Data from: Exploitation of the same trophic link favors convergence of larval life-history strategies in complex life cycle helminths

Switching from one host to the next is a critical life history transition
in parasites with complex life cycles. Growth and mortality rates are
thought to influence the optimal time and size at transmission, but these
rates are difficult to measure in parasites. The parasite life cycle, in
particular the trophic link along which transmission occurs, may be a
reasonable proxy for these rates, leading to the hypothesis that life
cycle should shape life history strategy. We compiled data on the size and
age at infectivity for trophically-transmitted helminths (i.e.
acanthocephalans, cestodes, and nematodes), and then categorized species
into trophic links (e.g. planktonic crustaceans to fish, insects to
terrestrial vertebrates, etc.). Comparative analyses that explicitly
included stabilizing selection within trophic links fit the data
significantly better than random walk models, indicating that parasites
with different life cycles have different optimal times/sizes for host
switching. The major helminth groups have often independently evolved
similar life cycles, and we show that this has frequently led to
convergent and/or parallel evolution of size and age at infectivity. This
suggests that for particular life cycles there are universal optimal
transmission strategies, applicable to widely divergent taxa, although the
cases of parallelism might indicate that lineage-specific constraints
sometimes prevent evolution to a single adaptive peak.