Vegetation Prior to and During Onset of East Antarctic Glaciation: High Resolution Palynological Insights from Sabrina Coast, East Antarctica

The Aurora Subglacial Basin (ASB) contains an estimated 3.5 m of global sea-level equivalent ice volume and is primarily drained by the Totten Glacier system, which terminates at the Sabrina Coast, East Antarctica. Thinning and retreating of the Totten Glacier indicate that this region is highly susceptible to oceanographic and atmospheric warming. The paleoclimate reconstruction of these changes, conducted in the context of this MS thesis, will improve understanding of East Antarctic Ice Sheet (EAIS) dynamics in this sensitive system. A recent study used seismic and sediment core data to document a dynamic early evolution of the EAIS in the ASB, suggesting that this large ice sheet may not be as stable as previously thought. Our study presents new high-resolution palynological data from NBP 14-02 jumbo piston cores (JPC) JPC-54 and JPC-55, which enable reconstruction of regional vegetation and environments during EAIS development. The newly described Sabrina Flora is dominated by angiosperms, with Gambierina (G.) spp. often exceeding 40% of the assemblage. Diverse Proteaceae, Battenipollis spp., Forcipites spp., Nothofagidites spp., fern and conifer palynomorphs are also notable in the assemblage. Because of pristine preservation and the frequent occurrence of Gambierina spp. clusters, the majority of the Sabrina Flora assemblage is interpreted as being penecontemporaneous with sedimentation. Biostratigraphic results indicate JPC-55 and JPC-54 are latest Paleocene and early-mid Eocene sediments (respectively) with likely contributions from reworked mid-Cretaceous marine deposits. Biomarker evidence of plant wax n-alkanoic acid yields average ẟ13C30 values of -30.2±0.5‰ (JPC-54 only), consistent with open canopy woodland or shrubby tundra. ẟD30 values were stable across JPC-54 and 55 with a mean -215±4.5‰. A fractionation of ~-100‰ indicates ẟDprecip of -128‰, slightly more positive than coastal snow in the same region today, suggesting sourcing of plant biomarkers from close to the coast. Integration of biomarker and palynological results suggests the abundance of Gambierina, Battenipollis and Proteaceae could be consistent with a drier, more open type of coastal vegetation rather than the closed rainforest vegetation often envisaged for Paleocene-Eocene Antarctica. Therefore, the Sabrina Flora provides new insight to paleoenvironment and paleoclimate reconstructions during onset of glaciation in East Antarctica

Last and corresponding authorship practices in ecology

Authorship is intended to convey information regarding credit and responsibility for manuscripts. However, while there is general agreement within ecology that the first author is the person who contributed the most to a particular project, there is less agreement regarding whether being last author is a position of significance and regarding what is indicated by someone being the corresponding author on a manuscript. Using an analysis of papers published in American Naturalist, Ecology, Evolution, and Oikos, I found that: (1) the number of authors on papers is increasing over time; (2) the proportion of first authors as corresponding author has increased over time, as has the proportion of last authors as corresponding author; (3) 84% of papers published in 2016 had the first author as corresponding author; and (4) geographic regions differed in the likelihood of having the first (or last) author as corresponding author. I also carried out an online survey to better understand views on last and corresponding authorship. This survey revealed that most ecologists view the last author as the “senior” author on a paper (i.e., the person who runs the research group in which most of the work was carried out), and most ecologists view the corresponding author as the person taking full responsibility for a paper. However, there was substantial variation in views on authorship, especially corresponding authorship. Given these results, I suggest that discussions of authorship have as their starting point that the first author will be corresponding author and the senior author will be last author. I also suggest ways of deciding author order in cases where two senior authors contributed equally.There is variation in views on corresponding and last authorship in ecology, but most ecologists view the last author position as one of emphasis and view the corresponding author as taking full responsibility for a paper. The field would benefit from greater consensus on what is signified by corresponding and last authorship.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/140027/1/ece33435.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/140027/2/ece33435_am.pd

Local adaptation of a parasite to solar radiation impacts disease transmission potential, spore yield, and host fecundity*

Environmentally transmitted parasites spend time in the abiotic environment, where they are subjected to a variety of stressors. Learning how they face this challenge is essential if we are to understand how host–parasite interactions may vary across environmental gradients. We used a zooplankton–bacteria host–parasite system where availability of sunlight (solar radiation) influences disease dynamics to look for evidence of parasite local adaptation to sunlight exposure. We also examined how variation in sunlight tolerance among parasite strains impacted host reproduction. Parasite strains collected from clearer lakes (with greater sunlight penetration) were most tolerant of the negative impacts of sunlight exposure, suggesting local adaptation to sunlight conditions. This adaptation came with both a cost and a benefit for parasites: parasite strains from clearer lakes produced relatively fewer transmission stages (spores) but these strains were more infective. After experimental sunlight exposure, the most sunlight‐tolerant parasite strains reduced host fecundity just as much as spores that were never exposed to sunlight. Sunlight availability varies greatly among lakes around the world. Our results suggest that the selective pressure sunlight exposure exerts on parasites may impact both parasite and host fitness, potentially driving variation in disease epidemics and host population dynamics across sunlight availability gradients.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/156433/3/evo13940.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/156433/2/evo13940-sup-0001-SuppMat.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/156433/1/evo13940_am.pd

A colorful killer: Daphnia infected with the bacterium Spirobacillus cienkowskii exhibit unexpected color variation

Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/148232/1/ecy2562-sup-0001-AppendixS1.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/148232/2/ecy2562_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/148232/3/ecy2562.pd

Daphnia predation on the amphibian chytrid fungus and its impacts on disease risk in tadpoles

Direct predation upon parasites has the potential to reduce infection in host populations. For example, the fungal parasite of amphibians, B atrachochytrium dendrobatidis ( B d), is commonly transmitted through a free‐swimming zoospore stage that may be vulnerable to predation. Potential predators of B d include freshwater zooplankton that graze on organisms in the water column. We tested the ability of two species of freshwater crustacean ( D aphnia magna and D . dentifera ) to consume B d and to reduce B d density in water and infection in tadpoles. In a series of laboratory experiments, we allowed D aphnia to graze in water containing B d while manipulating D aphnia densities, D aphnia species identity, grazing periods and concentrations of suspended algae ( A nkistrodesmus falcatus ). We then exposed tadpoles to the grazed water. We found that high densities of D . magna reduced the amount of Bd detected in water, leading to a reduction in the proportion of tadpoles that became infected. Daphnia dentifera , a smaller species of D aphnia , also reduced B d in water samples, but did not have an effect on tadpole infection. We also found that algae affected B d in complex ways. When D aphnia were absent, less B d was detected in water and tadpole samples when concentrations of algae were higher, indicating a direct negative effect of algae on B d. When D aphnia were present, however, the amount of B d detected in water samples showed the opposite trend, with less B d when densities of algae were lower. Our results indicate that D aphnia can reduce B d levels in water and infection in tadpoles, but these effects vary with species, algal concentration, and D aphnia density. Therefore, the ability of predators to consume parasites and reduce infection is likely to vary depending on ecological context. We tested the ability of two species of freshwater crustacean ( Daphnia magna and D. dentifera ) to consume zoospores of the amphibian parasite, Batrachochytrium dendrobatidis (Bd), and to reduce parasite density in water and infection in tadpoles. In a series of laboratory experiments, we allowed Daphnia to graze in water containing Bd, then exposed tadpoles to the grazed water. Our results show that Daphnia can reduce Bd levels in water and infection in tadpoles, but these effects vary with species, algal concentration and Daphnia density.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/100311/1/ece3777.pd

Gender diversity of editorial boards and gender differences in the peer review process at six journals of ecology and evolution

Despite substantial progress for women in science, women remain underrepresented in many aspects of the scholarly publication process. We examined how the gender diversity of editors and reviewers changed over time for six journals in ecology and evolution (2003–2015 for four journals, 2007–2015 or 2009–2015 for the other two), and how several aspects of the peer review process differed between female and male editors and reviewers. We found that for five of the six journals, women were either absent or very poorly represented as handling editors at the beginning of our dataset. The representation of women increased gradually and consistently, with women making up 29% of the handling editors (averaged across journals) in 2015, similar to the representation of women as last authors on ecology papers (23% in 2015) but lower than the proportion of women among all authors (31%) and among members of the societies that own the journals (37%–40%). The proportion of women among reviewers has also gradually but consistently increased over time, reaching 27% by 2015. Female editors invited more female reviewers than did male editors, and this difference increased with age of the editor. Men and women who were invited to review did not differ in whether they responded to the review invitation, but, of those that responded, women were slightly more likely to agree to review. In contrast, women were less likely than men to accept invitations to serve on journal editorial boards. Our analyses indicate that there has been progress in the representation of women as reviewers and editors in ecology and evolutionary biology, but women are still underrepresented among the gatekeepers of scholarly publishing relative to their representation among researchers.We examined how the gender diversity of editors and reviewers changed over time for six journals in ecology and evolution, and how several aspects of the peer review process differed between female and male editors and reviewers. Our analyses indicate that there has been progress in the representation of women as reviewers and editors in ecology and evolutionary biology, but women are still underrepresented among the gatekeepers of scholarly publishing relative to their representation among researchers.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/153720/1/ece35794_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/153720/2/ece35794.pd

Resources, key traits and the size of fungal epidemics in Daphnia populations

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/111939/1/jane12363.pd

Parasite transmission in a natural multihost-multiparasite community

Understanding the transmission and dynamics of infectious diseases in natural communities requires understanding the extent to which the ecology, evolution and epidemiology of those diseases are shaped by alternative hosts. We performed laboratory experiments to test how parasite spillover affected traits associated with transmission in two co-occurring parasites: the bacterium Pasteuria ramosa and the fungus Metschnikowia bicuspidata. Both parasites were capable of transmission from the reservoir host (Daphnia dentifera) to the spillover host (Ceriodaphnia dubia), but this occurred at a much higher rate for the fungus than the bacterium. We quantified transmission potential by combining information on parasite transmission and growth rate, and used this to compare parasite fitness in the two host species. For both parasites, transmission potential was lower in the spillover host. For the bacterium, virulence was higher in the spillover host. Transmission back to the original host was high for both parasites, with spillover influencing transmission rate of the fungus but not the bacterium. Thus, whilst inferior, the spillover host is not a dead-end for either parasite. Overall, our results demonstrate that the presence of multiple hosts in a community can have important consequences for disease transmission and host and parasite fitness

Temperature Drives Epidemics in a Zooplankton-Fungus Disease System: A Trait-Driven Approach Points to Transmission via Host Foraging

Climatic warming will likely have idiosyncratic impacts on infectious diseases, causing some to increase while others decrease or shift geographically. A mechanistic framework could better predict these different temperature-disease outcomes. However, such a framework remains challenging to develop, due to the nonlinear and (sometimes) opposing thermal responses of different host and parasite traits and due to the difficulty of validating model predictions with observations and experiments. We address these challenges in a zooplanktonfungus (Daphnia dentifera–Metschnikowia bicuspidata) system. We test the hypothesis that warmer temperatures promote disease spread and produce larger epidemics. In lakes, epidemics that start earlier and warmer in autumn grow much larger. In a mesocosm experiment, warmer temperatures produced larger epidemics. A mechanistic model parameterized with trait assays revealed that this pattern arose primarily from the temperature dependence of transmission rate (b), governed by the increasing foraging (and, hence, parasite exposure) rate of hosts ( f ). In the trait assays, parasite production seemed sufficiently responsive to shape epidemics as well; however, this trait proved too thermally insensitive in the mesocosm experiment and lake survey to matter much. Thus, in warmer environments, increased foraging of hosts raised transmission rate, yielding bigger epidemics through a potentially general, exposure-based mechanism for ectotherms. This mechanistic approach highlights how a trait-based framework will enhance predictive insight into responses of infectious disease to a warmer world

Pliocene Diatom Biomarkers in Sabrina Coast. EAIS Continental Marginal Dynamics

PNRA Tytan project, supported by the National Institute of Oceanography and Applied Geophysics (OGS), focused on the advances and retreats dynamics of the ice sheet and on variations in the glacial regime. Unit 2 focused on Diatom biomarkers and assemblages analysis on sediments of core PC03, collected during the IN2017-V01 cruise on the eastern flank of the Minang-a (or Whale) submarine Canyon. The project aims at reconstructing the depositional environment of the continental margin off the Totten Glacier and diatom data remained a key tools to constrain past ice-sheet dynamics and to forecasting future behaviour in a warming world. Preliminary dataset from diatom biostratigraphic tools allows to refer the base of the core to Pliocene while the upper part of the core records more modern EAIS dynamics, indicative of minor sedimentary evolution steps of the continental margin. Diatom assemblage analyses highlight Eocene-Oligocene reworked material and freshwater diatom inputs in Pliocene sequence, strengthening the debate about ice-sheet and paleoceanographic models, WAIS cyclic collapse and suspected Pliocene EAIS retreat into major subglacial Antarctic basins