Mark Christopher Bitter

All Publications

• Wide-ranging consequences of priority effects governed by an overarching factor. eLife Chappell, C. R., Dhami, M. K., Bitter, M. C., Czech, L., Herrera Paredes, S., Barrie, F. B., Calderon, Y., Eritano, K., Golden, L., Hekmat-Scafe, D., Hsu, V., Kieschnick, C., Malladi, S., Rush, N., Fukami, T. 2022; 11

  Abstract

  Priority effects, where arrival order and initial relative abundance modulate local species interactions, can exert taxonomic, functional, and evolutionary influences on ecological communities by driving them to alternative states. It remains unclear if these wide-ranging consequences of priority effects can be explained systematically by a common underlying factor. Here, we identify such a factor in an empirical system. In a series of field and laboratory studies, we focus on how pH affects nectar-colonizing microbes and their interactions with plants and pollinators. In a field survey, we found that nectar microbial communities in a hummingbird-pollinated shrub, Diplacus (formerly Mimulus) aurantiacus, exhibited abundance patterns indicative of alternative stable states that emerge through domination by either bacteria or yeasts within individual flowers. In addition, nectar pH varied among D. aurantiacus flowers in a manner that is consistent with the existence of these alternative stable states. In laboratory experiments, Acinetobacter nectaris, the bacterium most commonly found in D. aurantiacus nectar, exerted a strongly negative priority effect against Metschnikowia reukaufii, the most common nectar-specialist yeast, by reducing nectar pH. This priority effect likely explains the mutually exclusive pattern of dominance found in the field survey. Furthermore, experimental evolution simulating hummingbird-assisted dispersal between flowers revealed that M. reukaufii could evolve rapidly to improve resistance against the priority effect if constantly exposed to A. nectaris-induced pH reduction. Finally, in a field experiment, we found that low nectar pH could reduce nectar consumption by hummingbirds, suggesting functional consequences of the pH-driven priority effect for plant reproduction. Taken together, these results show that it is possible to identify an overarching factor that governs the eco-evolutionary dynamics of priority effects across multiple levels of biological organization.

  View details for DOI 10.7554/eLife.79647

  View details for PubMedID 36300797

• Molecular basis of ocean acidification sensitivity and adaptation in Mytilus galloprovincialis. iScience Kapsenberg, L., Bitter, M. C., Miglioli, A., Aparicio-Estalella, C., Pelejero, C., Gattuso, J., Dumollard, R. 2022; 25 (8): 104677

  Abstract

  Predicting the potential for species adaption to climate change is challenged by the need to identify the physiological mechanisms that underpin species vulnerability. Here, we investigated the sensitivity to ocean acidification in marine mussels during early development, and specifically the trochophore stage. Using RNA and DNA sequencing and in situ RNA hybridization, we identified developmental processes associated with abnormal development and rapid adaptation to low pH. Trochophores exposed to low pH seawater exhibited 43 differentially expressed genes. Gene annotation and in situ hybridization of differentially expressed genes point to pH sensitivity of (1) shell field development and (2) cellular stress response. Five genes within these two processes exhibited shifts in allele frequencies indicative of a potential for rapid adaptation. This case study contributes direct evidence that protecting species' existing genetic diversity is a critical management action to facilitate species resilience to climate change.

  View details for DOI 10.1016/j.isci.2022.104677

  View details for PubMedID 35847553