Search

Unisexual salamanders present a novel evolutionary phenomenon that has led to many speculations with respect to their origin and persistence. These salamanders do not comply with basic evolutionary theory with respect to any of the factors that guide speciation. Indeed, none of the various unisexual salamanders can be considered a distinct species. I outline the history of the unisexual Ambystoma from their discovery by Clanton in 1934 and attempt to show how our current understanding of the unisexuals has been influenced by discovering new populations and advances in technology. [ABSTRACT FROM AUTHOR]

Understanding the environmental drivers of species' dispersal and migration patterns is needed to accurately predict climate change impacts on populations. For pond-breeding amphibians, adult movements associated with the breeding period are well studied but major gaps exist in our knowledge of the drivers of adult and juvenile non-breeding movements. Here, we assess environmental drivers of adult and juvenile Ambystoma maculatum (Shaw, 1802), Ambystoma jeffersonianum (Green, 1827), and their unisexual dependants' (Ambystoma laterale–jeffersonianum (Uzzell, 1964)) summer and fall non-breeding movements using data from pitfall trapping and radio telemetry tracking. We used generalized linear models to assess the influence of precipitation, minimum temperature, day of year, and days since last precipitation on salamander movements. Juvenile summer dispersal movements were related to days since last precipitation in Jefferson Salamander complex individuals and 24 h precipitation in Spotted Salamanders. Adult and juvenile fall movements were driven by minimum temperature, 24 h precipitation, and days since last precipitation, and the effect of these environmental factors varied slightly between species and between Jefferson bisexuals and unisexuals. Our work indicates that changes in both temperature and precipitation will likely impact non-breeding dispersal and migration in these species and, overall, improves our understanding of ecological patterns throughout their entire life cycle. [ABSTRACT FROM AUTHOR]

Polyploid animals have independently evolved from diploids in diverse taxa across the tree of life. We review a few polyploid animal species or biotypes where recently developed molecular and cytogenetic methods have significantly improved our understanding of their genetics, reproduction and evolution. Mitochondrial sequences that target the maternal ancestor of a polyploid show that polyploids may have single (e.g. unisexual salamanders in the genus Ambystoma) or multiple (e.g. parthenogenetic polyploid lizards in the genus Aspidoscelis) origins. Microsatellites are nuclear markers that can be used to analyze genetic recombinations, reproductive modes (e.g. Ambystoma) and recombination events (e.g. polyploid frogs such as Pelophylax esculentus). Hom(e)ologous chromosomes and rare intergenomic exchanges in allopolyploids have been distinguished by applying genome-specific fluorescent probes to chromosome spreads. Polyploids arise, and are maintained, through perturbations of the 'normal' meiotic program that would include pre-meiotic chromosome replication and genomic integrity of homologs. When possible, asexual, unisexual and bisexual polyploid species or biotypes interact with diploid relatives, and genes are passed from diploid to polyploid gene pools, which increase genetic diversity and ultimately evolutionary flexibility in the polyploid. When diploid relatives do not exist, polyploids can interact with another polyploid (e.g. species of African Clawed Frogs in the genus Xenopus). Some polyploid fish (e.g. salmonids) and frogs (Xenopus) represent independent lineages whose ancestors experienced whole genome duplication events. Some tetraploid frogs (P. esculentus) and fish (Squaliusalburnoides) may be in the process of becoming independent species, but diploid and triploid forms of these 'species' continue to genetically interact with the comparatively few tetraploid populations. Genetic and genomic interaction between polyploids and diploids is a complex and dynamic process that likely plays a crucial role for the evolution and persistence of polyploid animals. See also other articles in this themed issue. Copyright © 2013 S. Karger AG, Basel [ABSTRACT FROM AUTHOR]

Presents information on a study on the tetraploid species of sand frog called genus Tomoptema from South Africa. Hibernation process of the frogs; Features of the frogs; Details on the genus Tomopterna; Analysis of calls by these frogs; Description of the tetraploid; Advertisement calls of the male tetraploid; Differences between eggs and tadpoles of the same species.

Examines hybridization between tetraploid and diploid species of treefrogs of the genus Hyla. Meiotic mechanisms in the Hyla versicolor; Absence of Hyla arborea alleles in the triploid male; Factors that relate to the ability of tetraploids to hybridize.

Presents the karyotype of the coelancanth. Forty eight chromosome karyotype of Latimeria chanlumnae; Comparison of the idiogram of A. truei with that of L. chalumnae.

Describes the sexual reproduction of triploid hybrid salamanders, which are unisex vertebrates. Gynogenesis; Importance of temperature in gynogenesis; Temperature in sexually-derived offspring.

Presents a study aimed at determining the maternal ancestry of the unisexual salamander hybrids. Populations in eastern North America of all-female salamanders that incorporate the nuclear genomes of two or three of four sympatric bisexual species; Most ancient known unisexual vertebrate lineage; More.

Habitat protection is a key component of endangered species conservation, but critical habitat designations are often based on limited data or habitat use during only a portion of a species' life cycle. Protected habitat around breeding pools for the endangered Jefferson Salamander (Ambystoma jeffersonianum (Green, 1827)) and their unisexual dependents (Ambystoma laterale – (2) jeffersonianum) is based upon limited movement data from primarily spring and summer seasons. Furthermore, despite their treatment as distinct species under Canada's Species at RiskAct, differences in habitat use have not been directly compared in areas where they co-occur. We used radiotelemetry to track A. jeffersonianum (JJ) and A. laterale – jeffersonianum (LJJ and LJJJ) during fall migrations to overwintering sites. We used these data and summarized available movement data from past studies that tracked movements in other periods of the annual cycle to estimate year-round critical habitat. Ambystoma jeffersonianum travelled significantly longer distances to overwintering locations than unisexuals. Individuals were more likely to overwinter next to a similar genomotype individual than not. Critical habitat encompassing the entire annual cycle of A. jeffersonianum extends up to 400–450 m from breeding ponds indicating existing regulatory habitat protections in Canada do not currently protect sufficient habitat. [ABSTRACT FROM AUTHOR]