Biology subjects

Riva, F.

Publications and source records attributed to Riva, F..

11 recordsLinked to original sources

bioRxiv2026

Small habitat patches can be the largest contributors to urban biodiversity across taxonomic groups

AimAs cities densify and expand, the careful planning and design of green spaces are essential for supporting urban biodiversity. Here, we evaluate the relative contribution of habitat patches of varying size, quality, and connectivity to urban biodiversity and assess environmental factors driving differences in species richness and community composition. LocationZurich, Switzerland. Time period: 2008-2018.Major taxa studied: Invertebrates, vertebrates, and trees. MethodsWe analyzed species occupancy data from 452 habitat patches. We quantified alpha, beta, and gamma diversity, assessed species-area relationships, and applied generalized dissimilarity modelling to test the role of patch area, connectivity, and habitat quality--proxied through environmental variables, including vegetation complexity, water presence, and forest isolation--in shaping community composition. ResultsAlpha diversity increased significantly with area, although small patches (usually < 5 ha) disproportionately contributed to beta diversity. Per unit area, groups of small patches yielded higher gamma diversity than equivalent areas of large patches, particularly for trees and invertebrates. Community composition was strongly influenced by patch area, with effects mediated by vegetation complexity, water, and isolation, with responses differing among taxa. Main conclusionsSmall habitat patches play a critical role in enhancing overall urban biodiversity. They increase species richness through cumulative area effects and promote community turnover (mediated by environmental heterogeneity). Maintaining networks of small patches alongside large green spaces is therefore key to conserving biodiversity in urban landscapes.

ecology↗

bioRxiv2026

Alterations in amygdala function explain how aging and loneliness impair trust learning

Functional relationships are essential for healthy aging and they rely on social cognition skills such as establishing and monitoring whom to trust. However, aging and loneliness can negatively affect social brain function, potentially leading to a vicious cycle. Using functional MRI and computational modeling we investigated trust learning in a sample of neurotypical older (64-84 years, n=29f/23m) compared to younger adults (20-33 years, n=31f/31m). Older participants displayed lower initial trust and less trust learning when repeatedly interacting with a trustworthy and an untrustworthy trustee. Their basolateral and central amygdala activation was lower during trust decisions, and this was associated with less optimal trust behavior. Computational modeling also revealed that a crucial learning parameter, trust prediction error precision, was decoupled from basolateral amygdala activation, and this effect was pronounced in lonely older adults. These findings indicate that differences in amygdala function and reward signaling at older age and higher loneliness could drive detrimental effects on trust learning, leading to poorer social cognition and putting individuals sociality and well-being at risk.

neuroscience↗

bioRxiv2025

A single large restored patch has lower tree diversity than several smaller ones

1. Restoration initiatives often target restoring the largest possible amount of habitat to provide the greatest benefits for biodiversity. However, the optimal configuration (e.g., the size and number of restored patches) of habitat, given a fixed total area, remains an unresolved question. 2. Here, we ask whether restoring a single large habitat patch or a mixture of smaller patches of the same total area supports higher plant diversity. To address this question, we measured taxonomic, phylogenetic, and functional diversity of all naturally recruiting woody species in 52 restored vegetation patches in Jambi Province, Sumatra, Indonesia. Thirteen restored patches of each of four sizes (25, 100, 400, and 1,600 m{superscript 2}) were established within conventional oil palm plantations six years before vegetation sampling. From these 52 patches, we generated 750 random comparisons between a single large patch vs. several small patches, ensuring equal total area (100, 400, or 1,600 m{superscript 2}). We evaluated taxonomic, phylogenetic, and functional diversity separately for all species, for native species, and for native forest species, using three diversity measures: species richness, the exponential of Shannon entropy, and the inverse of Simpson concentration. 3. Our findings indicate that restoring several smaller patches results in greater taxonomic, phylogenetic, and functional diversity of recruiting woody species than restoring a single large patch of the same total area. This result holds across the three total habitat areas (100, 400, and 1,600 m{superscript 2}), all species groupings, and all diversity metrics. As expected, species diversity also increased with total area in all cases. 4. Our findings challenge restoration strategies that focus exclusively on enlarging patches. Instead, biodiversity will be enhanced by increasing the total restored area across many patches of different sizes, including very small ones (e.g., 25 m{superscript 2}).

ecology↗

bioRxiv2022

30x30 biodiversity gains rely on national coordination

Protecting 30% of land by 2030 is an invaluable opportunity to combat the ongoing biodiversity crisis, but critical questions remain regarding what biodiversity to prioritize, how to coordinate protection, and how to incorporate global change. Here, we evaluate how well different 30x30 expansion scenarios capture the climatically viable ranges of Canadian terrestrial vertebrates, plants, and butterflies. We find that national coordination protects vastly more biodiversity (65% of species; 40% of species-at-risk) than regional approaches, which safeguard at least 33% fewer species and 75% fewer species-at-risk. Whereas prioritizing different taxa or biodiversity facets (e.g., phylogenetic diversity) incur smaller trade-offs. Surprisingly, national priorities closely match transnational ones, indicating that national coordination could efficiently contribute to global targets while protecting Canadas biodiversity at large.

ecology↗

bioRxiv2022

Hungry for compliments? Ghrelin is not associated with neural responses to social rewards or their pleasantness

The stomach-derived hormone ghrelin motivates food search and stimulates food consumption, with highest plasma concentrations before a meal and lowest shortly after. However, ghrelin also appears to affect the value of non-food rewards such as interaction with rat conspecifics, and monetary rewards in humans. The present pre-registered study investigated how nutritional state and ghrelin concentrations are related to the subjective and neural responses to social and non-social rewards. In a cross-over feed-and-fast design, 67 healthy volunteers (20 women) underwent functional magnetic resonance imaging (fMRI) in a hungry state and after a meal with repeated plasma ghrelin measurements. In task 1, participants received social rewards in the form of approving expert feedback, or non-social computer reward. In task 2, participants rated the pleasantness of compliments and neutral statements. Nutritional state and ghrelin concentrations did not affect the response to social reward in task 1. In contrast, ventromedial prefrontal cortical activation to non-social rewards was reduced when the meal strongly suppressed ghrelin. In task 2, fasting increased activation in the right ventral striatum during all statements, but ghrelin concentrations were neither associated with brain activation nor with experienced pleasantness. Complementary Bayesian analyses provided moderate evidence for a lack of correlation between ghrelin concentrations and behavioral and neural responses to social rewards, but moderate evidence for an association between ghrelin and non-social rewards. This suggests that ghrelins influence may be restricted to non-social rewards. Social rewards implemented via social recognition and affirmation may be too abstract and complex to be susceptible to ghrelins influence. In contrast, the non-social reward was associated with the expectation of a material object that was handed out after the experiment. This may indicate that ghrelin might be involved in anticipatory rather than consummatory phases of reward.

neuroscience↗

bioRxiv2021

Zooplankton as a transitional host for Escherichia coli in freshwater

This study shows that Escherichia coli can be temporarily enriched in zooplankton in natural conditions and that these bacteria can belong to different phylogroups and sequence types including environmental as well as clinical and animal isolates. We isolated 10 E. coli strains and sequenced the genomes of two of them. Phylogenetically the two isolates were closer to strains isolated from poultry meat than with freshwater E. coli, albeit their genomes were smaller than those from poultry. After isolation and fluorescent protein tagging of strains ED1 and ED157 we show that Daphnia sp. can take up these strains and release them alive again, thus forming a temporary host for E. coli. In a chemostat experiment we show that the association does not prolong the bacterial long-term survival, but that at low abundances it does also not significantly reduce the bacterial numbers. We demonstrate that E. coli does not belong to the core microbiota of Daphnia, suffers from competition by the natural microbiota of Daphnia, but can profit from its carapax to survive in water. All in all, this study suggests that the association of E. coli to Daphnia is only temporary but that the cells are viable therein and this might allow encounters with other bacteria for genetic exchange and potential genomic adaptations to the freshwater environment. ImportanceThe contamination of freshwaters with faecal derived bacteria is of major concern regarding drinking water acquisition and recreational activities. Ecological interactions promoting their persistence are still very scarcely studied. This study, which analyses the survival of E. coli in the presence of zooplankton, is thus of ecological as well as water safety relevance.

ecology↗

bioRxiv2021

In amygdala we trust: different contributions of the basolateral and central amygdala in learning whom to trust

Human societies are built on cooperation and mutual trust, but not everybody is trustworthy. Research on rodents suggests an essential role of the basolateral amygdala (BLA) in learning from social experiences (Hernandez-Lallement J et al., 2016), which was also confirmed in human subjects with selective bilateral BLA damage as they failed to adapt their trust behavior towards trustworthy vs. untrustworthy interaction partners (Rosenberger LA et al., 2019). However, neuroimaging in neurotypical populations did not consistently report involvement of the amygdala in trust behavior. This might be explained by the difficulty of differentiating between amygdalas structurally and functionally different subnuclei, i.e., the BLA and central amygdala (CeA), which have even antagonistic features particularly in trust behavior (van Honk J et al., 2013). Here, we used fMRI of the amygdala subnuclei of neurotypical adults (n=31f/31m) engaging in the repeated trust game. Our data show that both the BLA and the CeA play a role and indeed differentially: While the BLA was most active when obtaining feedback on whether invested trust had been reciprocated or not, the CeA was most active when subjects were preparing their next trust decision. In the latter phase, improved learning was associated with higher activation differences in response to untrustworthy vs. trustworthy trustees, in both BLA and CeA. Our data not only translate to rodent models and support our earlier findings in BLA-damaged subjects, but also show the specific contributions of other brain structures in the amygdala-centered network in learning whom to trust, and better not to trust. SIGNIFICANCE STATEMENTIn this fMRI study, the central amygdala was found active during trust behavior planning, while the basolateral amygdala was active during outcome evaluation. When planning trust behavior, central and basolateral amygdala activation differences between the players was related to whether participants learned to differentiate the players trustworthiness. Nucleus accumbens tracked whether trust was reciprocated but was not related to learning. This suggests learning whom to trust is not related to reward processing in the nucleus accumbens but rather to engagement of the basolateral amygdala. This study overcomes major empirical gaps between animal models and human neuroimaging and shows how different amygdala subnuclei and connected areas orchestrate learning to form different subjective trustworthiness beliefs about others and guide trust choice behavior.

neuroscience↗

bioRxiv2020

Placebo analgesia does not reduce empathy for naturalistic depictions of others' pain in a somatosensory specific way

Empathy for pain involves the affective-motivational and sensory-discriminative pain network. The shared representations account postulates that sharing anothers pain recruits underlying brain functions also engaged during first-hand pain. Critically, causal evidence for this has only been shown for affective pain processing, while the specific contribution of ones own somatosensory system to empathy remains controversial. Experimental paradigms used in previous studies did not a) direct attention towards a specific body part or b) employed naturalistic depictions of others pain, which could explain the absence of somatosensory effects. In this preregistered fMRI study, we thus aimed to test whether a causal manipulation of first-hand pain affects processing of empathy in a somatotopically- matched manner. Forty-five participants underwent a placebo analgesia induction in the right hand and observed pictures of right vs. left hands in pain. We found neither behavioral nor neural evidence for laterality-specific modulation of empathy for pain. However, exploratory analyses revealed a general effect of the placebo on empathy, and higher brain activity in bilateral anterior insula when viewing others hands in pain corresponding to ones own placebo hand. These results refine our knowledge regarding the mechanisms underlying empathy for pain by specifying the influence of first-hand pain on empathic responding.

neuroscience↗

bioRxiv2020

Another's pain in my brain: No evidence that placebo analgesia affects the sensory-discriminative component in empathy for pain

The shared representations account of empathy suggests that sharing other peoples emotions relies on neural processes similar to those engaged when directly experiencing such emotions. Recent research corroborated this by showing that placebo analgesia resulted in reduced pain empathy and decreased activation in shared neural networks. However, those studies did not report any placebo-related variation of somatosensory engagement during pain empathy. The experimental paradigms used in these studies did not direct attention towards a specific body part in pain, which may explain the absence of effects for somatosensation. The main objective of this preregistered study was to implement a paradigm overcoming this limitation, and to investigate whether placebo analgesia may also modulate the sensory-discriminative component of empathy for pain. We induced a localized, first-hand placebo analgesia effect in the right hand of 45 participants by means of a placebo gel and conditioning techniques, and compared this to the left hand as a control condition. Participants underwent a pain task in the MRI scanner, receiving painful or non-painful electrical stimulation on their left or right hand, or witnessing another person receiving such stimulation. In contrast to a robust localized placebo analgesia effect for self-experienced pain, the empathy condition showed no differences between the two hands, neither for behavioral nor neural responses. We thus report no evidence for somatosensory sharing in empathy, while replicating previous studies showing overlapping brain activity in the affective-motivational component for first-hand and empathy for pain. Hence, in a more rigorous test aiming to overcome limitations of previous work, we again find no causal evidence for the engagement of somatosensory sharing in empathy. Our study refines the understanding of the neural underpinnings of empathy for pain, and the use of placebo analgesia in investigating such models. HighlightsO_LIInvestigated placebo modulation of somatosensory and affective components of pain C_LIO_LILocalized placebo analgesia effects for self-report and fMRI of first-hand pain C_LIO_LINo evidence for such effects in empathy for pain C_LIO_LISuggests that somatosensory sharing does not play a critical role in pain empathy C_LI

neuroscience↗

bioRxiv2019

Age-related changes in human emotional egocentricity: evidence from multi-level neuroimaging

Emotional egocentric bias (EEB) occurs when, due to a partial failure in self-other distinction, empathy for anothers emotions is influenced by our own emotional state. Recent studies have demonstrated that this bias is higher in children, adolescents and older adults than in young adults. In the latter, overcoming emotional egocentrism has been associated with significant activity in the right supramarginal gyrus (rSMG), as well as increased connectivity between rSGM and somatosensory and visual cortices. Investigations on the neural correlates of EEB in adolescents and older adults are missing. We filled this gap, by asking female participants from three different age groups (adolescents, young adults and older adults, N=92) to perform a well-validated EEB task (Silani et al., 2013) in an MRI scanner. A multi-level analysis approach of MRI data including functional segregation, effective connectivity and structural analyses was adopted. Results revealed higher EEB in older compared to young adults and a comparable EEB in adolescents and young adults. Age-related differences in EEB were associated with differences in task-related rSMG connectivity with somatosensory cortices, especially with S2, which acted as a partial mediator between age and EEB. These findings provide further evidence for the crucial role of the rSMG in self-other distinction in the emotional domain, and suggest that the age-related decline in overcoming EEB is best explained by changes in rSMG connectivity rather than decreased regional activity in that area. This advocates a more systematic investigation of task-related connectivity in studies on aging and life-span development of social-cognitive phenomena.\n\nSignificance StatementEmpathy comprises both the ability to identify and share anothers emotional state, and the ability to disentangle ones own from the others emotional state. When self- and other-related emotions are conflicting, empathy might be negatively influenced by egocentric tendencies. This phenomenon is referred to as emotional egocentric bias (EEB), with previous research showing that its extent changes across the life-span. Here, we provide evidence that age-related differences in EEB are mainly associated with age-related changes in rSMG effective connectivity, and in particular that higher EEB in older adults is associated to lower rSMG effective connectivity with somatosensory cortices. These findings suggest the importance, particularly in aging, of intact functional connectivity for optimal socio-cognitive functioning.

neuroscience↗

bioRxiv2017

Using MinION to characterize dog skin microbiota through full-length 16S rRNA gene sequencing approach

The most common strategy to assess microbiota is sequencing specific hypervariable regions of 16S rRNA gene using 2nd generation platforms (such as MiSeq or Ion Torrent PGM). Despite obtaining high-quality reads, many sequences fail to be classified at the genus or species levels due to their short length. This pitfall can be overcome sequencing the full-length 16S rRNA gene (1,500bp) by 3rd generation sequencers.\n\nWe aimed to assess the performance of nanopore sequencing using MinION on characterizing microbiota complex samples. First set-up step was performed using a staggered mock community (HM-783D). Then, we sequenced a pool of several dog skin microbiota samples previously sequenced by Ion Torrent PGM. Sequences obtained for full-length 16S rRNA with degenerated primers retrieved increased richness estimates at high taxonomic level (Bacteria and Archaea) that were missed with short-reads. Besides, we were able to obtain taxonomic assignments down to species level, although it was not always feasible due to: i) incomplete database; ii) primer set chosen; iii) low taxonomic resolution of 16S rRNA gene within some genera; and/or iv) sequencing errors. Nanopore sequencing of the full-length 16S rRNA gene using MinION with 1D sequencing kit allowed us inferring microbiota composition of a complex microbial community to lower taxonomic levels than short-reads from 2nd generation sequencers.

microbiology↗