0000000000803831
AUTHOR
Jari J. Ahtiainen
A trade-off between sexual signalling and immune function in a natural population of the drumming wolf spider Hygrolycosa rubrofasciata.
The field of ecological immunology is ultimately seeking to address the question ‘Why is there variation in immune function?’ Here, we provide experimental evidence that costs of ubiquitous sexual signals are a significant source of variation in immune function. In the mating season, males of the wolf spider Hygrolycosa rubrofasciata drum against dry leaves while wandering around the habitat searching for receptive females. According to a previous study, the male metabolic rate during the drumming increases 22-fold compared to the resting metabolic rate. In the present study, we examined whether investment in costly courtship drumming decreases male immune function in a wild population of H…
Condition-dependence of male sexual signalling in the drumming wolf spider Hygrolycosa rubrofasciata
Jari Ahtiaisen väitöskirjatyön tutkimusten perusteella voidaan todeta, että H. rubrofasciata susihämähäkkinaaraat voivat käyttää koiraan seksuaalista kuntoa mittana arvioidessaan koiraan fenotyyppistä ja geneettistä laatua. Näyttäisi myös siltä, että seksuaalivalinnalla on merkittäviä populaatiotason vaikutuksia. Eläinten seksuaaliominaisuudet voivatkin tulevaisuudessa tarjota uusia keinoja populaatioiden sukupuuttouhan ja elinkyvyn arvioimiseen. The ´good genes´ or ´handicap´ model of sexual selection focuses on the evolution of female preferences for male sexual traits by using condition-dependence as the mediating mechanism. As the ´size´ of the preferred sexual trait increases, male fit…
Sexual advertisement and immune function in an arachnid species (Lycosidae)
A simple version of the immunocompetence handicap hypothesizes that through condition-dependence, the size of the sexual trait may be positively related to immune function at the population level. In the present study, we investigated the relationship between sexual advertisement and immune function in a natural population of male wolf spiders, Hygrolycosa rubrofasciata (Araneae: Lycosidae). Males of H. rubrofasciata have a costly and condition-dependent acoustic signal, courtship drumming. In the mating season, males drum against dry leaves while wandering around the habitat searching for receptive females. Males increase their mating success by increasing their drumming rate and mobility.…
Fluctuating asymmetry and immune function in a field cricket
Recently, fluctuating asymmetry (FA) of morphological traits has attracted great attention as a short-cut measure of individual quality. Whereas there is some evidence that FA of sexual ornaments is negatively associated with immune function, studies concerning FA and immune function in non-ornamental traits are absent. Here, we tested whether FA of three non-ornamental traits in hind limbs is related to male immune function in a population of the Mediterranean field cricket, Gryllus bimaculatus. As different measures of male immune function, we used encapsulation rate and lytic activity. We found that a composite measure of FA (cFA) was negatively related to encapsulation rate. However, ly…
Decreased sexual signalling reveals reduced viability in small populations of the drumming wolf spider Hygrolycosa rubrofasciata.
One of the important goals in conservation biology is to determine reliable indicators of population viability. Sexual traits have been suggested to indicate population extinction risk, because they may be related to viability through condition dependence. Moreover, condition-dependent sexual traits may be more sensitive indicators of population viability than early life-history traits, because deleterious fitness effects of inbreeding tend to be expressed mainly at the end of the species' life history. However, empirical evidence of the significance of sexual behaviour for population viability is missing. In this study, we examined two male sexual traits and survival in 39 different-sized …
Negatively condition dependent predation cost of a positively condition dependent sexual signalling.
Predation is considered as an important factor constraining the expression of sexual signals. Nevertheless, direct quantitative evidence for predation provoking significant viability costs on individuals signalling at high rates is scarce. Moreover, it is unclear whether high rate signallers are able to balance presumably increased predation costs. We examined whether a condition dependent audible sexual signal, drumming, makes Hygrolycosa rubrofasciata male spiders more prone to predation by pied flycatchers (Ficedula hypoleuca), and whether sexual signalling rate is related to escaping ability once attacked. When birds were given a choice between two spider males manipulated to drum eithe…
Fluctuating asymmetry and sexual performance in the drumming wolf spider Hygrolycosa rubrofasciata
Recently, there has been much interest in estimating fluctuating asymmetry (FA) of morphological traits as a short-cut measure of individual quality. FA deals with small differences around the symmetry value of zero. Thus, measurement error is often relatively large. However, repeated measurements. and large sample sizes allow reliable estimates of FA that can be corrected for errors. The purpose of this study was two-fold: at the biological level, we examined with a large sample size (N = 804) whether pedipalp FA could be used as a short-cut measure, of individual quality in the wolf spider Hygrolycosa rubrofasciata. This was done by estimating how strongly FA correlates with male sexual p…