Biology subjects

Caruso, C. M.

Publications and source records attributed to Caruso, C. M..

2 recordsLinked to original sources

bioRxiv2026

Extended floral longevity does not increase seed production under experimental pollinator decline

Premise of researchIn plant species that depend on pollinators to produce seeds, declines in pollinator populations should strengthen natural selection for floral traits that increase outcross pollen receipt by increasing the probability of pollinator visitation. One such trait is floral longevity, the amount of time that a flower is open and functional. If flowers that are open longer have a higher probability of pollinator visitation and this pollination benefit outweighs the resource cost of maintaining floral tissue, then pollinator decline should strengthen selection for extended floral longevity. MethodologyTo test whether pollinator decline could strengthen selection for extended longevity, we studied the pollinator-dependent species Lobelia siphilitica. We exposed L. siphilitica plants to either an ambient open-pollination treatment or a reduced open-pollination treatment that simulates pollinator decline. Within each pollination treatment, we measured floral longevity and seeds per fruit and used these data to estimate directional selection on longevity. This experiment was repeated twice. Pivotal resultsIn one experiment, there was significant selection within both ambient and reduced pollination treatments for shortened (rather than extended) floral longevity. In the other experiment, selection on floral longevity within both ambient and reduced pollination treatments was not significantly different from zero. ConclusionsWe found no evidence of selection for extended floral longevity, regardless of the pollination environment. These results suggest that pollinator decline will not strengthen selection for extended longevity and thus that pollinator-dependent species such as L. siphilitica may not respond to pollinator decline by evolving extended floral longevity.

evolutionary biology↗

bioRxiv2021

Defense by duplication: The relation between phenotypic glyphosate resistance andEPSPS gene copy number variation in Amaranthus palmeri

Gene copy number variation (CNV) has been increasingly associated with organismal responses to environmental stress, but we know little about the quantitative relation between CNV and phenotypic variation. In this study we quantify variation in EPSPS (5-enolpyruvylshikimate-3-phosphate synthase) copy number using digital drop PCR and variation in phenotypic glyphosate resistance in 22 populations of Amaranthus palmeri (Palmer Amaranth), a range-expanding agricultural weed. Overall, we detected a significant positive relation between population mean copy number and mean resistance. The majority of populations exhibited high glyphosate resistance, yet maintained low-resistance individuals resulting in bimodality in many populations. We investigated linear and threshold models for the relation between copy number and resistance, and found evidence for a threshold of ~15 EPSPS copies: there was a steep increase in resistance before the threshold, followed by a much shallower slope. Moreover, as copy number increases, the range of variation in resistance decreases. This suggests a working hypothesis that as EPSPS copies and dosage increases, negative epistatic interactions may be compensated. We detected a quadratic relation between mean resistance and variation (s.d.) in resistance, consistent with the prediction that as phenotypic resistance increases in populations, stabilizing selection decreases variation in the trait. Finally, patterns of variation across the landscape are consistent with less variation among populations in mean copy number / resistance in Georgia where glyphosate resistance was first detected, and wider variation among populations in resistance and copy number in a more northern state where resistance evolution may be at a younger evolutionary state.

evolutionary biology↗