Inbreeding depression depends on the body size and environmental conditions in a threatened songbird, the aquatic warbler Acrocephalus paludicola
While inbreeding is known to affect individual fitness and thus extinction risk in populations, studies have under-represented non-model species of conservation concern and rarely sought conditionality of inbreeding depression. Here, using SNPs identified with RAD-seq, we determined inbreeding depression in a threatened passerine, the aquatic warbler Acrocephalus paludicola , and whether its magnitude depends on phenotypic and environmental factors. We found no support for an association of the inbreeding coefficient (F) with the long-term return rate to breeding grounds and seasonal breeding success in adult males, and with the clutch size, hatch failures, nestling mortality, and fledged brood size in adult females. However, the F of adults with small tarsi (a proxy for structural body size) was negatively associated with the seasonal breeding success (in males) and clutch size (in females). We found no support for a relationship between nestling or parental F and nestling scaled-mass