The land snail family Polygyridae is native to North America; members of this family occur in a wide range of habitats, from humid, mixed-hardwood forests in the Southeastern US to desert mountain tops in the Southwestern US. Polygyrids are medium to large (~5-32 mm diameter), with reflected lips, and with shells ranging in shape from subglobose to discoidal.

This study proposed to use morphological characteristics and nuclear and mitochondrial gene sequences to form a phylogenetic hypothesis for Praticolella to aid revising the group and assist in the establishment of conservation priorities within this group. The focus of this study is the genus Praticolella which is composed of ~15 nominal taxa. The genus is distributed throughout the Southeastern US, Mexico, and Central America. Praticolella griseola has been introduced to several islands in the Caribbean and is an introduced pest in South Florida.

The common name for the genus is “scrub snails” and this is an apt description of their habitat preferences. They are commonly found in scrub brush under rocks, logs, Yucca, and trash. Most polygyrids are mycophagous with foraging activity being primarily nocturnal, when moisture is most abundant. However in more humid environments they can be found active at any time. Several species in this genus are considered to be of conservation concern with a G-rank of G1 or G2, indicating that they are imperiled.

I have made collecting trips throughout Florida and the Florida Keys, Central and South Texas, and Eastern and Central Mexico with one more trip planned to Southern Mexico. Collections of 31 lots (>200 specimens) of live Praticolella have been made encompassing 13 of the 14 described species of Praticolella. Only one species of Praticolella remains to be collected. I have not been able to obtain specimens of P. lawae, however, I will continue to collect to attempt to find this snail alive to include in this project. Shell-only collections make up an additional 95 lots of Praticolella. Additional specimens and types have been borrowed from the Florida Museum of Natural History, the Academy of Natural Sciences of Philadelphia, and the Smithsonian Museum. Outgroups that will be included in the study are Linisa texasiana, Daedalochila hippocrepis, Lobosculum pustulosa, and various other species within the Polygyridae.

DNA has been successfully extracted for all specimens of Praticolella. Several specimens have been amplified for an approximately 800 bp piece of the ITS-1 nuclear gene, however, these have not yet been sequenced. 18 specimens of Praticolella and 4 outgroups have been sequenced for the mt 16S gene. The amplified portion of this gene resulted in ~500 bp of sequence. Samples were purified and double-stranded DNA provided the template for cycle-sequencing using BigDye (ABI) chemistry followed by analysis on an ABI3100 automated sequencer.

A preliminary look at relationships within the genus indicates that the genus Praticolella is monophyletic(Figure 1); however, to draw any final conclusions a few closely related outgroup taxa (Lobosculum spp.) need to be included. The preliminary data also indicates that L. Hubricht’s hybrid hypotheses for the origin of 3 species in this genus are incorrect. A full analysis with both genes must be finished to say this conclusively, but the initial preliminary phylogenetic hypothesis doesn’t support Hubricht’s hybrid species. H.A. Pilsbry’s division of P. berlandieriana into 5 species based on shell morphology does appear to be valid based on this limited sample. Species (with the exception of P. griseola) identified by Pilsbry’s criteria are monophyletic groups in the analysis.

An exciting result of the analysis is the detection of several distinct lineages within the Mexican species of Praticolella. It has been speculated (Fred Thompson pers. comm.) that there are several distinct species of this genus in Mexico that are currently undescribed, and this is supported by the molecular analysis.

Future Work

A few collections remain to be made. There are several distinctive forms of Praticolella in Southern Mexico that I am trying to collect to include in the analysis. Lab work still to be done on this project is to sequence the remaining specimens of Praticolella for the mt 16S gene, and sequence all the specimens for LSU-1. Also underway is an analysis of shell morphology for all species.

A further project utilizing museum specimens and distributional records is underway. Distributional modeling is being used to examine the environmental factors influencing distributions of species in this genus. Comparison of distribution with phylogenetic relationships of this group allows detailed examination of evolutionary history of the group, can predict collection sites, and assists with conservation efforts by defining necessary habitats.

Fig. 1. A preliminary strict consensus tree of partial 16s mt rRNA sequences of snails from 14 numbered locations. Bar delineates the genus Praticolella.