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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") 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.