Genetic diversity was analysed in brown trout Salmo trutta populations living in an area of central Italy using RFLP analysis of two mtDNA segments and of the nuclear locus LDH-C1*. The data indicated a genetic structure profoundly altered by repeated stockings with allochthonous material of Atlantic origin. In fact, four and 11 of the haplotypes detected were, respectively, identical or genetically very close to haplotypes found in Danish populations, the putative source of stocked brown trout. Furthermore, the LDH-C1*90 allele, typical of north-western Europe, was widespread among the samples studied. Nonetheless, four populations are characterized by a high frequency of both putative autochthonous haplotypes and the LDH-C1*100 allele, common in the Mediterranean basin. These populations, sampled in areas where S. trutta is documented historically, might represent a remnant of the species' indigenous biodiversity, showing the scope for improving the management of brown trout in central Italy. # 2004 The Fisheries Society of the British Isles

Squamate reptiles show a striking diversity in modes of sex determination, including both genetic (XY or ZW) and temperature-dependent sex determination systems. The genomes of only a handful of species have been sequenced, analyzed and assembled including the genome of Anolis carolinensis. Despite a high genome coverage, only macrochromosomes of A. carolinensis were assembled whereas the content of most microchromosomes remained unclear. Most of the Anolis species have homomorphic XY sex chromosome system. However, some species have large heteromorphic XY chromosomes (e.g., A. sagrei) and even multiple sex chromosomes systems (e.g. A. pogus), that were shown to be derived from fusions of the ancestral XY with microautosomes. We applied next generation sequencing of flow sorting-derived chromosome-specific DNA pools to characterize the content and composition of microchromosomes in A. carolinensis and A. sagrei. Comparative analysis of sequenced chromosome-specific DNA pools revealed that the A. sagrei XY sex chromosomes contain regions homologous to several microautosomes of A. carolinensis. We suggest that the sex chromosomes of A. sagrei are derived by fusions of the ancestral sex chromosome with three microautosomes and subsequent loss of some genetic content on the Y chromosome.

Anoles are a clade of iguanian lizards that underwent an extensive radiation between 125 and 65 million years ago. Their karyotypes show wide variation in diploid number spanning from 26 (Anolis evermanni) to 44 (A. insolitus). This chromosomal variation involves their sex chromosomes, ranging from simple systems (XX/XY), with heterochromosomes represented by either micro- or macrochromosomes, to multiple systems (XXXX/XXY). Here, for the first time, the homology relationships of sex chromosomes have been investigated in nine anole lizards at the whole chromosome level. Cross-species chromosome painting using sex chromosome paints from A. carolinensis, Ctenonotus pogus and Norops sagrei and gene mapping of X-linked genes demonstrated that the anole ancestral sex chromosome system constituted by microchromosomes is retained in all the species with the ancestral karyotype (2n = 36, 12 macro- and 24 microchromosomes). On the contrary, species with a derived karyotype, namely those belonging to genera Ctenonotus and Norops, show a series of rearrangements (fusions/fissions) involving autosomes/microchromosomes that led to the formation of their current sex chromosome systems. These results demonstrate that different autosomes were involved in translocations with sex chromosomes in closely related lineages of anole lizards and that several sequential microautosome/sex chromosome fusions lead to a remarkable increase in size of Norops sagrei sex chromosomes.

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The brown trout (Salmo trutta L.) is widely distributed all around Europe but its natural diversity is 19 threatened by massive stocking with Atlantic domestic strains. Describing the remaining natural genetic 20 diversity and the proportion of domestic hatchery strains in rivers is a prerequisite for smart conservation. 21 The high genetic diversity of brown trout populations around the Tyrrhenian Sea is well known. Use of 22 twelve microsatellites has allowed description of the natural genetic structure of populations and detection 23 of the consequences of stocking. Mitochondrial DNA control region sequences and the LDH-C1* gene 24 enabled placement of each population into one of the six mitochondrial and two allozymic known 25 2 evolutionary lineages. The Corsican populations showed low intra-population genetic diversity but an 26 exceptionally high level of inter-population differentiation. More southern Tyrrhenian regions exhibited 27 opposite pattern of diversity, partly due to the Atlantic domestic introgression. Globally, the natural 28 structure outlines two north-south clines: high inter-population differentiation and predominance of the 29 Adriatic lineage in the north, but lower inter-population differentiation and presence of the natural Atlantic 30 lineage in the south. In addition, the Tyrrhenian region is the contact zone between the widespread 31 Adriatic lineage and a local natural Atlantic lineage probably coming from North Africa through the Strait 32 of Gibraltar.