Global evolutionary strategies across life caused by shared ecological stress: Fact or fancy?

Abstract

Cardinal evolutionary problems await resolution and critical testing. Evolution Canyon in Mount Carmel, Israel, is an excellent microcosmic model system of sharp physical (microclimatic) and biotic interslope contrasts, enabling critical tests in nature relevant to macrocosm evolution. We genotypically and phenotypically tested two phylogenetically and biologically very distant organisms there, the sessile, predominantly inbreeding plant wild barley, Hordeum spontaneum, and the vagile and outbreeding drosophilid fruit fly, Zaprionus tuberculatus, a very recent colonizer of Israel. The genomes of these extremely different organisms were tested by Amplified Fragment Length Polymorphism (AFLP) for genetic diversity at 357 and 345 genetic markers (presumed gene loci), respectively. We found in both organisms parallel genetic patterns reflecting the canyon's opposite slopes, with significantly higher genetic polymorphism in subpopulations on the ecologically more stressful African (warmer and drier) south-facing slope. Likewise, both organisms displayed higher viability in parallel in response to severe drought stress on the more arid and climatically fluctuating African SFS. Our results suggest: (i) microclimatic selection is the major evolutionary interslope's fast-acting diverging force upon genotypes and phenotypes, overriding migration and drift, and (ii) ecological stress can generate global-scale adaptive evolutionary genome and phenome strategies, at both micro and macroscales, reinforcing homeostasis and fitness and suggesting continuity between micro and macroevolution.