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Q&A ViewAttendees 4

Systematics, Evolution, and Biodiversity

Member Symposium

Tephritidae Systematics, Diagnostics, Phylogeny, Evolution & Natural History

Host shifting and host sharing in a genus of specialist flies diversifying alongside their sunflower hosts

Tuesday, November 2, 2021
1:50 PM – 2:05 PM MT
Location: Colorado Convention Center, Meeting Room 205-207
In-Person
Among host-specific insects, it is unusual for congeners to feed on the same tissue of the same hosts, because of strong selection against niche overlap. How multiple species come to coexist on the same host may reveal insights into ecological factors underlying the origins of diversity. Sunflower maggot flies (Strauzia) are endemic to North America. Their larvae feed on the pith of sunflowers. Although Strauzia tend to be specialists, they overlap in their host use on two different sunflower species. To resolve the origins of host sharing among these flies, we used reduced-representation genomic libraries to infer a multi-locus phylogeny for genus Strauzia. Helianthus tuberosus and H. grosseserratus each harbor three different fly species. The flies using each respective host are not one another’s closest relatives. Host sharing is likely the result of host shifts, not speciation in situ. Divergence timing estimates and evidence for incomplete lineage sorting suggest that many Strauzia species may be of recent origin. Many of the plant hosts of Strauzia belong to a young (1-2 MYA) clade of perennial sunflowers noted for their frequent introgression, hybrid speciation events, and historical domestication events. This may indicate that recent adaptive introgression and speciation in a group of plants has led to rapid host-shift speciation among their phytophagous fly associates, including the convergence of multiple species on the same host plants. We explore the emergence of sexually dimorphic traits within Strauzia as a putative mechanism to avoid interspecific interactions on a shared host.