Butterflies And Plants A Study In Coevolution Pdf

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Two related plants, C.

Visual cues are important for insects to find flowers and host plants.

Thank you for visiting nature. You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser or turn off compatibility mode in Internet Explorer. In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript. Interactions between herbivorous insects and their host plants are a central component of terrestrial food webs and a critical topic in agriculture, where a substantial fraction of potential crop yield is lost annually to pests.

BUTTERFLIES AND PLANTS: A STUDY IN COEVOLUTION

All data used in this study are from published studies or open access databases. All data for this project have been included in supplements or is drawn from published works. The Escape and Radiate Hypothesis posits that herbivorous insects and their host plants diversify through antagonistic coevolutionary adaptive radiation.

Here, with comparative phylogenetic analyses of nymphalid butterflies, we test two of these predictions: that major host switches tend to increase species diversification and that such increases will be proportional to the scope of ecological opportunity afforded by a particular novel host association.

We test several key predictions of the Escape and Radiate Hypothesis using comparative phylogenetics in nymphalid butterflies. We find that although it appears that the evolution of a few novel host associations may have caused bursts of speciation, in general, major changes in host use tend to be linked to significant decreases in butterfly species richness.

About half of the 1. How did herbivorous insects come to be so diverse? When a plant lineage evolves a new chemical defense, it escapes from its herbivores, enters a new adaptive zone, and diversifies ecologically and taxonomically. The name Escape and Radiate was introduced by Thompson Our current understanding of the Escape and Radiate Hypothesis is an extension of the basic theory of adaptive radiation Schluter, and inherits many of the same underlying assumptions. To wit, it assumes that release from constraints on diversity will cause the speciation of specialists, rather than the niche expansion of generalists Yoder et al.

Hence, it predicts that the colonization of novel host groups will increase herbivorous insect species diversity. Otherwise, the notion of coevolutionary adaptive zones becomes problematic; for example, evolving to overcome one plant species' defenses would not allow an insect population to overcome the defenses of a related plant species.

Another assumption that the Escape and Radiate Hypothesis inherits from the general theory of adaptive radiation is that adaptive zones can be saturated. Evidence for the Escape and Radiate Hypothesis is mixed. Clear evidence of phylogenetic conservatism has been found for some plant defensive chemistries e. Wink, ; currently, we lack a quantitative sense for the overall phylogenetic conservation of plant chemical defenses Agrawal, Likewise, the phylogenetic conservatism of host use varies across clades of herbivorous insects e.

The Escape and Radiate Hypothesis would seem most applicable to groups such as butterflies for which the assumptions of phylogenetic conservation of host use and defensive chemistry in at least some host groups are met. In it, he presents evidence for temporary increases in speciation rates after the evolution of a handful of major novel host associations, classified as such a priori.

To be sure, such bursts of speciation are as expected under the Escape and Radiation Hypothesis Fordyce, , but, as it stands, we do not know if such effects are typical or exceptional; the prediction that major host shifts will spur diversification has yet to be tested with statistical rigor.

We worked at two phylogenetic levels in nymphalids. First, we analyzed nymphalid genera, of which are extant. All analyses were performed in R R Core Team, First, we used Dispersal Extinction Cladogenesis DEC models to reconstruct the phylogenetic history of the use of host orders and families as in Hardy, However, simulations have shown that such an approach reconstructs ancestral host use with a strong bias toward the present and tends to infer ancestors without any hosts at all—a problem that DEC estimation avoids Hardy, In our DEC models, the host use of each extant nymphalid genus and each ancestral nymphalid node is expressed as a combination of discrete host taxa.

If this rate matrix is too large, computations are intractable. We also excluded from consideration any host family used by only one nymphalid genus. Note that this approach was not entirely inclusive and was biased against clades containing genera with especially broad host associations.

To test the predictions of the Escape and Radiate Hypothesis, we used a linear modeling approach. We first sought to explain the variation across nymphalid lineages in species diversity and diversification rates with their phylogenetic history of host use.

For these models, we had a single predictor variable. This classification allowed us to test if host gains and losses tend to boost or throttle diversity. A schematic of diversification model covariates.

Branches in purple correspond to lineages with a novel host association. Waiting times for speciation following the evolution of a novel host association are indicated with Wt x. Speciation waiting times for the sister clade are indicated with Ws x.

For each internal node in the butterfly phylogeny, we calculated the average length of the branches leading to its two immediate descendant nodes i.

We then performed the same calculation for the focal node's sister node. The difference in average waiting times between sister nodes was used as a phylogenetically independent contrast of speciation rates. The sign and magnitude of these contrasts can show us how the gains and losses of novel host associations tend to immediately affect speciation rates. In short, this is just a comparison between two sister nodes, of the average time for subsequent lineage divergence.

We calculated contrasts of extant nymphalid species richness in two ways, which we here refer to as exclusive and inclusive contrasts. For the exclusive contrasts, for each internal node in the butterfly phylogeny at which a host gain occurred, we calculated the total number of extant descendant species classified in genera that are known to continue to use the gained host.

Then, in the focal node's sister clade, we counted all of the extant species in genera that do not use the novel host. For losses, we did the inverse; we counted extant descendant species that continued to not use the lost host and compared that count to the number of the descendant species of the sister node that continue to use the lost host.

The differences between these extant diversities are a phylogenetically independent contrast of how the gains and losses of a host associations affect species diversity in the long term. For the inclusive contrasts, we compared total extant species diversities spanning each internal node; that is, we contrasted the extant diversity of a clade descended from an ancestor that gained or lost a new host, with the extant diversity of its sister clade, while ignoring whether or not extant taxa use or do not use that host See Appendix [Link] , [Link] for R scripts.

To account for genera removed from the phylogeny during DEC reconstructions of host family use, these calculations were performed on the corresponding nodes on the complete tree Wahlberg, For nodes at which no change in host use occurred, all descendants were contrasted in both the inclusive and exclusive diversity contrasts. A value of zero corresponds to a constant diversification rate.

Positive values of the gamma statistic are difficult to interpret. They could indicate that diversification rates accelerate from the root the tips, that is, there is a late burst of speciation.

Hence, Pybus and Harvey recommend that positive values are ignored. We calculated the gamma statistic for all clades comprised of at least ten nymphalid genera.

We developed four indices for the scope of the ecological opportunity opened by the evolution of a novel host association and then used these as predictor variables to try an explain changes in butterfly diversity linked to evolutionary host gains.

All else being equal—in particular rates of speciation and ecological evolution—older plant lineages should be more diverse and have provided more time for herbivore diversification.

Thus, it measures how quickly a particular butterfly lineage colonized a new host. If earlier colonizers are exposed to less competition and more open niche space, that could amount to greater ecological opportunity. By contrast some, hosts are seldom gained and lost. Colonization of such hosts may represent more novel niche transformations and greater ecological opportunities.

For the second question, we looked at the same response variables, but only for host gains, and tried to explain the variation in the response variables with several indices of the breadth of ecological opportunity afforded by a novel host group.

Two of the response variables—speciation waiting times and extant species diversities—were phylogenetically independent contrasts. Therefore, we could use standard linear modeling methods to estimate the fixed effects of the predictor variables on their variance. For these models, as is standard for models of phylogenetically independent contrasts, we forced the regression to pass through the origin. Values of the third response variable, the gamma statistic, were not phylogenetically independent.

To account for this, we fit linear mixed models in which phylogenetic relatedness between nodes was expressed using a pedigree structure and included this as a random effect with the Bayesian approach implemented in MCMCglmm Hadfield, Analyses consisted of 1,, MCMC iterations with a thinning interval of We used the Geweke diagnostic to confirm that we had sampled sufficiently from the stationary distribution see Tables S1—S16 for all model results.

Unfortunately, it is currently not feasible to fit such models to traits with as many states as host use in nymphalids. Then, for each host taxon, we compared the fit of the early burst model to a model with constant branching and extinction.

We looked only at inclusive contrasts of extant species diversity, and models explaining variation in gamma statistics were not weighted by MCCR tests. As explained above, we calculated contrasts of diversity in two ways for gains. In the first, which we refer to as exclusive contrasts, we compared the number of species in a focal clade that use a particular host group to the number of species in the sister clade that do not use that host group.

For losses, we did the inverse. In the second, which we refer to as inclusive contrasts, we compared the total extant species diversity regardless of current host use descended from an ancestor that gained a host group to the total species diversity of its sister group. To put those figures in perspective, the average summed species diversity of the focal and sister clades involved in a contrast was Note that in both cases, the estimated magnitude of the effects on diversity was greater for losses.

We found no significant effects from any of the ecological opportunity proxies on variation in extant diversities Tables S8—S Likewise, the proxies for the magnitude of ecological opportunity were mostly uncorrelated with diversity dynamics Tables S1—S8.

There was one exception; gamma statistic values were positively correlated with early adoption index values estimated coefficient: 0. For full results, see Table S For the most part, this does not seem to be the case.

We find no support for the broadest prediction that the evolution of major new host associations tends to boost herbivorous insect diversity over long phylogenetic time scales. To the contrary, we find evidence that novel associations tend to decrease extant butterfly species richness. It could be that major evolutionary changes in host use are caused by major declines in fitness on ancestral hosts. With reduced performance on ancestral hosts, and likely marginal performance on new hosts, the growth rates and effective sizes of herbivorous insect populations could shrink along with their geographic and climatic niche ranges.

This could increase the odds of extinction and decrease the odds of speciation. Thus, major evolutionary shifts in the diets of butterflies could mark ecological crashes more than ecological opportunities. Alternatively, it is possible that major new host associations are, in fact, the realization of ecological opportunities, but such opportunities do not tend to promote speciation of nymphalids in the long term.

We found evidence of early burst diversification linked to the evolution of the use of several specific plant families. This suggests that coevolutionary adaptive radiation may indeed have played a role in the diversification of herbivorous insects. The Escape and Radiate Hypothesis can also be used to predict that a novel host association should affect species diversity in a way that is proportional to the scope of ecological opportunity the new host group offers.

Two of our indices of ecological opportunity could explain some of the variation in our butterfly diversification variables. This is consistent with our assumption of emptier niche space earlier in a plant lineage's evolutionary history.

This in turn is based on the assumption that the origins of major plant clades tend to be linked to events which release plants from their previous consumers. This is consistent with our assumption that, all else being equal, older host taxa should tend to be more diverse and correspond to greater ecological opportunities.

BUTTERFLIES AND PLANTS: A STUDY IN COEVOLUTION

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Skip to search form Skip to main content You are currently offline. Some features of the site may not work correctly. DOI: Ehrlich and P. Ehrlich , P.

All data used in this study are from published studies or open access databases. All data for this project have been included in supplements or is drawn from published works. The Escape and Radiate Hypothesis posits that herbivorous insects and their host plants diversify through antagonistic coevolutionary adaptive radiation. Here, with comparative phylogenetic analyses of nymphalid butterflies, we test two of these predictions: that major host switches tend to increase species diversification and that such increases will be proportional to the scope of ecological opportunity afforded by a particular novel host association. We test several key predictions of the Escape and Radiate Hypothesis using comparative phylogenetics in nymphalid butterflies. We find that although it appears that the evolution of a few novel host associations may have caused bursts of speciation, in general, major changes in host use tend to be linked to significant decreases in butterfly species richness.

Coevolution

In biology, coevolution occurs when two or more species reciprocally affect each other's evolution through the process of natural selection. The term sometimes is used for two traits in the same species affecting each other's evolution, as well as gene-culture coevolution. Charles Darwin mentioned evolutionary interactions between flowering plants and insects in On the Origin of Species Although he did not use the word coevolution, he suggested how plants and insects could evolve through reciprocal evolutionary changes.

BUTTERFLIES AND PLANTS: A STUDY IN COEVOLUTION

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Skip to search form Skip to main content You are currently offline. Some features of the site may not work correctly. DOI: Ehrlich and P. Ehrlich , P. Raven Published Biology Evolution.

The greatest diversity of butterflies and their host plants occurs in tropical regions. Some groups of butterflies in the tropics exhibit monophagous feeding in the larval stage, exploiting only one family of plants; others are polyphagous, feeding on plants in two or more distinct families. The two major types of tropical habitats for butterflies, namely primary and secondary forests, offer very different evolutionary opportunities for the exploitation of plants as larval food. Butterflies are faced with the major logistical problem, as are many other herbivorous insects, of depositing eggs on the correct plant for successful larval feeding. This paper, using the concepts of phenotype set and spatial patchiness of resources, attemps to make some predictions as to the optimal phenotypic systems for monophagous and polyphagous feeding in tropical butterflies, as related to the spatial patchiness of larval host plants in primary and secondary forests. In addition to the secondary compound chemistry of larval host plants as playing a role in the evolution of monophagy and polyphagy, the assumption is made that the spatial patchiness of host plants within and among different families also acts as a major factor in determining optimal ranges of phenotypes for different patterns of larval feeding.

Coevolution

The suitability of several Cruciferae species for the survival and development of the larvae of Anthocharis cardamines , which are seed and flower predators, was investigated. Large differences, consistent in time and space, were observed between the survival of sub-populations on different hostplants. Foodplants influenced A. Oviposition by females appeared surprisingly maladaptive however with proportionately most eggs being laid on the hostplants yielding poorest larval survival, in opposition to previous expectations of coevolutionary theory. The evolutionary consequences of butterfly predation for Cruciferae are discussed, and juxtaposed to the needs of pollination.

Они работали. Сьюзан буквально онемела, когда эта страшная правда дошла до ее сознания. Северная Дакота - это Грег Хейл.

Девушка волокла за собой туристскую сумку. Подойдя к нему, она на этот раз расплылась в широкой улыбке. - Простите, что я на вас накричала. Я так испугалась, увидев. - Не стоит, - удивился Беккер - Я зашел куда не следовало.

BUTTERFLIES AND PLANTS: A STUDY IN COEVOLUTION

Он проявил редкую наблюдательность.

 Ein Ring, - сказал Беккер.  - Du hast einen Ring. У вас есть кольцо. - Проваливайте! - зарычал немец и начал закрывать дверь. Беккер не раздумывая просунул ногу в щель и открыл дверь.

Беккер закрыл глаза, стиснул зубы и подтянулся. Камень рвал кожу на запястьях. Шаги быстро приближались.

Его слова встретило гробовое молчание. Хейл понял, что попал в яблочко. Но невозмутимость Стратмора, очевидно, подверглась тяжкому испытанию. - Кто тебе это сказал? - спросил он, и в его голосе впервые послышались металлические нотки. - Прочитал, - сказал Хейл самодовольно, стараясь извлечь как можно больше выгоды из этой ситуации.

Она засмеялась.

1 Comments

  1. Meris C. 09.02.2021 at 19:15

    Butterflies and Plants: A Study in Coevolution. Paul R. Ehrlich; Peter H. Raven. Evolution, Vol. 18, No. 4. (Dec., ), pp. Stable URL.