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1. Stem succulence controls flower and fruit production but not stem growth in the desert shrub ocotillo ( Fouquieria splendens )

   https://doi.org/10.1002/ajb2.1237  

   Killingbeck, Keith_T (February 2019, American Journal of Botany)

   Premise of the StudyThe C₃desert shrub ocotillo (Fouquieria splendens) completely lacks xeromorphic leaves but is uncommonly both stem succulent and repetitively drought deciduous (documented to have produced many foliation–defoliation cycles during a growing season). Both adaptations conserve water in this xerophyte, but are the roles of succulence and deciduousness merely redundant? The observation that year‐to‐year reproductive effort was relatively consistent while vegetative growth was not offered a critical clue that, coupled with long‐term precipitation data, helped answer this question. MethodsAt two sites in the Chihuahuan Desert in southern New Mexico, United States, 22 ocotillos were studied annually for more than two decades to explore the relationships among reproductive effort, vegetative stem growth, and patterns of precipitation. Key ResultsVegetative stem growth occurred in mid‐ to late summer (July–September), the season of maximum precipitation in the Chihuahuan Desert, and was significantly related to summer precipitation received in the year of growth. Reproductive effort occurred in early to late spring (April–June), which with winter account for minimum precipitation during the year, but was significantly related to summer precipitation received in the previous year, suggesting the importance of stem succulence and stored water. ConclusionsWhile highly variable summer precipitation was responsible for enormous fluctuations in annual ocotillo stem growth, stem succulence insulated reproductive effort from such immense variability. Stem‐stored water allowed the production of flowers and fruits to proceed relatively consistently during the driest years and during the driest time of year in the Chihuahuan Desert. 

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2. Comparative Phylogeography of Phrynosomatid Lizards in Baja California: Asynchronous Divergences and Expansion of Callisaurus draconoides Across the North American Deserts

   https://doi.org/10.1111/jbi.70075  

   Gottscho, Andrew D; Hollingsworth, Bradford D; Espinal, Julio Lemos; Leaché, Adam D; Reeder, Tod W; de_Queiroz, Kevin (October 2025, Journal of Biogeography)

   ABSTRACT AimWe tested whether co‐distributed phrynosomatid lizards in the Baja California Peninsula (BCP) share synchronous phylogeographic discontinuities, as predicted by the “peninsular archipelago” hypothesis, and examined the diversification ofCallisaurus draconoidesthroughout its range. LocationThe BCP and the Great Basin, Mojave and Sonoran Deserts of southwestern North America. TaxaFive co‐distributed species complexes representing four genera within Phrynosomatidae:Callisaurus,Petrosaurus,UrosaurusandSceloporus. MethodsDouble‐digest restriction‐associated‐DNA (ddRAD) sequencing was used to collect genome‐wide sequence data for 309 lizards. We used phylogenetic analyses of concatenated loci and population admixture analysis of unlinked SNPs to identify lineages. To infer a species tree, we collected target sequence capture (TSC) data. Migration between adjacent peninsular lineages was estimated using the multispecies coalescent with migration (MSC‐M) in BPP. A full‐likelihood Bayesian comparative phylogeographic approach (ecoevolity) was used to test the simultaneous divergence hypothesis for the Isthmus of La Paz and Vizcaíno Desert. ResultsWe identified 24 potential lineages within the five co‐distributed complexes. Contact zones between lineages were observed at the Isthmus of La Paz in four of the five complexes, and in all five within the Vizcaíno Desert. The time‐calibrated species tree indicates that within each complex, divergences at the Isthmus of La Paz predate those across the Vizcaíno Desert. We found strong support for at least three independent divergence events at the Isthmus of La Paz and the Vizcaíno Desert, thereby rejecting the simultaneous divergence hypothesis. Inferred migration rates between adjacent peninsular populations were generally low (M << 1) to absent. Zebra‐tailed lizards (Callisaurus), in which the earliest diverging lineages are endemic to the southern BCP, exhibit a clear pattern of Pleistocene range expansion from the BCP into the deserts of the western United States and mainland Mexico. The most deeply nested populations inCallisaurusoccur at the northern, eastern and southeastern range limits in temperate, subtropical and tropical biomes, respectively. Main ConclusionsThese results support the BCP's tectonic isolation as a driver of peninsular endemism and a contributing factor to lineage diversification more broadly in the region. Taxonomic adjustments, including resurrectingUrosaurus microscutatus, are proposed to better reflect evolutionary history in taxonomy. 

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3. Press–pulse interactions and long‐term community dynamics in a Chihuahuan Desert grassland

   https://doi.org/10.1111/jvs.12881  

   Collins, Scott L.; Chung, Y. Anny; Baur, Lauren E.; Hallmark, Alesia; Ohlert, Timothy J.; Rudgers, Jennifer A.; Valencia, ed., Enrique (May 2020, Journal of Vegetation Science)

   Abstract QuestionsReordering of dominant species is an important mechanism of community response to global environmental change. We asked how wildfire (apulseevent) interacts with directional changes in climate (environmentalpresses) to affect plant community dynamics in a Chihuahuan Desert grassland. LocationSevilleta National Wildlife Refuge, Socorro County, New Mexico, USA. MethodsVegetation cover by species was measured twice each year from 1989 to 2019 along two permanently located 400‐m long line intercept transects, one in Chihuahuan Desert grassland, and the second in the ecotone between Chihuahuan Desert and Great Plains grasslands. Trends in community structure were plotted over time, and climate sensitivity functions were used to predict how changes in the Pacific Decadal Oscillation (PDO) affected vegetation dynamics. ResultsCommunity composition was undergoing gradual change in the absence of disturbance in the ecotone and desert grassland. These changes were related to the reordering of abundances between two foundation grasses,Bouteloua eriopodaandB. gracilis, that together account for >80% of above‐ground primary production. However, reordering varied over time in response to wildfire (apulse) and changes in the PDO (apress). Community dynamics were initially related to the warm and cool phases of the PDO, but in the ecotone these relationships changed following wildfire, which reset the system. ConclusionSpecies reordering is an important component of community dynamics in response to ecological presses. However, reordering is a complex, non‐linear process in response to ecological presses that may change over time and interact with pulse disturbances. 

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4. A chromosome-level genome assembly and annotation of the desert horned lizard, Phrynosoma platyrhinos , provides insight into chromosomal rearrangements among reptiles

   https://doi.org/10.1093/gigascience/giab098  

   Koochekian, Nazila; Ascanio, Alfredo; Farleigh, Keaka; Card, Daren_C; Schield, Drew_R; Castoe, Todd_A; Jezkova, Tereza (February 2022, GigaScience)

   Abstract BackgroundThe increasing number of chromosome-level genome assemblies has advanced our knowledge and understanding of macroevolutionary processes. Here, we introduce the genome of the desert horned lizard, Phrynosoma platyrhinos, an iguanid lizard occupying extreme desert conditions of the American southwest. We conduct analysis of the chromosomal structure and composition of this species and compare these features across genomes of 12 other reptiles (5 species of lizards, 3 snakes, 3 turtles, and 1 bird). FindingsThe desert horned lizard genome was sequenced using Illumina paired-end reads and assembled and scaffolded using Dovetail Genomics Hi-C and Chicago long-range contact data. The resulting genome assembly has a total length of 1,901.85 Mb, scaffold N50 length of 273.213 Mb, and includes 5,294 scaffolds. The chromosome-level assembly is composed of 6 macrochromosomes and 11 microchromosomes. A total of 20,764 genes were annotated in the assembly. GC content and gene density are higher for microchromosomes than macrochromosomes, while repeat element distributions show the opposite trend. Pathway analyses provide preliminary evidence that microchromosome and macrochromosome gene content are functionally distinct. Synteny analysis indicates that large microchromosome blocks are conserved among closely related species, whereas macrochromosomes show evidence of frequent fusion and fission events among reptiles, even between closely related species. ConclusionsOur results demonstrate dynamic karyotypic evolution across Reptilia, with frequent inferred splits, fusions, and rearrangements that have resulted in shuffling of chromosomal blocks between macrochromosomes and microchromosomes. Our analyses also provide new evidence for distinct gene content and chromosomal structure between microchromosomes and macrochromosomes within reptiles. 

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5. Eight genome sequences of bacterial, environmental isolates from Canada Glacier, Antarctica

   https://doi.org/10.1128/mra.01130-23  

   Smith, Heidi J; Dieser, Markus; Foreman, Christine M (August 2024, Microbiology Resource Announcements)

   Maresca, Julia A (Ed.)

   ABSTRACT Sediments in cryoconite holes and meltwater streams in the McMurdo Dry Valleys, Antarctica, provide both substrates and conditions that support life in an arid polar desert. Here, we report the genomic sequences of eight environmental, bacterial isolates from Canada Glacier cryoconite holes and stream. These isolates span three major phyla. 

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