Showing papers by "Geoff A. Parker published in 1999"
TL;DR: A quantitative attempt to incorporate female processes into the analysis of sperm utilization patterns in insects by following the movement of the copulating male's ejaculate through the female's reproductive tract using males labeled with different radioisotopes.
Abstract: Despite the ubiquity with which patterns of sperm utilization have been studied, the mechanisms underlying fertilization in insects are far from clear. One well‐studied system is the yellow dung fly, in which the last male's ejaculate is thought to displace rival sperm from the female's sperm stores. Here we follow the movement of the copulating male's ejaculate through the female's reproductive tract using males labeled with different radioisotopes. We find that males ejaculate into the bursa copulatrix and that male‐1 sperm are displaced from the spermathecae during copulation. The increase in male‐2 ejaculate in the spermathecae matches the pattern of male‐2 fertilization gain, indicating that only spermathecal sperm are utilized at fertilization. Previously we have analyzed this system with a direct model of sperm displacement in which the male displaces rival sperm from the spermathecae. The data, and morphology of the female, clearly preclude such a mechanism. Here we contrast this model w...
102 citations
TL;DR: In this paper, the authors show that Trivers' formulation applies in a limited range of circumstances and offer an alternative formulation that is universally applicable, under which the optimal investment from the offspring's point of view in species with uniparental care and hence, the extent of parent-offspring conflict depends on the cost of the caring parent's investment to the future fitness of the non-caring parent.
Abstract: R. L. Trivers used Hamilton's rule regarding the evolution of altruistic behaviour to demonstrate the occurrence of parent–offspring conflict and concluded that this would be more severe when future offspring were half siblings rather than full siblings of the offspring currently receiving investment. Here we show that Trivers' formulation applies in a limited range of circumstances and offer an alternative formulation that is universally applicable. Under this formulation the optimal investment from the offspring's point of view in species with uniparental care and, hence, the extent of parent–offspring conflict depends on the cost of the caring parent's investment to the future fitness of the non-caring parent.
47 citations
2 citations
TL;DR: It would be extremely useful, and probably reasonably straightforward, to use data presented in a manner that can be used to calculate the strength of interference – both to incorporate within theoretical models and provide comparisons with other taxa.
Abstract: We admire the fine primatological research1xSee all References1 to which Harcourt rightly draws our attention, and which shows the relationships between rank, group size and feeding behaviour. There does, however, seem to be a difference in terminology between this work and our own. We considered interference in terms of a quantified relationship between population density and mean or individual intake rate2xHassell, M.P. and Varley, G.C. Nature. 1969; 223: 1133–1136CrossRef | PubMed | Scopus (378)See all References2 as used in innumerable entomological and some ornithological studies. Many primate studies, for sensible reasons, consider interference as a change in foraging efficiency, activity budgets, or feeding-bout durations with group size; however, these measures may have a complex relationship with intake rate. Some studies do relate intake to rank (e.g. 2xHassell, M.P. and Varley, G.C. Nature. 1969; 223: 1133–1136CrossRef | PubMed | Scopus (378)See all References, 3xvan Schaik, C.P. and van Noordwijk, M.A. Behaviour. 1988; 105: 77–98CrossRefSee all References, 4xJanson, C.H. Behav. Ecol. Sociobiol. 1985; 18: 125–138CrossRef | Scopus (174)See all References, 5xBarton, R.A. and Whiten, A. Anim. Behav. 1993; 46: 777–789CrossRef | Scopus (92)See all References) and group size (e.g. Ref. 5xBarton, R.A. and Whiten, A. Anim. Behav. 1993; 46: 777–789CrossRef | Scopus (92)See all ReferencesRef. 5).Although in such examples the data are not presented in a manner that can be used to calculate the strength of interference, we suggest it would be extremely useful, and probably reasonably straightforward, to use such data to do so – both to incorporate within theoretical models and provide comparisons with other taxa.
2 citations