Home About us Contact
|
Home About us Contact | ||
|
|
||
Male Mass (male + mass)
Selected AbstractsRepeatability of hematocrits and body mass of Gray CatbirdsJOURNAL OF FIELD ORNITHOLOGY, Issue 1 2010Margret I. Hatch ABSTRACT Hematocrits may provide information about the physiological condition of birds, but, to be a useful measure, information is needed concerning how hematocrits vary among individuals and over time. We examined the repeatability of hematocrits in a population of Gray Catbirds (Dumetella carolinensis) in Pennsylvania at several time scales and also examined the repeatability of body mass, another measure commonly used as an indicator of condition. Both hematocrit (r= 0.64) and mass (r= 0.65) were repeatable (P < 0.01) for first captures between years and between first and second captures within a year (r= 0.41 and r= 0.50, respectively; P < 0.01), but not repeatable (P > 0.05) between captures in different months within a year (r= 0.11 for both). Repeatability of both measures differed by sex and age. Females exhibited repeatability of hematocrit and body mass only between years, while male hematocrits were repeatable between years and between first and second captures within a season. Male mass was repeatable for all time periods. Hematocrits of younger birds were repeatable between captures within a season and their body mass was repeatable between months and weeks while hematocrits of older birds were not repeatable and their body mass was repeatable only between captures in a season. Our results indicate that hematocrits and body mass had similar repeatability coefficients overall, but that hematocrits of Gray Catbirds were a consistent trait of individuals only across years. Because repeatability between captures and months depended on sex and age, we conclude that the hematocrit is a useful measure of individual performance only in limited circumstances. RESUMEN El hematocrito podría proveer información sobre la condición física de las aves pero para ser una medida útil se necesita información sobre como el hematocrito varia entre individuos y a través del tiempo. Examinamos la repetibilidad del hematocrito en una población de Dumetella carolinensis en Pennsylvania durante diferentes escalas temporales. También examinamos la repetibilidad del peso corporal, otra medida comúnmente usada como indicador de la condición del individuo. El hematocrito (r= 0.64) y el peso corporal (r= 0.65) eran repetibles (P < 0.01) para las primeras capturas entre años y entre la primera y segunda captura dentro del año (r= 0.41 y r= 0.50, respectivamente; P < 0.01), pero no eran repetibles (P > 0.05) entre capturas realizadas en diferentes meses dentro del año (r= 0.11 para los dos). La repetibilidad de las dos medidas difiere por sexo y edad. Las hembras se caracterizaron por tener repetibilidad del hematocrito y del peso corporal solo entre años, mientras que el hematocrito de los machos era repetible entre años y entre la primera y segunda captura dentro de la temporada. El peso corporal de los machos era repetible durante todos los periodos a través del tiempo. El hematocrito de las aves mas jóvenes era repetible entre capturas dentro de la temporada y su peso corporal era repetible entre meses y semanas, mientras que el hematocrito de las aves mayores no era repetible y su peso corporal era repetible solo entre capturas dentro de la temporada. Nuestros resultados indican que los hematocritos y el peso corporal en general tuvieron coeficientes de repetibilidad similares, pero que los hematocritos de D. carolinensis eran un rasgo consistente de los individuos solo entre años. Por la razón que la repetibilidad entre capturas y meses dependía del sexo y edad, concluimos que el hematocrito es una medida útil del performance individual solo en circunstancias limitadas. [source] Female Preferences for Call Traits and Male Mating Success in the Neotropical Frog Physalaemus enesefaeETHOLOGY, Issue 2 2003Zaida Tárano Female preferences for male call traits may affect male mating success and the evolution of exaggerated secondary sexual traits. We used phonotaxis experiments to examine female preferences in the frog Physalaemus enesefae in relation to variation in male call duration, dominant frequency, intercall interval and amplitude (dB SPL). Females preferred long calls, low and average dominant frequency calls, short intercall intervals and more intense calls. We compared the patterns of female preferences with those of acoustic variation among males to test the prediction that properties with low within-male variation are associated with stabilizing or weakly directional female preferences, whereas properties with high within-male variation are associated with directional preferences. Females had weakly directional preferences for the dominant frequency of the call and strongly directional preferences for call duration and call rate. We also determined whether the temporal relationship between calls influenced preferences based on the dominant frequency of the call. Preferences for low-frequency over high-frequency calls disappeared when calls partially overlapped. Females preferred the leading call regardless of its dominant frequency. We also investigated mating patterns in the field. There was size-assortative mating, as male and female body sizes snout-vent length (SVL) were positively correlated. In addition, differences in the frequency distributions of body length (SVL) between mated and unmated males approached significance; lower SVL classes were underrepresented among mated males. These patterns may reflect female preferences for lower dominant frequency calls, as there is a negative correlation between male mass and the dominant frequency of the call. [source] Temperature and host species affect nuptial gift size in a seed-feeding beetleFUNCTIONAL ECOLOGY, Issue 6 2006C. W. FOX Summary 1In many insects species, males contribute large nutritional gifts to females during mating, generally as seminal fluids (ejaculates) or spermatophores. These nuptial gifts can affect both male and female fitness, and can mediate selection on male body size. However, it is unclear how environmental variables, such as temperature and diet, affect gift size and the consequences of gift size for male and female fitness. 2We examine how temperature and rearing host affect male nuptial gift size (both total ejaculate size and the proportion of a male's mass allocated to his seminal fluids), and the relationship between gift size and female reproduction, in two populations of the seed-feeding beetle Callosobruchus maculatus. 3Males reared at lower temperature (20 °C) produced substantially larger ejaculates than males reared at higher temperatures (25, 30 and 35 °C). However, males allocated a smaller proportion of their body mass to their ejaculate at the lowest temperature compared with other temperatures. This effect of temperature on male allocation to their ejaculates mirrored the effect of temperature on female body size , male ejaculate size remained a relatively constant proportion of their mate's body mass across temperatures. 4Rearing host also affected male ejaculate size but the magnitude and direction of the host effect differed between populations. 5Rearing temperature affected the relationship between male body mass and ejaculate size. Temperature also affected the relationship between female body mass and fecundity. The relationship between male body mass and ejaculate size was significantly lower when beetles were reared on cowpea than when beetles were reared on azuki or mung. 6We found no evidence that male body size or nuptial gift size affected female fecundity in either population of C. maculatus. We thus propose that the effect of nuptial gift size on male fitness is through a reduction in female mating frequency and thus increased paternity for males producing larger nuptial gifts. [source] DO FEMALE SPIDERS SELECT HEAVIER MALES FOR THE GENES FOR BEHAVIORAL AGGRESSIVENESS THEY OFFER THEIR OFFSPRING?EVOLUTION, Issue 6 2003S. E. RIECHERT Abstract., We explore the hypothesis that females choose to mate with heavier males for the genes for behavioral aggressiveness they offer their offspring in the desert spider, Agelenopsis aperta. Behavioral aggressiveness is important to competition for limited resources in the field and is thus correlated with the mass spiders achieve. We established four crosses based on the body mass relationships of parents subjected to selection in their natural environment (female mass/male mass: HI/HI, HI/LO, LO/HI, and LO/LO) and reared the F1 offspring in a noncompetitive laboratory environment. Offspring size and mass at maturity were measured, life history parameters recorded, and behavioral aggressiveness scored in a series of tests. Significant familial effects were detected in all of these measures, but pertinent cross effects were observed only in the assays measuring behavioral aggressiveness. The results were summarized in terms of the fitness costs to HI females of mating with LO males (fewer female offspring of the more aggressive phenotypes) and the benefits to LO females of mating with HI males (fewer fearful offspring of both sexes). [source] | ||||||||||