Unisexual Ambystoma Small-mouthed Salamander dependent population
Scientific Name: Ambystoma laterale - texanum
Taxonomy Group: Amphibians
COSEWIC Range: Ontario
COSEWIC Assessment Date and Status Change: April 2016
COSEWIC Status: Endangered
COSEWIC Status Criteria: B1ab(i,ii,iii,iv)+2ab(i,ii,iii,iv)
COSEWIC Reason for Designation: These unusual unisexual salamanders exist only on one isolated island in Canada (Pelee Island in Lake Erie) and depend on an endangered sperm donor species, Small-mouthed Salamander (Ambystoma texanum), for recruitment. The salamander faces numerous threats that make its continued existence precarious. These include predation and habitat modification by introduced wild turkeys, drainage activities that can cause premature drying of breeding ponds, road mortality during seasonal migrations, urban development, and recreational activities.
COSEWIC History of Status Designation: Designated Endangered in April 2016.
SARA Status: Schedule 1, Endangered
Date of Listing (yyyy-mm-dd): 2021-08-12
Please note that this information is provided for general information purposes only. For the most up to date and accurate list of species listed under the Species at Risk Act, please see the Justice Laws Website.
All-female populations of Ambystoma (i.e., unisexuals) are members of the Mole Salamander family Ambystomatidae. Their morphology is variable and is determined by their nuclear genomes. Unisexuals with two or more Blue-spotted Salamander (A. laterale) chromosome complements are black with various amounts of blue flecking, and have relatively short limbs and a narrower head. Unisexuals with two or more Jefferson Salamander (A. jeffersonianum) chromosome complements are larger, grey to brown with a small amount of blue flecking, and have relatively long limbs and a broader head. Unisexuals with two or more Small-mouthed Salamander (A. texanum) chromosome complements are grey, more slender, and have narrow heads. Unisexual Ambystoma all share a very similar mitochondrial DNA that is distinctly different from any bisexual species. They have a unique genetic system and represent a distinct, monophyletic lineage that arose 3 to 5 million years ago, making them the oldest lineage of unisexual vertebrates known. Eggs normally develop by gynogenesis. This process requires sperm, derived from sympatric bisexual species. The sperm is only used to initiate the development of the eggs and typically is not incorporated in the developing embryo. In rare cases, sperm are incorporated, and when DNA from sperm are incorporated, the ploidy of the embryos increases (i.e., triploid to tetraploid). (Updated 2017/01/24)
Distribution and Population
Unisexual salamanders are found in association with appropriate bisexual species whose males serve as sperm donors. The geographic range of unisexual salamanders in the genus Ambystoma roughly coincides with deciduous and mixed-wood forests in northeastern North America from Nova Scotia and the New England States to Indiana. Their northern limits are in Minnesota, north-central Ontario, and southern Quebec, and they range south to Kentucky. Three designatable units are considered in this report, based on their sperm-donor species. In Canada, unisexual salamanders are found in association with the Blue-spotted Salamander in Nova Scotia, New Brunswick, Quebec, and Ontario; with the Jefferson Salamander in Ontario; and with the Small-mouthed Salamander on Pelee Island in Lake Erie, Ontario. In Canada, unisexual populations of salamanders occur in all known Jefferson Salamander and Small-mouthed Salamander populations, as well as in the majority of Blue-spotted Salamander populations that have been investigated. Unisexual Salamanders can be much more numerous than individuals of sympatric bisexual species that serve as sperm donors. (Updated 2017/01/24)
Unisexual Salamanders have the same habitat requirements as their respective sperm-donating species. They are normally found within deciduous or mixed forests containing, or adjacent to, suitable breeding ponds. Breeding ponds are normally ephemeral, or vernal, pools that dry in late summer. Terrestrial habitat is in moist woodlands, where the salamanders find shelter from predators and desiccation under fallen trees or rocks, as well as in mammal burrows. Adults forage during humid conditions at night on the forest floor within ~1 km of the breeding pond. These salamanders also require terrestrial overwintering sites below the frost line. (Updated 2017/01/24)
In conjunction with individuals of their sperm-donating species, unisexual adults migrate to and from breeding ponds at night very early in spring. Most migration events to and from breeding ponds coincide with rain or very humid conditions. Courtship occurs with sympatric bisexual males and, within a day or two after mating, unisexual salamanders deposit several egg masses on sticks or emergent vegetation at various depths in the breeding pond. Egg deposition may occur under the ice. Duration of egg and larval development is variable and temperature-dependent. Larvae are carnivorous and eat a variety of invertebrates and are also cannibalistic. In Canada, larvae normally transform in July or early August and leave the pond. Juveniles and adults are entirely terrestrial except for the annual breeding period. (Updated 2017/01/24)
Loss of sexual sperm donors is a limiting factor unique to unisexual Ambystoma because they require the presence of diploid males of their sexual hosts for reproduction. Threats include: i) partial or absolute elimination of suitable habitat by development, including loss of breeding ponds, trees and ground cover; ii) barriers (e.g., roads, silt fences) across migratory routes linked to breeding ponds; and iii) premature pond drying during summer. (Updated 2017/01/24)
The Unisexual Ambystoma, Small-mouthed Salamander dependent population, is protected under the federal Species at Risk Act (SARA). More information about SARA, including how it protects individual species, is available in the Species at Risk Act: A Guide.
Provincial and Territorial Protection
PLEASE NOTE: Not all COSEWIC reports are currently available on the SARA Public Registry. Most of the reports not yet available are status reports for species assessed by COSEWIC prior to May 2002. Other COSEWIC reports not yet available may include those species assessed as Extinct, Data Deficient or Not at Risk. In the meantime, they are available on request from the COSEWIC Secretariat.
6 record(s) found.
- COSEWIC Status Reports (1 record(s) found.)
- Response Statements (1 record(s) found.)
- Orders (1 record(s) found.)
- COSEWIC Annual Reports (1 record(s) found.)
- Consultation Documents (1 record(s) found.)
- Related Information (1 record(s) found.)
COSEWIC Status Reports
COSEWIC Assessment and Status Report on the Unisexual Ambystoma, Ambystoma laterale, Small-mouthed Salamander-dependent Population, Jefferson Salamander-dependent Population and the Blue-spotted Salamander-dependent Population, in Canada (2017-01-17)All-female populations of Ambystoma (i.e., unisexuals) are members of the Mole Salamander family Ambystomatidae. Their morphology is variable and is determined by their nuclear genomes. Unisexuals with two or more Blue-spotted Salamander (A. laterale) chromosome complements are black with various amounts of blue flecking, and have relatively short limbs and a narrower head. Unisexuals with two or more Jefferson Salamander (A. jeffersonianum) chromosome complements are larger, grey to brown with a small amount of blue flecking, and have relatively long limbs and a broader head. Unisexuals with two or more Small-mouthed Salamander (A. texanum) chromosome complements are grey, more slender, and have narrow heads.
Order Amending Schedule 1 to the Species at Risk Act (2021-09-01)The objectives of the Order Amending Schedule 1 to the Species at Risk Act (the Order) are to help maintain Canada's biodiversity and support the well-being of Canadian ecosystems by preventing wildlife species from becoming extirpated from Canada or extinct and to contribute to their recovery, as well as to respond to COSEWIC's recommendations.
COSEWIC Annual Reports
COSEWIC Annual Report - 2015-2016 (2016-10-13)Over the past year COSEWIC re-examined the status of 25 wildlife species; of these, the majority (68%) were re-assessed at the same or lower level of risk. Of a total of 45 species assessed, seven were assigned a status of Not at Risk (two re-assessments and five new assessments). To date, and with the submission of this report, COSEWIC’s assessments now include 724 wildlife species in various risk categories, including 320 Endangered, 172 Threatened, 209 Special Concern, and 23 Extirpated (i.e., no longer found in the wild in Canada). In addition, 15 wildlife species have been assessed as Extinct, 54 wildlife species have been designated as Data Deficient, and 177 have been assessed and assigned Not at Risk status.