![]() ![]() ![]() To add rigor, ecologists have noted that for two species to coexist there must be at least two (or a continuum of) limiting factors. It states that no two species can coexist by occupying the same niche at the same place and time. The competitive exclusion principle ( Hardin, 1961) has provided a basis for understanding how species coexist. ![]() Kotler and Brown (2020) have proposed cancer community ecology as a parallel to community ecology in nature to study the mechanisms that promote a diversity of cancer cell types. We suggest here that the different cancer cell types may equate to biodiversity in nature. These types may coexist within tumor microenvironments, across whole tumors, or among tumors within a single patient ( Lloyd et al., 2016). Metrics generally involve genetic and molecular variation, but much of this can be clustered into what appear to be distinct cancer cell phenotypes (e.g., Amaro et al., 2016 Yeo and Guan, 2017 Wooten et al., 2019 Iravani et al., 2021). Diversity also seems the norm in cancers, where cancer biologists recognize much variety among the cancer cells that inhabit tumor ecosystems within patients. Community ecologists construct theories and models to understand how biodiversity might exist, and then test empirically what mechanisms do promote coexistence of different species. Species coexist by preferentially consuming different foods (diet separation), occupying different times and places (habitat separation), or varying in their capacities to avoid hazards and exploit opportunities (predation-based or food-safety trade-offs) (e.g., Pulliam, 1974 Schoener, 1974 Werner and Hall, 1977 Kotler and Brown, 1988 Huntly, 1991 Morris, 2003). Here, in the context of pulsed resources, we (1) develop models of foraging consumers who experience pulsed resources to examine four types of trade-offs that can promote coexistence of phenotypes that do relatively better in richer versus in poorer times, (2) establish that conditions in tumors are conducive for this mechanism, (3) propose and empirically explore biomarkers indicative of the two phenotypes (HIF-1, GLUT-1, CA IX, CA XII), and (4) and compare cream skimmer and crumb picker biology and ecology in nature and cancer to provide cross-disciplinary insights into this interesting, and, we argue, likely very common, mechanism of coexistence.īiodiversity, the presence of many phenotypes and species, is a ubiquitous feature of nature. Despite interest in tumor heterogeneity and how it promotes the coexistence of different cancer cell types, the effects of fluctuating resource availability have not been explored for cancer. Within tumors, nutrient availability, oxygen, and pH can fluctuate stochastically or periodically, with swings occurring over seconds to minutes to hours. Fluctuations among richer and poorer times also appear to be the norm in cancer ecosystems. In nature, richer and poorer times, with regular or stochastic appearances, are the norm and occur on many time scales. Here we focus on two phenotypes, “cream skimmers” and “crumb pickers,” the former having the advantage in richer times and the latter in less rich times. Since, coexistence based on fluctuating conditions has been explored under the guises of “grazers” and “diggers,” variance partitioning, relative non-linearity, “opportunists” and “gleaners,” and as the storage effect. These reflect trade-offs where one species benefits more than the other during good periods and suffers more (or does less well) than the other during less good periods, be the periods stochastic, unstable population dynamics, or seasonal. Such coexistence results from non-linearities or non-additivities in the way resource supply translates into fitness. Over 40 years ago, seminal papers by Armstrong and McGehee and by Levins showed that temporal fluctuations in resource availability could permit coexistence of two species on a single resource. 3Inspirata, Inc., Tampa, FL, United States.2Department of Integrated Mathematical Oncology, Moffitt Cancer Center, Tampa, FL, United States.1Ecology Center and Department of Biology, Utah State University, Logan, UT, United States. ![]()
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