A Reappraisal of Phenotypic Variation in Daphnia galeata mendotae: The Role of Interspecific Hybridization

1993 ◽  
Vol 50 (10) ◽  
pp. 2137-2146 ◽  
Author(s):  
Derek J. Taylor ◽  
Paul D. N. Hebert
Keyword(s):  
Lake Level ◽  
Habitat Associations ◽  
Genetic Associations ◽  
Daphnia Galeata ◽  
Taxonomic Confusion ◽  
Lake Variation ◽  
Daphnia Galeata Mendotae ◽  
Daphnia Rosea ◽  
Isolating Mechanism

Seasonal, within-lake, and among-lake variation in helmet size and shape has been reported for Daphnia galeata mendotae. The genetic component of this variation was assessed by an allozyme and morphological reanalysis of nine previously studied sites. Genetic associations with morphological variation were found, but all were attributed to D. galeata mendotae × Daphnia rosea hybridization or to taxonomic confusion with D. rosea. The existence of hybrids accounted for spatial polymorphism both within and among lakes. In addition, hybrids contributed to seasonal variation as they increased in abundance from summer to winter. Nevertheless, cyclomorphosis in D. galeata mendotae s.s was real and due largely to phenotypic plasticity. Local hybridization between D. galeata mendotae and D. rosea was widespread from the midwestern states to Vermont. The distributions and habitat associations of D. galeata mendotae and D. rosea indicated that ecological segregation at the lake level acts as an important reproductive isolating mechanism. Reinterpretation of previous studies, however, suggests that disturbance followed by one or a few hybridization events often leads to hybrid domination of a lake.

Transporters, TBC1D4, and ARID5B Variants to Explain Glycated Hemoglobin Variability in Patients with Type 2 Diabetes

Pharmacology ◽  
2021 ◽  
pp. 1-9
Author(s):  
Vanessa Gonzalez-Covarrubias ◽  
Héctor Sánchez-Ibarra ◽  
Karla Lozano-Gonzalez ◽  
Sergio Villicaña ◽  
Tomas Texis ◽  
...  
Keyword(s):  
Genetic Variants ◽  
Glucose Control ◽  
Plasma Levels ◽  
Prediction Models ◽  
Glycated Hemoglobin ◽  
Clinical Chemistry ◽  
Diabetic Patients ◽  
Genetic Associations ◽  
Hemoglobin Variability

<b><i>Introduction:</i></b> Genetic variants could aid in predicting antidiabetic drug response by associating them with markers of glucose control, such as glycated hemoglobin (HbA1c). However, pharmacogenetic implementation for antidiabetics is still under development, as the list of actionable markers is being populated and validated. This study explores potential associations between genetic variants and plasma levels of HbA1c in 100 patients under treatment with metformin. <b><i>Methods:</i></b> HbA1c was measured in a clinical chemistry analyzer (Roche), genotyping was performed in an Illumina-GSA array and data were analyzed using PLINK. Association and prediction models were developed using R and a 10-fold cross-validation approach. <b><i>Results:</i></b> We identified genetic variants on <i>SLC47A1, SLC28A1, ABCG2, TBC1D4,</i> and <i>ARID5B</i> that can explain up to 55% of the interindividual variability of HbA1c plasma levels in diabetic patients under treatment. Variants on <i>SLC47A1</i>, <i>SLC28A1</i>, and <i>ABCG2</i> likely impact the pharmacokinetics (PK) of metformin, while the role of the two latter can be related to insulin resistance and regulation of adipogenesis. <b><i>Conclusions:</i></b> Our results confirm previous genetic associations and point to previously unassociated gene variants for metformin PK and glucose control.

Lake level change, climate, and the impact of natural events: the role of seismic and volcanic events in the formation of the Lake Patzcuaro Basin, Michoacan, Mexico

2005 ◽  
Vol 135 (1) ◽  
pp. 35-46 ◽  
Author(s):  
I. Israde-Alcántara ◽  
V.H. Garduño-Monroy ◽  
C.T. Fisher ◽  
H.P. Pollard ◽  
M.A. Rodríguez-Pascua
Keyword(s):  
Lake Level ◽  
Lake Level Change ◽  
Level Change ◽  
Volcanic Events ◽  
Lake Patzcuaro Basin ◽  
Change Climate ◽  
The Impact

Ecology of Mammals of the Shortgrass Steppe

2008 ◽  
Author(s):  
Paul Stapp ◽  
Beatrice Van Horne
Keyword(s):  
Great Plains ◽  
Native Species ◽  
Past Research ◽  
Habitat Associations ◽  
Shortgrass Steppe ◽  
Prairie Dogs ◽  
Vegetative Cover ◽  
Patterns And Processes ◽  
And Function

At first glance, the shortgrass steppe seems to offer little in the way of habitat for mammals. The expansive rolling plains, with little topographic relief or vegetative cover, provide minimal protection from predators or the harsh weather typical of the region. The short stature of the dominant native grasses prevents the development of any significant litter layer, and although snowfall can often be significant, too little accumulates to form the subnivean habitats that support small mammal populations in forests and more productive grasslands in winter. As a consequence, ecologists have typically considered the vertebrate fauna of the shortgrass steppe to be depauperate compared with other Great Plains grasslands, a hardy collection of generalists living in sparse populations. Although this characterization may generally be accurate, it has led mammalian ecologists to overlook the fauna of the shortgrass steppe in favor of that of other grasslands. It is precisely these circumstances, however, that suggest that a long-term approach may be necessary to understand the dynamics of mammal populations here. Relatively few such studies have been completed to date, but we can use the comparative and experimental results that are available to begin to determine what factors might be important. Here we review research on mammals in the shortgrass steppe, with the goal of identifying the general patterns and processes that contribute to them. Our review is roughly divided into four parts. We begin by describing the mammal communities and their broad habitat associations in shortgrass steppe environments. We then review the history of mammal research in the region to synthesize what these studies (many unpublished) have taught us about the most important determinants of the distribution and abundance of native species. Studies of mammal\ populations in the northern shortgrass steppe have spanned nearly 40 years, and we next describe some major patterns that have emerged from studies during this period. Much of this past research focused on the role of mammals in the structure and function of shortgrass steppe ecosystems, and we revisit this issue in some detail, with special emphasis on the important and sometimes controversial role of prairie dogs and other burrowing rodents. Finally, we end by considering how humans, and especially agriculture and its related activities, affect the diversity, abundance, and persistence of resident mammal populations.

scholarly journals Role of Upper-Flow-Regime Bedforms Emplaced by Sediment Gravity Flows in the Evolution of Deltas

2019 ◽  
Vol 7 (1) ◽  
pp. 5 ◽  
Author(s):  
Svetlana Kostic ◽  
Daniele Casalbore ◽  
Francesco Chiocci ◽  
Jörg Lang ◽  
Jutta Winsemann
Keyword(s):  
Numerical Analysis ◽  
High Resolution ◽  
Flow Regime ◽  
Case Studies ◽  
Seismic Data ◽  
Lake Level ◽  
Sediment Gravity Flows ◽  
Gravity Flows ◽  
Digital Elevation

Upper-flow-regime bedforms and their role in the evolution of marine and lacustrine deltas are not well understood. Wave-like undulations on delta foresets are by far the most commonly reported bedforms on deltas and it will take time before many of these features get identified as upper-flow-regime bedforms. This study aims at: (1) Providing a summary of our knowledge to date on deltaic bedforms emplaced by sediment gravity flows; (2) illustrating that these features are most likely transitional upper-flow-regime bedforms; and (3) using field case studies of two markedly different deltas in order to examine their role in the evolution of deltas. The study combines numerical analysis with digital elevation models, outcrop, borehole, and high-resolution seismic data. The Mazzarrà river delta in the Gulf of Patti, Italy, is selected to show that upper-flow-regime bedforms in gullies can be linked to the onset, growth, and evolution of marine deltas via processes of gully initiation, filling, and maintenance. Ice-marginal lacustrine deltas in Germany are selected as they illustrate the importance of unconfined upper-flow-regime bedforms in the onset and evolution of distinct delta morphologies under different lake-level trends.

Dieldrin reduces male production and sex ratio in Daphnia galeata mendotae

1999 ◽  
Vol 15 (1-2) ◽  
pp. 193-200 ◽  
Author(s):  
Christine M. Merritt ◽  
Laura Torrentera ◽  
Katherine M. Winter ◽  
Christopher K. Tornehl ◽  
Kristin Girvin ◽  
...  
Keyword(s):  
Sex Ratio ◽  
Male Production ◽  
Daphnia Galeata ◽  
Daphnia Galeata Mendotae

Freshwater Zooplankton Community Structure: Introduction of Large Invertebrate Predators and Large Herbivores to a Small Species Community

1988 ◽  
Vol 45 (10) ◽  
pp. 1758-1770 ◽  
Author(s):  
Michael J. Vanni
Keyword(s):  
Introduced Species ◽  
Zooplankton Community ◽  
Zooplankton Species ◽  
Small Species ◽  
Daphnia Galeata ◽  
Resident Species ◽  
Large Herbivores ◽  
Fishless Lakes ◽  
Invertebrate Predators ◽  
Daphnia Galeata Mendotae

Two hypotheses have been proposed to explain the scarcity of small zooplankton species in fishless lakes, in which large zooplankton species dominate: (1) selective predation on small species by large invertebrate predators and (2) competitive suppression of small species by large herbivores. These hypotheses were tested at the Experimental Lakes Area (ELA) by introducing a large invertebrate predator, Chaoborus americanus, and a large herbivore, Daphnia catawba, both common in fishless ELA lakes, into a zooplankton community typical of ELA lakes with fish (small zooplankton species present). Chaoborus had much more of an impact than D. catawba on resident zooplankton, although both introduced species significantly reduced the abundance of some resident species. Daphnia galeata mendotae, the dominant species in the absence of introduced species, was reduced to virtual extinction by Chaoborus. The cladocerans Bosmina and Diaphanosoma, the copepods Diaptomus spp., and the rotifer Conochilus also were reduced in abundance by Chaoborus. Daphnia galeata mendotae and Bosmina were the only resident species consistently reduced in abundance by D. catawba. These results support current conceptual models that depict invertebrate predation as an important factor responsible for the relative scarcity of small zooplankton species in fishless lakes.

Periodicity of Egg Laying and Egg Age Distributions in Planktonic Cladocera

1984 ◽  
Vol 41 (3) ◽  
pp. 409-413 ◽  
Author(s):  
Alan J. Tessier
Keyword(s):  
Negative Correlation ◽  
Natural Populations ◽  
Egg Laying ◽  
Daphnia Galeata ◽  
Molt Cycle ◽  
Egg Development ◽  
Daphnia Species ◽  
Diel Cycles ◽  
Development Times ◽  
Daphnia Galeata Mendotae

In natural populations of planktonic Cladocera, I observed significant diel, molt cycle, and cohort periodicity of egg laying. Diel cycles of egg laying were pronounced in one population of Daphnia galeata mendotae; most females laid eggs only at dawn. There was a strongly negative correlation between diel egg laying cycles of coexisting Daphnia species. Egg laying in two Daphnia populations cycled with a period approximating the egg development times, suggesting a synchronization of individual molt cycles. Noncontiguous reproduction was characteristic of a population of Holopedium gibberum. Adults reproduced synchronously and then died; there was little overlap of generations.

scholarly journals Multiple habitat associations: the role of offsite habitat in determining onsite avian density and species richness

Ecography ◽  
2012 ◽  
Vol 35 (2) ◽  
pp. 134-145 ◽  
Author(s):  
Martin Dallimer ◽  
Andrew M. J. Skinner ◽  
Zoe G. Davies ◽  
Paul R. Armsworth ◽  
Kevin J. Gaston
Keyword(s):  
Species Richness ◽  
Habitat Associations
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