Pollen competition reduces inbreeding depression in Collinsia heterophylla (Plantaginaceae)

We tested two predictions of the hypothesis that competition between self-pollen may mitigate negative genetic effects of inbreeding in plants: (1) intense competition among self-pollen increases offspring fitness; and (2) pollen competition reduces the measured strength of inbreeding depression. We used Collinsia heterophylla (Plantaginaceae), an annual with a mixed mating system, to perform controlled crosses in which we varied both the size of the pollen load and the source of pollen (self vs. outcross). Fitness of selfed offspring was higher in the high pollen-load treatment. Our second prediction was also upheld: inbreeding depression was, on average, lower when large pollen loads were applied (11%) relative to the low pollen-load treatment (28%). The reduction was significant for two fitness components relatively late in the life-cycle: number of surviving seedlings and pollen-tube growth rate in vitro. These findings suggest that intermittent inbreeding, which leads to self-fertilization in plants with genetic loads, may select for traits that enhance pollen competition.     

Juvenile hormone involvement in Drosophila melanogaster male reproduction as suggested by the Methoprene-tolerant mutant phenotype

Juvenile hormone (JH) involvement in male reproduction is poorly understood. In Drosophila melanogaster adults, JH deficiency has been shown to result in lowered protein synthesis in male accessory glands. To probe additional roles, we have examined males homozygous for a null allele of Methoprene-tolerant (Met). This gene is involved in the action of JH, possibly at the JH receptor level, and Met²⁷ null mutants reflect a diminution of JH action. Met²⁷ males were found to have reduced protein accumulation in male accessory glands and to court and mate wild-type females much less avidly than do either Met⁺ or Met²⁷; Met⁺ transgenic males. Exposure of Met²⁷ males to methoprene partially rescued the courtship deficiency. However, sperm transfer as reflected by fertility of Met²⁷ fathers was found to be similar to that of Met⁺. Taken together with previous work examining the JH-deficient mutant apterous, these results corroborate JH involvement in protein synthesis in the male accessory glands and suggest a role for JH in promoting male mating behavior in these flies.     

Juvenile hormone involvement in Drosophila melanogaster male reproduction as suggested by the Methoprene-tolerant(27) mutant phenotype

Juvenile hormone (JH) involvement in male reproduction is poorly understood. In Drosophila melanogaster adults, JH deficiency has been shown to result in lowered protein synthesis in male accessory glands. To probe additional roles, we have examined males homozygous for a null allele of Methoprene-tolerant (Met). This gene is involved in the action of JH, possibly at the JH receptor level, and Met²⁷ null mutants reflect a diminution of JH action. Met²⁷ males were found to have reduced protein accumulation in male accessory glands and to court and mate wild-type females much less avidly than do either Met⁺ or Met²⁷; Met⁺ transgenic males. Exposure of Met²⁷ males to methoprene partially rescued the courtship deficiency. However, sperm transfer as reflected by fertility of Met²⁷ fathers was found to be similar to that of Met⁺. Taken together with previous work examining the JH-deficient mutant apterous, these results corroborate JH involvement in protein synthesis in the male accessory glands and suggest a role for JH in promoting male mating behavior in these flies.     

When is it socially acceptable to feel sick?

Disease is a ubiquitous and powerful evolutionary force. Hosts have evolved behavioural and physiological responses to disease that are associated with increased survival. Behavioural modifications, known as ‘sickness behaviours’, frequently involve symptoms such as lethargy, somnolence and anorexia. Current research has demonstrated that the social environment is a potent modulator of these behaviours: when conflicting social opportunities arise, animals can decrease or entirely forgo experiencing sickness symptoms. Here, I review how different social contexts, such as the presence of mates, caring for offspring, competing for territories or maintaining social status, affect the expression of sickness behaviours. Exploiting the circumstances that promote this behavioural plasticity will provide new insights into the evolutionary ecology of social behaviours. A deeper understanding of when and how this modulation takes place may lead to better tools to treat symptoms of infection and be relevant for the development of more efficient disease control programmes.     

苍鹭孵化及育雏习性研究

1999、2000年3～6月,对辽宁省朝阳县树俩型苍鹭孵化习性和育雏习性进行观察。苍鹭孵化以雌鸟为主,两性轮流孵化,孵化期24～27天,平均孵化率93．5％;雏鸟为晚成鸟,育雏期40～50天左右,育雏过程分育雏初期、中期、末期三阶段;雏鸟的食物以鱼类、蚌类为主。     

Disentangling the effects of breakdown of self-incompatibility and transition to selfing in North American Arabidopsis lyrata

A breakdown of self‐incompatibility (SI) followed by a shift to selfing is commonly observed in the evolution of flowering plants. Both are expected to reduce the levels of heterozygosity and genetic diversity. However, breakdown of SI should most strongly affect the region of the SI locus (S‐locus) because of the relaxation of balancing selection that operates on a functional S‐locus, and a potential selective sweep. In contrast, a transition to selfing should affect the whole genome. We set out to disentangle the effects of breakdown of SI and transition to selfing on the level and distribution of genetic diversity in North American populations of Arabidopsis lyrata. Specifically, we compared sequence diversity of loci linked and unlinked to the S‐locus for populations ranging from complete selfing to fully outcrossing. Regardless of linkage to the S‐locus, heterozygosity and genetic diversity increased with population outcrossing rate. High heterozygosity of self‐compatible individuals in outcrossing populations suggests that SI is not the only factor preventing the evolution of self‐fertilization in those populations. There was a strong loss of diversity in selfing populations, which was more pronounced at the S‐locus. In addition, selfing populations showed an accumulation of derived mutations at the S‐locus. Our results provide evidence that beyond the genome‐wide consequences of the population bottleneck associated with the shift to selfing, the S‐locus of A. lyrata shows a specific signal either reflecting the relaxation of balancing selection or positive selection.     

Biparental care in incipient colonies of the dampwood termiteZootermopsis angusticollis Hagen (Isoptera: Termopsidae)

Parental care and division of labor in male and female primary reproductives in incipient colonies of the dampwood termite Zootermopsis angusticolliswere studied by recording repertory sizes, behavior frequencies, time budgets, and transition probabilities of acts. Repertory sizes for males and females were identical, and behaviors were performed at similar frequencies. Time budget data also suggested equal participation in parental care by both sexes. Transition probability analysis suggested that males and females did not organize their behavior in roles. We therefore found no indication of sex-based division of labor during colony foundation and the incipient stages of colony growth. The lack of behavioral specialization may be due to the fact that acts might be related and/or have more than one function, and different tasks are not spatially associated. Our observations are consistent with the hypothesis that monogamous mating systems in termites involve mate assistance.     

A Test of the Mating Limitation Hypothesis for Caste Determination in Evylaeus albipes (Hymenoptera: Halictidae), a Primitively Eusocial Halictine Bee

Yanega's (1997) mating limitation hypothesis (MLH) states that if a female mates promptly after emerging, she then becomes a member of the maximally reproductive behavioral caste (i.e., in most cases an overwintering gyne). Females that do not mate early become workers. We tested the MLH in laboratory colonies of a eusocial population of Evylaeus albipes. Of 24 worker brood females (13 from queenright and 11 from orphaned nests), 13 mated on the first day of flight activity and all mated within the first 5 days; there were no significant differences between mating rates of females from the two colony types. All 24 commenced foraging as workers after an average of between 3 and 4 days postmating. We conclude that the MLH does not apply to this species despite the fact that the only known halictine for which this hypothesis has been experimentally tested is the fairly closely related E. marginatus.