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Ronald M. Coleman: Research Interests
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Updated: August 16, 2017

Be sure to see my other website: the Cichlid Research Home Page <http://cichlidresearch.com>

Research Interests:

Evolutionary Ecology, typically of fishes

I am interested in both experimental and theoretical evolutionary ecology. My main interest is in aspects of fish reproduction and parental care, though I am interested in all areas of evolutionary ecology. I am also interested in practical application of evolutionary ecology to such issues as fisheries management and aquarium fish husbandry.

In brief, questions which contain the words "tradeoff", "decision" and "diversity" interest me most, e.g.
"Why do different fishes lay different sized eggs?"

"How do parents resolve the tradeoff between investing in current offspring versus investing in future offspring?"
"Why does this species care for its offspring and that species does not?"

Approaches to Research:

I use a diversity of approaches for understanding evolutionary ecology. In particular, I do the following:

My basic approach can be characterized as follows:

Field Sites

Current Research Projects:

Cichlid Fry Project

A large (~20) group of undergraduates are investigating the relationship between fry size and egg size in cichlid fishes.

Cichlid Simulator Project

Team ThinkTank (a group of five Computer Science students) and I are developing a simulation of a cichlid fish tank.

Campus Tree Project

We are mapping the trees on campus. See Sacramento State Online Natural History Museum

Evolution of Parental Investment Decisions

I am interested in determining which factors influence the behavior performed by parental fishes. For example, what influences a parental male sunfish to invest in its offspring? Are these investment decisions affected by brood number (yes), past investment (yes) and/or other factors?


How do parents in biparental investment situations decide how much to invest? Do the investment decisions of one parent affect the investment decisions of the other?

Evolution of Egg Size in Fishes

Egg size is a special case of parental investment, not because it is subject to different rules than other forms of investment, but rather because it can be measured so precisely. It is because egg size can be measured so precisely and consistently that it is particularly startling how variable egg size is among species of fishes.

So far I have addressed this issue in cichlid fishes, which display a perplexing diversity of egg sizes between species, yet remarkably little variation within a species. Analysis of this single character has revealed complex interrelationships between cichlid physiology, behavior and ecology.

I have been pursing this investigation through carefully controlled manipulations in the laboratory as well as observations and experiments in the field using cichlids, notably in Costa Rica, Nicaragua and Mexico.

In the near future, I will be expanding this project to include many other fishes and in fact, to consider egg size in fishes in general.


Evolution of Parental Care States

Why do some species of fishes exhibit male care while others exhibit female care? Other species exhibit biparental care and yet others provide no care at all. This fundamental question is difficult to work on because in many lineages the form of care is fixed or shows little diversity within a lineage. For example, there are no birds which do not exhibit some parental care. All sunfishes exhibit male parental care and therefore do not provide the diversity necessary to study this problem. Fortunately, some families of fishes, such as the cichlids exhibit a great diversity of parental care states and present many opportunities to study this question.

Other families, such as the Stichaeidae (marine intertidal fish) exhibit an intriguing dichotomy: some species provide male parental care, while other, very similar, species, exhibit female parental care.

In the immediate future, I will be investigating the parental care of the monkeyface eel Cebidichthyes violaceous, a stichaeid found here on the coast in Central California, to add to my previous studies on Anoplarchus purpurescens.

Salton Sea Project

Along with a graduate student, Shannon Waters, we are investigating the ecology of the Salton Sea, California. We are particularly interested in two species, namely the native desert pupfish and the introduced hybrid tilapia (Oreochromis spp.)

For more information on the Salton Sea, go here http://www.water.ca.gov/saltonsea/habitat/eir2011.cfm


Comparative Reproductive Ecology of the Centrarchidae (sunfishes)

The sunfishes and basses are widespread and important fishes in North America. While all species in the family exhibit male parental care, I am particularly interested in the subtle differences in how each species (and individuals within each species) allocate their parental investment.

In the near term, we will be exploring the reproductive biology and parental care of the Sacramento perch (Archoplites interruptus), the only sunfish native to Western North America.


Evolution of Strain Structure in Parasite Populations (The Evolution of Sex)

In collaboration with Alison Galvani at Oxford University and Dr. Neil Ferguson at Imperial College, London, I investigated the evolution of strain structure in macroparasites. Though radically different than fishes, the basic principles of evolutionary ecology apply to this problem as well, namely how do organisms resolve conflicting selection pressures that generate tradeoffs?

In this particular work, we focussed on the idea that long-lived macroparasites, such as helminths, use sex to generate antigenic diversity to evade the immune system of their vertebrate hosts. I am not pursuing this line of research at the moment.


Future Projects

Reproductive ecology and behavior of California fishes

Aquarium fish husbandry from an evolutionary ecological perspective, e.g. does structure in an aquarium reduce aggression?

Reproductive biology of catfishes

Sexual selection in killifishes

Parental care in sticklebacks


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