Biology subjects

Eberhart-Phillips, L. J.

Publications and source records attributed to Eberhart-Phillips, L. J..

5 recordsLinked to original sources

bioRxiv2023

Dispersal in Kentish plovers (Charadrius alexandrinus): Adult females perform furthest movements

Dispersal is an important behavioural process that plays a significant role in, among others, speciation, population viability, and individual fitness. Despite progress in avian dispersal research, there are still many knowledge gaps. For example, it is of interest to study how movement propensity (i.e., nomadic vs. philopatric) relates to age- and/or sex-specific patterns of dispersal. Here, we investigated the role of sex and life-stage on natal (i.e., displacement between birth site and first breeding site) and breeding dispersal (i.e., displacement between sequential breeding sites) in the Kentish plover (Charadrius alexandrinus). This small and inconspicuous wader is characterised by flexible mating behaviour that includes monogamy, and serial polygyandry. Using a continent-wide dataset of ringing and re-encounter data throughout the species range in Europe, we found that adult females generally dispersed further than adult males between seasons, but we detected no sex-difference in natal dispersal distances and no general difference between natal and breeding dispersal distances. Furthermore, females were the main group exhibiting long-distance breeding dispersal, which we defined as breeding movements greater than [≥]108 km (i.e., upper 10% percentile of our dataset). Our work detected two females breeding in the Mediterranean before dispersing and breeding at the North Sea in the subsequent year, distances of 1,290 and 1,704 km, respectively - this represents the longest known breeding dispersal within the genus Charadrius. The long-distance dispersal records we identified are consistent with low genetic differentiation between mainland populations shown in previous work. The dispersive nature of the Kentish plover is likely attributed to its breeding behaviour: polyandrous females exhibit extensive mate searching and habitat prospecting. We recommend that the dispersal traits of Kentish plover be incorporated into the species conservation and management planning to more accurately inform models of population connectivity and metapopulation dynamics.

animal behavior and cognition↗

bioRxiv2020

Polyandry and senescence shape egg size variation in a precocial bird.

Gamete size variation between the sexes is central to the concept of sex roles, however, to what extent gamete size variation within the sexes relates to sex role variation remains unclear. Comparative and theoretical studies suggest that, when clutch size is invariable, polyandry is linked to a reduction of egg size, while increased female-female competition for mates favors early breeding when females cannot monopolize multiple males. To understand whether and how breeding phenology, egg size, and mating behavior are related at the individual level, we studied the reproductive histories of 424 snowy plover females observed in the wild over a 15-year period. Egg size, but not polyandry, were highly repeatable for individual females. Consistent with theoretical predictions, we found that polyandrous females were the earliest breeders and that early clutches contained smaller eggs than clutches initiated later. Neither egg size nor mating behavior showed clear signs of an age-related deterioration, on the contrary, prior experience acquired either through age or local recruitment enabled females to nest early. Taken together, these results suggest that gamete size variation is not linked to mating behavior at the individual level, and, consequently, the adaptive potential of such variation appears to be limited. Teaser TextComparative avian analyses have linked female polyandry and sex-role reversal to the production of smaller eggs: the notion being that smaller eggs allow polyandrous females to lay multiple sequential clutches quickly. Our research, however, has found that the notion is more complex at the individual level. We found that females who started breeding early in the season were more likely to be polyandrous and produce smaller eggs. Experience was also found to give older and locally-raised females a competitive advantage over younger and inexperienced females vying for early breeding opportunities. Despite this, we found limited evidence that egg size reduction gives a competitive advantage in the scramble for mates. Instead, seasonal variations in egg size can likely be attributed to other factors, such as the survival of early-hatching chicks, resource limitations during egg production, and individual differences. We found that senescence had little impact on egg size or mating behavior. Future research should also examine how seasonality, age, and mating behavior impact the reproductive fitness of males, who provide more parental care than females in many sex role reversed systems. By studying these effects in concert, we can gain a deeper understanding of sex roles in natural populations.

evolutionary biology↗

bioRxiv2019

CeutaOPEN: Individual-based field observations of breeding snowy plovers Charadrius nivosus

Shorebirds (partim members of order Charadriiformes) have a global distribution and exhibit remarkable variation in ecological and behavioural traits that are pertinent to many core questions in the fields of evolutionary ecology and conservation biology. Shorebirds are also relatively convenient to study in the wild as they are ground nesting and often occupy open habitats that are tractable to monitor. Here we present a database documenting the reproductive ecology of 1,600 individually marked snowy plovers (Charadrius nivosus) monitored between 2006 and 2016 at Bahia de Ceuta (23{degrees}54 N, 106{degrees}57 W) - an important breeding site in north-western Mexico. The database encompasses various morphological, behavioural, and fitness-related traits of males and females along with spatial and temporal population dynamics. This open resource will serve as an important data repository for addressing overarching questions in avian ecology and wetland conservation during an era of big data and global collaborative science.

ecology↗

bioRxiv2017

Demographic causes of adult sex ratio variation and their consequences for parental cooperation

The adult sex ratio (ASR) is a fundamental concept in population biology, sexual selection, and social evolution. However, it remains unclear which demographic processes generate ASR variation and how biases in ASR in turn affect social behaviour. Here, we evaluate the demographic mechanisms shaping ASR and their consequences for parental cooperation using detailed survival, fecundity, and behavioural data on 6,119 individuals from six wild shorebird populations exhibiting flexible parental strategies. We show that these closely related populations express strikingly different ASRs, despite having similar ecologies and life histories, and that ASR variation is largely driven by sex differences in the apparent survival of juveniles. Furthermore, families in populations with biased ASRs were predominantly tended by a single parent, suggesting that parental cooperation breaks down with unbalanced sex ratios. Taken together, our results indicate that sex biases emerging during early life have profound consequences for social behaviour.

ecology↗

bioRxiv2017

Adult sex ratio bias in snowy plovers is driven by sex-specific early survival: implications for mating systems and population growth

Adult sex ratio (ASR) is a central concept in population biology and a key factor in sexual selection, yet why do most demographic models ignore sex-biases? Vital rates often vary between the sexes and across life history, but their relative contributions to ASR variation remain poorly understood--an essential step to evaluate sex ratio theories in the wild and inform conservation. Here we combine structured two-sex population models with individual-based mark-recapture data from an intensively monitored polygamous population of snowy plovers. We show that a strongly male-biased ASR is primarily driven by sex-specific survival of juveniles, rather than adults or dependent offspring. This provides empirical support for theories of unbiased sex allocation when sex-differences in survival arise after the period of parental investment. Importantly, a conventional model ignoring sex-biases significantly overestimated population viability. We suggest that sex-specific population models are essential to understand the population dynamics of sexual organisms: reproduction and population growth is most sensitive to perturbations in survival of the limiting sex. Overall, our study suggests that sex-biased early survival may contribute towards mating system evolution and population persistence, with implications for both sexual selection theory and biodiversity conservation.\n\nSIGNIFICANCE STATEMENTSex biases are widespread in nature and represent a fundamental component of sexual selection and population biology--but at which point in life history do these biases emerge? Here we report a detailed individual-based demographic analysis of an intensively studied wild bird population to evaluate the origins of sex biases and their consequences on mating strategies and population dynamics. We document a strongly male-biased adult sex ratio, which is consistent with behavioral observations of female-biased polygamy. Notably, sex-biased juvenile, rather than adult survival, contributed most to the adult sex ratio. Sex-biases also strongly influenced population viability, which was significantly overestimated when sex ratio and mating system were ignored. Our study therefore has implications for both sexual selection theory and biodiversity conservation.

ecology↗