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.
1. Range limits of estuarine animals
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
intriguing group.
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") can swim in the plankton, and the length of
time they are planktonic is thought to determine how far they get
dispersed by ocean currents. Such dispersal is critical to maintain gene
flow and allow colonization of new habitats in species that have limited
mobility as adults (think clams.. where's a clam gonna go?) Repeatedly
in most animal groups, some species have evolved larvae that don't need
to feed to complete development; lecithotrophic larvae spend less time
or no time in the plankton, and hence do not disperse far if at all.
Why some species lose highly dispersive larvae from their life cycle remains
a scientific mystery. Theory predicts dramatic effects of such transitions on
population dynamics, gene flow, speciation, range size, and rates of
molecular evolution. My lab is studying 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 shifts over the evolutionary history of a group.
top: veliger larva of a snail We also study the consequences of shifts to non-dispersing larvae by
bottom: egg mass of the sea comparing (1) population genetic structure of related, ecologically similar
slug Elysia subornata, with a species that differ in their larval lifespan, and (2) differential colonization
colorful ribbon of orange yolk ability of species with alternative larval types.
All images © Patrick Krug.