Stable isotopic niche predicts fitness of prey in a wolf–deer system

Interindividual variation in niche presents a potentially central object on which natural selection can act. This may have important evolutionary implications because habitat use governs a suite of selective forces encountered by foragers. In a free-living native black-tailed deer, Odocoileus hemionus , population from coastal British Columbia, we used stable isotope analysis to identify individual variation in foraging niche and investigated its relationship to fitness. Using an intragenerational comparison of surviving and nonsurviving O. hemionus over 2 years of predation by wolves, Canis lupus, we detected resource-specific fitness. Individuals with isotopic signatures that suggested they foraged primarily in cedar ( Thuja plicata )-dominated and low-elevation hemlock ( Tsuga heterophylla )-dominated forest stands were more likely to be killed by C. lupus . High-quality forage in T. plicata stands, as indexed by protein content, may be involved in maintaining this foraging phenotype. Moreover, nonsurvivors diverged more than survivors from median isotopic signatures, suggesting selection against foraging specialization. Stable isotope analysis provides a novel opportunity to integrate ecological and selective landscapes in order to identify underlying ecological mechanisms of selection and provide insight into the maintenance of variability.  © 2007 The Linnean Society of London, Biological Journal of the Linnean Society , 2007, 90 , 125–137.     

Restoration of morphological and functional integrity in the regenerating eye of the giant African land snail Achatina fulica

To determine whether vision returns to its original state following eye removal in Achatina fulica, light and electron microscope examinations, electrophysiological recordings and behavioural tests were carried out on the regenerating snails. Reparative morphogenesis can result in the restoration of the peripheral sense organ even in the absence of complete regrowth of the tentacle, but it can also lead to the formation of aberrant regenerates. We found that anatomically and ultrastructurally the eyes of the ‘most normal’ regenerates were basically the same as the original eyes. Under normal conditions each eye is composed of a principal and an accessory eye, both sharing a common cornea. The only difference between regenerated and native eyes is the smaller size of the former, as a result of a reduced number of retinal cells. Electroretinographic responses revealed that the molecular mechanism of phototransduction is restored, in principle, but that flicker fusion frequency in the regenerated eye is significantly lower than in the normal eye. The directional movement to a visual stimulus (a black stripe of 45° width) had not completely recovered even 6 months after amputation. This suggests that the central projections of the optic nerve had not become fully re‐established at the time of testing.     

Fritillary phylogeny, classification, and larval host plants: reconstructed mainly on the basis of male and female genitalic morphology (Lepidoptera: Nymphalidae: Argynnini)

Species-level phylogeny of the Butterfly tribe Argynnini is established based on 141 characters derived from wing and genitalia morphology of both sexes. The Argynnini can be divided into three subtribes; Yrameina comprising Yramea and Boloria s . l ., Argynnina comprising Prokuekenthaliella , Issoria , Brenthis , and all the 'large fritillary' species joined in the genus Argynnis s . l . and a new subtribe Euptoietina comprising only the genus Euptoieta . The classical genus Issoria s . l . is polyphyletic regarding Yramea and possibly paraphyletic regarding the two Afrotropic species baumanni and hanningtoni ; these two species are tentatively transferred to the old genus/subgenus Prokuekenthaliella . Surprisingly, one Afrotropic species, Issoria smaragdifera is closely related to the East Palaearctic Issoria species. A revised classification of Argynnini is proposed based on the obtained phylogeny. Studies of larval host plants based on the obtained phylogeny suggest that the ancestral Argynnini used Passiflora and Violaceae, but already the ancestor of Yrameina + Argynnina was probably specialized on Violaceae. Whereas the Boloria species have turned to other food plants such as Dryas , Vaccinium and Salix on several occasions, only Brenthis among the Argynnina use other host plants than Viola (mainly Rosaceae). The habit of laying eggs away from the food plant has probably evolved twice within Argynnina.  © 2006 The Linnean Society of London, Biological Journal of the Linnean Society , 2006, 89 , 627–673.     

Amphibious behaviour and feeding ecology of the four-eyed blenny (Dialommus fuscus, Labrisomidae) in the intertidal zone of the island of Santa Cruz (Galapagos, Ecuador)

The labrisomid Dialommus fuscus , endemic to the Galapagos archipelago, is a predator of crustaceans, which moves up and down the intertidal zone with the tides. Its divided eye and elongated body permit it to forage in the wet sections of the intertidal habitat during low tide, both on the rocks and below the water line and in tide pools. Compared with other intertidal fishes (e.g. Bathygobius sp.), it was present on the rock flat in significantly smaller tide pools nearer to the water line during low tide.     

Behavioural response of Mullus surmuletus to habitat modification by the invasive macroalga Caulerpa taxifolia

Densities of red mullet Mullus surmuletus have declined since 1996 at Cap Martin, Alpes‐Maritimes, France, following colonization by Caulerpa taxifolia . Foraging M. surmuletus were rarely observed over C. taxifolia or the seagrass Posidonia oceanica , but were observed over bare sand and endemic macroalgae. Within colonized sites (where the mean cover of C. taxifolia was 30–100%), fish were concentrated on areas with low cover of C. taxifolia (<21%). A difference in the frequency of observations of foraging groups (17%) was observed between sites with and without C. taxifolia . The observed patterns were probably due to a physical barrier to foraging that is presented by meadows of C. taxifolia . Changes to habitat structure that occur when the substratum is colonized by C. taxifolia influence the accessibility to benthic food resources, and consequently the foraging activities of fish that feed on benthic invertebrates. The decline in density of M. surmuletus at Cap Martin could be the result of fish emigration from colonized sites (unfavourable to the species) to uncolonized sites.     

Pre‐copulation intervals,copulation frequencies,and initial progeny sex ratios in two biotypes of whitefly,Bemisia tabaci

The whitefly Bemisia tabaci (Gennadius) (Homoptera: Aleyrodidae) is a species complex, and its systematic classification requires controlled crossing experiments among its genetic groups. Accurate information on pre‐copulation intervals, copulation frequencies, and initial frequency of egg fertilization of newly emerged adults is critical for designing procedures for collecting the virgin adults necessary for these experiments. In the literature, considerable variation is reported between B. tabaci populations, with respect to the length of the pre‐copulation interval and the initial frequency of egg fertilization. Here, we used a video‐recording method to observe continuously the copulation behaviour of the Mediterranean/Asia Minor/Africa (B biotype) and the Asia II (ZHJ1 biotype) groups of B. tabaci. We also recorded the initial frequency of egg fertilization, as determined by the sex of the progeny. When adults were caged in female–male pairs on leaves of cotton plants, the earliest copulation events occurred 2–6 h after emergence; at 12 h after emergence 56–84% of the females had copulated at least once, and nearly all (92–100%) had copulated at least once by 36 h after emergence. Both females and males copulated repeatedly. Approximately 80 and 20% of copulation events occurred during the photophase and scotophase, respectively. By 72 h post‐emergence, the females of the B and ZHJ1 biotypes had copulated on average 6.1 and 3.9 times, respectively. When adults were caged in groups on plants 1–13 h after emergence, 30–35% of the eggs deposited during this period were fertilized, and approximately 90% of females were fertilized by the end of the 13 h. Although timing of copulation differed in detail between the two genetic groups, the results demonstrate that B. tabaci adults can start to copulate as early as 2–6 h post‐emergence and the majority of females can become fertilized on the day that they emerge.     

Parasitoid behaviour: predicting field from laboratory

Abstract.  1. Most of what is known about parasitoid behaviour comes from laboratory observations: field quantitative observations on searching parasitoids are extremely difficult to do and are rare. The basic components of Aphytis melinus 's response to California red scale ( Aonidiella aurantii ) were studied in the laboratory: encounter, rejection, drumming, probing, oviposition, and host-feeding. It was then asked whether these observations provided a reliable guide to behaviour in the field in a situation that was very different from the laboratory.
2. Field observations were carried out on bark on the trunk and interior branches of trees where live scale density is extremely high in patches, dead scale make up 90% of all scale, and could be expected to interfere with Aphytis search.
3. The laboratory observations predicted well the time taken in the field for each basic event (drumming or probing) and average times spent on a scale. Also well predicted were the distributions of times spent on drumming, probing, and total time on a scale. Rejection rates were much higher in the field. Thus, the laboratory studies predicted foraging behaviour in the field with variable success; potential explanations for observed mismatch between laboratory and field and its possible larger implications are discussed.