Biology subjects

Leopold, D. R.

Publications and source records attributed to Leopold, D. R..

5 recordsLinked to original sources

bioRxiv2022

Efficiency of heterogenous functional connectomes explains variance in callous-unemotional traits after computational lesioning of cortical midline and salience regions

Callous-unemotional (CU) traits are a youth antisocial phenotype hypothesized to be a result of differences in the integration of multiple brain systems. However, mechanistic insights into these brain systems are a continued challenge. Where prior work describes activation and connectivity of the connectome in relation to these systems, new mechanistic insights can be derived by removing nodes and characterizing changes in network properties (hereafter referred to as computational lesioning) to characterize the resilience and vulnerability of the brains functional connectome. Here, we study the resilience of connectome integration in CU traits by estimating changes in efficiency after computationally lesioning individual-level connectomes. From resting-state data of 86 participants (48% female, age 14.52{+/-}1.31) drawn from the Nathan Kline institutes Rockland study, individual-level connectomes were estimated using graphical lasso. Computational lesioning was conducted both sequentially and by targeting global and local hubs. We calculated changes in network efficiency after each lesion. Then, elastic net regression was applied to determine how these changes explained variance in CU traits. Follow-up analyses characterized modeled node hubs, examined moderation, determined impact of targeting, and decoded the brain mask by comparing regions to meta-analytic maps. Elastic net regression revealed that computational lesioning of 23 nodes, network modularity, and Tanner stage explained variance in CU traits. Hub assignment of selected hubs differed at higher CU traits. No evidence for moderation between simulated lesioning and CU traits was found. Targeting global hubs increased efficiency and targeting local hubs had no effect at higher CU traits. Identified brain mask meta-analytically associated with more emotion and cognitive terms. Although reliable patterns were found across participants, adolescent brains were heterogeneous even for those with a similar CU traits score. Adolescent brain response to simulated lesioning revealed a pattern of connectome resiliency and vulnerability that explains variance in CU traits, which can aid prediction of youth at greater risk for higher CU traits.

neuroscience↗

bioRxiv2022

Resting-state connectivity underlying cognitive controls association with perspective taking in callous-unemotional traits

Callous-Unemotional (CU) traits are often associated with impairments in perspective taking and cognitive control (regulating goal directed behavior); and adolescents with CU traits demonstrate aberrant brain activation/connectivity in areas underlying these processes. Together cognitive control and perspective taking are thought to link mechanistically to explain CU traits. Because increased cognitive control demands modulate perspective taking ability among both typically developing samples and individuals with elevated CU traits, understanding the neurophysiological substrates of these constructs could inform efforts to alleviate societal costs of antisocial behavior. The present study uses GIMME to examine the heterogenous functional brain properties (i.e., connection density, node centrality) underlying cognitive controls influence on perspective taking among adolescents on a CU trait continuum. Results reveal that cognitive control had a negative indirect association with CU traits via perspective taking; and brain connectivity indirectly associated with lower CU traits - specifically the social network via perspective taking and conflict network via cognitive control. Additionally, less negative connection density between the social and conflict networks was directly associated with higher CU traits. Our results support the growing literature on cognitive controls influence on socio-cognitive functioning in CU traits and extends that work by identifying underlying functional brain properties.

neuroscience↗

bioRxiv2020

Ericoid mycorrhizal diversity increases with soil age and progressive phosphorus limitation across a 4.1 million-year chronosequence

Ericaceous plants rely on ericoid mycorrhizal fungi for nutrient acquisition. However, the factors that affect the composition and structure of these fungal communities remain largely unknown. Here, we use a 4.1-myr soil chronosequence in Hawaii to test the hypothesis that changes in nutrient availability with soil age determine the diversity and species composition of fungi associated with ericoid roots. We sampled roots of a native Hawaiian plant, Vaccinium calycinum, and used DNA metabarcoding to quantify changes in fungal diversity and species composition. We also used a fertilization experiment at the youngest and oldest sites to assess the importance of nutrient limitation. We found an increase in diversity and a clear pattern of species turnover across the chronosequence, driven largely by putative ericoid mycorrhizal fungi. Fertilization with nitrogen at the youngest site and phosphorus at the oldest site reduced total fungal diversity, suggesting a direct role of nutrient limitation. Our results also reveal the presence of novel fungal species associated with Hawaiian Ericaceae and suggest a greater importance of phosphorus availability for communities of ericoid mycorrhizal fungi than is generally assumed.

ecology↗

bioRxiv2020

Greater local diversity under older species pools may arise from enhanced competitive equivalence

Local ecological communities tend to contain more species when they are located within a geologically older region, a pattern that has traditionally been attributed to the accumulation of species in the regional species pool. In this explanation, local species interactions are assumed to play a minor role in the formation of the regional species pool, which is instead thought to be driven by speciation and dispersal occurring across larger areas. Here, we provide evidence suggesting a more important role of local species interactions than generally assumed. In an experiment in which we assembled 320 local communities of root-associated fungi under 80 species pools, we varied the species richness of the experimental species pools and the mean age of the sites from which we collected the fungal species across a 4-myr soil chronosequence in Hawaii. We found that realized local species diversity in the assembled communities increased more extensively with increasing species-pool richness when species were from older sites. We also found that older species pools had lower functional and phylogenetic diversity, indicating that the evolution of greater competitive equivalence among potential colonists enabled higher local diversity under older species pools. Our results suggest that the tendency of older regions to have higher local richness arises not simply because older species pools are more speciose, but also because the constituent species have evolved traits that allow them to co-occur more readily in local communities.

ecology↗

bioRxiv2020

Joint effects of host genotype and species arrival order govern plant microbiome composition and function

The composition of host-associated microbiomes can have important consequences for host health and fitness [1-3]. Yet, we still lack understanding of many fundamental processes that determine microbiome composition [4,5]. There is mounting evidence that historical contingency during microbiome assembly may overshadow more deterministic processes, such as the selective filters imposed by host traits [6-8]. More specifically, species arrival order has been frequently shown to affect microbiome composition [9-12], a phenomenon known as priority effects [13-15]. However, it is less clear whether priority effects during microbiome assembly are consequential for the host [16], or whether intraspecific variation in host traits can alter the trajectory of microbiome assembly under priority effects. In a greenhouse inoculation experiment using the black cottonwood (Populus trichocarpa) foliar microbiome, we manipulated host genotype and the colonization order of common foliar fungi. We quantified microbiome assembly outcomes using fungal marker-gene sequencing and measured susceptibility of the colonized host to a leaf rust pathogen, Melampsora x columbiana. We found that the effect of species arrival order on microbiome composition, and subsequent disease susceptibility, depended on the host genotype. Additionally, we found that microbiome assembly history can affect host disease susceptibility independent of microbiome composition at the time of pathogen exposure, suggesting that the interactive effects of species arrival order and host genotype can decouple community composition and function. Overall, these results highlight the importance of a key process underlying stochasticity in microbiome assembly while also revealing which hosts are most likely to experience these effects.

ecology↗