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1. E nvironmental niche adaptation revealed through fine scale phenological niche modelling

   https://doi.org/10.1111/jbi.13663  

   Van Dam, Matthew H. ; Rominger, Andrew J. ; Brewer, Michael S. ( July 2019 , Journal of Biogeography)

   Phenology, the temporal response of a population to its climate, is a crucial behavioural trait shared across life on earth. How species adapt their phenologies to climate change is poorly understood but critical in understanding how species will respond to future change. We use a group of flies (Rhaphiomidas) endemic to the North American deserts to understand how species adapt to changing climatic conditions. Here, we explore a novel approach for taxa with constrained phenologies aimed to accurately model their environmental niche and relate this to phenological and morphological adaptations in a phylogenetic context.

   Insecta, Diptera, Mydidae,Rhaphiomidas.

   North America, Mojave, Sonoran and Chihuahuan Deserts.

   We gathered geographical and phenological occurrence data for the entire genusRhaphiomidas, and, estimated a time calibrated phylogeny. We compared Daymet derived temperature values for a species adult occurrence period (phenology) with those derived from WorldClim data that is partitioned by month or quarter to examine what effect using more precise data has on capturing a species’ environmental niche. We then examined to what extent phylogenetic signal in phenological traits, climate tolerance and morphology can inform us about how species adapt to different environmental regimes.

   We found that the Bioclim temperature data, which are averages across monthly intervals, poorly represent the climate windows to which adult flies are actually adapted. Using temporally relevant climate data, we show that many species use a combination of morphological and phenological changes to adapt to different climate regimes. There are also instances where species changed only phenology to track a climate type or only morphology to adapt to different environments.

   Without using a fine‐scale phenological data approach, identifying environmental adaptations could be misleading because the data do not represent the conditions the animals are actually experiencing. We find that fine‐scale phenological niche models are needed when assessing taxa that have a discrete phenological window that is key to their survival, accurately linking environment to morphology and phenology. Using this approach, we show thatRhaphiomidasuse a combination of niche tracking and adaptation to persist in new niches. Modelling the effect of phenology on such species’ niches will be critical for better predictions of how these species might respond to future climate change.

    

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2. The compounding consequences of wildfire and climate change for a high‐elevation wildflower ( Saxifraga austromontana )

   https://doi.org/10.1111/jbi.13441  

   Bloom, Trevor D. S. ; Flower, Aquila ; Medler, Michael ; DeChaine, Eric G. ( October 2018 , Journal of Biogeography)

   High‐elevation plants are disproportionally affected by climate change. As temperatures rise, the amount of available alpine habitat in the Rocky Mountains will decrease resulting in potential local extinctions of plant species. In addition to the direct effects of climate‐driven habitat loss, alpine plants must also respond to indirect effects, such as changes in disturbance regimes. One notable shift is the increase of wildfire frequency in regions where fire was previously rare or absent, including the alpine. We hypothesized that direct climatic changes compounded with increased wildfire frequency will reduce the future suitable habitat of high‐elevation plants more than if climate was considered alone.

   Rocky Mountain Floristic Region, western North America.

   Saxifraga austromontana(Saxifragaceae), a wildflower endemic to high elevations of the Rocky Mountain Floristic Region.

   Our approach integrated historical herbarium records, field surveys, remote sensing, species distribution models, historic wildfire data, and predictive models.

   Our results indicate wildfire has significantly reduced the abundance and increased the likelihood of extirpation forS. austromontana. Increased fire frequency compounded with direct climatic changes will likely reduce the range of the species by approximately 43% by 2050 compared to 38% due to climate alone, under a moderateCO₂emissions scenario. The influence of wildfire varies regionally. For instance, the Middle Rockies will likely lose 74% of its suitable habitat of which 16% may be lost due to fire, while other regions, such as the northern range, will be less negatively affected by direct and indirect effects.

   Our evidence that increased wildfire frequency will compound the impacts of climate change on alpine taxa in North America led to the development of a new, general hypothesis on the fundamental interaction between direct and indirect effects of climate change on species range reductions.

    

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3. Host–enemy interactions provide limited biotic resistance for a range‐expanding species via reduced apparent competition

   https://doi.org/10.1111/ddi.13763  

   Prior, Kirsten M. ; Jones, Dylan G. ; Meadley‐Dunphy, Shannon A. ; Lee, Susan ; Milks, Alyson K. ; Daughton, Sage ; Forbes, Andrew A. ; Powell, Thomas H. Q. ( August 2023 , Diversity and Distributions)

   As species' ranges shift poleward in response to anthropogenic change, they may lose antagonistic interactions if they move into less diverse communities, fail to interact with novel populations or species effectively, or if ancestral interacting populations or species fail to shift synchronously. We leveraged a poleward range expansion in a tractable insect host–enemy community to uncover mechanisms by which altered antagonistic interactions between native and recipient communities contributed to ‘high niche opportunities’ (limited biotic resistance) for a range‐expanding insect.

   North America, Pacific Northwest.

   We created quantitative insect host–enemy interaction networks by sampling oak gall wasps on 400 trees of a dominant oak species in the native and expanded range of a range‐expanding gall wasp species. We compared host–enemy network structure between regions. We measured traits (phenology, morphology) of galls and interacting parasitoids, predicting greater trait divergence in the expanded range. We measured function relating to host control and explored if altered interactions and traits contributed to reduced function, or biotic resistance.

   Interaction networks had fewer species in the expanded range and lower complementarity of parasitoid assemblages among host species. While networks were more generalized, interactions with the range‐expanding species were more specialized in the expanded range. Specialist enemies effectively tracked the range‐expanding host, and there was reduced apparent competition with co‐occurring hosts by shared generalist enemies. Phenological divergence of enemy assemblages interacting with the range‐expanding and co‐occurring hosts was greater in the expanded range, potentially contributing to weak apparent competition. Biotic resistance was lower in the expanded range, where fewer parasitoids emerged from galls of the range‐expanding host.

   Changes in interactions with generalist enemies created high niche opportunities, and limited biotic resistance, suggesting weak apparent competition may be a mechanism of enemy release for range‐expanding insects embedded within generalist enemy networks.

    

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4. Caught in a bottleneck: Habitat loss for woolly mammoths in central North America and the ice‐free corridor during the last deglaciation

   https://doi.org/10.1111/geb.13238  

   Wang, Yue ; Widga, Chris ; Graham, Russell W. ; McGuire, Jenny L. ; Porter, Warren ; Wårlind, David ; Williams, John W. ; Lyons, ed., Kathleen ( December 2020 , Global Ecology and Biogeography)

   Identifying how climate change, habitat loss, and corridors interact to influence species survival or extinction is critical to understanding macro‐scale biodiversity dynamics under changing environments. In North America, the ice‐free corridor was the only major pathway for northward migration by megafaunal species during the last deglaciation. However, the timing and interplay among the late Quaternary megafaunal extinctions, climate change, habitat structure, and the opening and reforestation of the ice‐free corridor have been unclear.

   North America.

   15–10 ka.

   Woolly mammoth (Mammuthus primigenius).

   For central North America and the ice‐free corridor between 15 and 10 ka, we used a series of models and continental‐scale datasets to reconstruct habitat characteristics and assess habitat suitability. The models and datasets include biophysical and statistical niche models Niche Mapper and Maxent, downscaled climate simulations from CCSM3 SynTraCE, LPJ‐GUESS simulations of net primary productivity (NPP) and woody cover, and woody cover based upon fossil pollen from Neotoma.

   The ice‐free corridor may have been of limited suitability for traversal by mammoths and other grazers due to persistently low productivity by herbaceous plants and quick reforestation after opening 14 ka. Simultaneously, rapid reforestation and decreased forage productivity may have led to declining habitat suitability in central North America. This was possibly amplified by a positive feedback loop driven by reduced herbivory pressures, as mammoth population decline led to the further loss of open habitat.

   Declining habitat availability south of the Laurentide Ice Sheet and limited habitat availability in the ice‐free corridor were contributing factors in North American extinctions of woolly mammoths and other large grazers that likely operated synergistically with anthropogenic pressures. The role of habitat loss and attenuated corridor suitability for the woolly mammoth extinction reinforce the critical importance of protected habitat connectivity during changing climates, particularly for large vertebrates.

    

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5. Climate‐related geographical variation in performance traits across the invasion front of a widespread non‐native insect

   https://doi.org/10.1111/jbi.14005  

   Thompson, Lily M. ; Powers, Sean D. ; Appolon, Ashley ; Hafker, Petra ; Milner, Lelia ; Parry, Dylan ; Agosta, Salvatore J. ; Grayson, Kristine L. ( November 2020 , Journal of Biogeography)

   Invasive species are ideal systems for testing geographical differences in performance traits and measuring evolutionary responses as a species spreads across divergent climates and habitats. The European gypsy moth,Lymantria dispar disparL. (Lepidoptera: Erebidae), is a generalist forest defoliator introduced to Medford, Massachusetts, USA in 1869. The invasion front extends from Minnesota to North Carolina and the ability of this species to adapt to local climate may contribute to its continuing spread. We evaluated the performance of populations along the climatic gradient of the invasion front to test for a relationship between climate and ecologically important performance traits.

   Eastern United States of America

   Lymantria dispar disparL. (Lepidoptera: Erebidae)

   Insects from 14 populations across the US invasion front and interior of the invasive range were reared from hatch to adult emergence in six constant temperature treatments. The responses of survival, pupal mass and larval development time were analysed as a function of source climate (annual mean normal temperature), rearing temperature and their interaction using multiple polynomial regression.

   With the exception of female development time, there were no significant interactions between source climate and rearing temperature, indicating little divergence in the shape of thermal reaction norms among populations. Source population and rearing temperature were significant predictors of survival and pupal mass. Independent of rearing temperature, populations from warmer climates had lower survival than those from colder climates, but attained larger body size despite similar development times. Larval development time was dependent on rearing temperature, but there were not consistent relationships with source climate.

   Thermal adaptation can be an important factor shaping the spread of invasive species, particularly in the context of climate change. Our results suggest thatL. d. disparis highly plastic, but has undergone climate‐related adaptation in thermal performance and life‐history traits as it spread across North America.

    

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