude; this species lives also in Argentina. Common to Chile and Argentina are also C. andina, C. montana f. montana (tihuén) and C. valdiviensis (quila del sur). Although C. quila (quila) is considered endemic to Chile, some botanists considered it a synonym of C. valdiviensis (Nicora, 1978;Parodi, 1945). Even though C. quila has been collected between Valparaíso (33°S) and Aysén (44°S) (Baeza et al., 2002). When Munro describes C. ligulata from Cundinamarca (Colombia), he includes under this name a sterile specimen collected by Bertero in Juan Fernández that possibly corresponds to C. fernandeziana (Parodi, 1945). This is, probably, the reason why C. ligulata is included sometimes as a synonym of C. fernandeziana. However, C. ligulata is closer to or conespecific with C. sneidernii Asplund of section Longiprophyllae, not to C. fernandeziana (Clark, 1990). Chusquea cumingii grows between Limarí (Region of Coquimbo, 30 °S) and Ñuble (36 °S), usually below 1500 m of altitude. Chusquea macrostachya has been collected between Santiago and Chiloé (33-43°S) but it is found more frequently in the southern regions of the country into the forest under the canopy or in canopy gaps as well as in roadsides. Chusquea uliginosa (quila de los ñadis), is found from Valdivia to Aysén (39-44°S), below 1500 m of altitude, in the central valley. The species of Chusquea are known in Chile by the vernacular names "coligües" or "quilas". Indigenous people ("mapuches") used the culms of C. culeou (coligüe) to build partitions inside their houses ("rucas"), musical instruments ("trutrucas") or fences, and used quilas (C. quila, C. cumingii), as forage for livestock. Currently, craftsmen use coligües to build furniture. Although coligües are not widely used in the industry, some properties like specific gravity, fiber length and chemical constitution suggest that this plant could be used as raw material for paper and for particle or fiber board production (Poblete et al., 2009).

Ehrhartoideae link
In Chile, Ehrhartoideae are absent from the native grass flora, but both the cultivated (rice) and wild rice (red rice, Oryza sativa) are found. Approximately 25,000 ha of rice are grown in a small south-central area of the country, located between O'Higgins (34°S) and Bío-Bío (36°S), which is the southernmost region of the rice crop in the world. In the same area, wild red rice is found, one of the most problematic weed of rice production in temperate countries (Gealy et al., 2003). Ehrharta calycina is native to southern Africa (Barkworth et al., 2007); it has been collected in pastures in Elqui and cultivated in Rinconada de Maipú Experimental Station of University of Chile, Metropolitan Region.

Pooideae benth
In Chile, Pooideae encompasses six tribes and 18 subtribes with nearly 396 species in 76 genera (Table 1) (Table 3). Glyceria is represented only by the Eurasiatic G. fluitans (L.) R. Br., and a native species G. multiflora Steud., inhabiting from Chacabuco (33°S) to Última Esperanza (50°S). Melica comprises eight species (including M. cepacea sometimes classified in the genus Bromelica), seven endemic. Genus Melica is distributed mainly in central-southern Chile, between 27°50'S and 40°15'S, and from sea level to 2000 m of altitude (Muñoz-Schick, 1985). Three species are considered vulnerable: M. longiflora, M. paulsenii, and M. poecilantha . Tribe Stipeae includes 21 genera and more than 500 species of which 279 live in the New World in temperate regions in both hemispheres, growing mainly in dry open grasslands and steppe communities. Most species of the New World Stipeae (approx. 80%) are South American (Romaschenko et al., 2008). Tribe Stipeae includes nine genera in Chile. Amelichloa Arriaga & Barkworth was described recently on the basis of five species segregated from genus Stipa, three of which grow in central-southern Chile (Arriaga & Barkworth, 2006). Anatherostipa (Hack. ex Kuntze) Peñailillo, was segregated from Stipa (Peñailillo, 1996), to include 11 species, four of which grow in Chile, restricted to the Andes of the northern regions (17-25°S) from 3400 to 4600 m of altitude. The South American genus Jarava Ruiz & Pav., includes 13 species widely distributed in Chile, mainly from the Andes and Patagonia, between 18°S and 50°S. Nassella, being the largest genus of the tribe Stipeae in Chile, encompasses about 30 species, 10 of which are endemic. The genus Nassella ranges, approximately, between 17°S and 43°S. Two species of genus Ortachne, O. breviseta and O. rariflora inhabit the subantartic forests.
Ortachne breviseta grows between Valdivia and Llanquihue (39-41°S) and O. rariflora between Chiloé and Tierra del Fuego (42-55°S), and from see level to 1700 m of altitude. The genus Pappostipa includes six species in Chile distributed between Arica (18°S) and Magallanes (53°S). Pappostipa chrysophylla, P. ibari and P. humilis are restricted to or have its main distribution in southern Chile. On the contrary, P. atacamensis and P. frigida are distributed primarily in northern Chile. Pappostipa speciosa is widely distributed in Chile and it is found also in the northern hemisphere.  (Mösbach, 1999).

Arundinoideae Burmeist
Arundinoideae comprises two species, Arundo donax and Phragmites australis; both species are tall reeds of wet places. Phragmites australis is a weed of rice fields (Matthei, 1995); A. donax is sometimes cultivated as ornamental.

Panicoideae Link
Panicoideae consists of two tribes, 10 subtribes, 18 genera and about 50 species in Chile (Table 2) halepense is a serious agricultural weed from Arica and Parinacota to the region of Araucanía and Easter Island) (Matthei, 1995). Zea mays is cultivated (corn), but also commonly found in roadsides. Tribe Paniceae is represented by some 39 species in 11 genera, most of them have been mentioned as summer weed of agricultural fields in Chile. Genus Cenchrus contains seven species, from northern and central Chile, some of them reported as common weeds (C. incertus, C. clandestinus, C. myosuroides, C. chilensis, C. longisetus). In addition, all species of genus Digitaria in Chile have been reported as weeds in agricultural fields, however, the most important because of its geographical distribution is D. sanguinalis, living from Huasco (Atacama) to Valdivia (Los Rios) and Juan Fernández. Digitaria setigera and D. violascens are introduced weeds in Easter Island (Matthei, 1995). Eriochloa montevidensis has been reported only from Valle de Azapa (Arica) as a weed in agricultural and ruderal fields. Melinis repens was also reported as a weed species introduced in Easter Island (Matthei, 1995). Dichanthelium sabulorum occurs in central-southern Chile (Maule, Bío-Bío). Echinochloa includes three species (E. colona, E. crus-galli, and E. crus-pavonis), all of them important weeds of rice fields. Genus Panicum includes four or five species, two of them weeds of ruderal and agricultural places, P. capillare and P. dichotomiflorum. Ten species of Paspalum have been reported, most of them as summer weeds in corn, sugar beets, rice, and other crops (Matthei, 1995). Genus Setaria also includes several important weed species in Chile, growing in vineyards, sugar beet, orchards, etc: S. parviflora, S. pumila, S. verticillata, S. viridis.

Chloridoideae Kunth ex Beilschm
Subfamily Chloridoideae comprises 16 genera and 41 species. Most of the genera are represented in Chile by only 1, 2 or 3 species. The largest genus is Eragrostis, comprising 12 species and two varieties (Escobar et al., 2011). Chloridoideae are present in northern, central and Southern Chile but they are rare in Austral Chile. Bouteloua comprises only one Arica and Parinacota, in semi-desert slopes of the Andean foothills of Arica, above 2000 m of www.intechopen.com www.intechopen.com altitude (Matthei, 1973). Chloris comprises three species; all introduced (C. gayana, C. radiata and C. virgata). Chloris gayana is native from Africa (Senegal); in Chile it is found only in Easter Island (Anderson, 1974;Matthei, 1995). The other two species grow in Northern Chile. Cynodon nitidus is endemic to Chile. Cynodon dactylon is a common weed in ruderal places, both in continental Chile and Easter Island. Eleusine indica is found only in Easter Island. Eleusine tristachya is a common weed of gardens as well as orchards and meadows in Central Chile. Genus Eragrostis comprises 12 species, eight of them native and four introduced.   Eragrostis polytricha grows in Central Chile. Spartina densiflora (austral cordgrass), a species probably native from the east coast of South-America (Bortolus, 2006), has been reported as an invasive species in North America, Europe and Africa (Ayres et al., 2004); it grows in Chile in salt marshes, from Concepción (Bío-Bío) to Chiloé (Los Lagos) as the dominant species of the association Sarcocornio-Spartinetum densiflorae (San Martín et al., 2006). In the same habitats are usually found species of genus Distichlis; D. spicata, can also grow as a weed of orchards and ruderal places (Matthei, 1995).

Conclusions
The   Driven by the increasing necessity to define the biological diversity frame of widespread, endemic and threatened species, as well as by the stimulating chance to describe new species, the study of the evolutive and spatial dynamics is in constant execution. Systematic overviews, biogeographic and phylogenic backgrounds, species composition and distribution in restricted areas are focal topics of the 15 interesting independent chapters collected in this book, chosen to offer to the reader an overall view of the present condition in which our planet is.