DOI: 10.5061/dryad.kwh70rzjq
title: Differences in the fitness effects of traded resources shape traits and persistence in multi-mutualist communities

description: Mutualistic interactions, where species reciprocally benefit from each
 other, are crucial for ecosystem stability and biodiversity. These
 interactions often involve species that experience different fitness
 effects for the traded resources or services. Because mutualisms rely on
 positive feedback between partners, such asymmetries can strongly
 influence evolutionary outcomes. Differences in fitness effects create
 divergent selective pressures, shaping trait evolution and determining the
 persistence of mutualisms. The strength of these effects can also vary
 depending on the availability of traded resources from other sources.
 Despite their importance, the evolutionary role of fitness asymmetries in
 mutualism has received little attention, beyond recognizing that some
 species may be more dependent on their partners than others. This study
 investigates how asymmetry in the fitness effects of a traded resource
 influences the persistence and phenotypic trait evolution of species in
 multi-mutualist guilds. To test this, we constructed synthetic
 multi-mutualist communities by combining reproductively isolated and
 genetically modified strains of Saccharomyces cerevisiae that engage in a
 nutritional mutualism by trading adenine and lysine. One guild of four
 strains cannot produce lysine but overproduces adenine while the other
 guild cannot produce adenine but overproduces lysine. Lysine overproducers
 survive periods of low adenine better than adenine overproducers survive
 low lysine. Over a four-week evolution experiment we observed that strain
 persistence was strongly influenced by the availability of external
 resources. Communities in media containing traded resources supported the
 survival of all strains, whereas obligate conditions led to a significant
 extinction, especially for adenine overproducers. We observed distinct
 evolutionary trajectories of traits under obligate versus supplemented
 conditions. Phenotypic assays revealed that costs and benefits evolved
 differently depending on the essentiality of the traded resource and
 nutrient supplementation. These results demonstrate that asymmetries in
 the fitness effects of traded resources can influence evolutionary
 outcomes, species persistence, and community stability in multi-mutualist
 communities.
description: # Differences in the fitness effects of traded resources shape traits and
 persistence in multi-mutualist communities Dataset DOI:
 [10.5061/dryad.kwh70rzjq](https://doi.org/10.5061/dryad.kwh70rzjq) ##
 Description of the data and file structure ### Files and variables ####
 File: Yeast_MMC_evolution_data.xlsx **Description:** Synthetic
 multi-mutualist communities were constructed by combining reproductively
 isolated and genetically modified strains of *Saccharomyces* *cerevisiae*
 that engage in a nutritional mutualism by trading adenine (AdeOP) and
 lysine (LysOP). Mutualistic strain persistence and key traits associated
 with the production of traded resources, resource use, and population
 growth were tested after four weeks of evolution.  There are four
 worksheets: **1) Proportion_persistence** **Variables** * Week- Each value
 corresponds to the week in which strain persistence was tested. * Media-
 Strains evolved in two environments; Obligate=no external resources; High=
 external resources present. * Strain_id- Strain member identified by a
 strain number * OP_type- Overproducer strain, AdeOP or LysOP * N-
 Indicates the number of communities strain was absent from in that week. *
 Y- Indicates the number of communities strain was present in that week. *
 sample_n- starting total number of communities containing the respective
 strain * Prop_pers- Proportion of persistence of the strain **2)
 Retained_strains_in_communities** **Variables** * Media- Strains evolved
 in two environments; Obligate=no external resources; High= external
 resources present. * Number- Indicates how many strains were present
 within a given guild at that time point, out of a total of four possible
 members. * OP_type- type of overproducing strain, AdeOP overproduces
 adenine, LysOP overproduces lysine * Persisted- Percentage of persistence
 of the strain **3) AdeOP_phenotyping and 4) LysOP_phenotyping**
 **Variables** * Deepwell- 48-well plate used for the experiment * Person-
 Who performed the experiment. A: Anne E. Curé; R: Renuka Agarwal *
 Community- combinations of 4x4 AdeOPs and LysOPs * Media-Strains evolved
 in two environments; Obligate=no external resources; High= external
 resources present * Strain_id- Strain member identified by a strain number
 * t0_prop- Proportion of strain persisted after 0 hrs of starvation *
 t48_prop- Proportion of strain persisted after 48 hrs of starvation *
 t72_prop- Proportion of strain persisted after 72 hrs of starvation *
 t96_prop- Proportion of strain persisted after 96 hrs of starvation *
 t120_prop- Proportion of strain persisted after 120 hrs of starvation *
 t24_real_OD- Optical density at 24 hrs; Resource use efficiency *
 growth_rate- ((LN(OD @ 6hrs/OD @ 4hrs))/2 * real_OP_OD- Optical density of
 overproducing strain * real_test_OD- Optical density of test strain *
 OD_corrected- real_test_OD/real_OP_OD NA- missing data code