New Paper Out! Current and lagged climate affects phenology across diverse taxonomic groups

A synthesis paper led my myself, and 15 co-authors is now out in Proceedings of the Royal Society B: Biological Sciences. This paper examined how different aspects of climate affect phenology across five taxonomic groups encompassing 62 species. Researchers at the Rocky Mountain Biological Laboratory have been collecting phenological data since 1975. Working together, we were able to draw conclusions about how climate is altering phenology in the Crested Butte area of Colorado.

We found that species responses varied significantly across climate factors. While taxa responded to some cues similarly, such as snowmelt date and spring temperatures, other climate cues resulted in differential effects across taxa. Prior summer precipitation delayed first activity of some insects but advanced activity of some amphibians, mammals, and birds. Earlier snowmelt strongly advanced first activity of insects that overwinter as larvae, including Mormon fritillary butterflies, burying beetles, Gillette’s checkerspot butterfly, and flies, as well as plants that flower soon after snowmelt, including spring beauty and dwarf bluebell.

The fact that not all species are responding identically to the changing climate means that in the future some current interactions, such as those between particular wildflowers and pollinators, may no longer occur. Migratory hummingbirds may no longer arrive while glacier lilies are in bloom. Correspondingly, new kinds of interactions will characterize the future East River valley ecosystem as new species move in and current species change their activity periods. 

These results emphasize the importance of examining which cues are driving a species’ entire distribution of seasonal activity. Focusing only on cues driving first activity could provide inaccurate predictions for the remainder of a species’ phenological activity. For example, first date of flowering by a wildflower may not be a good predictor of its peak flowering.

Other unexpected results were that there were more important climate drivers of phenology than previous studies have found, that the most important cues could differ among taxa, and that the previous season’s climate could have a significant influence.

Scarlet gilia, blue flax flowers, and other midsummer wildflowers near the Rocky Mountain Biological Laboratory. Photo credit: David Inouye

Marmots (with ear tags) at the Rocky Mountain Biological Laboratory. Their emergence dates from hibernation are getting earlier. Photo credit: David Inouye

Broad-tailed Hummingbird male visiting flowers of the dwarf larkspur. Photo credit: David Inouye

A Mormon Fritillary butterfly on its nectar host plant, a fleabane daisy. Photo credit: David Inouye

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New paper out! Micronutrients enhance macronutrient effects in a meta-analysis of grassland arthropod abundance

A meta-analysis led my myself, Karen Castillioni, and Ellen Welti is now out in Global Ecology and Biogeography! This paper examined the effects of micro- and macronutrient fertilization in grasslands on plant biomass, plant nutrient content, and on the abundance of six arthropod trophic groups.

We found the interesting result that micronutrients applied alone had no effects on plant biomass or arthropod abundance. However, when added with macronutrients (such as nitrogen, phosphorus, and potassium), micronutrients amplified the effect of N, P and K in promoting arthropod abundance, a synergy that did not affect plant biomass (Figure 1).

Figure 2. Forest plot showing effect sizes (Cohen’s d) of (a) plant biomass and (b) total arthropod abundances by fertilizer type. Red stars denote significant effect sizes, while black circles indicate non-significant effect sizes. We included fertilizer types used in > 5 studies. The number of replicates provided within the figure refers to the number of experimental responses containing each fertilizer type. Error bars are the standard error of the mean of the effect sizes of individual experiments

Micronutrients catalyzed the ability of macronutrients to promote arthropod abundance across all arthropod guilds studied (Figure 2).

Figure 2. Forest plot showing effect sizes (Cohen’s d) of arthropod trophic group abundances by fertilizer type. Responses are provided for the trophic groups of (a) chewing herbivores, (b) sucking herbivores, (c) pollinators, (d) omnivores, (e) predators, and (f) detritivores. Red stars denote significant effect sizes, while black circles indicate non-significant effect sizes. We included fertilizer types used in ≥ 5 studies. Number of replicates provided within the figure refers to the number of experimental responses containing each fertilizer type and trophic group. Error bars are the standard error of the mean of the effect sizes of individual experiments

This paper was a result of a collaboration with Dr. Lara Souza and Dr. Mike Kaspari at OU and Dr. Chelse Prather and Ryan Reihart at the University of Dayton. We highlight a stoichiometric mismatch between limits of plants and arthropods for metal cations whose biogeochemistry, along with N and P, are being actively rearranged in the Anthropocene.

You can read the paper here. https://rmprather.files.wordpress.com/2020/10/prather-et-al.-2020-geb-meta-analysis.pdf

New paper out! The economics of optimal foraging by the red imported fire ant.

New paper out in Environmental Entomology! This is the 3rd publication for 2020, a surprisingly productive year.

Karl Roeder sums up the paper nicely, “Here we look at how the red imported fire ant, Solenopsis invicta, regulates its foraging behavior. This was an interesting project that we first piloted back in 2015 and built on all the way through the summer of 2018. We were interested in testing ideas from optimal foraging theory and developed the Diminished Returns Hypothesis that posits for social insects (1) foraging investment levels increase until diminishing gains result in a decelerating slope of return and (2) this investment level is a function of the size of the collective group. We argue this hypothesis is an analog to Charnov’s Marginal Value Theorem and in testing it we found that fire ants forage as predicated in a particular manner. Taken as a whole, our results suggest that substantial biomass differences between invasive and native ants are likely one of the key reasons that species like red imported fire ants are able to dominate novel environments.”

You can read the paper here.

New paper out! Bottom-up when it is not top-down: Predators and plants control biomass of grassland arthropods

New paper out in Journal of Animal Ecology! This paper surveyed 54 North American grasslands to investigate whether bottom-up or top-down control regulates ecological communities. We examined the biomass of four common grassland arthropod taxa— Auchenorrhyncha, sucking herbivores, Acrididae, chewing herbivores, Tettigoniidae, omnivores, and Araneae, predators.

We found that sucking herbivores and omnivores tracked plant biomass and chewing herbivores tracked plant quality. In addition, we found that when spider biomass was low, herbivores increased with plant biomass but this didn’t happen at high spider abundances. Furthermore, stable isotope analysis showed that neither predator biomass nor trophic position changed with plant biomass, suggesting predators themselves are top-down limited. Finally, the trophic position of chewing herbivores and omnivores increased with plant biomass, suggesting increased scavenging in grasslands with increased carbohydrate availability.

This was a fun paper to work on. You can click here to read the whole paper.

 

New paper out! Abiotic factors and plant biomass, not plant diversity, strongly shape grassland arthropods under drought conditions

My third dissertation chapter is now out in Ecology! This paper used a factorial experiment of precipitation manipulation and human management (hay harvest) in a temperate mixed-grass prairie to examine 1) how two drivers, altered precipitation and biomass removal, can synergistically affect abiotic factors and plant communities and 2) how these effects can cascade upward, impacting the arthropod food web.

This paper was a result of a collaboration with Dr. Lara Souza’s lab and I worked closely with her Ph.D. candidate, Karen Castillioni. At Kessler Atmospheric and Ecological Field Station, the Souza lab set up a seven-level precipitation manipulation gradient. Using rain-out shelters, they excluded up to 100% of precipitation on plots in addition to adding +50% precipitation to other plots (Fig. 1).

I collected arthropods from plots in 2017 and 2018 and tested 3 non-exclusive hypotheses detailing how direct and indirect effects of drought and hay harvest work synergistically to affect the plant and arthropod communities in a mixed-grass prairie. I found that both drought and hay harvest increased soil surface temperature while drought decreased soil moisture. Arthropod abundance decreased with low soil moisture and, contrary to our predictions, decreased with increased plant biomass. Arthropod diversity increased with soil moisture, decreased with high surface temperatures, and tracked arthropod abundance but was surprisingly unaffected by plant diversity or quality. Our results demonstrate that arthropod abundance is directly constrained by abiotic factors and plant biomass and in turn constrains local arthropod diversity.

This was a fun project to work on. You can click here to read the full paper.