Ron Karlson, Ph.D.

Research Interests

In retirement, I continue to be interested in scale-dependent processes influencing the structure of marine benthic communities dominated by clonal animals like corals, bryozoans, ascidians, sponges, and hydroids.   Recent research in the Pacific highlights how the local abundance patterns of corals and reef fishes appear to be independent of geographic range, contrary to current theory based on terrestrial organisms.  Research on dynamic east coast fouling communities highlights changes in regional latitudinal distributions, species invasions, and species distinctions due to taxonomic revisions and molecular genetics.

Current Projects

International Activity

Ongoing collaboration with T.P. Hughes et al. at the ARC Centre for Excellence for Coral Reef Studies, James Cook University, Townsville, Australia.  This research is focused on coral and reef fish communities sampled across the west-cental Pacific Ocean.

National Activity

Ongoing collaboration as a Research Associate with R.W. Osman at the Smithsonian Environmental Research Center, Edgewater, Maryland. This research is focused on fouling communities along the US east coast.

Research Group

  • Sean R. Connolly, Ph.D. - Australian Professional Fellow (ARC Centre of Excellence for Coral Reef Studies, James Cook University). Theoretical ecology, coral community ecology.
  • Terence P. Hughes, FAA, Ph.D. - Federation Fellow and Director (ARC Centre of Excellence for Coral Reef Studies, James Cook University). Coral ecology and evolution, socioeconomic and ecological resilience.
  • Richard W. Osman, Ph.D. – Senior Scientist (Smithsonian Environmental Research Center). Benthic population and community ecology.
  • Howard V. Cornell, Ph.D. - Professor Emeritus (Department of Environmental Science & Policy, UC Davis). Theoretical ecology, community ecology.

Selected Publications

Dynamics of Coral Communities cover

  • Hughes, T.P., D.R. Bellwood, S.R. Connolly, H.V. Cornell, and R.H. Karlson. 2014. Double jeopardy and global extinction risk in corals and reef fishes. Current Biology, 24:2946-2951.
  • Karlson, R.H., and R.W. Osman. 2012. Species composition and geographic distribution of invertebrates in fouling communities along the east coast of the USA: a regional perspective. Marine Ecology Progress Series, 458:255-268.
  • Karlson, R.H., S.R. Connolly,and T.P. Hughes. 2011. Spatial variance in abundance and occupancy of corals across broad geographic scales. Ecology, 92:1282-1291.
  • Cornell HV, Karlson RH, Hughes TP. Local-regional species richness relationships are linear at very small to large scales in west-central Pacific corals. Coral Reefs. 2008;27(1):145–151.
  • Cornell HV, Karlson RH, Hughes TP. Scale-dependent variation in coral community similarity across sites, islands, and island groups. Ecology. 2007;88(7):1707–1715.
  • Idjadi JA, Karlson RH. Spatial arrangement of competitors influences coexistence of reef-building corals. Ecology. 2007;88(10):2449–2454.
  • Karlson RH, Cornell HV, Hughes TP. Aggregation influences coral species richness at multiple spatial scales. Ecology. 2007;88(1):170–177.
  • Idjadi JA, Edmunds PJ. The role of scleractinian corals as facilitators for other invertebrates on a Caribbean reef. Mar Ecol Prog Ser. 2006;319:117–127.
  • Idjadi JA, Lee SC, Bruno JF, Precht WF, Allen-Requa L, Edmunds PJ. Rapid phase-shift reversal on a Jamaican coral reef. Coral Reefs. 2006;25(2):209–211.
  • Karlson RH. Metapopulation dynamics and community ecology of marine systems. In: Krizer JP, Sale PF, eds. Marine Metapopulations. Academic Press; 2006.
  • Connolly SR, Hughes TP, Bellwood DR, Karlson RH. Community structure of corals and reef fishes at multiple scales. Science. 2005;309(5739):1363–1365.
  • Karlson RH, Cornell HV, Hughes TP. Coral communities are regionally enriched along an oceanic biodiversity gradient. Nature. 2004;429(6994):867–870.
  • Baird AH, Bellwood DR, Connell JH, et al. Coral reef biodiversity and conservation. Science. 2002;296(5570):1026–8; author reply 1026–8.
  • Callaghan TP, Karlson RH. Summer dormancy as a refuge from mortality in the freshwater bryozoan Plumatella emarginata. Oecologia. 2002;132(1):51–59.
  • Karlson RH. Global, regional, and local patterns in species richness and abundance of butterflyfishes: Comment. Ecology. 2002;83(2):583–585.
  • Karlson RH. Population processes in modular benthic invertebrates. In: Hughes RN, ed. Progress in Asexual Reproduction. New Delhi, India: Oxford and IBH Publishing Co. Pvt. Ltd.; 2002:255–282. Reproductive Biology of Invertebrates XI.
  • Karlson RH, Cornell HV. Species richness of coral assemblages: Detecting regional influences at local spatial scales. Ecology. 2002;83(2):452–463.
  • Cornell HV, Karlson RH. Coral species richness: ecological versus biogeographical influences. Coral Reefs. 2000;19(1):37–49.
  • Karlson RH. Dynamics of Coral Communities. Dordrecht, The Netherlands: Kluwer Academic Publishers; 1999. Population and Community Biology 23.
  • Karlson RH, Cornell HV. Scale-dependent variation in local vs. regional effects on coral species richness. Ecol Monogr. 1998;68(2):259–274.
  • Cornell HV, Karlson RH. Species richness of reef-building corals determined by local and regional processes. J Anim Ecol. 1996;65(2):233–241.
  • Karlson RH, Hughes TP, Karlson SR. Density-dependent dynamics of soft coral aggregations: The significance of clonal growth and form. Ecology. 1996;77(5):1592–1599.
  • Karlson RH, Hurd LE. Disturbance, coral-reef communities, and changing ecological paradigms. Coral Reefs. 1993;12(3-4):117–125.
  • Karlson RH, Taylor HM. Mixed dispersal strategies and clonal spreading of risk – predictions from a branching-process model. Theor Popul Biol. 1992;42(2):218–233.
  • Karlson RH. Size-dependent growth in 2 zoanthid Species – a contrast in clonal strategies. Ecology. 1988;69(4):1219–1232.
  • Karlson RH, Jackson JBC. Competitive networks and community structure – a simulation Study. Ecology. 1981;62(3):670–678.
  • Sutherland JP, Karlson RH. Development and stability of fouling community at Beaufort, North Carolina. Ecol Monogr. 1977;47(4):425–446.



Fax: (302) 831-2281


Department of Biological Sciences
Wolf Hall
University of Delaware
Newark, DE 19716


  • B.A. - Pomona College
  • M.A., Ph.D. - Duke University
  • Postdoctoral - Johns Hopkins University