What determines host range in parasitoids? An analysis of a tachinid parasitoid community

Abstract

Despite the vast diversity of parasitic insects and their importance in natural and agricultural communities, our knowledge of what determines their patterns of association with hosts remains sparse. Unlike most parasites that tend to be specialized, parasitoid flies in the family Tachinidae exhibit a broad spectrum of host-specificity, with many species attacking a wide range of hosts. This variability in host-specificity makes them a useful model for examining the ecological and historical factors that determine host associations. We analyzed data collected from a 5-year rearing program of Lepidoptera in southern Arizona to investigate the factors that influence tachinid-host associations. After controlling for a strong effect of sample size, a significant portion of the remaining variance in host range was explained by differences among phylogenetic groups of tachinids and/or their correlated reproductive strategies. Relatively specialized tachinids tended to be associated with monophagous or narrowly oligophagous hosts and attacked them at relatively high frequencies, a pattern we suggest is related to host location efficiency. Cluster analysis indicated that host abundance, gregariousness, food-plant type, and morphology are all important determinants of tachinid host use. Little concordance was found between how tachinid species cluster according to characteristics of their hosts and their estimated phylogenetic relationships. Together, the results of this study suggest that ecological factors are important determinants of host use in these parasitoids and although phylogenetic history may influence the range of hosts used, its power to explain the ecological or taxonomic character of hosts used appears limited.

DNA barcodes affirm that 16 species of apparently generalist tropical parasitoid flies (Diptera, Tachinidae) are not all generalists

“…Reviews of the nature of tachinid host use have concluded that, as a whole, the family is generalist, and most variation on this pattern is due to a small subset of even more extremely generalist species (33). However, this conclusion is based almost entirely on host records from temperate regions and on generalist ''species'' as defined by their morphology.…”

Host specialist clownfishes are environmental niche generalists

“…with broadly overlapping diets explains the coexistence of generalist herbivores in nature [11]. While this suggests that multiple generalist-specialist coexistence patterns can emerge in heterogeneous systems [9], the evolutionary processes involved in specialization are inevitably more complex when two or more resource dimensions influence the coexistence of species [12].…”

Specificity and Specialization of Congeneric Monogeneans Parasitizing Cyprinid Fish

“…Host specificity has often been mentioned as a factor associated with adaptive specialization (Timms and Read 1999). Several attempts have been made to explain the patterns and processes of host specificity in different groups of parasites or parasitoids (see for instance Jaenike 1990;Poulin 1998;Š imková et al 2001a;Stireman and Singer 2003).…”