Biology subjects

Germain, R. R.

Publications and source records attributed to Germain, R. R..

4 recordsLinked to original sources

bioRxiv2018

Individual repeatability and heritability of divorce in a wild population

Understanding micro-evolutionary responses of mating systems to contemporary selection requires estimating sex-specific additive genetic variances and cross-sex genetic covariances in key reproductive strategy traits. One key trait comprises the occurrence of divorce versus mate-fidelity across sequential reproductive attempts. If divorce represents an evolving behavioural strategy it must have non-zero individual repeatability and heritability, but quantitative estimates from wild populations are scarce. We used 39 years of individual breeding records and pedigree data from free-living song sparrows (Melospiza melodia) to quantify sex-specific permanent individual and additive genetic variances, and hence estimate repeatability and heritability, in liability for divorce. We estimated moderate repeatability in females, but little repeatability in males. Estimates of additive genetic variance were small in both sexes, and the cross-sex genetic covariance was close to zero. However, the total heritability was likely non-zero but small, indicating low potential for micro-evolutionary response to selection. Rapid micro-evolution of divorce rate therefore appears unlikely, even if there were substantial fitness benefits of divorce and resulting selection.

evolutionary biology↗

bioRxiv2017

Demographic consequences of invasion by a native, controphic competitor to an insular bird population

Species invasions and range shifts can lead to novel competitive interactions between historically resident and colonizing species, but the demographic consequences of such interactions remain controversial. We present results from field experiments and 45 yrs of demographic monitoring to test the hypothesis that the colonization of Mandarte Is., BC, Canada, by fox sparrows (Passerella iliaca) caused the long-term decline of the song sparrow (Melospiza melodia) population resident there. Several lines of evidence indicate that competition with fox sparrows for winter food reduced over-winter survival in juvenile song sparrows, enforcing population decline despite an increase in annual reproductive rate in song sparrows over the same period. In contrast, we found no evidence of interspecific competition for resources during the breeding season. Our results indicate that in the absence of a sufficient ecological or evolutionary shift in niche dimension, range expansions by dominant competitors have the potential to cause the extirpation of historically resident species when competitive interactions between them are strong and resources not equitably partitioned.

ecology↗

bioRxiv2017

The consequences of polyandry for sibship structures, distributions of relationships and relatedness, and potential for inbreeding in a wild population

The evolutionary benefits of simultaneous polyandry (female multiple mating within a single reproductive event) remain elusive. One potential benefit could arise if polyandry alters sibship structures and consequent relationships and relatedness among females descendants, and thereby intrinsically reduces future inbreeding risk (the indirect inbreeding avoidance hypothesis). However such effects have not been quantified in naturally complex reproductive systems that also encompass iteroparity, overlapping generations, sequential polyandry, and polygyny. We used long-term social and genetic pedigree data from song sparrows (Melospiza melodia) to quantify cross-generational consequences of simultaneous polyandry for offspring sibship structures and distributions of relationships and relatedness among possible mates. Simultaneous polyandry decreased full-sibships and increased half-sibships on average, but such effects varied among females and were smaller than would occur in the absence of sequential polyandry or polygyny. Further, while simultaneous polyandry decreased the overall frequencies of possible matings among adult full-sibs, it increased the frequencies of possible matings among adult half-sibs and more distant relatives. These results imply that the intrinsic consequences of simultaneous polyandry for inbreeding risk could cause weak indirect selection on polyandry, but the magnitude and direction of such effects will depend on complex interactions with other mating system components and the form of inbreeding depression.

evolutionary biology↗

bioRxiv2017

Evolution Of Pre-Copulatory And Post-Copulatory Strategies Of Inbreeding Avoidance And Associated Polyandry

Inbreeding depression is widely hypothesised to drive adaptive evolution of pre-copulatory and post-copulatory mechanisms of inbreeding avoidance, which in turn are hypothesised to affect evolution of polyandry (i.e., female multiple mating). However, surprisingly little theory or modelling critically examines selection for pre-copulatory or post-copulatory inbreeding avoidance, or both strategies, given evolutionary constraints and direct costs, or examines how evolution of inbreeding avoidance strategies might feed back to affect evolution of polyandry. Selection for post-copulatory inbreeding avoidance, but not for pre-copulatory inbreeding avoidance, requires polyandry, while interactions between pre-copulatory and post-copulatory inbreeding avoidance might cause functional redundancy (i.e., degeneracy) potentially generating complex evolutionary dynamics among inbreeding strategies and polyandry. We used individual-based modelling to quantify evolution of interacting pre-copulatory and post-copulatory inbreeding avoidance and associated polyandry given strong inbreeding depression and different evolutionary constraints and direct costs. We found that evolution of post-copulatory inbreeding avoidance increased selection for initially rare polyandry, and that evolution of a costly inbreeding avoidance strategy became negligible over time given a lower cost alternative strategy. Further, fixed pre-copulatory inbreeding avoidance often completely precluded evolution of polyandry and hence post-copulatory inbreeding avoidance, but fixed post-copulatory inbreeding avoidance did not preclude evolution of pre-copulatory inbreeding avoidance. Evolution of inbreeding avoidance phenotypes and associated polyandry are therefore affected by evolutionary feedbacks and degeneracy. All else being equal, evolution of pre-copulatory inbreeding avoidance and resulting low polyandry is more likely when post-copulatory inbreeding avoidance is precluded or costly, and evolution of post-copulatory inbreeding avoidance greatly facilitates evolution of costly polyandry.

evolutionary biology↗