Data from: Tradeoffs with growth limit host range in complex life cycle helminths

Parasitic worms with complex life cycles have several developmental
stages, with each stage creating opportunities to infect additional host
species. Using a dataset for 973 species of trophically transmitted
acanthocephalans, cestodes, and nematodes, we confirmed that worms with
longer life cycles (i.e. more successive hosts) infect a greater diversity
of host species and taxa (after controlling for study effort). Generalism
at the stage level was highest for ‘middle’ life stages, the second and
third intermediate hosts of long life cycles. By simulating life cycles in
real food webs, we found that middle stages had more potential host
species to infect, suggesting that opportunity constrains generalism.
However, parasites usually infected fewer host species than expected from
simulated cycles, suggesting generalism also has costs. There was no
tradeoff in generalism from one stage to the next, but worms spent less
time growing and developing in stages where they infected more
taxonomically diverse hosts. Our results demonstrate that life cycle
complexity favors high generalism, and host use across life stages is
determined by both ecological opportunity and life history tradeoffs.