Substantial genetic differentiation, as great as among species, exists between populations of Drosophila melanogaster inhabiting opposite slopes of a small canyon. Previous work has shown that prezygotic sexual isolation and numerous differences in stressrelated phenotypes have evolved between D. melanogaster populations in ''Evolution Canyon,'' Israel, in which slopes 100 -400 m apart differ dramatically in aridity, solar radiation, and associated vegetation. Because the canyon's width is well within flies' dispersal capabilities, we examined genetic changes associated with local adaptation and incipient speciation in the absence of geographical isolation. Here we report remarkable genetic differentiation of microsatellites and divergence in the regulatory region of hsp70Ba which encodes the major inducible heat shock protein of Drosophila, in the two populations. Additionally, an analysis of microsatellites suggests a limited exchange of migrants and lack of recent population bottlenecks. We hypothesize that adaptation to the contrasting microclimates overwhelms gene flow and is responsible for the genetic and phenotypic divergence between the populations.thermotolerance ͉ hsp70 ͉ P element ͉ genetic distance ͉ premating isolation A recurrent issue in evolutionary biology is the amount of genetic isolation required for incipient species to diverge from a common ancestor, with geographical isolation and its impact on gene flow a prominent source of genetic isolation (1-3). Indeed, Mayr (4, 5) has stressed repeatedly the role of geographical separation of populations in the origin of species. Although several evolutionary mechanisms may give rise to new species in contiguous populations, in the absence of these mechanisms gene flow would seem to exert a potent homogenizing force on incipient isolates (6, 7). Nonetheless, profound adaptive radiation of species can occur without large scale geographical isolation, as in the Ͼ450 species of haplochromine cichlids from Lake Malawi (8-11). Critics reasonably may dispute that such cases are evidence for speciation without geographic separation, because in Lake Malawi (Ϸ500-km long) and other such instances, potential spatial and ecological separation are large relative to the dispersal abilities of the speciating populations.Accordingly, we have investigated ''Evolution Canyon,'' Israel, where Drosophila melanogaster occurs on north-and southfacing slopes with greatly differing climatic regimes and in the intervening region; the slopes are 400 m apart at the top and 100 m apart at the bottom (12-14). Although adult Drosophila can traverse several kilometers in a single day (15), populations on each slope have diverged in body size, heat and desiccation tolerance, oviposition thermal preference, fluctuating asymmetry, rates of mutation and recombination, and mate preference (16-18). We thus ask: Have the populations likewise diverged genetically according to microsatellite markers and a candidate gene strongly linked to resistance to environmental stress? Is this diver...

The strong microscale interslope environmental di¡erences in`Evolution Canyon' provide an excellent natural model for sympatric speciation. Our previous studies revealed signi¢cant slope-speci¢c di¡er-ences for a ¢tness complex of Drosophila. This complex involved either adaptation traits (tolerance to high temperature, di¡erent viability and longevity pattern) or behavioural di¡erentiation, manifested in habitat choice and non-random mating. This remarkable di¡erentiation has evolved despite a very small interslope distance (a few hundred metres only). Our hypothesis is that strong interslope microclimatic contrast caused di¡erential selection for ¢tness-related traits accompanied by behavioural di¡erentiation and reinforced by some sexual isolation, which started incipient speciation. Here we describe the results of a systematic analysis of sexual behaviour in a non-choice situation and several reproductive parameters of D. melanogaster populations from the opposite slopes of`Evolution Canyon'. The evidence indicates that: (i) mate choice derives from di¡erences in mating propensity and discrimination; (ii) females from the milder north-facing slope discriminate strongly against males of the opposite slope; (iii) both sexes of the south-facing slope display distinct reproductive and behavioural patterns with females showing increased fecundity, shorter time before remating and relatively higher receptivity, and males showing higher mating propensity. These patterns represent adaptive life strategies contributing to higher ¢tness.

The kidney glomerular filtration barrier (GFB) is enriched with heparan sulfate (HS) proteoglycans, which contribute to its permselectivity. The endoglycosidase heparanase cleaves HS and hence appears to be involved in the pathogenesis of kidney injury and glomerulonephritis. We have recently reported, nonetheless, that heparanase overexpression preserved glomerular structure and kidney function in an experimental model of Adriamycin-induced nephropathy. To elucidate mechanisms underlying heparanase function in podocytes—key GFB cells, we utilized a human podocyte cell line and transgenic mice overexpressing heparanase. Notably, podocytes overexpressing heparanase (H) demonstrated significantly higher survival rates and viability after exposure to Adriamycin or hydrogen peroxide, compared with mock-infected (V) podocytes. Immunofluorescence staining of kidney cryo-sections and cultured H and V podocytes as well as immunoblotting of proteins extracted from cultured cells, revealed that exposure to toxic injury resulted in a significant increase in autophagic flux in H podocytes, which was reversed by the heparanase inhibitor, Roneparstat (SST0001). Heparanase overexpression was also associated with substantial transcriptional upregulation of autophagy genes BCN1, ATG5, and ATG12, following Adriamycin treatment. Moreover, cleaved caspase-3 was attenuated in H podocytes exposed to Adriamycin, indicating lower apoptotic cell death in H vs. V podocytes. Collectively, these findings suggest that in podocytes, elevated levels of heparanase promote cytoprotection.