Biology subjects

Küpper, C.

Publications and source records attributed to Küpper, C..

6 recordsLinked to original sources

bioRxiv2025

Sex differences in development alter the fledgling sex ratio in a lekking bird with strong sexual size dimorphism

Sex ratio variation is of fundamental importance for population ecology, and the evolution of sex roles and life-histories. Yet, the ecological mechanisms underlying such variation remain often unknown. Using a multiyear dataset from captive and wild precocial Ruffs Calidris pugnax, we show that poorer survival and later fledging of males relative to females result in a female biased sex ratio of the fledgling population. Both sex-specific survival and maturation time contributed equally to an increasing sex ratio bias from hatching to fledging in this sexually dimorphic bird. On average, juvenile females fledged three days earlier than males due to expedited wing development, despite the higher absolute rate of wing growth in males. We argue that sex differences in growth, maturation, and offspring survival are likely the result of strong pre-sexual selection on males to achieve dominance and may help to enforce the Darwinian sex roles observed in this species.

ecology↗

bioRxiv2023

Sperm traits of the three genetic morphs in the ruff sandpiper

BackgroundThe ruff sandpiper Calidris pugnax is a Palearctic lekking shorebird with three genetic morphs determined by an autosomal inversion. Male morphs differ strikingly in body size, ornaments, endocrinology and mating behavior. Aggressive Independents represent the ancestral haplotype, while female-mimicking Faeders and semi-cooperative Satellites are the inverted haplotypes. Because one inversion breakpoint is homozygous lethal, the inverted haplotypes cannot recombine and are expected to accumulate deleterious mutations. The inversion regions also harbor genes involved in spermatogenesis. However, it remains unknown whether the genetic differences between the morphs also translate into differences in sperm traits. Here, we use a captive-bred population of ruffs to compare sperm swimming speed and morphology among the morphs. ResultsRuff sperm morphologically resembled those of passerines, but moved differently, vibrating from side to side while slowly moving forward, rather than rotating while moving forward. Faeder sperm moved the slowest, which is consistent with the prediction of genetic deterioration over time. However, against expectation, sperm of Independents did not seem to be of the highest quality, i.e., their sperm were not the fastest nor the least variable, and they had sperm with the shortest tail and midpiece. Although the midpiece contains the energy-producing mitochondria, sperm midpiece length was not associated with sperm swimming speed. Instead, two of three velocity metrics weakly positively correlated with head length (absolute and relative). ConclusionsThe three genetically determined ruff morphs showed subtle differences in swimming speed and in the length of some sperm components. However, the between-morph differences in sperm swimming speed were not linked to the differences in morphology. We conclude that there is at best limited evidence for lower-quality sperm in the morphs that carry the inversion, and suggest that the potential for the evolution of morph-specific sperm adaptations may be limited in this system. Lay SummaryThe ruff sandpiper is a shorebird that exhibits three genetically distinct types of males, which differ markedly in body size, ornaments, hormones, and mating behavior. Aggressive Independents represent the type that evolved first. Semi-cooperative Satellites and female-mimicking Faeders evolved later through a specific type of genetic rearrangement called an inversion, in which a segment of a chromosome reversed in orientation. Due to the nature of this inversion, Satellite and Faeder chromosomes are expected to deteriorate over time. However, it remains unclear whether the genetic differences between these morphs, which affect physiological and behavioral traits, also translate into differences in sperm traits. We used a captive population of ruffs to compare sperm swimming speed and length measurements between the three types of males. Faeder sperm was the slowest, which is consistent with expectations based on genetic deterioration over time. However, against our expectations, the sperm of Independents does not appear to have better performance characteristics. Although the midpiece of a sperm is responsible for energy production, the length of the midpiece did not relate to sperm swimming speed.

evolutionary biology↗

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↗

bioRxiv2020

Fluffy feathers: how neoptile feathers contribute to camouflage in precocial chicks

Camouflage is a widespread strategy to increase survival. The plumage of precocial chicks often contains elements of disruptive colouration and background matching to enhance concealment. Chick plumage also features fringed feathers as appendages that may contribute to camouflage. Here, we examine whether and how neoptile feathers conceal the outline of chicks. We first conducted a digital experiment to test two potential mechanisms for outline diffusion through appendages: 1) edge intensity reduction and 2) luminance transition. Local Edge Intensity Analysis (LEIA) showed that appendages decreased edge intensity and a mean luminance comparison revealed that the appendages created an intermediate transition zone to conceal the objects outline. The outline was most diffused through an intermediate number of interspersed thin appendages. Increased appendage thickness resulted in fewer appendages improving camouflage, whereas increased transparency required more appendages for best concealment. For edge intensity, the outline diffusion was strongest for a vision system with low spatial acuity, which is characteristic of many mammalian predators. We then analysed photographs of young snowy plover (Charadrius nivosus) chicks to examine whether neoptile feathers increase outline concealment in a natural setting. Consistent with better camouflage, the outline of digitally cropped chicks with protruding feathers showed lower edge intensities than the outline of chicks cropped without those feathers. However, the observed mean luminance changes were not consistent with better concealment. Taken together, our results suggest that thin skin appendages such as neoptile feathers improve camouflage. As skin appendages are widespread, this mechanism may apply to a large variety of organisms.

ecology↗

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↗