H A Orr

..melanogaster and autosomal gene(s) from D. melanogaster's sister species...

..These findings support previous claims that hybrid embryonic and larval lethalities are genetically distinct and suggest that Hmr(mel) is at least one of the proximate causes of hybrid larval inviability...

..Although my answer is essentially identical to one offered previously, my path to it differs somewhat from previous approaches. Some may find this new approach easier to intuit...

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..We discuss the possibility that hybrid sterility in this paradigmatic case of incipient speciation is caused by segregation distortion...

..I also discuss the challenges that face contemporary theories of adaptation...

..I conclude that the probability of parallel evolution under natural selection is nearly twice as large as that under neutrality...

..Finally, I review recent work in Drosophila pseudoobscura on the possible role of meiotic drive in the evolution of the genes that cause postzygotic isolation...

..I consider possible reasons for this congruence. I also emphasize what predictions do and, as important, do not follow from these models...

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..I show that all previous results characterizing single steps in adaptation in the mutational landscape model hold at least approximately on correlated landscapes in the block model; many entire-walk results, however, do not...

..These surprises, and others like them, suggest that evolutionary biologists may understand less about the genetic basis of speciation than seemed likely a few years ago...

..Our results show that adaptation to such environmental challenges can be difficult when relying on new mutations at one or a few loci, and populations will often decline to extinction...

..I also review the empirical study of fitness, emphasizing approaches that take advantage of recent genetic and genomic data, and I highlight important unresolved problems in understanding fitness...

..Molecular evolutionary study of the genes causing reproductive isolation may represent an important new phase in the study of speciation...

..autosomal loci. Last, we suggest a test to determine whether adaptation used new mutations or previously deleterious alleles from the standing genetic variation...

..I show that these findings are reasonably robust to deviations from several assumptions. I further show that one can back calculate the mean size of new beneficial mutations from the observed mean size of fixed beneficial mutations...

..Put differently, evolution must try out at least e wild-type sequences during an average bout of adaptation...

..Last, I show that adaptation by natural selection behaves in several respects as the average of two idealized forms of adaptation, perfect and random...

..Our analyses of data from Drosophila and Bombina suggest that p is generally very small, on the order of 10(-6) or less...

..Indeed, a maximum likelihood analysis suggests that roughly 15 hybrid male steriles separate the Bogota and USA subspecies. Only a subset of these would act in F1 hybrids...

..In the course of this work, I derive an approximation to the probability of fixation of a favorable mutation in an asexual genome or nonrecombining chromosome region in which both favorable and deleterious mutations occur...

..Rejection of the null hypothesis implies a role for directional natural selection. This test is applicable to any character in any organism in which QTL analysis can be performed...

..This precludes the development of a DMI, which requires different substitutions in the two populations...

..melanogaster males. Genetic analysis of the difference between D. simulans strains that produce many versus few hybrid females shows that recovery of hybrid females depends on autosomal, maternally acting gene(s)...

..We also consider the probability of parallel adaptation and the proportion of the total increase in fitness caused by the first substitution. Our key assumption is that there is no epistasis among beneficial mutations...

..Indeed, it is reasonably clear that the chain of implication sometimes primarily ran in the opposite direction-from, for instance, economics and political theory to Darwinism...

..This segregation distorter gene is essential for hybrid sterility, a strong reproductive barrier between these young taxa. Our results suggest that genetic conflict may be an important evolutionary force in speciation...

..simulans lineage. Because of this transposition, a fraction of hybrids completely lack JYAlpha and are sterile, representing reproductive isolation without sequence evolution...

..We find that some of these statistics are surprisingly similar between sexuals and asexuals. These results highlight the importance of the choice of substitution model in assessing the Fisher-Muller advantage of sex...

..autosomal diversity is reduced by hitchhiking under a broad range of conditions, but when there is no recombination in males, as in Drosophila, the required conditions are considerably more restrictive...

..These results show that a lethal hybrid incompatibility has evolved as a by-product of adaptive protein evolution...

..The results show that adaptation towards a fixed optimum is generally characterized by an exponential effects trend...

..The present results also suggest that one can define an effective number of dimensions characterizing an adapting species...

..A review of Philip Kitcher's book, Living with Darwinism: evolution, design, and the future of faith...

..Primarily a review of Richard Dawkins' book, The God delusion (Boston: Houghton Mifflin, 2006)...

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..Our long-term goal is to understand how animal species, including humans, arise by uncovering the genetic causes of speciation. ..

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