Inbreeding depression depends on the body size and environmental conditions in a threatened songbird, the aquatic warblerAcrocephalus paludicola

Abstract

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 warblerAcrocephalus 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 index (SMI) on days 2, 5 and 9 post-hatch. Nestling tarsus was negatively related to father F on days 5 and 9, and less strongly to mother F on day 5, but not to nestling F. The mother F effects on nestling tarsus and SMI were more negative in higher temperatures and the father F was more negatively related to nestling tarsus on later laying dates. The nestling F was more negatively associated with SMI under lower temperatures and rainfall. Neither the parental, nor the chick F effects on tarsus and SMI were found to interact with nestling sex, brood size and prey abundance. The inbreeding load on the adult male long-term survival rates was low for the mean covariates under study, but the decrease in fitness in the most inbred individuals, relative to the least inbred ones was high (~76%) for the breeding success in small-tarsus males and moderate (~10%) for the clutch size in small-tarsus females. We conclude that in the aquatic warbler (1) while inbreeding depression for the average phenotypic and environmental variables studied is not supported, (2) it is moderate to strong in small-bodied adults, (3) for chick condition, it depends on the weather, and (4) parental inbreeding effects could carry over to the next generation.

Agonistic song rate positively correlates with male breeding success and avian malaria infection in a promiscuous songbird with female-only parental care

“…Data collected for the purpose of this study was part of a larger project (Kubacka et al 2024), in which, between 2017-2019, in total 174 adult males were caught with mist-nets. Each bird was marked with unique metal and colour rings, and blood-sampled by puncturing the brachial vein with a sterile needle and collecting approx.…”

“…3RAD (Bayona-Vásquez et al 2019;Glenn et al 2019). We followed the methods applied in the larger study (Kubacka et al 2024). Briefly, DNA was isolated with the Xpure™ Blood mini kit (A&A Biotechnology, Poland).…”

“…The library was sequenced with the Illumina MiSeq V3 at 600 cycles and achieved a total of 3.6 M reads per sample. We then constructed 3RAD 'population' libraries (Bayona-Vásquez et al 2019), following the protocol described above, consisting of all the samples collected in the other project (Kubacka et al 2024). The population libraries (nine in total, prepared in three batches) were sequenced with llumina NextSeq MidOutput 300 cycles and Illumina NovaSeq 6000 300 cycles with 15% of PhiX.…”

“…The raw sequencing data was processed as described elsewhere (Kubacka et al 2024). In short, we first removed PhiX genome reads, trimmed the adapters with the Cutadapt software (Martin 2011) and demultiplexed the sequences with FLEXBAR (Dodt et al 2012).…”

“…We then assigned paternity with the Cervus programme (Kalinowski et al 2007), running the allele frequency analysis, parentage analysis simulation and paternity analysis given known mother. We ran Cervus on the full dataset (Kubacka et al 2024), of which the song-recorded males were part. In the parentage analysis simulation, we assumed 100,000 offspring, 440 as the average number of candidate fathers per offspring, 0.4 as the proportion of candidate fathers sampled and 88 as the minimum number of typed loci.…”