Parasite–induced risk of mortality elevates reproductive effort in male Drosophila

Abstract

A trade-off between sex and somatic maintenance is fundamental to life-history theory. Tests of this trade-off usually emphasize deleterious consequences of increased reproduction on life span. Here we show the reverse effect, that reductions in the expected life span elevate sexual activity. Experimentally parasitized male Drosophila nigrospiracula lived shorter lives, but before dying, they courted females significantly more than unparasitized controls. This greater courtship resulted in increased mating speed, and potentially greater reproductive success than parasitized males would have achieved otherwise. The results show that an environmental reduction in life span increases reproductive effort, and support the hypothesis of a trade-off between these key life-history traits.

Condition-dependent reproductive effort in frogs infected by a widespread pathogen

“…A functionally similar response to infection by B. dendrobatidis occurs in northern leopard frogs (Lithobates pipiens); the testes of infected males are larger and contain more sperm than those of uninfected males [15]. Studies on other taxa reveal that present reproductive effort can increase as life expectancy decreases [10][11][12][13][14][15][16][17][18]. In our study, however, calling activity did not increase in all infected frogs; we found that infected frogs in relatively poor condition were less likely to call than uninfected frogs.…”

“…For example, among female hosts, Tasmanian devils (Sarcophilus harrisii) infected by a transmissible cancer mature and breed earlier [12], and crickets (Acheta domesticus) infected by a bacterium, and water fleas (Daphnia magna) infected by a microsporidian lay more eggs [13,14]. Among male hosts, frogs (Lithobates pipiens) infected by a fungus increase sperm production [15], flies (Drosophila nigrospiracula) infected by a parasitic mite, and amphipods (Corophium volutator) infected by trematodes increase reproductive effort [16,17], and beetles (Tenebrio molitor) infected by tapeworms provide higher quality nuptial gifts to their mates, thus increasing egg production [18]. Whether hosts increase their reproductive effort in response to an infection depends on many factors, including resource availability [19].…”

Variable male potential rate of reproduction: high male mating capacity as an adaptation to parasite–induced excess of females?

“…However, parasite-induced risk of mortality may also increase reproductive effort (e.g. Polak & Starmer 1998). Numerous animals harbour endoparasites or endosymbionts which gain transmission to a new host generation via female eggs.…”

“…Polak & Starmer 1998;Altizer & Oberhauser 1999;Bollache et al 2002), with different mechanisms and proximate or ultimate causes (Worden et al 2000;Combes 2001;Hurd 2001). In some cases, parasites decrease the reproductive effort of their hosts as host resources are reallocated to parasites (Combes 2001).…”

Terminal Investment Induced by Immune Challenge and Fitness Traits Associated With Major Histocompatibility Complex in the House Sparrow

“…Mortality rate is not only affected by intrinsic factors such as age but also by extrinsic factors such as predation, food shortage, and parasitism. Infection may be a good indicator of a rapidly diminishing life span (Grenfell and Dobson 1995), and both theoretical and empirical work has shown that parasitized hosts can adaptively adjust their life-history traits to reduce the cost of parasitism (Minchella and LoVerde 1981;Hochberg et al 1992;Forbes 1993;Lafferty 1993;Polak and Starmer 1998;Adamo 1999;Agnew et al 2000;McCurdy 2000). For instance, Biomphalaria glabrata snails underwent a reproductive burst immediately following exposure to Schistosoma mansoni (Minchella and LoVerde 1981).…”