Data from: Species selection favors dispersive life histories in sea slugs, but higher per-offspring investment drives shifts to short-lived larvae

For 40 years, paleontological studies of marine gastropods have suggested
that species selection favors lineages with short-lived (lecithotrophic)
larvae, which are less dispersive than long-lived (planktotrophic) larvae.
Although lecithotrophs appeared to speciate more often and accumulate over
time in some groups, lecithotrophy also increased extinction rates, and
tests for state-dependent diversification were never performed. Molecular
phylogenies of diverse groups instead suggested lecithotrophs accumulate
without diversifying due to frequent, unidirectional character change.
Although lecithotrophy has repeatedly originated in most phyla, no adult
trait has been correlated with shifts in larval type. Thus, both the
evolutionary origins of lecithotrophy and its consequences for patterns of
species richness remain poorly understood. Here, we test hypothesized
links between development mode and evolutionary rates using
likelihood-based methods and a phylogeny of 202 species of gastropod
molluscs in Sacoglossa, a clade of herbivorous sea slugs. Evolutionary
quantitative genetics modeling and stochastic character mapping supported
27 origins of lecithotrophy. Tests for correlated evolution revealed
lecithotrophy evolved more often in lineages investing in extra-embryonic
yolk, the first adult trait associated with shifts in development mode
across a group. However, contrary to predictions from paleontological
studies, species selection actually favored planktotrophy; most extant
lecithotrophs originated through recent character change, and did not
subsequently diversify. Increased offspring provisioning in planktotrophs
thus favored shifts to short-lived larvae, which led to short-lived
lineages over macroevolutionary time scales. These findings challenge
long-standing assumptions about the effects of alternative life histories
in the sea. Species selection can explain the long-term persistence of
planktotrophy, the ancestral state in most clades, despite frequent
transitions to lecithotrophy.