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1. Historical interactions are predicted to be disrupted under future climate change: The case of lace lichen and valley oak

   https://doi.org/10.1111/jbi.13442  

   Zhao, Jian‐Li ; Werth, Silke ; Ikegami, Makihiko ; Gugger, Paul F. ; Sork, Victoria L. ( November 2018 , Journal of Biogeography)

   The distributions and interactions of co‐occurring species may change if their ranges shift asymmetrically in response to rapid climate change. We aim to test whether two currently interacting taxa, valley oak (Quercus lobata) and lace lichen (Ramalina menziesii), have had a long‐lasting historical association and are likely to continue to associate in the future.

   Central western California, western United States of America

   Using population genetic analyses andMaxEntsoftware for ecological niche modelling, we estimate species’ distributions during the Last Interglacial, the Last Glacial Maximum, present, and future periods. Mantel and vertex (genetic connection) tests were used to examine the spatial congruence among taxa. To compare the modelled response to climate change, we estimated migration speed between respective time periods using vector analysis.

   We found significant genetic congruence between valley oak and the lichen's green algal photobiont, independent of geographic isolation and habitat isolation, which is consistent with long‐term association. Ecological niche models under past and future climate scenarios indicate that overlap of climatic niche sharing between valley oak and lace lichen might decrease in the future. Our models indicate that the speed of shifts in climate niches between these two taxa differed significantly in past periods from that of the present period.

   Our findings reveal that historical interactions between valley oak and lace lichen correlate with long‐term sharing of past climate niches. However, the future association of lace lichen with valley oak may be disrupted in parts of its current distribution due to differential discordance of climate niche shifts, species’ movements and generation times. This study illustrates the processes and patterns that allow long‐term association during historic climate change and how they are likely to change during rapid climate change.

    

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2. Comparing Prochlorococcus temperature niches in the lab and across ocean basins

   https://doi.org/10.1002/lno.11777  

   Smith, Alaina N. ; Hennon, Gwenn M. M. ; Zinser, Erik R. ; Calfee, Benjamin C. ; Chandler, Jeremy W. ; Barton, Andrew D. ( May 2021 , Limnology and Oceanography)

   Niche theory suggests that the realized niche occupied by an organism in the field is a subset of the fundamental niche space of the organism, absent additional biotic and abiotic factors. Though often assumed, this discrepancy is rarely tested for specific organisms, and could act as a source of error in model predictions of biogeographical shifts resulting from temperature change which assume niche theory constraints. Here, we quantify the difference between fundamental and realized temperature niches for four dominant ecotypes ofProchlorococcus, including eMED4, eMIT9312, eMIT9313, and eNATL2A, and ask whether the realized temperature niches of each ecotype vary across ocean basins. The realized niches for the four ecotypes are, on average, 3.84°C ± 1.18°C colder (mean ± SD across all ocean basins and ecotypes) and 2.15°C ± 1.89°C wider than the lab‐measured fundamental niches. When divided into four ocean regions—North Atlantic, South Atlantic, North Pacific, and South Pacific—we find that the realized temperature niche optimum for a given ecotype compared to the fundamental temperature niche optimum differs across regions by as much as 7.93°C, while the niche width can differ by up to 9.48°C. Colder and wider realized niches may be a result of the metabolic risk associated with living in variable environments when the mean temperature is too close to the optimal temperature for growth or due to physical processes such as dispersal. The strong differences in temperature niches across ocean basins suggest that unresolved genetic diversity within ecotypes, local adaptation, and variable interactive ecological and environmental factors are likely to be important in shapingProchlorococcusrealized temperature niches.

    

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3. Diverse strategies for tracking seasonal environmental niches at hemispheric scale

   https://doi.org/10.1111/geb.13722  

   Cohen, Jeremy ; Jetz, Walter ( June 2023 , Global Ecology and Biogeography)

   Species depend upon a constrained set of environmental conditions, or environmental niches, for survival and reproduction that are being increasingly perturbed or lost under rapid climatic change. Seasonal environments, which require species to withstand shifting conditions or track their niches via movement, can offer an important system to study the range of biological responses to potentially cope with climate change. Here, we develop a novel methodological framework to identify niche‐tracking strategies, including the tracking of niche position and breadth, using a uniquely well‐sampled system of 619 New World bird species.

   Western Hemisphere.

   1980–2020.

   Birds (Aves).

   At continental scales, we identify the tracking of both environmental niche position and breadth and assess its phylogenetic and functional underpinning. Partitioning niche position and breadth tracking can inform whether climatic means or extremes constrain seasonal niches.

   We uncover four primary niche‐tracking strategies, including the tracking of environmental niche position, niche breadth, both or neither. Species that track niche position most often also track niche breadth, but nearly 40% only track one component and 26% only track niche breadth and not position. There is only limited phylogenetic determinism to this variation, but a strong association with ecological and functional attributes that differs between niche position versus niche breadth tracking.

   The observed diversity in type and strength of environmental niche‐tracking strategies points to highly differing sensitivity to ongoing climatic change, with narrow trackers of both position and breadth particularly susceptible. The trait associations of niche tracking imply significant functional consequences for communities and ecosystems as impending climate change affects some strategies more strongly than others. Seasonal environments and their diversity of niche‐tracking strategies offer exceptionally dynamic systems for understanding the biological responses and consequences of climate change.

    

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4. Climatic niche comparisons of eastern North American and eastern Asian disjunct plant genera

   https://doi.org/10.1111/geb.13504  

   Melton, Anthony E. ; Clinton, Matthew H. ; Wasoff, Donald N. ; Lu, Limin ; Hu, Haihua ; Chen, Zhiduan ; Ma, Keping ; Soltis, Douglas E. ; Soltis, Pamela S. ( April 2022 , Global Ecology and Biogeography)

   While the floras of eastern Asia (EA) and eastern North America (ENA) share numerous genera, they have drastically different species richness. Despite an overall similarity in the quality of their temperate climates, the climate of EA is more spatially heterogeneous than that of ENA. Spatial environmental heterogeneity has been found to play a key role in influencing species richness in some regions. Here, we tested the following hypotheses: (a) EA species will occupy larger climatic niches than their ENA congeners, (b) congeners of EA‐ENA disjunct genera will occupy statistically equivalent climatic niches, and (c) congeners of EA‐ENA disjunct genera will occupy more similar climatic niches than expected by their respective physiographic context.

   North America and Asia.

   Present.

   Seed plants.

   Predictions generated by ecological niche models (ENMs) were compared for 88 species across 31 EA‐ENA disjunct genera. ENM predictions were assessed for geographic and ecological breadth. Tests for niche equivalency and similarity were performed for congeneric species pairs to determine if species of disjunct genera have experienced niche conservatism or divergence.

   EA species tend to occupy greater amounts of climatic niche space than their close relatives in ENA. Over two‐thirds of the conducted niche comparisons show that EA‐ENA congeners either occupy equivalent climatic niche space within these broader climatic regimes or occupy non‐equivalent niches that are as similar as expected given their physiographic contexts.

   EA species tend to occupy larger climatic niches, and congeners of EA‐ENA disjunct genera tend to occupy equivalent/similar niche space within their respective distributions, with differences in occupied niches possibly due to their respective physiographic contexts, highlighting how niche‐neutral processes and niche conservatism may affect the distributions of disjunct species.

    

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5. Adaptation to lower latitudes and lower elevations precedes the evolution of hummingbird pollination in western North American Penstemon

   https://doi.org/10.1002/ajb2.1857  

   Hamilton, Ashley M. ; Wessinger, Carolyn A. ( June 2022 , American Journal of Botany)

   A switch in pollinator can occur when a plant lineage enters a new habitat where the ancestral pollinator is less common, and a novel pollinator is more common. Because pollinator communities vary according to environmental tolerances and availability of resources, there may be consistent associations between pollination mode and specific regions and habitats. Such associations can be studied in lineages that have experienced multiple pollinator transitions, representing evolutionary replicates.

   Our study focused on a large clade ofPenstemonwildflower species in western North America, which has repeatedly evolved hummingbird‐adapted flowers from ancestral bee‐adapted flowers. For each species, we estimated geographic ranges from occurrence data and inferred environmental niches from climate, topographical, and soil data. Using a phylogenetic comparative approach, we investigated whether hummingbird‐adapted species occupy distinct geographic regions or habitats relative to bee‐adapted species.

   Hummingbird‐adapted species occur at lower latitudes and lower elevations than bee‐adapted species, resulting in a difference in their environmental niche. Bee‐adapted species sister to hummingbird‐adapted species are also found in relatively low elevations and latitudes, similar to their hummingbird‐adapted sister species, suggesting ecogeographic shifts precede pollinator divergence. Sister species pairs—regardless of whether they differ in pollinator—show relatively little geographic range overlap.

   Adaptation to a novel pollinator may often occur in geographic and ecological isolation from ancestral populations. The ability of a given lineage to adapt to novel pollinators may critically depend on its ability to colonize regions and habitats associated with novel pollinator communities.

    

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