When Less Is Best: Female Brown-Headed Cowbirds Prefer Less Intense Male Displays

Sexual selection theory predicts that females should prefer males with the most intense courtship displays. However, wing-spread song displays that male brown-headed cowbirds (Molothrus ater) direct at females are generally less intense than versions of this display that are directed at other males. Because male-directed displays are used in aggressive signaling, we hypothesized that females should prefer lower intensity performances of this display. To test this hypothesis, we played audiovisual recordings showing the same males performing both high intensity male-directed and low intensity female-directed displays to females (N = 8) and recorded the females' copulation solicitation display (CSD) responses. All eight females responded strongly to both categories of playbacks but were more sexually stimulated by the low intensity female-directed displays. Because each pair of high and low intensity playback videos had the exact same audio track, the divergent responses of females must have been based on differences in the visual content of the displays shown in the videos. Preferences female cowbirds show in acoustic CSD studies are correlated with mate choice in field and captivity studies and this is also likely to be true for preferences elucidated by playback of audiovisual displays. Female preferences for low intensity female-directed displays may explain why male cowbirds rarely use high intensity displays when signaling to females. Repetitive high intensity displays may demonstrate a male's current condition and explain why these displays are used in male-male interactions which can escalate into physical fights in which males in poorer condition could be injured or killed. This is the first study in songbirds to use audiovisual playbacks to assess how female sexual behavior varies in response to variation in a male visual display

The role of vanillin and p-coumaric acid in the growth of Scotch pine seedlings

It was stated that vanillin and p-coumaric acid used at concentrations 10-8-10-5M stimulated the growth of pine seedlings. Most effective were these substances used at concentration 10-7M. Both phenolic compounds stimulated the elongation, fresh and dry weight in very young seedlings (up to 3-4 weeks) and increased the fresh and dry weight only in older ones (7 weeks). The stimulation of growth processes in pine seedlings treated with vanillin and p-coumaric acid coincided with the increase of auxins in roots and with the decrease of free gibberellins in these plant organs. Neither vanillin nor p-coumaric acid influenced the level of ABA-like inhibitor both in the shoots and roots of pine seedlings

A comparison between the effect of gibberellin and 2-chloroethyl trimethylammonium chloride (CCC) on some biochemical processes in bean plants. IV. Effect on the content of the inhibitor of absicisic acid properties

In shoots and in roots of bean seedlings the inhibitor of ABA-like properties was stated. Its level in shoots was increased by CCC and decreased in roots by GA3 treatment. Both -substances had neither synergistic nor antagonistic or additive effects on the level of LABA-like inhibitor. The effect of GA3 and CCC on the level of inhibitor was independent of the infuence of these substances on the growth processes. It has been concluded that the mode of action of GA and CCC in processes regulating the level of abscisic acid in plants is different for each of these substances

A comparison between the effect of gibberellin and 2-chloroethyl trimethylammonium chloride (CCC) on some biochemical processes in bean plants. IV. Effect on the content of the inhibitor of absicisic acid properties

In shoots and in roots of bean seedlings the inhibitor of ABA-like properties was stated. Its level in shoots was increased by CCC and decreased in roots by GA3 treatment. Both -substances had neither synergistic nor antagonistic or additive effects on the level of LABA-like inhibitor. The effect of GA3 and CCC on the level of inhibitor was independent of the infuence of these substances on the growth processes. It has been concluded that the mode of action of GA and CCC in processes regulating the level of abscisic acid in plants is different for each of these substances

Identification of QTLs for sex expression in dioecious and monoecious hemp (Cannabis sativa L.)

Hemp (Cannabis sativa L.) is a diploid species including both dioecious and monoecious cultivars with hetero- and homomorphic sex chromosomes, respectively. It displays a high plasticity of sex expression, i.e., the ratio of female and male flowers. In this study, we investigated the role of sex chromosomes in the genetic determinism of sex expression in dioecious and monoecious hemp. The experimental materials were three F1 segregating populations, two dioecious (C1 and C2: ‘Carmagnola’ ♀ × ‘Carmagnola’ ♂), and one monoecious (UF: ‘Uso 31’ × ‘Fedora 17’). A ‘sex’ phenotypic marker was mapped in C1 and C2. In total, 23, 42, and 26 AFLP markers (71 markers in total) were mapped to three, nine, and three co-segregation groups putatively located on sex chromosomes in C1, C2, and UF, respectively. Recombination rates with sex ranged from 0 to 0.5. Five sex-linked markers were detected in UF, revealing homologies between the X chromosomes of monoecious hemp and the X and Y chromosomes of dioecious hemp. Five QTLs associated with quantitative variations in sex expression were identified in each map. Four markers associated with variations in sex expression in UF segregated with sex or accounted for a putative QTL in C1 or C2. Two QTLs and three of these markers were mapped in UF in a region homologous to the sex-locus region of the dioecious maps. Given these results, conducting further research on the genetic determinism of sex expression in hemp using a quantitative approach appears relevant