Butterflies in the family Lycaenidae that have obligate associations with ants frequently exhibit ant-dependent egg laying behaviour. In a series of field and laboratory choice tests, we assessed oviposition preference of the Australian lycaenid Jalmenus evagoras in response to different species and populations of ants. Females discriminated between attendant and nonattendant ant species, between attendant ant species, and to some extent, between populations of a single ant species. When preferences were found, ovipositing butterflies preferred their locally predominant attendant ant species and geographically proximate attendant ant populations. A reciprocal choice test using adults from a generation of butterflies reared in the absence of ants indicated a genetic component to oviposition preference. Individual females were flexible with respect to oviposition site choice, often ovipositing on more than one treatment during a trial. Preferences arose from a hierarchical ranking of ant treatments. These results are discussed in terms of local adaptation and its possible significance in the diversification of ant-associated lycaenids.
Juveniles of the Australian common imperial blue butterfly, Jalmenus evagoras, produce substrate-borne vibrational signals in the form of two kinds of pupal calls and three larval calls. Pupae stridulate in the presence of conspecific larvae, when attended by an ant guard, and as a reaction against perturbation. Using pupal pairs in which one member was experimentally muted, pupal calls were shown to be important in ant attraction and the maintenance of an ant guard. A pupa may use-calls to regulate levels of its attendant ants and to signal its potential value in these mutualistic interactions. Therefore substrate-borne vibrations play a significant role in the communication between J. evagoras and its attendant ants and pupal calls appear to be more than just signals acting as a predator deterrent. Similarly, caterpillars make more sound when attended by Iridomyrmex anceps, suggesting that larval calls may be important in mediating ant symbioses. One larval call has the same mean dominant frequency, pulse rate, bandwidth and pulse length as the primary signal of a pupa, suggesting a similarity in function. (C) 2000 The Association for the Study of Animal Behaviour.
The mating system of the Australian lycaenid butterfly, Jalmenus evagoras, is highly unusual compared to most other Lepidoptera. Characteristics of this system, which has been termed an 'explosive mating strategy,' include the formation of an intensely competitive mating aggregation of males, a highly male biased operational sex ratio, a lack of discrimination and mate choice by both sexes, a high variance in male mating success, and female monogamy. In this study, we tested the hypothesis that multiple mating by males imposes physiological costs resulting in smaller spermatophores, and that this results in a fitness cost to females. We found that male J. evagoras transferred only 2.2% of their eclosion weight during their first mating, consistent with the hypothesis that males of monandrous species produce a relatively small investment. The wet weight of the ejaculate declined by an average of 27% at the second mating and the dry weight by 29%, and an intermating interval of 5-9 days was needed for the ejaculate to return to the size at the first mating, regardless of male size or age. Wet ejaculate mass increased proportionally with male size, though dry mass was proportionally larger in smaller males. Ejaculate mass tended to increase with male age at both first and second matings. Female characteristics, in general, did not affect ejaculate mass, although the wet weight of the ejaculate was positively associated with female weight at the second mating. Copulation duration increased from 2.4 h to approximately 3 h at the second mating, and to over 4 h at the third and fourth matings. Fecundity was positively correlated with female size but not with mating history, copulation duration, or any other characteristics measured for either males or females. Female longevity declined significantly as the number of times the male partner had previously mated increased. We conclude that despite the small male investment in ejaculate, the costs of multiple mating may nonetheless be significant, as indicated by the reduction in ejaculate mass, an increase in copulation duration, and reduction in female lifespan with increasing mating number.
If a mutualistic relationship entails providing services at a cost, selection will favor individuals that maximize the net benefits of the interaction and minimize the costs. Larvae of many species of lycaenid butterflies secrete nutritious food rewards to attending ants and, in return, receive protection against predators and parasitoids. Because ants typically recruit more workers to larger resources, by forming groups the larvae may ensure more reliable access to ants and thereby gain better protection. A further consequence of aggregating should be a change of the cost-benefit relationship for individual larvae. The larger the group, the smaller a single larva's influence will be on total ant density, which could lead to a smaller investment in secretion, thus reducing the per capita cost of cooperation. In this study, the influence of ant attendance, group size, and companion quality on larval investment was investigated. The interaction between the obligately ant-dependent lycaenid, Jalmenus evagoras, and its attendant Iridomyrmex ants was manipulated and the effect on larval secretion measured. As the level of ant attendance increased, the delivery of food rewards increased, both for solitary and for aggregated larvae. When aggregated, larvae provided less food rewards to ants than when solitary, and secretion rate decreased with increasing group size. Furthermore, larvae had lower secretion rates when paired with a bigger, more attractive larva than when paired with a smaller one. The considerable reduction in secretion rates for larvae in groups suggests that gaining protection at a lower secretion cost could be one factor that promotes aggregation in myrmecophilous lycaenids.
Populations of the myrmecophilous lycaenid Falmenus evagoras Donovan were assessed for genetic structure at three hierarchical spatial scales: sites, geographically-defined subpopulations, and subpopulations defined by species of mutualistic ant-associate. Estimates of Wright's F-ST generated from multilocus electrophoretic data revealed low, though significant, amounts of genetic structure. Most structure was observed at the level of geographic subpopulations, suggesting that adult butterflies do not exhibit preferential mating and oviposition along the lines of ant associate. The genetic structure data, together with estimates of Nei's genetic distance (D) for pairwise site and subpopulation comparisons, suggest that F. evagoras populations are spatially and temporally dynamic. These patterns are considered in the context of extinction and recolonization models. The extreme patchiness of F. evagoras populations stems from the stringent requirements of both host plant and host ant, contributing to an extinction/ recolonization process. We discuss the key parameters influencing genetic cohesion versus differentiation under an extinction/recolonization regime, including mode of butterfly dispersal, site turnover rate, and the effects of host dispersal and phenology. This system provides a model of population-level consequences of certain mutualistic interactions as well as of a class of patterns arising from an extinction/recolonization process. (C) 1996 The Linnean Society of London
Moths and butterflies whose larvae do not feed on plants represent a decided minority slice of lepidopteran diversity, yet offer insights into the ecology and evolution of feeding habits. This paper summarizes the life histories of the known predatory and parasitic lepidopteran taxa, focusing in detail on current researchin the butterfly family Lycaenidae, a group disprotionately rich in aphytophagous feeders and myrmecophilous habits.
Larvae and pupae of the Australian lycaenid butterfly, Jalmenus evagoras Donovan (Lepidoptera; Lycaenidae), are protected from parasites and predators by attendant ants. In return, the juveniles of J.evagoras secrete to the ants a solution containing substantial amounts of sugars and amino acids. Larvae of J.evagoras were reared from hatching until adult eclosion either with or without ants. Experiments were performed to examine whether fifth (final) instar larvae attempt to compensate for the nutrient loss to ants, by consuming more food, digesting food more efficiently, or extending development time. The presence or absence of ants had no effect on the feeding rate, efficiency of digestion or development time of fifth instar larvae. Larvae with ants converted a smaller proportion of ingested food into biomass, and consequently grew less than their counterparts without ants. Thus fifth instar larvae of J.evagoras do not appear to compensate for the nutrient loss to ants. Possible reasons for the failure to compensate are discussed.
1. Juveniles of the Australian lycaenid butterfly, Jalmenus evagoras (Donovan), secrete to ants a solution of sugars and amino acids, primarily serine. The attendant ants protect the larvae and pupae from parasites and predators.2. The effect of caterpillar nutrition on the defence provided by ants was investigated. Potted food plants of Acacia decurrens were either given water containing nitrogenous fertilizer or were given water alone. Fertilized plants had a higher nitrogen content than unfertilized plants.3. Fifth instar larvae of J.evagoras feeding on fertilized plants attracted a larger ant guard than those feeding on unfertilized plants. In the absence of caterpillars, ants were not differentially attracted to fertilized and unfertilized plants.4. In the presence of ants, over a 10-day period, larvae on fertilized plants survived better than larvae on unfertilized plants. In the absence of ants larvae survived equally on fertilized and unfertilized plants. It is concluded that larvae on fertilized plants attracted a larger ant guard, and thereby survived better, than larvae on unfertilized plants.5. Adult females of J.evagoras preferred to lay egg batches on fertiizedd rather than unfertilized plants, but they did not lay larger egg batches.
Many organisms make a living from seratching each other's backs. and many survive at the expense of othcrs. Once a complex interaction has arisen between two organisms. what elfect can such a relationship have on their subsequcnt cvolution·! This pllpcr will consider thc evolutionary conscquences of ussocintions UIllOlIg Iycllcnid buttcrflics, their host plants, unts. purusitoids. lind prcdators. Thc Lycacllidac llfC cspecially intcrc.'1ting from an ccologicul and evolutionary pcrspcctivc because they exhibit dramatic variety in their life histories. The larvae of many species associate with ants, and these relationships can be parasitic. commensal, or mutualistic. larvae cun be carnivorous or hcrbivorous: and some species interact with many species of ants, whereas others are species-specific. It is partly because of this complexity and diversity that the lycaenidae have not been studied as intensively as other buUerny families, and I will discuss at least three problems that have hampered our understanding of their ecology and evolution. In particular. more must be learned about the nature of the exocrine secretions of lycaenid larvae, and whether they function to reward. appease, and/or deceive their associated ants. The association between lycaenids and ants has had several important evolutionary consequences, and I will show how these relate to the question of why there are so many species of Iycaenid buuernies. Finally. I will discuss an unresolved pattern in the biogeography oflycaenid buuernies: association with ants in general, and species-specific interactions in particular, are far more common among Iycaenids found in Ethiopian, Oriental. and Australasian regions than among those from the Holarctic.