Non-native plant removal and high rainfall years promote post-fire recovery of Artemisia californica in southern California sage scrub.
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ABSTRACT:
SUBMITTER: Thomson DM
PROVIDER: S-EPMC8297819 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:The marine opisthobranch mollusk, Aplysia californica, is a powerful experimental system in cellular, molecular, and behavioral neuroscience as well as cell and evolutionary biology because of the distinctive organization of its nervous system, which makes it advantageous for cellular and comparative analysis of a variety of behaviors and learning and memory. Aplysia's large neurons allow examination of neuronal architecture of instinctive and learned behaviors at the level of single characterized cells and defined cellular compartments (e.g., synapses). As a result, many fundamental problems in neurobiology can be analyzed more effectively in Aplysias than in Drosophila, C. elegans, and vertebrates. In a larger sense work on Aplysia is synergistic with these other experimental systems. Here, we are sequencing the genome of Aplysia both to gain access to genomic mechanisms of basic neuronal and other functions and to study these mechanisms in real physiological time with single-neuron resolution. The distinction of Aplysia as a neurobiological and cellular model system is due to the following: (1) Its nervous system has a relatively small number of nerve cells. (2) Many of these cells are large (sometimes gigantic, up to 1 mm in diameter). (3) As a result of their size, pigmentation, and position in the nervous system, many cells can easily be uniquely identified at the single cell level and can be reliably linked to the animal's behavior. (4) The cells provide enough messenger RNA to generate cDNA libraries from single cells. (5) These neurons can be isolated and cultured in vitro and they form circuits which can be explored in detail at molecular and cellular levels. (6) The animal generates a variety of behaviors, many of which can be specified in terms of their underlying circuitry. (7) Some of these behaviors can be modified by different forms of learning. Aplysia are easy to rear in the laboratory from fertilized ova to mature adults and it is possible to obtain an inbred stock of reproducing animals. In 1995, the NIH established a National Resource Center for Aplysia at the University of Miami to meet the growing needs of the biomedical community. This Center supplies over 20,000 cultured Aplysia at all developmental stages annually to the research community throughout the world. This community consists of more than 100 laboratories and over a thousand investigators with overall research budgets of tens of millions of dollars annually. In addition to its value to the neurobiological community, Aplysia is also of interest from a comparative biological perspective. Aplysia is a free-living representative of Mollusca, the second largest animal phylum (after Arthropoda). Members of this phylum have received relatively little genetic study, even though they are of considerable significance for evolutionary and developmental biology and for basic and applied biomedical studies. Aplysia has a stable diploid genome consisting of 17 haploid chromosomes with highly polyploid central neurons. The genome size of about 850 million base pairs is typical for many molluscan species. Expressed sequence tags (ESTs) have already been sequenced, including more than 50,000 unique sequences representing several thousand genes, from the central nervous system of Aplysia – see Moroz et al (2006) . These ESTs have revealed many signaling molecules and pathways, including their key receptors, kinases and substrate proteins, but many rare yet key genes (e.g., ionic channels) have escaped detection so far. To achieve a complete understanding of the biologically important genes and their regulatory elements, a careful annotation and analysis of the sequenced genome is analysis is required. The Aplysia genome project will serve two major functions. First, it will be important for neuroscience by providing a critical resource for facilitating: (a) identification of all genes and regulatory regions of this valuable organism, (b) assembling microarrays and cDNA libraries for global expression studies, including those based on single neurons and their processes, and (c) gene function analysis by RNA interference screens. Second, the Aplysia genome will be important for comparative, developmental and evolutionary biology. Aplysia will serve as a complementary invertebrate/molluscan genomic model from the most diverse and second largest clade of bilaterally symmetrical animals. The Aplysia genome will promote studies of metazoan evolution, developmental biology, neuroscience, and human health, including identifying and validating therapeutic targets for human disorders that are related to aging, cancer, the central nervous system, as well as learning and memory mechanisms.
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Project description:Understanding genetic structure and diversity within species can uncover associations with environmental and geographic attributes that highlight adaptive potential and inform conservation and management. The California gnatcatcher, Polioptila californica, is a small songbird found in desert and coastal scrub habitats from the southern end of Baja California Sur to Ventura County, California. Lack of congruence among morphological subspecies hypotheses and lack of measurable genetic structure found in a few genetic markers led to questions about the validity of subspecies within P. californica and the listing status of the coastal California gnatcatcher, P. c. californica. As a U.S. federally threatened subspecies, P. c. californica is recognized as a flagship for coastal sage scrub conservation throughout southern California. We used restriction site-associated DNA sequencing to develop a genomic dataset for the California gnatcatcher. We sampled throughout the species' range, examined genetic structure, gene-environment associations, and demographic history, and tested for concordance between genetic structure and morphological subspecies groups. Our data support two distinct genetic groups with evidence of restricted movement and gene flow near the U.S.- Mexico international border. We found that climate-associated outlier loci were more strongly differentiated than climate neutral loci, suggesting that local climate adaptation may have helped to drive differentiation after Holocene range expansions. Patterns of habitat loss and fragmentation are also concordant with genetic substructure throughout the southern California portion of the range. Finally, our genetic data supported the morphologically defined P. c. californica as a distinct group, but there was little evidence of genetic differentiation among other previously hypothesized subspecies in Baja California. Our data suggest that retaining and restoring connectivity, and protecting populations, particularly at the northern range edge, could help preserve existing adaptive potential to allow for future range expansion and long-term persistence of the California gnatcatcher.
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