scholarly journals Bill size variation in northern cardinals associated with anthropogenic drivers across North America

2018 ◽  
Vol 8 (10) ◽  
pp. 4841-4851 ◽  
Author(s):  
Colleen R. Miller ◽  
Christopher E. Latimer ◽  
Benjamin Zuckerberg
Keyword(s):  
North America ◽  
Size Variation ◽  
Northern Cardinals ◽  
Anthropogenic Drivers

scholarly journals Testing Equid Body Mass Estimate Equations on Modern Zebras—With Implications to Understanding the Relationship of Body Size, Diet, and Habitats of Equus in the Pleistocene of Europe

2021 ◽  
Vol 9 ◽  
Author(s):  
Juha Saarinen ◽  
Omar Cirilli ◽  
Flavia Strani ◽  
Keiko Meshida ◽  
Raymond L. Bernor
Keyword(s):  
Body Size ◽  
North America ◽  
Body Mass ◽  
Size Variation ◽  
Mass Range ◽  
The Body ◽  
Mass Estimation ◽  
Body Size Variation ◽  
Estimation Equations ◽  
Body Mass Estimation

The monodactyl horses of the genus Equus originated in North America during the Pliocene, and from the beginning of the Pleistocene, they have been an essential part of the large ungulate communities of Europe, North America and Africa. Understanding how body size of Equus species evolved and varied in relation to changes in environments and diet thus forms an important part of understanding the dynamics of ungulate body size variation in relation to Pleistocene paleoenvironmental changes. Here we test previously published body mass estimation equations for the family Equidae by investigating how accurately different skeletal and dental measurements estimate the mean body mass (and body mass range) reported for extant Grevy's zebra (Equus grevyi) and Burchell's zebra (Equus quagga). Based on these tests and information on how frequently skeletal elements occur in the fossil record, we construct a hierarchy of best practices for the selection of body mass estimation equations in Equus. As a case study, we explore body size variation in Pleistocene European Equus paleopopulations in relation to diet and vegetation structure in their paleoenvironments. We show a relationship between diet and body size in Equus: very large-sized species tend to have more browse-dominated diets than small and medium-sized species, and paleovegetation proxies indicate on average more open and grass-rich paleoenvironments for small-sized, grazing species of Equus. When more than one species of Equus co-occur sympatrically, the larger species tend to be less abundant and have more browse-dominated diets than the smaller species. We suggest that body size variation in Pleistocene Equus was driven by a combined effect of resource quality and availability, partitioning of habitats and resources between species, and the effect of environmental openness and group size on the body size of individuals.

Mating Within the Meiotic Tetrad and the Maintenance of Genomic Heterozygosity

Genetics ◽  
2004 ◽  
Vol 166 (4) ◽  
pp. 1751-1759 ◽  
Author(s):  
Michael E Hood ◽  
Janis Antonovics
Keyword(s):  
North America ◽  
Meiotic Division ◽  
Genetic Load ◽  
Size Variation ◽  
Linkage Groups ◽  
Tetrad Analysis ◽  
Linear Tetrad ◽  
Pcr Products ◽  
Dynamic Genome ◽  
Diverse Groups

Abstract Mating among the products of a single meiosis (automixis or meiotic parthenogenesis) is found in diverse groups of plant, animal, and fungal taxa. Restoration of the diploid stage is often strictly controlled and brings together products separated at the first meiotic division. Despite apparent similarities to diploid selfing, the theoretical prediction is that heterozygosity should be maintained on all chromosomes when it is linked to the centromeres and thus also segregates at the first meiotic division. Using the fungus Microbotryum, we directly test this prediction by linear tetrad analysis. The patterns of meiotic segregation for chromosome size variation (electrophoretic karyotypes) and PCR products (AFLP procedures) were determined for Microbotryum lineages native to North America and Europe. Our data reveal a surprisingly dynamic genome that is rich in heterozygosity and where size-dimorphic autosomes are common. The genetic variation agrees with the prediction of centromere-linked heterozygosity. This was observed to the greatest extent in the lineage of Microbotryum native to North America where there was consistent first-division segregation and independent assortment of multiple linkage groups. The data also show properties that distinguish the fungal sex chromosomes from the autosomes in both lineages of Microbotryum. We describe a scenario where the mating system of automixis with first-division restitution is the result of feedback mechanisms to control exposure of genetic load.

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