Correlation between evolutionary history, flowering phenology, growth form and seral status for important veld grasses

G.E. Gibbs Russell Botanical Research Institute, Pretoria

Thirty species of veld grasses were analysed for their evolu­ Introduction tionary history, flowering phenology, growth form and range of veld types. These characteristics were correlated with succes­ In developing a method to assess veld condition for pastures, sional classes as reported in the literature, and the classes Foran eta/. (1978) and Tainton eta/. (1980) have listed grass were defined on the basis of the parameters considered. The species in Natal which occur in veld that has been subjected lowest and highest sera! states were clearly distinguished to different intensities of defoliation over an extended from each other, but there was some overlap between the in­ period. They divide the grasses into three major categories. termediate class and the highest and lowest classes. Si x of the species differed from other representatives of their class. 'Decreasers' are the most valuable pasture species and are They were either in vegetation types atypical of other species of intermediate sera! status. Under conditions of under­ in their group, were known to comprise a number of ecotypes, utilization, the Decreaser species are replaced by 'Increaser or were members of hybrid complexes. I' species which are of higher sera! status. Under conditions S. Afr. J. Bot. 1983, 2: 175- 180 of over-utilization, the Decreasers are replaced by 'Increaser II' species which are of lower sera! status. In this paper, Dertig veldgrasspesies is ten opsigte van blomfenologie, the three successional states are described and defined by groeivorm, evolusionere geskiedenis en verskeidenheid veldtipes geanaliseer. Hierdie kenmerke is met die their evolutionary history, flowering phenology, growth suksessieklasse, soos in die literatuur vervat, gekorreleer en form and range of veld types. The species in each group die klasse is op grand van die parameters onder bespreking, are listed in Tables I, 2 and 3. gedefinieer. Die laagste en hoogste seerklasse word 9uidelik van mekaar onderskei maar daar was 'n mate van oorvleueling tussen die intermediere klas en die hoogste en laagste klasse. Methods Ses van die spesies het van die ander verteenwoordigers in hulle klas verskil. Hulle was of in ongewone veldtipes, of The evolutionary history of each species is reflected in its bekend vir hulle ekotipes, of was lede van hibriedkomplekse. classification at subfamily and tribal level because each of S.-Afr. Tydskr. Plantk. 1983, 2: 175-180 the five grass subfamilies, Bambusoideae, Arundinoideae, , Chloridoideae and Pooideae, represents dif­ Keywords: Flowering phenology, grass subfamilies, pasture ferent evolutionary lines (Renvoize 1981) which developed grasses under different environmental conditions (Hartley 1963). The subfamily placing of the genera follows Clayton ( 1970, 1982) and Clayton eta/. (1974). The flowering phenology of each species was extracted from PRECIS (Pretoria National Herbarium Computerized Information System) (Morris & Manders 1981; Magill eta/. in press). Flowering specimens in the Herbarium were selected and sorted by month of flowering and locality as indicated by quarter degree square latitude and longitude grid. Only information for Natal specimens has been used. Flowering in each month is expressed as a percentage of the total number of flowering specimens reported for each species, so that comparisons between species can be made. Five species are represented by fewer than 20 specimens from Natal and could not show a clear flowering pattern, so were eliminated from the study. The growth form of the species is expressed according to an unpublished system of vegetative character states developed by the author. Measurements for each species G.E. Gibbs Russell were made using herbarium specimens from Natal at the Botanical Research Institute, Private Bag XIOI, Pretoria 0001, Republic of South National Herbarium (PRE), and were checked against the descriptions given by Tainton et at. (1976). Accepted 2 May 1983 The range of veld types in Natal for each species was I76 S.-Afr. Tydskr. Plantk., 1983, 2(3)

taken from the original lists of Tainton eta/. ( I980), checked Table 2 Species of intermediate seral status against Acocks (1975). (Decreaser) which decrease with either over­ utilization or under-utilization (Symbols as in Table 1) Results and Discussion Sub- Flowering Leaf No. of Subfamilies family time width veld types

The species in this study represent only three of the five grass Themeda triandra subfamilies, namely Panicoideae (I8 species), Chloridoideae Forssk. P EL 2 4 (II species) and Arundinoideae (I species). All three of these contortus subfamilies are most abundant in the tropics, and the C4 (L.) Beauv. ex Roem. & photosynthetic pathway, which is advantageous in warm Schult. P EL 2 4 climates, occurs only in these three subfamilies and not in Brachiaria serrata the other two (Renvoize I98I). The Panicoideae, composed (Thunb.) Stapf P EL 3 3 of the major tribes Paniceae, and Arun­ Panicum maximum Jacq. P EL 2- 4 dinelleae, evolved in high rainfall areas with a high annual Panicum deustum or midwinter temperature (Hartley I958a, I958b). The Thunb. P EL 3- 4 Chloridoideae, composed of the major tribes Eragrostideae, Rhynchelytrum seti- Sporoboleae and Chlorideae, evolved in arid or semi-arid jolium (Stapf) Chiov. P EL 1- 2 3 areas, again with a high annual or midwinter temperature Cenchrus ciliaris L. P EL 2 - 3 (Hartley & Slater I960). The Arundinoideae is a primitive amplec- subfamily with a number of diverse tribes that are not close­ tens (Nees) Clayton P L 3- 4 3 ly related and according to Renvoize (I98I) the tribe Monocymbium Aristideae is best included in this subfamily. Although a ceresiijorme (Nees) Stapf P L 2 3 climatic history for the whole tribe has not been determined, eriantha Steud. P L 3 De Winter (1965) has shown that most of the southern Eustachys paspaloides African species of Aristida occur in areas of low rainfall (Vahl) Lanza & Mattei C E 2 and that species which occur in higher rainfall areas often Eragrostis capensis (Thunb.) Trin. C E 1- 2 2 grow at sites where available moisture is limited. Eragrostis racemosa The subfamily of each of the species studied is shown in (Thunb.) Steud. C E 1- 2 3 Tables I, 2 and 3. The species of lowest seral status (In­ creaser II), are nearly all chloridoid or arundinoid, and by their evolutionary history may be expected to be better adapted to the drier conditions brought about by overgraz­ ing. The species of highest sera! status (Increaser I) are all Table 1 Species of lowest seral status (Increaser II) panicoid and by their evolutionary history may be expected which increase with over-utilization, replacing the to be better adapted to the more mesic conditions of unused species of intermediate seral status veld. The species of intermediate seral status (Decreasers) Sub- Flo.wer~ng Leaf No. of are a mixture of panicoid and chloridoid species. family• ume widthc veld types When moving upward in succession, panicoid grasses Aristida congesta subsp. replace the panicoid, chloridoid or arundinoid grasses of barbicollis (Trin. & Rupr.) De Wint. A L lower seral state. When moving downward in succession, Sporobolus pyramidalis chloridoid or arundinoid grasses replace the panicoid or Beauv. c L 2 - 3 chloridoid grasses of higher sera! state. Eragrostis plana Nees c L Sporobolus ajricanus (Poir.) Robyns & Tournay c L 2-3 Table 3 Species of highest seral status (Increaser I) hirta (L.) Stapf. p L(p) 2 4 which increase with under-utilization, replacing the Eragrostis curvula species of intermediate seral status (Symbols as in (Schrad.) Nees c EL 1- 2 2 Table 1) Eragrostis chloromelas Steud. c EL 1-2 Sub- Flowering Leaf No. of Bothriochloa insculpta family time width veld types (Hochst.) A. Camus p EL(p) 2 Eragrostis superba Peyr. c E 2-3 2 Tristachya leucothrix p Microchloa cajjra Nees c E 2 Nees E 2 2 Sporobolus stapjianus Alloteropsis semialata Gand. c E (R. Br.) Hitchc. p E 3 Eragrostis capensis Setaria nigrirostris (Thunb.) Trin. c E 1-2 (Nees) Our. & Schinz. p E 2-3 Eragrostis racemosa Eulalia villosa (Thunb.) (Thunb.) Steud. c E 1-2 Nees p E 2-3 Cymbopogon excavatus a Subfamily symbols: A = Arundinoideae; C Chloridoideae; P (Hochst.) Stapf ex Burtt Panicoideae Davy p L 2 - 3 2 b Flowering time symbols: L = late-flowering; EL = early-and-late­ spicatus flowering; E = early-flowering; p = prolonged (L.f.) Stapf p L 2 c Leaf width: width ranges taken from Table 4. S. Afr. J. Bot., 1983 , 2(3) 177

Flowering phenology the season and late in the season. Each of the sera! states Three flowering patterns were found: species with flower­ also has a group of species with a unique combination of ing peaks both early and late in the season (Figure 1); species subfamily and flowering time. All early-flowering panicoids with flowering peaks only early in the season (Figure 2) ; are in the highest sera! state; all early-and-late-flowering and species with flowering peaks only late in the season panicoids are in the intermediate sera! state; all late and (Figure 3) . 'Peaks' are taken to be months in which flower­ early-and-late-flowering chloridoids are in the lowest sera! ing is more than 1OOJo. Each of the basic flowering patterns state. On the other hand, the intermediate sera! state shares has a variant in which the flowering is more prolonged and certain combinations of subfamily and flowering time with the slope of the curve more gradual (Figure 4). The flower­ the higher and lower sera! states. Late-flowering panicoids ing pattern for each of the species is given in Tables 1, 2 occur in both high and intermediate sera! states, and early­ and 3. flowering chloridoids occur in both intermediate and low Each of the sera! states has species that flower early in sera! states.

50 -- Themeda triandra (j - - ·- Panic u m deus t u m 45 - - Heteropogon c ontortus z ··· ······ Eragrost1s chloromelas 40 a: 35 w ~ 30 0 25 ....J u.. 20

u.. 15

0 10

':....: 5

SEP OCT NOV DEC JAN FEB MAR APR MAY JUN JUL AUG MONTHS

Figure 1 Early-and-late-flowering pattern. There are two peaks, the first from October to Janaury with a trough in February and a lower peak in March. At least 5 months have flowering greater than 10%. Seven panicoid and two chloridoid species have this pattern.

50 Tristachya leu c othr i x (j 45 Eustachys paspaloides z Elionurus muticus Microchloa caffra 40 a: 35 w 3 30 0 ' . 25 ...J u.. 20

u.. 15 0 10 .•·. X 5 .-:'-' ,# .•...... _ .. ·

SEP OCT NOV DEC JAN FEB MAR APR MAY JUN JUL AUG MONTHS

Figure 2 Early-flowering pattern. There is a single peak with flowering reaching IOOJo as early as September and extending to January. Only 3 or 4 months have flowering above 10%. Three panicoid and six chloridoid species have this pattern. 178 S.-Afr. Tydskr. Plantk. , 1983, 2(3)

50 Cy rn bopogon excavatus Er agro s ti s pl ana (j 45 D i h e ter o p ogon a mp lec t ens z \ Sp oro b o l u s py r am idalis 40 I I I a: I \ 35 ~ - w I ·•. \ ~ 30 0 ·,, t . ·. \ 25 ..J }_ u.. 20 ------1 ·· ·,_- ,; f \ ·.\ u.. 1 5 I •- ·--·- 0 10 ------

X 5 .\ / SEP OCT NOV DEC JAN FEB MAR APR MAY JUN JUL AUG MONTHS

Figure 3 Late-flowering pattern. There is a single peak with flowering reaching IOOJo only in January or February and continuing to March or April. Only 3 or 4 months have flowering above 10% . Five panicoid and four chloridoid species have this pattern.

50 Bothriochloa insculpta (.') 45 Eulalia villosa z 40 a: 35 w ~ 30 0 25 ...J u.. 20 ------~-.--e._:: ----- / - ~ - ~ ·...... 15 ..... ·•··. u.. ·.. "\ 0 · ··· ~ .. 10 --- 7- \-- -... 5 . _/ ...... \ X ....-- ·

SEP OCT NOV DEC JAN FEB MAR APR MAY JUN JUL AUG M 0 N T H S Figure 4 Prolonged-flowering variants of the three basic patterns. Flowering spans the months of January and February when other patterns are declin­ ing or increasing, but flowering never reaches 20%. All three species with this variant are panicoid.

Vegetative characteristics vironments are in the lowest sera! state and have the nar­ Vegetative characters were determined for all species, and rowest leaf blades, whereas panicoid grasses with an evolu­ are shown in Table 4. The 30 species have similar character tionary history of adaptation to wetter environments are states for most of their organs, showing strong convergence higher in the succession and have broader leaf blades. from diverse evolutionary backgrounds. Slight differences between the species occur in foliage height and greater dif­ Range of veld types ferences occur between them in leaf blade width, as shown The number of veld types from which each species has been by the numbers of species occurring in each of the character recorded is given in Tables 1, 2 and 3. The majority of state categories for these two characters. The leaf blade species in the intermediate seral state are important in several width for each species is given in Tables 1, 2 and 3. veld types, but the species in the highest and lowest sera! Leaf blade width is generally correlated with sera! state states are usually important in only one or two veld types. and subfamily in that chloridoid and arundinoid grasses Thus, the species of intermediate seral status are of with an evolutionary history of adaptation to dry en- widespread occurrence, but different species characterize the S. Afr. J . Bot., 1983, 2(3) 179

Table 4 Vegetative characters of all species in the Table 5 Species characteristics typical of the three study. Some species may exhibit more than one state successional states for a single character Highest sera! state (Increaser I) No. of spp. showing Each spp. in I - 2 veld types character state only Panicoid early-flowering Medium to broad leaf blade t Growth form width ______Panicoid late-flowering Annual, fibrous root I Perennial, mat-forming, stoloniferous 3 Intermediate sera! state I Perennial, mat-forming, rhizomatous 0 (Decreaser) f Perennial, -forming, rhizomes Each spp. in I - 4 veld types Panicoid early-&-late-flowering compact 33 Medium to broad leaf blades t Perennial, rhizome solitary 0 Lo:e~t ~e:l~t~te-(l~c~e=e~ I~) ____ Chloridoid rrly-flowering Culm position Each spp. in I - 2 veld types f Erect 32 only Chloridoid early-&-late-flowering Decumbent 5 Filiform to medium leaf blade width Chloridoid late-flowering Prostrate 0

Culm branching Unbranched 28 Branched only at base 0 Variation in vegetation types Branched above base 8 Two of the problem species, Eustachys paspaloides and Bothriochloa inscu/pta, are given only for the lowveld. This Leaf position vegetation type includes the Valley Bushveld which Acocks Cauline only (1975) classifies as a karroid vegetation type. Its affinity is, Basal only 2 therefore, with the arid west of the country rather than with Basal and cauline 32 the tall grasslands that extend far into tropical Africa. It is in the lowveld that a chloridoid species may be higher Maximum foliage height in the succession and that a panicoid species may be lower. 30 - 200 mm 5 Another species, Eulalia vil/osa, is reported only from the 200 - 500 mm 27 highland sourveld and has in addition an atypical prolonged 500 - 1000 mm 19 flowering pattern, as does Bothriochloa inscu/pta. 1- 1,5 m 9 1,5 - 2 m I Ecotypes 0 Greater than 2 m Eragrostis racemosa and E. capensis both occur in the lowest and in the intermediate sera! states. Both the species have Leaf blade width wide ranges in Africa and it may be that their differing 1-2 mm 12 behaviour is due to ecotypic differences commonly en­ 2 - 5 mm 22 countered in grasses of widespread distribution. Alternative­ 5 - 10 mm 13 ly, they may be at different stages of succession in different Greater than 10 mm 3 communities because their sera! state may depend on the species with which they are associated.

Hybridization highest and lowest sera! states in different veld types. Hyparrhenia hirta is the only species in the lowest sera! state that is panicoid, has a prolonged flowering pattern and is Definition of successional classes reported from all four veld types of Tainton eta/. (1980). The characteristics of the species in each of the successional Hyparrhenia is a large and difficult tropical renowned classes are summarized in Table 5. The highest and the for the hybridization between its species, and H. hirta is lowest sera! states are distinguished from each other on the a member of a complex that includes H. anamesa, H. basis of subfamily, flowering phenology and leaf blade filipendu/a and H. dregeana (Clayton 1969). It is widely width. The intermediate sera! state has some species that recognized that hybrid populations often inhabit disturbed show characteristics of the highest sera! state and other sites and it may be for this reason that specimens named species that show characteristics of the lowest sera! state. H. hirta are often found in overgrazed areas. The broad This summary disregards a few problem species that do not flowering curve (Figure 4) may further illustrate its hybrid appear to fit in with the rest of their class. Their aberrant state since the flowering peaks of the component species behaviour may be the result of several different factors may tend to run together in a complex hybrid. which are discussed below. Conclusions Problem species The present study shows that evolutionary history, flower­ Each of the successional classes has at least one species that ing phenology and certain morphological features are cor­ differs from the pattern established by the others. These six related with the ecological behaviour of species. Further­ problem species exhibit biological traits that set them apart more, information on herbarium specimens, collected from from the other species in the study. many localities over a long time, shows patterns that are 180 S.-Afr. Tydskr. Plantk., 1983, 2(3) not easily discernible from the examination of a few in­ FORAN, B.D., TAINTON, N.M. & BOOYSEN, P. DE V. 1978. The dividuals and which in the field may be obscured by local development of a method for assessing veld condition in three or annual variations. grassveld types of Natal. Proc. Grass/d. Soc. sth Afr. 13 : 27-33. The results reported here are based on species lists for HARTLEY, W. 1958a. Studies in the origin, evolution and distribu­ Natal. The patterns derived from them will be tested by tion of the Gramineae. I. The tribe Andropogoneae. Aust. J. Bot. 6: 116-128. comparing them with similar data from other regions. HARTLEY, W. 1958b. Studies in the origin, evolution and distribu­ tion of the Gramineae. II. The tribe Paniceae. Aust. J. Bot. 6: Acknowledgements 343-357. Thanks are due to W.S.W. Trollope, R.H. Westfall and HARTLEY, W. & SLATER, C . 1960. Studies in the origin, evolution O.A. Leistner for helpful discussions and to M.D. Panagos and distribution of the Gramineae Ill. The tribes of the subfamily and W. Raux for their work in preparing the figures. Eragrostideae. Aust. J. Bot. 8: 256 - 276. HARTLEY, W. 1963. The phytogeographical basis of pasture introduction. Genetica Agraria 17: 135 - 160. References MAGILL, R.E., GIBBS RUSSELL, G.E., MORRIS, J .W . & GON­ ACOCKS, J.P.H. 1975. Veld types of . Mem. Bot. Surv. SALVES, P. (in press.) PRECIS - the Botanical Research In­ S. Afr. No. 40. stitute Herbarium Data Bank. Bothalia. CLAYTON, W.D . 1969. A revision of the genus Hyparrhenia. Kew MORRIS, J.W. & MANDERS, R. 1981. Information available within Bull. Add. Ser. Jl. Her Majesty's Stationery Office, London. the PRECIS data bank of the National Herbarium, with examples CLAYTON, W.D. 1970. Gramineae (Part 1) . In: Flora of tropical of the uses to which it may be put. Bothalia 13: 473 - 485 . East Africa, eds. Milne-Redhead, E. & Polhill, R.M. Crown RENVOIZE, S.A. 1981. The subfamily Arundinoideae and its posi­ Agents, London. tion in relation to a general classification of the Gramineae. Kew CLAYTON, W.D., PHILLIPS, S.M. & RENVOIZE, S.A. 1974. Bull. 36: 85 - 102. Gramineae (Part 2). In: Flora of tropical East Africa, ed. Polhill, TAINTON, N.M., BRANSBY, D. & BOOYSEN, P . DE V. 1976. R.M. Crown Agents, London. Common veld and pasture grasses of Natal. Schuter & Shooter, CLAYTON, W .D. 1982. Gramineae (Part 3). In: Flora of tropical Pietermaritzburg. East Africa. A.A. Balkema, Rotterdam. TAINTON, N.M., EDWARDS, P.J. & MENTIS, M.T. 1980. A DE WINTER, B. 1965. The South African Stipeae and Aristideae revised method for assessing veld condition. Proc. Grass/d. Soc. (Gramineae). Bothalia 8: 199 - 404. sth Afr. 15: 37-42.