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Ultimate Factors (ultimate + factor)
Selected AbstractsThe role of food supply in the dispersal behaviour of juvenile Tawny Owls Strix alucoIBIS, Issue 2 2003C. F. Coles We investigated the effects of food supply on decisions made by dispersing juvenile Tawny Owls Strix aluco in Kielder Forest, Northumberland, in 1996 and 1997. Field Voles Microtus agrestis were the main food of the owls and clear-cuts the main habitat for voles. A vole sign index was used to estimate vole abundance. In areas near to roosting owls, mean vole densities were 83 and 115 ha,1 in 1996 and 1997, respectively. The prediction that birds would perform area-restricted searches when prey was more abundant was not confirmed. Moreover, we found no evidence that juveniles avoided conspecifics. Owls appeared to have an imperfect knowledge of the environment as they responded to variability in Field Vole densities by altering the time spent in different areas rather than by moving to areas with successively greater vole densities. Vole abundance explained 25.7% of the variation in the time spent in different areas. Movements did not decrease with time after dispersal, although the detection of such movements was prone to error. This study supports recent work suggesting that although dispersal may be initiated by a variety of proximate and ultimate factors, individual decisions made during dispersal may depend partly on environmental conditions encountered during the process itself. [source] Habitat Characteristics of Eurytemora lacustris(Poppe, 1887) (Copepoda, Calanoida): The Role of Lake Depth, Temperature,Oxygen Concentration and Light IntensityINTERNATIONAL REVIEW OF HYDROBIOLOGY, Issue 3 2005Peter Kasprzak Abstract Field observations, laboratory experiments and a literature survey were conducted to evaluate the habitat characteristics of Eurytemoralacustris (Poppe 1887), a freshwater calanoid copepod species. Combined effects of temperature and oxygen concentration in the deep water of thermally stratifying lakes seem to be the ultimate factors governing the occurrence of the species throughout its home-territory. E. lacustris is largely restricted to relatively deep lakes (>30 m) providing a hypolimnetic refuge characterised by low temperatures (<,10 °C) and oxygenated water during summer. Therefore, although the species is spread over much of Europe it was only found in a small number of lakes. Long-term records in different lakes revealed E. lacustris to be perennial with relatively high biomasses occurring from May to September. During thermal stratification on average 87% of the nauplii and 72% of the copepodite biomass was found in hypolimnetic waters colder than 10 °C. Diurnal vertical migration was observed for the copepodid stages, but the migration amplitude clearly decreased from May to September. The migration amplitude was significantly related to light intensity. According to its special habitat requirements, E. lacustris might be considered a glacial relict sensitive to temperature increase and oxygen depletion. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Condition-dependent traits and the capture of genetic variance in male advertisement songJOURNAL OF EVOLUTIONARY BIOLOGY, Issue 4 2004L. S. E. Brandt Abstract The occurrence of additive genetic variance (VA) for male sexual traits remains a major problem in evolutionary biology. Directional selection normally imposed by female choice is expected to reduce VA greatly, yet recent surveys indicate that a substantial amount remains in many species. We addressed this problem, also known as the ,lek paradox', in Achroia grisella (Lepidoptera: Pyralidae), an acoustic moth in which males advertise to females with a pulsed ultrasonic song. Using a standard half-sib/full-sib breeding design, we generated F1 progeny from whom we determined VA and genetic covariance (COVA) among seven traits: three song characters, an overall index of song attractiveness, nightly singing period, adult lifespan, and body mass at adult eclosion. Because A. grisella neither feed nor drink as adults, the last trait, eclosion body mass, is considered a measure of ,condition'. We found significant levels of VA and narrow-sense heritabilities (h2) for all seven traits and significant genetic correlations (= COVAi,j /,(VA i·VA j)) between most pairs of traits (i, j). Male attractiveness was positively correlated with body mass (condition), adult lifespan, and nightly singing period, which we interpret as an energy constraint preventing males in poor condition from singing attractively, from singing many hours per night, and from surviving an extended lifespan. The positive genetic correlation (r = 0.79) between condition and attractiveness, combined with significant levels of VA for both traits, indicates that much of the variation in male song can be explained by VA for condition. Finally, we discuss the morphological and physiological links between condition and song attractiveness, and the ultimate factors that may maintain VA for condition. [source] Spatial and temporal variation in the fruiting phenology of palms in isolated standsPLANT SPECIES BIOLOGY, Issue 1 2008GREGORY H. ADLER Abstract Fruiting phenologies of two species of palms, Astrocaryum standleyanum L. H. Bailey and Attalea butyracea (Mutis ex L. f) Wess. Boer, isolated on eight small (1.7,3.7 ha) forested islands in the Panama Canal were studied over a 33-month period. Individual palms were permanently marked with numbered aluminum tags and censused each month for the presence of ripe fruits. The dataset consisted of 1106 monthly observations of palms with ripe fruits among the 634 marked individuals. Mean densities of palms of reproductive size varied widely among islands, ranging from a low of 0.3 ha,1 for A. standleyanum and 3.5 ha,1 for A. butyracea to a high of 44.9 ha,1 for A. standleyanum and 33.7 ha,1 for A. butyracea. Both species showed distinctly seasonal periods of fruiting activity that varied in duration between the two species and among years. The timing of fruiting by A. standleyanum was highly synchronous among islands, whereas inter-island synchrony in A. butyracea was less pronounced. The percentages of marked individuals that fruited varied widely among islands and years. Results indicated that these palms responded to both spatially and temporally variable conditions that promoted fruit production. We suggest that pollinator abundances are a crucial factor affecting reproductive output. Conditions that favor successful reproduction and seed dispersal, such as pollinator activity and the attraction of dispersal agents, may be the ultimate factors that have influenced the reproductive phenologies of these two species of palms. [source] Offspring size and survival in the frog Rana latastei: from among-population to within-clutch variationBIOLOGICAL JOURNAL OF THE LINNEAN SOCIETY, Issue 4 2009GENTILE FRANCESCO FICETOLA Egg size is considered to be a major maternal effect for offspring in oviparous organisms. It has profound consequences on fitness, and differences in egg size are viewed as plastic responses to environmental variability. However, it is difficult to identify the effect of egg size per se because egg size can covary with genetic features of the mother and with other nongenetic factors. We analysed the relationship between offspring starting size (i.e. a proxy of egg size) and larval survival in the frog Rana latastei. We analysed this relationship: (1) among five populations at different altitudes; (2) among clutches laid from different females; and (3) among siblings within clutches, to evaluate the effect of starting size. We observed differences among populations for offspring size, but starting size was not related to altitude or genetic diversity. Mortality was higher in populations and families with small average starting size; however, among siblings, the relationship between starting size and mortality was not verified. The relationship observed among clutches may therefore be caused by covariation between egg size and other effects. This suggests that the covariation between egg size and other effects can result in apparent relationships between egg size and fitness-related traits. Proximate and ultimate factors can cause the phenotypic variation of hatchlings in the wild, and key traits can be related to this variation, but the underlying causes require further investigation. © 2009 The Linnean Society of London, Biological Journal of the Linnean Society, 2009, 97, 845,853. [source] | ||||||||||