Gall Flies, Inquilines, and Goldenrods: A Model for Host-race Formation and Sympatric Speciation

Host shifts and subsequent host-race formation likely play a more common role in the speciation of herbivorous insects than has generally been recognized. Our studies of the interactions of goldenrod host plants (Solidago: Compositae), the gall fly Eurosta solidaginis (Diptera: Tephritidae), and the...

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Bibliographic Details
Published in:American zoologist 2001-09, Vol.41 (4), p.928-938
Main Authors: Abrahamson, Warren G., Eubanks, Micky D., Blair, Catherine P., Whipple, Amy V.
Format: Article
Language:English
Subjects:
An Integrative Approach to the Study of Terrestrial Plant-Animal Interactions
Beetles
Biodiversity
Ecological genetics
Genetics
Host plants
Insect ecology
Insect genetics
Insects
Larvae
Parasite hosts
Phytophagous insects
Plant gall
Speciation
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Summary:Host shifts and subsequent host-race formation likely play a more common role in the speciation of herbivorous insects than has generally been recognized. Our studies of the interactions of goldenrod host plants (Solidago: Compositae), the gall fly Eurosta solidaginis (Diptera: Tephritidae), and the stem- and gall-boring Mordellistena convicta (Coleoptera: Mordellidae) provide behavioral, ecological, and genetic evidence of insect host races that may represent incipient species formed via sympatric speciation. Eurosta solidaginis has developed genetically differentiated and reproductively isolated host races that are associated with the ancestral host Solidago altissima and the derived host S. gigantea. Conventional wisdom suggests that shifts even to closely related host plants are limited by host preferences or the inability to utilize a chemically and developmentally distinct host. However, our preliminary work with Eurosta from S. gigantea implies that host choice and gall induction do not deter a shift to S. canadensis. The galling of Solidago by Eurosta created a new resource that has led to a subsequent host range expansion by the stem-boring beetle. Mordellistena convicta from stems and galls are genetically distinct and likely shifted from stems to galls. Beetles from S. altissima versus S. gigantea galls exhibit assortative mating and higher preference for and/or performance on their natal host. The present-day distributions of the Eurosta host races and their behavioral isolating mechanisms do not suggest that geographic isolation was required for their formation; rather these characteristics suggest a sympatric mode of differentiation. Our findings lend credence to recent assertions that sympatric speciation may be an important source of biodiversity.
ISSN:1540-7063
0003-1569
1557-7023
2162-4445
DOI:10.1093/icb/41.4.928