Jacob Höglund

Patterns of Fluctuating Asymmetry in Avian Feather Ornaments: Implications for Models of Sexual Selection

Extravagant secondary sexual characters, i.e. sexual ornaments, are exaggerated, often bilaterally symmetrical traits of great intricacy of design. The full expression of such traits is likely to be very costly and close to the limits of production. Any kind of environmental stress is therefore more likely to affect the expression of ornaments than that of any other morphological trait not subjected to strong directional selection. One measure of the ability of individuals to produce extravagant sexual traits is their degree of fluctuating asymmetry. This occurs when symmetry is the normal state and there is no tendency for the trait on one side of the body to have larger character values than that on the other. The degree of fluctuating asymmetry has been shown to reflect the ability of individuals to cope with a wide array of environmental stress (review in Parsons (1990)). We predicted that sexual ornaments should show a larger degree of fluctuating asymmetry than other morphological traits or than homologous traits in non ornamented species. If ornaments honestly indicate the quality of individuals, high quality individuals should develop little asymmetry and large traits. Thus, we predicted a general negative relation between the degree of asymmetry and the size of ornaments. This should not be the case for other traits or for homologous traits in conspecific females or in either sex of monomorphic species. We tested these predictions on elaborate feather ornaments in birds, as these have been shown to be used as cues during female choice. We made pairwise comparisons between males and females of ornamented species and between males of ornamented and of non-ornamented, confamilial species. Sexual ornaments showed both a larger absolute and relative degree of fluctuating asymmetry than did wing length or did traits homologous to the feather ornament in females and in males of non-ornamented species. The degree of fluctuating asym m etry for tail ornaments generally showed a negative relation with the size of the ornament, whereas that was not the case for wing length or for traits homologous to the feather ornament in females and in males of non-ornamented species. The large degree of fluctuating asymmetry in ornam ents and the negative relation between ornament size and degree of asymmetry suggest that fluctuating asymmetry in ornaments reliably reflects male phenotypic quality.

Copying and sexual selection

Recent studies of a variety of polygynously mating animals indicate that females do not always choose mates independently, but instead may copy the choices of others. Copying could serve either to increase the accuracy of mate assessment or to reduce its costs. It is also likely to affect the intensity of sexual selection.

Genomics and the challenging translation into conservation practice

The global loss of biodiversity continues at an alarming rate. Genomic approaches have been suggested as a promising tool for conservation practice as scaling up to genome-wide data can improve traditional conservation genetic inferences and provide qualitatively novel insights. However, the generation of genomic data and subsequent analyses and interpretations remain challenging and largely confined to academic research in ecology and evolution. This generates a gap between basic research and applicable solutions for conservation managers faced with multifaceted problems. Before the real-world conservation potential of genomic research can be realized, we suggest that current infrastructures need to be modified, methods must mature, analytical pipelines need to be developed, and successful case studies must be disseminated to practitioners.

Spatial pattern of MHC class II variation in the great snipe (Gallinago media)

The genes of the major histocompatibility complex (MHC) code for proteins involved in antigen recognition and triggering of the adaptive immune response, and are therefore likely to be under selection from parasites. These selection regimes may vary in space and time. Here we report a strong geographical structure in MHC class II B genes of a migrating bird, the great snipe (Gallinago media). Genetic differentiation in the MHC between two ecologically distinct distributional regions (Scandinavian mountain populations vs. East European lowland populations) was still present after statistically controlling for the effect of selectively neutral variation (microsatellites) using partial Mantel tests. This suggests a role for selection in generating this spatial structure and that it represents local adaptation to different environments. Differentiation between populations within the two regions was negligible. Overall, we found a high number of MHC alleles (50, from 175 individuals). This, together with a tendency for a higher rate of nonsynonymous than synonymous substitutions in the peptide binding sites, and high Tajimas D in certain regions of the gene, suggests a history of balancing selection. MHC variation is often thought to be maintained by some form of balancing selection, but the nature of this selection remains unclear. Our results support the hypothesis that spatial variation in selection regimes contributes to the high polymorphism.

From connectivity to isolation: genetic consequences of population fragmentation in capercaillie across Europe

The capercaillie inhabits a continuous range in large parts of the Palearctic boreal forest, but is patchily distributed in temperate Europe. An ongoing population decline, largely related to human land use changes, has been most pronounced in central and western Europe, where some local populations have become extinct. In this study, we document the genetic differentiation of capercaillie populations at different stages along a gradient of spatial structuring from high connectivity (continuous range in the boreal forest) to a metapopulation systems (Alps) and recent (central Europe) and historic (Pyrenees) isolation. Four hundred and sixty individuals from 14 sample sites were genotyped at 10 polymorphic microsatellite loci to assess genetic structure and variation of capercaillie populations across its European range. As expected, differentiation was least pronounced within the continuous range in the boreal forest. Within the metapopulation system of the Alps, differentiation was less than among the isolated populations of central Europe (Black Forest, Fichtelgebirge, Thuringia, Vosges). In the long‐isolated population of the Pyrenees, and the recently isolated populations of central Europe, genetic diversity was significantly reduced compared with the Alps and boreal forest. Our results agree with the concept of a gradual increase in genetic differentiation from connectivity to isolation, and from recent to historic isolation. Anthropogenic habitat deterioration and fragmentation thus not only leads to range contractions and extinctions, but may also have significant genetic and evolutionary consequences for surviving populations. To maintain high levels of genetic variation in species in fragmented habitats, conservation should aim at securing connectivity between spatially distinct populations.

Size and Plumage Dimorphism in Lek-Breeding Birds: A Comparative Analysis

It has often been taken for granted that, among lekking avian species more than among species with other mating systems, males are larger and more brightly colored than females as a result of strong sexual selection. This assumption, however, is not supported by a phylogenetic analysis. In families with at least one lekking species, where phylogenies could be reconstructed, both plumage dimorphism (males being more brightly colored) and size dimorphism were not correlated with lekking. It was also found that lekking did not precede dimorphism more often than the reverse in the phylogenies for which the temporal order of these two events could be determined. Larger males are found particularly in species with ground displays. It is suggested that size monomorphism may be explained by selection for small agile males in species with aerial and/or arboreal displays. Although lekking seems to have favored the evolution of plumage dimorphism in some groups, it is suggested that in other groups sexual selection may have acted on acoustic displays.It has often been taken for granted that, among lekking avian species more than among species with other mating systems, males are larger and more brightly colored than females as a result of strong sexual selection. This assumption, however, is not supported by a phylogenetic analysis. In families with at least one lekking species, where phylogenies could be reconstructed, both plumage dimorphism (males being more brightly colored) and size dimorphism were not correlated with lekking. It was also found that lekking did not precede dimorphism more often than the reverse in the phylogenies for which the temporal order of these two events could be determined. Larger males are found particularly in species with ground displays. It is suggested that size monomorphism may be explained by selection for small agile males in species with aerial and/or arboreal displays. Although lekking seems to have favored the evolution of plumage dimorphism in some groups, it is suggested that in other groups sexual selection ...

Inbreeding depression and male fitness in black grouse

The male lifetime lekking performance was studied, and related to inbreeding‐outbreeding in a wild population of black grouse (Tetrao tetrix) in central Finland between 1989 and 1995. Inbreeding was measured as the mean heterozygosity and mean d2 of 15 microsatellite loci. We found a significantly positive relationship between mean d2 and lifetime copulation success (LCS), while the relationship between heterozygosity and LCS was close to significant. We also found that males that never obtained a lek territory had significantly lower mean heterozygosity than males that were observed on a territory at least during one mating season in their life. Furthermore, among males that were successful in obtaining a lek territory, LCS and mean d2 were highest for those males that held central territories. We suggest that inbred males have a disadvantage (or outbred males have an advantage) in the competition for territories that may explain the relationships with LCS and inbreeding. Furthermore, the fact that mean d2 was positively correlated with LCS whereas heterozygosity was not when we restricted the analysis to territorial males, suggests that mean d2 provides more information about levels of inbreeding‐outbreeding than heterozygosity alone, and potentially highlights the effects of heterosis. To our knowledge, this is the first time that measures of inbreeding and lifetime fitness have been linked in a non‐isolated population. This is important in establishing that the relationships found in previous studies are not artefacts of low gene flow created by limited dispersal but a general feature of wild vertebrate populations.

Sexual selection in a monomorphic lek-breeding bird: correlates of male mating success in the great snipe Gallinago media

SummaryIn the lek-breeding great snipe, male morphology, behaviour, and territory features were recorded for individually marked birds on two adjacent leks. Partial correlation sshowed that male mating success, expressed as the number of female solicitations and copulations, was negatively correlated with the distance of a display territory to the lek center and positively correlated with the number of displays per unit time given by a male. No other variables were directly correlated with male matin success. Thus, central males obtain more matings than peripheral males and successful males display more per unit time than do less successful males, independently of position on the lek. Central males were found to be older than peripheral ones and were present more often on the lek. Furthermore, central males had a larger number of white tail feathers, which are usea as visual signals in the displays, but this may be explained by the fact that these males were older. It is suggested that male great snipe are subject to sexual selection mainly in behavioural and vocal cues and that this may explain the absence of size and plumage dimorphism in this species.

Microsatellite markers reveal the potential for kin selection on black grouse leks

The evolution of social behaviour has puzzled biologists since Darwin. Since Hamiltons theoretical work in the 1960s it has been realized that social behaviour may evolve through the effects of kinship. By helping relatives, an individual may pass on its genes despite negative effects on its own reproduction. Leks are groups of males that females visit primarily to mate. The selective advantage for males to join such social groups has been given much recent attention, but no clear picture has yet emerged. Here we show, using microsatellite analysis, that males but not females of a lekking bird (the black grouse, Tetrao tetrix) are genetically structured at the lek level. We interpret this structuring to be the effects of strong natal philopatry in males. This has the consequence that males on any specific lek should be more related than expected by chance as indicated by our genetic data. Our results thus suggest that kin selection is a factor that needs to be considered in the evolution and maintenance of the lek mating system in black grouse and sheds new light on models of lek evolution.

Fine-scale genetic structuring on Manacus manacus leks

Leks have traditionally been considered as arenas where males compete to attract females and secure matings. Thus, direct fitness benefits mediated through competition between males to fertilize females have been considered to be the primary force driving the evolution of lekking behaviour. Inclusive fitness benefits mediated through kin selection may also be involved in lek formation and evolution, but to date this theory has been largely ignored. According to kin-selection theory, both reproducing and non-reproducing males may gain indirect inclusive fitness benefits. If females are attracted to larger leks, non-reproducing males add attractiveness to a lek, and therefore, in a genetically structured population, boost the reproductive success of kin. Theory predicts that the attractiveness of leks is plastic, and that males establish themselves on a lek in which the top male, in terms of reproductive success, is a close relative. Here we show that in white-bearded manakins (Manacus manacus), for which larger leks are more attractive to females and so secure the maximum number of matings, there is extraordinary fine-scale genetic structure, with leks being composed of clusters of related kin. We propose that males establish themselves where they find relatives to such an extent that they form groups within leks, and that such behaviour is consistent with kin-selection theory to maximize reproductive success of the group.