Variation Within the Xiphinema Americanum Group (Nematoda: Longidoridae)

Abstract

The influence of geographic location, latitude, mean annual precipitation, and temperature, on 75 populations of Xiphinema americanum sensu lato was studied. Twenty-one populations were from Florida, 17 from 9 other states and Canada, 20 from 8 European countries, 8 from Central and South America, 8 from Africa, and 1 from Asia. Criteria for comparison were as follows: female body length, vulva position (expressed as percentage of body length), de Manian and c ratios (body length divided by body width or tail length), stylet length, tail shape, and the ratio between tail length and body width at the anus (T/BWA Ratio). European populations mainly from Mediterranean countries were distinct from other populations primarily in ratio, vulva position, and tail shape, criteria which could be considered adequate for regarding these populations as a discrete species. The data further suggest that shorter nematodes with smaller ratios, a wider range of c ratios and stylet lengths, and lower vulva percentages are correlated with localities closer to the equator that have high amounts of precipitation and high mean temperatures.