Appendix 1. Summary of Hybrid Characteristics Identified Through the Literature Review

Appendix 1. Summary of hybrid characteristics identified through the literature review.

Hybrid / Parent taxa / Parent origin / Cause of hybridization / Reason for hybridization / Parent protection status / Hybrid conservation status (protected or managed) / Consequences & characteristics / Attitude towardshybrid
Mammals
Coywolf
(Canis rufus) / Grey Wolf
(Canis lupus) / native / natural[94] / Hybridization occurs due to overlapping ranges (sympatric) [17,18,94] / Grey Wolf protected under SARA and the ESA [52,130] / Not protected or managed [39] / Hybrid found in areas where human-Coywolf interactions are possible [17,18,122,39] / Negative – human health and safety concerns [122]
Coyote
(Canis latrans) / native
Grolar Bear
(Ursus maritimus x arctos) / Polar Bear
(Ursus maritimus) / native / natural [109] / Hybridization occurs due to overlapping ranges (sympatric) [109] / Both protected by SARA (as Special Concern) [52] / Not protected or managed [72] / Combination makes for an aggressive predator.
Not thought to be a product of climate change, just a rare occurrence [109] / Negative – human health and safety concerns [143]
Grizzley Bear
(Ursus arctos) / native
Florida Panther/Texas Cougar hybrid
(Puma concolor coryi xconcolor) / Florida Panther
(Puma concolor coryi) / native / anthropogenic (intentional)[34, 66, 105] / Conservation of the Florida Panther – Texas cougars were introduced into the Florida Panther’s habitat in Florida in 1995 [34, 66, 105] / Florida Panther – protected under the ESA [130]
Texas Cougar – not protected in Texas (only State in which it is not protected under the ESA) [125] / Population growth of the Florida Panther hybrid was helped by habitat protection of and construction of highway underpasses [8]
Will need to continuously import cougars for mates [8] / Have seen a significant increase in the Florida Panther hybrid population size [27, 34, 66]
Hybrids are more fit [34, 105] / Positive – increase in Florida Panther population size (conservation is working) [27, 34, 66, 105, 129]
Positive – seen as a “genetic rescue” [66, 104]
Texas Cougar
(Puma concolor) / non-native
Wild Swine/Eurasian Wild Boar hybrid
(Sus scrofadomesticus x s. cristatus) / Wild Swine
(Sus scrofa domesticus) / non-native / anthropogenic (unintentional) [51] / Hybridization occurs due to overlapping ranges (sympatric) [51] / No / Current management includes hunting and trapping of both Wild Swine and hybrid [51] / Hybrids cause destruction to crops and property [146] / Negative – similar attitude to parent taxa (Wild Swine); cause property damage and hybrids harbour parasites [51, 146]
Eurasian Wild Boar
(Sus scrofa cristatus) / non-native
White-tailed Deer/Mule Deer
(Odocoileus virginianus x hemionus) / White-tailed Deer (Odocoileus virginianus) / native / natural [64, 145] / Hybridization occurs due to overlapping ranges (sympatric) [64, 145]
White-tailed moving into Mule deer habitats [145] / No / Not protected or managed / Hybridization is rare [145] / Negative – white-tails could be replacing mule deer populations [150]
Negative – hybrids have lower survival and fitness rates [82, 145]
Mule Deer
(Odocoileus hemionus) / native
Blynx or Lynxcat
(Lynx canadensis x rufus) / Canada Lynx
(Lynx canadensis) / native / anthropogenic (unintentional) [3, 116,132] / Hybridization occurs due to overlapping ranges (sympatric) when mates of their own species cannot be found [65] / Canadian Lynx is protected under the ESA [3, 65, 130, 132] / Not protected or managed. Often shot by hunters [3] / Potential for the hybrids to cause a hybrid swarm and outcompete parental populations [65] / Negative – limits the recovery of the threatened Canada Lynx [65, 117]
Bobcat
(Lynx rufus) / native
Clymene Dolphin
(Stenella clymene) / Spinner Dolphin
(Stenella longirostris) / native / natural [2] / Unknown – possibly caused by selection through preferential mating [2] / Both parents listed on Appendix II of the Convention on the Conservation of Migratory Species of Wild Animals (CMS) [21] / West African population of the Clymene dolphin is listed on Appendix II (species that need or would significantly benefit from international co-operation) of the CMS [22] / Hybridization has resulted in speciation [2, 7] / Positive – contributes to the diversity of marine mammals [2]
Striped Dolphin
(Stenella coeruleoalba) / native
Plains Bison/Cow hybrid
(Bison bison x Bostaurus) / Plains Bison
(Bison bison) / native / anthropogenic (unintentional)[63] / Small, privately owned populations of Plains Bison were bred with domestic cow to obtain bison genes and produce larger cows for human consumption. These hybrids then backcrossed to Plains Bison in the wilderness [63] / Plains Bison protected under SARA (THR) [52] / Not protected or managed. After generations of these backcrosses, hybrids became indistinguishable from pure bison to the point where some were incorporated into bison herds [37, 95] / Genetic viability of Bison is in question. Hybrid bison are less genetically fit thannon-hybrids. Those with cow genes are smaller and there are questions as to their fitness and ability to withstand cold temperatures and deal with heat or energy conversion from forage [37] / Negative – hybrid causing degradation of native Bison genetics [36, 37, 142]
Domestic Cow
(Bostaurus) / non-native
Birds
Mallard/American Black Duck
(Anas platyrhynchos x rubripes) / Mallard
(Anas platyrhynchos) / native / natural [38] / Hybridization occurs due to overlapping ranges (sympatric) [35, 38] / No / Not protected or managed [38] / Hybrid has no effect on parent species and typically is unable to attract a mate [38] / Negative – hybrid decreases the number of Black Ducks [35]
Negative – hybrid can cause introgressive gene flow that results in species decline of parent taxa [38]
American Black Duck
(Anas rubripes) / native
Brewster’s or Lawrence’s Warbler
(Vermivora chrysoptera x cyanoptera) / Golden-winged Warbler
(Vermivora chrysoptera) / native / natural [54, 133, 134] / Hybridization occurs due to overlapping ranges (sympatric); BWWA tends to take over [54, 133, 134] / GWWA is protected by SARA (THR) and ESA [13, 52, 130] / Not protected or managed [13, 54] / Hybrid causing decline of protected GWWA [54] / Negative – hybrid creates competition and GWWA is being replaced by hybrids in addition to BWWA [20, 50, 54,95]
Negative – BWWA becomes dominant (can lead to extinction of GWWA) [54]
Blue-winged Warbler
(Vermivora cyanoptera) / native
MacGillivray’s Warbler/Mourning Warbler (Oporonis tolmiei x philadelphia) / MacGillvray’s Warbler (Oporonis tolmiei) / native / natural [67] / Hybridization occurs due to overlapping ranges (sympatric) [67] / No / Not protected or managed / None/unknown [67] / Neutral – small area where hybridization occurs; no impact to parent taxa [67]
Mourning Warbler (Oporonis philadelphia) / native
Townsend’s Warbler/Black-throated Green Warbler (Dendroica townsendi x virens) / Townsend’s Warbler (Dendroica townsendi) / native / natural [127] / Hybridization occurs due to overlapping ranges (sympatric) [127] / No / Not protected or managed / None/unknown [127] / Neutral – small area where hybridization occurs; no impact to parent taxa [127]
Black-throated Green Warbler (Dendroica virens) / native
Townsend’s Warbler/Hermit Warbler (Dendroica townsendi x occidentalis) / Townsend’s Warbler (Dendroica townsendi) / native / natural [127] / Hybridization occurs due to overlapping ranges (sympatric) [76, 127] / No / Not protected or managed / None/unknown [127] / Negative – phenotypic Townsend’s Warbler hybrids are moving south and replacing Hermit Warblers [76, 127]
Hermit Warblers (Dendroica occidentalis) / native
Audubon’s Warbler/Myrtle Warbler (Dendrioca coronata auduboni x c. coronata) / Audobon’s Warbler (Dendrioca coronata auduboni) / native / natural [10] / Hybridization occurs due to overlapping ranges (sympatric)[10] / No / Not protected or managed / None/unknown [10] / Neutral – relatively stable situation; a process of speciation[10]
Myrtle Warbler (Dendrioca coronata coronata) / native
Sparred Owl
(Strix occidentalis caurina x varia) / Northern Spotted Owl (Strix occidentalis caurina) / native / anthropogenic (unintentional) [58, 60, 61] / Hybridization occurs due to overlapping ranges (sympatric) caused by intensive logging [31, 61, 73, 74]
Barred owls moving into Northern Spotted Owl habitats [31, 57, 60, 61, 73, 74] / Northern Spotted Owl is protected under the ESA and SARA as threatened [11, 52, 130] / Not protected or managed / Barred owls are better competitors than Northern Spotted Owl [31, 57] / Negative – competition with Northern Spotted Owl which is endangered [31]
Negative – inbreeding threatens Northern Spotted Owl population [58]
Negative – increase hybrids will drive Northern Spotted Owl to extinction [58]
Barred Owl (Strix varia) / non-native
Perlin
(Falco peregrinus x columbarius) / Peregrine Falcon
(Falco peregrinus) / native / natural [87] / Unknown / Both parents listed as species of Least Concern by the IUCN, Peregrine Falcon protected the ESA [8, 130] / Not protected or managed / Unknown/no info / Neutral – no real data/info
Merlin
(Falco columbarius) / native
Red-breasted Sapsucker/Yellow-bellied Sapsucker (Sphyrapicus ruber x varius) / Red-breasted Sapsucker (Sphyrapicus ruber) / native / Natural [121] / Hybridization occurs due to overlapping ranges (sympatric) [121] / No / Not protected or managed / None/unknown [121] / Neutral – small area where hybridization occurs; no impact to parent taxa [121]
Yellow-bellied Sapsucker (Sphyrapicus varius) / native
Sharp-tailed Grouse/Greater Prairie-Chicken
(Tympanuchus phasianellus x cupido) / Sharp-tailed Grouse (Tympanuchus phasianellus) / native / natural [19, 84] / Hybridization occurs due to overlapping ranges (sympatric) [84] / Greater Prairie-Chicken is protected by SARA and ESA (EXT) in Canada, and ESA (END) in United States [52, 130] / Not protected or managed / Hybrids are partially fertile [110]
In areas where the two species overlap, Sharp-tailed Grouse will likely eventually replace Greater Prairie-Chickens. Female Greater Prairie Chickens show a preference for Sharp-tailed Grouse males, and Sharp-tailed Grouse are known to dominate Greater Prairie-Chickens during social encounters [110] / Neutral
Greater Prairie-Chicken (Tympanuchus cupido) / native
Fish
Rainbow Trout/Cutthroat hybrid
(Oncorhynchusmykiss x clarki) / Rainbow Trout
(Oncorhynchusmykiss) / native / anthropogenic (intentional) [1, 23, 25, 53, 114] / Rainbow trout were introduced in many cutthroat trout areas for recreational fishing [25, 114] / No (have seen declines in rainbow trout + activists looking to conserve them) [52] / Project to remove the Cutthroat and hybrids in Banff National Park [52] / Have seen interbreeding due to introductions [23, 24, 25, 114] / Negative – hybridization is a threat to cutthroat trout [1, 23, 24, 53, 107, 114]
Neutral – some research shows that hybridization is not a threat [25]
Cutthroat
(Oncorhynchus clarki) / non-native
Tiger Muskellunge
(Esox masquinongy x lucius) / True Muskellunge
(Esox masquinongy) / native / anthropogenic (intentional) [136, 137, 138, 139] / Hybrid is bred to stock lakes for fishing purposes [136, 137, 138, 139] / No / Not protected or managed / Hybrid is sterile [137] / Positive – fishing purposes/recreation [136, 137, 138, 139]
Neutral – no real data/info
Northern Pike
(Esox lucius) / native
Brown Trout/Atlantic Salmon hybrid
(Salmo trutta x salar). / Brown Trout
(Salmo trutta) / native / natural [90] / Hybridization occurs due to overlapping ranges (sympatric) [75, 90] / Atlantic Salmon protected in some areas of Newfoundland (SARA as THR), but not all areas [51] / Not protected or managed [75] / No negative consequences documented / Neutral – there is no positive or negative literature on the subject
Atlantic Salmon
(Salmo salar) / native
Bluegill/Green Sunfish hybrid (Lepomis macrochirus x cyanellus) / Bluegill (Lepomis macrochirus) / native / anthropogenic (intentional) [12] / Hybrid is bred to stock ponds for fishing purposes [12] / No / Not protected but hybrid is actively created for fishing purposes [12] / No negative consequences documented / Positive – greater catchability of hybrids in stocked ponds [12]
Green Sunfish (Lepomis cyanellus) / native
Walleye/Sauger hybrid (Stizostedion vitreum x canadense) / Walleye (Stizostedion vitreum) / native / natural and anthropogenic (intentional)[85] / Hybridization occurs in nature due to overlapping ranges (sympatric) and for intensive fish culture [85] / No / Not protected, but managed as a better option for fish culture [85] / No native consequences documented since hybridization rarely occurs naturally [85] / Positive – hybrids have improved growth and production compared to parent taxa, have potential for commercial food-fish production [85]
Sauger (Stizostedion canadense) / native
Wolffish Interspecific Hybrid (Anarhichas minor x lupus) / Atlantic Wolffish (Anarhichas lupus) / native / natural / Hybridization occurs due to overlapping ranges (sympatric) [48] / Atlantic Wolffish is Special Concern and Spotted Wolffish is Threatened [48] / Not protected or managed / Hybrid difficult to differentiate from parent taxa [48] / Positive – hybridization could facilitate adaptations to novel environments and provide opportunities for range expansion [48]
Spotted Wolffish (Anarhichas minor) / native
Northern Largemouth Bass/Florida Largemouth Bass (Micropterus salmoides salmoidesx s. floridanus) / Northern Largemouth Bass (Micropterus salmoides salmoides) / native / natural / Hybridization occurs due to overlapping ranges (sympatric) [150] / No / Not protected or managed [130] / No consequences documented / Neutral [150]
Florida Largemouth Bass (Micropterus salmoides floridanus) / native
Pecos Pupfish/ Sheepshead Minnow hybrid (Cyprinodon pecosensis x variegatus) / Pecos Pupfish (Cyprinodon pecosensis) / native / anthropogenic (unintentional) [111] / Hybridization occurs due to overlapping ranges (sympatric) [111] / No / Not protected or managed [130] / Hybrids and backcross hybrids have greater fitness (swimming endurance, mating competition and rapid growth) and are therefore promoting rapid spread [111] / Negative – imperiled Pecos Pupfish threatened with replacement by hybrids [111]
Sheepshead Minnow (Cyprinodon variegatus) / non-native
Hybrid Striped Bass
(Morone saxatilis x chrysops) / Striped Bass
(Morone saxatilis) / native / anthropotenic (intentional) [99, 140] / Bred in captivity and used to stock fishing ponds. Hybrids are more tolerant of warmer water and lower dissolved oxygen than striped bass. For these reasons, they can be stocked into a wider variety of waters than striped bass [140] / No / Not protected or managed [140] / Has escaped from fishing ponds and has been reported in the White, Wabash, Ohio, and Tennessee rivers and several of their tributaries in America [99, 140] / Neutral – hybrid has difficulty reproducing naturally so no impact on native fish species [140]
White Bass
(Morone chrysops) / native
Golden Shiner/Rudd hybrid (Notemigonus crysoleucas x Scardinius erythrophthalmus) / Golden Shiner
(Notemigonus crysoleucas) / native / anthropogenic (unintentional) [123] / Hybridization occurs due to overlapping ranges (sympatric) [123] / No / Not protected or managed / This crossbreeding may cause unknown effects to the wild populations of the native species, such as loss of fitness and spawning behaviour [123] / Negative [123]
Rudd
(Scardinius erythrophthalmus) / non-native
Reptiles
New Mexico Whiptail
(Cnemidophorus neomexicanus) / Little Striped Whiptail
(Cnemidophorus inornatus) / native / natural [28] / Hybridization occurs due to overlapping ranges (sympatric) [28] / No / Not protected or managed / Hybridization prevents healthy males from forming whereas males do exist inboth parent species [28, 29]
Hybrid species are all female – hybrids are “fertile” in that they reproduce through parthenogenesis (results is clones of the mother) [28, 29] / Neutral
Positive –genes have been passed on [28]
Western Whiptail
(Cnemidophorus tigris) / native
Jungle Corn Snake
(Pantherophis guttatus x Lampropeltis getula californiae) / Red Cornsnake (Pantherophis guttatus) / native / natural [40] / Unknown/no information / No / Not protected or managed / Hybrids of different genera but they are not sterile [40]
Hybrids are often albino [40] / Neutral
California Kingsnake (Lampropeltis getula californiae) / native
Loggerhead Turtle/ Kemp’s Ridley (Caretta caretta x Lepidochelys kempii) / Loggerhead Turtle (Caretta caretta) / native / natural [71] / Hybridization occurs due to overlapping ranges (sympatric) [71] / Both protected by the ESA [130] / Not protected or managed / Hybridization of the parent taxa is uncommon. More research is needed to determine consequences and appropriate management of hybrid [71] / Neutral – only few cases documented [71]
Kemp’s Ridley (Lepidochelys kempii) / native
Loggerhead Turtle/ Hawksbill (Caretta caretta x Eretmochelys imbricata) / Loggerhead Turtle (Caretta caretta) / native / natural [71] / Hybridization occurs due to overlapping ranges (sympatric) [71] / Both protected by the ESA [130] / Not protected or managed / Hybridization of the parent taxa is uncommon. More research is needed to determine consequences and appropriate management of hybrid [71] / Neutral – only few cases documented [71]
Hawksbill (Eretmochelys imbricata) / native
Green Turtle/Hawksbill (Chelonia mydas x Eretmochelys imbricata) / Green Turtle (Chelonia mydas) / native / natural [71] / Hybridization occurs due to overlapping ranges (sympatric) [71] / Both protected by the ESA [130] / Not protected or managed / Hybrids have been documented to have reduced fitness [71] / Neutral – only few cases documented [71]
Hawksbill (Eretmochelys imbricata) / native
Green Turtle/Loggerhead Turtle hybrid
(Caretta caretta xmydas) / Loggerhead Turtle
(Caretta caretta) / native / anthropogenic (unintentional) [68, 71] / Unknown/no information (rare hybridization event) [71] / Both protected by the ESA [130] / Not protected or managed / Parent taxa genetically separated for 50 million years [68]
Hybrid displays traits of the Green Turtle (found in Atlantic waters), resulting in possible mis-identification [68] / Neutral – only few cases documented[71]
Green Turtle (Chelonia mydas) / native
Bullsnake/Western Fox Snake
(Pituophis catenifer sayi x Mintonius vulpinus) / Bullsnake
(Pituophis catenifer sayi) / native / natural [81] / Unknown/no information / No / Not protected or managed / Hybrids of different genera (rare – only seen three times in reptiles so far) [81] / Neutral
Western Fox Snake
(Mintonius vulpinus) / native
Massasauga/Timber Rattlesnake
(Sistrurus catenatus x Crotalus horridus) / Massasauga
(Sistrurus catenatus) / native / natural [5] / Unknown/no information / Both protected by regional acts [98, 52] / Not protected or managed / Hybrids of different genera (rare – only seen three times in reptiles so far) [5] / Neutral
Timber Rattlesnake
(Crotalus horridus) / native
Common Watersnake/Southern Watersnake
(Nerodia sipedon x fasciata) / Northern Watersnake (Nerodia sipedon) / native / natural [89] / Hybridization occurs due to overlapping ranges (sympatric) [30, 89] / No / Not protected or managed / There is potential inferiority of some hybrid genotypes [89] / Neutral [89]
Southern Watersnake (Nerodiafasciata) / native
Plains Gartersnake/ Butler’s Gartersnake hybrid (Thamnophis radix x butleri) / Plains Gartersnake (Thamnophis radix) / native / natural [105] / Hybridization occurs due to overlapping ranges (sympatric) [105] / Butler’s Gartersnake is protected by the SARA [52] / Not protected or managed / Neutral [105]
Butler’s Gartersnake (Thamnophisbutleri) / native
Common Gartersnake/Butlers Gartersnake (Thamnophis sirtalis x butleri) / Common Gartersnake (Thamnophis sirtalis) / native / natural [69] / Hybridization occurs due to overlapping ranges (sympatric) [69, 144] / Butler’s Gartersnake is protected by the SARA [52] / Not protected or managed / Hybridization of the parent taxa is uncommon. More research is needed to determine if the hybrid poses a threat to Butler’s Gartersnake [69] / Neutral [69]
Butlers Gartersnake (Thamnophis butleri) / native
Amphibians
California Tiger Salamander/Barred Tiger Salamander hybrid
(Ambystoma californiense
x mavortium) / California Tiger Salamander
(Ambystoma californiense) / native / anthropogenic (unintentional) [43, 115, 131] / Barred Tiger Salamander was brought to California to be used as fish bait and is now invasive and hybridizes with California Tiger Salamander [43, 115] / California Tiger Salamander listed as threatened by the ESA [29, 115, 130] / Not protected or managed / Hybridization has resulted in very strong hybrid vigour [33, 42, 43, 115, 131] / Negative – hybrid is more likely to survive than either parent species, and California Tiger Salamander is endangered [29]