Susan Mazer - Academia.edu (original) (raw)

Papers by Susan Mazer

Frontiers in Plant Science, 2020

Ecosphere, 2016

Phenology is an integrative science that comprises the study of recurring biological activities o... more Phenology is an integrative science that comprises the study of recurring biological activities or events. In an era of rapidly changing climate, the relationship between the timing of those events and environmental cues such as temperature, snowmelt, water availability, or day length are of particular interest. This article provides an overview of the observer‐based plant phenology sampling conducted by the U.S. National Ecological Observatory Network (NEON), the resulting data, and the rationale behind the design. Trained technicians will conduct regular in situ observations of plant phenology at all terrestrial NEON sites for the 30‐yr life of the observatory. Standardized and coordinated data across the network of sites can be used to quantify the direction and magnitude of the relationships between phenology and environmental forcings, as well as the degree to which these relationships vary among sites, among species, among phenophases, and through time. Vegetation at NEON site...

Environmental Science: Nano, 2016

Copper-based nanoparticles have wide application in agriculture as fungicides and bactericides.

Phenology varies widely over space and time because of its sensitivity to climate. However, wheth... more Phenology varies widely over space and time because of its sensitivity to climate. However, whether phenological variation is primarily generated by rapid organismal responses (i.e., plasticity) or local adaptation remains unresolved. Here, we used 1,038,027 herbarium specimens representing 1,605 species to measure flowering time sensitivity to temperature over time (‘Stime’) and space (‘Sspace’). By comparing these estimates, we inferred how adaptation and plasticity historically influenced phenology along temperature gradients and how their contributions vary among species with different phenology and native climates, and among ecoregions differing in species composition. Sspace and Stime were highly positively correlated (r = 0.87), of similar magnitude, and more frequently consistent with plasticity than adaptation. Apparent plasticity and adaptation generated earlier flowering in spring, limited responsiveness in summer, and delayed flowering in fall in response to temperature ...

Phenological events – defined points in the life cycle of a plant or animal – have been regarded ... more Phenological events – defined points in the life cycle of a plant or animal – have been regarded as highly plastic traits, reflecting flexible responses to various environmental cues. The ability of a species to track, via shifts in phenological events, the abiotic environment through time might dictate its vulnerability to future climate change. Understanding the predictors and drivers of phenological change is therefore critical. Here, we evaluated evidence for phylogenetic conservatism – the tendency for closely related species to share similar ecological and biological attributes – in phenological traits across flowering plants. We aggregated published and unpublished data on timing of first flower and first leaf, encompassing ˜4000 species at 23 sites across the Northern Hemisphere. We reconstructed the phylogeny for the set of included species, first, using the software program Phylomatic, and second, from DNA data. We then quantified phylogenetic conservatism in plant phenology within and across sites. We show that more closely related species tend to flower and leaf at similar times. By contrasting mean flowering times within and across sites, however, we illustrate that it is not the time of year that is conserved, but rather the phenological responses to a common set of abiotic cues. Our findings suggest that species cannot be treated as statistically independent when modelling phenological responses. Synthesis. Closely related species tend to resemble each other in the timing of their life-history events, a likely product of evolutionarily conserved responses to environmental cues. The search for the underlying drivers of phenology must therefore account for species' shared evolutionary histories

International Journal of Plant Sciences, 2005

Evolutionary Ecology, 1990

Evolution, 1996

The experimental measurement of additive genetic variation in plant populations is complicated by... more The experimental measurement of additive genetic variation in plant populations is complicated by the potential for non-Mendelian inheritance. Maternal influences on progeny phenotype resulting from the cytoplasmic inheritance of plastids or RNA transcripts and effects of the maternal environment have consequently been the focus of much research. To exclude or to control for these sources of variation, breeding designs (e.g., cross-factored, nested, or diallel) in which genetically unrelated pollen donors are mated to maternal genotypes have been adopted. Using these designs, some empirical studies have detected statistically significant differences among pollen donors in the mean performance of their pollen (the mature male gametophytes) or in the mean phenotype of their progeny. These statistical effects of pollen-donor identity on pollen performance or progeny phenotype have frequently been interpreted as evidence for additive genetic variance among pollen donors, although patrilineal cytoplasmic inheritance or effects of the paternal environment on pollen performance or gene expression are recognized as alternative explanations. We note that environment-specific selection among developing gametophytes-in which the environment experienced by developing pollen grains (or ovules) provides a selective force causing the differential survival of gametophyte genotypes (analagous to meiotic drive)-is an additional process that may cause genetically based paternal (or maternal) effects on gametophyte performance. If genes selected during this process are expressed in the sporophyte (postfertilization), this process could also influence the phenotype of the diploid progeny. Here, we review the potential causes of statistically significant differences in mean phenotype among the gametophytes or progeny of maternal (seed-bearing) or paternal (pollen-donating) parental plants. We suggest an experimental approach that permits the detection or elimination of selection among developing gametophytes as one such cause. Specifically, the replication of homozygous parental genotypes within and across environments allows the detection and measurement of paternal and maternal environmentally induced effects on gametophyte or offspring phenotype, while eliminating meiotic drive as a source of the phenotypic variation.

Evolution, 1987

The possibility that sexual selection operates in angiosperms to effect evolutionary change in po... more The possibility that sexual selection operates in angiosperms to effect evolutionary change in polygenic traits affecting male reproductive success requires that there is additive genetic variance for these traits. I applied a half-sib breeding design to individuals of the annual, hermaphroditic angiosperm, wild radish (Raphanus raphanistrum: Brassicaceae), to estimate paternal genetic effects on, or, when possible, the narrow-sense heritability of several quantitative traits influencing male reproductive success. In spite of significant differences among pollen donors with respect to in vitro pollen tube growth rates, I detected no significant additive genetic variance in male performance with respect to the proportion of ovules fertilized, early ovule growth, the number of seeds per fruit, or mean individual seed weight per fruit. In all cases, differences among maternal plants in these traits far exceeded differences among pollen donors. Abortion rates of pollinated flowers and fertilized ovules also differed more among individuals as maternal plants than as pollen donors, suggesting strong maternal control over these processes. Significant maternal phenotypic effects in the absence of paternal genetic or phenotypic effects on reproductive traits may be due to maternal environmental effects, to non-nuclear or non-additive maternal genetic effects, or to additive genetic variance in maternal control over offspring development, independent of offspring genotype. While I could not distinguish among these alternatives, it is clear that, in wild radish, the opportunity for natural or sexual selection to effect change in seed weight or seed number per fruit appears to be greater through differences in female performance than through differences in male performance.