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PubMed2006

Modulation and variability of prey capture kinematics in clariid catfishes.

Species with narrow or limited diets (trophic specialists) are expected to be less flexible in their feeding repertoire compared to species feeding on a wide range of different prey (trophic generalists). The ability to modulate prey capture kinematics in response to different prey types and prey position, as well as the overall variability in prey capture kinematics, is evaluated in four clariid species ranging from trophic generalist (Clarias gariepinus) to species with morphological specializations and a narrow diet (Channallabes apus and Gymnallabes typus). High-speed video recordings were made of prey captures on two prey that differ in shape, attachment strength and hardness. While the observed amount of strike-to-strike variability in prey capture kinematics is similar for all species and not influenced by prey type, only the two less specialized species showed the ability to modulate their prey capture kinematics in function of the presented prey types. All species did, however, show positional modulation during the strike by adjusting the magnitude of neurocranial elevation. These results indicate that the narrow dietary breadth of trophic specialists is indeed indicative of functional stereotypy in this group of fishes. Although most studies focussing on prey processing found a similar result, the present study is one of the few that was able to demonstrate this relationship when focussing on prey capture mechanics. Possibly, this relationship is less frequently observed for prey capture compared to prey processing because, regardless of prey type, the initial capture of prey requires a higher amount of variability.

Animals↗
PubMed2001

Inter-observer variation between general and specialist gastrointestinal pathologists when grading dysplasia in ulcerative colitis.

Histological dysplasia is the cornerstone of colorectal cancer surveillance in ulcerative colitis (UC). Recently, pathologists have received unfavourable media attention concerning other cancer screening programmes. The aim of this study was to determine whether colonic biopsy specimens should be examined by gastrointestinal pathologists as opposed to generalists, by examining inter-observer variation between the two groups. Fifty-one coded slides showing varying degrees of dysplasia were mailed to seven gastrointestinal and six general histopathologists. Pathologists allocated each biopsy into one of four categories without the benefit of a clinical history or an opportunity to use the 'indefinite' category that is included in the Riddell classification. The responses were analysed using kappa statistics. The overall kappa statistic for gastrointestinal pathologists was 0.30 [95% confidence interval (CI)=0.26-0.34] and for general pathologists 0.28 (95% CI=0.23-0.32). Agreement was best for high-grade dysplasia (kappa of 0.54 and 0.61 for GI and general pathologists, respectively). There was total concordance of the 13 pathologists in only four of the 51 slides (7.8%) (95% CI=0.4-15.2%). It is concluded from these results that gastrointestinal pathologists are no better than generalists when grading dysplasia in UC and that agreement is poor in both groups. There is therefore no evidence that there would be any benefit in having specialist histopathology centres concentrating specifically on the interpretation of all surveillance colonoscopy biopsies from around the UK. It must be made clear to the public that surveillance and screening programmes carry a significant rate of histological error and that perfection cannot be expected or achieved with present methods.

Colitis, Ulcerative↗
PubMed2001

Effects of habitat destruction and resource supplementation in a predator-prey metapopulation model.

We developed a mean field, metapopulation model to study the consequences of habitat destruction on a predator-prey interaction. The model complements and extends earlier work published by Bascompte and Solé (1998, J. theor. Biol.195, 383-393) in that it also permits use of alternative prey (i.e., resource supplementation) by predators. The current model is stable whenever coexistence occurs, whereas the earlier model is not stable over the entire domain of coexistence. More importantly, the current model permits an assessment of the effect of a generalist predator on the trophic interaction. Habitat destruction negatively affects the equilibrium fraction of patches occupied by predators, but the effect is most pronounced for specialists. The effect of habitat destruction on prey coexisting with predators is dependent on the ratio of extinction risk due to predation and prey colonization rate. When this ratio is less than unity, equilibrial prey occupancy of patches declines as habitat destruction increases. When the ratio exceeds one, equilibrial prey occupancy increases even as habitat destruction increases; i.e., prey "escape" from predation is facilitated by habitat loss. Resource supplementation reduces the threshold colonization rate of predators necessary for their regional persistence, and the benefit derived from resource supplementation increases in a nonlinear fashion as habitat destruction increases. We also compared the analytical results to those from a stochastic, spatially explicit simulation model. The simulation model was a discrete time analog of our analytical model, with one exception. Colonization was restricted locally in the simulation, whereas colonization was a global process in the analytical model. After correcting for differences between nominal and effective colonization rates, most of the main conclusions of the two types of models were similar. Some important differences did emerge, however, and we discuss these in relation to the need to develop fully spatially explicit analytical models. Finally, we comment on the implications of our results for community structure and for the conservation of prey species interacting with generalist predators.

Animals↗
PubMed1996

Optimal Level of Chemical Defense Decreasing with Leaf Age

A recent study on a biennial plant demonstrated that pyrrolizidine alkaloids decrease with the age of leaves due to reallocation from old leaves to new leaves. Here we study the optimal age-specific pattern of defense chemical concentration in leaves that achieves the maximum growth rate of the plant. We consider a plant growing exponentially in a constant environment. Assumptions are the following: (1) The loss of leaves due to herbivory decreases with defense chemical concentration (2) The daily net photosynthesis of a leaf decreases with its age. (3) Using photosynthetic products, the plant produces new leaves that may contain defense chemicals. (4) Although there is a cost to producing new defense chemicals, such chemicals can be reallocated without cost. In the optimal schedule calculated using Pontryagin's maximum principle, the chemical defense level decreases with leaf age. The optimal level of chemical defense increases with the cost of leaf production and herbivory intensity but decreases with the cost of defense chemical production, effectiveness of the defense chemical, net productivity, and growth rate of the plant. If both generalist and specialist herbivores attack the same plant, the optimal defense level is dependent only on the generalists' abundance and sensitivity, but is independent of the specialists that are unaffected by the defense chemical.

Journal Article↗
PubMed1995

Host-seeking behaviour by Australian ticks (Acari: Ixodidae) with differing host specificities.

Ticks generally detach from their hosts into sites where they are later exposed to host species which may or may not be suitable for infestation. The question of how four species of ixodid ticks, with differing specificities, behave towards such potential host species was examined. Observations of the generalists, Aponomma hydrosauri and Amblyomma limbatum and the specialists, Aponomma fimbriatum and Aponomma concolor, showed that the generalists were attracted to a wider range of potential host species than the specialists and that the larval stages of all tick species, regardless of specificity, contacted more potential host species than the adults. The interspecific differences may be attributed to reliance on different sets of host cues, while the intraspecific differences may reflect the developmental state of the sensory system.

Animals↗
PubMed1998

The practice of general internal medicine by subspecialists.

To determine the proportion of specialists in internal medicine at a university medical center practicing general internal medicine in addition to their specialty, full-time and voluntary faculty were asked to complete a questionnaire concerning their practice patterns. In addition, the directories of two of the largest managed-care groups in the area were reviewed to identify physicians who were also faculty members, to determine whether faculty in these directories self-identified as general internists. Excluding those with primary research appointments, 303 faculty in the Department of Medicine were asked to participate. Of these, 187 (62%) responded, of whom 86 (46%) were full-time and 101 (54%) voluntary faculty. Of the respondents, 183 (98%) were either board certified (152; 81%) or board eligible (31; 17%) in a subspecialty. Both general internal medicine and specialty medicine were practiced by 116 (65%), with full-time faculty being more likely to have solely subspecialty practices (P < .001). The majority of faculty (150; 80%) participated in managed care. A review of directories of two managed-care groups revealed that 100 (87%) of the 115 faculty with appointments within subspecialty divisions of the Department of Medicine were listed as general internists. Subspecialists in internal medicine already spend considerable time practicing general medicine and are increasingly willing to identify themselves as generalists. Unless this is recognized, the future need for generalists may be overestimated considerably.

Hospitals, University↗
PubMed1994

Faculty--agents of change.

In medical schools and residencies, the faculty in all settings and through all facets of the curriculum influence learners' skills, attitudes, and behaviors. Mentorship and role modeling are powerful forces in shaping a professional. To positively affect the number of students seeking to enter the generalist specialties, the faculty community will need reevaluation, expansion, and professional development. This paper discusses some of the hurdles for institutional leaders and offers pragmatic suggestions for beginning the process of retooling the faculty. A matrix is presented to describe the multifaceted faculty required for educating the generalist.

Adult↗
PubMed2002

Assessing habitat utilization by neotropical primates: a new approach.

This study aims to ascertain habitat utilization, in relation to forest structural variation, by a multi-species group of primates in tropical lowland rainforest in Southeast Peru during dry season. A new approach to assessing habitat utilization was used. Habitat variation was described by structural and indicator variables collected in quadrats along transects through a study area within Terra Firme and Floodplain forest. Variables were grouped into 'factors' accounting for most of the variation by means of a Principal Components Analysis (PCA). Presence or absence of the primates within the quadrats, assessed by repeat transect surveys, was taken to indicate habitat preferences. Discrimination between the habitat and forest structure in areas of primate presence as opposed to absence was carried out by means of Discriminant Function Analysis (DFA). This highlighted patterns in most utilized habitat. Vertical utilization of the forest was also assessed along with presence in bamboo and general activity on encounter. Suggestions of habitat preference and utilization are made for each of the six sympatric species studied, based on significantly discriminating habitat factors, vertical stratification on encounter and relationships with bamboo. Saguinus fuscicollis and Cebus moloch appeared as habitat generalists. Cebus apella, Saimiri sciureus, and Aotus spp., exhibited varying degrees of preference for habitat factors suggesting disturbed forest, Cebus albifrons was more generalistic but with a possible association with primary, naturally disturbed forest. C. apella was encountered in Terra Firme forest significantly more than in Floodplain. For S. sciureus, C. moloch, and C. apella, upper understory was the most utilized forest layer, for C. albifrons, middle canopy and for S. sciureus and Aotus spp., lower understory. Both positive and negative relationships with bamboo were highlighted. Significant positive relationships between Aotus spp., and bamboo suggest dense bamboo stands provide important daytime resting sites for this nocturnal species. C. moloch was also shown to utilize bamboo whereas S. fuscicollis appeared to actively avoid it. High levels of conformity with past studies in terms of habitat utilization patterns described for the species studied supports the conclusion that the methods used in this study provide an effective means of assessing primate habitat utilization within complex habitat.

Animals↗
PubMed2002

Evidence for regulation of resistance in Arabidopsis to Egyptian cotton worm by salicylic and jasmonic acid signaling pathways.

Signaling cross-talk between wound- and pathogen-response pathways influences resistance of plants to insects and disease. To elucidate potential interactions between salicylic acid (SA) and jasmonic acid (JA) defense pathways, we exploited the availability of characterized mutants of Arabidopsis thaliana (L.) Heynh. and monitored resistance to Egyptian cotton worm (Spodoptera littoralis Boisd.; Lepidoptera: Noctuidae). This generalist herbivore is sensitive to induced plant defense pathways and is thus a useful model for a mechanistic analysis of insect resistance. As expected, treatment of wild-type Arabidopsis with JA enhanced resistance to Egyptian cotton worm. Conversely, the coil mutant, with a deficiency in the JA response pathway, was more susceptible to Egyptian cotton worm than wild-type Arabidopsis. By contrast, the nprl mutant, with defects in systemic disease resistance, exhibited enhanced resistance to Egyptian cotton worm. Pretreatment with SA significantly reduced this enhanced resistance of nprl plants but had no influence on the resistance of wild-type plants. However, exogenous SA reduced the amount of JA that Egyptian cotton worm induced in both npr1 mutant and wild-type plants. Thus, this generalist herbivore engages two different induced defense pathways that interact to mediate resistance in Arabidopsis.

Animals↗
PubMed2002

Abundance-prevalence relationship of gill congeneric ectoparasites: testing the core satellite hypothesis and ecological specialisation.

We investigated the abundance-prevalence relationships in monogeneans belonging to the genus Dactylogyrus. A total of 182 dactylogyrid populations representing nine species were collected from the gills of roach ( Rutilus rutilus). Local abundance was found to be strongly positively correlated with prevalence. Two hypotheses were tested to explain this relationship: (1) the core-satellite hypothesis, and (2) the ecological specialisation hypothesis. Abundance was log-normally distributed, and the relationship between mean abundance and variance of abundance followed Taylor's power law prediction. Prevalence showed a negative binomial distribution, which does not confirm the core-satellite hypothesis. The positive relationship between abundance and prevalence was found for both specialists and generalists. However, generalists were found to be more widely distributed among hosts and had higher abundances than specialists, which supports the ecological specialisation hypothesis.

Animals↗
PubMed2000

Parasite communities of the Salzhaff (Northwest Mecklenburg, Baltic Sea) II. Guild communities, with special regard to snails, benthic crustaceans, and small-sized fish.

Metazoan parasites of guilds of benthic snails and crustaceans and of four fish families--Gobiidae, Gasterosteidae, Syngnathidae, and Zoarcidae--were investigated off the brackish Salzhaff area (Southwest Baltic) in the semienclosed Salzhaff and the near Rerik Riff in the free Baltic. Comparisons revealed greater similarities in parasite populations and communities within the fish guilds than between them. According to an evaluation of the core-/satellite-species concept using abundance values, the most important parasites of fish were some generalists, such as Cryptocotyle spp., Podocotyle atomon, and Diplostomum spathaceum, as well as some specialists, such as Acanthostomum balthicum, Thersitina gasterostei, and Aphalloides timmi. These specialists revealed high degrees of prevalence in their main hosts and lower degrees in one or two by-hosts. Additional importance is assigned to parasites that cause harm to their hosts due to their large size, e.g., Schistocephalus spp., or via massive infestation, e.g., several digenean metacercariae. Because specialists were more prominent in snails and fish from the Rerik Riff, the correlation of host numbers with prevalence resulted in only a slight increase instead of a more rapid rise in regression among crustaceans and fish from the entire Salzhaff, where the generalists were more prevalent. The selected host guilds demonstrated the entire life cycles of three digeneans (P. atomon, A. balthicum, A. timmi), one acanthocephalan (Echinorhynchus gadi), and one nematode (Hysterothylacium sp.). The prevalence increased in these cycles from host level to host level and attained relatively high values in all guilds. The parasite fauna of the Salzhaff area is influenced by eutrophication stress, which leads to a high level of productivity and, consequently, to great densities in primary consumers such as snails and crustaceans. These are attractive for several secondary consumers such as fish and birds, which is the reason for the existence of at least 24 autogenic and 20 allogenic parasite species at this locality. The slight surplus of the first category indicates a yet-balanced environment in the investigation area.

Animals↗
PubMed2004

Plant chemical defense against herbivores and pathogens: generalized defense or trade-offs?

Plants are often attacked by multiple enemies, including pathogens and herbivores. While many plant secondary metabolites show specific effects toward either pathogens or herbivores, some can affect the performance of both these groups of natural enemies and are considered to be "generalized defense compounds". We tested whether aucubin and catalpol, two iridoid glycosides present in ribwort plantain (Plantago lanceolata), confer in vivo resistance to both the generalist insect herbivore Spodoptera exigua and the biotrophic fungal pathogen Diaporthe adunca using plants from P. lanceolata lines that had been selected for high- and low-leaf iridoid glycoside concentrations for four generations. The lines differed approximately three-fold in the levels of these compounds. Plants from the high-selection line showed enhanced resistance to both S. exigua and D. adunca, as evidenced by a smaller lesion size and a lower fungal growth rate and spore production, and a lower larval growth rate and herbivory under both choice and no-choice conditions. Gravimetric analysis revealed that the iridoid glycosides acted as feeding deterrents to S. exigua, thereby reducing its food intake rate, rather than having post-ingestive toxic effects as predicted from in vitro effects of hydrolysis products. We suggest that the bitter taste of iridoid glycosides deters feeding by S. exigua, whereas the hydrolysis products formed after tissue damage following fungal infection mediate pathogen resistance. We conclude that iridoid glycosides in P. lanceolata can serve as broad-spectrum defenses and that selection for pathogen resistance could potentially result in increased resistance to generalist insect herbivores and vice versa, resulting in diffuse rather than pairwise coevolution.

Adaptation, Physiological↗
PubMed2004

Lichen palatability depends on investments in herbivore defence.

Lichens are well-suited organisms for experimental herbivory studies because their secondary compounds, assumed to deter grazing, can be non-destructively extracted. Thalli of 17 lichen species from various habitats were cut in two equal parts; compounds were extracted from one part by acetone, the other served as a control. These two pieces were offered as a paired choice to the generalist herbivore snail Cepaea hortensis. Control thalli of all lichens were consumed at a low rate regardless of their investments in acetone-extractable lichen compounds; naturally compound-deficient lichen species were not preferred compared to those with high contents. However, for extracted thalli, there was a highly significant positive correlation between rate of consumption and the extracted compound contents. These data imply that herbivore defence has evolved in different directions in different lichens. Studied members of Parmeliaceae, common in oligotrophic habitats, have high contents of carbon-rich acetone-soluble compounds; these lichens became highly palatable to snails subsequent to acetone rinsing. Extracted lichen compounds were applied to pieces of filter paper and fed to snails. Extracts from members of the Parmeliaceae significantly deterred feeding on paper. Such data suggest that generalist herbivores may have shaped evolution in the widespread and highly diverse Parmeliaceae towards high investments in lichen compounds. On the other hand, lichens belonging to the Physciaceae and Teloschistales, common in nutrient-enriched habitats, are deficient in, or have low concentrations of, lichen compounds. Such lichens did not become more palatable after acetone rinsing. The orange anthraquinone compound parietin, restricted to the Teloschistales, and which has previously been found to protect against excess light, did not deter grazing.

Acetone↗
PubMed2005

Hearing in fishes under noise conditions.

Our current knowledge on sound detection in fishes is mainly based on data acquired under quiet laboratory conditions. However, it is important to relate auditory thresholds to background noise in order to determine the signal-detecting abilities of animals in the natural environment. We investigated the influence of two noise levels within the naturally occurring range on the auditory sensitivity of two hearing specialists (otophysines) and a hearing generalist. Audiograms of the goldfish Carassius auratus, the lined Raphael catfish Platydoras costatus and the pumpkinseed sunfish Lepomis gibbosus (hearing generalist) were determined between 200 and 4000 Hz (100-800 Hz for L. gibbosus) under laboratory conditions and under continuous white noise by recording auditory evoked potentials (AEPs). Baseline thresholds showed greatest hearing sensitivity around 500 Hz in goldfish and catfish and at 100 Hz in the sunfish. Continuous white noise of 110 dB RMS elevated the thresholds by 15-20 dB in C. auratus and by 4-22 dB in P. costatus. White noise of 130 dB RMS elevated overall hearing thresholds significantly in the otophysines by 23-44 dB. In the goldfish, threshold did not shift at 4 kHz. In contrast, auditory thresholds in the sunfish declined only at the higher noise level by 7-11 dB. Our data show that the AEP recording technique is suitable for studying masking in fishes, and that the occurrence and degree of the threshold shift (masking) depend on the hearing sensitivity of fishes, the frequency, and noise levels tested. The results indicate that acoustic communication and orientation of fishes, in particular of hearing specialists, are limited by noise regimes in their environment.

Acoustic Stimulation↗
PubMed2001

Dermatologists and allergists have far more experience and use more complex treatment regimens in the treatment of atopic dermatitis than other physicians.

BACKGROUND: Atopic dermatitis (AD) is a prevalent skin condition, especially in the pediatric population. Whereas it has been shown that dermatologists prefer using more intensive therapy for AD than generalists, actual drug utilization has not been quantified. OBJECTIVE: The purpose of this study is to characterize visits for and treatment of AD in the office-based setting. METHODS: National Ambulatory Medical Care Survey data from 1990 to 1997 was analyzed to determine the use of topical corticosteroids (including their relative potencies), oral antibiotics, and oral antihistamines in the treatment of AD. RESULTS: There were an estimated 900,000 outpatient visits per year for AD. If in some visits to generalists the diagnosis for AD was miscoded as contact dermatitis, there may have been as many as 3 million outpatient visits per year for AD. Topical corticosteroids were used in 67% of visits with a mean potency rank of 4.5 (4.3, 4.8 95% CI). Dermatologists saw 48% of all visits for AD (63 yearly visits/physician) and allergists saw 10% of visits (30 yearly visits/physician). Other physicians saw from 0.1 to 2 yearly visits per physician. Dermatologists were the most likely to use topical corticosteroids (81% of visits) and high-potency corticosteroid agents (22% of visits). Dermatologists and allergists were the only physicians to prescribe ultrahigh-potent corticosteroid agents (12% and 9% of visits, respectively) and were more likely than other physicians to use multiple-agent regimens (21% and 27% of visits treated with a corticosteroid agent, respectively). CONCLUSIONS: Dermatologists and allergists have more expertise in the management of AD than other physicians, as suggested by their higher per capita visits and greater use of complex topical corticosteroid regimens.

Administration, Topical↗
PubMed2006

Role of the lipoxygenase/lyase pathway of host-food plants in the host searching behavior of two parasitoid species, Cotesia glomerata and Cotesia plutellae.

To elucidate the role of the plant lipoxygenase (LOX)/lyase pathway for host search behavior of two parasitic wasps attacking herbivorous larvae, an Arabidopsis mutant (all84) was isolated with a mutation somewhere in the LOX/lyase pathway. Detached leaves of the mutant were shown to release less (Z)-3-hexenal, a first green leaf volatile (GLV) product of the LOX/lyase pathway. The braconid larval parasitoids studied, Cotesia glomerata and Cotesia plutella, differ in their ability to discriminate among plant volatiles induced by feeding of lepidopteran hosts and nonhosts: C. plutella only responds to plant volatiles induced by hosts (Plutella larvae), whereas the response by the more generalist C. glomerata is not host specific. The Arabidopsis mutant all84 infested by Pieris larvae was less attractive to C. glomerata than Arabidopsis wild type (wt) infested by the host larvae. C. glomerata was attracted by two of the GLV biosynthesized through the LOX/lyase pathway, (E)-2-hexenal and (Z)-3-hexenyl acetate. However, attraction of C. plutellae to volatiles from Plutella-infested all84 plants did not differ from attraction to host-infested wt Arabidopsis. Both wasp species were arrested to the respective host-infested edge of the wt leaf by showing characteristic antennal searching behavior on the edge. In C. glomerata, the duration of this searching behavior at the infested leaf edge was significantly shorter on all84 plants than on wt plants. By contrast, the duration of the searching behavior of C. plutellae on the host-infested leaf edge of all84 was not significantly different from that on the wt leaf. These data suggest that the LOX/lyase pathway is directly involved in the production of attractants and arrestants important for host search behavior of the more generalist C. glomerata, but not for the specialist C. plutellae.

Animals↗
PubMed2006

Is alpha-pinene a substrate for permeability-glycoprotein in wood rats?

alpha-Pinene is the dominant monoterpene in Juniperus monosperma. Wood rat species in the genus Neotoma that consume J. monosperma vary in their inclusion of it in their wild diet and in their tolerance of whole J. monosperma or alpha-pinene in laboratory feeding trials. A proposed mechanism for variable tolerance is a difference in absorption of alpha-pinene from the small intestine that is mediated by the intestinal transporter permeability glycoprotein (Pgp). To determine if alpha-pinene is a Pgp substrate, we tested whether it can competitively inhibit Pgp and thereby increase the accumulation of a known Pgp substrate (digoxin) in (1) everted sleeves of small intestine from Neotoma stephensi, a juniper specialist, N. albigula, a sympatric generalist that consumes juniper, N. cinerea, a more distantly related generalist, and Sprague-Dawley rats, and (2) in Caco-2 cells that over express Pgp. We also measured Pgp ATPase phosphate production in transfected insect membrane vesicles exposed to alpha-pinene. We found no significant increase in digoxin accumulation with competitive inhibition experiments, and no increase in phosphate production with transfected membranes, at any concentration of alpha-pinene up to 100 muM. To test whether other compounds in juniper affect Pgp activity, we acclimated five N. stephensi to a juniper diet for 5 d, but found no significant effect compared to animals on control diet. Our data suggest that alpha-pinene is not a Pgp substrate.

Animals↗
PubMed2007

De novo synthesis vs. sequestration: negatively correlated metabolic traits and the evolution of host plant specialization in cyanogenic butterflies.

Larvae of Heliconius butterflies (Nymphalidae: Heliconiinae) feed exclusively on cyanogenic leaves of Passiflora (passion vine). Most Heliconius manufacture cyanogenic glycosides (cyanogens) and some species sequester cyanogens from host plants. We compare ability to sequester simple monoglycoside cyclopentenyl (SMC) cyanogens and manufacture aliphatic cyanogens in 12 Heliconius species, including larvae that are specialized (single host species) and generalized (many host species). All butterflies tested higher for cyanide concentrations when reared on plants that larvae can sequester from (SMC plants) than when reared on plants that larvae do not sequester from (non-SMC plants). Specialists in the sara-sapho clade sequestered SMC cyanogens from specific host plants at seven times that of Passiflora generalists fed the same hosts. In contrast, sara-sapho clade species reared on non-SMC plants had significantly lower cyanide concentrations from de novo synthesis than generalists fed the same plants. Furthermore, cyanogen analyses indicated that Heliconius sara butterflies reared on an SMC host had a greater proportion of sequestered SMC cyanogens (95.0%) than de novo-synthesized aliphatic cyanogens (5.0%). Thus, sequestration and de novo synthesis are negatively correlated traits. Results suggest that losing the ability to synthesize cyanogens has restricted sara-sapho clade species to specific hosts containing SMC cyanogens and explains dietary restriction in this clade.

Animals↗