Resumen
- Amphimictic populations of root-lesion nematodes with numerous males and females having three lip annuli, a functional spermatheca and non-areolated lateral field occur on sword fern (Nephrolepis exaltata) in Florida. Identified for decades as Pratylenchus penetrans, they appeared to be a morphologically separated species on the basis of a longer stylet (17.8-18.3 μm) than P. penetrans (15-17 μm) and different lip pattern in en face view (rectangular vs dumb-bell in P. penetrans). Morphologically similar amphimictic root-lesion nematodes have also been detected on flax lily in Costa Rica. Subsequent morphological observations indicated that these amphimictic root-lesion nematodes from fern and flax lily are closely related to the parthenogenetic species P. bolivianus, which has areolated lateral fields. In spite of the reproductive and morphological dissimilarities between these populations, their separation into different species was not supported by the results of molecular analyses of their DNA sequences. The populations used in these analyses included those that are amphimictic from Florida and Costa Rica and others that are parthenogenetic from the type locality in Bolivia, and geographically distant localities in Chile, China, Colombia and Europe.