Biology subjects

Larson, J. G.

Publications and source records attributed to Larson, J. G..

4 recordsLinked to original sources

bioRxiv2024

Increased host diversity limits bacterial generalism but may promote microbe-microbe interactions

Host-associated bacteria vary in their host breadth, which can impact ecological interactions. By colonizing diverse hosts, host generalists can have disproportionate ecological impacts. For bacteria, host generalism may advantageous, particularly when the availability of specific hosts is variable. It is unclear how much the ability to evolve generalism, by inhabiting diverse hosts, is constrained in host-associated bacteria. We hypothesized that constraints on bacterial generalism will differ depending on the availability of specific host species. To test this, we assessed patterns of diversity and specialization in the cloacal microbiomes of reptile communities from the temperate zone to the tropics, where the diversity and abundance of host species varies substantially. Within these communities, generalist taxa tended to be Proteobacteria, whereas specialists tended to be Firmicutes. We found that bacterial generalists were less prevalent in the highest diversity host communities, and in keeping with this, Proteobacteria were less diverse in these communities. Generalist taxa became relatively less widespread across host species only in the two most diverse host communities. We therefore conclude that the constraint on generalism is not driven by absolute incompatibility with some host species, but rather from competition with host adapted specialist lineages. In the high-diversity communities, we found that the successful generalists, typically Proteobacteria, were disproportionately likely to co-occur with one another across evolutionarily disparate hosts within the community. Our data indicate that bacterial lineages can adapt to the evolutionary pressures of high diversity host communities either by specializing on hosts or by forming cohorts of co-occurring bacterial lineages.

ecology↗

bioRxiv2022

Global change drivers and the risk of infectious disease

Anthropogenic change is contributing to the rise in emerging infectious diseases, but it remains unclear which global change drivers most increase disease and under what contexts. We amassed a dataset from the literature that includes 1,832 observations of infectious disease responses to global change drivers across 1,202 host-parasite combinations. We found that biodiversity loss, climate change, and introduced species were associated with increases in disease-related endpoints or harm (i.e., enemy release for introduced species), whereas urbanization was associated with decreases in disease endpoints. Natural biodiversity gradients, deforestation, forest fragmentation, and most classes of chemical contaminants had non-significant effects on these endpoints. Overall, these results were consistent across human and non-human diseases. Context-dependent effects of the global change drivers on disease were common and are discussed. These findings will help better target disease management and surveillance efforts towards global change drivers that increase disease. One-Sentence SummaryHere we quantify which global change drivers increase infectious diseases the most to better target global disease management and surveillance efforts.

ecology↗

bioRxiv2019

Convergence and divergence in anti-predator displays: A novel approach to quantitative behavioural comparison in Neotropical snakes

Animals in nature use diverse strategies to evade or deter their predators, including many vivid behavioural displays only qualitatively described from field encounters with natural predators or humans. Within venomous snake mimicry, stereotyped anti-predator displays are suggested to be a critical component of the warning signal given by toxic models and thus under strong selection for independent convergence in mimetic species. However, no studies have systematically quantified variation in snake anti-predator displays across taxonomically broad clades to test how these behaviours evolve across species within a phylogenetic comparative methods framework. Here we describe a new, high-throughput approach for collecting and scoring snake anti-predator displays in the field that demonstrates both low observer bias and infinite extension across any species. Then, we show our methods utility in quantitatively comparing the behaviour of 20 highly-divergent snake species from the Amazonian lowlands of Peru. We found that a simple experimental setup varying simulated predator cues was very successful in eliciting anti-predator displays across species and that high-speed videography captured a greater diversity of behavioural responses than described in the literature. We also found that although different display components evolve at different rates with complicated patterns of covariance, there is clear evidence of evolutionary convergence in anti-predator displays among distantly related elapid coral snakes and their colubrid mimics. We conclude that our approach provides new opportunity for analyses of snake behaviour, kinematics, and the evolution of anti-predator signals more generally, especially macroevolutionary analyses across clades with similarly intractable behavioural diversity.

animal behavior and cognition↗

bioRxiv2019

A kinematic analysis of Micrurus coral snakes reveals unexpected variation in stereotyped anti-predator displays within a mimicry system

O_LIWarning signals in chemically defended organisms are critical components of predator-prey interactions, often requiring multiple coordinated display components for a signal to be effective. When threatened by a predator, venomous coral snakes (genus Micrurus) display a vigorous, non-locomotory thrashing behaviour that has been only qualitatively described. Given the high-contrast and often colourful banding patterns of these snakes, this thrashing display is hypothesized to be a key component of a complex aposematic signal under strong stabilizing selection across species in a mimicry system.\nC_LIO_LIBy experimentally testing snake response across simulated predator cues, we analysed variation in the presence and expression of a thrashing display across five species of South American coral snakes.\nC_LIO_LIAlthough the major features of the thrash display were conserved across species, we found significant variation in the propensity to perform a display at all, the duration of thrashing, and the curvature of snake bodies that was mediated by predator cue type, snake body size, and species identity. We also found an interaction between curve magnitude and body location that clearly shows which parts of the display vary most across individuals and species.\nC_LIO_LIOur results suggest that contrary to the assumption in the literature that all species and individuals perform the same display, a high degree of variation persists in thrashing behaviour exhibited by Micrurus coral snakes despite presumably strong selection to converge on a common signal. This quantitative behavioural characterization presents a new framework for analysing the non-locomotory motions displayed by snakes in a broader ecological context, especially for signalling systems with complex interaction across multiple modalities.\nC_LI

animal behavior and cognition↗