Condition-dependence of male sexual signalling in the drumming wolf spider Hygrolycosa rubrofasciata
DisciplineEkologia ja ympäristönhoito
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 fitness increases in terms of mating success, but this is traded-off with viability which decreases as the ornament size increases. Males in poor condition have lower optimum level of the ornament expression than males in good condition. Ultimately, females that base their choice on the size of condition-dependent male sexual traits benefit in terms of increased offspring viability (i.e. `good genes´). In the wolf spider Hygrolycosa rubrofasciata, males have a costly and condition-dependent acoustic signal, courtship drumming, which is the target of female choice. Males with higher drumming rate have considerably higher viability than males with lower drumming rate, and females that mate with the more actively drumming males gain genetic benefits in terms of increased offspring viability. Also, male mobility is positively associated with male mating success. In this thesis, I tested if higher immunocompetence level can partly explain the better viability of males with high sexual performance. I also investigated if males with high sexual activity can compensate costs of increased risk of predation. Further, I examined if fluctuating symmetry can be used as a short-cut measure of male quality. Finally, I studied if sexual selection for viable males has any population-level consequences. My results show that males with higher drumming rate had higher encapsulation rate than males with lower drumming rate, and males with higher mobility had higher lytic activity than males with lower mobility. I also found that males with increased investment in drumming rate had lower lytic enzyme activity than control males. However, encapsulation rate was higher among males with increased investment in drumming rate. This might be due to males investing their immune effort to components of the body where it is likely to be most useful. My results suggest that conspicuous sexual signalling increases the risk of predation, but males with high sexual activity might be better in escaping from predation than males with low sexual activity. My results indicate that fluctuating asymmetry was negatively, but weakly related to male sexual performance at the population level. Finally, my results show that male survival and drumming rate were substantially reduced only in the smallest wolf spider populations. This suggests that the indirect benefits of female choice in terms of `good genes´ might cover the reduction in viability in small populations. The results of this thesis suggest that, in the drumming wolf spider H. rubrofasciata, sexual traits are related to several measures of individual quality through ´good genes´, and that sexual selection may have significant consequences at the population level. ...
- Artikkeli I: Ahtiainen, J. J., Alatalo, R. V., Kortet, R., & Rantala, M. (2004). Sexual advertisement and immune function in an arachnid species (Lycisidae). Behavioral Ecology, 15, 602-606. DOI: 10.1093/beheco/arh062
- Artikkeli II: Rantala, M. J., Ahtiainen, J. J., Alatalo, R. V. & Kortet, R. (2005). A trade-off between sexual signalling and immune function in a natural population of the drumming wolf spider Hygrolycosa rubrofasciata. Journal of Evolutionary Biology, 18(4), 985-991. DOI: 10.1111/j.1420-9101.2005.00907.x
- Artikkeli III: Lindström, L., Ahtiainen, J. J., Mappes, J., Kotiaho, J. S., Lyytinen, A., & Alatalo, R. V. (2006). Negatively condition dependent predation cost of a positively condition dependent sexual signalling. Journal of Evolutionary Biology, 19(2), 649-656. DOI: 10.1111/j.1420-9101.2005.01043.x
- Artikkeli IV: Ahtiainen, J. J., Mappes, J., Alatalo, R. V., & Vertainen, L. (2003). Fluctuating asymmetry and sexual performance in the drumming wolf spider Hygrolycosa rubrofasciata. Annales Zoologici Fennici, 40, 281–292. jyx.jyu.fi/handle/123456789/27039
- Artikkeli V: Ahtiainen, J. J., Alatalo, R. V., Mappes, J. & Vertainen, L. (2004). Decreased sexual signalling reveals reduced viability in small populations of the drumming wolf spider Hygrolycosa rubrofasciata. Proceedings of the Royal Society B, 271. DOI: 10.1098/rspb.2004.2791
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Tynkkynen, Katja (University of Jyväskylä, 2005)Lajienvälinen aggressiivisuus voi selittää immenkorentokoiraiden seksuaaliominaisuuden koossa havaittavaa vaihtelua, toteaa Katja Tynkkynen väitöskirjatyössään. Sekundaarisien seksuaaliominaisuuksien, kuten koiraslintujen ...
Baudry, Gautier; Hopkins, Juhani; Watts, Phillip C.; Kaitala, Arja (Springer, 2021)Theory predicts that because costs constrain female sexual signaling, females are expected to have a low signaling effort that is increased with passing time until mating is secured. This pattern of signaling is expected ...
Fluctuating asymmetry and sexual performance in the drumming wolf spider Hygrolycosa rubrofasciata Ahtiainen, Jari J.; Alatalo, Rauno Veli; Mappes, Johanna; Vertainen, Laura (Finnish Zoological and Botanical Publishing Board, 2003)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, ...
Parri, Silja (1999)Female choice for male acoustic signalling and consequences of female selective mating behaviour were studied in the wolf spider Hygrolycosa rubrofasciata. Males of this species produce audible drumming signals that they ...