HOOCK, H. 1993 . Kakt. and. Sukk. Band: 44 Heft (2) Seite 37-44 Ist Astrophytum coahuilense (MOELLER) KAYSER ein Naturhybrid?
German version German version

Is Astrophytum coahuilense (Möller) KAYSER a natural hybrid?

1. Historical review

Rudolf MEYER, a respected cactus collector at his time, mentioned in 1911 in the German monthly cactus news for the first time "Astrophytum myriostigma" (LEM.) with red colored flower throats. They were under an import shipment from Mexico which just had reached the gardener GRÄSSNER in Perleberg. We know today that this must have been Astrophytum coahuilense. Unfortunately, the article of MEYER remained unnoticed so that 16 years still passed up to the first description of the plants (table 1).

The discovery of these beautiful Astrophytums has to be owed to Dr. Carl PURPUS who collected these plants already in 1904 on his journeys through Coahuila in Mexico beside many other interesting succulents. At his often adventurous, lonesome raids he had found the "white" form of Astrophytum myriostigma at the Cerro Bola and nearby Torreon. He and his literarily active brother of Josef Anton distinguished it from the "green" form from the far remote San Luis Potosi, known since 1839, by the extreme thick flakes on the epidermis which give it the typically white appearance. In different impressive location descriptions they emphasize again and again the unbelievably perfect visual adaptation of the "coahuile Myriostigmas" to their surroundings. They are practically not distinguishable from the lime rock of her native country in form and color. However, obviously neither Carl nor his brother Josef Anton knew the important facts through what they are different from the GALEOTTI-Myriostigmas so unmistakably: the red throated flower and the red, seed rich fruit with the bottom opening.

Heinrich MÖLLER, an also known Astrophytum specialist of the 20- years, by informative intersection trials stated that the "green" and "white" Myriostigmas do not fertilize mutually. Although all other essential differences were also known to him apart from the sterility he decided merely on the mounting of a sub variety in his first description in 1927. He names the white bishop's cap "Echinocactus myriostigma subspecies coahuilensis". Konrad KAYSER, nephew of the famous Czech field researcher A.V. FRIC 1932 ventured the decisive step. He combined the PURPUS find to a stand-alone species and described it like its native country as "Astrophytum koahuilense". This opinion is very controversial since then. Although experienced experts in the genus with further arguments supported it later (M. MEGATA, 1944; table 3), the consent is still very different. Today, many authors primarily in the English linguistic area still represent for the opinion, that Astrophytum coahuilense is merely a variety or really only a form of the "green" Myriostigmas discovered by GALEOTTI (table 2). Why is this so?

2. The species problem at the example of Astrophytum coahuilense

In biology there are few concepts which were discussed so intensely as the one of the species. One can say without going into these difficulties more nearly that the majority of the scientists is representing a definition at present according to Ernst MAYR. After this a species is a natural propagation community which differs of others by constant, hereditary characteristics and which is isolated reproductively (MAYR, E. 1942, 1982). Let us have a try at the example of Astrophytum coahuilense using this set appearing a little theoretical at first in the practice.

The coahuile bishop's caps settle fields in the southwestern Coahuila partly also peripheries of the adjacent states of Durango and Zacatecas. Their main distribution lies in the Sierra Baicuco, the Sierra Parras but also something southern in the Sierra of El Numero. Completely intact populations are found in this areas with plants at every age, so that the first condition of the species definition of a "natural propagation community" is filled.

Astrophytum coahuilense has in its outer, spine-less form and generally with the five ribs a surprising similarity to Astrophytum myriostigma. However, it is different in all characteristics regarding flower, fruit, seed and embryo which are borrowed in all details from Astrophytum capricorne (DIETR.) BR. & R. Their areas reach in Coahuila far into the Sierra de Parras and Sierra Baicuco so that intersections also occur with the fields of the Coahuilenses. The differences into flower, fruit, seed and embryo mentioned by MÖLLER/KAYSER are constant, hereditary suffices in any case to distinguish Astrophytum coahuilense in nature or in the culture without problems from Astrophytum myriostigma.

The question only remains open if we find in nature descendants between the "white" and "green" Myriostigmen or if they are "isolated reproductively." It can be answered easily. Between the most northern area of the Myriostigmas at Jaumave in Tamaulipas and the most southern populations of the Coahuilenses in the three country horizontal bar Coahuila/Durango/Zacatecas lies for pollinators an invincible geographical distance of over 350 kilometers of beeline. However, in addition a biological propagation barrier exists. Astrophytum coahuilense and Astrophytum myriostigma have, when cross-pollinated, neither fruit approach nor seed: they are sterile by each other.

3. The origin of Astrophytum coahuilense

Neither the agreement of the two bishop's caps in her outer form, still the one into flower, fruit, seed and embryo between Astrophytum coahuilense und Astrophytum capricorne by parallel development lines are explicable. It is obvious that the Coahuilense has to be regarded as a descendant from natural hybrids between pure yellow flowering "ancestor" Myriostigmas and red throated "ancestor" Capricornes. It has characteristics from the two Astrophytum groups and its native country is on the southern margin of the Capricorne areas neighboring to the Myriostigma habitats.

The sterility of the Coahuilense opposite the Myriostigmas and the partial sterility to Astrophytum capricorne v. senile (FRIC) OKUM., his common partner in today's area, is more a proof of the narrow relationship than against it. An intersection barrier between nature hybrids and her output forms can be found very frequent in botany. It makes the demarcation possible first for the new speciation in many cases. The mixing populations would get back itself fast to one single propagation community without it. We possibly owe mainly the existence of Astrophytum coahuilense to his sterility after the process of hybridization.

So much the flower of the "white" bishop's caps originates from the Astrophytum capricorne complex in her details an interesting and informative difference is nevertheless in the order of the filaments. Two groups can clearly be distinguished here how they have only Astrophytum myriostigma and Astrophytum ornatum (DC.) WEB. The length of the flower axis takes a middle position between Astrophytum myriostigma and Astrophytum capricorne. This can be a direct result of the intersection process however, a gradual evolutiv diminution of the flower length is more probable caused by the cessation of the spines at the hybrids.

Nature hybrids can be often recognized by the multiplied set of chromosomes. This effect confessed as polyploidy is proved repeatedly in the family of the cactuses at Opuntias. In the genus Astrophytum have Astrophytum asterias (ZUCC.) LEM., Astrophytum capricorne, Astrophytum ornatum und Astrophytum myriostigma the simple sets of chromosomes (2n = 22). Till now, unfortunately, Astrophytum coahuilense wasn't examined in this regard. If it would be poyploid this would be a further important reference to his hybrid origin.

4. The evolution of Astrophytum

During ice-age climate fluctuations in the last earth-epochs the complete middle-American flora was tied into multiple north-south or south-north movements (figure 1). The precursors of the Astrophytums divided presumable early into a south complex equipped with conservative characteristics and a higher evolved group in the north in which the Coahuila mountain chains of the Sierra Madre Oriental caused a decisive separating function (figure 2). At a later turning back of the wandering movement obviously both plant communities met in today's south Coahuila again. The historical development difference between these populations must have been considerably lower than today at this time. A hybridization and with that the birth of the Astrophytum coahuilense was possibly (figure 3).

Course of continual climate deterioration subsequently the Myriostigmen retired on the fields confessed today to the south - a large Astrophytum-free distance between them and the Coahuilense area arose (figure 4). Perhaps unknown refuges of these plants still wait for their discovery in the rough area of the northeastern Zacatecas, however?

5. Summary

Is Astrophytum coahuilense as a stand-alone species justifiable or are these plants merely form/variety of the Astrophytum myriostigma? This question has been discussed again and again since the discovery of the "white" Myriostigmas in Coahuila. It had to be answered difficultly because of the similarity of the two taxa, but also in the agreement in flower, fruit, seed, and embryo of Astrophytum coahuilense with Astrophytum capricorne exclude a parallel development within the same genus as an explanation. They speak rather for a very narrow relationship both to the Myriostigmas as well as to the Capricorne complex (table 4).

All facts indicate that Astrophytum coahuilense occurred through a natural intersection between a higher evolved Astrophytum group in the north and an even more original Astrophytum south-group. During ice-age conditional flora walks after an area-isolation they met again in height of today's Sierra Baicuco/Parras. The sterility entered by the hybridization of the Astrophytum coahuilense facilitated a own development and the result satisfies all modern scientific criteria to the recognition as a stand-alone species.

Texts to the diagrams and figures

Figure 1:
One can approximately accept the origin of the genus Astrophytum in the area of the southern, Mexican highland. The species is there today with Astrophytum ornatum which one still has the most original characteristics.

Figure 2:
An early area dividing of the Astrophytum population has presumably occurred by ice-age flora walks. The north group equipped with more modern attributes arose to the north of today's Sierra de Parras, while within the more conservative south group by rib diminution, small growth and spine loss the Myriostigmas developed.

Figure 3:

The climate caused, turning back of the flora movement direction at a later time, the meeting of the north and south Astrophytums in height of today's Sierra Baicuco/Sierra Parras. By intersection between the ancestors of today's Capricorne and Myriostigma resulted the nature hybrid Astrophytum coahuilense.

Figure 4:
Today's geographical distribution of the genus Astrophytum is represented simplified. Only Astrophytum asterias could break through the barrier Sierra Madre Oriental on a detour via the Rio Grande area. On its long way which led it to the north Myriostigmas down to the geographical height again in the end. It has reached the most developed characteristics of all Astrophytums

Figure 5:
The presumable evolutiv development of the genus Astrophytum is represented here schematically as a temporal sequence and difference of the characteristics. Only the lines living today are shown. The geographical development steps concerning figure 1 to 4 are labeled.

Illustration:
Astrophytum coahuilense is almost like the Astrophytum myriostigma completely in the outer shape. But the red-throated flower, an intensively purple color, seed-rich fruit and the opening of the seed capsule at the base come from the characteristics of Astrophytum capricorne. Also the green embryos which after a successful seed dispersal are characteristic with their reduced cotyledons and succulent shoot axis for the Capricorne type.

Abbreviations:
Astrophytum asterias = AS, Asterias
Astrophytum capricorne = CA, Capricorne (Type)
Astrophytum capricorne v. aureum = CAE, Aureum
Astrophytum capricorne v. minor = CAI, Minor
Astrophytum capricorne v. niveum = CAN, Niveum
Astrophytum capricorne v. senile = CAS, Senile
Astrophytum coahuilense = CO, Coahuilense
Astrophytum myriostigma = MY, Myriostigma, Potosinum
Astrophytum myriostigma v. columnare = MYC, Columnare
Astrophytum myriostigma ssp. tamaulipense = MYJ, Jaumave
Astrophytum myriostigma ssp. tulense = MYL, Tulense
Astrophytum ornatum = OR, Ornatum (Type)
Astrophytum ornatum v. mirbelii = ORE, Mirbelii

Literature (statement):

Anonym (1903): Die Reisen des Sammlers C.A. PURPUS in Mexiko im Jahre 1903, Die Gartenwelt VIII (32): 378-380

BRAVO-HOLLIS, H. (1958): Notas Acerca de una Gira Cactologica, Cact. Suc. Mex. 3 (3): 63-67

BRITTON, N. L.; ROSE, J. N. (1937): The Cactaceae - Descriptions and Illustrations of Plants of the Cactus Family, Carnegie Inst. of Washington: 182-185

FLORES, R. E. (1944): From Mexico, Cact. Succ. Journ. (US) 16 (7): 98-99

GLASS, C.; FOSTER, R. (1974): Strange Bedfellows, Cact. Succ. Journ. (US) 46 (3): 112

GOLD, D. B. (1965): Las Cactaceas del Estado de Coahuila, Cact. Suc. Mex. 10 (4): 102-104

KAYSER, K. (1932): Astrophytum myriostigma subspecies Tulense, Der Kakteenfreund 1 (6): 57-59

KRÄHENBÜHL, F. (1975): Eine besondere Bischofsmütze: Astrophytum coahuilense (MOELLER) KAYSER, Kakt. and. Sukk. 26 (9): 206-209

MAYR, E. (1942): Systematics and the Origin of Species, Columbia University Press, New York

MAYR, E. (1982): The Growth of Biological Thought, The Belknap Press of Harvard University Press, Cambridge, Massachusetts

MEGATA, M. (1944): An Account of the Genus Astrophytum LEMAIRE in: Memoirs of the College of Agriculture, No. 56, Kyoto Imperial University: 1-62

MEYER, R. (1911): Über Echinocactus myriostigma S.-D. und Echinocactus asterias ZUCC., Monatsschrift f. Kakteenkunde 21 (6): 89-91

MÖLLER, A. F. (1930): Astrophytum myriostigma, Cact. Succ. Journ. (US) 1 (8): 156-157

MÖLLER, H. (1927): Beobachtungen an Astrophyten, Zeitschrift f. Sukkulentenkunde 3 (3): 52-55

OCHOTERENA, I. (1922): Las Cactaceas de Mexico, Universidad Nacional Autonoma de Mexico: 110-113

PURPUS, J. A. (1911): Standorte und Standortverhältnisse einiger Kakteen, Monatsschrift f. Kakteenkunde 21 (6): 82-86

PURPUS, J. A. (1914): Mimikry bei Kakteen, Möllers Deutsche Gärtner-Zeitung Jg. 29 (8): 89-91

VIERECK, H. W. (1939): Astrophyten, wie sie der Sammler in den Heimatgebieten sieht, Beiträge z. Sukkulentenkunde Jg. 1939 (1): 4-8

Table 1
Historical data about Astrophytum coahuilense (MÖLL.) KAYS.

1911 J.A. PURPUS reports about discoveries in Mexico of his brother Carl in the “Monatsschrift für Kakteenkunde” backdating partly to the year 1904. He found a "white" form of the bishop's cap, beside many other new succulents in Coahuila, whose "green" variant is known from the state San Luis Potosi already since 1839.

1911 R. MEYER describes red-throated flowering Myriostigmas in the same periodical like J. A. PURPUS from the collection GRÄSSNER, Perleberg.

1922 OCHOTERENA mentions a Myriostigma which shall grow at Monterrey. This only can be the coahuile bishop's cap. However, no collector has found it there ever.

1927 Intersection trials by H. MÖLLER between the two forms of the bishop's caps fail. He describes the form from the north as Echinocactus myriostigma subsp. coahuilensis, because flowers, fruit and seedlings differ essential of the form in San Luis Potosi.

1932 Recombination of the subspecies to the species of "Astrophytum coahuilense" by K. KAYSER, published in the periodical "Der Kakteenfreund".

1944 MEGATA repeated the intersection trials of the predecessors and regards the Coahuilense as an own species which he intended to name later as Astrophytum albissimum.

1974 C. GLASS & R. FOSTER confirm the statement of Carl PURPUS by a location photo that north of Viesca Astrophytum coahuilense and Astrophytum capricorne v. senile live in common areas. (the authors quote Astrophytum myriostigma v. coahuilense and Astrophytum capricorne v. minor).

Table 2
Taxonomic treatment of Astrophytum coahuilense in the past
Year author language taxon comment/quotations

1903 Anonym de MY "...Coahuila...wächst hier...MY..."
1911 PURPUS, J.A. de MY (grauweiße Form von MY)
1911 MEYER, R. de MY "...Blumen...mit scharlachfarbigem Grun de..."
1922 OCHOTERENA, I me MY "...MY, conocido en Monterrey..."
1925 FRIC, A. V. ts MY "...Villa Lerdo, Monterrey..."
1925 ROST, E. C. en MY "...MY...die graue oder weißliche Form aus Coahuila..."
1927 MÖLLER, H. de MY (Erstbeschreibung als Subspecies)
1929 BERGER, A. de MY "...subspec. coahuilensis..."
1930 MÖLLER, A.F. de MY "...Astrophytum myriostigma v. coahuilensis..."
1932 KAYSER, K. de CO (Erstbeschreibung als Art)
1933 TSUDA, M. ja MY "...Astrophytum myriostigma f. coahuilense..."
1935 OKUMURA, Y. ja MY "...Astrophytum myriostigma subsp. coahuilense..."
1935 KREUZINGER, K. de CO (unter der Sektion II bei Capricorne)
1937 BRITTON, N.L. & en MY "...grayish-white form..."
1937 BACKEBERG, C. de CO "...Astrophytum coahuilense..."
1937 WERDERMANN, E. & de MY "...Astrophytum myriostigma subsp. coahuilense..."
1939 VIERECK, H.W.* de MY "...Varietät(?)..."
1941 MARSHALL, W.T & en MY "...Astrophytum myriostigma v. coahuilensis...(MÖLLER, A.)..."
1944 MEGATA, M. ja CO "...Astrophytum coahuilense..."
1944 GILKEY, I.E. en MY " Astrophytum myriostigma v. coahui lensis..."
1951 BORG, J. en MY "...Astrophytum myriostigma v. coahui lensis..."
1958 BRAVO-HOLLIS, H. me MY "...entre La Paila y La Cuchilla collectamos...MY..."
1960 FEARN, P. en MY "...Astrophytum myriostigma v. coahui lensis..."
1962 KRAINZ, H. de MY "...MY in einer hochwüchsigen Art in S-Coahuila..."
1965 GOLD, D. B. me MY "...MY (Coahuila)..."
1967 SUAREZ, V. M. me MY "...Birrete de obispo (Coahuila), MY..."
1974 GLASS, C. & en MY "...Astrophytum myriostigma v. coahuilense..."
1979 HIRAO, H. ja CO "...Astrophytum coahuilense..."
1979 SADOVSKY, O. & ts CO "...Astrophytum coahuilense..."
1980 LAU, B. me CO "...Astrophytum coahuilense...Bahio de Ahuichila..."
1981 ITO, Y. ja MY "...Astrophytum myriostigma v. coahui lense..."

S: linguistic area (de = German; en = English; me = Mexican; ja = Japanese; ts = Czech)
CO/MY = Classification of Astrophytum coahuilense by the quoted author as: CO: Astrophytum coahuilense (own species); MY: Astrophytum myriostigma (or subspecies, variety, form)
Comment/quotations: "..." nomenclature or taxonomy used by the author in the original text
() Remarks by the author

Table 4
Stunted pollen forms in the genus Astrophytum (investigated by Megata)
------------------------------------------------------------------------
Taxon/number of plants/number flowers /stunted pollen (%)
------------------------------------------------------------------------
OR / 1 / 1 / 4,62

MY / 13 / 17 / 12,79 + 7,52

CO / 3 / 3 / 14,17 + 6,13

CA / 6 / 6 / 10,00 + 6,29

AS / 7 / 10 / 10,00 + 5,12

Hybrids:

OR X MY / 2 / 2 / 14,17 + 4,25

MY X AS / 4 / 5 / 52,50 + 4,74

CO X AS / 3 / 4 / 33,75 + 7,39

CA X AS / 12 / 18 / 27,64 + 9,07

------------------------------------------------------------------------

At hybrids, one frequently find more damaged pollen grains than at the parents plants. Astrophytum coahuilense lies above the values of Astrophytum myriostigma and Astrophytum capricorne. It is definitely possible that this fact is caused by the process of the natural hybridization between the two species although the extent of the material on hand doesn't allow a statistically protected statement. (all data from MEGATA, M. 1944, p. 28)

Table 3
Homologous characteristics of the nature hybrid Astrophytum coahuilense with today's Myriostigmas and Capricornes
------------------------------------------------------------------------
Myriostigma Coahuilense Capricorne
(Jaumave) (Cerro Bola) (Parras)
------------------------------------------------------------------------
Rib number from till: (3-9) (5-8) 8
flakes in the new shoot: white white brown
Flower axis: approx. 5-9 mm approx. 13-17 mm approx. 25-30 mm
Flower middle: yellow red red
Nectar chamber seal: pressure stamen stamen
Fruit color: green red red
Fruit opening: above below below
Seed number of the fruit: (30-100) (140-180) (110-220)
------------------------------------------------------------------------

Figures:

Astrophytum coahuilense, flower and fruit
figure 1 and figure 2
table 3
figure 3 and figure 4
table 4
evolution of Astrophytum, diagram

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