Garrett E. Crow

Bio: Garrett E. Crow is an academic researcher from University of New Hampshire. The author has contributed to research in topics: Flora & Wetland. The author has an hindex of 14, co-authored 47 publications receiving 638 citations.

Aquatic and wetland plants of northeastern North America : a revised and enlarged edition of Norman C. Fassett's A manual of aquatic plants

Abstract: This is by far the best and most comprehensive manual and illustrated guide to native and naturalized vascular plantsferns, conifers, and flowering plantsgrowing in aquatic and wetland habitats in northeastern North America, from Newfoundland west to Minnesota and south to Virginia and Missouri. Published in two volumes, this long-awaited work completely revises and greatly expands Norman Fassett s 1940 classic "A Manual of Aquatic Plants," yet retains the features that made Fassett s book so useful. Features include: * coverage of 1139 plant species, 1186 taxa, 295 genera, 109 families* more than 600 pages of illustrations, and illustrations for more than 90% of the taxa* keys for each species include references to corresponding illustrations* habitat information, geographical ranges, and synonomy* a chapter on nuisance aquatic weeds* glossaries of botanical and habitat terms* a full index for each volume Wetland ecologists, botanists, resource managers, public naturalists, and environmentalists concerned with the preservation of wetland areas, which are increasingly threatened, will welcome this clear, workable, and comprehensive guide."

Phylogenetic relationships in Nuphar (Nymphaeaceae): evidence from morphology, chloroplast DNA, and nuclear ribosomal DNA.

Abstract: The genus Nuphar consists of yellow-flowered waterlilies and is widely distributed in north-temperate bodies of water. Despite regular taxonomic evaluation of these plants, no explicit phylogenetic hypotheses have been proposed for the genus. We investigated phylogenetic relationships in Nuphar using morphology and sequences of the chloroplast gene matK and of the internal transcribed spacer (ITS) regions of nuclear ribosomal DNA. Two major lineages within Nuphar are consistently resolved with the morphological and molecular data sets. One lineage comprises New World taxa and the other represents a primarily Old World lineage. Relationships within the major lineages were poorly resolved by morphology and ITS, yet certain relationships were elucidated by all analyses. Most notable is the strong support for a monophyletic lineage of dwarf taxa and the alliance of the North American N. microphylla with the Eurasian taxa. Minor discordance between the independent cladograms is accounted for by hybridization. The common taxonomic practice of uniting all North American and Eurasian taxa under one species is not supported phylogenetically.

LATITUDINAL GRADIENTS OF BIODIVERSITY:Pattern,Process,Scale,and Synthesis

Abstract: ▪ Abstract The latitudinal gradient of decreasing richness from tropical to extratropical areas is ecology's longest recognized pattern. Nonetheless, notable exceptions to the general pattern exist, and it is well recognized that patterns may be dependent on characteristics of spatial scale and taxonomic hierarchy. We conducted an extensive survey of the literature and provide a synthetic assessment of the degree to which variation in patterns (positive linear, negative linear, modal, or nonsignificant) is a consequence of characteristics of scale (extent or focus) or taxon. In addition, we considered latitudinal gradients with respect to generic and familial richness, as well as species evenness and diversity. We provide a classification of the over 30 hypotheses advanced to account for the latitudinal gradient, and we discuss seven hypotheses with most promise for advancing ecological, biogeographic, and evolutionary understanding. We conclude with a forward-looking synthesis and list of fertile areas f...

On the Generality of the Latitudinal Diversity Gradient

Abstract: The decline of biodiversity with latitude has received great attention, but both the concise pattern and the causes of the gradient are under strong debate. Most studies of the latitudinal gradient comprise only one or few organism types and are often restricted to certain region or habitat types. To test for significant variation in the gradient between organisms, habitats, or regions, a meta-analysis was conducted on nearly 600 latitudinal gradients assembled from the literature. Each gradient was characterized by two effect sizes, strength (correlation coefficient) and slope, and additionally by 14 variables describing organisms, habitats, and regions. The analysis corroborated the high generality of the latitudinal diversity decline. Gradients on regional scales were significantly stronger and steeper than on local scales, and slopes also varied with sampling grain. Both strength and slope increased with organism body mass, and strength increased with trophic level. The body mass-effect size relation varied for ecto- versus homeotherm organisms and for different dispersal types, suggesting allometric effects on energy use and dispersal ability as possible mechanisms for the body mass effect. Latitudinal gradients were weaker and less steep in freshwater than in marine or terrestrial environments and differed significantly between continents and habitat types. The gradient parameters were not affected by hemisphere or the latitudinal range covered. This analysis is the first to describe these general and significant patterns, which have important consequences for models aiming to explain the latitudinal gradient.

Why are most aquatic plants widely distributed? Dispersal, clonal growth and small-scale heterogeneity in a stressful environment

Abstract: Non-marine aquatic vascular plants generally show broad distributional ranges. Climatic factors seem to have limited effects on their distributions, besides the determination of major disjunctions (tropical–temperate–subarctic). Dispersal should have been frequent enough to assure the quick colonisation of extensive areas following glacial retreat, but dispersal limitation is still apparent in areas separated by geographic barriers. Aquatic vascular plants also show limited taxonomic differentiation and low within-species genetic variation. Variation within populations is particularly low, but variation among populations seems to be relatively high, mainly due to the persistence of long-lived clones. Ecotypic differentiation is often related to factors that constrain clonal reproduction (salinity and ephemeral inundation). Inland aquatic habitats are heterogeneous environments, but this heterogeneity largely occurs at relatively small scales (within waterbodies and among neighbouring ones). They also represent a stressful environment for plants, characterised by low carbon availability, shaded conditions, sediment anoxia, mechanical damage by currents and waves, significant restrictions to sexual reproduction, and sometimes also osmotic stress and limited nutrient supply. I propose that the generality of broad distributions and low differentiation among the inland aquatic flora is best explained by a combination of: (1) selection for stress-tolerant taxa with broad tolerance ranges. (2) The selective advantages provided by clonal growth and multiplication, which increases plant tolerance to stress, genet survivorship and population viability. (3) Long-distance dispersal of sexual propagules and high local dispersal of asexual clones. (4) The generality of broad plastic responses, promoted by the combination of clonal growth, high local dispersal, small-scale spatial heterogeneity and temporal variability.

Environmental influences on aquatic plants in freshwater ecosystems

Abstract: Aquatic plants are important components of many freshwater ecosystems. In this review we examine natural and anthropogenic influences on the distribution and abundance of aquatic plants, and develo...

Global diversity of aquatic macrophytes in freshwater

Abstract: Aquatic macrophytes are aquatic photosynthetic organisms, large enough to see with the naked eye, that actively grow permanently or periodically submerged below, floating on, or growing up through the water surface. Aquatic macrophytes are represented in seven plant divisions: Cyanobacteria, Chlorophyta, Rhodophyta, Xanthophyta, Bryophyta, Pteridophyta and Spermatophyta. Species composition and distribution of aquatic macrophytes in the more primitive divisions are less well known than for the vascular macrophytes (Pteridophyta and Spermatophyta), which are represented by 33 orders and 88 families with about 2,614 species in c. 412 genera. These c. 2,614 aquatic species of Pteridophyta and Spermatophyta evolved from land plants and represent only a small fraction (∼1%) of the total number of vascular plants. Our analysis of the numbers and distribution of vascular macrophytes showed that whilst many species have broad ranges, species diversity is highest in the Neotropics, intermediate in the Oriental, Nearctic and Afrotropics, lower in the Palearctic and Australasia, lower again in the Pacific Oceanic Islands, and lowest in the Antarctic region. About 39% of the c. 412 genera containing aquatic vascular macrophytes are endemic to a single biogeographic region, with 61–64% of all aquatic vascular plant species found in the Afrotropics and Neotropics being endemic to those regions. Aquatic macrophytes play an important role in the structure and function of aquatic ecosystems and certain macrophyte species (e.g., rice) are cultivated for human consumption, yet several of the worst invasive weeds in the world are aquatic plants. Many of the threats to fresh waters (e.g., climate change, eutrophication) will result in reduced macrophyte diversity and will, in turn, threaten the faunal diversity of aquatic ecosystems and favour the establishment of exotic species, at the expense of native species.