Experimental and Applied Acarology (2000) 24, 365-376

M. Navajas, A. Tsagkarakov, J. Lagnel and M.J. Perrot-Minnot (2000)
Genetic differentiation in Tetranychus urticae (Acari : Tetranychidae): polymorphism, host races or sibling species ?
Experimental and Applied Acarology 24 (5-6), 365-376
Abstract: Based on allozyme electrophoresis at the Pgm locus and nuclear ribosomal DNA (ITS2) sequences, we studied the genetic variation of the two-spotted spider mite Tetranychus urticae Koch collected on rose bay, Nerium oleander L. (Apocynaceae), from several localities around the Mediterranean basin. In addition, we compared these results with those of Navajas et al. (1998) and Tsagkarakou (1997) who collected from several other host plants from the Mediterranean. In the western part of this area (Spain, France, Tunisia), we found the individuals collected from rose bay to be clearly genetically differentiated from other samples. No evidence of such host-associated differentiation was detected in the eastern Mediterranean (Italy and Greece). The genetic differentiation of mites collected on rose bay was investigated further by studying the reproductive incompatibilities between populations in Greece and in France and a laboratory strain reared on bean, Phaseolus vulgaris, in France. Reciprocal crosses performed between these strains revealed variable levels of incompatibility, spanning from partial to complete reproductive isolation. In all cases incompatibility was asymmetric. We designed a test based on double-mating to establish the fertilization status of females in fully incompatible crosses. These crosses showed that the females had been inseminated, which suggests that the barrier to reproduction is not of a prezygotic behavioral nature. The data raises the question of the relative role of ecological factors (host plant) and geographical distance, in the ongoing differentiation process potentially leading to speciation.
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Link to article at publishers website
Database assignments for author(s): Maria Navajas

Research topic(s) for pests/diseases/weeds:
general biology - morphology - evolution
environment - cropping system/rotation

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Pest and/or beneficial records:

Beneficial	Pest/Disease/Weed	Crop/Product	Country	Quarant.
	Tetranychus urticae		France
	Tetranychus urticae		Greece
	Tetranychus urticae		Italy
	Tetranychus urticae		Spain (continental)
	Tetranychus urticae		Tunisia