Severe disturbance overflows the stabilizing buffer of variable biotic interactions

Recent studies have uncovered that biotic interaction strength varies over time in real ecosystems intrinsically and/or responding to anthropogenic disturbances. Little is known, however, about whether such interaction variability strengthens or weakens community resistance against disturbances. Here, we examine how the change in interaction strength after pesticide application mediates disturbance impacts on a freshwater community using outdoor mesocosms. We show that the change in interaction strength buffered the disturbance impact but amplified it once the disturbance severity exceeded a certain threshold. Importantly, we also show that interactions fluctuating more temporally under no disturbances were more changeable in response to pesticide applications. Our findings suggest that a severe disturbance may have a surprise impact on a biological community amplified by their own interaction variability, but the possibility still remains that we can predict the consequences of the disturbance by measuring the interaction variability before the disturbance occurs.

Continental-Scale Paddy Soil Bacterial Community Structure, Function, and Biotic Interaction

Rice fields provide food for over half of the world’s human population. The ecology of paddy soil microbiomes is shaped by human activities, which can have a profound impact on rice yield, greenhouse gas emissions, and soil health.

Interspecific Interactions II: Competition and Mutualism

Competition and mutualism are important forms of biotic interaction in aquatic communities. Quantification of the population and community-level effects of these interactions has historically been less common in fisheries analyses than predation. In part, this reflects the difficulties in conducting controlled experiments for larger-bodied organisms in aquatic environments. Documenting competition entails not only identifying patterns of shared resource use but evidence that these resources are limiting. Inferences concerning competitive interactions in non-experimental settings may be possible if histories of population change for putative competitors are available and quantifiable interventions involving the addition of a species (through deliberate or inadvertent introductions) or a differential reduction in abundance of the species through harvesting is undertaken. Care must be taken to account for other changes in the environment in these uncontrolled quasi-experiments. Mutualistic interactions are widely recognized in aquatic ecosystems but far less commonly quantified than competition.

Four cases of prey-predator interaction (anuran-snake) through their geographical distribution

The biotic interaction prey-predator between one anuran species and one snake species, in some cases have been reported just in one geographical location, and in other cases have been reported several records through the geographical distribution of both interacting species. In this study we report four cases of anurans predation by snakes in different geographical location to the previous records. The previous and new records suggest that the biological interaction prey-predator between two species is maintained regardless of the geographical location and elevation. The consequences of these kind of biotic interactions for the predator and prey requires further study.

Assessing effects of genetic, environmental, and biotic gradients in species distribution modelling

To develop more reliable marine species distribution models (SDMs), we examine how genetic, climatic, and biotic interaction gradients give rise to prediction error in marine SDM. Genetic lineages with distinct ecological requirements spanning genetic gradients have yet to be treated separately in marine SDM, which are often constrained to modeling the potential distribution of one biological unit (e.g. lineage or species) at a time. By comparing SDM performance for the whole species or where observation and predictions were partitioned among geographically discontinuous genetic lineages, we first identified the appropriate biological unit for modeling sea scallop. Prediction errors, in particular contiguous omissions at the northern range margins were effectively halved in genetic lineage SDM (Total error=15%) verses whole species SDM. Remaining SDM prediction error was strongly associated with: i) Sharp climatic gradients (abrupt and persistent spatial shifts in limiting temperatures) found within continental shelf breaks and bottom channels. ii) A biotic gradient in the predation of sea scallop juveniles by the sand star within the Hudson Shelf USA. Our findings highlight how the accuracy of marine SDM is dependent on capturing the appropriate biological unit for modeling (e.g. lineages rather than species) and adequately resolving limiting abiotic and biotic interaction gradients.

Adaptation and latitudinal gradients in species interactions: nest predation in birds

The “biotic interactions” hypothesis—that stronger interspecific interactions in the tropics drive faster evolution and speciation, giving rise to the latitudinal diversity gradient—has inspired many tests of whether certain biotic interactions are indeed stronger in the tropics. However, the possibility that populations have adapted to latitudinal differences in species interactions, blunting effects on evolutionary rates, has been largely ignored. Here we show that mean rates of nest predation experienced by land birds vary minimally with latitude in the Western Hemisphere. This result is surprising because nest predation in birds is a canonical example of a strong tropical biotic interaction. We explain our finding by demonstrating that (1) rates of nest predation are in fact higher in the tropics, but only when controlling for the length of the nesting period, (2) long nesting periods are associated with reduced predation rates, and (3) tropical birds have evolved particularly long nesting periods. We suggest this is a case example of how adaptation to a biotic interaction can alter observed latitudinal gradients in interaction strength, potentially equalizing evolutionary rates among latitudes. More broadly, we advocate for tests of the biotic interactions hypothesis to consider both latitudinal patterns in interaction strength and evolutionary responses to these interactions.