Abstract
Polymorphism in a population of the desmid (Zygnemaphyceae) Cosmarium abbreviatum Raciborski var. minus (West & West) Krieger & Gerloff is reported from material collected from 3 stations at the Lily Pond located in the Parque Estadual das Fontes do Ipiranga, São Paulo City, southern Brazil. From the examination of approximately 200 plants, 6 different morphological expressions were described and the following remarks made: 1) a detailed analysis of sample populations is absolutely necessary for the definition of species and infraspecific categories among desmids; 2) the morphological characteristics presently used for the delimitation of certain species, which are built up of individuals of very small size, seem to have no great taxonomical significance when only isolated individuals are analysed; and 3) taxa, such as Cosmarium angulosum Bréb. var. angulosum f. angulosum, C. abbreviatum Rac. var. minus (West & West) Krieg. & Gerl., C. succisum G.S. West var. jaoi Krieg. & Gerl., C. tinctum Ralfs var. tinctum, and C. minimum West & West var. minimum are of doubtful validity and may prove to be merely polymorphic expressions of C. abbreviatum var. minus.
Cosmarium abbreviatum var. minus; polymorphism; synonymy; Zygnemaphyceae; Cosmarium abbreviatum var. minus; desmídia; polimorfismo; sinonimia; Zygnemaphyceae
ARTICLES
Polymorphism in the desmid Cosmarium abbreviatum var. minus (Zygnemaphyceae) and its taxonomic implications
Polimorfismo na desmidiácea Cosmarium abbreviatum var. minus (Zygnemaphyceae) e suas implicações taxonômicas
Carlos E. de M. Bicudo
Phycology Section, Instituto de Botânica, Caixa Postal 4005 - 01051 - São Paulo-SP - Brasil
ABSTRACT
Polymorphism in a population of the desmid (Zygnemaphyceae) Cosmarium abbreviatum Raciborski var. minus (West & West) Krieger & Gerloff is reported from material collected from 3 stations at the Lily Pond located in the Parque Estadual das Fontes do Ipiranga, São Paulo City, southern Brazil. From the examination of approximately 200 plants, 6 different morphological expressions were described and the following remarks made: 1) a detailed analysis of sample populations is absolutely necessary for the definition of species and infraspecific categories among desmids; 2) the morphological characteristics presently used for the delimitation of certain species, which are built up of individuals of very small size, seem to have no great taxonomical significance when only isolated individuals are analysed; and 3) taxa, such as Cosmarium angulosum Bréb. var. angulosum f. angulosum, C. abbreviatum Rac. var. minus (West & West) Krieg. & Gerl., C. succisum G.S. West var. jaoi Krieg. & Gerl., C. tinctum Ralfs var. tinctum, and C. minimum West & West var. minimum are of doubtful validity and may prove to be merely polymorphic expressions of C. abbreviatum var. minus.
Key words: Cosmarium abbreviatum var. minus; desmid; polymorphism; synonymy; Zygnemaphyceae.
RESUMO
Relata-se um caso de polimorfismo na alga desmidiácea (Zygnemaphyceae) Cosmarium abbreviatum Raciborski var. minus (West & West) Krieger & Gerloff. O material foi coletado de três estações distintas no Lago das Ninféias, que se situa no Parque Estadual das Fontes do Ipiranga, cidade de São Paulo, Brasil. O exame criterioso de aproximadamente 200 indivíduos permitiu relacionar e descrever seis expressões morfológicas e fazer as seguintes observações: 1) para delimitação de especie e de táxons infra-específicos em desmídias, é absolutamente necessária a análise de amostras populacionais; 2) as características morfológicas atualmente utilizadas na delimitação de certas espécies constituídas de indivíduos de pequeno porte parecem não ter valor taxonômico quando apenas indivíduos isolados são examinados; e 3) devem-se tratar com cautela táxons como: Cosmarium angulosum Brébisson var. angulosum f. angulosum, C. abbreviatum Raciborski var. minus (West & West) Krieger & Gerloff, C. succisum G.S. West var. jaoi Krieger & Gerloff, C. tinctum Ralfs var. tinctum e C. minimum West & West var. minimum, até que novos estudos confirmem o presente, visto poderem ser apenas expressões morfológicas de C. abbreviatum var. minus.
Palavras-chave: Cosmarium abbreviatum var. minus; desmídia; polimorfismo; sinonimia; Zygnemaphyceae.
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Acknowledgement
The author thanks Mr. Alasdair G. Burman for revision of the English text.
Bibliographic references
Received: Aug. 5, 1987.
Accepted: Oct. 20, 1987.
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- WEST, W. & WEST, G.S. 1900. The algal-flora of Yorkshire, a complete account of the know freshwater algae of the Country, with many notes on their affinities and distribution. Trans. Yorks. Nat. Un., Leeds, 5(22): 1-52; (23): 53-100; (25): 101-164; (27): 165-239.
Publication Dates
-
Publication in this collection
17 June 2011 -
Date of issue
Dec 1988
History
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Accepted
20 Oct 1987 -
Received
05 Aug 1987
