The rapid expansion of road networks has reduced connectivity among populations of flora and fauna. The resulting isolation is assumed to increase population extinction rates, in part because of the loss of genetic diversity. However, there are few cases where loss of genetic diversity has been linked directly to roads or other barriers. We analysed the effects of such barriers on connectivity and genetic diversity of 27 populations of Ovis canadensis nelsoni (desert bighorn sheep). We used partial Mantel tests, multiple linear regression and coalescent simulations to infer changes in gene flow and diversity of nuclear and mitochondrial DNA markers. Our findings link a rapid reduction in genetic diversity (up to 15%) to as few as 40 years of anthropogenic isolation. Interstate highways, canals and developed areas, where present, have apparently eliminated gene flow. These results suggest that anthropogenic barriers constitute a severe threat to the persistence of naturally fragmented populations.

PALSBOLL, P. J., VADER, A., BAKKE, I., and RAAFAT EL-GEWELY, M. 1992. Determination of gender in cetaceans by the polymerase chain reaction. Can. J. Zool. 70: 2 166 -2170. We determined the gender of a variety of cetacean species, including both ondotocetes and mysticetes, using the polymerase chain reaction for amplification of the sex chromosome specific regions ZFYIZFX and SRY. This quick and simple method requires extremely small amounts of tissue, and therefore allows gender to be determined from skin biopsies taken from freeranging specimens. In the fin whale, Balaenoptera physalus, no gender-specific bands were observed when the ZFYIZFX system was used, but.when the SRY system was used, sex was accurately determined. Previous studies in other mammals have also shown the SRY system to be more reliable in sex determination. We therefore recommend amplification of the SRY region alone or in parallel with the ZFYIZFX regions, as described here, as a test for gender in cetaceans and other mammals. PALSBOLL, P. J., VADER, A., BAKKE, I., et RAAFAT EL-GEWELY, M. 1992. Determination of gender in cetaceans by the polymerase chain reaction. Can. J. Zool. 70 : 2 166-2170. Nous avons dCterminC le sexe chez un bon nombre d'espkces de cCtacCs en utilisant la rCaction de la chaine des polymCrases pour mettre en Cvidence les rCgions spkcifiques ZFYIZFX et SRY des chromosomes sexuels. Les espkces examinCes appartenaient aux odontocktes aussi bien qu'aux mysticktes. Cette mkthode rapide et simple ne requiert que des quantitCs minimes de tissus et permet donc la dktermination du sexe a partir de biopsies de la peau prClevCes chez des individus libres. Chez le Rorqual commun, Balaenoptera physalus, aucune bande spkcifique au sexe n'a Ct C observCe a l'utilisation du systkme ZFYIZFX, mais le systkme SRY a permis de dkterminer le sexe avec prCcision. Des Ctudes antkrieures d'autres mammifkres avaient dCja dCmontrC que le systkme SRY Ctait plus exact. Nous recommandons donc I'amplification de la rCgion SRY, ou son utilisation conjointe avec l'amplification des rCgions ZFYIZFX, comme mCthode de dktermination du sexe chez les cCtacCs et chez d'autres mammifkres.[Traduit par la rCdaction]

We developed 31 novel, polymorphic microsatellite loci in the marbled murrelet (Brachyramphus marmoratus), a critically endangered seabird. Variability was tested on 15 individuals from the Santa Cruz, California population, with each locus characterized by two to 12 alleles. Observed levels of heterozygosity ranged from 0.13 to 0.93. These loci provide a valuable means of assessing the population structure and demographic parameters of this species, which may be critical to its conservation across a fragmented habitat.

Hyalopterus pruni is an invasive aphid pest in California. To study the population biology of this pest both in California and its native Mediterranean region, we have developed 11 di‐ and tri‐nucleotide repeat microsatellite markers. Each locus amplified in individuals representing the full range of geographical regions and host plants where Hyalopterus is found. Polymorphism was high, ranging from six to 22 alleles per locus in the individuals screened. These loci represent the first microsatellites developed for Hyalopterus and they should be of great value in studying the invasion biology and population structure of this insect pest.