KRUG LAB - EVOLUTIONARY AND LARVAL ECOLOGY OF MARINE INVERTEBRATES
Welcome to the Krug lab at Cal State Los Angeles. We study the ecology and evolution of marine animals, focusing on the role of dispersal by planktonic larval stages, and resource specialization of adult stages. We seek to understand
how larval dispersal, reproductive biology, or host use may set range limits or 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, local adaptation, and ultimately drive lineage diversification. Click on the major research topics (below) to learn more.
1. Chemical ecology of estuaries. We are studying how the chemical defense of abundant sea slugs (Alderia) alters food webs, making the slugs unpalatable to predators, and also has unexpected effects on the surrounding ecosystem. We are performing experiments to test how slug chemistry affects infaunal organisms living in and on mudflats, both positively and negatively, and the broader effects of changes in community diversity and composition. This should lead to better predictions of how climate change will affect coastal ecosystems, as slug populations are rapidly responding to drought and warming trends.
2. Phylogeny & evolution of Sacoglossa, solar-powered sea slugs.
Using DNA sequences, we infer the phylogeny or "family tree" of a sea slug group called Sacoglossa, and study key evolutionary processes in this framework. Sacoglossans are herbivores that feed, mate and lay eggs on specific host algae. We are investigating how traits like larval development mode, reproductive structures, and algal host use have influenced speciation and lineage diversification over macroevolutionary time. We and colleagues also help curate and create Sacoglossa pages for ScratchPads that feed into the Encyclopedia of Life.
Some sacoglossans exhibit kleptoplasty, storing chloroplasts (the organelle
in plant and algal cells that performs photosynthesis) from their meals within gut cells. Instead of being digested, hijacked chloroplasts continue to provide nutrients for the slug, in some species for months. We are studying how kleptoplasty evolved and how it affects the slugs' ecology.
top: veliger larva of a snail; bottom: egg mass of the sea slug Elysia subornata, with a colorful ribbon of orange extra-capsular yolk
All images © Patrick Krug.
3. Causes & consequences of shifts in larval development. Marine invertebrates have a two-stage life cycle, with non-reproductive larvae that metamorphose into the adult form. Feeding (planktotrophic) larvae develop over weeks to months as they are dispersed by ocean currents, which maintains gene flow and allows colonization of new habitats in species with low adult mobility (think clams--how far's a clam gonna go?)
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Repeatedly in most animal groups, some species have evolved lecithotrophic larvae that complete development without feeding, and spend comparatively little time in the plankton; lecithotrophic larvae generally do not disperse as far.
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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. We also study the consequences of shifts to non-dispersing larvae for (1) the population genetic structure of related, ecologically similar species that differ in larval lifespan, and (2) reproductive compatibility and genetic diversity among populations in species that produce alternative larval types.
Funding for the Krug lab has come from:
National Science Foundation programs in
Biological Oceanography (OCE-1130072, 0648606, 0242272)
Division of Environmental Biology - Phylogenetic Systematics (DEB-0817084, 1355190)
Human Resources Division
Major Research Instrumentation (DBI-0421537)
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COAST: CSU Council on Ocean Affairs, Science & Technology
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CSUPERB: California State Univ. Program for Education and Research in Biotechnology
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The LaKretz endowment for environmental science at Cal State L.A.
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Support for graduate and undergraduate students has come from:
National Science Foundation:
GK-12 programs (Science for our Schools, ImpactLA)
Louis Stokes Alliance for Minority Participation (LSAMP) program
UMEB/UMR program
National Institutes of Health:
Minority Opportunities in Research (MORE) program
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