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Abstract Copulations are very brief in many species, sometimes taking only seconds, but in other species, they can be quite prolonged. Potential explanations for prolonged copulations include time requirements for the transfer of sperm and/or other ejaculate substances. Ejaculate substances could function to regulate female receptivity to subsequent matings, provide nutritional nuptial gifts, or hasten egg oviposition at a potential survival cost to the female. We investigated prolonged copulation in a member of the Enchenopa binotata complex of treehoppers (Hemiptera: Membracidae), in which females rarely remate and copulation can last several hours. We assigned females to treatments in which we interrupted copulation at different times. We also included a control where copulation was not interrupted. We found that females that experienced shorter copulations were more likely to be subsequently receptive to an attractive male. We also found that few females produced offspring when they engaged in short copulations compared to those with longer copulations. We did not find any differences in female survival. Our results support the sperm transfer and receptivity regulation hypotheses. We discuss potential reasons for why these processes should take so long in a species with low female remating.
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Hidden impacts of conservation management on fertility of the critically endangered kākāpō
Background Animal conservation often requires intensive management actions to improve reproductive output, yet any adverse effects of these may not be immediately apparent, particularly in threatened species with small populations and long lifespans. Hand-rearing is an example of a conservation management strategy which, while boosting populations, can cause long-term demographic and behavioural problems. It is used in the recovery of the critically endangered kākāpō ( Strigops habroptilus ), a flightless parrot endemic to New Zealand, to improve the slow population growth that is due to infrequent breeding, low fertility and low hatching success. Methods We applied Bayesian mixed models to examine whether hand-rearing and other factors were associated with clutch fertility in kākāpō. We used projection predictive variable selection to compare the relative contributions to fertility from the parents’ rearing environment, their age and previous copulation experience, the parental kinship, and the number of mates and copulations for each clutch. We also explored how the incidence of repeated copulations and multiple mates varied with kākāpō density. Results The rearing status of the clutch father and the number of mates and copulations of the clutch mother were the dominant factors in predicting fertility. Clutches were less likely to be fertile if the father was hand-reared compared to wild-reared, but there was no similar effect for mothers. Clutches produced by females copulating with different males were more likely to be fertile than those from repeated copulations with one male, which in turn had a higher probability of fertility than those from a single copulation. The likelihood of multiple copulations and mates increased with female:male adult sex ratio, perhaps as a result of mate guarding by females. Parental kinship, copulation experience and age all had negligible associations with clutch fertility. Conclusions These results provide a rare assessment of factors affecting fertility in a wild threatened bird species, with implications for conservation management. The increased fertility due to multiple mates and copulations, combined with the evidence for mate guarding and previous results of kākāpō sperm morphology, suggests that an evolutionary mechanism exists to optimise fertility through sperm competition in kākāpō. The high frequency of clutches produced from single copulations in the contemporary population may therefore represent an unnatural state, perhaps due to too few females. This suggests that opportunity for sperm competition should be maximised by increasing population densities, optimising sex ratios, and using artificial insemination. The lower fertility of hand-reared males may result from behavioural defects due to lack of exposure to conspecifics at critical development stages, as seen in other taxa. This potential negative impact of hand-rearing must be balanced against the short-term benefits it provides.
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- Award ID(s):
- 1826801
- PAR ID:
- 10408024
- Date Published:
- Journal Name:
- PeerJ
- Volume:
- 11
- ISSN:
- 2167-8359
- Page Range / eLocation ID:
- e14675
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.7717/peerj.14675
