Appendix 1. Summary of hybrid characteristics identified through the
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Appendix 1. Summary of hybrid characteristics identified through the literature review. Hybrid Mammals Coywolf (Canis rufus) Grolar Bear (Ursus maritimus x arctos) Florida Panther/Texas Cougar hybrid (Puma concolor coryi x concolor) Parent taxa Grey Wolf (Canis lupus) native Coyote (Canis latrans) native Polar Bear (Ursus maritimus) native Grizzley Bear (Ursus arctos) native Florida Panther (Puma concolor coryi) native Texas Cougar (Puma concolor) Wild Swine/Eurasian Wild Boar hybrid (Sus scrofa Parent origin Wild Swine (Sus scrofa domesticus) Cause of hybridization Parent protection status Hybrid conservation status (protected or managed) Consequences & characteristics Attitude towards hybrid 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] natural [109] Hybridization occurs due to overlapping ranges (sympatric) [109] Both protected by SARA (as Special Concern) [52] Not protected or managed [72] Negative – human health and safety concerns [143] 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] Population growth of the Florida Panther hybrid was helped by habitat protection of and construction of highway underpasses [8] Combination makes for an aggressive predator. Not thought to be a product of climate change, just a rare occurrence [109] Have seen a significant increase in the Florida Panther hybrid population size [27, 34, 66] Hybrids are more fit [34, 105] Positive – seen as a “genetic rescue” [66, 104] Hybrids cause destruction to crops and Negative – similar attitude to parent taxa (Wild Swine); nonnative nonnative Reason for hybridization anthropogenic (unintentional) [51] Hybridization occurs due to overlapping Texas Cougar – not protected in Texas (only State in which it is not protected under the ESA) [125] No Will need to continuously import cougars for mates [8] Current management includes Positive – increase in Florida Panther population size (conservation is working) [27, 34, 66, 105, 129] Hybrid Parent taxa Parent origin domesticus x s. cristatus) Eurasian Wild Boar (Sus scrofa cristatus) nonnative White-tailed Deer/Mule Deer (Odocoileus virginianus x hemionus) White-tailed Deer (Odocoileus virginianus) native Mule Deer (Odocoileus hemionus) native Canada Lynx (Lynx canadensis) Bobcat (Lynx rufus) native Spinner Dolphin (Stenella longirostris) native Striped Dolphin (Stenella coeruleoalba) native Blynx or Lynxcat (Lynx canadensis x rufus) Clymene Dolphin (Stenella clymene) Cause of hybridization Reason for hybridization Parent protection status ranges (sympatric) [51] natural [64, 145] anthropogenic (unintentional) [3, 116, 132] native natural [2] Hybridization occurs due to overlapping ranges (sympatric) [64, 145] White-tailed moving into Mule deer habitats [145] Hybridization occurs due to overlapping ranges (sympatric) when mates of their own species cannot be found [65] Unknown – possibly caused by selection through preferential mating [2] No Hybrid conservation status (protected or managed) hunting and trapping of both Wild Swine and hybrid [51] Not protected or managed Consequences & characteristics Attitude towards hybrid property [146] cause property damage and hybrids harbour parasites [51, 146] Negative – whitetails could be replacing mule deer populations [150] Hybridization is rare [145] 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] 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] Negative – hybrids have lower survival and fitness rates [82, 145] Negative – limits the recovery of the threatened Canada Lynx [65, 117] Positive – contributes to the diversity of marine mammals [2] Hybrid Plains Bison/Cow hybrid (Bison bison x Bos taurus) Birds Mallard/American Black Duck (Anas platyrhynchos x rubripes) Brewster’s or Lawrence’s Warbler (Vermivora chrysoptera x cyanoptera) Parent taxa Parent origin Plains Bison (Bison bison) native Domestic Cow (Bos taurus) nonnative Mallard (Anas platyrhynchos) American Black Duck (Anas rubripes) native Golden-winged Warbler (Vermivora chrysoptera) native Cause of hybridization Reason for hybridization Parent protection status 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] natural [38] Hybridization occurs due to overlapping ranges (sympatric) [35, 38] No Hybridization occurs due to overlapping ranges (sympatric); BWWA tends to GWWA is protected by SARA (THR) and ESA [13, 52, 130] native natural [54, 133, 134] Hybrid conservation status (protected or managed) Not protected or managed. After generations of these backcrosses, hybrids became indistinguishabl e from pure bison to the point where some were incorporated into bison herds [37, 95] Not protected or managed [38] Not protected or managed [13, 54] Consequences & characteristics Attitude towards hybrid Genetic viability of Bison is in question. Hybrid bison are less genetically fit than non-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] 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] Hybrid causing decline of protected GWWA [54] Negative – hybrid can cause introgressive gene flow that results in species decline of parent taxa [38] Negative – hybrid creates competition and GWWA is being replaced by hybrids in addition Hybrid MacGillivray’s Warbler/Mourning Warbler (Oporonis tolmiei x philadelphia) Townsend’s Warbler/Blackthroated Green Warbler (Dendroica townsendi x virens) Townsend’s Warbler/Hermit Warbler (Dendroica townsendi x occidentalis) Audubon’s Warbler/Myrtle Warbler (Dendrioca coronata auduboni x c. coronata) Parent taxa Parent origin Blue-winged Warbler (Vermivora cyanoptera) native MacGillvray’s Warbler (Oporonis tolmiei) Mourning Warbler (Oporonis philadelphia) Townsend’s Warbler (Dendroica townsendi) Black-throated Green Warbler (Dendroica virens) Townsend’s Warbler (Dendroica townsendi) Hermit Warblers (Dendroica occidentalis) native Audobon’s Warbler (Dendrioca coronata auduboni) Myrtle Warbler (Dendrioca coronata coronata) native Cause of hybridization Consequences & characteristics Attitude towards hybrid to BWWA [20, 50, 54, 95] Negative – BWWA becomes dominant (can lead to extinction of GWWA) [54] Neutral – small area where hybridization occurs; no impact to parent taxa [67] Hybridization occurs due to overlapping ranges (sympatric) [67] No Not protected or managed None/unknown [67] 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] natural [127] Hybridization occurs due to overlapping ranges (sympatric) [76, 127] No Not protected or managed None/unknown [127] natural [10] Hybridization occurs due to overlapping ranges (sympatric) [10] No Not protected or managed None/unknown [10] Negative – phenotypic Townsend’s Warbler hybrids are moving south and replacing Hermit Warblers [76, 127] Neutral – relatively stable situation; a process of speciation [10] native native Hybrid conservation status (protected or managed) natural [67] native native Parent protection status take over [54, 133, 134] native native Reason for hybridization Hybrid Sparred Owl (Strix occidentalis caurina x varia) Perlin (Falco peregrinus x columbarius) Red-breasted Sapsucker/Yellowbellied Sapsucker (Sphyrapicus ruber x varius) Parent taxa Parent origin Northern Spotted Owl (Strix occidentalis caurina) native Barred Owl (Strix varia) nonnative Peregrine Falcon (Falco peregrinus) native Merlin (Falco columbarius) native Red-breasted Sapsucker (Sphyrapicus ruber) Yellow-bellied Sapsucker (Sphyrapicus varius) native native Cause of hybridization anthropogenic (unintentional) [58, 60, 61] Reason for hybridization Parent protection status Hybridization occurs due to overlapping ranges (sympatric) caused by intensive logging [31, 61, 73, 74] Northern Spotted Owl is protected under the ESA and SARA as threatened [11, 52, 130] Hybrid conservation status (protected or managed) Not protected or managed Consequences & characteristics Attitude towards hybrid 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] Barred owls moving into Northern Spotted Owl habitats [31, 57, 60, 61, 73, 74] natural [87] Unknown Natural [121] Hybridization occurs due to overlapping ranges (sympatric) [121] Both parents listed as species of Least Concern by the IUCN, Peregrine Falcon protected the ESA [8, 130] No Not protected or managed Unknown/no info Not protected or managed None/unknown [121] Negative – increase hybrids will drive Northern Spotted Owl to extinction [58] Neutral – no real data/info Neutral – small area where hybridization occurs; no impact to parent taxa [121] Hybrid Sharp-tailed Grouse/Greater Prairie-Chicken (Tympanuchus phasianellus x cupido) Fish Rainbow Trout/Cutthroat hybrid (Oncorhynchus mykiss x clarki) Tiger Muskellunge (Esox masquinongy x lucius) Parent taxa Parent origin Sharp-tailed Grouse (Tympanuchus phasianellus) native Greater PrairieChicken (Tympanuchus cupido) native Rainbow Trout (Oncorhynchus mykiss) Cutthroat (Oncorhynchus clarki) native True Muskellunge (Esox masquinongy) Northern Pike (Esox lucius) native Cause of hybridization Reason for hybridization Parent protection status natural [19, 84] Hybridization occurs due to overlapping ranges (sympatric) [84] Greater PrairieChicken is protected by SARA and ESA (EXT) in Canada, and ESA (END) in United States [52, 130] 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] Hybrid is bred to stock lakes for fishing purposes [136, 137, 138, 139] No Not protected or managed Hybrid is sterile [137] anthropogenic (intentional) [1, 23, 25, 53, 114] nonnative native anthropogenic (intentional) [136, 137, 138, 139] Hybrid conservation status (protected or managed) Not protected or managed Consequences & characteristics Attitude towards hybrid Hybrids are partially fertile [110] Neutral In areas where the two species overlap, Sharptailed 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 PrairieChickens during social encounters [110] 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] Positive – fishing purposes/recreatio n [136, 137, 138, 139] Neutral – no real data/info Hybrid Parent taxa Parent origin Cause of hybridization Reason for hybridization Parent protection status natural [90] Hybridization occurs due to overlapping ranges (sympatric) [75, 90] anthropogenic (intentional) [12] Hybrid is bred to stock ponds for fishing purposes [12] Atlantic Salmon protected in some areas of Newfoundlan d (SARA as THR), but not all areas [51] No Hybridization occurs in nature due to overlapping ranges (sympatric) and for intensive fish culture [85] No Hybrid conservation status (protected or managed) Not protected or managed [75] Consequences & characteristics Attitude towards hybrid No negative consequences documented Neutral – there is no positive or negative literature on the subject Not protected but hybrid is actively created for fishing purposes [12] Not protected, but managed as a better option for fish culture [85] No negative consequences documented Positive – greater catchability of hybrids in stocked ponds [12] 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 foodfish production [85] Positive – hybridization could facilitate adaptations to novel environments and provide opportunities for range expansion [48] Neutral [150] Brown Trout/Atlantic Salmon hybrid (Salmo trutta x salar). Brown Trout (Salmo trutta) Atlantic Salmon (Salmo salar) native Bluegill/Green Sunfish hybrid (Lepomis macrochirus x cyanellus) Walleye/Sauger hybrid (Stizostedion vitreum x canadense) Bluegill (Lepomis macrochirus) Green Sunfish (Lepomis cyanellus) Walleye (Stizostedion vitreum) Sauger (Stizostedion canadense) native native natural and anthropogenic (intentional) [85] Wolffish Interspecific Hybrid (Anarhichas minor x lupus) Atlantic Wolffish (Anarhichas lupus) Spotted Wolffish (Anarhichas minor) 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] 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 Northern Largemouth Bass/Florida Largemouth Bass (Micropterus salmoides salmoides native native native native Hybrid x s. floridanus) Pecos Pupfish/ Sheepshead Minnow hybrid (Cyprinodon pecosensis x variegatus) Hybrid Striped Bass (Morone saxatilis x chrysops) Golden Shiner/Rudd hybrid (Notemigonus Parent taxa Parent origin Florida Largemouth Bass (Micropterus salmoides floridanus) Pecos Pupfish (Cyprinodon pecosensis) Sheepshead Minnow (Cyprinodon variegatus) native Striped Bass (Morone saxatilis) native White Bass (Morone chrysops) native Golden Shiner (Notemigonus crysoleucas) native native Cause of hybridization Reason for hybridization Parent protection status Hybrid conservation status (protected or managed) Consequences & characteristics Attitude towards hybrid Hybrids and backcross hybrids have greater fitness (swimming endurance, mating competition and rapid growth) and are therefore promoting rapid spread [111] 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] Negative – imperiled Pecos Pupfish threatened with replacement by hybrids [111] This crossbreeding may cause unknown effects Negative [123] anthropogenic (unintentional) [111] Hybridization occurs due to overlapping ranges (sympatric) [111] No Not protected or managed [130] 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] Hybridization occurs due to overlapping No Not protected or managed [140] No Not protected or managed nonnative anthropogenic (unintentional) [123] Neutral – hybrid has difficulty reproducing naturally so no impact on native fish species [140] Hybrid crysoleucas x Scardinius erythrophthalmus) Reptiles New Mexico Whiptail (Cnemidophorus neomexicanus) Jungle Corn Snake (Pantherophis guttatus x Lampropeltis getula californiae) Loggerhead Turtle/ Kemp’s Ridley (Caretta caretta x Parent taxa Parent origin Rudd (Scardinius erythrophthalmu s) nonnative Little Striped Whiptail (Cnemidophorus inornatus) native Western Whiptail (Cnemidophorus tigris) native Red Cornsnake (Pantherophis guttatus) California Kingsnake (Lampropeltis getula californiae) Loggerhead Turtle (Caretta caretta) native Cause of hybridization Reason for hybridization Parent protection status Hybrid conservation status (protected or managed) ranges (sympatric) [123] natural [28] natural [40] Hybridization occurs due to overlapping ranges (sympatric) [28] Unknown/no information Consequences & characteristics Attitude towards hybrid to the wild populations of the native species, such as loss of fitness and spawning behaviour [123] No No Not protected or managed Not protected or managed native 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] Hybrids of different genera but they are not sterile [40] Neutral Positive –genes have been passed on [28] Neutral Hybrids are often albino [40] native natural [71] Hybridization occurs due to overlapping Both protected by the ESA Not protected or managed Hybridization of the parent taxa is uncommon. More Neutral – only few cases documented [71] Hybrid Parent taxa Parent origin Lepidochelys kempii) Kemp’s Ridley (Lepidochelys kempii) native Loggerhead Turtle/ Hawksbill (Caretta caretta x Eretmochelys imbricata) Loggerhead Turtle (Caretta caretta) Hawksbill (Eretmochelys imbricata) native Green Turtle/Hawksbill (Chelonia mydas x Eretmochelys imbricata) Green Turtle (Chelonia mydas) Hawksbill (Eretmochelys imbricata) Loggerhead Turtle (Caretta caretta) native Green Turtle (Chelonia mydas) native Bullsnake (Pituophis catenifer sayi) Western Fox Snake (Mintonius vulpinus) native Green Turtle/Loggerhead Turtle hybrid (Caretta caretta x mydas) Bullsnake/Western Fox Snake (Pituophis catenifer sayi x Mintonius vulpinus) Cause of hybridization Hybrid conservation status (protected or managed) [130] natural [71] Hybridization occurs due to overlapping ranges (sympatric) [71] Both protected by the ESA [130] Not protected or managed natural [71] Hybridization occurs due to overlapping ranges (sympatric) [71] Both protected by the ESA [130] Not protected or managed anthropogenic (unintentional) [68, 71] Unknown/no information (rare hybridization event) [71] Both protected by the ESA [130] Not protected or managed native native Parent protection status ranges (sympatric) [71] native native Reason for hybridization natural [81] Unknown/no information No Not protected or managed Consequences & characteristics research is needed to determine consequences and appropriate management of hybrid [71] Hybridization of the parent taxa is uncommon. More research is needed to determine consequences and appropriate management of hybrid [71] Hybrids have been documented to have reduced fitness [71] Parent taxa genetically separated for 50 million years [68] Hybrid displays traits of the Green Turtle (found in Atlantic waters), resulting in possible misidentification [68] Hybrids of different genera (rare – only seen three times in reptiles so far) [81] Attitude towards hybrid Neutral – only few cases documented [71] Neutral – only few cases documented [71] Neutral – only few cases documented [71] Neutral Hybrid Massasauga/Timber Rattlesnake (Sistrurus catenatus x Crotalus horridus) Common Watersnake/ Southern Watersnake (Nerodia sipedon x fasciata) Plains Gartersnake/ Butler’s Gartersnake hybrid (Thamnophis radix x butleri) Common Gartersnake/Butlers Gartersnake (Thamnophis sirtalis x butleri) Amphibians California Tiger Salamander/Barred Tiger Salamander hybrid Parent taxa Parent origin Massasauga (Sistrurus catenatus) Timber Rattlesnake (Crotalus horridus) Northern Watersnake (Nerodia sipedon) Southern Watersnake (Nerodia fasciata) Plains Gartersnake (Thamnophis radix) Butler’s Gartersnake (Thamnophis butleri) Common Gartersnake (Thamnophis sirtalis) Butlers Gartersnake (Thamnophis butleri) native California Tiger Salamander (Ambystoma californiense) native Cause of hybridization Reason for hybridization Attitude towards hybrid Hybrids of different genera (rare – only seen three times in reptiles so far) [5] Neutral There is potential inferiority of some hybrid genotypes [89] Neutral [89] Both protected by regional acts [98, 52] natural [89] Hybridization occurs due to overlapping ranges (sympatric) [30, 89] No Not protected or managed natural [105] Hybridization occurs due to overlapping ranges (sympatric) [105] Butler’s Gartersnake is protected by the SARA [52] Not protected or managed 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] anthropogenic (unintentional) [43, 115, 131] Barred Tiger Salamander was brought to California to be California Tiger Salamander listed as Not protected or managed Hybridization has resulted in very strong hybrid vigour [33, 42, Negative – hybrid is more likely to survive than either parent species, native native Consequences & characteristics Unknown/no information native native Hybrid conservation status (protected or managed) Not protected or managed natural [5] native native Parent protection status native Neutral [105] Hybrid (Ambystoma californiense x mavortium) Parent taxa Barred Tiger Salamander (Ambystoma mavortium) Parent origin nonnative Plains Spadefoot Toad/New Mexico Spadefoot Toad hybrid (Spea bombifrons x multiplicata) Plains Spadefoot Toad (Spea bombifrons) New Mexico Spadefoot Toad (Spea multiplicata) native American Toad/Woodhouse's Toad hybrid (Bufo americanus x woodhousii) Woodhouse's Toad (Bufo woodhousii) American Toad (Bufo americanus) Florida Bog Frog (Lithobates okaloosae) native Florida Bog Frog/Bronze Frog hybrid (Lithobates Cause of hybridization natural [46, 103] native natural [113] native native natural [4] Reason for hybridization Parent protection status used as fish bait and is now invasive and hybridizes with California Tiger Salamander [43, 115] threatened by the ESA [29, 115, 130] Female Plains Spadefoot will mate with New Mexico Spadefoot rather than their own species if the resulting hybrid tadpole would have higher chances of survival [46, 103] Hybridization occurs due to overlapping ranges (sympatric) [113] No Hybridization occurs due to overlapping Hybrid conservation status (protected or managed) Consequences & characteristics Attitude towards hybrid 43, 115, 131] and California Tiger Salamander is endangered [29] Negative – hybrid may drive parent species to extinction [42, 43, 115, 131] Neutral Not protected or managed Hybrids are less fertile and metamorphose two weeks earlier than pure Plains Spadefoot Toad tadpoles (increases chance of survival) [46] No Not protected or managed Result of a hybrid zone between the two species [113] Neutral Not protected under ESA Not protected or managed Florida Bog Frog has limited distribution and Negative concern that hybrid will swamp Positive – hybridization allows for high chance of survival or offspring [103] Hybrid okaloosae x clamitans) Parent taxa Bronze Frog (Lithobates clamitans) Parent origin Cause of hybridization native Reason for hybridization ranges (sympatric) [4] Parent protection status Hybrid conservation status (protected or managed) [130] State Species of Special Concern [46] Consequences & characteristics Attitude towards hybrid Bronze Frog is widespread, concern that hybrid species will swamp parent taxa [4] geographicallyrestricted Florida Bog Frog [4] Neutral – depending on environmental variables, hybrid population has reduced or greater fitness compared to parent taxa [102] Negative – adverse effects on parent taxa populations [59] Florida Bog Frog protected under Florida’s Endangered and Threatened Species Rule [45] Plains Leopard Frog/Southern Leopard Frog hybrid (Rana blairi x sphenocephala) Plains Leopard Frog (Rana blairi) Southern Leopard Frog (Rana sphenocephala) native American Green Treefrog/Barking Treefrog hybrid (Hyla cinerea x gratiosa) American Green Treefrog (Hyla cinerea) Barking Treefrog (Hyla gratiosa) native Fowler’s Toad/American Toad hybrid (Bufo fowleri x americanus) Fowler’s Toad (Bufo fowleri) American Toad (Bufo americanus) native Insects natural [102] Hybridization occurs due to adjacent or overlapping ranges (parapatric or sympatric) [102] No Not protected or managed Some populations out-compete parent taxa, other hybrid populations had reduced fitness [102] natural [59] Hybridization occurs due to overlapping ranges (sympatric) [59] No Not protected or managed natural [56] Hybridization occurs due to overlapping ranges (sympatric) [30, 56] Fowler’s Toad protected under SARA and ESA (END) [52, 130] Not protected or managed [56] Hybrids most likely to survive and return to breed in ponds compared to parent taxa [59] Hybridization not considered a threat to Fowler’s Toad [56] native native native Neutral – no introgression and no negative effect on Fowler’s Toad [55, 56] Hybrid Africanized Honeybee (Apis mellifera ligustica x m. scutellata) Lonicera Fly (Rhagoletis mendax x zephyria) Red imported Fire Ant/Black Imported Fire Ant (Solenopsis invicta x richteri) Common House Mosquito/Southern House Mosquito (Culex pipiens x quinquefasciatus) Parent taxa Parent origin European Honeybee (Apis mellifera ligustica) native African Honeybee (Apis mellifera scutellata) nonnative Blueberry Maggot (Rhagoletis mendax) Snowberry Maggot (Rhagoletis zephyria) Red imported Fire Ant (Solenopsis invicta) Black Imported Fire Ant (Solenopsis richteri) Common house mosquito (Culex pipiens) native Cause of hybridization anthropogenic (unintentional) [15, 80] Hybrid conservation status (protected or managed) Not protected or managed Consequences & characteristics Attitude towards hybrid Considered invasive in the southern-western United States and other select regions in North America [6, 112] Negative – health risks to humans (caused 11 human deaths since first reported in the United States in 1990) [6, 80, 135] No natural [9, 118, 119] Possibly due to a reproductive barrier breakdown caused by plant preference [118, 119] No Not protected or managed Rare example of a new species arising from hybridization (example of speciation) [9, 100] anthropogenic (unintentional) [91] Accidental introduction of the two species of ants to North America resulted in them hybridizing [91] No Not protected or managed Hybrids are more similar to the Black Imported Fire Ant [96] Negative – hybrid ants outcompete native ants for resources [49] anthropogenic (unintentional) [26] Possibly caused by accidental human transport of the two species between Europe and North America No Not protected or managed Hybridization between the species is being blamed for the West Nile crisis in North America (no such crisis Negative – hybrid is a West Nile vector in North America + could be in the future in Europe if climate warms [26, 120] nonnative native Parent protection status African Honeybee was brought over to Brazil to help with the rapid decline of bees and resulted in hybridization [15, 80] native nonnative Reason for hybridization Negative – not as effective pollinators as European Honeybees [112] Neutral Hybrid Appalachian Tiger Swallowtail (Papilio appalachiensis) Plants Freeman’s Maple (Acer x freemanii) Parent taxa Parent origin Southern House Mosquito (Culex quinquefasciatus ) native Eastern Tiger Swallowtail (Papilio glaucus) native Canadian Tiger Swallowtail (Papilio canadensis) native Silver Maple (Acer saccharinum) native Cause of hybridization Reason for hybridization Parent protection status Hybrid conservation status (protected or managed) [120] Consequences & characteristics Attitude towards hybrid observed yet in Europe although both species occur there) [26, 120] natural [78] Hybridization occurs due to overlapping ranges (sympatric) [78] No Not protected or managed; treated as a native species [78] natural & anthropogenic (intentional) [69, 88, 116] Silver Maple and Red Maple freely hybridize both in the wild and in the nursery. No Not protected or managed Southern mosquitos bite birds, whereas common house mosquitos bite humans. When they hybridize, it results in more human-biting mosquitos (hybrid not yet observed in Europe, possibly due to climate) [26, 120] Appalachian Tiger Swallowtail is considered to be a species on its own. It was only recent discovered that it was produced through hybridization between Eastern Tiger Swallowtail and Canadian Tiger Swallowtail. The hybrid rarely mates with parent taxa [78, 126] Advantage of using Freeman's Maple in urban areas is that they are much more Positive - Hybrid speciation is more common in plants, but there are very few cases in animals. This study may create the fullest picture we have to date of hybrid speciation occurring in an animal [126, 141] Neutral – even though hybrids can outcompete parents in urbanized areas, Hybrid Butternut Hybrid (Juglans x bixbyi) Parent taxa Parent origin Red Maple (Acer rubrum) native Butternut (Juglans cinerea) native Japanese Walnut (Juglans ailantifolia) nonnative Cause of hybridization Reason for hybridization Parent protection status Hybrid conservation status (protected or managed) Some hybrids were recognized as superior to either species. Oliver Freeman produced a controlled cross in 1933 [79, 88, 116] anthropogenic (unintentional) [47] Hybridization occurs due to overlapping ranges (sympatric), although Japanese Walnut is not native to Butternut range; it was introduced to the area. The parent taxa have the same bloom time [47] Butternut protected under ESA (END) [130] Not protected or managed, but because hybrids are resistant to canker (disease causing decline of Butternut), hybridization is currently seen as a way to protect Butternut, but more knowledge is required to know full effects [41] Consequences & characteristics Attitude towards hybrid tolerant of high pH soils than the commonly planted red maple, and therefore, are not as prone to succumbing to stresses induced by iron chlorosis. Therefore, in many urban areas, Freeman’s Maple is outcompeting and replacing native parents [88] Dilution of native species with nonnative genes. But hybridization may save the species from extinction from Butternut canker as some hybrids are resistant [41] there is not literature to indicate a negative attitude toward the species [116] Negative – hybrids are highly fruitful, and can mate with hybrids, parent taxa, and selfpollinate, making identification difficult [47] Negative – unknown if hybrids can fully replace ecological services of Butternut, and they could “pollute” the gene pool [41] Positive – hybrid may be the only type of Butternut found in an area [41, 47] Hybrid Hybrid Ash (Fraxinus spp.) Red Mulberry Hybrid (Morus rubra x alba) Hybrid Watermilfoil (Myriophyllum spicatum x sibiricum) Parent taxa Parent origin North American Ash (Fraxinus americana and F. nigra) native Asian Ash (Fraxinus chinensis, F. angustifolia spp. syriaca, and F. mandshurica) Red Mulberry (Morus rubra) nonnative White Mulberry (Morus alba) nonnative Spiked Watermilfoil (Myriophyllum sibiricum) native native Cause of hybridization anthropogenic (intentional) [76] Reason for hybridization Parent protection status Hybrid conservation status (protected or managed) Not protected or managed. Currently in experimental stage where resistant hybrids are being tested [76] Created to abate the effects of Emerald Ash Borer on native ash populations [76, 108, 129] No anthropogenic (unintentional) [97] Hybridization occurs due to overlapping ranges (sympatric), although White Mulberry is not native to Red Mulberry range; it was introduced to the area [97] Red Mulberry protected under ESA [130] Not protected, but instead, Hybrid and White Mulberries are being removed in the vicinity of Red Mulberries to reduce competition and potential hybridization [97] anthropogenic (unintentional) [92] Hybridization occurs due to overlapping ranges (sympatric) [92] No Control measures in development [92] Consequences & characteristics Attitude towards hybrid North American ash have no resistance to Emerald Ash Borer infestation, therefore, hybrid may help aid in the protection of ash forests [76, 108] Positive – Ash forests will be protected as a vegetation community [76] Genetic dilution of Red Mulberry. Most hybrids are more genetically similar to White Mulberry. Hybrid and White Mulberry outcompete Red Mulberry as they recolonize better (more successful seed germination & establishment). Overall, the native Red Mulberry is being genetically assimilated by White Mulberry [97] Hybrid is invasive in aquatic ecosystems [92] Negative – hybridization may result in extirpation of pure Red Mulberry from Canada [97] Negative – the forests will now have non-native genetics [128] Negative – considered an invasive threat to water systems [92] Hybrid Bohemian Knotweed (Fallopia bohemicum) Hybrid Cattail (Typha x glauca) Hybrid Crack Willow (Salix x rubens) Parent taxa Parent origin Eurasian Watermilfoil (Myriophyllum spicatum) nonnative Japanese Knotweed (Fallopia cuspidatum) nonnative Giant Knotweed (Fallopia sachalinense) nonnative Broad-leaved Cattail (Typha latifolia) native Narrow-leaved Cattail (Typha angustifolia) nonnative (species origin is under debate) White Willow (Salix alba) native Cause of hybridization Reason for hybridization Parent protection status Hybrid conservation status (protected or managed) Consequences & characteristics Attitude towards hybrid anthropogenic (unintentional) [124] Hybridization occurs due to overlapping ranges (sympatric) [124, 149] No Managed for removal, along with parent taxa [124] Hybrid may be more invasive than parent taxa due to greater genetic diversity and greater ability to disperse into areas where parent taxa have not established [124] Negative – hybrid may be more invasive than parent taxa [124] anthropogenic (unintentional) [103] Hybridization occurs due to overlapping ranges (sympatric) [103] No Create a monoculture and outcompete native and sometimes rare wetland plants, and ultimately lower biodiversity of habitats. Affects plant and animal biodiversity in wetlands [14, 103] Negative – invades wetlands and displaces native vegetation and lowers biodiversity and floristic quality [83, 103] anthropogenic (unintentional) Hybridization occurs due to No Not protected, but sometimes managed by cutting, burning, or grazing, followed by flooding or herbicide, to provide shortterm control, but re-growth from rhizomes and a vast soil seed-bank complicate eradication [14, 103] Not protected or managed Out-competes native Salix [62] Negative – invades wetlands Hybrid Grey Oak/Gambel Oak (Quercus grisea x gambelii) Fremont’s Cottonwood/ Narrowleaf Cottonwood hybrid (Populus fremontii x angustifolia) Red/Siberian Elm hybrid (Ulmus rubra x pumila) Parent taxa Parent origin Cause of hybridization Crack Willow (Salix fragilis) nonnative [32] Grey Oak (Quercus grisea) Gambel Oak (Quercus gambelii) Fremont’s Cottonwood (Populus fremontii) Narrowleaf Cottonwood (Populus angustifolia) native natural [16] Red Elm (Ulmus rubra) native Siberian Elm (Ulmus pumila) nonnative native native Reason for hybridization overlapping ranges (sympatric) [32] Hybridization occurs due to overlapping ranges (sympatric) [16] Parent protection status Hybrid conservation status (protected or managed) Consequences & characteristics No Not protected or managed No consequences documented. natural Hybridization occurs due to overlapping ranges (sympatric) [86] No Not protected or managed Hybrid has better crown structure for nesting birds [86] anthropogenic (unintentional) [147] Hybridization occurs due to overlapping ranges (sympatric) [148] No Not protected or managed Introgression toward Siberian Elm, and hybridization increases invasiveness of Siberian Elm and threatens the survival of Red Elm [147, 148] native Attitude towards hybrid and displaces native Salix species [62] Neutral – does not affect biodiversity [16] Positive – increased nesting in hybrids compared to parent taxa suggests potential use of hybrids in riparian area management [86] Negative – hybrid threatens survival of native species [148] Literature Cited [1] Allendorf, F.W., Leary, R.F., Hitt, N.P., Knudsen, K.L., Lundquist, L.L., Spruell, P. 2004. 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