Fluctuating optimum and temporally variable selection on breeding date in birds and mammals

International audienceTemporal variation in natural selection is predicted to strongly impact the evolution and demography of natural populations, with consequences for the rate of adaptation, evolution of plasticity, and extinction risk. Most of the theory underlying these predictions assumes a moving optimum phenotype, with predictions expressed in terms of the temporal variance and autocorrelation of this optimum. However, empirical studies seldom estimate patterns of fluctuations of an optimum phenotype, precluding further progress in connecting theory with observations. To bridge this gap, we assess the evidence for temporal variation in selection on breeding date by modeling a fitness function with a fluctuating optimum, across 39 populations of 21 wild animals, one of the largest compilations of long-term datasets with individual measurements of trait and fitness components. We find compelling evidence for fluctuations in the fitness function, causing temporal variation in the magnitude, but not the direction of selection. However, fluctuations of the optimum phenotype need not directly translate into variation in selection gradients, because their impact can be buffered by partial tracking of the optimum by the mean phenotype. Analyzing individuals that reproduce in consecutive years, we find that plastic changes track movements of the optimum phenotype across years, especially in bird species, reducing temporal variation in directional selection. This suggests that phenological plasticity has evolved to cope with fluctuations in the optimum, despite their currently modest contribution to variation in selection

Lästige Gäste - Parasiten der Vögel

Das Gefieder der Vögel ist ein idealer Lebensraum und ein Schlaraffenland für Parasiten aller Art. Die einen ernähren sich von Hautschuppen, andere von Federmaterial und wieder andere zapfen die Blutbahnen an. Im Normalfall stellen die sechs- bis achtbeinigen Mitbewohner kein Problem für ihre Wirte dar. Doch wie immer ist das Mass entscheidend

Die Mauser der Wasseramsel Cinclus cinclus und der Bezug zu Geschlecht, Alter und Bruttermin

Ongoing studies in the region of Zurich, Switzerland, on the Dipper date back to 1987. The Dipper population (about 25 breeding pairs) is located on two streams flowing into Lake Zurich. All the birds are individually marked. Over the years moult records on 247 individuals trapped once or repeatedly per season were collected, however, due to re-trapping of individuals total number of records amounted to 358. Exact age of 238 individuals was known. Moult process was outlined on the basis of all primaries and the outer six secondaries as well as in tail feathers (rectrices). All birds recorded belong to the local population, thus data on individuals and their breeding specifics had been collected over the years and could thus be analysed as to their influence on the moult process. Among passerines flight feather moult in Dippers is exceptional. Feather replacement occurs in accelerated and sporadic waves. This particular trait however does not shorten the overall time required for a moult: the waves occur in sequences and between these periods moult is slowed down. Moult in the secondaries, which, in general, is not initiated until the primaries have obtained their second wave, follows the same pattern. For the Dipper, moult starts on 23 June and ends on 15 September on average; 95% of all initiations lie between 1 June and 15 July. Moult lasts 80 to 88 days (84 days on average) and is thus within the range known for other similar songbird species. No support was found of the hypothesis that given its aquatic lifestyle at least two thirds of the wing feathers have to be intact. Observations on behaviour show that during moult the Dipper forages on the bankside or in shallow water. Analyses of stomach content have confirmed this behaviour. During the stage in which a massive loss of feathers occurs real diving is very rare and the Dipper becomes quite sedentary and even cryptic with otherwise little activity evident. Its wave-like moult seems to be a compromise between a short moulting period within which flight and diving capability is limited. On the whole, male Dippers start to moult 5.2 days earlier than females. A comparison of age classes shows that 89 of secondyear birds initiate moult 5.6 days prior to the 149 older-than-second-year birds. The earlier moult in second-year birds can be explained by the fact that they have retained their plumage for a longer time (hatching date to average moult date in their second year versus average moult date to average moult date in older-than-second-year birds). Among the older-than-secondyear birds the median starting date remains stable. A striking difference becomes evident when comparing 176 early breeders (brood or young reaching independence prior to 22 June) with 71 late breeders (breeding activites after 22 June): the advance group begins moulting 12.5 days earlier than those birds with prolonged breeding acitvities. Within the delayed group males moult 6.1 days earlier than females. In conclusion, moult is dependent on sex, breeding date and breeding activity as well as age

Bachforelle Salmo trutta fario erbeutet junge Wasseramsel Cinclus cinclus

In an area of 200 km2 in the region of Zurich, Switzerland, White-throated Dipper were ringed continuously since 1987. Out of 8827 nestlings and adults a total of 93 individuals (1.1%) were reported dead to the Swiss Ornithological Institute. Within these reports was a spectacular one: A young Dipper has been found in the stomach of a Brown Trout Salmo trutta fario, being catched by an angler in a one-meter deep stilling basing of a small stream. The fish had a total lenght of 38 cm and a weight of 80 g. The Dipper was one of three nestlings ringed five days before in nest situated 20 meters upstream. When predated it was about 18 days old and therefore not yet able to fly sufficiently. To our knowledge such an incidence has never been reported, neither for White-throated Dipper predated by fish nor for Brown Trout having swallowed a songbird

Attraktivität von zwei Schlafplätzen der Wasseramsel Cinclus cinclus

At nighttime the European Dipper is known to frequent nest boxes or nests from the previous year. Birds use such structures individually as space inside is limited. The European Dipper, will, though, occasionally choose spacious tunnels or sections of buildings as roosting sites which they share with other individuals. Temperature seems to be the decisive factor determing the quality of a roost site. Two sites, a small one visited by individuals or pairs and a larger second one which attracted up to 11 individuals were selected for a study carried out consecutively from 1992, 1997 to 2016 respectively. Both roosting sites were located in tunnel-shaped shafts close to streams and rivers. In both shafts temperatures were higher than in comparable open locations. As winter progressed the number of birds roosting at the sites decreased. This chronological phenology can be ascribed to the species’ territorial behavior and early initiation of breeding. Apparently, once birds have chosen a particular site to roost in, they have made a choice that lasts a lifetime

Becker-et-al_JEB_pedigree

Pedigree Data White-throated dipper (Cinclus cinclus), Pruned Pedigree, Long-term Study Zurich, Switzerland

Data from: Phenotype-associated inbreeding biases estimates of inbreeding depression in a wild bird population

Inbreeding depression is usually quantified by regressing individual phenotypic values on inbreeding coefficients, implicitly assuming there is no correlation between an individual's phenotype and the kinship coefficient to its mate. If such an association between parental phenotype and parental kinship exists, and if the trait of interest is heritable, estimates of inbreeding depression can be biased. Here we first derive the expected bias as a function of the covariance between mean parental breeding value and parental kinship. Subsequently, we use simulated data to confirm the existence of this bias, and show that it can be accounted for in a quantitative genetic animal model. Finally, we use long-term individual-based data for white-throated dippers (Cinclus cinclus), a bird species in which inbreeding is relatively common, to obtain empirical estimate of this bias. We show that during part of the study period, parents of inbred birds had shorter wings than those of outbred birds, and as wing length is heritable, inbred individuals were smaller, independent of any inbreeding effects. This resulted in the overestimation of inbreeding effects. Similarly, during a period when parents of inbred birds had longer wings, we found that inbreeding effects were underestimated. We discuss how such associations may have arisen in this system, and why they are likely to occur in others, too. Overall, we demonstrate how less biased estimates of inbreeding depression can be obtained within a quantitative genetic framework, and suggest that inbreeding and additive genetic effects should be accounted for simultaneously whenever possible

Becker-et-al_JEB_wing-data

Morphological Data, White-throated dipper (Cinclus cinclus), Long-term Study Zurich, Switzerland. See file for more information