My research programme in this field mostly concerns the evolutionary biology of the
hoverflies (Diptera, Syrphidae), a very large group of flower-visiting flies whose diverse larval feeding strategies are particularly
interesting from an evolutionary standpoint. Using comparative and experimental approaches, I concentrate on morphology,
life-histories, feeding specialization and mimetic communities. Funded initially by a Leverhulme fellowship, I am still struggling to
complete a monograph on the evolutionary biology of the Syrphidae. This summarises and reinterprets information from
more than 5300 published works on the family, most of which I have scanned as pdfs; much of this work will be published also as papers. The databases that
abstract the information from the literature will be placed on the Web.
The basic information for all comparative approaches is a phylogeny of the group. With my colleague
Dr Graham Rotheray of the National Museums of Scotland, we have completed a very large phylogeny of most of the Palaearctic
genera of Syrphidae using cladistic methods on larval characters (Rotheray & Gilbert 1989, 1999, 2005).
The large scale of this work makes it possible to use the phylogeny to test many hypotheses about
the evolution of morphological and ecological attributes:
for example, whether particular life-history attributes promote the rate
of speciation (Kazourakis et al 2001). Modern comparative methods fare much better when phylogenies have estimates of
the branch lengths, obtainable from molecular-based phylogenies (Ståhls G, et al, 2003).
Very little is known about the evolution of feeding specialization, and still less about the evolution
of dietary specialisation using phylogenetic information. The Syrphidae are an excellent model system to use in testing
hypotheses because of their diverse larval feeding ecologies, which include economically important aphid predators with
varying degrees of specialization. Research on the evolution of feeding specialization has found a relationship between
prey preference by ovipositing females and the larval performance feeding on those prey, even in an extreme generalist (Sadeghi
& Gilbert 1999, 2000a-c). Specialization may also evolve in response to mortality by natural enemies, the idea
of ‘enemy-free space’. The phylogenies of syrphid hosts and diplazontine parasitoids match,
and reveal the parallel evolution of feeding specialization in both taxa. A review of the interactions known to occur
in the communities where aphidophagous syrphids live (Gilbert 2005a) shows that the community context is an important determinant
of feeding specialisation.
I am very interested in the evolution of the mimetic colour patterns of hoverflies. Aspects of
hoverfly mimetic communities do not match expectations from current mimicry theory, with two main problems: mimics are
too common relative to their models, and are also mostly very imperfect mimics. With a student David Grewcock we developed
the potential of new approaches to the study of these communities of models and mimics, using the hoverfly phylogeny, image
analysis, neural networks and operant conditioning methods, in collaboration with various researchers and students including Winand
Dittrich, Peter McGregor, Patrick Green, Salma Azmeh, Graham Holloway and Tom Sherratt. These have a) shown that birds
see the mimetic patterns of many hoverflies in a way similar to the way in which humans see them (Dittrich et al 1993);
b) demonstrated how image analysis allows a quantitative assessment of mimicry; c) suggested that current relative abundances
are far from their natural values in the absence of human habitat interference (Azmeh et al 1998); d) suggested that
‘mimics’ may actually be advertising their flight agility (and hence unprofitability), being therefore aposematic
rather than mimetic; e) analysed pattern variability and its significance (Holloway et al 2002). In a review I summarized
possible explanations of imperfect mimicry in syrphids (Gilbert 2005b). Using a neural network approach, it is possible to
dissect which components of the pattern are used by birds to classify mimics and nonmimics (see Bain et al 2007).
Now with my colleague Tom Reader and student Chris Taylor (PhD 2011-14) we are testing the multiple-model hypothesis and taking a new look at the accuracy of mimetic resemblence via image comparisons.
I collaborate with a number of workers around the world on hoverfly biology, and organize an email discussion group for promoting international collaboration.
See my related site:
Syrphid Biology Website
Rotheray GE & Gilbert F (1989)
The phylogeny and systematics of European predacious Syrphidae (Diptera) based on larval and puparial stages.
Zoological Journal of the Linnean Society 95:29-70
Gilbert F (1990)
Size, phylogeny, and life history in the evolution of specialisation in insect predators.
pp. 101- 124 in F Gilbert (ed) Insect Life Cycles: genetics, evolution and coordination Springer, London.
Gilbert F & Owen J (1990)
Size, shape, competition, and community structure in hoverflies.
Journal of animal Ecology 59: 21-39
Dittrich W, et al (1993)
Imperfect mimicry: a pigeon's perspective.
Proceedings of the Royal Society of London B 251: 195-200
Gilbert F, et al (1994)
The evolution of feeding strategies. in P Eggleton & R Vane-Wright (eds) Phylogeny and Ecology. Academic Press.
Vahed K & Gilbert F (1996)
Differences across taxa in nuptial gift size correlate with differences in sperm number and ejaculate volume in bushcrickets (Orthoptera; Tettigoniidae)
Proceedings of the Royal Society of London B 263: 1257-1263
Azmeh S, et al (1998)
Mimicry profiles are affected by human-induced habitat change.
Proceedings of the Royal Society of London B 265: 2285-2290
Gilbert F & Jervis M (1998)
Functional, evolutionary and ecological aspects of feeding-related mouthpart specializations in parasitoid flies.
Biological Journal of the Linnean Society 63: 495-535
Green PR, et al (1999)
Conditioning pigeons to discriminate among naturally lit insect specimens.
Behavioural Processes 46: 97-102
Rotheray GE & Gilbert F (1999)
Phylogeny of Palaearctic Syrphidae (Diptera): evidence from larval stages.
Zoological Journal of the Linnean Society 127: 1-112
Sadeghi H & Gilbert F (1999)
Individual variation in oviposition preference, and its interaction with larval performance in an insect predator.
Oecologia 118: 405-411
Sadeghi H & Gilbert F (2000a)
Oviposition preferences of aphidophagous hoverflies .
Ecological Entomology 25: 91-100
Sadeghi H & Gilbert F (2000b)
The effect of egg load and host deprivation on oviposition behaviour in aphidophagous hoverflies.
Ecological Entomology 25: 101-108
Sadeghi H & Gilbert F (2000c)
Suitability of different aphids as larval food for the predatory larvae of hoverflies (Diptera: Syrphidae).
Journal of animal Ecology 69: 771-784
Katzourakis A, et al (2001)
Macroevolution of hoverflies (Diptera: Syrphidae): an analysis of phylogeny and adult characters.
Journal of Evolutionary Biology 14: 219-227
Holloway G, et al (2002)
The relationship between mimetic imperfection and phenotypic variation in insect colour patterns.
Proceedings of the Royal Society of London B 269: 411-416
Ståhls G, Rotheray G, Hippa H, Muona J & Gilbert F (2003)
Phylogeny of the Syrphidae (Diptera) inferred from combined analysis of molecular and morphological characters.
Systematic Entomology 28(4):433-450
Gilbert F (2005a)
Syrphid aphidophagous predators in a food-web context.
European Journal of Entomology 120(3): 325-333
Gilbert F (2005b)
The evolution of imperfect mimicry.
pp 231-288 in MDE Fellowes, GJ Holloway & J Rohlff (eds) Insect Evolutionary Ecology. CABI, Wallingford, UK.
Bain R, et al (2007)
The key mimetic features of hoverflies through avian eyes.
Proceedings of the Royal Society of London B 274: 1949-1954
Rotheray GE & Gilbert F (2008)
Phylogenetic relationships and the larval head of the Lower Cyclorrapha (Diptera).
Zoological Journal of the Linnean Society 153: 287-323.
Rotheray GE & Gilbert F (2010)
The Natural History of Hoverflies.
Forrest Text, Ceredigion, Wales (in press)