In this column we would like to report about interesting developments and results concerning our research activities.
A most interesting article was published in the September edition of Gymnocalycium:
Diers, Lothar: Zur Klärung von Verwandtschaftsbeziehungen durch experimentell-taxonomische Untersuchungen. Gymnocalycium 21(4)2008:809-814.
Diers reports well documented about his bi-generic crosses between Gymnocalycium and species/populations of Weingartia, Sulcorebutia, and Rebutia. His leading thought is the biological species concept, i.e. different parents that can interbreed successfully and produce fertile offspring are closely related. Diers evaluates the success of pollination, quality of seeds, qualitative and quantitative outcome of germination, development of the seedlings, their mortality rate, and their phenotypic imprinting by either female or male parent. The amount of data would allow establishing a scale from "not being related" to "closely related" with many increments between these extremes.
Diers concludes: "If one regards the seed production, the seed size, the germination and eventually the low number of survivable seedlings, then all of this is to be explained only by a substantial incompatibility of the partners. Thus a closer relationship between Gymnocalycium and the here examined other genera Weingartia, Sulcorebutia, Rebutia does not exist" (p814). Original text below.
"Betrachtet man den Samenansatz, die Samengröße, die Keimung und schließlich die geringe Zahl überlebensfähiger Sämlinge, so ist dies alles nur durch eine erhebliche Unverträglichkeit der Partner zu erklären. Damit ist eine engere Verwandtschaft zwischen Gymnocalycium und den hier überprüften anderen Gattungen Weingartia, Sulcorebutia, Rebutia nicht gegeben" (p814).
The results of our phylogenetic studies in 2005 and 2006 are confirmed by this well reproducible work.
By request of our German readers we have produced a research report about the results of our DNA sequence analysis in the SSK Project 2005 in German language. This report was submitted in October 2007 to the editorial office of Sukkulenten und andere Kakteen and published in June 2008. We regret that this article did not appear earlier.
Ritz C. M. & R. Mecklenburg. 2008: Die Phylogenie von Rebutia und ihrer Verwandten spiegelt die geologische Geschichte Südamerikas wider. Kakteen und andere Sukkulenten: 59(6):157-170.
This catch line is spooking through emails and internet forums since Hentzschel & Augustin had published the second part of their revision of the genus Weingartia in Gymnocalycium 21(2)2008Hentzschel G. & K. Augustin. 2008: Weingartia, Sulcorebutia und Cintia - eine untrennbare Einheit - Merkmalsvergleiche und Neukombinationen. Gymnocalycium 21(2): 767-782.. The authors united Weingartia, Sulcorebutia, and Cintia into one genus. As many experts before, they have been emphasising the morphological proximity between Weingartia and Sulcorebutia in the first part of their revision in 2002. Based upon our molecular data from 2005, we have confirmed their hypothesis in our research report: "Sulcorebutia and Weingartia should be united into one genus, because neither molecular nor morphological data reveal a distinction between these genera." (Ritz et al., 2007. American Journal of Botany 94(8): p1330.)
Already in 2006 the members of the SSK have contemplated uniting Weingartia, Sulcorebutia, and Cintia.
However, DNA sequence analyses did not sufficiently resolve the relationships within this expanded genus in order to come to a reliable conclusion. Therefore we decided to investigate the infrageneric relationships more deeply with the AFLP fingerprints.
Although Hentzschel & Augustin united Weingartia and Sulcorebutia in 2008, Hentzschel emended Sulcorebutia nine years ago (Hentzschel 1999Hentzschel, G. 1999: Het Geslacht Sulcorebutia Backeberg emend. Hentzschel. Succulenta 78(3):131-142.). Consequently Augustin, Gertel & Hentzschel authored the monograph Sulcorebutia that was published in 2000Augustin, K, W. Gertel & G. Hentzschel. 2000: Sulcorebutia. 4. Ed. Eugen Ulmer, Stuttgart. in German language. The authors advocate for a separation of Sulcorebutia from Weingartia mainly because the northern group of Weingartia differs from Sulcorebutia in "multiply branched funiculi", albeit southern Weingartia and Sulcorebutia have "single or simply branched funiculi". This latter fact and the retention of one genus for southern and northern Weingartia rendered the emendation of Sulcorebutia questionable.
The "multiply branched funiculi" are also discussed as argument for the common phylogenetic origin of Gymnocalycium, Weingartia, and Sulcorebutia. This hypothesis was refuted by Ritz et al. (2007).
Hentzschel & Augustin (2008Hentzschel G. & K. Augustin. 2008: Weingartia, Sulcorebutia und Cintia - eine untrennbare Einheit - Merkmalsvergleiche und Neukombinationen. Gymnocalycium 21(2): 767-782.) stated that "multiply branched funiculi" were misinterpreted by Hentzschel who corrected his error in 2001Hentzschel G. & K. Hentzschel. 2001: Sulcorebutia or Rebutia? Cactus and Succulent Journal Vol 73, No 5 Sept-Oct 2001. in the American Cactus and Succulent Journal. Unfortunately, most German-speaking cactus enthusiast and readers of the monograph Sulcorebutia were informed about this important fact seven years later.
In 2008 Hentzschel & Augustin reported that clear multiply branched funiculi as in Gymnocalycium have never been observed in Weingartia. Nevertheless they refer to the emendation of Sulcorebutia in 1999Hentzschel, G. 1999: Het Geslacht Sulcorebutia Backeberg emend. Hentzschel. Succulenta 78(3):131-142. and continue to contend that the species of Weingartia and Sulcorebutia are similar to each other in many characters. Furthermore, a large number of these characters occurred in various species of Gymnocalycium. On one hand this would point to a close relationship between Weingartia and Sulcorebutia and on the other hand to a close relationship of both to Gymnocalycium. While Weingartia has been brought in connection with Gymnocalycium by many authors, the assignment of Sulcorebutia to both genera has been rejected for a long time. Original text below.
"Es konnte gezeigt werden, dass die damals bekannten Weingartien und Sulcorebutien in sehr vielen Merkmalen übereinstimmen. Außerdem fiel auf, dass eine große Zahl dieser Merkmale auch bei verschiedenen Gymnocalycium-Arten auftreten, was auf eine enge verwandtschaftliche Beziehung zwischen Weingartia und Sulcorebutia einerseits und Gymnocalycium andererseits hinweist. Während Weingartia schon von mehreren Autoren mit Gymnocalycium in Verbindung gebracht wurde..., stieß der Gedanke, dass auch Sulcorebutia diesem Verwandtschaftskreis zuzuordnen sei, lange Zeit auf Ablehnung." Gymnocalycium 21(2):768.
This argumentation suggests that the authors maintain their hypothesis of a close relationship between Gymnocalycium, Weingartia, and Sulcorebutia.
The emphasis of the study by Hentzschel & Augustin (2008) is on hybridisation experiments. The authors claimed to have cross-pollinated all Weingartia species available at present with different species of Sulcorebutia. Almost all hybrids yielded viable seeds. Morphological features supplemented by hybridisation results would not allow maintaining two separated genera.
The authors recognised the research results of the SSK as follows:
"The recently published molecular-genetic studies by Ritz et al. confirm our observations of many years."
These long lasting observations are not specified in this context. Al least with regard to the assumed relationship of Gymnocalycium Hentzschel and Augustin drew a completely different conclusion than Ritz et al. (2007). Both studies come to the same result that Weingartia, Sulcorebutia and Cintia are better treated in one genus. The hybridisation experiments of Hentzschel & Augustin (2008) confirmed the molecular phylogeny.
However, we have a different opinion concerning the hurried re-combination of all Sulcorebutia and Cintia to a now unbelievable number of 73 (seventy-three) species and subspecies of Weingartia. If we follow the argument of the authors that the capability of different parents to interbreed and produce fertile offspring indicates close relationship and militates for the merging of three genera on one side then the nearly unexceptional success of hybridisation suggest at best only a few biological species on the other side.
For this reason we continue to follow the hitherto applied taxonomy until our present AFLP-project is completed.
Hentzschel, G. 1999: Het Geslacht Sulcorebutia Backeberg emend. Hentzschel. Succulenta 78(3):131-142.
Augustin, K, W. Gertel & G. Hentzschel. 2000: Sulcorebutia. 4. Ed. Eugen Ulmer, Stuttgart.
Hentzschel G. & K. Hentzschel. 2001: Sulcorebutia or Rebutia? Cactus and Succulent Journal Vol 73, No 5 Sept-Oct 2001.
Augustin K. & G. Hentzschel. 2002: Die Gattung Weingartia Werdermann -Teil 1: Besprechung und Neuordnung. Gymnocalycium 15(3): 453-472.
Ritz C. M., L. Martins, R. Mecklenburg, V. Goremykin, F. H. Hellwig. 2007: The Molecular Phylogeny of Rebutia (Cactaceae) and its Allies Demonstrates the Influence of Paleogeography on the Evolution of South American Mountain Cacti. American Journal of Botany 94(8): 1321-1332.
Hentzschel G. & K. Augustin. 2008: Weingartia, Sulcorebutia und Cintia - eine untrennbare Einheit - Merkmalsvergleiche und Neukombinationen. Gymnocalycium 21(2): 767-782.
Ritz C. M. & R. Mecklenburg. 2008: Die Phylogenie von Rebutia und ihrer Verwandten spiegelt die geologische Geschichte Südamerikas wider. Kakteen und andere Sukkulenten: 59(6):157-170.
The following progress report was presented at a poster on the congress of the German Botanical Society (Deutsche Botanische Gesellschaft) in September 2007 in Hamburg:
"Phylogenetic relationships within the Cintia-Sulcorebutia-Weingartia-complex"
(Christiane M. Ritz, Carsten Löser, Rainer Mecklenburg und Frank. H. Hellwig)
Globular Andean cacti fascinate cactus breeders, because of their great diversity and especially the remarkable differences in flower colour. This great attention of collectors resulted in a notoriously difficult taxonomy and in an inflated numbers of synonyms. Previous studies demonstrated that the rigorous lumping of many genera in Rebutia s.l. is not supported by molecular data. The genera Cintia, Sulcorebutia and Weingartia constitute a well-supported monophyletic clade, which is clearly separated from Rebutia s.s. This clade is well characterized by hairless pericarpels with persistent auriculate scales as opposed to the deciduous acute triangular scales characteristic for Rebutia. We investigated the phylogenetic relationships within the Cintia-Sulcorebutia-Weingartia complex employing sequences of the trnS-trnG intergenic spacer of the chloroplast DNA and data from AFLP fingerprinting. Several morphological characters, e.g. the adherence of the fruits, the shape of the areoles and the branching of the funiculi are usually cited to distinguish Sulcorebutia from Weingartia. However, transitions between these characters are gradual. Molecular data do not support the separation of Sulcorebutia and Weingartia but the phylogeny reflects the geographic distribution of the species."
It is an important result of our DNA sequence analysis during the SSK project 2005 that Weingartia and Gymnocalycium are not closely related. We presented this finding on the 29th Congress of the IOS in September 2006 in Zürich. It was confirmed by AFLP fingerprinting in 2006 and published in the American Journal of Botany in August 2007 (Ritz et al, 2007). Gymnocalycium specialists cast doubt on this outcome. Scepticism was put forward in particular from the Austrian Arbeitsgruppe Gymnocalycium since there are ambitions to move Weingartia to Gymnocalycium.
The taxonomical classification for Weingartia has been debated for a long time. In 1993, Barthlott & Hunt included Weingartia as part of the genus Rebutia in Trichocereeae, but this was proven to be wrong by our projects 2005 and 2006.
Many authors presume a close relationship of Weingartia and Gymnocalycium because both genera have hairless, scaly pericarpels, e.g. Hutchison (1957), Endler & Buxbaum (1974), Backeberg (1977), Ritter (1980), Hentzschel (1999) and Augustin & Hentzschel (2002). According to Augustin & Hentzschel, Gymnocalycium, Weingartia, and Sulcorebutia have a common phylogenetic origin because all traits characterising Weingartia and Sulcorebutia also occur in some Gymnocalycium species (Gymnocalycium 15(3)2002, p453). Our molecular data from 2005 clearly refute this hypothesis because Gymnocalycium is sister of various genera in Trichocereeae with hairy or bristly pericarpels, and thus the similarities of Gymnocalycium and Weingartia are originated by convergent evolution. Additionally, our data do not support the classification of Gymnocalycium based on seed morphology (Till 2001).
After publication of our report in the American Journal of Botany we gladly observe that the Arbeitsgruppe Gymnocalycium has decided to compile a molecular phylogeny of Gymnocalycium in 2008 at the University of Vienna. This "framework" would be necessary to interpret distribution patterns and character evolution within the genus correctly. Thus also the species concept cold be re-defined and existing conceptions supported or disproved. (Gymnocalycium 20(3)2007, S.XII)
Study Community of South American Cacti
© 2007-10 · I.A. Mecklenburg
Last update: 14 August 2010
These pages are displayed in an optimal way with Firefox or Opera.