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51.
In mammals with solitary females, the potential for males to monopolize matings is relatively low, and scramble competition polygyny is presumed to be the predominant mating system. However, combinations of male traits and mating tactics within this type of polygyny have been described. The main aim of our study was to identify the relative importance of, and interactions among, potential determinants of contrasting male reproductive tactics, and to determine their consequences for male reproductive success in a small solitary nocturnal Malagasy primate, the gray mouse lemur (Microcebus murinus). We studied their mating behavior over three consecutive annual mating seasons. In addition, we determined the genetic relationships among more than 300 study animals to quantify the reproductive success of individual males. We found that, with a given relatively low overall monopolization potential, successful male mouse lemurs roamed extensively in search of mates, had superior finding ability and mated as early as possible. However, contest competition was important too, as temporary monopolization was also possible. Males exhibited different mating tactics, and heavier males had a higher reproductive success, although most litters had mixed paternities. Switching between tactics depended on short-term local variation in monopolization potential determined by a pronounced dynamic in fertilization probability, number of alternative mating opportunities, and the operational sex ratio. This study also revealed that the dynamics of these determinants, as well as the mutual interactions between them, necessitate a detailed knowledge of the mating behavior of a species to infer the impact of determinants of alternative mating tactics.Electronic Supplementary Material Supplementary material is available in the online version of this article at
Communicated by S. AlbertsThis revised version was published online in August 2004 with corrections to Figure 2. 相似文献
52.
Harry?L.?S.?RobertsEmail author Oliver?True Otto?Schmidt 《Behavioral ecology and sociobiology》2004,57(2):132-138
In a laboratory colony of the asexual solitary endoparasitoid Venturia canescens Grav. (Hymenoptera: Ichneumonidae), two genetically and phenotypically distinct lines (RP and RM) appear to coexist sympatrically, with the reproductive success of the RM-line being greater under con-specific superparasitism but lower under self superparasitism. To investigate the basis of the RM-lines advantage under con-specific superparasitism, we examined the outcome of inter-larval physical combat under in-vitro conditions. The results showed that the outcome depended on both the relative and absolute ages of the contestants, and that the competitive abilities of the two lines were not symmetric. In contests involving a larva and an egg, the unhatched wasp lost. In contests involving two larvae, at least one of which was newly hatched, the RP-larva tended to lose. Finally, if both larvae were at least 8–10 h post-hatching when the contest occurred, then the larger larva tended to lose, with the probability increasing with the difference in length between the two larvae. Thus, the higher reproductive success of the RM-line under competing superparasitism with the RP-line is due to a physiological difference between the newly hatched larvae of the two lines, which results in an advantage to the RM-larva independent of the order or time interval between ovipositions.Communicated by P. Heeb 相似文献
53.
Joris M. Koene Tina Pförtner Nico K. Michiels 《Behavioral ecology and sociobiology》2005,59(2):243-249
Sexual conflict between mating partners can give rise to strategies that are advantageous for one sex but harmful to the opposite sex. Usually, sperm donors develop (offensive) traits to enhance their chances in sperm competition, while sperm recipients evolve (defensive) traits that allow them to stay in control of who fathers their offspring. Here, we demonstrate that these processes are also at work in simultaneous hermaphrodites. The hermaphroditic earthworm Lumbricus terrestris uses 40 to 44 copulatory setae to pierce into its partner's skin, causing damage and injecting a substance from its setal glands. Experimental injection of the gland substance indicates that a refractory period may be induced. More importantly, removal of the copulatory setae shows that they influence the partner's sperm uptake. When the setae are present, more sperm are taken up and sperm are distributed more equally over the four spermathecae. We interpret this as a strategy that stacks the odds for the donor's sperm in fertilizing cocoons. 相似文献
54.
Sexual cohabitation as mate-guarding in the leaf-curling spider Phonognatha graeffei Keyserling (Araneoidea, Araneae) 总被引:1,自引:1,他引:1
The leaf-curling spider Phonognatha graeffei incorporates a twisted leaf into the central hub of its orb-web that is used as a retreat. This species is unusual among orb-weaving
spiders because males cohabit in the leaf retreat with both immature and mature females, mating with the former shortly after
the female molts. Cohabitation appears to be a form of mate-guarding because cohabiting males respond agonistically to rival
males that venture onto the web, and their behaviour depends upon the reproductive status of the female; males defending immature
females are more aggressive than those defending virgin, adult females. Males copulate with previously mated females for significantly
longer than with virgin females. Females may cannibalise cohabiting males, which occurs independently of whether the female
has been deprived of food. Females that cannibalise a single male do not have a higher fecundity than non-cannibalistic females.
Received: 2 February 1996 / Accepted after revision: 27 October 1996 相似文献
55.
56.
Contradictory findings in studies of sex ratio variation in roe deer (Capreolus capreolus) 总被引:3,自引:0,他引:3
A. J. Mark Hewison Reidar Andersen Jean-Michel Gaillard John D. C. Linnell Daniel Delorme 《Behavioral ecology and sociobiology》1999,45(5):339-348
Patterns of sex ratio variation and maternal investment reported in the literature are often inconsistent. This could be
due to intra- and inter-specific variation in social systems, but may also be a result of the a posteriori nature of much
of this type of analysis or the testing of models which are inappropriate. Two recent papers reported directly opposed results
concerning variation in offspring sex ratios in relation to maternal condition in roe deer, interpreting the results as support
for the Trivers and Willard model and for the local resource competition hypothesis, respectively. In this paper, we present
data on offspring sex ratios and early juvenile body weight from two long-term studies of this species to test predictions
arising from these two models concerning sex biases in litter composition and maternal care. First, we observed no consistent
pattern of sex differences in an index of weaning weight or body weight at 1 month old in either population, indicating a
lack of sex bias in maternal care. However, in one population, higher maternal body weight was associated with higher juvenile
body weight of daughters, but not of sons. Secondly, we found a negative, but not statistically significant, relationship
between maternal body weight and litter sex ratio such that heavier females tended to produce more daughters and lighter females
to produce more sons. These results indicate that roe females which have additional investment potential available do not
invest it in sons, as predicted by the Trivers and Willard model. Our results may provide some support that roe deer are subject
to local resource competition acting at the level of the individual mother; however, the fact that particular trends in sex
ratio data can be explained in functional terms provides no indication that they are actually adaptive.
Received: 9 December 1997 / Accepted after revision: 11 November 1998 相似文献
57.
Testis size variation in the greenfinch Carduelis chloris : relevance for some recent models of sexual selection 总被引:3,自引:0,他引:3
Interspecific evidence that testis size responds to selection caused by sperm competition has been obtained from many taxa. However, little is known about the sources of intraspecific variation in testis size, although such variation may have functional significance. Variation in testis size and asymmetry was studied within and between eight geographically separated (and genetically differentiated) populations of greenfinches Carduelis chloris. The relationships between testis size and plumage brightness (degree of yellowness) and the prevalence of haematozoan infections were also investigated in three of these populations, as they related to the predictions of the immunocompetence handicap hypothesis, and Møller's hypothesis relating directional testis asymmetry to phenotypic quality. There were large differences between populations in testis size, with males from northern populations having larger testes than those from southern populations. Within populations, large testes were associated with larger body size and greater age. When the influence of these factors was removed statistically, males with large testes were more likely to be infected with haematozoan parasites, and had brighter yellow plumage. No evidence was found that directional asymmetry in testis size was related to either of these measures of phenotypic quality. These results are consistent with the hypothesis that males with large testes, while signalling higher phenotypic quality as revealed by increased plumage brightness, also pay a cost in terms of reduced immunocompetence, revealed by the increased probability of infection in these males. That these patterns were similar in three different populations adds further strength to these conclusions. Our results suggest that studying the sources of variation in testis size among individuals can reveal interesting processes in sexual selection. 相似文献
58.
比较研究了林下和撂荒地生境有无竞争条件下紫茎泽兰(Ageratina adenophora(Sprengel))幼苗的生长特征、生长速率、生物量和种内竞争的形态反应。结果表明:(1)2类生境条件下紫茎泽兰植株幼苗形态特征基本一致,无竞争条件下紫茎泽兰幼苗根长和叶片数明显高于在竞争条件下对应指标值;(2)同类生境中,在无竞争条件下紫茎泽兰幼苗的生长速率、生物量积累显著比在竞争条件下的高;(3)不同生境中,撂荒地生境紫茎泽兰幼苗生物量显著高于林下生境的值,在无竞争条件下,林下生境紫茎泽兰幼苗生长速率比撂荒地生境的高,而在竞争条件下反之;(4)林下和撂荒地生境紫茎泽兰幼苗植株竞争强度差异不显著,但在林下生境其地上部分的竞争强度显著大于其在撂荒地生境的值,而根的竞争强度相反。可见,紫茎泽兰幼苗在种群建立的过程中具有不同的生态适应性和形态反应,这可能是其能成功入侵不同生境的一种重要生理生态策略。 相似文献
59.
Exploring the administrative mechanism of China's Paired Assistance to Disaster Affected Areas programme 下载免费PDF全文
The Paired Assistance to Disaster Affected Areas (PADAA) programme is a mutual aid initiative with Chinese characteristics, which speeded up the process of restoring and reconstructing regions affected by the Wenchuan earthquake on 12 May 2008. 1 The PADAA is an efficient instrument for catastrophe recovery, yet it remains a mysterious mechanism to many members of disaster management communities. This paper aims to lift the veil on it by assessing its origins and evolution. It draws on the multi‐level moderated competition model to explain how the PADAA functions within the Chinese administrative system. The country's top‐down political system allows the central authority to mandate provincial and local governments from more economically developed regions to assist devastated areas with post‐disaster reconstruction. The practices of local accountability complement vertical control by giving leaders from donor regions strong incentives to accomplish assigned reconstruction tasks, resulting in intense competition between them. 相似文献
60.
Sperm number is often a good predictor of success in sperm competition; however, it has become increasingly clear that, for
some species, variation in probability of paternity cannot be explained by sperm number alone. Intraspecific variation in
ejaculate characteristics, such as the number of viable sperm and sperm longevity, may play an equally important role in determining
fertilization success. Here, we assess variation among ejaculates in three factors that may contribute to fertilization success
(number of sperm per ejaculate, viability, and longevity), in a population of Peron’s tree frog (Litoria peronii). We detected large variation among males in the number of sperm per ejaculate and the proportion of viable sperm within
ejaculates, which could not be explained by variation in either male size or body condition. However, the proportion of viable
sperm released by males increased over the season. Finally, we assessed sperm longevity (proportion viable sperm determined
using a dual-fluorochrome vital dye) at two different temperatures. At 23°C, on average, 75% of sperm remained viable after
2 h, but there were significant differences amongst males with the percentage of viable sperm ranging from 43% to 95%. For
sperm incubated at 4°C, ejaculates varied fivefold in sperm longevity with some males having 50% viable sperm after 5 days.
Our data suggest that ejaculate characteristics (sperm number, viability, and longevity) vary widely in Peron’s tree frog
and may therefore play an important role in determining siring success both in the presence and absence of sperm competition.
We discuss the results in relation to selection on ejaculate traits via natural and sexual selection in this and other amphibians. 相似文献