Ryan Germain
Department of Ecoscience
Aarhus University
RESEARCH PROJECTS
Overview
My research integrates advances from several fields to understand of how changing environmental conditions affect the life-history dynamics and genetic diversity of wild bird populations. Determining the sources and consequences of such effects is crucial to our understanding of how wild populations will respond to land-use and climate change, and will play a pivotal role in long-term conservation planning. To meet these objectives, I integrate observations from long-term field studies with diverse analytical methods (including remote sensing, spatial statistics, quantitative genetics, comparative genomics, and simulation-based modelling) to determine the sources of life-history variation within wild populations and predict evolutionary responses to selection given environmental change.
Avian demography under one million years of climate change
My current research utilizes full-genome sequence data from hundreds of bird species to evaluate demographic change in the face of climate change over the past million years. This project, funded by the Danish Research Council, involves a consortium of researchers from universities, museums, and genomic centers around the world. Findings from this work will inform our understanding of how biodiversity will respond to current and ongoing environmental challenges, allowing us to make more realistic demographic predictions in our goal to stem current global biodiversity loss.
Illustration by Jon Fjeldså
The relative effects of genetic and individual variation versus habitat quality on fitness
Much of my past and ongoing research focuses on disentangling the effects of habitat quality versus genetic and among-individual variation on measures of fitness. To address this topic, I primarily rely on the long-term study population of song sparrows (Melospiza melodia) on Mandarte Island (British Columbia, Canada), which has been monitored continuously since 1975.
Each year, every nesting attempt on this small island is located and all offspring are banded and followed until independent from parental care. This effort over the past four decades allows for highly detailed estimates of both habitat preference and habitat quality. Because all individuals in this resident population are monitored over their lifetime, we are able to accurately measure variation in individual fitness and use the detailed pedigree to determine the heritability of fitness traits.
My co-authors and I have found that certain habitats are highly preferred by females as nest-sites and offer specific reproductive benefits during the early breeding season. Despite this, the annual reproductive output in a given site is primarily determined by the quality of individual female occupants and not the environmental attributes of the site itself. Further, we have found that breeding date (a trait strongly correlated with annual reproductive success) is influenced by both direct (female) and indirect (male) additive genetic effects, which can each exceed phenotypic variance stemming from fine-scale habitat-based variation.
Follow-up projects from this work in other systems have aimed to further investigate the role of habitat quality on different fitness components in a variety of bird species facing different ecological and social-environmental conditions. By employing pedigree-based analyses and detailed field observations of environmental variation, my work provides key information on how to accurately quantify the role of habitat as a driver of selection in wild populations.
The effects of polyandry on population relatedness structure and inbreeding
My postdoctoral research at the University of Aberdeen focused on estimating the effects of female multiple mating (‘polyandry’) on the potential for inbreeding in wild populations. The widespread occurrence of polyandry in nature suggests some intrinsic benefit to this behaviour, despite its obvious costs. However, we previously had no empirical basis on which to consider how the evolutionary dynamics of mating systems could be influenced by the effects of polyandry on population-wide sibship and relationship structures and the resulting potential for inbreeding.
To address this knowledge gap, I used comprehensive pedigree data (Figure) from free-living socially-monogamous song sparrows to quantify the consequences of extra-pair reproduction (and hence underlying polyandry) for sibship structures and the distributions of relationships and relatedness between possible mates. I demonstrated that polyandry shifts the distribution of relatedness among females’ descendants and their potential mates, thereby reducing the potential for close inbreeding in future generations. These results imply that the consequences of multiple mating for inbreeding risk could cause weak indirect selection for polyandry, and illustrate the potential feedbacks between mating strategy, population relatedness structure, and inbreeding.
As a follow up to this, my collaborators and I are currently exploring the consequences of ‘sequential polyandry’ due to mate-death or divorce on population relatedness structure, as well as the genetic basis of divorce in wild populations.
Developmental-based variation in sexual signals
Many animals use conspicuous visual and vocal displays in both courtship and territorial interactions, as such displays often act as signals of individual genetic and/or phenotypic quality. However, we currently have a limited understanding of how the information conveyed through such signals changes when displays themselves develop or change over an individual’s lifetime.
My work on this topic has so far focused on the delayed maturation of sexual signals in the American redstart (Setophaga ruticella), a migratory warbler with dramatic age-based differences in male plumage colouration. I investigated variation in the degree of adult-like plumage expressed by juvenile males on both the breeding grounds (Queen’s University Biological Station, Ontario, Canada) and wintering grounds (Font Hill Nature Preserve, Westmoreland Parish, Jamaica), and found that a more adult-like appearance may signal a juvenile male’s competitive ability for high-quality resources during both stages of the annual cycle.
My collaborators and I have also uncovered developmental differences in the mate-attraction song of male redstarts, indicating that males of this species exhibit delayed song maturation as well as delayed plumage maturation. We provide evidence of the potential reproductive benefits of expressing more adult-like songs, highlighting the importance of variation in delayed signals for individual life-history.
My interests in animal signalling have also resulted in exciting collaborative work on phenotypic divergence in plumage, song, and morphology across sister-pairs of migratory birds, the genetic basis to differences in plumage colouration among hybridizing sub-species, and previously undocumented sexual dichromatisim in a species of freshwater turtle.
Natural history and miscellany
I enjoy conducting research on a variety of topics, and I’ve formed great collaborations with people who feel the same way. This has led to a number of fun studies on diverse subjects such as predation of passerines living in gull colonies, the effects of highways as barriers to mammal movement, and how ecologists can effectively target their research audience.
Current projects mostly revolve around evidence-based conservation area design, including applied methods to help identify high-priority land parcels.