The Xiphinema americanum-group. II. Morphometric relationships

Hierarchical cluster analysis on morphometrics placed 117 populations, representing 39 putative species, of the Xiphinema americanum group into four clusters. Cluster 1 consisted of three populations identified as X. brevisicum; Cluster 2 consisted of five sub-clusters of populations; and Cluster 3 and 4 each consisted of seven sub-clusters. When several populations ascribed to a putative species were used, they usually clustered with a long range of variability, thus confirming their similarity. A population that had been identified as representing X. diffusum and another as being X. incognitum were placed in clusters different from that which characterized the rest of the populations of each species, respectively. Populations identified as X. americanum sensu stricto, X. thornei, X. santos and X. pachydermum were placed in 2 and 3 different sub-clusters within the same major cluster. Conversely, several populations of X. madeirense, X. duriense and X. pachtaicum had a low coefficient of dissimilarity (<2.8), which is considered as being indicative of intra-specific variability. Four populations, each identified as representing X. pachydermum, were placed in three different sub-clusters of Cluster 4, thus indicating wide morphometric variability for this putative species.