Welcome to the Krug lab at CSU Los Angeles. We study the ecology and evolution of marine animals, focusing
on the role of dispersal by planktonic larval stages. We seek to understand how dispersal and habitat colonization
by larvae link populations, and to identify factors that limit gene flow, set range limits, and promote speciation
in the sea. The lab uses a group of herbivorous sea slugs as a model system to understand the general forces
that influence the evolution of marine life histories and impact coastal population dynamics.
Click on the major research topics (below) or the links on the left to learn more about our research.
Some students in the lab study the evolutionary
ecology of range limits, to better understand how
the physical environment (heat, salinity),
biological interactions (competition, predation),
and coastal currents that deliver larvae together
define where a species occurs. This work will
lead to better predictions of ecosystem response to
ongoing climate change. We use sea slugs in the
genus Alderia as a model system for studies along
the Californian coast.
A sampler of sacoglossan diversity
2. Phylogenetics and evolution of the Sacoglossa, solar-powered sea slugs
We use DNA sequences to infer the phylogeny, or
"family tree", of a sea slug group called sacoglossans.
These slugs are an exciting group with which to study
key evolutionary processes. Most are herbivores that
feed, mate and lay eggs on one type of host algae.
We are testing the hypothesis that ecological speciation
has frequently resulted from switches onto new host
algae among these often colorful animals. We are also
studying how traits such as larval development and
violent mating have changed over the history of this
Some sacoglossans also have the remarkable ability to
store chloroplasts (the part of plant and algal cells
that perform photosynthesis) from their meals.
Instead of being digested, the hijacked chloroplasts
continue to pump out nutrients for the slug, in some
species for many months. We are modeling the
evolution of such "kleptoplasty" with collaborators.
3. Larval biology:
Causes and consequences of shifts in larval development
Marine invertebrates have a two-stage life cycle, with non-reproductive
larval stages that metamorphose into the adult form. Feeding larvae
(termed planktotrophic) develop in the plankton for long periods of
time, during which they are dispersed by ocean currents. Dispersal
maintains gene flow and allows colonization of new habitats in species
with limited adult mobility (think clams.. where's a clam gonna go?)
Repeatedly in most animal groups, some species have evolved larvae that
complete development without feeding (lecithotrophic larvae), and spend
comparatively little time in the plankton; lecithotrophs do not disperse as far.
Why some species lose dispersive larvae from their life cycle remains a puzzle.
Theory predicts dramatic effects of such transitions on population dynamics,
gene flow, speciation, range size, and rates of molecular evolution. We study
the causes of evolutionary shifts in larval type in two ways: (1) using rare species
that express both types of larval development at different times or places, and
(2) by identifying traits associated with such shifts over evolutionary time.
We also study the consequences of shifts to non-dispersing larvae for (1) the
top: veliger larva of a snail (1) population genetic structure of related, ecologically similar species that
bottom: egg mass of the sea differ in their larval lifespan, and (2) reproductive compatibility and genetic
slug Elysia subornata, with a diversity among populations in species that produce alternative larval types.
colorful ribbon of orange yolk
All images © Patrick Krug.