Phenotypic variability confirmed by nuclear ribosomal DNA suggests a possible natural hybrid zone of Triatoma brasiliensis species complex

The genusThlaspi L. s.l. comprises numerous segregate lineages, which have been recognized as single genera. One of these, Microthlaspi, represents one such segregate. It consists of morphologically similar annual species. The species have different ploidy levels (2x, 4x, 6x) and are usually summarized under the designation Thlaspi perfoliatum agg. The assumed ancestral diploid members of the species complex, Microthlaspi granatense (Boiss. & Reut.) F.K. Meyer, Microthlaspi umbellatum (Steven ex DC.) F.K. Meyer, and Microthlaspi natolicum (Boiss.) F.K. Meyer, are restricted to northwestern Africa, southeastern Spain and Turkey, northern Iran, and Lebanon. Microthlaspi perfoliatum (L.) F.K. Meyer is widely distributed all over Europe and shows three ploidy levels. Diploid M. perfoliatum is restricted to Middle Europe, whereas tetraploid and hexaploid M. perfoliatum are distributed all over Europe. Individual plants from 125 natural populations throughout the geographic range were analysed using chloroplast DNA (cpDNA) and nuclear ribosomal DNA (nrDNA) restriction site analysis. Within Microthlaspi, 31 cpDNA restriction site mutations, six nrDNA restriction site variations, and two length mutations in the IGS region of the nrDNA were found, and a molecular phylogeny of the species complex has been derived. Polymorphisms in molecular data partitioned cytotypes of M. perfoliatum. The geographical distribution patterns apparently reflect ancient speciation processes and postglacial vegetation history.Key words: chloroplast DNA, nuclear ribosomal DNA, Microthlaspi perfoliatum polyploid complex, molecular phylogeny, biogeography.

Download Full-text

Intra- and inter-specific variation in nuclear ribosomal internal transcribed spacer 1 of the Schistosoma japonicum species complex

Parasitology ◽

10.1017/s003118209800242x ◽

1998 ◽

Vol 116 (4) ◽

pp. 311-317 ◽

Cited By ~ 55

Author(s):

L. VAN HERWERDEN ◽

D. BLAIR ◽

T. AGATSUMA

Keyword(s):

Schistosoma Japonicum ◽

Ribosomal Dna ◽

Internal Transcribed Spacer ◽

Species Complex ◽

Sequence Variation ◽

Nuclear Ribosomal Dna ◽

Single Individual ◽

Repeat Sequences ◽

Dna Repeat ◽

Specific Variation

The first internal transcribed spacer (ITS1) of the nuclear ribosomal DNA repeat was sequenced for members of the Schistosoma japonicum species complex (S. malayensis, S. mekongi and 2 geographical isolates of S. japonicum). The ITS1 is composed of 3 distinct regions: the 5′ end (23 nucleotides); a tract of approximately 90–140 nucleotides, which occurs up to 7 times in tandem, the number varying even within an individual in all species investigated in this study; the 3′ region (378 nucleotides), which lacks repeats. There is size and sequence variation among copies of the ITS1 repeat within a single individual. The relative abundances of size variants of ITS1 in S. japonicum have been ascertained by hybridizing genomic digests with an ITS1 probe. Multiple repeats and intra-individual variation in numbers and abundance of these is a feature of the Asian schistosomes, but not generally of African schistosomes. Possible reasons for this difference in ITS1 between African and Asian schistosomes are discussed. The ITS1 repeat sequences described for African schistosomes are different to, and cannot be aligned with, those from the Asian species described here, whereas the remainder of the ITS1 can be aligned quite easily.

Download Full-text