Biology subjects

Sheldon, K. S.

Publications and source records attributed to Sheldon, K. S..

4 recordsLinked to original sources

bioRxiv2026

Acclimation to thermal variability increases the intensity of activity and alters the activity window in the temperate dung beetle Onthophagus taurus

O_LIEctotherms in thermally variable environments mediate energy expenditure through both physiological and behavioural responses. However, many studies focus on constant temperature acclimation, and few consider behaviour and physiology in unison. It is unclear how acclimation to thermal variability affects locomotory choices, activity timing, and performance across daily thermal cycles. C_LIO_LIWe investigated the effects of thermal variability in the temperate dung beetle Onthophagus taurus. Following acclimation to a low amplitude (22{degrees}C {+/-} 2{degrees}C) or a high amplitude (22{degrees}C {+/-} 10{degrees}C) temperature regime, we measured behaviour and metabolic rate across temperatures. We hypothesised that O. taurus adjusts its locomotive strategy and search window when kept in high amplitude fluctuating temperatures to reduce energy loss associated with high temperature exposure. C_LIO_LIWe found that differences in energy expenditure were determined by propensity for flight which differed between acclimation treatments, particularly at intermediate temperatures. We also found that, following acclimation to a high amplitude of thermal variability, O. taurus exhibited a greater intensity of activity over a narrower window of time, and O. taurus acclimated to a low amplitude of thermal variability showed nocturnal activity. C_LIO_LIWe then used the data to model activity through the growing season over five years. Biophysical models were built using NicheMapR Microclimate and Ectotherm functions to test the length of potential searching time across seasons, the temperatures individuals are exposed, and locomotive strategy. Model outputs showed that acclimation to higher amplitudes of thermal variability increased accumulated degree-hours of activity relative to the low variability acclimation group. Individuals acclimated to higher amplitudes of thermal variability showed greater accumulated degree-hours in spring and fall, but exhibited shorter periods of activity during summer, with the model predicting increased opportunities for flight. Comparatively, O. taurus from the low variability acclimation treatment showed increased night activity in summer but did not fly. C_LI

physiology↗

bioRxiv2021

Experimental increases in temperature mean and variance alter reproductive behaviors in the dung beetle Phanaeus vindex

Temperature profoundly impacts insect development, but plasticity of reproductive behaviors may mediate the impacts of temperature change on earlier life stages. Few studies have examined the potential for behavioral plasticity of adults to buffer developing offspring from warmer, more variable temperatures associated with climate change. We used a field manipulation to examine whether the dung beetle Phanaeus vindex alters breeding behaviors in response to climate change and whether adult behavioral shifts protect offspring from temperature increases. Dung beetles lay eggs inside brood balls made of dung that are buried underground for the entirety of offspring development. Depth of the brood ball impacts the temperatures offspring experience with consequences for beetle development. We placed females in either control or greenhouse treatments that simultaneously increased temperature mean and variance. We found that females produced smaller brood balls but buried them deeper in the greenhouse treatment, suggesting burial depth may come at a cost to brood ball size, which can impact offspring nutrition. Despite being buried deeper, brood balls from the greenhouse treatment experienced warmer mean temperatures but similar amplitudes of temperature fluctuation relative to the controls. Our findings suggest adult behaviors may buffer offspring from increased temperature variation due to climate change.

ecology↗

bioRxiv2021

Drivers of inter-population variation in the gut microbiomes of sister species of Phanaeus dung beetles

The microbiome plays key roles in host physiology and ecology, but how the microbiome varies among populations of hosts is not well understood. However, different abiotic and biotic selection pressures across a species range likely lead to variation in the microbiome. In addition, symbiotic microbiota may differ more between closely-related species in sympatry than in allopatry if selection favors the reduction of interspecific competition. We investigated variation in the maternally-transmitted, beneficial gut microbiomes of Phanaeus vindex and P. difformis, sister species of dung beetle that compete for the same resources in sympatry and occur across diverse climatic conditions. We sampled and sequenced bacterial/archaeal 16S rDNA from guts of P. difformis and P. vindex collected across 17 sympatric and allopatric sites. Gut microbial communities were best predicted by temperature and precipitation, cattle present at sites, and spatial relationships among sites. Contrary to our hypotheses, we did not find that the gut microbial communities of P. vindex and P. difformis differed more in sympatry than in allopatry, nor that P. vindex, the more broadly distributed of the two species, exhibited greater microbiome turnover among populations. However, the gut microbiome of P. vindex shifted more between sympatric and allopatric populations than did that of P. difformis, suggesting character displacement. While more research is needed, it is possible that differences in gut microbial communities allow P. vindex and P. difformis to partition their niches in sympatry. Our work argues for further exploration of the gut microbiomes potential role in niche partitioning and local adaptation.

ecology↗

bioRxiv2019

Panmixia across elevation in thermally sensitive Andean dung beetles

Janzens seasonality hypothesis predicts that organisms inhabiting environments with limited climatic variability will evolve a reduced thermal tolerance breadth compared with organisms experiencing greater climatic variability. In turn, narrow tolerance breadth may select against dispersal across strong temperature gradients, such as those found across elevation. This can result in narrow elevational ranges and generate a pattern of isolation-by-environment, or neutral genetic differentiation correlated with environmental variables that is independent of geographic distance. We tested for signatures of isolation-by-environment across elevation using genome-wide SNP data from five species of Andean dung beetles (subfamily Scarabaeinae) with well-characterized, narrow thermal physiologies and narrow elevational distributions. Contrary to our expectations, we found no evidence of population genetic structure associated with elevation and little signal of isolation- by-environment. Further, elevational ranges for four of five species appear to be at equilibrium and show no evidence of demographic constraints at range limits. Taken together, these results suggest physiological constraints on dispersal may primarily operate outside of a stable realized niche.\n\n\n\nO_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=134 SRC=\"FIGDIR/small/783233v2_ufig1.gif\" ALT=\"Figure 1\">\nView larger version (84K):\norg.highwire.dtl.DTLVardef@1a1d1c4org.highwire.dtl.DTLVardef@d2b557org.highwire.dtl.DTLVardef@17f860dorg.highwire.dtl.DTLVardef@139f38a_HPS_FORMAT_FIGEXP M_FIG C_FIG

ecology↗