Genes, organisms, and areas: the problem of multiple lineages

The presence of multiple species lineages can cause problems in biogeographic and cospeciation studies analogous to the problems gene paralogy can cause in molecular systematics. The differential survival of these lineages, coupled with inadequate sampling, can distort esti? mates of area relationships in biogeography or host-parasite relationships in parasitology. (Bio- geography; cladistics; congruence; orthology; paralogy; parasitology.) Molecular systematists, parasitologists, and biogeographers all use cladograms to reconstruct the history of various entities, such as genes, organisms, and areas. All three disciplines share the problem of us? ing cladograms for one entity to infer cladograms for another. A molecular sys- tematist interested in reconstructing the phylogeny of a group of organisms using DNA sequences bases that reconstruction on a cladogram of genes. A biogeographer infers the history of a group of areas from the phylogeny of a sample of the resident organisms. Parasitologists may seek to con? struct a cladogram for a group of host taxa from the cladogram of the parasites of those taxa.