**2. 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

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

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

growing on agricultural land are also members of the grass family.

more rarely, solid. Roots are fibrous and adventitious (homorriza).

pseudopetiole, a constriction at the base of the leaf blade

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

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

**2. Diversity, phylogeny and classification of the grass family** 

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 CO2 levels and high O2 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 (Mathews et al., 2000), 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,

<sup>1</sup> An asterisk indicates the subfamilies present in Chile.

Systematic Diversity of the Family Poaceae (Gramineae) in Chile 75

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

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

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 parallel-

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.

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

Chilean grasses.

present (sometimes absent).

Bicellular microhairs present.

sided subsidiary cells. Bicellular microhairs present.

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 (Soreng et al., 2007). 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

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

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

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

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

Subfamily **Pooideae** is the largest of the 13 subfamilies of Poaceae (GPWG, 2001), comprising about 3560 species (Soreng et al., 2007). 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

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

description of Chilean bamboos species see also Matthei, 1997).

parenchymatous and the inner with thick walls (Kellogg, 2009).

about half of the diversity of the family.

the Chilean grass flora.

grasses belong to this subfamily.

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

Systematic Diversity of the Family Poaceae (Gramineae) in Chile 77

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). *Provincia Chilena Central* extends between 32ºS and 38°S (except in the high mountains), including the regions of Valparaíso, Metropolitana, O'Higgins, Maule and Bío-Bío. This province is dominated by sclerophyllous forests with *Bielschmiedia miersii* (belloto, Lauraceae), *Peumus boldus* (boldo, Monimiaceae), *Cryptocarya alba* (peumo, Lauraceae), *Kageneckia oblonga* (huayu, Rosaceae), *Lithrea caustica* (litre, Anacardiaceae), *Quillaja saponaria* (quillay, Rosaceae), *Colliguaya dombeyana* (colliguay, Euphorbiaceae), etc. In the central valley known as Depresión Intermedia, the espinal of *Acacia caven* (espino, Mimosaceae) is the dominant vegetation community. The espinal has a very high diversity of Poaceae. Species commonly found in the prairie of the espinal are *Agrostis capillaris*, *Aira caryophyllea*, *Aristida pallens*, *Avena barbata*, *Briza maxima*, *B. minor*, *Bromus hordeaceus*, *B. rigidus*, *B. stamineus*, *Chascolytrum subaristatum*, *Chusquea quila*, *Cynosurus echinatus*, *Dactylis glomerata*, *Danthonia chilensis* var. *aureofulva*, *Hordeum chilense*, *H. murinum*, *Lolium multiflorum*, *L. perenne*, *Melica violacea*, *Nasella gibba*, *N. neesiana*, *N. pfisteri*, *Paspalum dasypleurum*, *Phalaris amethystina*, *Poa annua*, *Piptochaetium montevidense*, and *Vulpia bromoides*. In southern Chile, *Provincia Patagónica* comprises the regions of Aysén and Magallanes. This region is characterized by dry and cold climate with vegetation consisting mainly of grassland steppe (Fig. 1), where communities of *Festuca pallescens* and *F. gracillima* are important in Aysén and Magallanes, respectively (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).

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).
