Sorted gene genealogies and species- specific nonsynonymous substitutions point to putative postmating prezygotic isolation genes in Allonemobius crickets

Citation: Noh, S., & Marshall, J. L. (2016). Sorted gene genealogies and species- specific nonsynonymous substitutions point to putative postmating prezygotic isolation genes in Allonemobius crickets. Peerj, 4, 29. doi:10.7717/peerj.1678In the Allonemobius socius complex of crickets reproductive isolation is primarily accomplished via postmating prezygotic barriers. We tested seven protein-coding genes expressed in the male ejaculate for patterns of evolution consistent with a putative role as postmating prezygotic isolation genes. Our recently diverged species generally lacked sequence variation. As a result, omega-based tests were only mildly successful. Some of our genes showed evidence of elevated omega values on the internal branches of gene trees. In a couple of genes, these internal branches coincided with both species branching events of the species tree, between A. fasciatus and the other two species, and between A. socius and A. sp. nov. Tex. In comparison, more successful approaches were those that took advantage of the varying degrees of lineage sorting and allele sharing among our young species. These approaches were particularly powerful within the contact zone. Among the genes we tested we found genes with genealogies that indicated relatively advanced degrees of lineage sorting across both allopatric and contact zone alleles. Within a contact zone between two members of the species complex, only a subset of genes maintained allelic segregation despite evidence of ongoing gene flow in other genes. The overlap in these analyses was arginine kinase (AK) and apolipoprotein A-1 binding protein (APBP). These genes represent two of the first examples of sperm maturation, capacitation, and motility proteins with fixed non-synonymous substitutions between species-specific alleles that may lead to postmating prezygotic isolation. Both genes express ejaculate proteins transferred to females during copulation and were previously identified through comparative proteomics. We discuss the potential function of these genes in the context of the specific postmating prezygotic isolation phenotype among, our species, namely conspecific sperm precedence and the superior ability of conspecific males to induce oviposition in females

The chemistry of sex games: Why do male crickets transfer large amounts of dopamine to females during copulation?

Dopamine is an important biological molecule that plays a critical role in how behaviors are “punished” or “rewarded”. And while dopamine has been studied with regard to a wide range of behaviors, including memory, diet and addiction, it has not been found previously to be transferred from one individual to another during copulation. However,the ejaculates of male ground crickets (Allonemobius socius) can contain up to 100pg of dopamine, which is roughly 10X the normal physiological dose required to modify behavior in insects. So, the question is, why are male crickets transferring so much dopamine to females during sex? There are several alternative hypotheses, derived from sexual selection and sexual conflict theory, which may explain the function of dopamine as an agent of sexual reward or punishment, respectively. Our preliminary data suggest that dopamine acts as a punishment, whereby the greater the amount of dopamine transferred to the female, the longer it takes for the female to re-mate. As a consequence, females receiving larger doses of dopamine are likely forced to store and utilize more of that male’s sperm relative to a female who receives smaller amounts of dopamine. This “punishment” effect is particularly strong when a female re-mates with a different male. While further experiments are needed to clarify the role of dopamine in the chemistry of cricket sex, our data suggest that sexual conflict over mating rates may be driving the evolution of dopamine usage as a sexual punishment in this system

Species Boundaries and Hybrid Zones of a Recently Diverged Species Complex

Speciation is the biological process of one species splitting into two or more new species, and is the driving force of biodiversity on Earth. When such new species are formed, there are three different ways in which their populations can be distributed relative to each other. They can be sympatric, where species boundaries overlap one another; parapatric, where species boundaries line up along each other’s edges; or allopatric, where the species boundaries do not come in contact with each other. In the Marshall Laboratory, we are interested both in how environmental variables like temperature and moisture influence species distributions (Camp and Marshall 2000; Jensen, Camp, and Marshall 2002; Marshall and Camp 2006; Camp, Huestis, and Marshall 2007) and how closely related species interact at the boundaries of their distributions (Howard et al 2003; Traylor et al. 2008). The combination of these two interests motivated this study. Specifically, we were interested in the Allonemobius socius complex of crickets, which is comprised of four closely related species (i.e., A. socius, A. fasciatus, A. sp. nov. Tex, and A. shalontaki) whose species boundaries are unresolved in the central United States. This complex of crickets has been a model in evolutionary biology, used to study speciation (Howard et al. 2002; Marshall, Arnold, and Howard 2002; Marshall et al. 2011; Marshall and DiRienzo 2012; Marshall 2013), hybrid zones (Howard et al. 2003; Traylor et al. 2008), genetics (Huestis and Marshall 2006a; Britch et al. 2007; Huestis and Marshall 2009; Huestis, Oppert, Marshall 2009; Marshall et al. 2009), behavior (Huestis and Marshall 2006b; Birge et al. 2010), and sexual conflict (Hayashi, Marshall, Gavrilets 2007; Marshall 2007; DiRienzo and Marshall 2013). Here, the goal of this research project was to assess the physical and ecological distribution of these species in the central United States and determine whether or not there are areas of sympatry. To accomplish this, we created eight transects over five states (Nebraska, Kansas, Missouri, Texas, and Arkansas), and collected 10-30 crickets every 100 km on those transects. Next, we genetically screened all individuals for two diagnostic allozyme loci (Mdh and Idh; Huestis and Marshall 2006; Huestis, Oppert, Marshall 2009) and several AFLP markers (Howard et al. 2002). We also conducted hybrid index analyses for locations where multiple species were collected. We found that species were patchily distributed along their boundaries and that the hybrid zone between A. socius and A. sp. nov. Tex (Marshall 2004; Traylor et al. 2008) extends well into Oklahoma. Moreover, there is evidence of a new species in Missouri and northern Arkansas. More research is needed to define the number and distribution of species in this rapidly evolving complex of crickets.Citation: NSF-REU Summer Program Symposium, 2012. Title: Species boundaries and hybrid zones of a recently diverged species complex. Desiree Harpel (undergraduate), presenter. Kansas State University. Manhattan, KS.Citation: Ecological Genomics Symposium, 2012. Title: Species boundaries and hybrid zones of a recently diverged species complex. Desiree Harpel (undergraduate), presenter. Kansas City, KS.Citation: University of Boston, Sean Mullen’s Research Group, 2013. Title: The identification of zones of secondary contact in a cricket hybrid zone. Desiree Harpel (undergraduate), Interview Seminar. Boston, MA.Citation: University of Kansas, EEB group, 2013. Title: The identification of zones of secondary contact in a cricket hybrid zone. Desiree Harpel (undergraduate), Interview Seminar. Lawrence, KS

What Types of Courses Best Prepare Students?

I wanted to do a study on how people learn best because I think it’s important for instruction to be effective for productive learning. A lot of professors or future teachers need to know what style of class will work best for their learners. I wanted to know if college students learn best in lecture style, studio style or lab style classes and I thought college students would learn best in studio. In my results, I found that most students liked lecture style classes but learned best from lab style classes. I hope to take the knowledge I gained from this research into my classroom in the future

What do Cats do All Day?

When we look at zoo animals, we only see them for a couple of minutes at most. We do not see how active they really are, nor do we get a good representation of their behavior (Szokalski et al 2012; Allen et al. 2015). Cats are usually seen as lazy, sleepy animals. However, what do zoo cats really do during the day? Following four separate visits of 70 minutes each, the results showed a correlation between social behavior/movement based on size of the animal. There is a clear difference in the level of activity and observable behaviors among these species of big cat. The data suggest that smaller cats, like the Bobcat may be better at showing the public a wider range of behaviors

Grooming as a Means to Cool Down

Many people believe that the only method of cooling down their horse is to walk them, and sometimes for long amounts of time depending on the work and length of work the horse was used for. Brushing a horse’s coat mimics a natural equine behavior (mutual grooming) between horses that can induce a horse to relax – and thus affect his heart rate and cause it to lower (EquiMed) quicker. There are even certain studies that show heart rate reduction when the withers and nearby areas were groomed, but no reduction when the shoulder and other areas of the horse was groomed (S. Normando). There is not a lot of research projects on this idea that heart rate could help cool down horses after a workout, which would in turn save some time for the horse’s caretaker. If a horse is groomed immediately following exertion, then their heart rate should decrease at a rate faster than if they were walked after the exerting exercise. I concluded that there is a faster decrease in heart rate of the horse following a few minutes of grooming. The results that were found here should help show and explain to horse owners that grooming is a good practice to exercise after a horse has exerted itself with work. This could be extremely beneficial to the racing industry, where the cool down process is extremely important but consumes large amounts of time

Freezing and Recovery Time of Red Flour Beetles

Body size plays a critical role in animal survival. In fact, Bergmann's Rule states that larger animals should be more successful in colder environments (McNab 1971), although this may not be the case for ectotherms like insects (see Mousseau 1997). The underlying mechanism for this relationship is that larger animals have lower surface to volume ratios, thus making freezing more difficult (Schmidt- Nielsen 1984). So we tested the hypothesis on Red Flour Beetles to see if it holds for very small organisms. We found that hypothesis is supported by the experiment

The Effects of Species Exposure on Chemical Communication Behavior in Beetles

The Tribolium castaneum genome sequence contains a large number of odorant receptor (Or) genes when compared to the olfactory genomes of other insects (Engsontia et al., 2007). Evolved populations of the red flour beetle differ in their ability to detect chemical senses (Boake & Wade, 1984). Red flour beetles have been noted to release compounds via glands on their femurs (Olsson et al., 2006). This study observes the effects of chemical communication on behavior in beetles by comparing the response of the red flour beetles to areas predisposed to the chemical communication of other species. The purpose of this research is to study the effects of chemical communication in beetles by comparing the behavior of beetles exposed to life with only members of their own species to life in a group setting exposed to other species. If members of the species, Tribolium castaneum, were exposed to living with other species of beetles, then these beetles would be more likely to be present in areas predisposed to the other species. When accounting for edge behavior tendencies in beetles, this study observed that 80% of the tested individuals from the single species environment visited the red flour beetle chemical communication patch, while only 50% of individuals exposed to the group of multiple species were found on the patch chemically marked by species of red flour beetles. Results of this study support the notion that living alongside other species likely influences chemical communication preferences in beetles