Evaluation of reproductive strategies in captive California yellowtail (Seriola dorsalis) using genetic parentage analyses

A good understanding of spawning dynamics of species in aquaculture is vital in order to maximize egg production and quality as well as efficient allocation of food and space resources. The breeding program of California yellowtail (CYT; Seriola dorsalis previously Seriola lalandi) at Hubbs-SeaWorld Research Institute (HSWRI) is set up such that up to 30 wild caught brood fish can broadcast spawn in a group setting, just as CYT reproduce in the wild. The population of brood fish were originally caught offshore from Southern California, and are maintained under ambient sea water and natural lighting conditions. The spawning season at HSWRI lasted from March to September during the 2013 and 2014 study period. Reproductive output from this population of cultured CYT was evaluated through microsatellite-based parentage analyses whereby the percent contribution of offspring was determined across all spawning events over two years. Methods were first tested to determine the minimum sample size required to accurately describe the parental contributions in this specific group spawning environment. To do this, five spawns were selected from the 2013 season based on spawn volume, which was presumed to represent a high number of female parents thus representing the most complex spawning dynamic. For these five spawning events, there were 19 brood fish present, representing all possible parents. Actual assignment of samples sizes between 47 and over 300 was assessed for each spawn. Except in one instance, the parental contribution from sample size of 47 CYT offspring analyzed per spawn, was not statistically significantly different than a sample size of over 300 offspring per spawn (average P-value = 0.65). Simulated subsampling via computational bootstrapping, and subsequent statistical analysis, indicated that a sample size of 30 offspring per spawn was adequate to accurately describe the parental contributions. Based on this information, a samples size of 47 was used so that samples from two spawns could be run on a single 96 well plate, including one negative control sample per spawn. This constitutes one of the first studies of sample size quality control for genetic parentage contribution for an aquaculture species. Offspring were then analyzed from every spawning event (N = 130) over two spawning seasons to characterize spawning events of CYT. Analyzing all spawns during multiple spawning seasons allowed for determination of individual contribution levels, spawn pairings, and analysis of female fecundity. The breeding population consisted of 19 brood fish in 2013, and 37 in 2014; both years were roughly 50: 50 male – female. Brood fish added to the population in 2014 were smaller in terms of mass and total lengths. Spawning events tended to have one female contribute (primary female), with relatively equal paternal contribution during both the spawning events and season, for a possible lottery polygyny (Nunney, 1993) spawning system. One female in particular contributed 40% of all offspring during the two years, spawning nearly every 5-6 days during the spawning seasons. The larger females (~21 kg) had an average batch fecundity of ~490,000 eggs per spawn, while smaller females (~8.4 kg) only spawned 35,000 eggs per spawn. Annual and batch spawning totals were correlated to female mass (P \u3c 0.0005). All smaller brood fish spawned fewer times in the season than larger brood fish. This work constitutes the first-ever study of reproductive strategy (lottery polygyny) and parental contribution for a carangid species at the individual-level over several spawning events

A Natural Experiment Testing the Role of Specialization in Speciation of Seed Beetles

Species diversity varies across different insect lineages. One possible explanation for this diversity is that more diverse lineages are driven by intricate coevolutionary relationships. Many phytophagous insects must overcome significant plant defenses, such as accumulation of toxins, by developing specific adaptations of their own. This \u27arms race\u27 often leads to specialization and subsequent speciation within many insect taxa. Seed beetles in particular impose an intense selective pressure on plants by directly attacking plant offspring, contributing to widespread specialization between seed beetle species and highly specific host plants. Thus, it is highly unusual to come across seed beetles that are considered relative generalists. However, the Great Plains seed beetle, Acanthoscelides fraterculus, has been reared from host plants in different genera. To determine whether A. fraterculus is a true generalist or is actually composed of many specialist populations/species, I collected beetles at the same site from hosts in the genera Astragalus, Oxytropis, and Glycyrrhiza. This was repeated across eight localities in Colorado. I compared populations of the seed beetle reared from each host phenotypically and genotypically to determine whether the population structure is largely defined by host plant choice or geographic locality. Results from this experiment will provide insights into the mechanisms driving coevolution between phytophagous insects, which can contribute to understanding large scale community structuring

Does Urbanization Promote Invasive Species?

The world population has increased seven-fold in the past 200 years alone. This boom in global population led to a massive increase in urbanization. Along with this movement of people came the movement of non-native species into these urbanized areas, both intentional (e.g. through agriculture) and not (e.g. as invasive species). This is concerning, as invasive species could have detrimental impacts both on the environment and on our agriculture and economy. Armored scale insects are invertebrate plant pests with over 2,000 described species, many of which are invasive in the USA. Because they are found nearly everywhere on woody plants, I used these as a study organism to test if there is an association between invasive species of armored scale insects and urbanized areas. I do so by comparing the ratio of invasive to native species abundance of armored scale insects on plant hosts in these environments. I used molecular systematic techniques, including DNA sequencing, to examine the population demographics in the two differing environments. The findings I present will be the first to explicitly examine armored scale abundances across urban and non-urban landscapes while controlling for the confounding effects of different host plant communities. These findings, in turn, give us insights into the causes and consequences of urbanization for the establishment of invasive species

How Extreme is Specialization in Seed-Feeding Beetles when their Hosts are Poisonous?

The paradigm of insect-plant research is that coevolutionary dynamics select for specialization in the interaction. The purpose of this study is to follow a population genomic method to dissect the host plant specificity of seed beetles (Acanthoscelides) on multiple varieties of the toxic legume Astragalus lentiginosus. Acanthoscelides impose direct fitness consequences on A. lentiginosus through consuming the plants\u27 offspring (seeds), thus being a primary driver for high diversification and likely coevolution. I propose that through the seed beetles\u27 imposition of antagonistic selection pressures and the resulting diversity of A. lentiginosus, populations of Acanthoscelides will have genetic association with the particular variety of host plant that they were collected from. I have examined the population genetic structure of 115 individuals from 15 varying populations found on several A. lentiginosus varieties in CA, AZ, UT, and NV. I will present the results of population genetic analyses based on molecular markers in order to assess whether there is evidence of host-associated specialization in the beetle. This study creates the opportunity to assess population dynamics of seed beetles, which impose great losses in legume crop yield each year