The neoteny Goldilocks zone: The evolution of neoteny in Ambystoma

Neoteny is a developmental strategy wherein an organism reaches sexual maturity without associated adult characteristics. In salamanders, neoteny takes the form of individuals retaining aquatic larval characteristics such as external gills upon maturation. Mole salamanders (Ambystoma) occupy a wide range of habitats and areas across the North American continent and display examples of non-neotenic, facultatively neotenic, and obligate neotenic species, providing high variation for investigating the factors influencing the evolution of neoteny. Here, we use phylogenetic comparative methods to test existing hypotheses that neoteny is associated with elevational and latitudinal distribution, cave-associated isolation, and hybridisation-related polyploidy. We also test if neoteny influences the diversity of habitats a species can occupy since the restriction to aquatic life should constrain the availability of different niches. We find that neoteny tends to occur in a narrow latitudinal ban..., Maximum elevation data was taken from the IUCN Red List database (IUCN 2021) for all species except the following; A. barbouri (Micheletti and Storfer 2015), A.bishopi, A. mabeei, A. maculatum, A. talpoideum, A. texanum, A. talpoideum, A.texanum (observations from AmphibiaWeb 2021, checked for elevation on www.freemaptools.com/elevation-finder.htm), A. californiense (Lanoo 2005), A. cingulatum, (animaldiversity.org 2021), A. jeffersonianum (Thompson and Gates 1982), and A. opacum (Klemens 1993). Latitudinal data (northern and southern distributional limits) were collected using the species distributions from the IUCN Red List database (IUCN 2021). The number of habitats occupied by each species was estimated by counting the second-level habitat types (for example 1.4 Forest -Temperate) listed in the IUCN Red List (IUCN 2021) according to their habitat classification scheme. Inclusion in the Ambystoma jeffersonianum polyploid complex was based on information from Robertson et al. (2006),..., , # The neoteny Goldilocks zone: The evolution of neoteny in *Ambystoma*

[https://doi.org/10.5061/dryad.37pvmcvt0](https://doi.org/10.5061/dryad.37pvmcvt0)

This data was used for our study of the same name, to test previously proposed theories of the drivers of neoteny across the genus *Ambystoma*. We also tested the effect of frequency of neoteny on the diversity of habitats a species can occupy, as well as the transition rates from non-neotenic, facultatively neotenic, and obligate neotenic states.

Phylogenetic comparative methods used binomial phyloGLMs tested with a tree downloaded from vertlife.org (Jetz and Pyron 2014), to test elevational (stated in meters in the dataset as \"MaxElev\"), latitudinal distribution (northern and southern distribution limits \"NLim\" and \"SLim\", by latitude), cave-associated isolation (\"cave\", as binomial, with 1 representing species known to occupy caves), and hybridisation-related polyploidy's (\"complex\", as binomial, with 1 representing species posse...