Taxonomy and phylogeny of two subgroups of Pelargonium section Otidia ( Geraniaceae ) . 1 . The Pelargonium carnosum complex

This contribution deals with the taxonomy and phylogeny of the  Pelargonium carnosum complex, a group of closely related taxa of Pelargonium L’Her. section  Otidia (Sweet) DC. (Geraniaceae) that is distributed in the winter rainfall area of South Africa. According to molecular analyses via AFLP, P. adriaanii M.Becker & F.AIbers,  P. carnosum (L.) L’Uer., P.  ferulaceum (C'av.) Willd. and P. polycephalum (E.Mey. ex Harv.) R.Knuth form a monophyletic clade. Although hybridization may occur between the taxa, three are assigned to specific rank. The fourth taxon, P. ferulaceum is recognized as a subspecies ot'P carnosum. As is implied from the occurrence of morphological intermediates and partly from molecular evidence,hybridization does not only occur among the taxa in this complex but also involves species closely related to this group  (P. panifiorum J.C.Wendl., P. laxum (Sweet) G.Don, P. dasyphyllum R.Knuth). For the taxa in the P. carnosum complex, distribution areas are delineated and diagnostic features that have until now remained obscure, are outlined.


INTRODUCTION
The genus Pelargonium L'Hér.com prises ± 280-290 species w hich are subdivided into 16 sections (B akker et al. 2004).The infrageneric classification relies on m olecu lar evidence, on differences in chrom osom e sizes and basic chrom osom e num bers, and on geographical distribution and growth forms.W ithin the m ajor group characterized by small chrom osom es, section Otidia (Sw eet) DC. belongs to a subgroup show ing xerophytic growth.Within this 'xerophytic clad e', it is part o f the so-called w inter rainfall clade (B akker et al. 2004).Section Otidia com prises 25 taxa, some o f them distinctive and isolated, others closely related and hardly distinguishable.
The Pelargonium carnosum (L.) L'H ér.com plex includes several taxa that are linked by interm ediates.M orphological interm ediates are usually assigned to introgression.The close relationship o f these taxa w as recognized early in the taxonom ic history o f Pelargo nium.H arvey (1860), w hen describing P. polycephalum (E.M ey.ex H arv.) R.K nuth as P. ferulaceum var.poly cephalum, stressed its strong resem blance to P. carno sum.D yer (1953) reduced P. ferulaceum (C av.) W illd. and P. polycephalum to the rank o f a variety under P. carnosum, w hich can be taken as the year o f inception o f the P. carnosum com plex.B ecker & A lbers (2005a) added P. adriaanii M .B ecker & F.AIbers, thus increasing the n u m b e r o f taxa in this com plex to four: P. adriaanii, P. carnosum, P. ferulaceum and P. polycephalum.
V orster (1990) placed the closely related Pelargonium parviflorum J.C .W endl. in the P. carnosum com plex as well.H ow ever, as P. parviflorum com prises several taxa that are ch aracterized by a distinctive floral structure, w e prefer to treat it as a separate taxon and w ith further taxa as a separate su b g ro u p (P. parviflorum com plex, B ecker & A lbers in press a).
A ph y lo g en etic tree that resu lts from extensive m o lecu lar analyses is p resented.P o lym orphic m ark ers have been detected via A FL P (am plified fragm ent length p o ly m o rp h ism , Vos et al. 1995), a m ethod that requires no p revious k n o w led g e o f D N A sequences and p rovides a large am ount o f reliab le and repeatable bands.A FL P m arkers are generated from the entire sp ec trum o f genom ic D NA including fast ev olving regions, leading to a high resolution at th e su b sp ecies and even p o pulation level in phylogenetic analyses.W e discarded sequence analyses based on n uclear ITS and plastid trn-LF regions, as the differences b etw een stu d ied taxa w ere too m arginal.

Plant material
S pecim ens o f the living collection o f M unster B otani cal G arden (Table 1) w ere in cluded in the m olecular analysis.V oucher specim ens w ere d ep o sited in M SU N .For d elim itin g the distribution ran g es o f th e taxa, 224 herbarium specim en s w ere ex am in ed from the follow ing herbaria: BM , B O L , K, M S U N , N B G and PR E -acro nym s as in H olm gren et al. (1990).

Cladistic analysis
Each A FL P fragm ent w as counted as a separate p u ta tive locus and scored as present (1) or absent (0) for each sam ple.O nly polym orphic bands that could be read unam biguously on each gel im age w ere used for data analysis.
Phylogenetic analyses w ere perform ed w ith PAUP Version 4.0b 10 (Sw offord 2002), using neighbour join ing (NJ; R estriction-site distances: U pholt) and a maxi mum parsimony criterion.For the latter, starting trees w ere generated by stepw ise addition, sw apping on best tree only in case o f m ultiple trees.O ne thousand random addition replicates w ere chosen.The heuristic search for best topologies used TBR branch sw apping.Support for clades in both distance and parsim ony analyses was m easured using the non-param etric bootstrap m ethod (Felsenstein 1985; 10 000 replicates).

RESULTS
The taxa in the P. carnosum complex: etymology and taxonomic history' The oldest mention o f Pelargonium carnosum is found on a herbarium sheet dating back to 1724 {BM649367, Fig ure 1A).The brief diagnosis reads: 'Geranium africanum frutescens, Chelidonii folio; petalis florum angustis, albidis; carnoso caudice'.The herbarium specimen originates from a plant that arrived at Chelsea Physic Garden in Lon don in the same year.The collector and place o f origin o f this specimen are not known.A first detailed description o f P. carnosum was provided by Dillenius in 1732, who described the species under the phrase name ' Geranium Afric.carnosum, petalis angustis albicantibus'-a pre-Lin-

Morphological characters o f section O tidia
In addition to the com m only occurring succulent stem s and pinnate leaves, the set o f characters defining section Otidia also includes short-spurred flowers.
The typical auricles borne at the base o f the poste rior petals are restricted to this section, although sim ilar petal structures are found in certain species o f sections Campylia, Hoarea, Ligularia and Pelargonium (Struck 1997).Stam ens that curl upw ards at the end o f the staminate phase are restricted to section Otidia and a couple o f species in section Pelargonium (Struck 1997).Otidia.H ow ever, m ost taxa in the P. carnosum co m plex and the closely related P. parviflorum com plex (B eck er & A lbers in press a) are distinguished by a char acter w hich is otherw ise absent in the section (except in P. a I ter nans): the pedicel is m uch shorter than in the rem ain in g Otidia species.T he ratio betw een the lengths o f hy p an thium and pedicel-a valuable characteristic in Pelargonium (M iller 1996)-varies betw een 2 and 10 w ithin both com plexes, but betw een 0.1 and 1.0 in the rem ain in g m em bers o f Otidia s.str.H ow ever, P. adriaa nii does not fit into this pattern: in this species the p ed i cel is m uch longer than the hypanthium .T herefore, no p h enotypic character clearly delineates the P. carnosum co m plex.T he taxa in the P. parviflorum com plex differ from those in the P. carnosum com plex in possessing tiny, m ostly yellow ish petals.

Pelargonium alternans
Diagnostic features in the P. carnosum complex (Table 2) In Pelargonium adriaanii and P. carnosum subsp.carnosum the lateral roots form series o f sm all tubers; P. carnosum subsp.ferulaceum and P. polycephalum Pelargonium polycephalum likew ise differs from P. carnosum subsp.carnosum and P. adriaanii by a larger n um ber o f pseudo-um bels.H ow ever, in contrast to P. carnosum subsp.ferulaceum, these do not em erge su c cessively at the tip o f the co ntinuously grow ing p ed u n cle, but develop in large num bers from already visible buds.Each o f the 4 or 5 nodes o f the principal axis m ay p roduce 10 15 p seudo -um bels w ith about 10 flow ers each, w hich m ay add up to som e 500 flow ers per inflor escence w ithin a relatively short period o f tim e. C o m pared to P. carnosum subsp.ferulaceum, the life span o f an inflorescence is short in P. polycephalum: the period betw een full flow ering and fruiting and im m ediate w ith ering o f the inflorescence w ill last a few w eeks only.H ence, fully dev elo p ed inflorescences are easily assigned to the respective taxa, but not you n g inflorescences, as these all represent v ariations o f the sam e basic structural type.

Molecular analysis (AFLP)
The phylogram (Figure 5) results from a neigh bour joining (N J) analysis using 416 A FLP m arkers.There are three questions w ith regard to the Pelargo nium carnosum com plex: 1, is this com plex a m onophyletic group?; 2, are the distinct phenotypes reflected in distinct genotypes?; and 3, can the presum ed existence o f structural interm ediates be verified?AFLP data are also consistent with the notion o f phe notypic intergrades am ong the two subspecies o f Pelar gonium carnosum (Hybrid 1: A&B4444.A&B43 73, A&B4426.STEU2401) and am ong P. carnosum subsp.car-nosum/P polycephalum/P.adriaanii (Hybrid 2: A&B4389, A&B4397).However, possible interbreeding processes also involve taxa in the P. parviflorum complex.
In term s o f the grouping o f taxa, one w ould expect both subspecies o f Pelargonium carnosum to share one clade.H ow ever, subsp.ferulaceum appears in the cladogram as a sister group to clade B2b, w hich contains not only subsp.carnosum but also P. polycephalum and P. adriaanii.T his m ay be seen as a conflict o f m olecular data and proposed taxonom y, w hich is based on m or phology.O n the other hand, this sister group relation ship to the rem aining taxa o f the P. carnosum com plex m ight reflect the ongoing gene flow betw een P. carno sum subsp.ferulaceum and the P. parviflorum com plex, w hich has been predicted after evaluation o f m orpholog ical traits.
H ybrid 1 com prises four plants in the cladogram that are supposed to result from gene flow betw een both sub species o f Pelargonium carnosum.A s subsp.ferulaceum and subsp.carnosum do not share a clade, it is no sur prise that the sam e is true for their hybrids.
The distribution areas o f several taxa o f the tw o co m plexes m eet in the southern part o f the K nersvlakte.In this area particularly, the tw o subspecies o f P. carnosum and P. parviflorum s.I. appear to interbreed.C ollection A&B4405 from C lanw illiam show s a phenotype sim ilar to the interm ediates o f the tw o subspecies o f P. carno sum (A&B4373, V redendal population), but it is only one selected from an array o f plants that intergrades to the P. parviflorum com plex (B ecker & A lbers in press a).

Original descriptions
The distribution area o f Pelargonium carnosum was assum ed to be fairly large (Van der W alt 1977;Vorster 1990), since the delineation o f P. carnosum subsp.car nosum w as blurred, due to the occurrence o f num erous interm ediates.Furtherm ore, even taxa foreign to this com plex w ere uncritically grouped under P. carnosum as well.H ow ever, w hen taxonom ically treated in a stricter sense, P. carnosum is actually restricted to a com para tively sm all geographical area (Figure 4).This taxonom ical concept is in line w ith D illenius's original description o f 1732 and the available herbarium records dating back to the first h a lf o f the 18th century both w ith respect to the m orphological characteristics as w ell as to their geo graphical distribution.

Morphology and ecological function in a geographical context
M any structural differences betw een the taxa in the com plex can be explained as adaptations to prevailing environm ental conditions.With regard to leaf shape, tw o basic traits can be distinguished w hich correlate to the geographical distance from the coast.Plants occur ring close to the sea exhibit virtually non-succulent and densely hairy leaves, w hereas taxa from further inland are characterized by succulent and (to the naked eye) glabrous leaves.A nother character shaped by habitat factors is the underground organs o f the plants.Pelargo nium adriaanii and P. carnosum subsp.carnosum occur ring in S andveld habitats near the A tlantic coast pos sess lateral roots w ith thickened sections, w hereas the tw o taxa occurring further inland, P. carnosum subsp.ferulaceum and P. polycephalum, m ostly on rugged soil, exhibit fibrous root system s lacking tubers.
Since the taxa in the Pelargonium carnosum com plex are adapted to different clim atic, edaphic and topo graphical factors and are associated w ith certain habitats, one could view them as m ere ecotypes o f a single taxon.H ow ever, this view is contradicted by the observation that P. adriaanii and P. polycephalum m aintain their typi cal grow th habit even under cultivation, and do not seem to hybridize on a large scale, w hich speaks in favour o f treating them as separate species.W'hile interm ediates betw een P. adriaanii, P. polycephalum and P. carnosum w ere rarely recorded, the situation is different in "P.car nosum' and 'P.ferulaceum'.In view o f their extrem ely different habitats (Sandveld and Little K aroo) on the one hand and their relatively subtle structural differences on the other hand, it seem s appropriate to treat them as sub species.This view is supported by the occurrence o f a range o f phenotypic interm ediates w hich is correlated to the distance from the sea and the im m ediate degree o f aridity, respectively.

Molecular analysis and its taxonomic application
The results o f the molecular analyses (AFLP) are mostly consistent with the hypotheses based on m orpho logical observations.The four taxa in the Pelargonium carnosum complex emerge as a monophyletic group within section Otidia (Figure 5).P. carnosum subsp.car nosum and P. carnosum subsp.ferulaceum were treated as a single taxon by many authors (Van der Walt 1977;Vorster 1990), since neither their geographical range nor their morphological features were sufficiently known.Our molecular study confirms their close relationship but also provides evidence in favour o f the existence o f two distinct genotypes.
The close relationship o f Pelargonium adriaanii and P. polycephalum as revealed by the AFLP analysis is sur prising as there are profound differences in floral struc ture between P. adriaanii and P. polycephalum.Preced ing the description o f P. adriaanii, a short pedicel was among the diagnostic features given for the circum scrip tion o f the complex.The constricted pseudo-umbels o f P. polycephalum versus the loose pseudo-umbels o f P. adriaanii represent the extremes in this feature.
If the analysis is exclusively restricted to typical samples in the various taxa, high values are yielded in the maximum parsimony analysis and increased lengths of branches in the phylogenetic tree (not represented in Figure 5).The inclusion o f all morphological intermedi ates demonstrates that interbreeding is the rule within the Pelargonium carnosum complex on the one hand (Figure 5) and among the P. carnosum complex and the closely related P. parviflorum complex on the other hand (Becker & Albers in press a).
Finally, the question arises: which taxonomic rank is appropriate in the Pelargonium carnosum complex?Following the biological species concept (Dobzhansky 1937), a species is a reproductive group; interbreeding among species is prevented by various isolation mecha nisms.These include, in simple terms, mechanical, tem poral.habitat-related and genetic barriers to interbreed ing (Avise 2004)  A recent breakdown o f reproductive barriers result ing from human action as has been presumed by Vorster (1990) cannot be excluded, but such an assumption is not needed to explain the large number o f interbreeding taxa.A shift in species distribution ranges due to recent climatic changes may have played a role.
As long as there is no artificial transport o f propagules.the spread o f settlements, agriculture, overgrazing and diamond mining could also isolate small populations from each other, as this would render large intermittent areas unsuitable to support the natural plant life.Nev ertheless, man will hardly contribute to increase biotic diversity but rather destroy genetic diversity o f the local flora as well as its natural habitats.Pelargonium adriaa nii is currently threatened with extinction unless the dia mond companies denounce their rights to fully exploit the diamond fields within the species' range.
The massive impact o f human activities on the veg etation within the Cape flonstic region is uncontested.Today the species-rich flora and fauna is protected within an increasing number o f national parks and nature reserves.However, the Cape floristic region stands out in its wealth o f endemics which often show a very localized distribution outside o f protective areas.In order to pro tect even this species from extinction, centres o f diver sity have to be identified and plant diversity has to be put on record through taxonomic contributions.A further article on Pelargonium sect.Otidia will elucidate the unexpected radiation within the P. paniflorum complex, which hitherto has been treated as a single taxon.

G
en o m ic DNA w as ex tracted from ± 500 m g o f fresh le a f tissue p er plant follow ing the CTAB pro cedure describ ed by D oyle & D oyle (1987) and m odi fied by B akker et al. (1998).A FL P (am plified fragm ent length poly m o rp h ism ) analyses w ere p erform ed using the protocol o f Vos et al. (1995), w ith m inor m odifi catio n s (M arschalek 2003).D NA w as restricted w ith enzym es EcoRI (rarely cutting) and M sel (frequently cutting).S ingle strands o f EcoRI and M sel adapter w ere 3 A G -3\ respectively.Nine com binations o f prim ers based on three selective bases (EcoRI-AAC, -AGG, -ATA and M sel -CAA, -CAG, -CCG, -CGA,
J.C.W endl.w hich hitherto has also been placed in section Otidia, differs in various cha racters (B ecker & A lbers in press b).A large genetic gap betw een this species and the rest o f the section ha.s been established (B akker et al. 2004; B ecker & Albers in press c), and P. alternans is excluded from the section in the strict sense (= Otidia s.str.) in the present account We refer to Otidia s.I. in order to indicate traditional cir cum scription o f the section, i.e. including P. alternans.The taxa in the Pelargonium carnosum com plex do not differ m uch from the other m em bers o f section adriaanii (Figure ID ) and P. poly cephalum (Figure IF, G ) can develop into large plants o f 1 m across that possess stem s o f 50 m m in diam eter.In P. carnosum subsp.carnosum (Figure IE ) the stem s are m uch thinner and in subsp .ferulaceum(Figure 1H) they rem ain shorter.

T
he four tax a in the Pelargonium carnosum com plex o ccu r w ithin clearly circu m scrib ed distribution areas w h ich do n ot o verlap m uch (F igure 4).P. adriaanii from the N o rth ern C ape is g eographically w ell isolated: there is no reco rd o f any o th er m em b er o f section Otidia w ithin a rad iu s o f 50 km .O nly a single plant resem b lin g P. parviflorum is know n from K leinsee south o f Port N o llo th (Drijfhout 2842 sub STEU2979).W ith the exception o f a single d isp u ted specim en, P. adriaanii has alw ay s been co llected near the co ast at altitudes o f up to 50 m (B eck er & A lbers 2005a).P. adriaanii lodges at the fringes o f the G ariep C entre, w h ich is a m ajo r centre o f en d em ism (Van W yk & S m ith 20 0 1 ) b o rdering on the southern N am ib w h ere the species receives less than 100 m m annual rainfall (F igure 4).Pelargonium carnosum subsp.carnosum is ex c lu sively found in the W estern C ape w ith in an area that stretches from the A tlantic coast to the chain o f the Cede rb e rg -S w a rtru g g e n s-H e x riv ie r M o untains at altitudes o f up to 200 m.R eceiving an annual rainfall o f m ore than 300 m m , this region exhibits tran sitio n s to fynbos v egetation.T he m ost typical specim en s o f P. carnosum subsp.carnosum are restricted to the S andveld rig h t at the coast.T he tw o rem ainders in the P. carnosum co m plex o ccu r further inland, receiving 1 5 0 -2 5 0 m m o f annual precipitation.The area o f P. carnosum subsp.ferulaceum is largely situated in the W estern C ape and stretches into the N orthern Cape.T he ran g e o f subsp.ferulaceum borders on the area o f Pelargonium carno sum subsp.carnosum, but instead o f p ro ceed in g to the A tlantic coast, stretches in the opp o site d irection tow ards the sh ru b lan d o f the G reat and L ittle K aroo.T he su b sp e cies occurs m ostly at altitu d es o f 6 0 0 -1 000 and in the vicinity o f V anrhynsdorp, m erely at 100 m.P. polyceph alum is largely restricted to th e N am aq u alan d H ills in the N orthern C ap e P rovince at altitudes o f up to 1 200 m.
FIGURE 4.-Distribution o f taxa in P. carnosum complex accord ing to records from herbarium and living specimens.Dark grey shading = winter rain fall area; light grey shading = annual rainfall area.

A
lthough the four taxa in the Pelargonium carnosum com plex are clearly distinguished, the existence o f inter m ediates is unm istakable.Interbreeding has repeatedly been recorded from areas w here different taxa in the P. carnosum com plex occur in close proxim ity.H ybrids w ithin the com plex The region w est o f the C ederberg (V red en d al-C lanw illiam ) harbours hybrids betw een the tw o sub species o f Pelargonium carnosum w hich exhibit leaf features o f both parental taxa (A&B4373).Plants from this area show the sam e type o f indum entum as found in typical P. carnosum and pinnae as stalked and narrow as found in P. carnosum subsp.ferulaceum.Plants from the coastal region near P apendorp and D oringbaai m ostly exhibit pink petals (A&B4389, A&B4397).In this region, not less than three genotypes appear to intergrade, as the specific characters o f all three taxa w ere found to com bine in plants grow ing next to each other.T hese plants develop leaves as observed in P. carnosum subsp.carnosum, the distinct inflorescence o iP polvcephalum and the lone pedicels o f P adriaanii H ybridridzation involving taxa outside this com plex The closest relatives o f the Pelargonium carnosum com plex are found in the P. parviflorum com plex.Struc tural interm ediates occur in several regions w hich point to large-scale interbreeding betw een both com plexes.The resulting cluster o f hybrids are discussed elsew here in m ore detail (B ecker & A lbers in press a) and are only briefly characterized in the present account.In this clus ter o f hybrids, floral structure is conspicuously varied exhibiting a range o f petal colours and shapes.The closest relatives o f both com plexes com bined are Pelargonium laxum (Sw eet) G .D on and P. dasyphyllum R.K nuth (B ecker et a l 2008).Both species are clearly d istinguished on account o f a set o f structural charac teristics.P. laxum possesses posterior petals w hich are sharply reflexed from bases at nearly 180° and unusually long stam ens.P. dasyphyllum exhibits a cushion-shaped grow th habit and relatively sm all leaves.In both spe cies, plants recorded from the geographical fringes also exhibit characters o f the P. carnosum com plex.O ne record pertains to a plant o f rem ote resem blance to Pelargonium dasyphyllum (A&B4286) w hich we tracked dow n in the m idst o f a population o f typical m em bers o f that species.In this plant, the stem is unusu ally thickened and leaves are exceedingly large.The w ide range o f different petal shapes o f individual speci m ens o f P. dasyphyllum even includes the petal structure found in typical P. carnosum flowers.
N o n -p aram etn c bootstrap values (BV s) are indicated.A maximum parsimony analysis w as also undertaken (not show n) em ploying 193 inform ative characters.The m ajor groupings o f taxa w ere congruent betw een both ^nalvses.

FIGURE
FIGURE 5.-Cladistic analysis o f taxa in P. carnosum complex based on AELP patterns; phy logenetic tree reconstructed by neighbour joining analy sis using 416 AFLP markers.Bootstrap values derived from a maximum parsimony analy sis employing 193 informative characters are indicated for clades that are congruent to the strict consensus tree.Col lections that were unequivo cally grouped under defined phenotypes o f the complex are highlighted with dark grey shading.

C
om parison w ith other m em bers o f section Otidia s.I. (P.alternans, P. ceratophyllum, P. crithmifolium Sm .. P. dasyphyllum, P. klinghardtense, P. laxum and P. paniculatum) yields indications as to the m onophyly o f the com plex.The study also involved the subspecies o f the closely related P. parviflorum com plex ( B ecker & A lbers 2005b, in press a).In the cladogram (F igure 5) the four taxa o f the Pel argonium carnosum com p lex em erge as a single m onop hyletic group (clade B) w ith the P. parviflorum c o m plex (clad e A) as sister group.T he clade that com p rises clad e A and clad e B is w ell su p p o rted by a BV o f 95.W ith less go o d sup p o rt (B V 79), P. dasyphyllum and P. laxum share a clad e w ith the group that co m p rises clad es A and B. D espite the m any m o rp h o lo g ical signs o f in terb reed in g b etw een the tw o co m p lex es, the ty p i cal p h en o ty p es o f P. adriaanii, P. polycephalum and su b sp ecies o f P. carnosum em erg e as m o n o p h y letic gro u p s (h ig h lig h ted in dark grey in F ig u re 5).A fter ex clu d in g the sam p les o f the su p p o sed h y b rid s from the an aly sis.B V s rise to 9 5 -1 0 0 in support o f these g ro u p s (not rep resen ted in F igure 5).T he clad o g ram seem s to co rro b o ra te the p resu m ed in terb reed in g p ro cesses am o n g several tax a in the P. carnosum co m plex.

W
ith regard to the circum scription o f Pelargonium carnosum subsp.ferulaceum, contradictions in the ear lier descriptions (B urm an f. 1759; C avanilles 1787; L in naeus 1826) led to a sim ilar state o f taxonom ic limbo.T his becom es obvious w hen com paring le af characters given for 'P.ferulaceum' and 'P.carnosum', respec tively (degree o f division or separation o f the le af blade, degree o f hairiness and succulence).B urm an's iconotype o f P. ferulaceum contains tw o variants o f the sam e taxon w hich differ in le af shape and (according to the d iagno sis) in petal colour.The significance and reliability o f this inform ation can be questioned in view o f B urm an's erroneous representation o f the num ber o f petals: the author believed both o f his specim ens to carry a single posterior petal and three or four anterior petals, w hich is not found in the genus Pelargonium.So it happens that the view adhered to in the present account o f 'Pelargonium ferulaceum' not being synony m ous to "P. carnosum' is based to a lesser degree on the original description (with the exception o f leaf m orphol ogy) than on the extensive study o f herbarium speci m ens, observations in the field and a m olecular analysis o f populations sam pled from their natural habitats.W hile the precise identity o f the specim ens on w hich 'Pelargonium ferulaceum' w ere based rem ains obscure, the diagnosis o f P. polycephalum is fairly straightfor ward.A lthough w e could not exam ine the holotype itself (Drêge 3244), we w ere able to study a com parable speci m en (Drêge 1033) w hich clearly show ed the diagnostic features given in the original description for P. poly cephalum: capitate pseudo-um bels and a panicle-like inflorescence.The notion o f a conspicuous indum entum show n on the leaves rem ains incom prehensible.All dried and live specim ens seen by us show ed alm ost glabrous leaves.
. Mechanical isolating mechanisms, as brought about in the flower o f different subgroups o f Pelargonium alternans (Becker & Albers in press b), are absent in the P. carnosum complex.Despite differences in petal size and in lengths o f pedicels, the taxa show basically the same floral structure.In contrast, a seasonal isolation resulting from the development o f different flowering periods is found in Pelargonium polycephalum.Nevertheless, a slight over lap o f this species' reproductive season with that o f P. carnosum subsp.carnosum results in the occurrence o f hybrids in the region o f Papendorp-Doringbaai (3118 CA and CC).Interbreeding between P polycephalum and the cluster o f hybrids in the P. parviflorum complex could also be expected due to their generally sympatric distribution and insufficiently separated flowering seasons.However, the occurrence o f rudimentary and.consequently, sterile anthers in many 'P.polycephalum' plants speak against consecutive interbreeding among P polycephalum and P. parviflorum beyond the FI genera tion (Becker & Albers in press a).
related or geographical isolation is particu larly found in Pelargonium adriaanii.While the distri bution areas o f the remainders in the complex border on each other, the range o f P. adriaanii is situated fairly isolated in the region around Port Nolloth-as far as this can be assessed in view' o f the fact that we were unable to enter the local diamond mining area.From rare occur rences o f P. adriaanii-like features near Papendorp, the existence o f a gene substitution along the stretch o f the Sandveld is presumed.Intermediates between Pelargonium carnosum and P. polycephalum or P. adriaanii are on record, but such intermediates occur markedly less often than intermedi ates among the subspecies o f P. carnosum.Since numer ous morphological characteristics support the distinct ness o f their gene pools and as there are no indications o f interbreeding processes going beyond the F 1 generation, P. polycephalum and P. adriaanii continue to qualify as separate species.The position is completely different in the subspecies o f 'P.carnosum' and 'P.ferulaceum'.Large-scale hybridization as in the region o f Vredendal/ Clanwilliam demonstrate the absence o f effective repro ductive isolation mechanisms; P. ferulaceum is therefore reduced to the rank o f subspecies.There is evidence that P. carnosum subsp.ferulaceum is connected to P. parvi florum subsp.parviflorum via a full range o f intergrading forms in the area o f geographical overlap.In Becker & Albers (in press a) we will provide material that none theless supports the treatment o f P. parviflorum and near related taxa as a distinct complex.