Behavioral and genomic consequences of evolution under skewed sex ratios

113 pagesIn this dissertation I combine game theoretic modeling with experimental evolution and next-generation sequencing to address the causes and consequences of male and female sexual interactions. In chapter 1, I use tug-of-war theory to model the evolution of male and female sex roles as a function of anisogamy and sex ratio, and show that individuals can diverge in how they allocate their reproductive effort based on either of these parameters. The model incorporates both within-sex competition and between-sex cooperation to demonstrate that sexual interactions underlie the evolution of sexually dimorphic behaviors. In chapter 2, I perform experimental evolution in the laboratory using a nematode with a short generation time, Caenorhabditis remanei, and test an extension of the hypothesis that disrupting male-female interactions has cascading effects on reproductive behavior and gamete investment. By systematically altering the adult sex ratio of replicate populations over 50 generations, I show that males and females increase their mating effort when exposed to a population with an excess of males, but find no effects on their sperm and egg sizes. Chapter 3 extends this experiment by applying a genomic lens to this organism and exploring the consequences of a skewed sex ratio on populations, along with the potential for repeatable evolution in replicate populations faced with identical environmental conditions. I show that populations with a male-biased sex ratio tend towards higher genomic divergence compared to female-biased populations, and that parallel evolution can arise across experimental populations regardless of sex ratio, with implications for the predictability of evolutionary trajectories at short evolutionary timescales. Furthermore, I identify loci that change in allele frequency in opposite directions in male-biased and female-biased populations and are implicated in male mating behavior, indicating possible genes under sexual conflict in this system

Compensatory Responses to Copulatory Organ Damage in the Western Black Widow

Experimental alterations of morphological traits during development can reveal life history tactics and resource allocation patterns. I examined effects of amputation of a structure directly involved with mating compared to one that is less associated with fitness. I amputated one of the paired external copulatory organs (palps) of juvenile male black widow spiders Latrodectus hesperus), and compared changes in life history traits and fitness to males with amputated legs and controls. I show that palps are more likely to be regenerated than legs, smaller juveniles are more likely to regenerate, and mating success is adversely affected in all adults that suffered early amputation. The pre-existing relationship between juvenile size and development was a critical determinant of regeneration, however no life history costs of regeneration were evident. I conclude that plasticity in life history facilitates regeneration, and that this may mask trade-offs involved in compensatory effects at the population level.MAS

Subtle pedipalp dimorphism: a reliable method for sexing juvenile spiders

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Juvenile Experience with Male Cues Triggers Cryptic Choice Mechanisms in Adult Female Redback Spiders

Female choice may be linked to population density if the expected encounter rates with potential mates affects choosiness (the energy and risk engaged to express mate preferences). Choosiness should covary with male availability, which could be assessed using the social cues available during development. We tested whether the exposure of juvenile females to cues of male density affected the mechanisms of choosiness of adult Latrodectus hasselti spiders in two experiments simulating natural contexts. The juvenile females were exposed to (1) volatile chemicals from two densities of adult males (airborne cues), and (2) tactile, vibrational and chemical cues from adult males or other females (cohabitation cues). As adults, the females mated readily, regardless of the treatment, but there was strong evidence for post-copulatory mechanisms of choosiness in females exposed to cues of high male availability. These included abbreviated matings (in both experiments), cannibalism of the males before the mating was complete (cohabitation), and, remarkably, a reduction in the successful placement of internal sperm plugs (cohabitation). These shifts decrease the likelihood that the first mate would monopolize paternity if the female chose to mate again. We conclude that female choosiness may impose a strong selection on males despite the high mating rates, and these effects can hinge on the cues of male availability detected by juveniles

Note types and coding in Parid vocalizations: The chick-a-dee call of the boreal chickadee (Poecile hudsonicus)

An important first step in characterizing a vocalization is to classify, describe, and measure the elements of that vocalization. Here, this methodology is employed to study the chick-a-dee call of the boreal chickadee (Poecile hudsonicus). The note types (A, B, C, D, and D h ) in a sample of boreal chickadee calls are identified and described, spectral and temporal features of each note type are analyzed, and production phenomena in each note type are identified and quantified. Acoustic variability is compared across note types and individuals to determine potential features used for note-type and individual discrimination. Frequency measures appear to be the most useful features for identifying note types and individuals, though total duration may also be useful. Call syntax reveals that boreal chick-a-dee calls follow a general rule of note-type order, namely A-B-C-D h -D, and that any note type in this sequence may be repeated or omitted. This work provides a thorough description of the boreal chickadee chick-a-dee call and will serve as a foundation for future studies aimed at elucidating this call's functional significance within this species, as well as for studies comparing chick-adee calls across Poecile species

Note types and coding in Parid vocalizations : the chick-a-dee call of the boreal chickadee (Poecile hudsonicus).

International audienceAn important first step in characterizing a vocalization is to classify, describe, and measure the elements of that vocalization. Here, this methodology is employed to study the chick-a-dee call of the boreal chickadee (Poecile hudsonicus). The note types (A, B, C, D, and D(h)) in a sample of boreal chickadee calls are identified and described, spectral and temporal features of each note type are analyzed, and production phenomena in each note type are identified and quantified. Acoustic variability is compared across note types and individuals to determine potential features used for note-type and individual discrimination. Frequency measures appear to be the most useful features for identifying note types and individuals, though total duration may also be useful. Call syntax reveals that boreal chick-a-dee calls follow a general rule of note-type order, namely A-B-C-D(h)-D, and that any note type in this sequence may be repeated or omitted. This work provides a thorough description of the boreal chickadee chick-a-dee call and will serve as a foundation for future studies aimed at elucidating this call's functional significance within this species, as well as for studies comparing chick-a-dee calls across Poecile species

A megastudy of text-based nudges encouraging patients to get vaccinated at an upcoming doctor's appointment

Many Americans fail to get life-saving vaccines each year, and the availability of a vaccine for COVID-19 makes the challenge of encouraging vaccination more urgent than ever. We present a large field experiment (N = 47,306) testing 19 nudges delivered to patients via text message and designed to boost adoption of the influenza vaccine. Our findings suggest that text messages sent prior to a primary care visit can boost vaccination rates by an average of 5%. Overall, interventions performed better when they were 1) framed as reminders to get flu shots that were already reserved for the patient and 2) congruent with the sort of communications patients expected to receive from their healthcare provider (i.e., not surprising, casual, or interactive). The best-performing intervention in our study reminded patients twice to get their flu shot at their upcoming doctor's appointment and indicated it was reserved for them. This successful script could be used as a template for campaigns to encourage the adoption of life-saving vaccines, including against COVID-19.Open access articleThis 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]