Phenotypic plasticity's role in the origins and diversification of feeding strategies in spadefoot toad larvae

Phenotypic plasticity - the ability of one genotype to produce many phenotypes in response to environmental change - may play a critical role in allowing populations to endure environmental transitions. Moreover, selection on genetic variation underlying plastic phenotypes may modify and refine these traits such that they are adaptive in novel environments. Yet the prevalence of such genetic variation in natural populations, and the proximate mechanisms underlying its expression, remain relatively uncharacterized. My research sought to address this gap by assessing the role of environmentally-dependent phenotypes and their underlying genetic variation in the origins and diversification of feeding strategies among spadefoot toad larvae. While most spadefoot larvae feed on a range of diets, two lineages specialize on specific resources. Tadpoles of the genus Spea can develop as a carnivore morph that preys on, and is induced by fairy shrimp. In contrast, Sc. couchii, which cooccurs with Spea, specializes on detritus. Using a comparative approach, I determined that Sc. couchii have been excluded from the shrimp resource because of predation pressure imposed by Spea, and that Sc. couchii minimize this predation risk via behavioral plasticity. Furthermore, this dietary exclusion has been followed by evolutionary modification of Sc. couchii's behavioral, physiological and morphological responses to shrimp. Relaxed selection on traits that are no longer used - such as those involved with consuming shrimp in Sc. couchii - can result in the accumulation of neutral population genetic variation. When these populations encounter a new environment (or revisit an old one), such genetic variation may be expressed and is potentially adaptive. I found that feeding Sc. couchii shrimp amplifies the expression of genetic variation in a trait that is adaptive for consuming shrimp (as seen in Spea). Additionally, the hormone corticosterone, which is elevated in Sc. couchii fed the shrimp diet, can mediate the expression of this variation. In summary, ecological interactions can influence genetic variation underlying environmentally-dependent phenotypes and, by extension, phenotypes that are expressed and potentially adaptive when populations transition to novel environments. Furthermore, characterizing environmentally-dependent physiological processes may help us to better understand when and how such phenotypes are expressed

Adaptive maternal behavioral plasticity and developmental programming mitigate the transgenerational effects of temperature in dung beetles

Phenotypic plasticity allows organisms to cope with rapid environmental change. Yet exactly when during ontogeny plastic responses are elicited, whether plastic responses produced in one generation influence phenotypic variation and fitness in subsequent generations, and the role of plasticity in shaping population divergences, remains overall poorly understood. Here, we use the dung beetle Onthophagus taurus to assess plastic responses to temperature at several life stages bridging three generations and compare these responses across three recently diverged populations. We find that beetles reared at hotter temperatures grow less than those reared at mild temperatures, and that this attenuated growth has transgenerational consequences by reducing offspring size and survival in subsequent generations. However, we also find evidence that plasticity may mitigate these consequences in two ways: 1) mothers modify the temperature of their offspring's developmental environment via behavioral plasticity and 2) in one population, offspring exhibit accelerated growth when exposed to hot temperatures during very early development (‘developmental programming’). Lastly, our study reveals that offspring responses to temperature diverged among populations in fewer than 100 generations, possibly in response to range-specific changes in climatic or social conditions.Fil: Macagno, Anna L. M.. Indiana University; Estados UnidosFil: Zattara, Eduardo Enrique. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones en Biodiversidad y Medioambiente. Universidad Nacional del Comahue. Centro Regional Universidad Bariloche. Instituto de Investigaciones en Biodiversidad y Medioambiente; Argentina. Indiana University; Estados UnidosFil: Ezeakudo, Onye. Homestead High School; Estados UnidosFil: Moczek, Armin P.. Indiana University; Estados UnidosFil: Ledón Rettig, Cristina. Indiana University; Estados Unido

Concordance in hippocampal and fecal Nr3c1 methylation is moderated by maternal behavior in the mouse

Recent advances in genomic technologies now enable a reunion of molecular and evolutionary biology. Researchers investigating naturally living animal populations are thus increasingly able to capitalize upon genomic technologies to connect molecular findings with multiple levels of biological organization. Using this vertical approach in the laboratory, epigenetic gene regulation has emerged as an important mechanism integrating genotype and phenotype. To connect phenotype to population fitness, however, this same vertical approach must now be applied to naturally living populations. A major obstacle to studying epigenetics in noninvasive samples is tissue specificity of epigenetic marks. Here, using the mouse as a proof‐of‐principle model, we present the first known attempt to validate an epigenetic assay for use in noninvasive samples. Specifically, we compare DNA methylation of the NGFI‐A (nerve growth factor‐inducible protein A) binding site in the promoter of the glucocorticoid receptor ( Nr3c1 ) gene between central (hippocampal) and peripheral noninvasive (fecal) tissues in juvenile Balb/c mice that had received varying levels of postnatal maternal care. Our results indicate that while hippocampal DNA methylation profiles correspond to maternal behavior, fecal DNA methylation levels do not. Moreover, concordance in methylation levels between these tissues within individuals only emerges after accounting for the effects of postnatal maternal care. Thus, although these findings may be specific to the Nr3c1 gene, we urge caution when interpreting DNA methylation patterns from noninvasive tissues, and offer suggestions for further research in this field. A major obstacle to studying epigenetics in noninvasive samples is tissue specificity of epigenetic marks. Here, we compare DNA methylation of the NGFI‐A (nerve growth factor‐inducible protein A) binding site in the promoter of the glucocorticoid receptor ( Nr3c1 ) gene between central (hippocampal) and peripheral noninvasive (fecal) tissues in juvenile Balb/c mice that had received varying levels of postnatal maternal care. Our results indicate that concordance in methylation levels between these tissues within individuals only emerges after accounting for the effects of postnatal maternal care and that maternally induced variation in DNA methylation is limited to the brain.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/95656/1/ece3416.pd

Assaying Environmental Nickel Toxicity Using Model Nematodes

Although nickel exposure results in allergic reactions, respiratory conditions, and cancer in humans and rodents, the ramifications of excess nickel in the environment for animal and human health remain largely undescribed. Nickel and other cationic metals travel through waterways and bind to soils and sediments. To evaluate the potential toxic effects of nickel at environmental contaminant levels (8.9-7,600 µg Ni/g dry weight of sediment and 50-800 µg NiCl2/L of water), we conducted assays using two cosmopolitan nematodes, Caenorhabditis elegans and Pristionchus pacificus. We assayed the effects of both sediment-bound and aqueous nickel upon animal growth, developmental survival, lifespan, and fecundity. Uncontaminated sediments were collected from sites in the Midwestern United States and spiked with a range of nickel concentrations. We found that nickel-spiked sediment substantially impairs both survival from larval to adult stages and adult longevity in a concentration-dependent manner. Further, while aqueous nickel showed no adverse effects on either survivorship or longevity, we observed a significant decrease in fecundity, indicating that aqueous nickel could have a negative impact on nematode physiology. Intriguingly, C. elegans and P. pacificus exhibit similar, but not identical, responses to nickel exposure. Moreover, P. pacificus could be tested successfully in sediments inhospitable to C. elegans. Our results add to a growing body of literature documenting the impact of nickel on animal physiology, and suggest that environmental toxicological studies could gain an advantage by widening their repertoire of nematode species

Are There Synergistic or Antagonistic Effects of Multiple Maternally Derived Egg Components on Offspring Phenotype?

Eggs are ‘multivariate’ in that they contain multiple maternally-derived egg components (e.g. hormones, antibodies, mRNA, antioxidants) which are thought to influence offspring phenotype. However, most studies have focused on single egg components (most often yolk testosterone, or corticosterone), and on short-term effects. Here we simultaneously manipulated two egg components, maternally-derived antibodies (MAb) and yolk testosterone to assess potential synergistic or antagonistic effects on offspring phenotype from hatching to sexual maturity. We used lipopolysaccharide treatment to generate a secondary immune response in female zebra finches (Taeniopygia guttata), which produced clutches of eggs with high (LPS-treated) or low (control) MAb. We then used a split design manipulating yolk testosterone within clutches of high- and low-MAb eggs using in ovo egg injection. We investigated a) short-term effects of experimental manipulation of both egg components at 30 days post-hatching on chick growth and immune function at fledging, and b) long-term effects at sexual maturity (> 90 days post-hatching) on phenotypic quality of i/ males (sons) using standardise mating trials (courtship, song rate, etc); ii/ females (daughters) by measuring reproductive traits during breeding (egg size, clutch size etc), and iii/ cell-mediated and humoral immunity in both sexes

16S-raw-.001-abundance.representative.sequences

This fasta file includes 16S sequence data from different environmental samples. Within QIIME2, DADA2 was used to remove primer sequences from the reads, perform error correction, identify sequence variants, and remove chimeric sequences. Sequence variants were then classified by a naive Bayes classifier within QIIME2 using release of 128 of the Silva SSU database. An abundance filter was applied, and sequence variants that did not compose at least 0.1% of at least one library were removed from all libraries. The fasta file includes all variants that passed the abundance filter

ITS-dna-sequences

Following ITS sequencing, reads were demultiplexed using the 2017.10 release of QIIME2 requiring a barcode match. Because the forward and reverse reads do not overlap for this amplicon, DADA2 was used to trim forward and reverse reads to 200 and 100bp respectively. Cutadapt was used to trim primer sequences from the sequence variants identified by DADA2. Sequences that did not contain these primer sequences were discarded. VSEARCH was used to perform de novo chimera detection and removal. The remaining ITS sequence variants were clustered into operational taxonomic units (OTUs) at 97% similarity using Abundant OTU+. The software package ITSx was then used to filter non-ITS and non-fungal OTUs from our data set

Eco-Evo-Devo: Developmental Symbiosis And Developmental Plasticity As Evolutionary Agents

The integration of research from developmental biology and ecology into evolutionary theory has given rise to a relatively new field, ecological evolutionary developmental biology (Eco-Evo-Devo). This field integrates and organizes concepts such as developmental symbiosis, developmental plasticity, genetic accommodation, extragenic inheritance and niche construction. This Review highlights the roles that developmental symbiosis and developmental plasticity have in evolution. Developmental symbiosis can generate particular organs, can produce selectable genetic variation for the entire animal, can provide mechanisms for reproductive isolation, and may have facilitated evolutionary transitions. Developmental plasticity is crucial for generating novel phenotypes, facilitating evolutionary transitions and altered ecosystem dynamics, and promoting adaptive variation through genetic accommodation and niche construction. In emphasizing such non-genomic mechanisms of selectable and heritable variation, Eco-Evo-Devo presents a new layer of evolutionary synthesis