Linda A Whittingham

• PhD
• Professor (Full) at University of Wisconsin–Milwaukee

Large structural variants in the genome, such as inversions, may play an important role in producing population structure and local adaptation to the environment through suppression of recombination. However, relatively few studies have linked inversions to phenotypic traits that are sexually selected and may play a role in reproductive isolation....

Climate change models often assume similar responses to temperatures across the range of a species, but local adaptation or phenotypic plasticity can lead plants and animals to respond differently to temperature in different parts of their range. To date, there have been few tests of this assumption at the scale of continents, so it is unclear if t...

Significance Ornaments are thought to signal the genetic quality of males to females choosing mates, but the qualities they signal and why they sometimes vary between populations are poorly understood. Here, we show, within a single warbler species, that two plumage ornaments signal similar aspects of male quality (e.g., immunity and oxidative bala...

During migration, animals may experience high rates of mortality, but costs of migration could also be manifested through non-lethal carry-over effects that influence individual success in subsequent periods of the annual cycle. Using tracking data collected from light-level geolocators, we estimated total spring migration distance (from the last w...

There have been an increasing number of observations of itinerancy in migratory songbirds, where individuals move among 2 or more widely separated areas during the “stationary” nonbreeding season. Knowledge of such movements and an understanding of what drives them are important for predicting how migratory populations will respond to environmental...

The use of single nucleotide polymorphism (SNP) arrays to generate large SNP datasets for comparison purposes have recently become an attractive alternative to other genotyping methods. Although most SNP arrays were originally developed for domestic organisms, they can be effectively applied to wild relatives to obtain large panels of SNPs. In this...

Latitudinal differences in timing of breeding are well documented but how such differences carry over to influence timing of events in the annual cycle of migratory birds is not well understood. We examined geographical variation in timing of events throughout the year using light-level geolocator tracking data from 133 migratory tree swallows (Tac...

The evolution of the Major Histocompatibility Complex (MHC) is shaped by frequent gene duplications and deletions, which generate extensive variation in the number of loci (gene copies) between different taxa. Here, we collected estimates of copy number at the MHC for over 250 bird species from 68 families. We found contrasting patterns of copy num...

Genes of the major histocompatibility complex (MHC) are a critical part of the adaptive immune response, and the most polymorphic genes in the vertebrate genome, especially in passerine birds. This diversity is thought to be influenced by exposure to pathogens which can vary in relation to numerous factors. Migratory behaviour may be a particularly...

Habitat type can dramatically affect wildlife by influencing availability of resources (such as food) or behavior, which in turn can impact reproductive output. Human-dominated areas with short grass, such as golf courses, can provide habitat for wildlife but may have reduced arthropod abundance, which can lower habitat quality for birds. We invest...

Recent advancements in sequencing technology have resulted in rapid progress in the study of the Major Histocompatibility Complex (MHC) in non‐model avian species. Here, we analyse a global dataset of avian MHC class I and class II sequences (ca. eleven thousand sequences from over 250 species) to gain insight into the processes that govern macroev...

Determining demographic rates in wild animal populations and understanding why rates vary are important challenges in population ecology and conservation. Whereas reproductive success is reported frequently for many songbird species, there are relatively few corresponding estimates of annual survival for widespread populations of the same migratory...

Ornaments are thought to honestly signal individual quality to potential mates. Individual quality may include the ability to cope with stress through the production of glucocorticoids ( GC s), such as corticosterone ( CORT ), which help to redirect resources from growth or reproduction to survival during an acute stress response. However, elevated...

Gene polymorphisms shared between recently diverged species are thought to be widespread and most commonly reflect introgression from hybridization or retention of ancestral polymorphism through incomplete lineage sorting. Shared genetic diversity resulting from incomplete lineage sorting is usually maintained for a relatively short period of time,...

Determining how migratory animals are spatially connected between breeding and non-breeding periods is essential for predicting the effects of environmental change and for developing optimal conservation strategies. Yet, despite recent advances in tracking technology, we lack comprehensive information on the spatial structure of migratory networks...

The Hamilton-Zuk hypothesis predicts that ornament expression is a signal of the ability of individuals to resist parasite infection. Thus, across a population (i.e., between-individuals) more ornamented individuals should have lower levels of parasitism. Numerous studies have tested this prediction and the results are mixed. One reason for these c...

The Major Histocompatibility Complex (MHC) plays a key role in pathogen recognition as a part of vertebrate adaptive immune system. The great diversity of MHC genes in natural populations is maintained by different forms of balancing selection and its strength should correlate with the diversity of pathogens to which a population is exposed and the...

The negative effects of inbreeding on fitness are serious concerns for populations of endangered species. Reduced fitness has been associated with lower genome-wide heterozygosity and immune gene diversity in the wild; however, it is rare that both types of genetic measures are included in the same study. Thus, it is often unclear whether the varia...

Across taxa, extra-pair mating is widespread among socially monogamous species, but few studies have identified male ornamental traits associated with extra-pair mating success, and even fewer studies have experimentally manipulated male traits to determine if they are related directly to paternity. As a consequence, there is little experimental ev...

Genes of the major histocompatibility complex (MHC) encode receptor molecules that are responsible for recognition of intracellular and extracellular pathogens (class I and class II genes, respectively) in vertebrates. Given the different roles of class I and II MHC genes, one might expect the strength of selection to differ between these two class...

Immune-receptor genes of the adaptive immune system, such as the major histocompatibility complex (MHC), are involved in recognizing specific pathogens and are known to have high rates of adaptive evolution, presumably as a consequence of rapid coevolution between hosts and pathogens. In contrast, many 'mediating' genes of the immune system do not...

Male ornaments are hypothesized to signal the ability of males to produce an effective immune response without extensive oxidative stress and damage to DNA . We examined this hypothesis in male common yellowthroats ( Geothlypis trichas ), which have two ornaments, a black (eumelanin‐based) facial mask and a yellow (carotenoid‐based) bib. In our stu...

Despite benefits of using light-sensitive geolocators to track animal movements and describe patterns of migratory connectivity, concerns have been raised about negative effects of these devices, particularly in small species of aerial insectivore. Geolocators may act as handicaps that increase energetic expenditure, which could explain reported ef...

The bright colors of birds are often attributed to sexual selection on males, but in many species both sexes are colorful and it has been long debated whether sexual selection can also explain this variation. We show that most evolutionary transitions in color have been toward similar plumage in both sexes, and the color of both sexes (for example,...

Male traits that signal health and vigor are used by females to choose better quality mates, but in some cases, the male trait selected by females differs among populations. Multiple male traits can be maintained through female mate choice if both traits are equally honest indicators of male quality, but tests of this prediction are rare. By choosi...

One of the greatest feats of avian migration is the non-stop crossing of extensive areas of inhospitable habitat such as deserts and seas. Differences in spring and autumn migration routes have been reported in species that cross such barriers, and are thought to have evolved in response to seasonal variation in prevailing wind direction. We tested...

In a study of almost 16 000 nest records from seven swallow species across the entire Western Hemisphere, clutch sizes decline with relative laying date in each population, but the slope of this decline grows steeper with increasing distance from the equator. Late-laying birds at all latitudes lay clutches of similar sizes, suggesting that latitudi...

Females often possess ornaments that appear smaller and duller than homologous traits in males. These ornaments may arise as nonfunctional by-products of sexual selection in males and cause negative viability or fecundity selection in females in proportion to the cost of their production and maintenance. Alternatively, female ornaments may function...

Research on sexually selected male traits has intensified over the last two decades and there are now many species of birds for which male traits associated with extra-pair mating success have been identified. Some of the more commonly studied species have been examined in multiple populations; however, there is often little consistency in results...

One of the greatest feats of avian migration is the non-stop crossing of extensive areas of inhospitable habitat such as deserts and seas. Differences in spring and autumn migration routes have been reported in species that cross such barriers, and are thought to have evolved in response to seasonal variation in prevailing wind direction. We tested...

Sexual selection is proposed to be an important driver of diversification in animal systems, yet previous tests of this hypothesis have produced mixed results and the mechanisms involved remain unclear. Here, we use a novel phylogenetic approach to assess the influence of sexual selection on patterns of evolutionary change during 84 recent speciati...

In socially monogamous species, extra-pair paternity may increase the strength of intersexual selection by allowing males with preferred phenotypes to monopolize matings. Several studies have found relationships between male signals and extra-pair mating, but many others fail to explain variation in extra-pair mating success. A greater appreciation...

Determining the distribution of stopover and overwintering areas for migratory animals is essential for understanding population dynamics and building predictive models. Tree Swallows (Tachycineta bicolor) are small songbirds that breed across North America. Data from Doppler weather radar and eBird indicate that Tree Swallow numbers increase throu...

Hamilton and Zuk proposed that females choose mates based on ornaments whose expression is dependent on their genetically based resistance to parasites. The major histocompatibility complex (MHC) plays an important role in pathogen recognition and is a good candidate for testing the relationships between immune genes and both ornament expression an...

The major histocompatibility complex (MHC) plays a central role in innate and adaptive immunity, but relatively little is known about the evolution of the number and arrangement of MHC genes in birds. Insights into the evolution of the MHC in birds can be gained by comparing the genetic architecture of the MHC between closely related species. We us...

Females are thought to gain better-quality genes for their offspring by mating with particular males. Genes of the major histocompatibility complex (MHC) play a critical role in adaptive immunity, and several studies have examined female mate choice in relation to MHC variation. In common yellowthroats, females prefer males that have larger black f...

Many species possess multiple sexual signals that are produced in different modalities. Signals from different modalities may convey different or similar (redundant) information, or be intended for different receivers. We studied sexual selection on two such signals (plumage and song) in the common yellowthroat, Geothlypis trichas. We measured the...

Data from the North American Breeding Bird Survey (BBS) suggest that populations of aerial insectivorous birds are declining, particularly in northeastern regions of the continent, and particularly since the mid-1980s. Species that use nest boxes, such as Tree Swallows (Tachycineta bicolor), may provide researchers with large data sets that better...

In lek mating systems, females visit aggregations of displaying males and appear to have unrestricted opportunity to choose and mate with any male. Behavioral observations of lekking birds indicate that females generally mate once and that only a small percentage of males gain a majority of copulations. However, genetic analyses of paternity have r...

Population bottlenecks may reduce genetic variation and potentially increase the risk of extinction. Here, we present the first study to use historic samples to analyse loss of variation at the major histocompatibility complex (MHC), which plays a central role in vertebrate disease resistance. Balancing selection acts on the MHC and could moderate...

Sex allocation theory predicts that females should bias the sex ratio of their offspring in response to differences in the reproductive value of sons and daughters. For example, paternal traits (ornaments) that are associated with male quality and reproductive success may result in male-biased sex ratios when inheritance of these traits is more ben...

In seasonal environments, vertebrates are generally thought to time their reproduction so offspring are raised during the peak of food abundance. The mismatch hypothesis predicts that reproductive success is maximized when animals synchronize their reproduction with the food supply. Understanding the mechanisms influencing the timing of reproductio...

In biparental species, parental-investment theory generally predicts an inverse relationship between the level of parental care provided by each parent and incomplete compensation by one parent in response to reduced parental care by their partner. The factors that influence the magnitude of this compensation have rarely been examined in birds. For...

Females often mate with several different males, which may promote sperm competition and increase offspring viability. However, the potential benefits of polyandry remain controversial, particularly in birds where recent reviews have suggested that females gain few genetic benefits from extra-pair mating. In tree swallows (Tachycineta bicolor), we...

The major histocompatibility complex (MHC) is characterized by a birth and death model of evolution involving gene duplication, diversification, loss of function, and deletion. As a result, gene number varies across taxa. Birds have between one and 7 confirmed MHC class II B genes, and the greatest diversity appears to occur in passerines. We used...

1. Female preferences for particular male ornaments may shift between populations as a consequence of ecological differences that change the reliability and detectability of the ornament, but few studies have examined how ornaments function in different populations. 2. We examined the signalling function of male plumage ornaments in a warbler, the...

The major histocompatibility complex (Mhc) of domestic chickens has been characterized as small and relatively simple compared with that of mammals. However, there is growing evidence that the Mhc of many bird lineages may be more complex, even within the Order Galliformes. In this study, we measured genetic variation and balancing selection at Mhc...

In many animals, sexual selection has resulted in complex signaling systems in which males advertise aspects of their phenotypic or genetic quality through elaborate ornamentation and display behaviors. Different ornaments might convey different information or be directed at different receivers, but they might also be redundant signals of quality t...

There is mounting evidence in a variety of taxa that females increase offspring quality by mating with multiple males, often resulting in multiple paternity. In birds, however, few studies have explicitly examined the benefits of mating with several different males; instead, the focus has been on whether or not extra-pair mating occurs, and its ada...

Los especímenes de museo son valiosos para estudiar el color del plumaje en las aves, pero el color de las plumas podría perderse a lo largo del tiempo y no reflejar los colores de las aves vivas. Específicamente, se ha sugerido que el color ultravioleta (UV) podría ser más susceptible a degradarse que los colores visibles por los humanos. En este...

Se cree que la abundancia de alimento, el clima y la condición corporal de las hembras influyen sobre el momento de la reproducción y el desempeño reproductivo de las aves. Estudiamos simultáneamente el efecto del clima y de la abundancia de alimento sobre la reproducción de Tachycineta bicolor, al mismo tiempo que redujimos experimentalmente la co...

Cuando el valor reproductivo de los hijos difiere del de las h?as, la selección favorecerá las nidadas sesgadas hacia el sexo que puede brindar mayor adecuación biológica. En las especies en las que la elección de las hembras se basa en la ornamentación de los machos, las hembras que se aparean con machos con muchas ornamentaciones pueden obtener u...

Se espera que los padres varíen el cociente de sexos de sus pichones en relación a beneficios sexo-específicos en la adecuación biológica (fitness). Sin embargo, los beneficios de producir nidadas sesgadas en sexo pueden depender del estado de la hembra. Por ejemplo, madres en buen estado podrían alcanzar mayor fitness si produjeran hijos de alta c...

We studied within-season mate switching in House Wrens (Troglodytes aedon) from 1998 to 2000. Males initiated mate switching, but mate switching was not related to the male's paternity in the first brood, his body condition, or his breeding experience. Males were more likely to switch mates when unmated females were nearby. Males that switched mate...

We studied female responses to experimental intraspecific brood parasitism (IBP), or egg-dumping, in Tree Swallows (Tachycineta bicolor). Unlike other species of swallows, Tree Swallow nests are rarely parasitized by conspecifics. We experimentally parasitized nests of Tree Swallows to investigate how females respond to uncertain maternity. Host fe...

The classification of New World martins (Progne) has a convoluted history because taxonomists have relied on plumage traits that vary continuously across populations. We estimated the phylogeny of Progne by analyzing mitochondrial cytochrome b DNA sequences of 27 individuals of eight of the nine species (10 subspecies) and nuclear β-fibrinogen intr...

Recent advances in portable spectrophotometers have allowed researchers to collect quantitative, objective data on colour. There are few comparisons of the different methods used to summarize and analyse spectrophotometer data, however. Using colour data on over 900 species of birds, we compared three methods of calculating sexual dichromatism usin...

We used controlled aviary experiments to study the role of male ornaments in male-male competition and female choice in the common yellowthroat Geothlypis trichas, a sexually dichromatic warbler. Previous aviary studies in Wisconsin, USA, indicated that males with larger black facial masks were dominant over males with smaller masks and preferred b...

Male ornaments may advertise genetic benefits to females choosing mates. These benefits may come in the form of genes for resistance to parasites and disease. Thus, females that prefer more ornamented males as mates may receive genes for enhanced immune system function for their offspring. The common yellowthroat (Geothlypis trichas) is the only sp...

Bibliography, phylogenies, and subfamily data

In 1950, Rensch first described that in groups of related species, sexual size dimorphism is more pronounced in larger species. This widespread and fundamental allometric relationship is now commonly referred to as 'Rensch's rule'. However, despite numerous recent studies, we still do not have a general explanation for this allometry. Here we repor...

Maternal allocation of resources to eggs and nestlings can potentially have a profound influence on offspring phenotype and fitness. However, it is often unclear how much of the variation in offspring quality is due to maternal or environmental effects. We examined the influence of maternal and environmental effects on egg mass and nestling quality...

Maternal allocation of resources to eggs and nestlings can potentially have a profound influence on offspring phenotype and fitness. However, it is often unclear how much of the variation in offspring quality is due to maternal or environmental effects. We examined the influence of maternal and environmental effects on egg mass and nestling quality...

Male ornaments may be signals of direct or indirect benefits to females that mate with those males. One important direct benefit to females is the level of male parental assistance they receive when provisioning young. Three main hypotheses attempt to explain the relationship between male ornament size and parental care. The good parent hypothesis...

Costs of searching for a mate are an important component of models of sexual selection, yet they have rarely been examined in wild populations of vertebrates. In this paper, we report an experiment in which we handicapped female tree swallows by clipping some flight feathers. This manipulation increased the costs of flight and searching for extra-p...

When the reproductive value of sons differs from that of daughters, selection will favor broods biased toward the sex that can provide greater fitness benefits. In species where female choice is based on male ornamentation, females mated to highly ornamented males may experience a reproductive advantage by skewing the brood sex ratio toward sons. I...

Extra-pair mating is widespread in birds, but its adaptive function remains unclear. It is often suggested that females obtain superior genes for their offspring as a consequence of extra-pair mating, but the evidence is limited. In this study, we examined the hypothesis that extra-pair mating provides females with offspring that have superior immu...

Despite numerous studies of extrapair paternity in birds, little is known about the behaviours that males and females use to seek (or avoid) extrapair copulations. We used radiotelemetry to examine the extrater- ritorial movements of both male and female common yellowthroats, Geothlypis trichas, in relation to male ornaments, particularly the black...

Models of sexual selection assume that female mating preferences are heritable and, thus, repeatable for individual females across multiple mating episodes. Previous studies of the repeatability of female preference have examined individuals in captivity and focused presumably on social mate choice. However, extra-pair mating is widespread and can...

Food abundance, weather, and female body condition are believed to influence the timing of breeding and reproductive performance of birds. We simultaneously studied the effects of weather and food abundance on reproduction in Tree Swallows (Tachycineta bicolor) while experimentally reducing female condition and foraging efficiency by clipping some...