Biology subjects

Woods, H. A.

Publications and source records attributed to Woods, H. A..

9 recordsLinked to original sources

bioRxiv2026

Pervasive effects of Wolbachia on host body mass and metabolic rate

Metabolic rate is a widely variable trait that reflects organismal energy expenditure. At least half of all arthropod species carry maternally transmitted Wolbachia bacteria, but it is poorly understood how these endosymbionts affect host physiology and fitness. We tested how two central host traits, body mass and standard metabolic rate (SMR), are altered by Wolbachia for nine diverse Drosophila fly species and 13 co-occurring Wolbachia variants diverged roughly 150 million years. Interspecific trait variation was structured according to the host phylogeny, but within each host system, Wolbachia almost always altered body mass and/or SMR. Wolbachia often caused increases or decreases in body mass that, in some cases, also led to mass-dependent effects on whole-organism SMR. Other Wolbachia altered mass-adjusted SMR. These variable effects are plausibly explained by complex interactions among Wolbachia and host genomes, as documented for other traits (e.g., Wolbachia-induced cytoplasmic incompatibility). Endosymbiont effects on body mass and metabolic rate likely have cascading consequences for host biology and evolution, because these central traits are correlated with many aspects of host physiology, behavior, and life history. This also applies to hosts transinfected with Wolbachia from Drosophila to reduce the impacts of pathogens and pests on multiple continents.

evolutionary biology↗

bioRxiv2023

Resource allocation strategies and mechanical constraints drive the diversification of stick and leaf insect eggs

The diversity of insect eggs is astounding but still largely unexplained. Here, we apply phylogenetic analyses to over 210 species of stick and leaf insects (order Phasmatodea), coupled with physiological measurements of metabolic rate and water loss, to evaluate several major classes of factors that may drive egg morphological diversification: life history constraints, material costs and mechanical constraints, and ecological circumstances. We show support for all three classes, but egg size is primarily influenced by female body size and strongly trades off with egg number. Consequently, females that lay relatively fewer but larger eggs, which develop more slowly because of disproportionately low metabolic rates, tend to bury or glue them in specific locations, instead of simply dropping them from the foliage (ancestral state). This form of parental care then directly favors relatively elongated eggs, which may facilitate their specific placement and allow easier passage through the oviducts in slender species. In addition, flightless females display a higher reproductive output and consequently lay relatively more and larger eggs compared to flight-capable females. Surprisingly, local climatic conditions had only weak effects on egg traits. Overall, our results suggest that morphological diversification of stick insect eggs is driven by a complex web of causal relationships among traits, with dominant effects of resource allocation strategies and mechanical constraints.

evolutionary biology↗

bioRxiv2022

Warming undermines emergence success in a threatened alpine stonefly: a multi-trait perspective on vulnerability to climate change

Species vulnerability to global warming is often assessed using short-term metrics such as the critical thermal maximum (CTmax), which represents an organisms ability to survive extreme heat. However, an understanding of the long-term effects of sub-lethal warming is an essential link to fitness in the wild, and these effects are not adequately captured by metrics like CTmax. The meltwater stonefly, Lednia tumana, is endemic to high-elevation streams of Glacier National Park, MT, USA, and has long been considered acutely vulnerable to climate change-associated stream warming. In 2019, it was listed as Threatened under the U.S. Endangered Species Act. This presumed vulnerability to warming was challenged by a recent study showing that nymphs can withstand short-term exposure to temperatures as high as ~27 {degrees}C. But how this short-term tolerance relates to chronic, long-term warming has remained unclear. By measuring fitness-related traits at several ecologically relevant temperatures over several weeks, we show that L. tumana cannot complete its life-cycle at temperatures well below the CTmax values measured for its nymphs. Although warmer temperatures maximized growth rates, they appear to have a detrimental impact on other key traits (survival, emergence success, and wing development), thus extending our understanding of L. tumanas vulnerability to climate change. Our results call into question the use of CTmax as a measure of thermal sensitivity, while highlighting the power and complexity of multi-trait approaches to assessing climate vulnerability.

ecology↗

bioRxiv2022

Going with the flow - how a stream insect, Pteronarcys californica, exploits local flows to increase oxygen availability

For insects, aquatic life is challenging because oxygen supply is typically low compared to air. Although many insects rely on stream flows to augment oxygen supply, oxygen limitation may occur when oxygen levels or flows are low or when warm temperatures stimulate metabolic demand for oxygen. Behavior may allow insects to mitigate oxygen shortages - by moving to cooler, more oxygenated, or faster flowing microhabitats. However, whether stream insects can make meaningful choices depends on: i) how much temperature, oxygen, and flow vary at microspatial scales in streams and ii) the ability of insects to exploit that variation. We measured microspatial variation in temperature, oxygen saturation, and flow velocity within riffles of two streams in Montana, USA. Additionally, we examined the preferences of nymphs of the stonefly Pteronarcys californica to gradients of temperature, oxygen, and flow in lab choice experiments. Temperature and oxygen level varied modestly within stream riffles ([~] 1.8 {degrees}C, [~] 8.0% of air saturation, respectively). By contrast, flow velocity was highly heterogeneous, often varying by more than 125 cm s-1 within riffles and 44 cm s-1 around individual cobbles. Exploiting micro-variation in flow may thus be the most reliable option for altering rates of oxygen transport. In alignment with this prediction, P. californica nymphs showed relatively little ability to exploit laboratory gradients in temperature and oxygen. By contrast, they readily exploited micro-variation in flow - consistently choosing higher flows when conditions were warm or hypoxic. These behaviors may help stream insects mitigate low-oxygen stress from climate change and other anthropogenic disturbances. Summary StatementStonefly nymphs stressed by higher temperatures and lower oxygen availability often relocate to areas of higher flow. This behavior likely increases the ratio of oxygen supply to demand.

physiology↗

bioRxiv2021

Pervasive effects of Wolbachia on host activity

Heritable symbionts have diverse effects on the physiology, reproduction, and fitness of their hosts. Maternally transmitted Wolbachia are one of the most common endosymbionts in nature, infecting about half of all insect species. We test the hypothesis that Wolbachia alter host behavior by assessing the effects of 14 different Wolbachia strains on the locomotor activity of nine Drosophila host species. We find that Wolbachia alter the activity of six different host genotypes, including all hosts in our assay infected with wRi-like Wolbachia strains (wRi, wSuz, wAur), which have rapidly spread among Drosophila species in only the last 13,000 years. While Wolbachia effects on host activity were common, the direction of these effects varied unpredictability and sometimes depended on host sex. We hypothesize that the prominent effects of wRi-like Wolbachia may be explained by patterns of Wolbachia titer and localization within host somatic tissues, particularly in the central nervous system. Our findings support the view that Wolbachia have wide-ranging effects on host behavior. The fitness consequences of these behavioral modifications are important for understanding the evolution of host-symbiont interactions, including how Wolbachia spread within host populations.

evolutionary biology↗

bioRxiv2020

Cold tolerance of mountain stoneflies (Plecoptera: Nemouridae) from the high Rocky Mountains

ABSTRACTHow aquatic insects cope with cold temperatures is poorly understood. This is particularly true for high-elevation species that often experience a seasonal risk of freezing. In the Rocky Mountains, nemourid stoneflies (Plecoptera: Nemouridae) are a major component of mountain stream biodiversity and are typically found in streams fed by glaciers and snowfields, which due to climate change, are rapidly receding. Predicting the effects of climate change on mountain stoneflies is difficult because their thermal physiology is largely unknown. We investigated cold tolerance of several alpine stoneflies (Lednia tumana, Lednia tetonica, and Zapada spp.) from the Rocky Mountains, USA. We measured the supercooling point (SCP) and tolerance to ice enclosure of late-instar nymphs collected from a range of thermal regimes. SCPs varied among species and populations, with the lowest SCP measured for nymphs from an alpine pond, which is much more likely to freeze solid in winter than flowing streams. We also show that L. tumana cannot survive being enclosed in ice, even for short periods of time (less than three hours) at relatively mild temperatures (−0.5 °C). Our results indicate that high-elevation stoneflies at greater risk of freezing may have correspondingly lower SCPs, and despite their common association with glacial meltwater, they appear to be living near their lower thermal limits.Competing Interest StatementThe authors have declared no competing interest.View Full Text

physiology↗

bioRxiv2020

Phylogenomic resolution of sea spider diversification through integration of multiple data classes

Despite significant advances in invertebrate phylogenomics over the past decade, the higher-level phylogeny of Pycnogonida (sea spiders) remains elusive. Due to the inaccessibility of some small-bodied lineages, few phylogenetic studies have sampled all sea spider families. Previous efforts based on a handful of genes have yielded unstable tree topologies. Here, we inferred the relationships of 89 sea spider species using targeted capture of the mitochondrial genome, 56 conserved exons, 101 ultraconserved elements, and three nuclear ribosomal genes. We inferred molecular divergence times by integrating morphological data for fossil species to calibrate 15 nodes in the arthropod tree of life. This integration of data classes resolved the basal topology of sea spiders with high support. The enigmatic family Austrodecidae was resolved as the sister group to the remaining Pycnogonida and the small-bodied family Rhynchothoracidae as the sister group of the robust-bodied family Pycnogonidae. Molecular divergence time estimation recovered a basal divergence of crown group sea spiders in the Ordovician. Comparison of diversification dynamics with other marine invertebrate taxa that originated in the Paleozoic suggests that sea spiders and some crustacean groups exhibit resilience to mass extinction episodes, relative to mollusk and echinoderm lineages.

evolutionary biology↗

bioRxiv2019

Temperature-dependence of metabolic rate in tropical and temperate aquatic insects: support for the Climate Variability Hypothesis in mayflies but not stoneflies.

A fundamental gap in climate change vulnerability research is an understanding of the relative thermal sensitivity of ectotherms. Aquatic insects are vital to stream ecosystem function and biodiversity but insufficiently studied with respect to their thermal physiology. With global temperatures rising at an unprecedented rate, it is imperative that we know how aquatic insects respond to increasing temperature and whether these responses vary among taxa, latitudes, and elevations. We evaluated the thermal sensitivity of standard metabolic rate in stream-dwelling baetid mayflies and perlid stoneflies across a ~2,000 m elevation gradient in the temperate Rocky Mountains in Colorado, U.S.A., and the tropical Andes in Napo, Ecuador. We used temperature-controlled water baths and microrespirometry to estimate changes in oxygen consumption. Tropical mayflies generally exhibited greater thermal sensitivity in metabolism compared to temperate mayflies; tropical mayfly metabolic rates increased more rapidly with temperature and the insects more frequently exhibited behavioral signs of thermal stress. By contrast, temperate and tropical stoneflies did not clearly differ. Varied responses to temperature among baetid mayflies and perlid stoneflies may reflect differences in evolutionary history or ecological roles as herbivores and predators, respectively. Our results show that there is physiological variation across elevations and species and that low elevation tropical mayflies may be especially imperiled by climate warming. Given such variation among species, broad generalizations about the vulnerability of tropical ectotherms should be made more cautiously.

ecology↗

bioRxiv2019

Mountain stoneflies may tolerate warming streams: evidence from organismal physiology and gene expression

Rapid glacier recession is altering the physical conditions of headwater streams. Stream temperatures are predicted to rise and become increasingly variable, putting entire meltwater-associated biological communities at risk of extinction. Thus, there is a pressing need to understand how thermal stress affects mountain stream insects, particularly where glaciers are likely to vanish on contemporary timescales. In this study, we tested the critical thermal maximum (CTMAX) of stonefly nymphs representing multiple species and a range of thermal regimes in the high Rocky Mountains, USA. We then collected RNA-sequencing data to assess how organismal thermal stress translated to the cellular level. Our focal species included the meltwater stonefly, Lednia tumana, which was recently listed under the U.S. Endangered Species Act due to climate-induced habitat loss. For all study species, critical thermal maxima (CTMAX > 20{degrees}C) far exceeded the stream temperatures mountain stoneflies experience (< 10{degrees}C). Moreover, while evidence for a cellular stress response was present, we also observed constitutive expression of genes encoding proteins known to underlie thermal stress (i.e., heat shock proteins) even at low temperatures that reflected natural conditions. We show that high-elevation aquatic insects may not be physiologically threatened by short-term exposure to warm temperatures and that longer term physiological responses or biotic factors (e.g., competition) may better explain their extreme distributions.

physiology↗