Biology subjects

Toll, K.

Publications and source records attributed to Toll, K..

3 recordsLinked to original sources

bioRxiv2022

The genetic basis of traits associated with the evolution of serpentine endemism in monkeyflowers

The floras on chemically and physically challenging soils, such as gypsum, shale, and serpentine, are characterized by narrowly endemic species. These edaphic endemics often have widespread close relatives that are not restricted to specific soil types. The evolution of edaphic endemics may be facilitated or constrained by genetic correlations among traits contributing to adaptation and reproductive isolation across soil boundaries. The yellow monkeyflowers in the Mimulus guttatus species complex are an ideal system in which to examine these evolutionary patterns. To determine the genetic basis of adaptive and prezygotic isolating traits, we performed genetic mapping experiments with F2 hybrids derived from a cross between a serpentine endemic, M. nudatus, and its close relative M. guttatus. Plants occurring on serpentine soils have repeatedly evolved short statures and small leaves, suggesting that these traits are adaptive, and M. nudatus shows all these characteristics compared to M. guttatus. Previous research demonstrated that flower size and life history differences between these species contribute to prezygotic reproductive isolation between them. Few large effect and many small effect loci contribute to interspecific divergence in life history, floral and leaf traits, and a history of directional selection contributed to trait divergence. Loci contributing to adaptive traits and prezygotic reproductive isolation overlap, and their allelic effects are largely in the direction of species divergence. These loci contain promising candidate genes regulating flowering time and plant organ size. Together our results suggest that genetic correlations among traits facilitated the evolution of edaphic adaptation and speciation in this species pair.

evolutionary biology↗

bioRxiv2022

Abiotic conditions alter effectiveness of a key seed defensive trait against granivores similarly across many plant species

O_LIEnvironmental conditions alter the function of many plant traits that drive species interactions, producing context-dependency in the outcomes of those interactions. Seed mucilage is a common, convergently-evolved trait found in thousands of plant species. When wetted, the seed coat swells into a viscid mass; when dried, the mucilage strands strongly cement the seed to whatever it is in contact with. C_LIO_LIThis binding to the ground has been previously shown to protect seeds from granivory. Previous research found both that mucilage volume - and the correlated attachment strength - are higher in species from hot, dry, areas suggesting an environmental component of this traits function. C_LIO_LIHere we (1) quantified the effect of temperature on attachment across many species in a lab setting, (2) tested the potential mechanism behind this correlation by accelerating desiccation speed without changing temperature, and (3) tested whether these relationships introduce context dependency of the defensive function of mucilage in the field, using field trials with harvester ants. C_LIO_LIWe found that (1) increasing temperature during mucilage drying strongly reduced the force needed to dislodge seeds for most species, (2) drying time was likely the driving mechanism behind the loss of attachment strength at higher temperatures, not temperature per se, (3) seeds attached to substrate during higher temperatures or under accelerated drying conditions were far more susceptible to granivory. C_LIO_LI Synthesis These results show not only the mechanism behind an abiotic modification of a functional trait of seeds, but that this change majorly alters a key interaction contributing to seed survival. These results add to a small, but growing, literature on the importance of seed mucilage in seed survival and demonstrate strong and largely predictable context-dependency in this traits defensive function. C_LI

ecology↗

bioRxiv2021

Frequency-dependent hybridization contributes to habitat segregation in monkeyflowers

Spatial segregation of closely related species is usually attributed to differences in stress tolerance and competitive ability. For both animals and plants, reproductive interactions between close relatives can impose a fitness cost that is more detrimental to the rarer species. Frequencydependent mating interactions may thus prevent the establishment of immigrants within heterospecific populations, maintaining spatial segregation of species. Despite strong spatial segregation in natural populations, two sympatric California monkeyflowers (Mimulus nudatus and M. guttatus) survive and reproduce in the others habitat when transplanted reciprocally. We hypothesized that a frequency-dependent mating disadvantage maintains spatial segregation of these monkeyflowers during natural immigration. To evaluate this hypothesis, we performed two field experiments. First, we experimentally added immigrants in varying numbers to sites dominated by heterospecifics. Second, we reciprocally transplanted arrays of varying resident and immigrant frequencies. Immigrant seed viability decreased with conspecific rarity for M. guttatus, but not M. nudatus. We observed immigrant minority disadvantage for both species, but driven by different factors- frequency-dependent hybridization for M. guttatus, and competition for resources and/or pollinators for M. nudatus. Overall, our results suggest a major role for reproductive interference in spatial segregation that should be evaluated along with stress tolerance and competitive ability.

ecology↗