Temporal stability of the hybrid zone between Calocitta magpie‐jays revealed through comparison of museum specimens and iNaturalist photos

Abstract

Hybrid zones are natural experiments for the study of avian evolution. Hybrid zones can be dynamic, moving as species adjust to new climates and habitats, with unknown implications for species and speciation. There are relatively few studies that have comparable modern and historic sampling to assess change in hybrid zone location and width over time, and those studies have generally found mixed results, with many hybrid zones showing change over time, but others showing stability. The whitethroated magpie-jay (Calocitta formosa) and black-throated magpie-jay (Calocitta colliei) occur along the western coast of Mexico and Central America. The two species differ markedly in throat color and tail length, and prior observation suggests a narrow hybrid zone in southern Jalisco where individuals have mixed throat color. This study aims to assess the existence and temporal stability of this putative hybrid zone by comparing throat color between georeferenced historical museum specimens and modern photos from iNaturalist with precise locality information. Our results confirm the existence of a narrow hybrid zone in Jalisco, with modern throat scores gradually increasing from the parental ends of the cline toward the cline center in a sigmoidal curve characteristic of hybrid zones. Our temporal comparison suggests that the hybrid zone has not shifted its position between historical (pre-1973) and modern (post-2005) time periods-a surprising result given the grand scale of habitat change to the western Mexican lowlands during this time. An anomalous pocket of white-throated individuals in the northern range of the black-throated magpie-jay hints at the possibility of prehistorical long-distance introduction. Future genomic data will help disentangle the evolutionary history of these lineages and better characterize how secondary contact is affecting both the DNA and the phenotype of these species.

Hybrid zones of Natrix helvetica and N. natrix: Phenotype data from iNaturalist and genetics reveal concordant clines and the value of species-diagnostic morphological traits

“…The present study is another example indicating that georeferenced photos from iNaturalist and similar Citizen Science platforms can provide valuable morphological data for research and may also enhance our knowledge of the distribution of the depicted taxa or hybrid zones (e.g., Fritz and Ihlow 2022;Pizarro et al 2023;Storniolo et al 2023). In this vein, the iNaturalist records from northwestern Germany, where grass snakes are rare, may help to clarify their taxonomic identity.…”

Environmental colour pattern variation in Mediterranean Podarcis

“…These images were taken from iNaturalist [ 45 ], which contains thousands of georeferenced photographs with their level of spatial error. These data are reliable for studies on the composition of faunal assemblages and species colouration [ 46 – 48 ]. However, given the heterogeneity in the quality of the images, those that did not meet the following minimum requirements were discarded: (1) the quality of the image had to enable verification of taxonomic identities; (2) the colour image could not show extremely low or high light; (3) the colour image could not be blurry or grossly pixelated (e.g., the small dorsal scales had to be distinguished); (4) the colour image was georeferenced with a maximum error of 1000 m; and (5) the image corresponded to live, not preserved, animals.…”

Integrating Genomics, Collections, and Community Science to Reveal Speciation in a Variable Monitor Lizard (Varanus tristis)

“…However, these observations also convey important information about the geographic and temporal distribution of morphological variation (Drury et al 2019;Hantak et al 2022). In that way, community science can provide important information about evolutionary processes and inform taxonomy (Fritz and Ihlow 2022;Fritz et al 2023;Pizarro et al 2023).…”