Inbreeding in the field: an experiment on root vole populations

We used a field experiment with replicate populations of a particular geographic race of root voles (Microtus oeconomus) with different degrees of inbreeding to test whether inbreeding effects were expressed in demographic parameters. This geographic race had been shown to exhibit reduced reproductive rates in the laboratory resulting from inbreeding depression. There were no effects of inbreeding on population growth rate or any demographic parameter. Inbred animals grew less than outbred animals early in the summer, but this had no demographic consequences. Our study is one of the few to compare the performance of the same species in the laboratory and in the field with respect to the extent of inbreeding depression. More such comparisons will be needed to determine whether inbreeding is detrimental more often in the field than in the laboratory.

Estimates of gene flow among populations, geographic races, and species in the Ipomopsis aggregata complex.

Interpopulational gene flow within a species can reduce population differentiation due to genetic drift, whereas genetic exchange among taxa can impede speciation. We used allozyme data to estimate gene flow within and among geographic races and species of perennial herbs in the Ipomopsis aggregata complex (Polemoniaceae). Estimates of interpopulational gene flow within taxa from two methods (F statistics and private alleles) were correlated with one another. Gene flow among populations within each geographic race (subspecies) of I. aggregata was relatively high (Nm greater than approximately 1.0). Gene flow was also high among populations of I. arizonica and among four northern populations of I. tenuituba. However, gene flow was low (Nm less than 1.0) for I. tenuituba when a population representing subsp. macrosiphon was included. This is consistent with previous findings that subsp. macrosiphon has had an independent origin and is reproductively, as well as geographically, isolated. A recently developed model, based on hierarchical F statistics, was employed to estimate genetic exchange among taxa. Gene flow estimates were generally high among races of I. aggregata (dNmrace greater than 1.0) but were low among subspecies of I. tenuituba (dNmrace less than 1.0). Consistent with morphological evidence, estimates of interspecific gene flow were moderate between I. aggregata and I. tenuituba, which hybridize in several areas. However, contrary to morphological evidence, we estimated relatively high levels of interspecific gene flow involving I. arizonica. Our results suggest that I. arizonica has hybridized with other species without the transfer of morphological traits.(ABSTRACT TRUNCATED AT 250 WORDS)

A Spiny Orb Weaver Spider, Gasteracantha cancriformis (Linnaeus) (Arachnida: Araneae: Araneidae)

One of the more colorful spiders in Florida is a spiny orb weaver, Gasteracantha cancriformis (Linnaeus) 1767. Although not as large as some of the other common orb weavers (e.g., Argiope, Levi 1968; Neoscona, Edwards 1984), the combination of color, shape, and web characteristics make G. cancriformis one of the most conspicuous of spiders. The colloquial name for this spider in parts of Florida is "crab spider", although it is not related to any of the families of spiders commonly called crab spiders, e.g., Thomisidoe. This species belongs to a pantropical genus which contains many species in the Old World. With the possible exception of the West Indian G. tetracantha (L.) (which may be only a geographic race), G. cancriformis is the only species of its genus to occur in the New World, ranging from the southern United States to northern Argentina (Levi 1978). The bite of this common species is not known to cause serious effects to humans. This document is EENY-167 (originally published as DPI Entomology Circular 308), one of the Featured Creatures series of the Entomology andNematology Department, Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida. Published: October 2000. EENY-167/IN324: Spiny Orb Weaver Spider, Gasteracantha cancriformis (Linnaeus) (Arachnida: Araneae: Araneidae) (ufl.edu)

The North American Species of Diathrausta Lederer (Lepidoptera: Pyralidae)

Dyar (1913) listed Diathrausta reconditalis (Walker) as a “form” of the South American D. nerinalis (Walker) and described as new the “form” harlequinalis from Arizona. From the context it is evident that in that paper Dyar used “form” as equivalent to geographic race, and the form names he proposed there can accordingly be treated as valid trinomina. Haimbach (1915), apparently in ignorance of Dyar's paper, described Diathrausta montana from Colorado. This was sunk by Barnes and McDunnough (1917) as a synonym of harlequinalis. Barnes and McDunnough listed harlequinalis as a geographical race of reconditalis, but did not follow Dyar in uniting these with nerinalis.