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Alternative reproductive tactics and strategies (ARTS) refer to polymorphic reproductive behaviours in which in addition to the usual two sexes, there are one or more alternative morphs, usually male, that have evolved the ability to circumvent direct intra-sexual competition. Each morph has its own morphological, ecological, developmental, behavioural, life-history, and physiological profile that shifts the balance between reproduction and self-maintenance, one aspect being immunity. Immunoecological work on species with ARTS, which is the topic of this review, is particularly interesting because the alternative morphs make it possible to separate the effects of sex per se from other factors that in other species are inextricably linked with sex. We first summarize the evolution, development, and maintenance of ARTS. We then review immunoecological hypotheses relevant to species with ARTS, dividing them into physiological, life-history, and ecological hypotheses. In context of these hypotheses, we critically review in detail all immunoecological studies we could find on species with ARTS. Several interesting patterns emerge. Oddly, there is a paucity of studies on insects, despite the many benefits that arise from working with insects: larger sample sizes, simple immune systems, and countless forms of alternative reproductive strategies and tactics. Of all the hypotheses considered, the immunocompetence handicap hypothesis has generated the greatest amount of work, but not necessarily the greatest level of understanding. Unfortunately, it is often used as a general guiding principle rather than a source of explicitly articulated predictions. Other hypotheses are usually considered a posteriori, but perhaps they should take centre stage. Whereas blanket concepts such as “immunocompetence” and “androgens” might be useful to develop a rationale, predictions need to be far more explicitly articulated. Integration so far has been a one-way street, with ecologists delving deeper into physiology, sometimes at the cost of ignoring their organisms’ evolutionary history and ecology. One possible useful framework is to divide ecological and evolutionary factors affecting immunity into those that stimulate the immune system, and those that depress it. Finally, the contributions of genomics to ecology are being increasingly recognized and sometimes applied to species with ARTS, but we must ensure that evolutionary and ecological hypotheses drive the effort, as there is no grandeur in the strict reductionist view of life.

Animals use multiple cues when choosing mates, but it is not yet clear why a single signal would not suffice. In this paper, drawing support from predation and “noise” effects on mate choice, marketing economics, and multiple signals models, a new hypothesis explaining multiple sexual signals is proposed: the sexual interference hypothesis. The hypothesis is based on three well-supported premises: (1) selectivity decreases when mate assessment costs increase, (2) assessment costs increase when the propagation or reception of sexual signals is more difficult, and (3) males not only exploit such circumstances by courting females when choice is more difficult, but actively interfere with females' preferences by making choice more difficult. The hypothesis argues that additional sexual signals evolve as a way for males to hinder female mate choice by interfering with the propagation and reception of other males' sexual signals. Females respond by evolving the ability to glean meaningful information from signals despite males' attempts at obfuscation. In turn, males respond by producing better interference signals and signals that are not so easily blocked. This co-evolutionary process increases the costs of assessment for females and the costs of signal production for males, and leads to a temporary equilibrium of honest advertising via multiple signals.

Anorexia nervosa is diagnosed by drastic weight loss, a fear of gaining weight, a distorted body image, and, in women, three consecutive episodes of amenorrhea. It is often associated with a compulsive need for exercise, a bright outlook on life, and a high level of competitiveness. It afflicts primarily young women in higher socioeconomic strata who are highly competitive and otherwise overachievers. There are three adaptive explanations for anorexia nervosa: the reproductive suppression, the fleeing famine and the pseudo-female hypotheses. Here I present a novel hypothesis, the age-related obesity hypothesis. It posits that the otherwise normal tendency by women to seek a youthful appearance can become maladaptive and lead to anorexia nervosa in environments in which thinness becomes the primary indicator of youth, such as in modern industrialized societies. This hypothesis explains the aforementioned associated features of anorexia nervosa, and its increasing prevalence in western societies. The hypothesis generates several testable predictions: (1) Prevalence of anorexia nervosa across societies should be related to the degree to which thinness is an indicator of youth in a population. (2) Conversely, perceptions of the weight-age relationship should differ among populations depending on the prevalence of anorexia nervosa. (3) Anorectic individuals, or those with the propensity to develop the disease, should have a biased perception of the weight-age relationship. (4) Experimental manipulation of individuals' perception of the weight-age relationship should affect weight concerns, particularly among anorectic or at-risk individuals. Should the hypothesis be supported it might be used to screen at-risk individuals. Furthermore, it would call for more integrative public health programs that take a comprehensive approach encompassing both obesity and anorexia.

Abstract The immune system is costly to operate, so we expect allocation to this function to relate to other indices of overall phenotypic condition. In captive male ruffs (Philomachus pugnax), we examine covariation between three seasonal male characteristics induced by testosterone (neck 'ruff', facial wattles, and increases in mass/size) and cell-mediated and humoral immunity. The ruff has two genetically distinct morphs of males, 'independents' and 'satellites', which differ in mating behaviour, somewhat in body size, and possibly life history strategy. Ruff length and wattle number were significantly correlated with each other and with body size, but unrelated to mass/size. Humoral immunity was weakly correlated with size, but not with secondary male traits, or with cell-mediated immunity. We did not detect differences in humoral immunity between morphs. Cell-mediated immunity was weakly correlated with ruff length, but not with wattle number, size, or mass/size. Cell-mediated immunity decreased significantly with age. Controlling for age, independents had higher cell-mediated immunity responses than satellites. The expected relationships between two measures of immune function and other measures of condition were not always present, which suggests we need more data and/or more specific predictions about how the different aspects of immune function relate to each other and to ecological variables.

The immune system is an energetically expensive self–maintenance complex that, given the risks of parasitism, cannot be carelessly compromised. Life–history theory posits that trade–offs between fitness components, such as self–maintenance and reproduction, vary between genders and age classes depending on their expected residual lifetime reproductive success, and seasonally as energetic requirements change. Using ruff ( Philomachus pugnax ), a bird with two genetically distinct male morphs, we demonstrate here a decrease in male immunocompetence during the breeding season, greater variance in immune response among males than females, immunosenescence in both sexes and male morphs, and a seasonal shift in the age range required to detect senescence. Using a phytohaemagglutinin delayed hypersensitivity assay, we assessed cell–mediated immunity (CMI) of males of typical breeding age during the breeding and nonbreeding seasons, and of a larger sample that included females and birds of a greater age range during the non-breeding period. CMI was higher for breeding–aged males in May than in November, but the increase was not related to age or male morph. In November, mean CMI did not differ between the sexes, but the variance was higher for males than for females, and there were no differences in mean or variance between the two male morphs. For both sexes and male morphs, CMI was lower for young birds than for birds of typical breeding ages, and it declined again for older birds. In males, senescence was detected in the non–breeding season only when very old birds were included. These results, generally consistent with expectations from life–history theory, indicate that the immune system can be involved in multifarious trade–offs within a yearly cycle and along an individual9s lifetime, and that specific predictions about means and variances in immune response should be considered in future immunoecological research.

The fact that avian eggs contain antibody of maternal origin is well documented, but only recently has this phenomenon been considered in an ecological context. We used tree swallows (Tachycineta bicolor) to examine the possibility of transgenerational immunity and its effect on nestling growth and immune development. We measured cell-mediated immunity with a delayed-hypersensitivity assay and antibody-mediated immunity with a hemagglutination test with sheep red blood cells (SRBCs). We tested for differences in immunocompetence and growth between nestlings from females who had been exposed to a novel antigen prior to egg laying and nestlings from unexposed females. To determine whether the effect, if any, resulted from something transferred to the eggs prior to egg laying or from subse - quent changes in parental behaviour, nestlings were exchanged so that at each nest half the nestlings were from fe - males who had been injected with SRBCs and half were from females who had not been exposed to SRBCs. Finally, brood sizes were independently manipulated to either 4 or 6 nestlings. We failed to detect maternal antibodies in any nestlings, and whether a female was exposed to SRBCs or not had no effect on the growth or cell-mediated immunity of her brood. However, nestlings in smaller broods grew better than nestlings in larger broods, though we did not find the expected differences in cell-mediated immunity. Furthermore, within each nest, nestlings whose mothers had been exposed to SRBCs grew better than nestlings whose mothers had not been exposed. These results are contrary to the idea of a simple trade-off in the allocation of resources between parasite protection and reproduction; however, they support the idea that exposure of females to parasites prior to egg laying leads to better nestling growth, and are con- gruous with the possibility of mithridatic parental care. Resume : La presence d'un anticorps d'origine maternelle dans les oeufs des oiseaux est un fait bien connu, mais ce n'est que recemment que ce phenomene a ete examine dans un contexte ecologique. Nous avons utilise des hirondelles bicolores (Tachycineta bicolor) pour verifier l'existence possible d'une immunite transmise d'une generation a l'autre et ses effets eventuels sur la croissance des oisillons au nid et sur le developpement de leur systeme immunitaire. Nous avons mesure l'immunite d'origine cellulaire au cours d'un test d'hypersensibilite retardee et l'immunite assuree par les anticorps au moyen d'un test d'hemagglutination SRBCs (globules rouges de mouton standardises). Nous avons cherche a etablir s'il y a des differences dans l'immunocompetence et la croissance chez les oisillons issus de femelles expo- sees a un antigene nouveau avant la ponte et chez les oisillons de femelles non exposees. Pour determiner si cet effet, s'il existe, resulte d'un transfert aux oeufs avant la ponte ou des changements subsequents dans le comportement pa- rental, les oisillons ont ete deplaces de telle sorte que, dans chaque nid, la moitie des oisillons etaient issus de femelles qui avaient recu une injection de SRBC et la moitie, issus de femelles non exposees aux SRBCs. Enfin, les couvees ont ete fixees independammen ta4o u 6o isillons. Nous n'avons detecte d'anticorps maternel chez aucun des oisillons et l'exposition d'une femelle a des SRBCs est sans effet sur la croissance ou l'immunite d'origine cellulaire de sa pro - geniture. Cependant, les oisillons des couvees moins nombreuses se developpent mieux que les oisillons des couvees plus grandes, mais nous n'avons pas observe les differences prevues quant a l'immunite d'origine cellulaire. De plus, dans chaque nid, les oisillons issus de meres exposees aux SRBCs ont eu une croissance meilleure que celle des oisil- lons issus de meres non exposees. Ces resultats contredisent l'hypothese d'un simple compromis dans l'allocation des ressources entre la protection contre les parasites et la reproduction, mais ils sont en accord avec l'hypothese selon la - quelle l'exposition aux parasites avant la ponte donne lieu a une meilleure croissance des oisillons et ne contredisent pas la possibilite de soins parentaux mithridatiques. (Traduit par la Redaction) 925

Endler (1980) suggested that in a carotenoid-poor envi-ronment, carotenoid-dependent sexual ornamentsindicateforaging ability, and hence, they can be used by femalesto gauge male quality. This idea led researchers to viewfemale mate choice from a fresh perspective, and it gaineda fair level of acceptance (Kodric-Brown 1989; Milinskiand Bakker 1990; Houde and Torio 1992; Frischknecht1993); however, many years passed before the “carotenoid-poor-environment” assumption began to be questioned(Hudon 1994; Linville and Breitwisch 1997; Grether et al.1999) or a viable alternative hypothesis was first conceived(Lozano 1994). Carotenoids stimulate the immune system,prevent cancer, and act as free radical scavengers (Ames1983; Bendich and Olson 1989; Di Mascio et al. 1991;Diplock 1991). These physiological functions had not beenconsidered in the ecological literature and led to the al-ternative hypothesis that carotenoid-dependentornamentsactually indicate the bearer’s immune condition and healthstatus (Lozano 1994). Lozano’s hypothesis was recentlyexpanded and generalized by Von Schantz et al. (1999),who proposed that sexual signals, carotenoid dependentor not, indicate resistance to oxidative stress. Hill (1999)recently outlined several alleged inconsistencies that “havebeen ignored or overlooked in the growing literature pro-moting the idea of carotenoids as signals of immuno-competence,” but his arguments and supporting evidencerequire careful scrutiny.First, Hill (1999) aptly titles a subsection “Comparing

Emlen and Oring (1977) suggested that monogamy in birds is maintained because of the need for strict biparental care. A corollary of their suggestion is that paternal care should decrease under conditions of high food abundance. An alternative is that paternal care would increase if males take advantage of the higher food abundance by trying to reduce the length of the nestling feeding period. We tested these two ideas using yellow warblers (Dendroica petechia) by providing some pairs with supplemental food, thereby reducing the importance of biparental care. However, the extra food did not decrease paternal effort, nor did it increase it (Fig. 2). Early in the nestling period experimental females brooded more but visited their nestlings less than did control females, but later, when brooding times decreased, experimental females fed their nestlings more than did control females (Fig. 3). There were no significant differences in nestling survival (Fig. 5), but nestlings in the control treatment were larger and heavier up to 6 days old (Fig. 6). The main effect of supplemental food was on maternal, not paternal behaviour. Models of biparental care assume interdependence between the parental effort of both parents. In this species, however, males and females provide for their brood independently from each other.

Vigil summarizes sex-related differences in emotivity, and presents a psychological model based on the restrictive assumption that responses to stimuli are dichotomous. The model uses for support the concept of intrasexual selection, but ignores intersexual selection. An alternative hypothesis might be that emotivity signals age: maturity in men and youth in women. Integration requires considering all evolutionary biology, not just agreeable concepts.

The role of parasitism has, to date, been largely ignored in optimal foraging theory. The mechanisms necessary to allow animals to use their diet to protect themselves from potential or actual parasitism have been observed in various species. The inclusion of the effects of parasitism on diet choice may considerably improve the predictive powers of future optimal foraging models