Apparent Townsend’s x Black-throated Green Warbler (\u3ci\u3eSetophaga townsendi x virens\u3c/i\u3e) hybrids in Kansas and Nebraska

The Townsend’s Warbler (Setophaga townsendi), Hermit Warbler (Setophaga occidentalis), Golden-cheeked Warbler (Setophaga chrysoparia), and Black-throated Green Warbler (Setophaga virens) are similar in appearance and vocalizations. Evaluation of mtDNA suggests that these four species diverged about 1 million years ago during the mid-Pleistocene (Lovette et al. 2010), at which time glaciation separated ancestral forms thus allowing for speciation (Morse and Poole 2020). Under the environmental conditions prevalent today, however, the breeding distribution of Townsend’s Warbler now overlaps to a limited extent with those of the Hermit and Black-throated Green Warblers, and hybridization occurs frequently in these contact zones. The contact zone between Townsend’s and Hermit Warblers in Oregon and Washington has been studied extensively (Wright et al. 2020) and several hybrid individuals have even strayed to the southern Great Plains. Recently for example, Townsend’s x Hermit Warblers were photographed in Hamilton Co., Kansas on 17 May 2014; Midland Co., Texas on 17 Sep 2017; Pueblo Co., Colorado from 10-11 Sep 2020; and in Roosevelt Co., New Mexico between 26 Sep and 4 Oct 2020 (eBird 2021)

Effective intra-S checkpoint responses to UVC in primary human melanocytes and melanoma cell lines

The objective of this study was to assess potential functional attenuation or inactivation of the intra-S checkpoint during melanoma development. Proliferating cultures of skin melanocytes, fibroblasts and melanoma cell lines were exposed to increasing fluences of UVC and intra-S checkpoint responses were quantified. Melanocytes displayed stereotypic intra-S checkpoint responses to UVC qualitatively and quantitatively equivalent to those previously demonstrated in skin fibroblasts. In comparison to fibroblasts, primary melanocytes displayed reduced UVC-induced inhibition of DNA strand growth and enhanced degradation of p21Waf1 after UVC, suggestive of enhanced bypass of UVC-induced DNA photoproducts. All nine melanoma cell lines examined, including those with activating mutations in BRAF or and NRAS oncogenes, also displayed proficiency in activation of the intra-S checkpoint in response to UVC irradiation. The results indicate that bypass of oncogene-induced senescence during melanoma development was not associated with inactivation of the intra-S checkpoint response to UVC-induced DNA replication stress