The Evolution of Host Specialization: Are Trade-Offs Overrated?

Fry, James D.

doi:10.1086/285904

Cited by 374 publications

(400 citation statements)

References 34 publications

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“…different sexes or different environments) is a genetic correlation of one [13,14]. Genetic correlations less than one will allow some degree of independent evolution, and even small deviations from a correlation of one can allow evolutionary change towards multiple optima [13,14]. The same logic can be applied to quantitative genetic studies of associations across metamorphosis-for traits measured pre-and post-metamorphosis, a genetic correlation across metamorphosis significantly less than one would suggest that independent evolution across metamorphosis is possible.…”

Section: Introductionmentioning

confidence: 98%

The genetic covariance between life cycle stages separated by metamorphosis

2014

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Metamorphosis is common in animals, yet the genetic associations between life cycle stages are poorly understood. Given the radical changes that occur at metamorphosis, selection may differ before and after metamorphosis, and the extent that genetic associations between pre-and post-metamorphic traits constrain evolutionary change is a subject of considerable interest. In some instances, metamorphosis may allow the genetic decoupling of life cycle stages, whereas in others, metamorphosis could allow complementary responses to selection across the life cycle. Using a diallel breeding design, we measured viability at four ontogenetic stages (embryo, larval, juvenile and adult viability), in the ascidian Ciona intestinalis and examined the orientation of additive genetic variation with respect to the metamorphic boundary. We found support for one eigenvector of G (g obs max ), which contrasted larval viability against embryo viability and juvenile viability. Target matrix rotation confirmed that while g obs max shows genetic associations can extend beyond metamorphosis, there is still considerable scope for decoupled phenotypic evolution. Therefore, although genetic associations across metamorphosis could limit that range of phenotypes that are attainable, traits on either side of the metamorphic boundary are capable of some independent evolutionary change in response to the divergent conditions encountered during each life cycle stage.

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Section: Introductionmentioning

confidence: 98%

The genetic covariance between life cycle stages separated by metamorphosis

2014

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“…From an evolutionary perspective, selection for higher or lower levels of host specificity (or, in a broader sense, ecological specialization) is affected by a variety of both parasite (=forager)-related and host (=resource)-related factors (Fox and Morrow, 1981 ;Futuyama and Moreno, 1988 ;Fry, 1996 ;Desdevises et al 2002). In particular, the models of Ward (1992) suggested that species tend to specialize on predictable resources, i.e.…”

Section: Introductionmentioning

confidence: 99%

Resource predictability and host specificity in fleas: the effect of host body mass

et al. 2006

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Ecological specialization is hypothesized to result from the exploitation of predictable resource bases. For parasitic organisms, one prediction is that parasites of large-bodied host species, which tend to be long-lived, should specialize on these hosts, whereas parasites of small host species, which represent more ephemeral and less predictable resources, should become generalists. We tested this prediction by quantifying the association between the level of host specificity of fleas and the mean body mass of their mammalian hosts, using published data from 2 large, distinct geographical regions (South Africa and northern North America). In general, we found supporting evidence that flea host specificity, measured either as the number of host species exploited or their taxonomic distinctness, became more pronounced with increasing host body mass. There were, however, some discrepancies among the results depending on the different measures of host specificity, the geographical region studied, or whether we used the raw values or phylogenetically independent contrasts. These are discussed with respect to other forces acting on the evolution of host specificity in parasites, as well as in the context of the regions' contrasting evolutionary histories. Overall, though, our findings indicate that the exploitation of large-bodied, and therefore long-lived, host species has promoted specialization in fleas, most likely because these hosts represent predictable resources.

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“…It exploited interspecific variation in habitat specialization, and it tested for trade-offs under natural conditions. Most previous studies have examined trade-offs within species, among clones or host races, under artificial conditions or following artificial selection for specialization (Futuyma & Moreno 1988;Rauscher 1988;Jaenike 1990;Via 1990;Fry 1996;Van Tienderen 1997;Kassen & Bell 1998). Although the search for tradeoffs with host specialization has largely failed, it may be premature to abandon the 'jack of all trades is master of none' model of habitat specialization given our results.…”

Section: Discussionmentioning

confidence: 83%

“…The main effects of habitat and specialization were analysed as fixed effects, and goby (specialization) as a random effect. Therefore, the main effect specialization was tested over a synthesized mean square (MS synthesized = 0.774(goby species(specialization)) ϩ 0.226 × (residual) (Futuyma & Moreno 1988;Jaenike 1990;Via 1990;Fry 1996;Kassen & Bell 1998). Why, then, were these trade-offs evident here?…”

Section: Discussionmentioning

confidence: 99%

Growth trades off with habitat specialization

Caley

Munday

2003

Proc. R. Soc. Lond. B

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How differences in niche breadth evolve and are maintained remains largely unknown. The 'jack of all trades is master of none' model of resource specialization has been widely considered, but, to our knowledge, never before supported empirically. It invokes performance trade-offs associated with specialization. Specialists should outperform generalists on a subset of resources, but be unable to maintain high performance over a broader range of resources. By contrast, generalists should perform less well, on average, using a greater diversity of resources. We report such trade-offs among four coral goby species in the wild. Habitat specialists grew faster than generalists in one of two habitats. Average growth rates of generalists were less than that of specialists, but more consistent between habitats. Performance trade-offs associated with resource specialization could influence the evolution and maintenance of narrow niche breadth.

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The Evolution of Host Specialization: Are Trade-Offs Overrated?

Cited by 374 publications

References 34 publications

The genetic covariance between life cycle stages separated by metamorphosis

The genetic covariance between life cycle stages separated by metamorphosis

Resource predictability and host specificity in fleas: the effect of host body mass

Growth trades off with habitat specialization

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