An Intergeneric Hybrid Between Historically Isolated Temperate and Tropical Jays Following Recent Range Expansion

Abstract

Shifts in species' ranges are creating novel ecosystems and previously unobserved species interactions. Documenting and understanding these novel interactions between species is an emergent priority of global ecological importance. We report a wild hybridization resulting from recent range expansion: a hybrid between Green Jay (Cyanocorax yncas) and Blue Jay (Cyanocitta cristata), charismatic and historically allopatric species whose ranges newly overlap in Texas. Morphological and genetic evidence indicate the hybrid individual resulted from the pairing of a female Green Jay and a male Blue Jay. Hybridization between these species is remarkable across vertebrate species, as such events typically occur between recently diverged populations, whereas the most recent common ancestor to Blue and Green Jays is estimated to have lived at least 7 million years ago. We believe this hybridization event joins a growing list of increasingly unexpected outcomes of contemporaneous range expansions fueled by anthropogenic global change. As birds are keystone species in ecological webs and reservoirs for zoonotic diseases, the creation of unique genomic contexts resulting from climate-driven hybridization is a phenomenon of both scientific and practical importance.

Keywords: anthropogenic hybridization; climate change; evolution; range shifts.

FIGURE 1

(a) Blue Jay by Travis Maher (ML578309451). Cornell Lab of Ornithology, Macaulay Library. (b) Hybrid Jay by Brian R. Stokes. (c) Green Jay by Dan O'Brien (ML390361871). Cornell Lab of Ornithology, Macaulay Library.

FIGURE 2

(a) Visualization of a representative 16S rRNA region from the MAFFT alignment. The hybrid mitochondrial sequence (“Hybrid MT,” top) is shown explicitly. For the other taxa, bases matching the hybrid are rendered as dots; non‐matching bases are shown as letters. Masked positions are “N,” and indels are shown as “–”. Colors denote base identity at variant positions. (b) Distribution of top BLASTN hits for 17,654 phase blocks from scaffold #5 (≥ 97% identity). Bars indicate matches to C. yncas (green), C. cristata (blue), C. stelleri (blue), and equal top hit ( C. cristata / C. stelleri )—phase blocks with equal bit score between the two species (blue), and other (gray). Other represents the additional candidate species and any combination of score ties aside from C. cristata / C. stelleri . Percentages are relative to all blocks; the bracket indicates the cumulative percentage for C. cristata  +  C. stelleri (47.8%). (c) Triangle plot of hybrid index values. Points represent C. yncas (green), C. cristata (blue), and the hybrid (orange). Placement of the hybrid near a 1.0 interclass homozygosity and 0.50 hybrid index strongly supports the hybrid to be a F1 hybrid between C. yncas and C. cristata . (d) Per‐site heterozygosity at the nuclear ACTB gene. Points show natural and “synthetic” hybrids (teal), C. cristata (blue), four C. yncas samples (green), and other candidate species (black). Points are horizontally jittered to reduce overlap; the x‐position has no meaning.

FIGURE 3

(a) Region of study. Red square delineates extent of maps for panels b and d. (b) Green Jay and Blue Jay occurrences, black points indicate localities of recorded co‐occurrence. (c) eBird recordings of Green and Blue Jay co‐occurrences per year. Gray bars are the raw count of all checklists each year which record a co‐occurrence. (d) Green and Blue Jay climate niche distributions based on MaxEnt using climate norms of 1991–2020 and climate norms for ssp245 emission projection for 2041–2060. Light blue and green areas represent current predicted climatic niches of Blue and Green Jay respectively. Orange area represents current predicted climatic niche overlap between both species. Blue and green lines represent boundary of future projected distributions.