The cave environment is consistently radically different than the surface environment because it lacks light, and animals adapting to cave life are subject to strong selective forces much different than those experienced by their ancestors who evolved in the presence of light. As such, their divergence from surface ancestors and eventual speciation is likely to be driven by the shift in ecology. We report here that hybrids between cave and surface Astyanax mexicanus fishes produce offspring with allelic frequencies that differ significantly from Mendelian expectations both for transmission ratios and for independent assortment of unlinked markers. Comparison of allelic content of DNA from fin clips and sperm pools show that the transmission ratio distortion likely occurs during spermatogenesis. Departures from expectations of independent assortment are essentially epistatic phenomena generating linkage disequilibrium. A novel analysis of the epistatic interactions reveals an apparent network of interactions among genes known or suspected to be involved in cave adaptation, implying that the epistasis arose as a “by product” of the divergence due to cave adaptation.
The term reflexive is applied by traditional grammarians to an event or situation that “reflects” (“rebounds”) upon its initiator, typically when some internal argument of the predicate co-refers with its subject (e.g., English John pinched himself or John saw himself in the mirror). In a slightly broader sense, reflexivity is a type of interpretation wherein two arguments of the same predicate co-refer, regardless of their structural positions in their clause; thus, I spoke to John about himself is viewed as semantically reflexive. From a cross-linguistic perspective, expressions used to express reflexive interpretations—reflexivity markers—typically include nominals denoting the human person or body, or inalienable parts of it (for example, Haitian Jan renyen tèt li, lit. “John hates his head” = “John hates himself”), and specialized reflexive pronouns (e.g., English himself, Russian sebja: Ivan ljubit sebja “Ivan loves himself”), which may grammaticalize into verbal affixes deriving reflexive verbs (for example, Russian myt’-sja, French se laver “to wash (oneself)”). Finally, reflexive interpretations, as defined above, may also be available with some ordinary personal pronouns (e.g., French Jean est fier de lui = “John is proud of him” or “of himself”). A crucial cross-linguistic generalization brought out by works on reflexivity is that the forms that may correlate in some contexts with reflexive readings, in the narrower sense defined above, are often associated, in other contexts, with interpretive effects distinct from reflexivity, such as valency or aspectual changes, intensification, subject affectedness, or subjective discourse perspective. Two approaches may thus be considered for the study of reflexives and reflexivity in one or several languages: (i) the research may focus on the expression of reflexivity in its narrowest semantic sense: how are reflexive interpretations signaled in a given language or in natural languages? (ii) the research may aim at identifying and linking together the different uses of forms available, among other things, as reflexivity markers. Option (i) leads us to consider reflexivity as a special case of co-referential or anaphoric relations. Option (ii) leads us to consider reflexivity as one among a set of semantic effects associated with a common “reflexive” morpology, and to try and understand how these different effects can arise from the same forms.
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