Michael Singer

Professor, Section of Integrative Biology

  Education | Research Interests |Advice to graduate students| Publications

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PAT 624
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  • B.A., Oxford University, 1967
  • Ph.D., Stanford University, 1971

Research Interests

Research: Evolutionary ecology of plant-insect interactions:  changing interests from source-sink dynamics to phylogeography to incipient speciation.

Our group has been interested in ecological, evolutionary and behavioral mechanisms by which plant-feeding insects come to be distributed across landscapes in both space and time.  This interest spans what is beginning to seem like a very long time, my first publication on this topic was in Evolution in 1971.  However, it isn’t static!   It has evolved!  Below I've listed some of the main threads

Metapopulation dymanics, 1980's-2000's

During the 1980's and 1990's our group worked intensively on metapopulation-level interactions between habitat patches where the same insect species used different host plants and suffered opposing selection pressures.   We studied both the ecological and evolutionary dynamics resulting from the movement of insects among different types of habitat patch (Thomas et al. 1996 AmNat, Singer & Thomas 1996 AmNat).   These studies led my grad student Davy Boughton to a dissertation on the rules involved in dispersal (Boughton 2000 AmNat) and the reversibility of source-sink relationships (Boughton 1999 Ecology).

This interest in metapopulations led to a strong collaboration with Ilkka Hanski's group in Finland (eg Kuussaari, Singer & Hanski 2000 Ecology; Hanski & Singer 2001 AmNat).  When host preferences are diverse, colonization rates of particular patch types result not just from habitat quality but from differences among individual insects in their perception of habitat quality that stem from their differences in preference.  In consequence, the likelihood that an empty habitat patch will be colonized depends on the match between the host composition of the patch and the host preferences of insects that encounter the patch.

Insect gene flow across landscapes with different host plants (1990's-2000's) 

A longstanding theme in phylogeography is the role of local adaptation in gene flow.  With respect to herbivorous insects, this work has concentrated on host-plant relations.  Our own group's initial foray into this area was to ask whether relatedness among Euphydryas editha butterflies was correlated with host use.  We first used an mtDNA gene tree to ask this question (Radtkey & Singer 1995 Evolution.).  We concluded that there was no strong relationship, suggesting that each host had been repeatedly colonized.  This wasn't wonderfully strong evidence, though it did show that we were not dealing with a set of cryptic species, one on each host.

I picked up this theme again in 2001-2004, in collaboration with my student Brian Wee.  We devised a project to ask what were the relative roles in population genetic differentiation of three factors: current adaptation to hosts, physical barriers to gene flow in the landscape and population history.  We used AFLP analysis of nuclear DNA to examine genetic differentiation among conspecific butterflies using the same or different hosts.  We did this at three spatial scales:  300 meters, 20 kilometers and 1000 kilometers.   The original idea of the project was to examine isolation by distance (IBD), modify the IBD relationship by modeling the real landscapes and then ask whether residuals from the modified IBD were best explained by local adaptation or by historical factors.

The project has produced some complex and unexpected results, among them the conclusion that host use is more closely associated with genetic variance than with mean genotype.  Much remains to be published but here is a link to a chapter from Brian's dissertation to show the flavor plus a summary paper from a recent symposium in Finland (pdf).

Incipient ecological speciation?   2003-2010

Although the AFLP results are not easy to interpret, they do indicate that host use affects gene flow, independently of geographic separation of populations. I presented these data at a seminar in UC Davis in 2003. Carolyn McBride, a grad student at Davis, suggested that the AFLP data would allow us to choose population pairs that were all genetically equidistant but that fell into three categories of host adaptation: both populations adapted to host A, both adapted to host B: one population adapted to host A and the other to host B. Her idea was that hybrids made within these population pairs could be used to ask questions about the influence of local adaptation on hybrid fitness, while controlling for overall genetic differentiation. And so this is what we did in 2004-2006. We've had fun with this project and it has worked well; it is now complete and our first paper is just published. This paper describes the adaptive suites associated with use of particular hosts; (pdf)

Upcoming MSS from this project will concern the ecological context for the development of these adaptive suites and the properties of hybrid insects. Some of these properties can be guessed from the Singer-McBride paper. Hybrids between insects adapted to different hosts are intermediate in geotaxis and in clutch size, with adverse consequences for their fitness in the field.

Longstanding interests.

1)  One longstanding interest is anthropogenic evolution of insect diet.  A book chapter is just published (2007).  (pdf)

2)  I've become interested in the application of basic knowledge about insect host preference behavior to the problems of choosing insects as agents for biological control of weeds.   Here is a keynote paper from the 2004 International Symposium on BioContrrol of Weeds.  Sorry the figire is missing!  (pdf)

3) Unexpected axes of variation in plant-insect interactions.
There are philosophical difficulties in separating and measuring traits of plants and traits of insects relevant to the plant-insect interaction, and in distinguishing these traits from those of the interaction itself (Singer, 2000. Ecology Letters).    I have been interested identifying unexpected axes of variation in plant-insect interactions, and assessing the implications of these variables for experimental design (Singer & Lee 2000, Ecology Letters).  One finding is that sampling individuals at random for experiments can give misleading results when species do not, in practice, interact at random.  A standard experimental design using random sampling gave the conclusion that host preferences of several insect populations were maladaptive, and we were able to show that this conclusion was incorrect (Singer, Stefanescu & Pen,  Ecology Letters, January 2002).

Info for prospective grad students:

I typically supervise a small group, 2-4 students, some independent and some collaborative.  I don't run a molecular lab, so students doing molecular work in collaboration with me have been co-supervised by other faculty; most recently Brian Wee (PhD 2004) was co-supervised by Ulrich Mueller.   At present (2006) my strongest collaboration is with a postdoc at Rockefeller, Lindy McBride.

I have written some general advice about choosing a grad school and a supervisor; you can find it on this website.


Papers by Singer and collaborators, 1990-present:

In revision:

  • Singer M C, Parmesan C. Phenological asynchrony between herbivorous insects and their hosts: a naturally evolved starting point for climate change impacts? Submitted to Philosophical Transactions of the Royal Society. (pdf)


  • Singer, M. C. &. C. S. McBride. 2010. Multi-trait, host-associated divergence among sets of butterfly populations: implications for reproductive isolation and ecological speciation. Published online October 10 2009 in: Evolution (print version will be in 2010).

  • Neve G, Singer MC. 2008. Protandry and postandry in two related butterflies: conflicting evidence about sex-specific trade-offs between adult size and emergence time. Evolutionary Ecology 22: 701-709.

  • Olivieri I, Singer MC, Magalhaes S, et al. 2008. Genetic, ecological, behavioral and geographic differentiation of populations in a thistle weevil: implications for speciation and biocontrol. Evolutionary Applications 1: 112-128.

  • Wee B, Singer MC. 2007. Variation among individual butterflies along a generalist-specialist axis: no support for the 'neural constraint' hypothesis. Ecological Entomology 32 : 257-261

  • Singer MC, Wee B. 2005. Spatial pattern in checkerspot butterfly-host plant association at local, metapopulation and regional scales . Annales Zoologici Fennici 42 : 347-361

  • Haikola S, Singer MC, Pen I . 2004. Has inbreeding depression led to avoidance of sib mating in the Glanville fritillary butterfly (Melitaea cinxia)? Evolutionary Ecology 18: 113-120

  • Van Nouhuys S, Singer MC, Nieminen M . 2003. Spatial and temporal patterns of caterpillar performance and the suitability of two host plant species. Ecological Entomology 28 : 193-202

  • Singer MC, Stefanescu C, Pen I. 2002. When random sampling does not work: standard design falsely indicates maladaptive host preferences in a butterfly. Ecology Letters 5 : 1-6. (pdf)

  • Nieminen, M., Singer, M.C., Fortelius, W, Schöps, K. and Hanski, I. 2001. Experimental confirmation that inbreeding depression increases extinction risk in butterfly populations. American Naturalist 157, 237-244.

  • McNeely, C. & M.C. Singer. 2001. Contrasting roles of learning in butterflies foraging for nectar and oviposition sites. Animal Behaviour. (pdf)

  • Hanski, I. & M.C. Singer. 2001.. Colonization and oviposition preference in butterfly metapopulations. American Naturalist 158: 341-353. (pdf)

  • Singer, M.C. 2000. Reducing ambiguity in describing plant-insect interaction: "preference", "acceptability" and "electivity". Ecology Letters 3:159-162. (pdf)

  • Kuussaari, M., M.C. Singer & I. Hanski. 2000 Local Specialization and landscape-level influence of host use in a herbivorous insect. Ecology 81: 2177-2187.

  • Agnew, K. & M. C. Singer. 2000. Does fecundity drive the evolution of insect diet? Oikos 88: 533-538.

  • Singer, M.C., Brian Wee, Sara Hawkins & Marie Butcher. 2007. Rapid Natural and anthropogenic diet evolution: three examples from checkerspot butterflies. Chapter 22 in: Specialization, speciation and radiation: the evolutionary biology of herbivorous insects. Ed. by Kelley Tilmon. University of California press.

  • Singer, M.C. & J. R. Lee. 2000. Discrimination within and between host species by a butterfly: implications for design of preference experiments. Ecology Letters 3:101-105. (pdf)

  • Singer, M.C. and C. D. Thomas. 1996. Evolutionary responses of a butterfly metapopulation to human and climate-caused environmental variation. American Naturalist 148: S9-S39.

  • Thomas, C. D., M. C. Singer and D. Boughton. 1996. Catastrophic extinction of population sources in a butterfly metapopulation. American Naturalist 148: 957-975.

  • Parmesan, C., M.C. Singer & I. Harris. 1995. Absence of adaptive learning from the oviposition foraging behaviour of a checkerspot butterfly. Animal Behaviour 50: 161-175.

  • Radtkey, R. & M.C. Singer. 1995. Repeated reversals of host preference evolution in a specialist insect herbivore. Evolution 49: 351-359.

  • Singer, M.C., C.D. Thomas, H.L. Billington & C. Parmesan. 1994. Correlates of speed of evolution of host preference in a set of twelve populations of the butterfly Euphydryas editha. Ecoscience 1: 107-114.

  • Singer, M.C. and P.R. Ehrlich. 1994.Host specialization of satyrine butterflies, and their responses to habitat fragmentation in Trinidad. Journal of Research on the Lepidoptera. 30: 248-256.

  • Singer, M. C. and C. Parmesan. 1993. Sources of variation in patterns of plant-insect interaction. Nature 361:251-253.

  • Singer, M. C., C. D. Thomas & C. Parmesan. 1993. Rapid human-induced evolution of insect diet. Nature 366; 681-683.

  • Singer, M. C., D. Ng, D. Vasco and C. D. Thomas. 1992. Rapidly evolving associations among oviposition preferences fail to constrain evolution of insect diet. American Naturalist 139: 9-20.

  • Singer, M.C. and C.D. Thomas. 1992. The difficulty of deducing behavior from resource use: an example from hilltopping in checkerspot butterflies. American Naturalist 140: 654-664.

  • Singer, M.C., D. Vasco, C. Parmesan, C.D. Thomas and D. Ng. 1992. Distinguishing between preference and motivation in food choice: an example from insect oviposition. Animal Behaviour 44: 463-471.

  • Singer, M. C., R. A. Moore, and D. Ng. 1991. Genetic variation in oviposition preference between butterfly populations. J. Insect Behavior 4:531-535.

  • Thomas, C.D., D. Vasco, M.C. Singer, D. Ng, R.R. White and D. Hinkley 1990. Diet divergence in two sympatric congeneric butterflies: community or species level phenomenon? Evolutionary Ecology 4: 62-74.

Papers by Graduate Students from work supervised by Singer:

  • Boughton, D.A. 2000.  The Dispersal System of a Butterfly: A test of source-sink theory suggests the intermediate-scale hypothesis.  American Naturalist 156; 131-144.
  • Boughton, D.A.  1999. Empirical evidence for complex source-sink dynamics with alternative states in a butterfly metapopulation. Ecology  80: 2727-2739.
  • Sword, G. A.  1999   Density-dependent warning coloration. Nature 397: 217.
  • Sword, G.A. and Dopman, E.B. (1999) Developmental specialization and geographic structure of host plant use in a polyphagous grasshopper, Schistocerca emarginata. Oecologia. 120:437-445.
  • Sword GA. 2001. Tasty on the outside, but toxic in the middle: grasshopper regurgitation and host plant-mediated toxicity to a vertebrate predator Oecologia 128: 416-421

The long-term focus of our group's work has been to understand spatial and temporal patterns of plant-insect association, using behavioral, ecological and evolutionary tools. In this sense the group differs from most other plant-insect folk, who are more firmly rooted in one conceptual discipline or another. So, among our publications you'll find purely ecological stuff (eg. Hanski & Singer 2001, Kuussaari et al. 2000, Singer & Parmesan 1993), purely behavioral work (eg. Singer, Vasco et al. 1992, Parmesan et al. 1995, McNeely & Singer 2001) and purely evolutionary studies (eg. Singer et al. 1993, Radtkey & Singer 1995, Singer & Thomas 1996). Check out the titles in the pubs list below and you'll see what I mean.