Genotypic and phenotypic divergence of rodents (Acomys cahirinus and Apodemus mystacinus) at "Evolution Canyon": Micro- and macroscale parallelism

Genetic allozyme and RAPD diversities were examined for ecological-genetic patterns in two rodents, the spiny-mouse Acomys cahirinus (Desmarest, 1819) and woodmouse Apodemus mystacinus (Danford and Alston, 1877), from the ecologically contrasting opposite slopes of the Lower Nahal Oren microsite, Mt. Carmel, Israel, designated by us "Evolution Canyon". Likewise, morphological measurements were compared. Samples of both rodent species were collected from six stations: 3 (upper, middle and lower) on the "tropical" xeric South-facing slope (SFS) and 3 on the opposite "temperate" mesic North-facing slope (NFS) which vary dramatically physically and biotically. Higher solar radiation on the SFS than on the NFS makes it warmer, drier, spatiotemporally more heterogeneous and climatically more fluctuating and stressful than the cooler and more humid NFS. Consequently, the SFS exhibits an open park forest representing an "African" savanna landscape, in sharp contrast with the "European" lush liveoak maquis forest. Inter- and intraslope allozyme, RAPD, and morphological divergence was found in both rodents. Local variation in solar radiation, temperature and aridity stress caused interslope and intraslope adaptive genotypic (proteins and DNA) and phenotypic (morphological, physiological and behavioural) differences paralleling regional patterns across Israel in Acomys and in northern and central Israel in Apodemus. This suggests that, at both the micro- and macroscales, diversifying natural (microclimate) selection appears to be the major evolutionary driving force causing inter- and primarily SFS intraslope adaptive genotypic and phenotypic divergence. "Evolution Canyon" proved in small rodents, as previously in other organisms, an optimal model for unravelling evolution in action across life and organization.