Journal of Biogeography (1997) 24, 197–204

Distribution of C3 and C4 grasses along an altitudinal gradient in Central

M C∗,N A†, M E. A† and A M. A∗∗IMBIV, UNC-CONICET, CC 495, 5000 Co´rdoba, Argentina and †Facultad de Ciencias Agropecuarias, UNC. CC 509, 5000 Co´rdoba, Argentina

Abstract. The distribution pattern of C3 and C4 grasses nine climatic and environmental variables showed the was studied in eight sites located between 350 m and 2100 m highest correlation with July mean temperature, but all along an altitudinal gradient in Central Argentina. Of 139 temperature variables show highly significant correlations taxa fifty-nine are C3 and eighty C4. Species of the C3 tribes with % C4. Correlation with annual rainfall is lower but (Stipeae, Poeae, Meliceae, Aveneae, Bromeae and Triticeae) also significant. These results are consistent with previous and C3 Paniceae species increase in number at higher research showing the relative importance of C4 grasses as elevations; only one C3 species was found below 650 m. temperature increases. C3 species make a high contribution

C4 Aristideae, Pappophoreae, Eragrostideae, , to relative grass coverage below the C3/C4 floristic crossover Andropogoneae and Paniceae increase at lower altitudes. point but are rare below 1000 m. The floristic crossover point is at about 1500 m; the ground cover cross-over point is at about 1000 m. Analysis of the Key words. C3 and C4 grasses, altitudinal gradient, climate, relationships between % C4 species along the gradient and Argentina.

METHODS INTRODUCTION The distribution of C and C grasses were obtained for Physiological differences of C and C grass species are 3 4 3 4 eight sites along an altitudinal gradient ranging from 350 m reflected in their distribution patterns along environmental to around 2100 m a.s.l. in the Co´rdoba Mountains (31°60′S gradients or under varying climatic conditions. C grasses 4 and 65°50′W). Floristic surveys and Braun-Blanquet cover are generally represented more on warmer environments, abundance data (Braun-Blanquet 1932), provided by while C grasses are represented more on cooler 3 Cabido (1985), Cabido & Acosta (1986), Cabido, Breimer environments. These distribution patterns are remarkably & Vega (1987), Acosta et al. (1989) and Cabido et al. (1994), consistent at a large range of spatial scales (Wentworth, were used to assess the distribution of species. All the sites 1983), and in all parts of the world where they have been were open grasslands where grasses are the dominant species. investigated (Hattersley, 1992; Ehleringer & Monson, 1993). Only the two lower sites had scattered trees. The climate is Usually temperature is the variable mostly correlated with temperate with warm season rainfall (70% of the rain falls the occurrence of C species in grass floras (Teeri & Stowe, 4 from November to March). A detailed description of the 1976; Cavagnaro, 1988), even though some authors have area is given by the authors cited above. stressed the importance of water availability and soil Total number of C and C grass species, % C species moisture indices (Chazdon, 1978; Tieszen et al., 1979). 3 4 4 and%C and C grass cover were calculated for each According to Hattersley (1983) generally both C and C 3 4 3 4 elevational site. Cover values were obtained from Braun- grass species increase in number with increasing rainfall in Blanquet data. The C photosynthetic pathway was their preferred temperature regime. 4 identified by examination of Kranz anatomy in cross- The study reported here is one of the few examining the sections of fresh and herbarium specimens and from distribution of C and C grass species along an elevational 3 4 literature data (Smith & Epstein, 1971; Sa´nchez & Arriaga, gradient for grasslands in a temperate summer-rainfall 1990; Hattersley & Watson, 1992). region of the world (in Central Argentina). Our objective Pearson’s correlation coefficients were calculated for the was to identify those climatic variables most correlated with relationships between distribution parameters (% C4 and C4 grass species composition. numbers of C3 and C4 species) and climatic variables obtained from the National Meteorological Service (Servicio Meterorolo´gico Nacional 1958, 1962a, 1962b), from records of the Argentine Railways (unpublished data) and from ∗ Corresponding author: Marcelo Cabido, IMBIV, Casilla de Correo 495, stations located in private properties (Palacios & Zamar, 5000 Co´rdoba, Argentina. 1986) (Table 1).

 1997 Blackwell Science Ltd 197 198 Marcelo Cabido et al.

TABLE 1. Climatic parameters for the eight sites along an elevational gradient in Central Argentina. Altitude (m) 350 600 1000 1400 1600 1800 1900 2100

AAT 18.1 17.5 13.1 11.6 10.7 9.7 8.8 8.1 ANF 9.6 28.7 41.9 57.3 65.1 74.0 85.8 89.6 JANT 20.0 16.5 14.7 12.3 11.7 10.2 9.1 8.3 JAMT 34.5 30.6 27.5 23.6 22.1 20.0 18.0 15.8 JuANT 4.1 5.1 2.7 1.3 0.9 0.7 0.1 −2.0 JuAMT 18.8 17.3 15.1 13.0 11.8 10.3 8.3 8.8 JMT 27.2 24.0 22.1 17.9 16.6 15.4 12.1 13.3 JuMT 10.8 10.4 8.3 6.7 6.0 5.2 4.2 4.1 AR 680 750 786 887 858 873 840 891 SR 365 432 473 530 597 586 549 644

ALT=altitude; AAT=annual average temperature; AR=annual rainfall; SR=summer rainfall; ANF=average number of days with frost; JANT=January average minimum temperature; JAMT=January average maximum temperature; JuANT=July average minimum temperature; JuAMT=July average maximum temperature; JMT=January mean temperature; JuMT=July mean temperature.

FIG. 1. Frequency of occurrence of C3 and C4 grass species by tribe along an altitudinal gradient in Central Argentina. Light bars=C3 species; dark bars=C4 species.

 Blackwell Science Ltd 1997, Journal of Biogeography, 24, 197–204 Distribution of C3 and C4 grasses in Argentina 199

more prevalent at lower altitudes. Andropogoneae species are more common at intermediate sites (between 1000 m and 1400 m).

C3 and C4 grasses show a divergent distribution along the

gradient (Fig. 2). The number of C3 species decreases from thirty-seven at 2100 m to four at 600 m, and only one (Stipa

sanluisensis Speg.) at 350 m. C4 grasses are more numerous in the lower zone and less so above 1400 m (Table 2).

Nevertheless, nine C4 grasses are still found at 2100 m where the January average maximum temperature is only 15.8°C.

The floristic crossover point (equal numbers of C3 and C4 species) is at approximately 1500 m but the ground cover

cross-over point is at 1000 m (Fig. 2). Although C3 species decrease considerably below 1600 m, their contribution to total grass coverage is well over 50% from above 1000 m (Table 2). Remarkably high positive correlation was found between

both summer and winter temperature variables with % C4

species (Table 3). Correlation of % C4 with rainfall is nega- tive and also is significant. Correlations between the number

of C4 species and climatic variables are not significantly different (results are not presented).

DISCUSSION

There are clear differences in the distribution of C3 and C4 grasses along the altitudinal gradient studied. Lower altitude

grasslands consist mainly of C4 grasses, whereas C3 grasses dominate at higher altitudes. Our findings are comparable with those reported for different regions of the world (Hattersley, 1992; Hattersley & Watson, 1992; Ehleringer & Monson, 1993). All temperature variables tested showed strong

correlations with the relative abundance of C4 and C3 species, suggesting that the cooler the winter, the greater the relative

success of C3 grasses, and the hotter the summer the greater

the relative success of C4 grasses. An equally close

relationship was found between % C4 and January average maximum temperature for Australia (Hattersley, 1983). While temperature and related variables are highly

correlated with % C4 at continental scales (Hattersley, 1992), good correlations with rainfall are also reported along elevational gradients at more local scales, where precipitation increases with altitude (Chazdon, 1978; Rundel, 1980). In our study area rainfall also shows good

correlation with % C4 and when only summer rainfall is correlated the coefficient is even higher. Our finding contrasts

FIG. 2. Relative C3/C4 grass species composition (%) and coverage with that of Cavagnaro (1988) who reported non-significant (%) along an altitudinal gradient in Central Argentina. correlation with rainfall for a close but climatically different region in Argentina. The cross-over point for the number of species occurs at RESULTS 1500 m, and is characterized by a mean annual daily Of the 139 grass taxa found along the elevational gradient, minimum temperature of approximately 7°Cto8°C. The

fifty-nine were C3 and eighty C4. Only the tribe Paniceae cross-over point occurs at different elevations in other contains both C3 and C4 species. Most of the tribes show regions of the world but at similar mean minimum trends in their representation with increasing or decreasing temperature ranges (Tieszen et al., 1979; Rundel, 1980). altitude (Fig. 1). The C3 tribes Poeae, Aveneae, Bromeae and Several authors have found that mean minimum and mean

Arundineae and C3 Paniceae species are more represented maximum temperatures of the warmest month are the single at higher altitudes. In contrast, the C4 tribes Aristideae, best predictors of C3 and C4 species numbers (Wentworth,

Pappophoreae, Cynodonteae and C4 Paniceae species, are 1983). When our results are compared with those reported

 Blackwell Science Ltd 1997, Journal of Biogeography, 24, 197–204 200 Marcelo Cabido et al.

TABLE 2. Number of species, % species and % cover of C3 and C4 grasses for eight locations along an altitudinal gradient in Central Argentina. Altitude (m) 350 600 1000 1400 1600 1800 1900 2100

Number of C3 1 4 19 20 20 21 27 37 species

%C3 species 2.3 10.0 35.8 39.2 60.6 65.6 69.2 80.0

%C3 cover 0.03 0.04 51.8 65.4 63.3 63.0 71.4 72.1

Number of C4 43 36 34 31 13 11 12 9 species

%C4 species 97.7 90.0 64.2 60.8 38.2 34.4 30.8 20.0

%C4 cover 99.7 99.9 48.2 34.6 36.7 37.0 28.6 27.9

TABLE 3. Correlation of % C4 grass species composition and environmental distribution has also been stressed by Tieszen et al. (1979). variables. In our study area it seems to be related to at least the

Variables R local C4 species distribution at higher elevation where soil moisture data are available (Cabido et al., 1987). In

ALT −0.98∗∗ agreement with Teeri & Stowe (1976) C4 genera recognized AAT 0.97∗∗ as being particularly susceptible to low temperatures, such ANF −0.97∗∗ as Digitaria, Paspalum and Axonopus, were not found above AR −0.86∗ SR −0.95∗∗ 1900 m in our transect. JANT 0.96∗∗ The ground cover cross-over point found in this study is at JAMT 0.97∗∗ approximately 1000 m, considerably lower than the floristic

JuANT 0.94∗∗ cross-over altitude. The high cover of C3 grasses below the JuAMT 0.97∗∗ floristic cross-over point results from the dominance effect JMT 0.96∗∗ exerted in grassland communities by big tussock grasses JuMT 0.98∗∗ such as Stipa filiculmis Delile, S. tenuissima Trin. and Festuca R=correlation coefficient; ∗∗=significant hieronymi Hack. (Acosta et al., 1989). The mean maximum at P<0.01; ∗=significant at P<0.05. temperature of the warmest month at this elevation is about 27°C, which is similar to the value of 26°C reported by Wentworth (1983) for the cross-over point in Arizona, but for lower latitudes (Chazdon, 1978 for Costa Rica; Tieszen substantially higher than the corresponding value of 22°C et al., 1979 for Kenya; Rundel, 1980 for Hawaii), a pattern reported by Rundel (1980) for Hawaii. These results are for the cross-over point emerges only for the mean maximum consistent with the temperate versus tropical pattern of temperature of the warmest month, which ranges between floristic cross-over temperatures discussed above. Below 21°C and 22°C. However, when the mean minimum 1000 m the contribution of C3 species to total grass cover temperatures of the warmest month are compared for the is negligible. By contrast C4 grasses still attain nearly 30% cross-over point, our results are most comparable with of total grass cover at higher elevations as a result of the those reported for temperate latitudes (Wentworth, 1983 dominance of some species in locally rocky or xeric sites, for Arizona; Cavagnaro, 1988 for Argentina). This is in as mentioned before. The higher contribution of C3 grass agreement with what has been suggested by Rundel (1980), species to total grass coverage below the floristic cross- and supported by Ehleringer (1978) and Cavagnaro (1988), over point requires further explanation and research. Some that C4 grasses achieve floristic dominance at lower possibilities are that it could reflect inertia of past environmental temperatures in the tropics than in temperate communities widely distributed during the last glaciation, regions. or the importance of other environmental constraints, such Teeri & Stowe (1976) and Long (1983) suggested that as edaphic factors. locations with a minimum temperature of the warmest ACKNOWLEDGMENTS month below 8°C appear to have few or no C4 grass species.

However, Schwartz & Redmann (1988) reported that C4 This study was supported by the National University of genera such as Muhlenbergia commonly occur at or below Co´rdoba through the Secretary of Science and Technology this temperature limit. In our study area such temperatures (SECyT) and the Research Council of Co´rdoba Province are found at the highest extreme of the gradient where nine (CONICOR). Paul Hattersley made valuable improvements

C4 grass species are still found. They belong to the genera to a first draft of the manuscript. We are also indebted to Muhlenbergia, Aristida, Eragrostis, Tripogon, , Prof. D. Abal Solı´s who drew the figures.

Bothriochloa, Schizachyrium and Sorghastrum. The C4 species at this altitude are restricted to sandy shallow soils REFERENCES with low indices of available soil moisture and water deficit Acosta, A., Cabido, M., Dı´az, S. & Menghi, M. (1989) Local and at some time throughout the year (Cabido et al., 1987). The regional variability in granite grasslands in the mountains of importance of soil moisture in determining C3/C4 species Central Argentina. Ber. Geobot. Inst. ETH. 55, 39–50.

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Braun-Blanquet, J. (1932) Plant sociology, the study of plant photosynthesis. Grass evolution and domestication (ed. by G. communities, p. 438. New York, McGraw-Hill. Chapman), pp. 38–116. Cambridge, Cambridge University Press.

Cabido, M. (1985) Las comunidades vegetales de la Pampa de Long, S.P. (1983) C4 photosynthesis at low temperatures. Plant Cell Achala, Sierras de Co´rdoba, Argentina. Doc. Phytosociologiques, Environ. 6, 345–363. 9, 431–443. Palacios, A.A. & Zamar, J.L. (1986) Erosio´nhı´drica. Volu´men de Cabido, M. & Acosta, A. (1986) Contribucio´n al conocomiento Sı´ntesis: Proyecto Pacho´n-Achala. MaB 6-UNEP-UNESCO 1105- fitosociolo´gico del Sub-piso Superior de pastizales y bosquecillos 77-01 (ed. by R. Luti), pp. 244–310. Montevideo, ROSTLAC- de altura de las Sierras de Co´rdoba. Veroff. Geobot. Inst. ETH. UNESCO. 91, 118–140. Rundel, P. (1980) The ecological distribution of C4 and C3 grasses Cabido, M., Breimer, R. & Vega, G. (1987) Plant communities and in the Hawaiian Islands. Oecologia, 45, 354–359. associated soil types in a high plateau of the Co´rdoba Mountains, Sa´nchez, E. & Arriaga, M. (1990) El sı´ndrome de Kranz en Central Argentina. Mount. Res. Devel. 7, 25–42. de la flora Argentina. Parodiana, 6, 73–102. Cabido, M., Manzur, A., Carranza, L. & Gonza´lez Albarricı´n, C. Schwarz, A.G. & Redman, R.E. (1988) C4 grasses from the boreal (1994) La vegetacio´n y el medio fı´sico del Chaco Arido en la forest region on northwestern Canada. Can. J. Bot. 66, 2424–2430. provincia de Co´rdoba, Argentina Central. Phytocoenologia, 24, Servicio Meteorolo´gico Nacional, Repu´blica Argentina (1958) 423–460. Estadı´sticas climatolo´gicas 1901–1950. Buenos Aires, Publ. B1, Cavagnaro, J.B. (1988) Distribution of C and C grasses at different 3 4 No. 1. altitudes in a temperature arid region of Argentina. Oecologia, Servicio Meteorolo´gico Nacional, Repu´blica Argentina (1962a) 76, 273–277. Datos pluviome´tricos 1921–1950. Buenos Aires, Publ. B1, No. 2. Chazdon, R.L. (1978) Ecological aspects of the distribution of C 4 Servicio Meteorolo´gico Nacional, Repu´blica Argentina (1962b) grasses in selected habitats of Costa Rica. Biotropica, 10, 265–269. Estadı´sticas climatolo´gicas 1951–1960. Buenos Aires, Publ. B1, Ehleringer, J.R. (1978) Implications of quantum yield differences No. 6. on the distributions of C3 and C4 grasses. Oecologia, 31, 255–267. Smith, B. & Epstein, S. (1971) Two categories of 13C/12C ratios for Ehleringer, J.R. & Monson, R.K. (1993) Evolutionary and higher . Plant Physiol. 47, 380–384. ecological aspects of photosynthetic pathway variation. Ann. Rev. Teeri, J.A. & Stowe, L.G. (1976) Climatic patterns and the Ecol. Syst. 24, 411–439. distribution of C4 grasses in North America. Oecologia, 23, 1–12. Hattersley, P.W. (1983) The distribution of C3 and C4 grasses in Tieszen, L.L., Senyimba, M.M., Imbamba, S.K. & Troughton, J.H. Australia in relation to climate. Oecologia, 57, 113–128. (1979) The distribution of C3 and C4 grasses and carbon isotope Hattersley, P.W. (1992) C4 photosynthetic pathway variation in discrimination along an altitudinal and moisture gradient in grasses (Poaceae): its significance for arid and semi-arid lands. Kenya. Oecologia, 37, 337–350.

Desertified grasslands: their biology and management (ed. by G. Wentworth, T.R. (1983) Distributions of C4 plants along Chapman), pp. 181–212. London, Academic Press. environmental and compositional gradients in southeastern Hattersley, P.W. & Watson, L. (1992) Diversification of Arizona. Vegetatio, 52, 21–34.

APPENDIX 1

Presence (+) and absence (−)ofC3 and C4 grass species for eight sites along an altitudinal gradient in Central Argentina Altitude (m) 350 600 1000 1400 1600 1800 1900 2100

C3 species 1 Tribe Stipeae Stipa amethystina Steud. −−−+−−+− Stipa cordobensis Speg. −+−−−−−− Stipa eriostachya Kunth −++++−−+ Stipa filiculmis Delile −−+++++− Stipa hunzikeri Caro −−++−−−− Stipa juncoides Speg. −−−+−+++ Stipa neesiana var. longiaristata Arechav. −−−−−+−− Stipa neesiana Trin. & Rupr. var. neesiana −−+++−++ Stipa nidulans Mez −−−−−−++ Stipa niduloides Caro −−−−−−++ Stipa papposa Nees −−−−+−−− Stipa polyclada Hack. −+−−−−−− Stipa pseudopampagrandensis Caro −−−−−−−− Stipa sanluisensis Speg. ++−−−−−− Stipa stuckertii Hack. −−−−−−−+ Stipa tenuissima Trin. −−++++++ Stipa trichotoma Nees −−+++++− Piptochaetium medium (Speg.) Torres −−++−−−− Piptochaetium montevidense (Spreng.) Parodi −−++++++ Piptochaetium napostaense (Speg.) Hack. −−++−−−− Piptochaetium stipoides var. chaetophorum (Griseb.) Parodi −−+−+−−− 2 Tribe Poeae Briza paleapilifera Parodi −−+−+++− Briza rufa (J. Presl.) Steud. −−−−−−++ Briza subaristata Lam −−++++++

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APPENDIX 1 (contd)

Presence (+) and absence (−)ofC3 and C4 grass species for eight sites along an altitudinal gradient in Central Argentina Altitude (m) 350 600 1000 1400 1600 1800 1900 2100

Festuca circinata Griseb. −−−−−−−+ Festuca hieronymi Hack. −−++−+++ Festuca tucumanica E. B. Alexeev −−−−−+++ Lolium multiflorum Lam. −−+−+−+− Poa annua L. −−−−−−−+ Poa hubbardiana Parodi −−−+++−+ Poa resinulosa Steud. −−−−+−−+ Poa scaberula Hook. f. −−−−−−++ Poa stuckertii (Hack.) Parodi −−−−−+−+ Vulpia myurus var. hirsuta Hack. −−−+++++ Vulpia myurus var. megalura (Nutt.) Auquier −−−−−++− 3 Tribe Meliceae Melica macra Nees −−+−−−−− Melica stuckertii Hack. −−++−−−− 4 Tribe Aveneae Agrostis breviculmis Hitchc. −−−−−−−+ Agrostis glabra (J. Presl) Kunth var. glabra −−−−−−−+ Agrostis montevidensis Spreng. −−−+++++ Agrostis tolucensis Kunth −−−−−−−+ Aira caryophyllea L. −−−−−−−+ Chaetotropis elongata (Kunth) Bjo¨rkman −−−−−−++ Deyeuxia colorata Beetle −−−−−−−+ Deyeuxia eminens f. brevipila (Hack.) Tu¨rpe −−−−−−−+ Deyeuxia eminens J. Presl −−−−−−−+ Deyeuxia hieronymi (Hack.) Tu¨rpe −−−−−+++ Koeleria kurtzii Hack. −−−−−−−+ 5 Tribe Bromeae Bromus auleticus Nees −−++++++ Bromus brevis Steud. −−−−+−++ Bromus catharticus Vahl −−++++++ Bromus commutatus Schrad. −−−−−−−+ 6 Tribe Triticeae Hordeum stenostachys Godr. −−+−−−+− 7 Tribe Arundineae Cortaderia selloana (Schult. et Schult.f.) Asch. & Graebn. −−−−−−−+ Danthonia cirrata Hack. & Arechav. −−−−−+++ Danthonia montevidensis Hack. & Arechav. −−−−−−++ Lamprothyrsus hieronymi (Kuntze) Pilg. −−−−−+−− 8 Tribe Paniceae Panicum hians Elliott −−−+++−− Panicum sabulorum Lam. var. sabulorum −−−−+−−−

C4species 1 Tribe Aristideae Aristida achalensis Mez −−−+−−−− Aristida adscensionis var. modesta Hack. −++−−−−− Aristida adscensionis var. scabriflora Hack. ++−−−−−− Aristida circinalis Lindm. −−++−−−− Aristida flabellata var. flabellata Caro −+−−−−−− Aristida laevis (Nees) Kunth −−++−−−− Aristida mendocina Phil. ++−−−−−− Aristida pallens Cav. var. pallens −−++−−−− Aristida spegazzini Arechav. var. spegazzini −−++−+++ 2 Tribe Pappophoreae Cottea pappophoroides Kunth ++−−−−−− caespitosum R.E.Fr. ++−−−−−− Pappophorum pappiferum (Lam.) Kuntze ++−−−−−− Pappophorum philippianum Parodi ++−−−−−− Pappophorum vaginatum Buckley ++−−−−−− 3 Tribe Eragrostideae Diplachne dubia (Kunth) Scribn. ++−−−−−−

Blackwell Science Ltd 1997, Journal of Biogeography, 24, 197–204 Distribution of C3 and C4 grasses in Argentina 203

APPENDIX 1 (contd)

Presence (+) and absence (−)ofC3 and C4 grass species for eight sites along an altitudinal gradient in Central Argentina Altitude (m) 350 600 1000 1400 1600 1800 1900 2100

Eleusine tristachya (Lam.) Lam. −−+−+−−− Eragrostis cilianensis (All.) Janch. +++−−−−− Eragrostis lugens Nees var. lugens −+++++++ Eragrostis orthoclada Hack. ++−−−−−− Gouinia paraguayensis (Kuntze) Parodi ++−−−−−− Muhlenbergia ligularis (Hack.) Hitchc. −−−−−−++ Muhlenbergia peruviana (P. Beauv.) Steud. −−−+++++ Sporobolus indicus (L.) R. Br. −−+++++− Sporobolus phleoides Hack. +−−−−−−− Sporobolus pyramidatus (Lam.) Hitchc. ++−−−−−− Sporobolus rigens (Trin.) Desv. +−−−−−−− Tripogon spicatus (Nees) Ekman +−++−+++ 4 Tribe Cynodonteae Bouteloua aristidoides (Kunth) Griseb. ++−−−−−− Bouteloua curtipendula var. caespitosa Gould & Kapadia ++++−−−− Bouteloua megapotamica (Spreng.) Kuntze −−++−−+− Chloris virgata Sw. ++−−−−−+ Chondrosum simplex (Lag.) Kunth −−−−−−−− Cynodon dactylon (L.) Pers.var. dactylon +++−−−−− Cynodon hirsutus Stent var. hirsutus −−++++−− Eustachys distichophylla (Lag.) Nees ++−−−−−− Eustachys retusa (Lag.) Kunth −−+++−−− Gymnopogon spicatus (Spreng.) Kuntze −−++−−−− Microchloa indica (L.f.) P. Beauv. var. indica −−+++−−− Neobouteloua lophostachya (Griseb.) Gould ++−−−−−− Tragus berteronianus Schult. ++−−−−−− Trichloris crinita (Lag.) Parodi ++−−−−−− Trichloris pluriflora E. Foum. ++−−−−−− 5 Tribe Paniceae Axonopus fissifolius (Raddi) Kuhlm. −−++−−−− Cenchrus myosuroides Kunth var. myosuroides +−−−−−−− Cenchrus pauciflorus Benth. var. pauciflorus +−−−−−−− Digitaria aequiglumis (Hack. & Arechav.) Parodi var. −−−−−−+− aequiglumis Digitaria californica (Benth.) Henrard var. californica ++−−−−−− Digitaria ciliaris (Retz.) Koeler +−−−−−−− Digitaria insularis (L.) Fedde ++−−−−−− Digitaria sanguinalis (L.) Scop. +−−−−−−− Digitaria swalleniana Henrard +−−−−−−− Echinochloa colona (L.) Link +−−−−−−− Panicum bergii Arechav. var. bergii −+−−−−−− Paspalum dilatatum Poir. subsp. dilatatum −−++−−−− Paspalum humboldtianum Flu¨gge var. humboldtianum −−++−−−− Paspalum malacophyllum Trin. −−++−−−− Paspalum nicorae Parodi −−−−+−−− Paspalum notatum var. latiflorum Do¨ll −−+++−−− Paspalum plicatulum Michx. var. plicatulum −−++−−−− Paspalum quadrifarium Lam. −−+−−−−− Setaria hunzikeri Anton +−−−−−−− Setaria lachnea (Nees) Kunth ++−−−−−− Setaria leucopila (Scribn. & Merr.) K. Schum. ++−−−−−− Setaria macrostachya Kunth ++−−−−−− Setaria pampeana Nicora ++−−−−−− Setaria parviflora (Poir.) Kergue´len var. parviflora ++++++−− Setaria setosa (Sw.) P. Beauv. ++−−−−−− Setaria vaginata Spreng. var. vaginata +−−−−−−− Urochloa lorentziana (Mez) Morrone & Zuloaga +−−−−−−− 6 Tribe Andropogoneae Andropogon ternatus (Spreng.) Nees −−++−−−− Bothriochloa barbinodis (Lag.) Herter −−++−+−− Bothriochloa laguroides (DC.) Herter subsp. laguroides −−+++++− Bothriochloa saccharoides (Sw.) Rydb. −−+++−++ Bothriochloa springfieldii (Gould) Parodi −+−−−−−−

Blackwell Science Ltd 1997, Journal of Biogeography, 24, 197–204 204 Marcelo Cabido et al.

APPENDIX 1 (contd)

Presence (+) and absence (−)ofC3 and C4 grass species for eight sites along an altitudinal gradient in Central Argentina Altitude (m) 350 600 1000 1400 1600 1800 1900 2100

Elionurus muticus (Spring.) Kuntze +−++−−−− Heteropogon contortus (L.) Roem. & Schult. ++−−−−−− Schizachyrium condensatum (Kunth) Nees −−++−−−− Schizachyrium salzmannii (Steud.) Nash −−++−−−− Schizachyrium spicatum (Spreng.) Herter −+++++++ Sorghastrum pellitum (Hack.) Parodi −−++−+++

Blackwell Science Ltd 1997, Journal of Biogeography, 24, 197–204