EEOB Publications March 1-March 31
Interspecific Eavesdropping on Ant Chemical Communication
Rachelle M. M. Adams, Rachel L. Wells, Stephen P. Yanoviak, Christopher J. Frost, and Eduardo G. P. Fox. 2020. Front. Ecol. Evol. https://doi.org/10.3389/fevo.2020.00024
Chemical communication is a fundamental, highly complex component of social insect societies. Ants in particular employ a remarkable diversity of chemical signals to maintain social cohesion among nestmates, gain essential resources through coordinated foraging, and warn of danger. Although the chemicals used can be functionally specific, they are vulnerable to exploitation by eavesdropping natural enemies (e.g., parasitoids, predators, parasites) and other associates (e.g., myrmecophiles). Ant nests are nutrient hotspots due to their collection of resources warranting keen defense systems; yet the heavily defended hideouts are frequently invaded. Many organisms exploit ant species, but how they locate hosts—including what host-derived cues are used—is still poorly understood. Here, we review current knowledge about how ant chemical communication systems can be exploited by unintended receivers. We take a case study approach and illustrate the diversity of ant associates and host traits that may predispose ants to exploitation. We identify knowledge gaps by reviewing host systems and listing: (1) the types of associates (e.g., fly, wasp, beetle) where eavesdropping is likely occurring, organized by the host communication system that is being exploited; (2) the ant parasites that exploit trail pheromones; and (3) the experimentally determined chemicals (i.e., alarm/defensive pheromones), used by eavesdroppers. At least 25 families of arthropods (10 orders) potentially eavesdrop on ant communication systems and nearly 20 host ant species are vulnerable to trail parasite ant species. We also propose future research that will improve our understanding of community assembly by examining host traits (e.g., latitude, nest characteristics, trail system) that influence their susceptibility to eavesdropping associates.
Hypoxia’s impact on pelagic fish populations in Lake Erie: A tale of two planktivores
Joshua P. Stone, Kevin L Pangle, Steven A Pothoven, Henry A. Vanderploeg, Stephen B Brandt, Tomas O. Höök, Thomas H. Johengen, Stuart A. Ludsin. 2020. Canadian Journal of Fisheries and Aquatic Sciences, https://doi.org/10.1139/cjfas-2019-0265
Whether bottom hypoxia has long-lasting consequences for pelagic fish populations remains speculative for most ecosystems. We explored hypoxia’s influence on two pelagic zooplanktivores in Lake Erie that have different thermal preferences: cold-water rainbow smelt (Osmerus mordax) and warm-water emerald shiners (Notropis atherinoides). To assess acute effects, we combined predictive bioenergetics-based modeling with field collections made across the hypoxic season in central Lake Erie during 2005 and 2007. To assess chronic effects, we related fishery-independent and fishery-dependent catches with hypoxia severity and top predator (walleye, Sander vitreus) abundance during 1986-2014. As our modeling predicted, hypoxia altered rainbow smelt movement and distributions, leading to avoidance of cold, hypoxic bottom waters. In response, diets shifted from benthic to pelagic organisms, and consumption and energetic condition declined. These changes were lacking in emerald shiners. Our long-term analyses showed rainbow smelt abundance and hypoxia to be negatively related and suggested that hypoxia-avoidance increases susceptibility to commercial fishing and walleye predation. Collectively, our findings show that hypoxia can negatively affect pelagic fish populations over the long-term, especially those requiring cold water.
Back to the future of a rare plant species of the Chihuahuan desert: tracing distribution patterns across time and genetic diversity as a basis for conservation actions
Ana Gabriela Zacarías-Correa, Andrés Lira-Noriega, Emmanuel Pérez-Calix, Marie-Stéphanie Samain & Andrea D. Wolfe. 2020. Biodivers Conserv. https://doi.org/10.1007/s10531-020-01962-2
Habitat fragmentation and its effects on the persistence of populations and species are of major concern to conservation biology. Penstemon coriaceus is a rare and endemic species from the Mexican Central Plateau and adjacent foothills of the Sierra Madre Occidental and Sierra Madre Oriental, which belongs to the Chihuahuan Desert ecoregion. This is the first study that integrates population genetics and ecological niche modeling analysis as tools to understand the distribution and genetic diversity patterns of a Penstemon species. We used AFLP markers for 144 individuals across 11 populations, and calibrated Ecological niche modeling for three different time periods (current, future and past). Population genetics analysis showed low levels of genetic diversity at the population level and high genetic differentiation among populations. Ecological niche modeling analysis revealed an important decline of the distribution range due to climate change, which can be considered as an indicator for the vulnerability of temperate forest. The integration of both methods revealed that the genetic differentiation observed only show a relationship with the environment variables and the habitat suitability, but not with the geographical distribution of the populations sampled; which indicate the importance of the environmental factors in the determination of genetic processes for P. coriaceus.
Hierarchical multi‐grain models improve descriptions of species’ environmental associations, distribution, and abundance
Katherine Mertes Marta A. Jarzyna Walter Jetz. 2020. Ecological Applications. https://doi.org/10.1002/eap.2117
The characterization of species’ environmental niches and spatial distribution predictions based on them are now central to much of ecology and conservation, but implicitly requires decisions about the appropriate spatial scale (i.e. grain) of analysis. Ecological theory and empirical evidence suggest that range‐resident species respond to their environment at two characteristic, hierarchical spatial grains: (i) response grain, the (relatively fine) grain at which an individual uses environmental resources, and (ii) occupancy grain, the (relatively coarse) grain equivalent to a typical home range. We use a multi‐grain (MG) occupancy model, aided by fine‐grain remotely sensed imagery, to simultaneously estimate species‐environment associations at both grains, conduct grain optimization to measure response grain, and apply this analysis framework to an example species: a medium‐sized bird (Tockus deckeni) in a heterogeneous East African landscape. Based on home range analysis of movement data, we calculate an occupancy grain of 1km for T. deckeni. Using a grain optimization procedure across 32 grains from 10m to 500m, we identify 60m as the most strongly supported response grain for a suite of environmental variables, slightly coarser than opportunistic behavioral observations would have suggested. Validation confirms that the accuracy of the optimized MG occupancy model substantially exceeds that of equivalent single‐grain (SG) occupancy models. We further use a simulation approach to assess the potential impacts of accounting for the multi‐scale structure of species’ environmental requirements on estimates of population size. We find that the more strongly supported MG approach consistently predicts a minimum population sizes in the study landscape that is much lower than that provided by the SG model. This suggests that SG approaches commonly used in conservation applications could lead to overly optimistic abundance and population estimates and that the MG approach may be more appropriate for supporting species conservation goals. More generally, we conclude that multi‐grain approaches of the sort presented, and increasingly enabled by growing high‐resolution remotely sensed data, hold great promise for offering a more mechanistic framework for assessing the appropriate grain(s) for population monitoring and management and enable more reliable estimates of abundances and species’ distributions.