Coevolutionary Dynamics and the Conservation of Mutualisms

The vast majority of studies in conservation biology focus on a single species at a time. However, many of the anthropogenic threats that species face occur via disrupted or enhanced interactions with other organisms. According to one recent analysis, interactions with introduced species, such as predators, parasites, and pathogens, are the eighth leading cause of species endangerment worldwide; they are the primary cause of endangerment in Hawaii and Puerto Rico (Czech and Krausman 1997). Altering interactions not only has ecological effects, but also it can generate selective pressures and evolutionary responses, which may either favor or disfavor the evolutionary persistence of species and interactions. An increased focus on interspecific interactions will thus enlighten our efforts to conserve species and, more pointedly, our ability to understand when species will and will not respond evolutionarily to conservation threats. Such a focus is also critical for efforts to conserve communities as units, because interactions are the crucial and poorly understood link between threatened species and threatened species assemblages. Different types of interspecific interactions are subject to, and generate, some-what different ecological and evolutionary threats. Predator and pathogen introductions can lead to reduction, local exclusion, or extinction of native species (Savidge 1987; Schofield 1989; Kinzie 1992; Steadman 1995; Louda et al. 1997). Rapid evolution in the enemies and/or the victims may also result (Dwyer et al. 1990; Singer and Thomas 1996; Carroll et al. 1998)

Basic Module Theory over Non-Commutative Rings with Computational Aspects of Operator Algebras

The present text surveys some relevant situations and results where basic Module Theory interacts with computational aspects of operator algebras. We tried to keep a balance between constructive and algebraic aspects.Comment: To appear in the Proceedings of the AADIOS 2012 conference, to be published in Lecture Notes in Computer Scienc

Self-optimization, community stability, and fluctuations in two individual-based models of biological coevolution

We compare and contrast the long-time dynamical properties of two individual-based models of biological coevolution. Selection occurs via multispecies, stochastic population dynamics with reproduction probabilities that depend nonlinearly on the population densities of all species resident in the community. New species are introduced through mutation. Both models are amenable to exact linear stability analysis, and we compare the analytic results with large-scale kinetic Monte Carlo simulations, obtaining the population size as a function of an average interspecies interaction strength. Over time, the models self-optimize through mutation and selection to approximately maximize a community fitness function, subject only to constraints internal to the particular model. If the interspecies interactions are randomly distributed on an interval including positive values, the system evolves toward self-sustaining, mutualistic communities. In contrast, for the predator-prey case the matrix of interactions is antisymmetric, and a nonzero population size must be sustained by an external resource. Time series of the diversity and population size for both models show approximate 1/f noise and power-law distributions for the lifetimes of communities and species. For the mutualistic model, these two lifetime distributions have the same exponent, while their exponents are different for the predator-prey model. The difference is probably due to greater resilience toward mass extinctions in the food-web like communities produced by the predator-prey model.Comment: 26 pages, 12 figures. Discussion of early-time dynamics added. J. Math. Biol., in pres

Stellar structure and compact objects before 1940: Towards relativistic astrophysics

Since the mid-1920s, different strands of research used stars as "physics laboratories" for investigating the nature of matter under extreme densities and pressures, impossible to realize on Earth. To trace this process this paper is following the evolution of the concept of a dense core in stars, which was important both for an understanding of stellar evolution and as a testing ground for the fast-evolving field of nuclear physics. In spite of the divide between physicists and astrophysicists, some key actors working in the cross-fertilized soil of overlapping but different scientific cultures formulated models and tentative theories that gradually evolved into more realistic and structured astrophysical objects. These investigations culminated in the first contact with general relativity in 1939, when J. Robert Oppenheimer and his students George Volkoff and Hartland Snyder systematically applied the theory to the dense core of a collapsing neutron star. This pioneering application of Einstein's theory to an astrophysical compact object can be regarded as a milestone in the path eventually leading to the emergence of relativistic astrophysics in the early 1960s.Comment: 83 pages, 4 figures, submitted to the European Physical Journal

Cheating can stabilize cooperation in mutualisms

Mutualisms present a challenge for evolutionary theory. How is cooperation maintained in the face of selection for selfishness and cheating? Both theory and data suggest that partner choice, where one species preferentially directs aid to the more cooperative members of the other species, is central to cooperation in many mutualisms. However, the theory has only so far considered the evolutionary effects of partner choice on one of the species in a mutualism in isolation. Here, we investigate the co-evolution of cooperation and choice in a choosy host and its symbiont. Our model reveals that even though choice and cooperation may be initially selected, it will often be unstable. This is because choice reduces variation in the symbiont and, therefore, tends to remove the selective incentive for its own maintenance (a scenario paralleled in the lek paradox in female choice and policing in within-species cooperation). However, we also show that when variability is reintroduced into symbionts each generation, in the form of less cooperative individuals, choice is maintained. This suggests that the presence of cheaters and cheater species in many mutualisms is central to the maintenance of partner choice and, paradoxically, cooperation itself

On mutualists and exploiters: Plant-Insect coevolution in pollinating seed-parasite systems

We investigate the coevolution of time of flowering and time of pollinator emergence in an obligate association between a plant and an insect that both pollinates and parasitizes flowers. Numerical analysis shows that the system in general evolves towards a time of flowering different from the time favoured by the abiotic environment. The equilibrium towards which the system evolves is a local fitness maximum (an ESS) with respect to mutational variation in flowering time but, for the insect, it can be a local fitness minimum at which selection on mutational variation in the time of insect emergence is disruptive. A consequence of evolutionary convergence to a fitness minimum is that pollinators having an earlier phenology can coexist with pollinators having a later phenology. Since late emerging insects are more likely to encounter and oviposit within previously pollinated flowers, their effect on the plant is more exploitative, leading them to function as cheaters within the system. Thus, in the long term, pollinators and exploiters are likely to be found in stable coexistence in pollinating seedparasite systems

What Are the Plant Reproductive Consequences of Losing a Nectar Robber?

Pollinator declines worldwide are having strong negative consequences for plants. In many communities, antagonistic flower visitors, including nectar robbers, have likely declined in abundance as well. Given the negative effects that these visitors can sometimes inflict, might declines in their populations benefit plants? During the 1970s, the floral visitor community of the Colorado columbine, Aquilegia caerulea (Ranunculaceae), was documented near Gothic, Colorado. At that time, Bombus occidentalis, the Western Bumble bee, was one of its many pollinators, but more commonly acted as its only known nectar robber. Bombus occidentalis abundance has declined precipitously throughout the Western USA since the 1970s. In 2016, we documented the floral visitor community in sites near to those used in the original survey. We then experimentally quantified the effects of nectar robbing, allowing us to estimate the reproductive consequences of losing B. occidentalis. We also quantified the potential pollination services of muscid flies (Muscidae, Diptera). The floral visitor community was dramatically different in 2016 compared to the 1970s. Bombus occidentalis, a frequent A. caerulea visitor from 1969-1976, was infrequently observed visiting the plant, and nectar robbing was negligible. Our experiments suggested that a high level of nectar robbing would lead to significantly reduced fruit set, although not seeds per fruit. Fly visits to flowers were dramatically higher in 2016 compared to the 1970s. We show that, in the absence of bumble bee pollinators, muscid flies significantly reduced fruit set below the self-pollination rate. The negative effect of the increase in these flies likely outweighed any positive effects A. caerulea experienced from the absence of its nectar robber. Although the field observations were conducted in a single year, when they are interpreted in combination with our manipulative experiments, they suggest how A. caerulea may fare in a changing visitation landscape. © 2022 Enviroquest Ltd. All Rights Reserved.Open access journalThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]

A Mechanistic Framework for Understanding the Effects of Climate Change on the Link Between Flowering and Fruiting Phenology

Phenological shifts are a widely studied consequence of climate change. Little is known, however, about certain critical phenological events, nor about mechanistic links between shifts in different life-history stages of the same organism. Among angiosperms, flowering times have been observed to advance with climate change, but, whether fruiting times shift as a direct consequence of shifting flowering times, or respond differently or not at all to climate change, is poorly understood. Yet, shifts in fruiting could alter species interactions, including by disrupting seed dispersal mutualisms. In the absence of long-term data on fruiting phenology, but given extensive data on flowering, we argue that an understanding of whether flowering and fruiting are tightly linked or respond independently to environmental change can significantly advance our understanding of how fruiting phenologies will respond to warming climates. Through a case study of biotically and abiotically dispersed plants, we present evidence for a potential functional link between the timing of flowering and fruiting. We then propose general mechanisms for how flowering and fruiting life history stages could be functionally linked or independently driven by external factors, and we use our case study species and phenological responses to distinguish among proposed mechanisms in a real-world framework. Finally, we identify research directions that could elucidate which of these mechanisms drive the timing between subsequent life stages. Understanding how fruiting phenology is altered by climate change is essential for all plant species but is particularly critical to sustaining the large numbers of plant species that rely on animal-mediated dispersal, as well as the animals that rely on fruit for sustenance. Copyright © 2021 Sandor, Aslan, Pejchar and Bronstein.Open access journalThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]