Resource specialization and ecological speciation arising through host-associated genetic differentiation (HAD) are frequently invoked as an explanation for the high diversity of plant-feeding insects and other organisms with a parasitic lifestyle. While genetic studies have demonstrated numerous examples of HAD in insect herbivores, the rarity of comparative studies means that we still lack an understanding of how deterministic HAD is, and whether patterns of host shifts can be predicted over evolutionary time scales. We applied genome-wide SNP and mtDNA sequence data obtained through genome resequencing to define species limits and to compare host-plant use in population samples of leaf- and bud-galling sawflies (Hymenoptera: Tenthredinidae: Nematinae) collected from seven shared willow (Salicaceae: Salix) host species. To infer the repeatability of long-term cophylogenetic patterns, we also contrasted the phylogenies of the two galler groups with each other as well as with the phylogeny of their Salix hosts estimated based on RADseq data. We found clear evidence for host specialization and HAD in both of the focal galler groups, but also that leaf gallers are more specialized to single host species than are most bud gallers. In contrast to bud gallers, leaf gallers also exhibited statistically significant cophylogenetic signal with their Salix hosts. The observed discordant patterns of resource specialization and host shifts in two related galler groups that have radiated in parallel across a shared resource base indicate a lack of evolutionary repeatability in the focal system, and suggest that short- and long-term host use and ecological diversification in plant-feeding insects are dominated by stochasticity and/or lineage-specific effects.
|Original language||English (US)|
|State||Published - Jan 10 2023|
Bibliographical noteKAUST Repository Item: Exported on 2023-01-13
Acknowledgements: Funding for this study was provided by the Academy of Finland (Project 294466 to TN).Computation-intensive bioinformatic and statistical analyses were performed on the servers of the Finnish Centre for Scientific Computing (www.csc.fi). Jens-Peter Kopelke kindly provided photographs of bud galls on S. myrsinifolia and S. hastata. This manuscript benefited from discussions with Catherine Linnen and P hillip Watts, as well as from suggestions provided by six anonymous reviewers.
ASJC Scopus subject areas
- Ecology, Evolution, Behavior and Systematics