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SOCIAL STATUS AND AVAILABILITY OF FEMALES DETERMINE PATTERNS OF SPERM ALLOCATION IN THE FOWL
Author(s) -
Cornwallis Charlie K.,
Birkhead Tim R.
Publication year - 2006
Publication title -
evolution
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.84
H-Index - 199
eISSN - 1558-5646
pISSN - 0014-3820
DOI - 10.1111/j.0014-3820.2006.tb01227.x
Subject(s) - sperm , biology , sperm competition , reproductive success , human fertilization , fowl , sperm quality , reproductive value , fertility , zoology , ecology , andrology , demography , genetics , population , pregnancy , medicine , sociology , offspring
Where sperm competition occurs, the number and quality of sperm males inseminate relative to rival males influences fertilization success. The number of sperm males produce, however, is limited, and theoretically males should allocate sperm according to the probability of gaining future reproductive opportunities and the reproductive benefits associated with copulations. However, the reproductive opportunites and value of copulations males obtain can change over their lifetime, but whether individuals respond to such changes by adjusting the way they allocate sperm is unclear. Here we show that, in the fowl, Gallus gallus , dominant males, which have preferential access to females, modulate the number of sperm they ejaculate according to the availability of females. When presented with two femals, dominant males allocated more sprem to higher quality femalesw, whereas when females were on their own, only copulation order had an affect on their numbers of sperm to initial copulations, irrespective of femlae availability. We further swhow, by manipulating male social status, that sperm allocation is bhoth phenotypically plastic, with males adjusting their patternsof sperm allocate sperm, once the effects of social status are taken into accont. This study suggests that males have evolved sophisticated patterns of sperm allocation to respond to frequent fluctuations in trhe value and frequency of reproductive opportunites.