01738nas a2200145   4500008004100000245008100041210006900122260000900191490003100200520121400231100002301445700002201468700002201490856008001512       2009                        eng d00aCompetition promotes the evolution of host generalists in obligate parasites0 aCompetition promotes the evolution of host generalists in obliga  c20090 vdoi:10.1098/rspb.2009.11743 a<p>Ecological theory traditionally predicts that interspecific competition selects for an increase in ecological specialization. Specialization, in turn, is often thought to be an evolutionary &lsquo;dead end,&rsquo; with specialist lineages unlikely to evolve into generalist lineages. In host&ndash;parasite systems, this specialization can take the form of host specificity, with more specialized parasites using fewer hosts. We tested the hypothesis that specialists are evolutionarily more derived, and whether competition favours specialization, using the ectoparasitic feather lice of doves. Phylogenetic analyses revealed that complete host specificity is actually the ancestral condition, with generalists repeatedly evolving from specialist ancestors. These multiple origins of generalists are correlated with the presence of potentially competing species of the same genus. A competition experiment with captive doves and lice confirmed that congeneric species of lice do, in fact, have the potential to compete in ecological time. Taken together, these results suggest that interspecific competition can favour the evolution of host generalists, not specialists, over macroevolutionary time.</p>
1 aJohnson, Kevin, P.1 aMalenke, Jael, R.1 aClayton, Dale, H.  uhttps://phthiraptera.myspecies.info/sites/phthiraptera.info/files/47579.pdf01921nas a2200157   4500008004100000245007900041210006900120260000900189300001600198490000700214520140200221100002201623700002301645700002201668856007301690       2009                        eng d00aHost specialization differentiates cryptic species of feather-feeding lice0 aHost specialization differentiates cryptic species of featherfee  c2009  a1427 - 14380 v633 a<p>Parasite species with differentiated host-specific populations provide a natural opportunity to explore factors involved in parasite diversification. Columbicola macrourae is a species of ectoparasitic feather louse currently recognized from 15 species of New World pigeons and doves. Mitochondrial sequences reveal five divergent haplotype clusters within C. macrourae, suggesting cryptic species. Each cluster is relatively host specific, with only one or a few hosts. We conducted a reciprocal transfer experiment with two of these lineages to test whether host use has an adaptive component. Our results demonstrate that the fitness of each lineage is considerably higher on its native host than on the novel host suggesting that one or more selective agents favor host specialization by the different lineages. In addition, we were able to morphologically separate individual lice from the two experimental lineages using discriminant function analysis. Furthermore, differences in the size of these louse lineages match differences in the size of their respective hosts, paralleling the strong correlation between parasite and host body size across the genus Columbicola. Together, these results suggest that selection in this cryptic species complex reflects selection across the whole genus, and that this selection, in part, contributes to the maintenance of host specialization.</p>
1 aMalenke, Jael, R.1 aJohnson, Kevin, P.1 aClayton, Dale, H.  uhttp://www.phthiraptera.info/sites/phthiraptera.info/files/47577.pdf