Biology subjects

Bocquet, C.

Publications and source records attributed to Bocquet, C..

5 recordsLinked to original sources

bioRxiv2025

Early-life adversity modulates growth trajectories and red blood cell mitochondrial metabolism in king penguin chicks

In many avian species, variation in breeding phenology is known to affect reproductive success. In king penguins, the breeding cycle lasts more than a year, and the start of egg-laying extends over 3 months, with early-breeders laying eggs around December and late-breeders around February. Consequently, late-born chicks have less time to grow and build up their energy reserves before the Austral winter. It is however not known whether late-born chicks display alternative physiological strategies to catch up before winter. Variation in metabolic rate is one important pathway driving differences in growth patterns, as it is directly involved both in energy allocation processes and fitness. The conversion of resources into energy occurs in mitochondria, and the efficiency of this conversion is likely to play a fundamental role in explaining individual heterogeneity in growth and survival. The purposes of this study were to investigate the differences in red blood cell mitochondrial metabolism between early- and late-born king penguin chicks and to assess whether morphometric phenotypes could be explained by differences in mitochondrial metabolism. Late-chicks expressed higher mitochondrial metabolism compared to early-chicks at 100 days post-hatching, probably linked to the stress related to winter environmental conditions and a decrease in parental feeding rates. We did not find a clear association between chick mitochondrial metabolism and growth patterns, suggesting that mostly environmental conditions contributed in explaining different metabolic phenotypes. As king penguin populations in Crozet may face changing breeding conditions (changes in feeding area and foraging trips duration) in relation to global changes, studying the physiological traits and adaptations underlying the chick growth and survival may help understanding the response of king penguins facing challenging conditions.

physiology↗

bioRxiv2025

Urbanisation and habitat fragmentation favour thermophilic and monogynous ant species

Environmental changes such as urbanisation and related habitat loss and fragmentation profoundly impact ecological communities by altering habitats, resources, and microclimates. Yet, the impacts of the resulting environmental conditions on metacommunity dynamics, ranging from species sorting to mass effects, remain a subject of debate. Ants, with diverse life histories and strong ecological effects, are ideal model species to study these pressures. We investigated the response of ant communities, including taxonomic and functional diversity, to urbanisation and habitat fragmentation in the Paris region, comparing wooded areas in 25 urban parks vs. 24 rural forests outside the city. We found a clear difference in species composition between urban and rural environments, with a higher prevalence of thermophilic species and a tendency for monogyny in the city. Forest communities were homogeneous across the size levels we studied, while park communities differed noticeably depending on park size, with larger parks harbouring more species. Our findings suggest that urbanisation selects specific ant traits and favours more thermophilic species, thereby increasing the mean thermal preference of urban communities. These selective effects influence which species can colonise and survive in different patches, shaping metacommunity structure and potentially affecting the resilience of ant communities under climate change.

ecology↗

bioRxiv2024

Mind the polar sun: Solar radiations trigger frequent heat stress in breeding king penguins, despite relatively cool air temperatures.

Polar and sub-polar animals evolved to thrive in cold climates and may thus be particularly sensitive to rising temperatures associated with climate change. Penguins may be especially vulnerable, due to their dual habitat, alternating between foraging in cold waters and breeding/moulting on an increasingly warm land. Here, we characterized heat stress occurrence in breeding king penguins through behavioural observations (e.g. panting occurrence) and body temperature measurements. We observed that behavioural signs of heat stress are frequent in king penguins breeding in the sub-Antarctic region (> 20% of observations at mid-day), and that subcutaneous temperatures increase under high heat load, especially in penguins observed panting. Subcutaneous and core body temperatures were moderately correlated and both increased with heat load. Yet, their responses were not parallel since core body temperature is markedly less sensitive to heat load than subcutaneous temperature. Air temperature alone was a poor predictor of heat stress occurrence, whereas the combination of high solar radiation, low wind speed and high air temperatures provided the strongest predictive power. Finally, reproductive failures were more likely to occur on warmer days, suggesting that heat stress may have significant sublethal effects on adults that could ultimately affect population dynamics. O_FIG O_LINKSMALLFIG WIDTH=150 HEIGHT=200 SRC="FIGDIR/small/611977v3_ufig1.gif" ALT="Figure 1"> View larger version (95K): org.highwire.dtl.DTLVardef@26db91org.highwire.dtl.DTLVardef@119461dorg.highwire.dtl.DTLVardef@4a1d8forg.highwire.dtl.DTLVardef@1da9d96_HPS_FORMAT_FIGEXP M_FIG C_FIG

evolutionary biology↗

bioRxiv2023

Group or solitary dispersal: worker presence and number favour the success of colony foundation in ants

Dispersal strategies are highly variable. Any strategy is associated to costs and benefits, and understanding which factors favour or disfavour a strategy is a key issue in ecology and evolution. Ants exhibit different dispersal and colony foundation strategies. Some species have winged queens that disperse solitarily and far by flight, and that found new colonies alone. Others have apterous queens that disperse with workers over short walking distances, and found new colonies as a group (colony fission). The putative benefits conferred by workers have been little studied and quantified, because comparing the costs and benefits of solitary vs. group dispersal and foundation is difficult when comparing different species. We did this using the ant Myrmecina graminicola, one of the few species that use both strategies. Young queens were mated and allowed to found new colonies in the laboratory, with either zero, two or four workers. We monitored the survival and growth of foundations over one year. The presence of workers increased both survival and growth, with more workers yielding higher growth. These results show the benefit of dispersing and founding in a group. The presence of few workers (as little as two workers) was sufficient to provide benefits, suggesting group foundation does not require a dramatic decrease in the number of propagules produced in M. graminicola. Our results support the hypothesis that the two strategies coexist along a competition-colonization trade-off, where solitary foundation offers a colonization advantage while group foundation has a competitive advantage.

ecology↗

bioRxiv2023

Habitat fragmentation selects for low dispersal in an ant species

Increased habitat fragmentation is one of the major global changes affecting biodiversity. It is characterised by a decrease in habitat availability and by an increase in the isolation of suitable habitat patches. The dispersal capacities of species may evolve in response to increased habitat fragmentation. Spatial heterogeneities and/or costs of dispersal, which are directly linked to habitat fragmentation, tend to select for lower dispersal abilities. We studied the effects of habitat fragmentation on dispersal using an ant species that exhibits a marked dispersal polymorphism. Myrmecina graminicola produces winged queens dispersing by flight over long distances, or apterous queens dispersing on foot over short distances. We sampled queens in 24 forests around Paris and 25 parks within Paris, representing varied levels of habitat fragmentation and habitat size. We identified the queen morphotypes in each environment and used it as a proxy of dispersal. Winged queens predominated in both environments. However, apterous queens were comparatively more common in parks than in forests, suggesting that high fragmentation counterselects dispersal in this species. We argue that this is because dispersing within urban environments is very costly and discuss the factors favouring each queen morph or resulting in their co-occurrence (maintenance of polymorphism).

evolutionary biology↗