			Home About us Contact

Intrapopulation Variation (intrapopulation + variation)

Distribution by Scientific Domains

Life Sciences	75%

Selected Abstracts

Intrapopulation variation in reproduction by female eastern kingbirds Tyrannus tyrannus: the impacts of age, individual performance, and breeding site

JOURNAL OF AVIAN BIOLOGY, Issue 3 2004
Michael T. Murphy
I used data from a 13-year study of eastern kingbirds Tyrannus tyrannus from central New York, USA, to evaluate the relative impact of female age and body size on reproduction. I also calculated repeatabilities of reproductive traits for both females and the sites where they bred in an attempt to evaluate the relative contribution of each to intrapopulation variation in reproduction. Female age had a strong influence on timing of breeding (breeding date advanced by one day for each year of life), but was not a significant source of variation for clutch size, egg mass, number of young to hatch or fledge, or total seasonal production. Repeatabilities of breeding date for females and sites were both significant (0.284 and 0.181, respectively), but the only other significant repeatabilities were for female clutch size (0.282) and female egg mass (0.746). Among-year repeatabilities of breeding date for females who bred at two or more sites over their lifetime were as high as those for females that were site faithful. Thus, breeding date was probably affected independently by the female and site. No measure of productivity exhibited a repeatable pattern in comparisons made among females or sites. All reproductive traits were entered as dependent variables in a series of stepwise multiple regression analyses in an attempt to identify female properties (size, lifespan and condition) that might be linked proximately to differences in breeding statistics. I found that (a) large birds tended to breed the earliest, (b) clutch size was independent of female size, condition and lifespan, (c) female body size and egg size were correlated positively, but (d) production of young was independent of all measured female properties. Reproduction appears to be linked more closely to the female than to the site. Body size accounts for a portion of the repeatable portion of breeding date and egg mass, but most of the intrapopulation variation in these and other traits remained unexplained. [source]

Genetic structure in Atlantic brown trout (Salmo trutta L.) populations in the Iberian peninsula: evidence from mitochondrial and nuclear DNA analysis

JOURNAL OF ANIMAL BREEDING AND GENETICS, Issue 3 2000
S. Dunner
Summary Brown trout (Salmo trutta L.) was sampled in rivers belonging to three different Spanish basins in order to analyse the distribution of genetic variability. The genetic analysis was performed by using two systems and techniques: nuclear DNA was screened through random amplified polymorphic DNAs (screening 2 × 105 bp of the whole genome), and mitochondrial DNA (mtDNA) through sequencing of the hypervariable control region. Genetic distances between the populations were similar using either analysis although some differences arise. For example, some populations of the Tajo basin were very close through nuclear analysis but more distant using mtDNA. Differences between the two DNA sources could be the result of a different evolutionary rate, and the fact that mtDNA is maternally transmitted and differences in sex migration rates will influence the patterns of genetic variation between the transmitted DNAs. Total variation was partitioned using amova showing a clear subdivision among basins although intrapopulation variation remained as high as 62%. A correspondence analysis defined the differences in a three-dimensional way, clustering the populations according to their common basin. When mtDNA was sequenced, higher variability was noted in the segment between 400 and 600bp of the whole D-loop sequence, suggesting that these 200bp improved the analysis of the variability more than sequencing the t-RNA ends of the control region. A comparison was made between the t-RNAPro ends of the 10 populations screened here and the rest of the published sequences found in the literature, leading to a concentration of these populations in group IV which includes all trouts which originate in the Atlantic. The analyses performed suggest that a high genetic variability is present in all populations and that although there has been a probable interference from stocked strains introduced to increase population density, this was only detectable through the variance between rivers which reflect different policies according to the region where the basin is located. However, the genetic analysis using the two approaches allows the control of the natural populations avoiding a loss of their genetic potential. Zusammenfassung In drei verschiedenen spanischen Wassersystemen wurden Bachforellen (Salmo trutta L.) gesammelt, um die genetische Variabilität zu analysieren. Zur Analyse wurden zwei Systeme und zwei Techniken genutzt: Kern-DNA wurde mittels RAPD analysiert (2.105bp des Gesamtgenoms), mitochondriale DNA durch das Sequenzieren der hypervariablen Kontrollregion. Beide Techniken ergaben ähnliche genetische Distanzen zwischen den Populationen, obwohl Unterschiede bei Populationen aus dem Tajo-Gebiet auftraten, deren Kern-DNA eine sehr geringe Distanz aufwiesen, während die über Sequenzierung von mtDNA ermittelte Distanz auf größere Unterschiede hinwies. Diese Differenz könnte das Ergebnis unterschiedlicher Mutationsraten während der Evolution sein, oder auf dieTatsache zurückzuführen sein, daß mtDNA über die Mutterlinien weitergegeben wird, und Migrationsunterschiede zwischen den Geschlechtern die Muster der genetischen Variation der weitergegebenen DNA-Stücke beeinflußt. Die Gesamtvarianz wurde mit Hilfe von AMOVA analysiert, wobei zwischen den Wassersystemen eine eindeutige Unterteilung festgestellt werden konnte, obwohl die Varianz innerhalb der Population bei 62% liegt. Eine Korrespondenzanalyse erklärt die Distanzen dreidimensional, wodurch die Populationen gleicher Herkunft in Cluster zusammenfallen. Bei der Sequenzierung von mtDNA wurde eine größere Variabilität im Sequenzbereich zwischen 400 und 600 bp der gesamten D-Loop Sequenz festgestellt, was darauf schließen läßt, daß diese 200 bp für eine Analyse der Variabilität geeigneter sind als eine Sequenzierung der t-RNA Enden der Kontrollregion. Ein Vergleich der t-RNAPro Enden der zehn hier untersuchten Populationen und der bereits publizierten Sequenzen führen zu einer Konzentration dieser in der Gruppe IV, zu der alle Forellenpopulationen zählen, die aus dem Atlantik stammen. Die Untersuchung deutet auf eine hohe genetische Variabilität in allen Populationen hin und auf Interferenzen durch Aufstockungsmaßnahmen zur Erhöhung der Populationsdichten hin. Dies ist nur durch die Varianz zwischen den Flußsystemen aufzuklären, die von Region zu Region unterschiedliche Maßnahmen wiederspiegelt. Die genetische Analyse mittels dieser zwei Ansätze erlaubt eine Kontrolle der natürlichen Populationen zwecks Vermeidung eines Verlustes ihres genetischen Potentials. [source]

Food limitation explains most clutch size variation in the Nazca booby

JOURNAL OF ANIMAL ECOLOGY, Issue 4 2001
L. D. Clifford
Summary 1,Natural selection is expected to optimize clutch size, but intrapopulation variation is maintained in many bird species. The Nazca booby provides a simple system in which to investigate clutch size evolution because clutch size and brood size are decoupled due to obligate siblicide. The indirect effect of brood size on clutch size evolution can therefore be eliminated. 2,In Nazca boobies, second eggs provide insurance against the failure of the first egg or early death of the first hatchling, but approximately half of all females lay only one egg. We tested the hypothesis that one-egg clutches result from food limitation by providing female Nazca boobies with supplemental food. 3,A higher proportion of supplemented females produced two-egg clutches than did control females. Supplemented females produced larger second-laid eggs than did control females, but not first-laid eggs. Laying date and laying interval were not affected. 4,Comparisons of clutch size and egg volume between years indicated that the supplemental feeding experiment was not conducted in a year with a poor natural food supply. Thus supplemented females produced larger clutch sizes despite apparently normal natural food levels. 5,This experiment nearly completes our understanding of clutch size variation in the Nazca booby, and indicates that food limitation and the costs of egg-laying should be considered carefully in studies of clutch size evolution. [source]