Biology subjects

Courtin, J.

Publications and source records attributed to Courtin, J..

4 recordsLinked to original sources

bioRxiv2025

Dynamic connectivities of plant metacommunities at a millennial time-scale: the Beringia testbed

Ecological connectivity shapes ecosystem responses to climate change and is thought to underpin stability, yet its millennial-scale dynamics remain poorly resolved. We asked how spatial and temporal connectivity of plant metacommunities changed over the last 40 ka and which processes drove it. We analysed and compiled plant sedimentary DNA from 20 lake cores across Beringia (Siberia, Alaska) to investigate community dynamics and, for a high-resolution subset, applied beta- and zeta-diversity to track connectivity. Vegetation changed coherently across the glacial-Holocene transition, with trait shifts mirroring functional composition. Connectivity peaked during the late MIS3 and Last Glacial Maximum--likely aided by the Bering Land Bridge, mass effects and facilitation--collapsed during the Deglacial with rapid turnover, and rebounded in the Holocene as shrub and boreal communities expanded. Temporal zeta within sites exceeded spatial zeta, indicating strong local persistence and resilience. Tundra sites uninvaded by forest maintained continuous species pools. Overall, these patterns underscore the value of a metacommunity perspective for assessing millennial-scale connectivity changes.

ecology↗

bioRxiv2025

Functional and structural profiling of circulation via genetically encoded modular fluorescent probes.

Sustained labeling of fluids is crucial for their investigation in animal models. Here, we introduce a mouse line (Alb-mSc-ST), where blood and interstitial fluid are labeled with the red fluorescent protein mScarlet and SpyTag. The SpyTag-SpyCatcher technology is exploited to monitor circulating fluid properties by biosensors or detect blood-brain barrier disruption. This approach represents a valuable tool for studying vascular structure, permeability and microenvironment in body organs in vivo.

neuroscience↗

bioRxiv2025

A common neuronal basis for Pavlovian and instrumental learning in amygdala circuits

Reward-predictive Pavlovian cues can selectively invigorate instrumental behaviors. Accumulating evidence pinpoints the basolateral amygdala (BLA) as a key brain structure to assign outcome-specific motivational significance to Pavlovian cues or Instrumental actions. However, whether neuronal representations of Pavlovian and Instrumental learnings are processed in different BLA circuits and how the resulting memories interact is unknown. Here, we used calcium imaging and optogenetic manipulation of the BLA neurons in mice that acquired and expressed Pavlovian and Instrumental behaviors in a multi-phase behavioral task called specific Pavlovian to Instrumental Transfer (sPIT). We first confirmed that Pavlovian cues selectively invigorate instrumental actions and showed that this effect, referred as the sPIT effect, depends on BLA activity. Then, by tracking the activity of single BLA neurons across days, we found that BLA neurons integrate common reward-anticipation information relevant for Pavlovian and instrumental learning. Interestingly, this reward-anticipation information re-emerged during subsequent memory transfer and covaried with sPIT effect. These findings reveal that the BLA encodes an outcome-specific motivational state that generalizes across Pavlovian and instrumental behaviors to promote and guide reward-seeking behavior.

neuroscience↗

bioRxiv2020

Plant sedimentary ancient DNA from Far East Russia covering the last 28 ka reveals different assembly rules in cold and warm climates

Woody plants are expanding into the Arctic under a warming climate. The related impact on plant diversity is not well understood because we have only limited knowledge about plant assembly rules and because of a lack of time-series of plant diversity. Here, we applied sedimentary ancient DNA metabarcoding using the plant-specific g and h primers of the trnL gene to a sediment record from Lake Ilirney (central Chukotka Far Eastern Russia) covering the last 28 thousand years. Our results show that forb-dominated steppe-tundra and Saliceae-rich dwarf-shrub tundra communities dominated during the cold climate before 14 ka, while deciduous erect-shrub tundra was abundant during the warm period between 14 and 0 ka. Larix invasion during the late Holocene substantially lagged behind the period of densest vegetation and likely warmest period between 10 and 6 ka. Overall, we discovered the highest richness during 28-23 ka and a second richness peak during 13-10 ka: both periods are characterised by low shrub abundance. The richest communities during the cold pre-14 ka period were phylogenetically clustered, which probably originates from environmental filtering along with niche differentiation under limited resources. In contrast, the richest post-14 ka community was phylogenetically overdispersed, likely originating from an erratic recruitment process in the course of warming. Despite differences in timescale, some of our evidence can be relevant to arctic plant diversity changes. By analogy to the past, we expect a lagged response of tree invasion. In the long-term, ongoing expansion of deciduous shrubs will eventually result in a phylogenetically more diverse community but will also cause reduced plant taxonomic richness; however, richness may overshoot in the short-term.

ecology↗