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Abstract Thermal performance curves (TPCs) are important tools for predicting the sensitivity of populations to climate change. However, the interactive ways that temperature affects multiple life‐history components lead to different fitness outcomes. These interactions are poorly understood for modular animals, especially over the lifespan of individual colonies, which limits our capacity to connect physiological and demographic responses.The goal of this study was to assess and compare the relationships between temperature and different life‐history components in a modular animal to reveal the mechanisms underlying TPCs for fitness.We reared replicated clones of the marine bryozoanBugula neritinaacross a thermal gradient (16 values) ranging from 23 to 32°C, which reflected the upper thermal range of seasonal variation in the field. TPCs were constructed for survival (measured as zooids states within a colony), growth rate, development to reproductive maturity and reproductive capacity, which were measured over much of the realized lifespan expected under field conditions (~30 days).The effect of temperature was more acute on zooid states rather than whole‐colony survival, and increased temperature increased the frequency of polypide regression. Most colonies reached reproductive maturity up to ~30°C, but growth rate and reproduction decreased at temperatures beyond ~25°C. The decline in reproductive capacity over temperatures above ~25°C was then due to the decline in the production of zooids capable of brooding embryos and zooids transitioning to regressed states up until about 30°C and transitioning to dead state beyond that.Higher temperatures are often considered to affect reproduction by interfering with gametogenesis and post‐zygotic pathways, but in modular animals, changes in growth rate and module states could indirectly cause temperature sensitivity of reproduction. Our study has implications for the role of temperature in driving the sampled population's dynamics by setting the number of generations that occur during the time window when temperatures are conducive to reproduction. Our results also have implications for the generality and predictability of temperature on population persistence across unitary and modular animals. Read the freePlain Language Summaryfor this article on the Journal blog. 

ABSTRACT Warming global temperatures have consequences for biological rates. Feeding rates reflect the intake of energy that fuels survival, growth and reproduction. However, temperature can also affect food abundance and quality, as well as feeding behavior, which all affect feeding rate, making it challenging to understand the pathways by which temperature affects the intake of energy. Therefore, we experimentally assessed how clearance rate varied across a thermal gradient in a filter-feeding colonial marine invertebrate (the bryozoan Bugula neritina). We also assessed how temperature affects phytoplankton as a food source, and zooid states within a colony that affect energy budgets and feeding behavior. Clearance rate increased linearly from 18°C to 32°C, a temperature range that the population experiences most of the year. However, temperature increased algal cell size, and decreased the proportion of feeding zooids, suggesting indirect effects of temperature on clearance rates. Temperature increased polypide regression, possibly as a stress response because satiation occurred quicker, or because phytoplankton quality declined. Temperature had a greater effect on clearance rate per feeding zooid than it did per total zooids. Together, these results suggest that the effect of temperature on clearance rate at the colony level is not just the outcome of individual zooids feeding more in direct response to temperature but also emerges from temperature increasing polypide regression and the remaining zooids increasing their feeding rates in response. Our study highlights some of the challenges for understanding why temperature affects feeding rates, especially for understudied, yet ecologically important, marine colonial organisms. 

The adoption of biomass crops grown for energy is a likely source of major landscape change in coming decades during the transition from fossil fuels. There are a wide range of cropping systems that have not been widely deployed yet but could become commonplace, and our knowledge of their ecological attributes and biodiversity impacts is limited. Ants are prominent and functionally important components of grassland and agricultural ecosystems. Given their outsized influences on ecosystem structure and function, we sought to understand how ant communities are likely to be shaped by a range of bioenergy cropping systems. We characterized ant communities in a long-term experimental array in Michigan, USA containing ten dedicated bioenergy crops including annual monocultures, simple monoculture or near-monoculture perennial grasses, and complex polyculture systems. Community composition differed strongly among cropping systems, and ants were more abundant, species-rich, and functionally diverse in complex systems than in simpler systems, particularly annual crops. Our results illustrate the divergent effects that bioenergy crop adoption could have for ant communities and the important functions they carry out in agroecosystems. 

ABSTRACT Hot and cold spring travertine deposits record integrated histories reflecting changing hydrologic conditions, informing our understanding of the driving forces behind factors impacting local hydrology. We present results from a geologic and geochemical investigation of Cottonwood Travertine, located in Dixie Valley, NV, where it is unclear if the paleospring system that deposited the travertine was driven by deeply sourced hydrothermal fluids, or high fluid flow driven by wetter paleoclimate conditions. The temperature of the spring water that precipitated the Cottonwood Travertine has implications for the relative importance of hydrothermal versus climatic processes influencing the formation and cessation of this enigmatic deposit. We identified four groups of samples based on geologic setting, sample textures, and stable and clumped isotopic analysis: 1) calcite cemented upper gravels, 2) a mound area at the upper bench of the deposit, 3) samples from the flanks and from vuggy veins and fault zone cements from the base of the deposit, and 4) fibrous sub-travertine veins. The calcite-cemented gravels yielded δ18OC values as low as -18.4‰ (VPDB) and apparent TΔ47 of 52°C. The top mound of the deposit returned calcite δ18OC values between -12.8‰ and -11.7‰ (VPDB) and clumped isotope temperatures (TD47) of 24 – 32°C. Higher d13C and d18Oc values at the mound site are interpreted to reflect off gassing of CO2 and disequilibrium conditions. δ18OC and TD47 values from the slopes and base of the deposit are between -15.9‰ and -14.5‰ (VPDB) and around 20°C, respectively. Structurally, texturally, and isotopically (δ18OC = -29.4‰ (VPDB); TΔ47 = 93°C), the fibrous sub-travertine veins are more consistent with the local Jurassic host rock and probably do not reflect recent hot spring conditions. Our analysis suggests that, despite the impressive volume, Cottonwood Travertine formed from springs that were not particularly hot, and the deposit instead reflects vigorous warm spring activity in a wetter climactic regime rather than fluid flow from an extinct higher temperature hydrothermal system.