Length of the planktonic larval period can determine dispersal distances of sedentary benthic animals and thereby influence genetic variation within and among subpopulations, accumulation or elimination of deleterious recessive genes, and adaptation to local conditions. These microevolutionary
changes, together with possible differences in geographic range, may influence speciation and extinction rates. If length of planktonic period is important to evolution, then how does length of planktonic period evolve? Types of embryonic and larval development (benthic or planktonic, feeding
or non-feeding) determine duration of the planktonic period. Therefore conditions controlling types of larval development ultimately control evolutionary processes for descendent lineages insofar as dispersal influences these processes. Here 1 list 10 hypotheses on persistence of types of
development and transitions between types of development. These conditions include trades between rate of early development, rate of early growth, and risks from benthic and planktonic predators. The size of adults and larvae, body plans of adults, body plans and feeding mechanisms of larvae,
and internal fertilization determine the form of these trades. Transitions between types of development are restricted by a bias against recovery of a feeding larval stage and stabilizing selection for local adaptive optima. Advantages of long distance dispersal, differences in reproductive
effort, and adaptations for larval settlement have little effect on type of larval development and duration of planktonic periods.
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