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


Alderia willowi

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) 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.