Molecular phylogeography of European Sciurus vulgaris: refuge within refugia?

The red squirrel (Sciurus vulgaris) is a well-known forest animal distributed all over Europe. Still, we are far from having a firm knowledge of the species' phylogeography. This study investigates the genetic differentiation of S. vulgaris across the species' Eurasian range, using sequence data from the mitochondrial DNA gene (D-loop, 252 base pairs, cytochrome b, 359 base pairs), and eight variable autosomal microsatellite loci genotyped for 236 individuals. The results reveal the presence of two main mitochondrial phylogroups. The first clade comprises the individuals from the region of Calabria in southern Italy, belonging to the subspecies S. v. meridionalis, while the second clade contains the remainder of the studied individuals. Bayesian analysis of microsatellite genotypes resulted in three main clusterings corresponding to the three S. vulgaris subspecies: infuscatus, meridionalis and fuscoater. Geographical distribution of mtDNA haplotypes and mismatch analysis suggest a common refugium for the red squirrel across most of its present range from which expansion happened rather rapidly. The genotype mixing of italicus with northern populations could be a residual of postglacial expansion. The lack of mixing between the Calabrian lineage and the rest of European red squirrel haplotypes can be seen as evidence for distinct histories throughout the Pleistocene. Calabrian mtDNA probably diverged in an ice age contraction and remained isolated from the neighbouring squirrel populations until very recent times.

Natural infection with two genotypes of Cryptosporidium in red squirrels (Sciurus vulgaris) in Italy.

We investigated the genotypes of Cryptosporidium infecting red squirrels (Sciurus vulgaris L.) in two areas of the Western Alps in Italy. Examination of 141 faecal samples from 70 red squirrels revealed oocysts of Cryptosporidium in 17 animals (24.3%). Based on 18S rRNA gene sequencing, two genotypes of Cryptosporidium species were found: 15 squirrels were positive for the Cryptosporidium ferret genotype and 2 for the Cryptosporidium chipmunk genotype I. The occurrence and intensity of Cryptosporidium infection did not differ between the study areas or sex. More than 85% of the positive animals were adults; however no difference was found between Cryptosporidium infection in the juvenile and adult age groups. Oocysts of the Cryptosporidium ferret genotype measured 5.5 +/- 0.3 x 5.2 +/- 0.2 microm (shape index 1.06) and the Cryptosporidium chipmunk genotype I 5.8 +/- 0.3 x 5.4 +/- 0.3 microm (shape index 1.07). Neonatal and adult CD1 and BABL/c mice inoculated with 1 x 10(3) fresh oocysts of both genotypes did not produce detectable infection.

Anticipatory reproduction and population growth in seed predators.

Mast seeding, the intermittent, synchronous production of large seed crops by a population of plants, is a well-known example of resource pulses that create lagged responses in successive trophic levels of ecological communities. These lags arise because seed predators are thought capable of increasing reproduction and population size only after the resource pulse is available for consumption. The resulting satiation of predators is a widely cited explanation for the evolution of masting. Our study shows that both American and Eurasian tree squirrels anticipate resource pulses and increase reproductive output before a masting event, thereby increasing population size in synchrony with the resource pulse and eliminating the population lag thought to be universal in resource pulse systems.