RESUMO
Microorganism communities can shape host phenotype evolution but are often comprised of thousands of taxa with varied impact on hosts. Identification of taxa influencing host evolution relies on first describing microorganism communities and acquisition routes. Keratinolytic (keratin-degrading) microorganisms are hypothesized to be abundant in saltmarsh sediments and to contribute to plumage evolution in saltmarsh-adapted sparrows. Metabarcoding was used to describe plumage bacterial (16S rRNA) and fungal (ITS) communities in three sparrow species endemic to North America's Atlantic coast saltmarshes. Results describe limited within-species variability and moderate host species-level patterns in microorganism diversity and community composition. A small percentage of overall microorganism diversity was comprised of potentially keratinolytic microorganisms, warranting further functional studies. Distinctions between plumage and saltmarsh sediment bacteria, but not fungal, communities were detected, suggesting multiple bacterial acquisition routes and/or vertebrate host specialization. This research lays groundwork for future testing of causal links between microorganisms and avian host evolution.
RESUMO
Saltmarsh (Ammospiza caudacuta) and Nelson's (A. nelsoni) sparrows are sister taxa that breed in tidal marshes along the coast of the Northeastern United States and Canada. The Saltmarsh Sparrow breeds from mid-coast Maine south to Virginia, while the Acadian Nelson's Sparrow breeds from the Canadian maritime provinces south to northern Massachusetts. Here, we present three extralimital observations of breeding Saltmarsh (n = 2) and Nelson's (n = 1) sparrows. In 2021 and 2022, we observed Saltmarsh Sparrow females attending nests at Mendall Marsh, ME, and Milbridge, ME, respectively, approximately 60 and 110 km beyond the documented northern extent of the Saltmarsh Sparrow breeding range. In 2022, we observed a breeding-condition male Nelson's sparrow singing in the upriver portion of a marsh on Cape Cod, Massachusetts, approximately 115 km beyond the previously documented southern extent of the Nelson's Sparrow breeding range. We confirmed morphological species identification using a panel of microsatellite DNA loci. Due to both the well-documented population declines of these species in the region and the intensity of sampling effort undertaken in recent years, we suggest that these observations likely are not indicative of range expansion. However, they do indicate that these 2 taxa have the capacity to use and successfully reproduce in marshes well beyond their established breeding limits. Our findings provide novel insight into the potential for these taxa to occur and successfully breed outside their documented breeding ranges. Given increased interest in their conservation, these results support the idea that management actions aimed at creating or maintaining nesting habitat across both species ranges could benefit both taxa.
RESUMO
The necromenic nematode Pristionchus entomophagus has been frequently found in nests of the invasive European ant Myrmica rubra in coastal Maine, United States, and may contribute to ant mortality and collapse of colonies by transferring environmental bacteria. Paenibacillus and several other bacterial species were found in the digestive tracts of nematodes harvested from collapsed ant colonies. Serratia marcescens, Serratia nematodiphila, and Pseudomonas fluorescens were collected from the hemolymph of nematode-infected wax moth (Galleria mellonella) larvae. Virulence against waxworms varied by the site of origin of the nematodes. In adult nematodes, bacteria were highly concentrated in the digestive tract with none observed on the cuticle. In contrast, juveniles had more on the cuticle than in the digestive tract. Host species was the primary factor affecting bacterial community profiles, but Spiroplasma sp. and Serratia marcescens sequences were shared across ants, nematodes, and nematode-exposed G. mellonella larvae.
