Addresses:
*H. Lembcke, 2000 Hamburg 61, Gottschalkweg 33, Germany.
**Dr P. J. Weisser, previously: Facultad de Ciencias, Univ. de Chile, Santiago, Chile, now: Botanical Research In­stitute, Private Bag X1Ol, Pretoria, 0001, South Africa
+ Presented at SUCCULENTA 78

Abstract

Schematic distribution maps of twenty three genera for Chilean Cactaceae are given. A well delimited group of north-andean genera was found, which included Arequipa, Armatocereus, Browningia, Corryocactus, Haageocereus, Helianthocereus, Neowerdermannia, Opuntia, Oreocereus and Soehrensia. The genera Copiapoa, Eriosyce, Eulychnia, Neoporteria, Pyrrhocactus and Trichocereus are coastal in the northern part of their distribution area, but extend to the preandean and andean zone in the southern part. Islaya is present in Chile only near the coast close to the Peruvian border. Austrocylindropuntia is typical of the coastal area between latitudes 25^o and 30^o south and Thelocephala between the latitudes 26^o and 29^o south. Erdisia occurs in the Andes of Central Chile. Maihuenia is the southern most occurring genus of Cactaceae in Chile and can be found in the Andes and the Central Valley. Tephrocactus is one of the most widespread genus, having representatives along the coast as well as at high altitudes on the Andes, from the border with Peru to north of Santiago. Austrocactus has been found in the Andes of Central Chile.

This distribution pattern can be correlated with the topography and climatic conditions of the country. While the north-andean group gets its water mainly from summer rains, the coastal group is dependent mainly on fog and dew in their northern distribution areas. To the south, winter rain becomes more important.

Ecological factors controlling the distribution of the plants vary from one genus to the other, The drought in the Atacama Desert, the climatic conditions associated with high altitude (e,g. low temperature) on the Andes and competition by faster growing plants in areas with higher rainfall seem to be the main limiting ecological factors controlling the distribution pattern and the expansion of Chilean Cactaceae.

Introduction

The study of Chilean Cactaceae has been characterized by "species hunts“, which have led to the scientist becoming lost in the detail without achieving an overview. No attempt has previously been made to give an overall picture of the distribution pattern of the genera of this family in Chile. The objective of this paper is a start in this direction. lt is not envisaged to present precise and comprehensive distribution maps as such information is not available, but only to give some indications in sketch maps about the latitudinal-longitudinal distribution of cacti occurring in Chile.

The main difficulties encountered during our work lay in the extent of the country, the inaccessibility of some regions, and the instability of the Taxonomy of Cactaceae. This latest fact made it sometimes impossible to establish with certainty to which species reference was made in the literature or to which genus a quoted species should be allocated. The usual inadequate indication of the localities and the difficulty in getting the scattered literature together, made it an even more difficult task. All this led us to rely more on our own field records than on literature. The selection of genera for this paper was very problematic. This being a biogeographical contribution with no taxonomic pretensions, a pragmatic approach was adopted. The main conditions for inclusion of a genus were its recognisability in the field, together with its frequent appearance in the current literature. In relation to the taxonomy of the genera we consulted Britton and Rose (1920 & 1922), Looser (1929), Buxbaum (1964—), Lembcke (1969) and Backeberg (1970).

All the encountered difficulties made us realize that the material presented here is only a working base for future research and corrections and additions will be most welcome. We expect that when the results of the research done by F. Ritter (in prep.) become available, quite a number of refinements will be possible. Nevertheless, we are confident of having been able to detect the main distribution pattern of the cacti genera in Chile.

Topography

Chile is a long (4 200 km, without the Antarctic section), narrow, N-S oriented country and therefore ideally suited for phytogeographical studies. Apart from its considerable latitudinal extension, the presence of the Andes mountain range allows the development of a altitudinal zonation. The possibility of this interplay between latitudinal and altitudinal zonation is remarkable. The main topographical features of the country arc the presence of a coastal mountain range, of which some peaks surpass 2 000 m in altitude, the Andes, in some parts over 6,000 m, and between both, the Central Valley, sometimes replaced by a plateau or a series of transversal mountain ranges.

Climate

The latitudinal and altitudinal changes arc accompanied by climatic changes that contribute, together with historical, genetic, and topographical factors, to control the distribution areas of the plants.

In the northern part of the country the climate is arid except in the high lying areas near the border with Peru, Bolivia, and the Argentine. There, summer rains occur. The Atacama Desert (east of Antofagasta, Fig. 1) is considered to be the driest desert in the world. The aridity and the temperature fluctuations arc considerably mitigated near the coast, where coastal fogs and occasional dew occurring throughout the year, make the existence of vegetation possible. The situation is in some aspects similar to the Namib, as a cold sea current induces lower temperatures, high air humidity and fog. In places, where the coastal cordillera is high, it may act as a barrier to the fogs, impeding their penetration inland.

When advancing from the desert southward, occasional winter rains give rise to the phenomena of the flowering desert, especially on the plains between Vallenar and Copiapó. These winter rains, climatic element typical of the Mediterranean zone of Chile, increase in frequency and duration to the south. The Mediterranean climatic zone occupies the .central part of the country (Fig. 2, area Valparaiso). For more details on climate the biogeographical classification of Chile by F. di Castri (1968) can be consulted.

Biogeography

According to Diels (in Schubert 1966), the northern and central parts of Chile fall into the Neotropical, and the southern part into the Antarctic Plant Kingdom. Cactaceae is typical of the Neotropical Zone and their southern limits coincide.

Pisano‘s (1966) biogeographical classification of Chile places Cactaceae as occurring in the xeromorphic, mesomorphic and andean zone.

For more information related to general climatic and biogeographic background of Chile, the works by Reiche (1907 or 1934 & 1938), Schmithüsen (1956), Oberdorfer (1960), Mann (1964), Walter (1964 & 1968), Pisano (1966), and di Castri (1968) can be consulted. For descriptions of travels in search of Cactaceae in Chile the accounts of Lembckc (1958 & 1959), Buining (1971), and Schreier & Weisser (1974 & 1975) are recommended. Distribution maps of Cactaceae from Argentina are given in Castellanos & Lelong (1943) and additional information by Kiesling (1975).

Methods

A cartographic representation of the areas occupied by the different genera was originally drawn at a scale of 1: 6 000 000. In this work, reductions of the original maps are published. The areas obtained were then characterized, described and wherever possible interpreted. Because of the schematic nature of the maps the areas indicated should be considered only as gross approximations.

Results

1. AREQUIPA Br. & R.

The main distribution of this genus lies in South Peru. The areas that it occupies in Chile are indicated in Fig.1. lt is restricted to the northern Chilean Andes. The presence of populations between the two areas indicated on the map can be expected. The region has a high altitude climate with summer rains. Limiting factors could be the droughts to the west and too low temperatures to the east, owing to the increase in height of the Andes. Buxbaum (1973 b) does not acknowledge the validity of this genus and has incorporated it into Oreocereus.

2. ARMATOCEREUS Backbg.

Backeberg (1970) reports this genus to be distributed from Columbia to Peru. We found some populations in Chile (Fig.2), growing at high altitudes (around 3,000 m) in the northern part of the country near the border with Peru and Bolivia. Summer rains occur and a high altitude climate, with great daily variations in temperatures, high radiation and usually a low air humidity can be experienced here. The same limiting factors as with Arequipa could control this distribution area, i.e. drought to the west and cold temperatures to the east.

3. AUSTROCACTUS

On our field trips we were not able to find this genus. lt has been reported by F. Ritter to be in the Maule Valley, at 2,000 m, above "Mina Dolomita“ at a latitude of 360 south, which locality we have plotted in Fig1 (in Buxbaum, 1975).

4. AUSTROCYLINDROPUNTIA Backbg.

This genus is represented in Chile by only one species, A. miquelii (Monv.) Backbg. and was previously known as Opuntia miquelii Monv‘. (see Wagenknecht 1956). This cactus inhabits areas with a climate that is under coastal influence, with frequent fogs and occasional winter rains. To the south, the denser vegetation could be a controlling factor of its distribu­tion, while the presence of the Pacific Ocean constitutes a barrier to the west. Aridity could be a controlling factor to the east,

Kiesling (1975) reports this plant being present in Ecuador, Peru, Chile, Bolivia, Paraguay, Uruguay and the Argentine. This indicates its effective dispersion mechanisms. Its very hard greyish-white seeds, covered with an arillus (Weisser 1973) are noteworthy. Apart from seeds, it is possible that dispersion takes place through the breaking off of branches, with subsequent rooting.

5. BROWNINGIA Br. & R.

Browningia candelaris (Fig. 3) which also grows in Peru, is the only, very conspicuous species, of this genus in Chile.

 

Fig. 3 Browningia candelaris in the ,,Quebrada Cardones“ on the road between Arica and Chapiquina        <Photo Weisser)

lt is found in the northern Chilean Andes (Fig. 5) at altitudes above 2,300 m. Here it grows in a zone of high altitude climate with summer rains. Aridity is probably the limiting factor to the west while the ecological changes correlated to higher altitudes probably control the distribution to the east. In the distribution map information from Silva and Lira (1976) was incorporated.

6.COPIAPOA Br. & R.

The name of this genus was taken from the Chilean city or province of Copiapó (Fig. 1, left, lower corner) and it occurs only in Chile. In this genus we have included Pilocopiapoa solaris Ritt., whose correct name in our opinion should be Copiapoa conglomerata (Phil.) Lembcke (Lembcke 1966). Copiapoa (Fig. 4) has a wide latitudinal range along the coast and is represented by over 50 species (Bleck 1972). Plants of this genus grow from north of Antofagasta to the Limari River mouth (Muñoz & Pisano 1947) (Fig. 2). They mainly colonize the coastal mountains, adjacent plains and canyons that are under the influence of coastal fogs (called "camanchacas“ in Chile and "garüas“ in Peru). Depending on the coastal topography, the fog can be restricted to the immediate coast (e.g. Antofagasta) or penetrate deeply inland following canyons or surpassing lower peaks of the coastal mountain range (e.g. near Vallenar). Special topography and wind currents can result in some areas being par­ticularly frequently covered with fogs, resulting in what Follmann & Weisser (1966) called fog oases, which can support a relatively luxuriant vegetation, e.g. in Paposo (see Rundel & Mahu 1976).

The distribution of Copiapoa (Fig. 2) is coastal in its northern area, while it can penetrate deeper into the interior following valleys, from Copiapó southwards. For example, Copiapoa megarrhiza occurs in the mountain range near Copiapó.

In the Antofagasta area the distribution of this genus to the east seems to be controlled by aridity, to the west by the Pacific Ocean, to the north some arid stretches between fog oases could constitute an insurmountable barrier and in the south Copiapoa are probably limited by competition.

Distribution pattern may be affected directly or indirectly through biotic factors such as predation and diseases. lt could therefore be relevant that predation of flowers of Copiapoa by lizards has been reported (Weisser 1975) as well as myrmecory (predation?) (Speta 1967 and Weisser 1973).

Seeds found in the stomach of the seedsnipe Tninocorus ruminicivorus from the area of Vallenar by Prof. G. L. Maclean, were identified as belonging to this genus by Weisser. This could imply occasional predation or dispersion of seeds by birds.

 

Fig. 6 Erdisia sp., photograph taken in the Andes in a valley to the east of Santiago.   
(Photo Weisser)

7. CORRYOCACTUS Br. & R.

For the presence of this genus in Chile we rely on the information published by Wagenknecht (1956), who found Corryocactus brachypetalus in the area of Chusmiza (Fig. 8).

8. ERDISIA Br. & R.

Backeberg (1970) describes this genus as being distributed from the south of Peru to Chile and he recognizes eleven species. We have only found Erdisia (Fig. 6) in the Andes of Central Chile (Fig. 5). Wagenknecht (1956) quotes the possibility of L. Peña having found Erdisia in the high Andes cordillera inland of Antofagasta, near the Laskar Volcano. Buxbaum (1964) mentions valleys of North Chile above 2,000 m as habitat for Erdisia. The validity of this genus is not recognised by Buxbaum (1964) who includes Erdisia in Corryocactus.

9. ERIOSYCE Phil.

In this genus we have included Rodentiophila (Ritt.). Eriosyce (Fig. 7) has a wide and scattered distribution. Phytogeographically, one could consider two groups of Eriosyce varieties:

The coastal varieties, on the mountain range near the sea (up to about 600 m) and those of the interior on the pre-Andes and Andes at altitudes up to 2,300 m . A tentative distribution map is shown in Fig. 8.

Along the coast one can find Eriosyce from Antofagasta (very seldom) to the Limari river. The climate here is mild, arid to semi-arid, with occasional winter rain in the southern area of distribution and with abundant fog. Controlling the distribution is the Paciflc Ocean to the west, aridity to the north and east in the northern parts of the distribution area. Competition by faster growing vegetation could limit Eriosyce in the more southern localities.

The Andean varieties live in a harsher climate. In the upper distribution limits frost and occasional snowfalls may occur. Rains mainly in winter.

Fig. 7 Eriosyce ceratites, commonly named "sandillon“ on the road between Ovalle and Vicuña, with the accompanying Bromeliaceae of the genus Puya.    (Photo Weisser)

10. EULYCHNIA Phil.

The area where this genus grows is shown in Fig. 5. F. Ritter found plants of this genus on the Peruvian coast. In its northern distribution it is coastal bound and it can form impressive populations in fog oases such as La Chimba (near Antofagasta, Fig. 9) and Paposo (north of Tal-Tal).

The genus shows a wide latitudinal range, ex­tending from south of Arica (Ritter, in Backeberg 1970) to Los Molles (Eulychnia castanea) in Central Chile. While in the northern part of its distribution area it is represented by isolated populations in coastal localities with frequent fogs, it also penetrates deep into the interior at Copiapó, Vallenar, Coquimbo and Ovalle, giving the landscape a particular character with its candelabric growth form. Drops of water from fog condensed on Eulychnia spines are shown in Fig. 10.

Attitudinally it seems to cover the range of 0 to around 960 m. The distribution could be controlled in the north and east by aridity, to the west by the Pacific Ocean and in the south by competition.

11. HAAGEOCEREUS Backbg.

lt has not been found by us, but it was reported by Wagenknecht (1956) to be growing at 2 000 m in front of the hamlet of Mocha on a side road to Chusmiza, to the east of Iquique (Fig. 11). The species found by him was Haageocereus australis. Climatically it corresponds to a high altitude climate with occasional summer rains. Rauh quoted by Buxbaum (1973a) gives the altitudinal range as being 0-2,400 m in Peru.

12. HELIANTHOCEREUS Backbg.

Helianthocereus atacamensis (= H. pasacana) belongs to this genus and it is the most impressive of all the Chilean cacti (Figs. 12 and 13). lt is widely spread in the high Andes east of Calama and San Pedro de Atacama and its distribution stretches into Argentina and Bolivia (Fig. 2). The climate is a high altitude type, rains mainly in summer, Cabrera (1971) records H. pasacana as being frequent in the northern part of the phytogeographical province of the Prepuna (= "Provincia Prepuñena“) in the Andes of Argentina.

Some authors, e.g. Wagenknecht (1956), Cabrera (1971) and Muñoz (1973) consider H. atacamensis as belonging to the genus Trichocereus.

Fig. 12 Helian thocereus atacamensis near Toconoce. In the background, ran­sacked tombs of the ,,atacameños“ tribe.  (Photo Weisser)

Fig. 13 Flower of Helianthocereus atacamensis near Toconce. (Photo Weisser)

Fig. 14 Maihuenia poeppigii forming a low caespitose cushion on sandy soil in the vicinity of Charrua, at the latitude of Concepción. The large fruits are clearly visible. (Photo Weisser)

 13. ISLAYA Backbg.

We have not traced plants of this genus in Chile, but F. Ritter found them near Poconchile about 50 km east of Arica, the species being Islaya krainziana Ritt. (quoted in Kinzel 1968). lt can be assumed that the climate at Poconchile is influenced by the coastal proximity, with abundant fogs and very little rain (Fig. 1). Buxbaum (1973c) considers islaya krainziana as being a Neoporteria. If this criteria were followed, Islaya would not reach Chile.

14.  MAIHUENIA Phil.

The species of this genus (Fig. 14) occur mainly in the Andes in Central Chile, on both Chilean and Argentinian sides. lt can be considered to be the most primitive of all Chilean cacti and the seed morphology shows great similarities to that of Pereskia (Weisser 1973).

The approximate distribution is shown in Fig. 2. In its northern distribution area, the genus Maihuenia seems to be restricted to the Andes, whereas it enters the Central Valley at the latitude of Concepción. The southern limit in Chile seems to be in the vicinity of Lonquimay (Hollenmayer, quoted by Wagenknecht 1956).

15. NEOPORTERIA Br. & R.

Plants of Neoporteria are mainly distributed along the coast and on the coastal mountain range (,,Cordillera de la Costa““) and they seem to extend from south of Chanaral to the area around Copquecura, south of Constitución (Fig. 11). In its northern area it is limited to localities near the coast, while in Central Chile it reaches the longitude of Santiago.

Fig. 15 Pyrrhocactus sp from Paposo, north of Tal-Tal. 
(Photo Weisser)

 

Fig. 16 Pyrrhocactus chilensis (= Neochilenia chilensis) from the area of Pichidangui with ten open flowers.(Photo Lembcke)

In the north they gröw in zones under the influence of the coastal fogs. In the south, the fogs diminish progressively in their importance to hydric economy of the cacti, the winter rains increasing in importance instead. While in the northern zone the limiting factor seems to be climatic (e,g. drought) in the south competition by taller shrubs through outshading restricts this genus to more xeric, often stony habitats, such as coastal bluffs and mountain slopes exposed to the north.

For this work we used a more narrow concept of the genus Neoporteria than the one proposed by Buxbaum (1972). He includes Thelocephala, Neochilenia, Horridocactus and Pyrrhocactus in Neoporteria, while we accepted Thelocephala and Pyrrhocactus as valid.

16.  NEOWERDERMANNIA Fric. emend F. Buxbaum

This genus has not been found by us in Chile, but has been reported by Backeberg in the area of Ticnamar, near the Bolivian border at 3,500 m and by F. Ritter at 4,000 m (Buxbaum 1969). We have plotted the area Ticnamar near the Bolivian border on Fig. 8.

17. OREOCEREUS (Berg.) Ricc.

This genus is restricted to the Andes and its approximate area is shown in Fig. 11. Climatically this corresponds to a high altitude climate, with summer rains. A more extensive distribution is probable, the existence of populations between the two indicated areas is likely.

18. OPUNTIA

Most of the Opuntia appearing in the literature for Chile we have considered under Tephrocac­tus. Under Opuntia we have included plants with phyllocladia and we have found only one native species. Its approximate distribution is shown in Fig. 17. The distribution of the cultivated Opuntia sp. (common name "tuna“) has been excluded.

This genus seems to be restricted to the higher parts of the Andes near the Peruvian­Bolivian border.

19. PYRRHOCACTUS

In this genus we have included Horridocactus, Neochilenia and Pyrrhocactus sensu Backeberg, because the proposed generic differences are not always sufficient to distinguish plants in the field. Also, this group of genera present the same type of fruit and a similar general aspect (Lembcke 1969).

For the presence of this genus in the coastal area between Arica and north of Antofagasta in the form of some isolated populations, we rely on the discoveries of F. Ritter reported in the literature (Whiteley pers. comm. 1977). We have marked the area north of Antofagasta as a continuous band, but most probably extensive gaps exist between populations.

Pyrrhocactus (Fig. 15 & 16) can be found in Chile from Arica to the latitude of Talca and from sea level to around 2 200 m . In its northern section, this genus is exclusively coastal. At the latitude of Copiapó it reaches the Andes, where it can be found as far south as the latitude of Talca (Fig. 17). In the Chilean north, the plants are mainly dependent on fog, while to the south the winter rains are more important. Competition by faster growing plants can be limiting in the southern distribution areas. Snow and frost may occur in the higher range of its altitudinal distribution.

20. SOEHRENSIA Backbg.

Species of this columnar genus seem to be restricted in Chile to the northern Andes in the region to the interior of Calama (Fig. 5) at an altitude of about 3,500 m.

21. TEPHROCACTUS Lem. emend Backbg.

This genus is classified by some researchers as Opuntia (e.g. Wagenknecht 1956) and its species cover a wide range of habitats, at high altitude as well as in the coastal, fog influenced areas. High altitude species tend to have cushion forms while coastal forms grow in a less compact form. The southern limit seems to be the species growing at the Cuesta Chacabuco, while the northern species cross over the Peruvian and Bolivian borders. The distribution in the northern Andes probably extends further east and further south than we have indicated in Fig. 19. Representatives of Tephrocactus can be found on the coastal mountain chain the Andes and the area in-between. With a range from 0 to over 4,200 m, it seems to be the genus with the widest altitudinal range. The latitudinal range is also remarkable, from the interior of Arica to the Cuesta Chacabuco which is north of Santiago (about 2,000 km). The very efficient vegetative reproduction of some species through the breaking off (e.g. by goats and sheep) of plant sections and subsequent rooting could be related to this wide distribution. The area of Tephrocactus presents a great variety of climates, from desertic to Mediterranean, and from coastal to high altitude.

22. TRICHOCEREUS (Berg.) Ricc.

Together with Eulychnia this genus with its columnar growth gives its character to extensive stretches of Chilean landscape. The most conspicuous species of Central Chile is Trichocereus chilensis and is commonly called “quisco” (Fig. 18).

 

Fig. 18 Photograph of Trichocereus chilensis flower taken in the vicinity of Santiago. (Photo Weisser)

It frequently grows on the north exposed slopes of the coastal mountain range and Andes, as well as in some parts of Central Chile. In its northern area this genus is mainly coastal. penetrating further landwards from the latitude of La Serena southwards (Fig. 21). The southern limit of this genus seems to be at the latitude of Talca. This genus grows in a variety of climates, e.g. coastal with abundant fogs in the northern part of its distribution, and Mediterranean in Central Chile. Occasional frost and snowfalls may occur in the Andean valleys occupied by quiscos, e.g. east of Santiago. For additional information about this genus consult Rundel (1974).

23. THELOCEPHALA Y. Ito

This genus includes the cacti described by Ritter (1960) under Chileorebutia and consists usually of species that are cryptic and which present tap roots (see also Lembcke 1959 and Weisser 1967). They grow on the coastal range in the area under the influence of fogs their northern limit probably being about 30 km south of Tal­Tal and their southern limit south of Huasco (Fig.19). It is an exclusively coastal genus. Buxbaum (1972b) includes this genus in Neoporteria.

Conclusions

A pattern was found when comparing the distribution areas of the Chilean genera of Cactaceae. This spatial arrangement can be directly or indirectly correlated in most of the cases to climatic and edaphic conditions. Climate is chiefly dependent on latitude, topography and modification through the presence of the ocean and altitude. Desertifica­tion owing to human activities seems to have opened new habitats for cacti in some cases, e.g. Trichocereus in Central Chile. Four main distribution areas seem to exist. That with the most genera present is the Andean area of Chile bordering with Peru, Bolivia and the north of Argentina. There the following genera may be encountered: Arequipa, Armatocereus, Brown­ingia, Corryocactus, Soehrensia, Haageocereus, Helianthocereus, Neowerder­mannia, Oreocereus and Opuntia. Tephrocac­tus may be present in this zone, but it also oc­curs in other regions. The climate of this area is characterized by summer rains, that, depending on the place, can fluctuate between 50 and 400 mm . In the higher part frosts are frequent and the temperature changes between day and night are considerable.

The second group of genera is confined to areas under the influence of the frequent coastal fogs and includes the genera Copiapoa, Eulychnia, Islaya, Austrocylindropuntia and Thelocephala. Their distribution is mainly coastal, reaching the interior in places where the topography of the coastal mountains is low or cross valleys are present, allowing the fogs to penetrate deeply into the country (e.g. Copiapó, Huasco and Elqui valleys). The climate is mild, without frost or great variations in temperatures. Water is provided mainly by fogs, the occasional winter rains becoming more frequent to the south. Air humidity tends to be high and the incoming solar radiation is reduced by the frequent fogs. A detailed climatic description of the locality of Caldera, situated in this zone, is given by Weisser (1967).

A third group of genera also inhabits the fog area, but is able to colonize more extensive areas of the preandean, andean regions, as well as reaching farther south into the winter rain-fall region of Central Chile. To this a group of widely distributed genera belongs, such as Pyrrhocactus, Neoporteria, Trichocereus and Eriosyce. They occupy an extensive area with a wide range of ecological conditions that extends from maritime climate near the coast with fogs and sometimes winter rains, to mountain climate in the interior of the country. Some Pyrrhocactus, Trichocereus and Eriosyce species grow in places where frost and snowfalls may occur.

Present in the Andes of Central Chile is a fourth group formed by Erdisia, Austrocactus and Maihuenia, the latter mentioned growing also in the Central Valley on sandy soils. Maihuenia is the genus with the southernmost distribution on the Chilean side of the Andes, reaching the area of the Volcano Lonquimay.

What limits cacti in their expansion, in their natural tendency to colonize new areas? To the west, the Pacific Ocean is the distribution barrier. In the Atacama desert, the drought and in the Andes the climatic conditions associated with high altitude (e.g. low temperature) seem to be the most important factors controlling the distribution. In areas with higher rainfall, com­petition by faster growing plants seems to be decisive. lt could also be that some genera have not had enough time as yet to occupy the whole area they potentially could.

There is still a wide field open for the study of the geography of the Cactaceae in Chile. When an agreement on the validity of the genera has been reached, probably some of the presented distribution areas must be rearrang­ed. The opening of new roads will bring to light new localities and, maybe, new genera for Chile. lt will be a task for future research to refine and add to our findings, completing in this way the picture, which we have sketched in this work.

Acknowledgements

We would like to thank the Facultad de Ciencias, Universidad de Chile, Santiago, Chile, Mrs Melica Muñoz from the Museo Nacional de Historia Natural, Santiago, the Botanical Research Institute, Pretoria and Prof. Hugo Gunckel for help given and for allowing us to consult literature. We are thankful for the translation into the English language to Jacqueline Weisser. Valuable information was given by D. Whiteley (England) and we thank P. Vorster for his comments on the manuscript. We thank Miss M. Visser for drawing of the base map and Mrs A. Romanowski for her fine photographic work.

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